Gas-dynamic processes in ships internal circulation. Modern problems of science and education. Measurement of the angle of rotation and frequency of rotation of the camshaft
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1 for the rights of manuscript Mashkis Makhmud A. Mathematical model of gas dynamics and heat exchange processes in intake and exhaust systems of the DVS specialty "Thermal motors" dissertation author's abstract on competition of a scientific degree of Candidate of Technical Sciences St. Petersburg 2005
2 General characteristics of work The relevance of the thesis in the current conditions of the accelerated pace of engine development, as well as the dominant trends in the intensification of the workflow, subject to increasing its economy, more close attention is paid to the reduction in the creation of the creation, finishing and modifying the available types of engines. The main factor that significantly reduces both temporary and material costs, in this task is the use of modern computing machines. However, their use can be effective only if the adequacy of the created mathematical models of real processes determining the functioning of the internal combustion system. Especially acute at this stage of the development of the modern engine building is the problem of the heat-staring of the details of the cylinda group (CPG) and the cylinder heads, inextricably associated with an increase in aggregate power. The processes of the instant local convective heat exchange between the working fluid and walls of gas-air channels (GVK) are still not sufficiently studied and are one of the narrow places in the theory of DVS. In this regard, the creation of reliable, experimentally substantiated calculation methods for the study of local convective heat exchange in GVK, which makes it possible to obtain reliable estimates of the temperature and heat-stressed state of DVS parts, is an urgent problem. Its decision will allow to carry out a reasonable choice of design and technological solutions, to increase scientific technical Level Design, will provide an opportunity to reduce the engine creating cycle and get an economic effect by reducing the cost and costs for experimental engines. The purpose and objectives of the study The main objective of the dissertation work is to solve the complex of theoretical, experimental and methodological tasks, 1
3 related to the creation of new refinery mathematical models and methods for calculating local convective heat exchange in the GVK of the engine. In accordance with the purpose of the work, the following basic tasks were solved, a large extent determined and a methodological sequence of performance of work: 1. Conduct the theoretical analysis of the non-stationary flow flow in GVK and assessing the possibilities of using the theory of the boundary layer in determining the parameters of the local convective heat exchange in engines; 2. Development of an algorithm and numerical implementation on the computer for the problem of the imperious flow of the working fluid in the elements of the intake-release system of the multi-cylinder engine in nonstationary formulation to determine the speeds, temperature and pressure used as boundary conditions for the further solution of the gas-dynamics problem and heat exchange in the cavities of the engine GVK. 3. Creating a new methodology for calculating fields of instantaneous velocities by the working bodies of the GVK in three-dimensional formulation; 4. Development mathematical model Local convective heat exchange in GVK using the foundations of the theory of the boundary layer. 5. Check the adequacy of mathematical models of local heat exchange in GVK by comparing experimental and calculated data. The implementation of this complex task allows you to achieve the main objective of the work - the creation of an engineering method for calculating the local parameters of convective heat exchange in GVK gasoline engine. The relevance of the problem is determined by the fact that the solution of the tasks will allow to carry out a reasonable selection of design and technological solutions at the engine design stage, increase the scientific technical level of design, will reduce the engine creating cycle and to obtain an economic effect by reducing the cost and costs for experimental finiteness of the product. 2.
4 The scientific novelty of the dissertation work is that: 1. For the first time, a mathematical model was used, rationally combining one-dimensional representation of gas-dynamic processes in the intake and exhaust system of the engine with a three-dimensional representation of gas flow in GVK to calculate the parameters of local heat exchange. 2. The methodological basis for the design and finishing of the gasoline engine is developed by upgrading and clarifying methods for calculating local thermal loads and the thermal state of the elements of the cylinder head. 3. New calculated and experimental data on the spatial gas flows in the inlet and exhaust channels of the engine and the three-dimensional temperature distribution in the body of the head of the gasoline engine cylinders are obtained. The accuracy of the results is ensured by the application of approved methods of computational analysis and experimental studies, common systems Equations reflecting fundamental laws conservation of energy, mass, impulse with relevant initial and boundary conditions, modern numerical methods for the implementation of mathematical models, the use of guests and other regulatory acts, corresponding to the graduation of the elements of the measuring complex in an experimental study, as well as satisfactory coordination of the results of modeling and experiment. The practical value of the results obtained is that the algorithm and a program for calculating the closed operating cycle of a gasoline engine with a one-dimensional representation of gas-dynamic processes in the intake and exhaust engine systems, as well as an algorithm and a program for calculating the parameters of heat exchange in GVK of the head of the gasoline engine cylinder head in three-dimensional production, recommended for implementation. The results of theoretical research, confirmed 3
5 experiments, allow you to significantly reduce the cost of designing and finishing the engines. Approbation of the results of work. The main provisions of the dissertation work was reported at scientific seminars of the Department of DVS SPbGPU in G.G., at the XXXI and XXXIII weeks of Science SPbGPU (2002 and 2004). Publications on the dissertation materials published 6 printed works. Structure and scope of work The dissertation work consists of introduction, fifth chapters, conclusion and literature of literature from 129 names. It contains 189 pages, including: 124 pages of the main text, 41 drawings, 14 tables, 6 photographs. The content of the work in the introduction is justified the relevance of the topic of the thesis, the purpose and objectives of the research are determined, the scientific novelty and the practical significance of the work are formulated. Present general characteristics Work. The first chapter contains the analysis of basic work on theoretical and experimental studies of the process of gas dynamics and heat exchange in ICC. Tasks are subject to research. An overview was carried out by constructive forms of graduation and intake channels in the head of the cylinder block and the analysis of methods and results of experimental and calculating and theoretical studies of both stationary and nonstationary gas flows in the gas-air paths of engines internal combustion. Currently, the current approaches to the calculation and modeling of thermo- and gas-dynamic processes, as well as heat transfer intensity in GVK, are considered. It was concluded that most of them have a limited application area and do not give a complete picture of the distribution of heat exchange parameters on the surfaces of the GVK. First of all, this is due to the fact that the solution of the problem of the movement of the working fluid in GVK is produced in a simplified one-dimensional or two-dimensional 4
6 formulation, which is not applicable to the case of a complex form. In addition, it was noted that for calculating convective heat transfer, in most cases, empirical or semi-empirical formulas are used, which also does not allow to obtain the necessary accuracy of the solution. The most fully these questions were previously considered in the works of Bavyin V.V., Isakova Yu.N., Grishina Yu.A., Kruglov M.G., Kostina A.K., Kavtaradze R.Z., Ovsyannikova M.K. , Petrichenko R.M., Petrichenko M.R., Rosenlands GB, Strakhovsky M.V., Thairov, N.D., Shabanova A.Yu., Zaitseva A.B., Mundstukova D.A., Unru P.P., Shehovtsova A.F., Imaging, Haywood J., Benson RS, Garg Rd, Woollatt D., Chapman M., Novak Jm, Stein Ra, Daneshyar H., Horlock JH, WinterBone DE, Kastner LJ , Williams TJ, White BJ, Ferguson CR et al. Analysis of existing problems and methods of research of gas dynamics and heat exchange in GVK made it possible to formulate the main objective of the study as the creation of a methodology for determining the gas flow parameters in GVK in a three-dimensional formulation with the subsequent calculation of the local heat exchange in the Cylinder Cylinder Cylinder heads and the use of this technique to solve practical Problems of reducing the thermal tension of cylinder heads and valves. In connection with the following tasks set out in the work: - create a new methodology for one-dimensional-three-dimensional modeling of heat exchange in the engine output and intake systems, taking into account the complex three-dimensional gas flow in them in order to obtain the source information to specify the boundary conditions of heat exchange when calculating the tasks of heat change of piston cylinder heads DVS; - develop a methodology for setting the boundary conditions at the inlet and outlet of the gas-air channel on the basis of solving a one-dimensional nonstationary model of the working cycle of the multi-cylinder engine; - to check the accuracy of the methodology using test calculations and comparing the results obtained with the experimental data and calculations according to techniques previously known in the engine engineering; five
7 - conduct an inspection and finalization of the technique by performing a calculating experimental study of the thermal state of the engine cylinder heads and carry out the comparison of experimental and calculated data on the temperature distribution in the part. The second chapter is devoted to the development of a mathematical model of a closed working cycle of multi-cylinder internal combustion engine. To implement the one-dimensional calculation scheme of the working process of the multi-cylinder engine, a known characteristic method is selected, which guarantees the high speed of convergence and stability of the calculation process. The gas-air system of the engine is described as an aerodynamically interconnected set of individual elements of cylinders, sections of intake and outlet channels and pipes, collectors, silencers, neutralizers and pipes. The processes of aerodynamics in the intake-release systems are described using the equations of one-dimensional gas dynamics of the imperious compressible gas: the equation of continuity: ρ u ρ u + ρ + u + ρ t x x f df dx \u003d 0; F 2 \u003d π 4 D; (1) Motion equation: U T U + U x 1 P 4 F + + ρ x D 2 U 2 U u \u003d 0; f τ \u003d w; (2) 2 0.5ρU Energy conservation equation: P P + U A T x 2 ρ \u200b\u200bx + 4 F d U 2 (k 1) ρ q U \u003d 0 2 u u; 2 kp a \u003d ρ, (3) where A- the speed of the sound; ρ-density of gas; U-velocity flow along the x axis; t- time; P-pressure; F-coefficient of linear losses; D-diameter with pipeline; k \u003d P ratio of specific heat capacity. C V 6.
8 As boundary conditions are set (based on the basic equations: Inclipatibility, energy conservation and density ratio and sound rate in the non-satropical nature of the flow) Conditions on valve creams in cylinders, as well as conditions on the inlet and output from the engine. The mathematical model of a closed engine operating cycle includes the calculated relationships that describe the processes in the engine cylinders and the parts of the intake and graduation systems. The thermodynamic process in the cylinder is described using the technique developed in SPbGPU. The program provides the ability to define instantaneous gas flow parameters in cylinders and in inlet and output systems for different engine designs. Considered general aspects The use of one-dimensional mathematical models by the method of characteristics (closed working fluid) and some results of the calculation of the change in gas flow parameters in the cylinders and in inlet and outcomes of single and multi-cylinder engines are shown. The results obtained allow you to estimate the degree of perfection of the organization of the engine intake systems, the optimality of the gas distribution phases, the possibility of gas-dynamic configuration of the workflow, the uniformity of individual cylinders, etc. Pressures, temperatures and speed of gas flows at the inlet and output to gas-air cylinder head channels defined using this technique are used in subsequent calculations of heat exchange processes in these cavities as boundary conditions. The third chapter is devoted to the description of the new numerical method, which makes it possible to realize the calculation of the boundary conditions of the thermal state by gas-air channels. The main stages of the calculation are: one-dimensional analysis of the non-stationary gas exchange process in the sections of the intake system and production by the method of characteristics (second chapter), three-dimensional calculation of the filter flow in the inlet and 7
9 graduate channels by finite elements of the MKE, the calculation of local coefficients of the working fluid heat transfer coefficients. The results of the first stage of the program of the closed cycle are used as boundary conditions at the subsequent stages. To describe gas-dynamic processes in the channel, a simplified quasistationary scheme of the slice gas (system of the Euler equations) was selected with a variable form of the region due to the need to take into account the valve movement: R v \u003d 0 RR 1 (V) V \u003d P, the complex geometric configuration of the channels, presence in The volume of the valve, the fragment of the guide sleeve makes it necessary 8 ρ. (4) As boundary conditions, instantaneous, averaged gas-averaged gas velocities at the input and output section were set. These speeds, as well as temperatures and pressure in the channels, were set as a result of calculating the workflow of the multi-cylinder engine. To calculate the gas dynamics problem, the ICE finite element method was chosen, providing high modeling accuracy in combination with acceptable costs for the implementation of the calculation. The calculated ICE algorithm To solve this problem is based on the minimization of the variational functional, obtained by converting the Euler equations using the Bubnov method, Gallerykin: (LLLLLLMM) K Uu φ x + Vu φ y + wu φ z + p ψ x φ) lllllmmk (UV Φ x + vv φ y + wv φ z + p ψ y) φ) lllllmmk (uw φ x + vw φ y + ww φ z + p ψ z) φ) lllllm (u φ x + v φ y + w φ z ) ψ dxdydz \u003d 0. dxdydz \u003d 0, dxdydz \u003d 0, dxdydz \u003d 0, (5)
10 Using the current model of the calculated area. Examples of the calculated models of the intake and exhaust channel of the VAZ-2108 engine are shown in Fig. 1. -B--and Fig.1. The inlet and (b) models (a) of the VAZ engine of the VAZ for calculating the heat exchange in GVK are chosen a bulk two-zone model, the main permissions of which is the separation of the volume on the region of the non-voiceic kernel and the boundary layer. To simplify, the solution of gas dynamics problems is carried out in a quasi-stationary formulation, that is, without taking into account the compressibility of the working fluid. The analysis of the calculation error showed the possibility of such an assumption with the exception of a short-term section of the time immediately after opening the valve gap not exceeding 5 7% of the total gas exchange cycle time. The heat exchange process in GVK with open and closed valves has a different physical nature (forced and free convection, respectively), therefore, they are described in two different techniques. At closed valves, the method is used proposed by MSTU, in which two heat loading processes are taken into account on this section of the working cycle at the expense of the free convection itself and due to the forced convection due to the residual vibrations of the column 9
11 gas in the channel under the influence of pressure variability in the collectors of the multi-cylinder engine. With the open valves, the process of heat exchange is subject to the laws of forced convection initiated by the organized movement of the working fluid on the gas exchange tact. The calculation of heat exchange in this case implies a two-stage solution of the problem Analysis of the local instantaneous structure of the gas flow in the channel and the calculation of the heat exchange intensity through the borderline layer formed on the channel walls. The calculation of the processes of convective heat exchange in GVK was built according to the heat exchange model when the flat wall is streamlined, taking into account either a laminar or turbulent structure of the boundary layer. The criterion dependences of heat exchange were refined based on the results of comparing the calculation and experimental data. The final form of these dependencies is shown below: for a turbulent boundary layer: 0.8 x RE 0 Nu \u003d Pr (6) x for a laminar boundary layer: Nu Nu xx αxx \u003d λ (m, PR) \u003d φ Re TX Kτ, (7) where: α x local heat transfer coefficient; Nu x, Re x Local values \u200b\u200bof Nusselt and Reynolds numbers, respectively; PR number of Prandtl at the moment; m flow gradient characteristic; F (M, PR) function depending on the indicator of the gradient of the flow M and the number 0.15 of the PRANDTL of the PR working fluid; K τ \u003d RE D - correction factor. According to the instantaneous values \u200b\u200bof heat fluxes in the calculated points of the heat-visible surface, averaging was carried out per cycle based on the valve closing period. 10
12 The fourth chapter is devoted to the description of the experimental study of the temperature state of the head of the gasoline engine cylinders. An experimental study was carried out in order to verify and clarify the theoretical technique. The task of the experiment included to obtain the distribution of stationary temperatures in the body of the cylinder head and comparing the results of calculations with the data obtained. Experimental work was carried out at the Department of DVS SPbGPU on the test stand with car Engine VAZ Cylinder Head Preparations are made by the author at the Department of DVS SPbGPU according to the method used in the research laboratory of Zvezda OJSC (St. Petersburg). To measure the stationary temperature distribution in the head, 6 chromel-Copel thermocouples installed along the surfaces of the GVK are used. Measures were carried out both by speed and loading characteristics at various constant rotational frequencies. crankshaft. As a result of the experiment, the thermocouple was obtained during the operation of the engine through speed and load characteristics. Thus, studies have shown, what are the real temperature values \u200b\u200bin the parts of the Cylinder Cylinder Block. More attention is paid to the chapter processing experimental results and evaluation of errors. The fifth chapter provides data from the estimated research, which was carried out in order to verify the mathematical model of heat transfer in GVK by comparing the calculated data with the results of the experiment. In fig. 2 presents the results of modeling the speed field in the intake and exhaust channels of the VAZ-2108 engine using the end element method. The data obtained fully confirm the impossibility of solving this task in any other formulation, except for three-dimensional, 11
13 Since the valve rod has a significant impact on the results in the responsible zone of the cylinder head. In fig. 3-4 shows examples of the results of the calculation of the intensities of the heat exchange in the inlet and exhaust channels. Studies have shown, in particular, the substantial uneven nature of heat transfer as over the channel forming and in the azimuthal coordinate, which is obviously explained by the substantial uneven structure of the gas-entertainment in the channel. The final fields of heat transfer coefficients were used to further calculate the temperature state of the cylinder head. The boundary conditions of heat exchange along the surfaces of the combustion chamber and cooling cavities were set using techniques developed in SPbGPU. The calculation of temperature fields in the cylinder head was carried out for the steady engine operating modes with a crankshaft rotation frequency of 2500 to 5600 rpm along external high-speed and load characteristics. As the Cylinder Cylinder Cylinder Cylinder Circuit Scheme, the head section belonging to the first cylinder is selected. When modeling the thermal state, the finite element method is used in three-dimensional production. A complete picture of thermal fields for the calculated model is shown in Fig. 5. The results of the settlement study are represented as a change in temperature in the body of the cylinder head at the installation places of the thermocouple. Comparison of the calculation data and the experiment showed their satisfactory convergence, the calculation error did not exceed 3 4%. 12
14 outlet channel, φ \u003d 190 inlet channel, φ \u003d 380 φ \u003d 190 φ \u003d 380 Fig.2. The fields of speeds of the working fluid in the graduation and intake channels of the VAZ-2108 engine (n \u003d 5600) α (W / m 2 K) α (W / m 2 K), 0 0.2 0.4 0.6 0.8 1 , 0 S -B- 0 0,0 0.2 0.4 0.6 0.8 1.0 S -A- Pic. 3. Changes in the intensities of heat exchange in external surfaces - -B - intake channel. 13
15 α (W / m 2 K) at the beginning of the intake channel in the middle of the intake channel at the end of the intake channel section-1 α (W / m 2 K) at the beginning of the final channel in the middle of the exhaust channel at the end of the exhaust channel cross section angle turning angle of rotation - Battail channel - outlet channel Fig. 4. Curves change in the intensities of heat exchange depending on the corner of the rotation of the crankshaft. -but- -B- Fig. 5. General view of the finite element model of the cylinder head (A) and the calculated temperature fields (N \u003d 5600 rpm) (b). fourteen
16 Conclusions for work. According to the results of the work carried out, the following main conclusions can be drawn: 1. A new one-dimensional-three-dimensional model of calculating complex spatial processes of the working fluid flow and heat exchange in the channels of the cylinder head of an arbitrary piston engine, characterized greater compared to previously proposed methods and complete versatility Results. 2. New data was obtained about the features of gas dynamics and heat exchange in gas-air channels, confirming the complex spatial uneven nature of the processes, practically excluding the possibility of modeling in one-dimensional and two-dimensional variants of the task. 3. The need to set the boundary conditions for calculating the task of gas-dynamics of intake and outlet channels is confirmed based on the solution of the problem of non-stationary gas flow in pipelines and multi-cylinder channels. It is proved the possibility of considering these processes in one-dimensional formulation. The method of calculating these processes based on the characteristics method is proposed and implemented. 4. The conducted experimental study made it possible to clarify the developed settlement techniques and confirmed their accuracy and accuracy. The comparison of the calculated and measured temperatures in the details showed the maximum error of the results not exceeding 4%. 5. The proposed settlement and experimental technique can be recommended for the introduction of the engine industry in the enterprises in the design of new and adjustment of already existing piston four-stroke. fifteen
17 On the topic of the thesis, the following works were published: 1. Shabanov A.Yu., Mashkur M.A. Development of a model of one-dimensional gas dynamics in intake and exhaust systems of internal combustion engines // dep. in vinity: N1777-B2003 from, 14 s. 2. Shabanov A.Yu., Zaitsev A.B., Mashkir M.A. The finite-element method of calculating the boundary conditions of thermal loading of the head of the cylinder block of the piston engine // dep. in vinity: N1827-B2004 from, 17 s. 3. Shabanov A.Yu., Makhmud Mashkir A. Calculated and experimental study of the temperature state of the engine cylinder head // Engineering: Scientific and technical collection, tagged with a 100th anniversary of the Honored Worker of Science and Technology Russian Federation Professor N.Kh. Dyachenko // P. ed. L. E. Magidovich. St. Petersburg: Publishing House of Polytechnic Un-Ta, from Shabanov A.Yu., Zaitsev A.B., Mashkir M.A. A new method for calculating the boundary conditions of thermal loading of the head of the cylinder block of the piston engine // Engineering, N5 2004, 12 s. 5. Shabanov A.Yu., Makhmud Mashkir A. The use of the method of finite elements in determining the boundary conditions of the thermal state of the cylinder head // XXXIII Science Week of SPbGPU: Materials of the Inter-University Scientific Conference. SPb.: Publishing House of Polytechnic University, 2004, with Mashkir Mahmud A., Shabanov A.Yu. The use of the method of characteristics to the study of gas parameters in gas-air channels of DVS. XXXI SPBGPU Science Week. Part II. Materials of the Interuniversity Scientific Conference. SPB: Publishing House of SPbGPU, 2003, with
18 The work was carried out at the State Educational Institution of Higher Professional Education "St. Petersburg State Polytechnic University", at the Department of Internal Combustion Engines. Scientific leader - Candidate of Technical Sciences, Associate Professor Shabanov Aleksandr Yuryevich Official opponents - Doctor of Technical Sciences, Professor Erofeev Valentin Leonidovich Candidate of Technical Sciences, Associate Professor Kuznetsov Dmitry Borisovich Leading organization - GUP "Tsnidi" Protection will be held in 2005 at the meeting of the dissertation council The state educational institution of higher professional education "St. Petersburg State Polytechnic University" at the address :, St. Petersburg, ul. Polytechnic 29, Main Building, Aud .. The dissertation can be found in the Fundamental Library of GOU "SPbGPU". Abstract of the Dissertation Council Scientific Secretary of the Dissertation Council, Doctor of Technical Sciences, Associate Professor Khrustalev B.S.
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D.V. Grineh (k. T. N.), M.A. Donchenko (k. T. N., Associate Professor), A.N. Ivanov (graduate student), A.L. Perminov (graduate student) Development of the methodology for calculating and designing rotary-blade-type engines with external submarine
Three-dimensional modeling of the workflow in the aviation rotary-piston engine Zelentsov A.A., Minin V.P. Cyam them. P.I. Baranova Dep. 306 "Aviation Piston Engines" 2018 The purpose of the operation rotary-piston
The non-erotic model of transport transport of Trophimov AU, Kutsev VA, Kocharyan, Krasnodar, when describing the process of pumping natural gas in mg, as a rule, a separate hydraulics and heat exchange tasks are considered separately
UDC 6438 Method for calculating the intensity of the turbulence of gas flow at the outlet of the combustion chamber of the gas turbine engine 007 A in Grigoriev, in and Mitrofanov, O and Rudakov, and in Solovyov OJSC Klimov, St. Petersburg
The detonation of the gas mixture in the rough pipes and the slots of V.N. Ohitin S.I. Klimachkov I.A. Potals Moscow State Technical University. AD Bauman Moscow Russia Gasodynamic parameters
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480 rub. | 150 UAH. | $ 7.5 ", Mouseoff, Fgcolor," #FFFFCC ", BGColor," # 393939 ");" Onmouseout \u003d "Return nd ();"\u003e Dissertation period - 480 rub., Delivery 10 minutes , around the clock, seven days a week and holidays
Grigoriev Nikita Igorevich. Gas Dynamics and heat exchange in the exhaust pipeline of the piston engine: the dissertation ... Candidate of Technical Sciences: 01.04.14 / Grigoriev Nikita Igorevich; [Place of protection: Federal State Autonomous Educational Institution of Higher Professional Education "Ural Federal University named after the first President of Russia B. N. Yeltsin "http://lib.urfu.ru/mod/data/view.php?d\u003d51&rid\u003d238321 ].- Ekaterinburg, 2015.- 154 p.
Introduction
Chapter 1. State of the issue and setting the objectives of the study 13
1.1 Types of exhaust systems 13
1.2 Experimental studies of the effectiveness of exhaust systems. 17.
1.3 Settlement studies of the effectiveness of graduation systems 27
1.4 Characteristics of heat exchange processes in the exhaust system of piston internal combustion engine 31
1.5 Conclusions and setting Tasks 37
Chapter 2. Research methodology and description of experimental installation 39
2.1 Choosing a methodology for the study of gas dynamics and heat exchange characteristics of the process of output of the piston engine 39
2.2 Constructive execution of the experimental installation for the study of the process of release in the Piston DVS 46
2.3 Measurement of the angle of rotation and frequency of the distribution shaft 50
2.4 Definition of instant flow 51
2.5 Measurement of instantaneous local heat transfer coefficients 65
2.6 Measurement of overpressure flow in the graduation path 69
2.7 Data Collection System 69
2.8 Conclusions to chapter 2 s
Chapter 3. Gas dynamics and expenditure characteristics of the release process 72
3.1 Gas dynamics and expenditure characteristics of the release process in the piston engine of internal combustion without chance of 72
3.1.1 with a pipeline with a circular cross section 72
3.1.2 For pipeline with square cross section 76
3.1.3 with a pipeline of a triangular cross section 80
3.2 Gas dynamics and consumables for the process of output of the piston internal combustion engine with reducing 84
3.3 Conclusion to Chapter 3 92
Chapter 4. Instant heat transfer in the exhaust channel of the piston engine of internal combustion 94
4.1 Instant local heat transfer process of an internal combustion of an internal combustion engine without supercharow 94
4.1.1 with pipeline with round cross section 94
4.1.2 For pipeline with square cross section 96
4.1.3 with a pipeline with a triangular cross section 98
4.2 Instant heat transfer process of the outlet of the piston engine of internal combustion with reducing 101
4.3 Conclusions to Chapter 4 107
Chapter 5. Stabilization of the flow in the exhaust channel of the piston engine of internal combustion 108
5.1 Changing the flux pulsations in the exhaust channel of the piston engine using a constant and periodic ejection 108
5.1.1 Suppression of flux pulsations in the outlet using a constant ejection 108
5.1.2 Changing the pulsations of flow in the exhaust channel by periodic ejection 112 5.2 Constructive and technological design of the exhaust tract with ejection 117
Conclusion 120.
Bibliography
Estimated studies of the effectiveness of graduation systems
The exhaust system of piston engine is to remove the exhaust gas engine cylinders and supplying them to the turbocharger turbine (in supervising engines) in order to convert the energy left after the workflow mechanical work on the TK tree. The exhaust channels are performed by a shared pipeline, cast from gray or heat-resistant cast iron, or aluminum in the case of cooling, or from separate cast iron nozzles. To protect service personnel from burns exhaust pipeline It can be cooled with water or coated with heat insulating material. The heat-insulated pipelines are more preferable for engines with gas turbine superimposses. Since in this case, the loss of exhaust gas energy is reduced. Since when heated and cooled the length of the exhaust pipeline changes, then special compensators are installed before the turbine. On the large engines The compensators also combine individual sections of exhaust pipelines, which according to technological reasons make composite.
Information about the parameters of the gas before the turbine turbocharger in the dynamics during each working cycle DVS appeared in the 60s. Some results of studies of the dependence of the instantaneous temperature of the exhaust gases from the load for the four-stroke engine on a small area of \u200b\u200bthe crankshaft rotation dated with the same period of time are also known. However, in no way in any sources there are such important characteristics as the local heat transfer intensity and gas flow rate in the exhaust channel. Diesels with a superior can be three types of gas supply organization from the cylinder head to the turbine: a system of permanent gas pressure in front of the turbine, a pulse system and a supercharge system with a pulse converter.
In the system of constant pressure, the gases from all cylinders go into a large exhaust manifold of a large volume, which serves as a receiver and largely smoothes pressure pulsations (Figure 1). During the release of gas from the cylinder in the exhaust pipe, a high amplitude pressure wave is formed. The disadvantage of such a system is a strong decrease in gas performance while flowing from the cylinder through the collector to the turbine.
With such an organization of the release of gases from the cylinder and the supply of them to the nozzle apparatus of the turbine decreases the loss of energy associated with their sudden expansion during the expiration of the cylinder into the pipeline and the two-time conversion of energy: the kinetic energy arising from the cylinder of gases into the potential energy of their pressure in the pipeline, and the last Again in the kinetic energy in the nozzle apparatus in the turbine, as it occurs in the graduation system with constant pressure pressure at the entrance to the turbine. As a result of this, during the pulsed system, the disposable operation of gases in the turbine increases and their pressure decreases during the release, which reduces the cost of power to carry out gas exchange in the cylinder of the piston engine.
It should be noted that with a pulsed superior, the conditions for the conversion of energy in the turbine are significantly deteriorated due to nonstationarity of the flow, which leads to a decrease in its efficiency. In addition, the definition of the calculated parameters of the turbine is hampered due to variables of pressure and temperature of the gas before the turbine and behind it, and the separation supply of gas to its nozzle apparatus. In addition, the design of both the engine itself and the turbocharger turbine is complicated due to the introduction of separate collectors. As a result, a number of firms with mass production Engines with gas turbine superior applies a constant pressure boost system before turbine.
The supervision of the impulse converter is intermediate and combines the benefits of pressure pulsations in the exhaust manifold (reducing the poverty operation and improving the cylinder purge) with a winner from reducing pressure ripples before the turbine, which increases the efficiency of the latter.
Figure 3 - Superior system with pulse converter: 1 - nozzle; 2 - nozzles; 3 - camera; 4 - Diffuser; 5 - pipeline
In this case, the exhaust gases on pipes 1 (Figure 3) are summarized through nozzles 2, into one pipeline, which combines the releases from cylinders, the phases of which are not superimposed by one to another. At a certain point in time, the pressure pulse in one of the pipelines reaches a maximum. In this case, the maximum gas expiration rate from the nozzle connected to this pipeline becomes the maximum, which results in the effect of ejection to the resolution in another pipeline and thereby facilitates the purge of cylinders attached to it. The process of expiration of the nozzles is repeated with a high frequency, therefore, in chamber 3, which performs the role of a mixer and a damper, a more or less uniform stream is formed, the kinetic energy of which in the diffuser 4 (speed reduction) is transformed into a potential due to increase in pressure. From the pipeline 5 gases enter the turbine at almost constant pressure. A more complex structural diagram of the pulse converter consisting of special nozzles at the ends of the exhaust pipes, combined by a common diffuser, is shown in Figure 4.
The flow in the exhaust pipeline is characterized by pronounced nonstationarity caused by the frequency of the process itself, and the nonstationarity of gas parameters at the borders of the exhaust pipeline-cylinder and the turbine. Channel rotation, profile breakdown and periodic change of its geometrical characteristics at the input section of the valve slot serve the cause of the separation of the boundary layer and the formation of extensive stagnant zones, the dimensions of which are changed over time. In stagnation zones, a refundable flow with large-scale pulsating vortices, which interact with the main flow in the pipeline and largely determine the flow characteristics of the channels. The nonstationarity of the stream is manifested in the exhaust channel and under stationary boundary conditions (with a fixed valve) as a result of ripples of congestion zones. The dimensions of non-stationary vortices and the frequency of their ripples can significantly determine only by experimental methods.
The complexity of experimental study of the structure of non-stationary vortex flows forces designers and researchers to use when choosing the optimal geometry of the exhaust channel by comparing the integral consumables and energy characteristics of the flow, usually obtained under stationary conditions on physical models, that is, with static purge. However, the substantiation of the reliability of such studies is not given.
The paper presents the experimental results of studying the stream structure in the exhaust channel of the engine and carried out comparative analysis structures and integral characteristics of streams under stationary and nonstationary conditions.
The test results of a large number of output variants indicate the insufficient effectiveness of the usual approach to profiling based on the perpetrators of the stationary flow in the knees of pipes and short pipes. There are no discrepancy cases of predicted and valid dependencies consumables from channel geometry.
Measurement of the angle of rotation and frequency of rotation of the camshaft
It should be noted that the maximum differences between the values \u200b\u200bof the TPs defined in the center of the channel and near its wall (the variation on the radius of the channel) are observed in control sections close to the input to the channel under study and reach 10.0% of the IPI. Thus, if the forced gas flow pulsations for 1x to 150 mm were with a period of a lot less than the IPI \u003d 115 ms, the current should be characterized as the current high degree Nonstationarity. This suggests that the transitional flow regime in the channels of the energy installation has not yet been completed, and the next indignation has already affected. And on the contrary, if the pulsations of the flow would be much more with a period than TR, the current should be considered a quasistationary (with a low degree of nonstationary). In this case, before the occurrence of the perturbation, the transitional hydrodynamic mode has time to complete, and the course to be aligned. And finally, if the flow rate of flow was close to the value of TR, the current should be characterized as moderately non-stationary with an increasing degree of nonstationary.
As an example of the possible use of the characteristic times proposed to assess the characteristic times, the flow of gas in the exhaust channels of piston engineers is considered. First, refer to Figure 17, at which the dependences of the WX flow rate from the angle of rotation of the crankshaft F (Figure 17, a) and on the time T (Figure 17, b). These dependences were obtained on the physical model of the same-cylinder DVS dimension 8.2 / 7.1. From the figure, it can be seen that the representation of the dependence WX \u003d F (φ) is a little-informative, since it does not accurately reflect the physical essence of the processes occurring in the graduation channel. However, it is precisely in this form that these graphics are taken to submit in the field of engine field. In our opinion, it is more correct to use temporal dependences WX \u003d / (T) to analyze.
We analyze the dependence WX \u003d / (T) for n \u003d 1500 min. "1 (Figure 18). As can be seen, at this crankshaft rotation frequency, the length of the entire release process is 27.1 ms. The transitional hydrodynamic process in the outlet begins after opening the exhaust valve. At the same time, the most dynamic area of \u200b\u200bthe lift can be distinguished (the time interval during which there is a sharp increase in flow rate), the duration of which is 6.3 ms. After that, the growth of the flow rate is replaced by its recess. As shown earlier (Figure 15), for this The configuration of the hydraulic system relaxation time is 115-120 ms, i.e. significantly larger than the duration of the lifting section. Thus, it should be assumed that the beginning of the release (lifting section) occurs with a high degree of nonstationary. 540 Ф, HRAD PKV 7 A)
The gas was supplied from the total network on the pipeline, on which the pressure gauge 1 was installed to control the pressure on the network and the valve 2, to control the flow. The gas flowed into the tank receiver 3 with a volume of 0.04 m3, it contained an alignment grille 4 to quench pressure pulsations. From the tank-receiver 3, the gas pipeline was supplied to the cylinder-blowing chamber 5, in which Honeycomb 6 was installed. Honaycomb was a thin grille, and was intended to clean residual pressure ripples. The cylinder-blowing chamber 5 was attached to the cylinder block 8, while the inner cavity of the cylinder-cell chamber was combined with the inner cavity of the head of the cylinder block.
After opening the exhaust valve 7, the gas from the simulation chamber went through the exhaust channel 9 to the measuring channel 10.
Figure 20 shows in more detail the configuration of the exhaust path of the experimental installation, indicating the locations of the pressure sensors and the thermoemometer probes.
Due limited quantity Information on the dynamics of the release process as the original geometric base was chosen a classic direct outlet channel with a circular cross section: an experimental exhaust pipe was attached to the head of the cylinder block 2, the pipe length was 400 mm, and a diameter of 30 mm. In the pipe, three holes were drilled at distances L \\, lg and b, respectively, 20,140 and 340 mm for the installation of pressure sensors 5 and thermo-chaser sensors 6 (Figure 20).
Figure 20 - configuration of the exhaust channel of the experimental installation and location of the sensor: 1 - cylinder - blowing chamber; 2 - the head of the cylinder block; 3 - exhaust valve; 4 - an experimental graduation tube; 5 - pressure sensors; 6 - thermoemometer sensors for measuring the flow rate; L is the length of the outlet pipe; C_3- Diases to the locations of the thermo-chaser sensors from the exhaust window
The installation measurement system made it possible to determine: the current corner of the rotation and the rotational speed of the crankshaft, the instantaneous flow rate, the instantaneous heat transfer coefficient, excess flow pressure. Methods for defining these parameters are described below. 2.3 Measurement of the corner of rotation and frequency of rotation of the distribution
To determine the speed of rotation and the current angle of rotation of the camshaft, as well as the moment of finding the piston in the upper and lower dead points, a tachometric sensor was applied, the installation scheme, which is shown in Figure 21, since the parameters listed above must be unambiguously determined in the study of dynamic processes in ICC . four
The tachometric sensor consisted of a toothed disk 7, which had only two teeth located opposite each other. The disk 1 was installed with an electric motor 4 so that one of the discs of the disk corresponded to the position of the piston in the upper dead point, and the other, respectively, the bottom dead point and was attached to the shaft using the coupling 3. The motor shaft and the piston engine shaft were connected by the belt transmission.
When passing one of the teeth near the inductive sensor 4, fixed on the tripod 5, the output of the inductive sensor is formed a voltage pulse. Using these pulses, you can determine the current position of the camshaft and, accordingly, determine the position of the piston. In order for the signals corresponding to NMT and NMT, the teeth were performed from each other from each other, the configuration is different from each other, due to which the signals at the outlet of the inductive sensor had different amplitudes. The signal obtained at the outlet from the inductive sensor is shown in Figure 22: the voltage pulse of a smaller amplitude corresponds to the position of the piston in the NTC, and the pulse of a higher amplitude, respectively, position in NMT.
Gas dynamics and consumables process of the output of the piston internal combustion engine with a superposition
In classical literature on the theory of workflow and engineering, the turbocharger is mainly considered as the most effective method of engine forcing, due to an increase in the amount of air entering the engine cylinders.
It should be noted that in literary sources, the influence of the turbocharger on the gas-dynamic and thermophysical characteristics of the gas flow of the exhaust pipeline is extremely rare. Mainly in the literature, the turbine turbine turbine is considered with simplifications, as an element of a gas exchange system, which has hydraulic resistance to the flow of gases at the outlet of the cylinders. However, it is obvious that the turbocharger turbine plays an important role in the formation of the flow of exhaust gases and has a significant impact on the hydrodynamic and thermophysical characteristics of the flow. This section discusses the results of the study of the effect of the turbocharger turbine on the hydrodynamic and thermophysical characteristics of the gas flow in the exhaust pipeline of the piston engine.
Studies were carried out on an experimental setup, which was previously described, in the second chapter, the main change is the installation of a TKR-6 turbocharger with a radial-axial turbine (Figures 47 and 48).
Due to the influence of the pressure of the exhaust gases in the exhaust pipeline to the workflow of the turbine, the patterns of changes in this indicator are widely studied. Compressed
The turbine turbine installation in the exhaust pipeline has a strong effect on the pressure and flow rate in the exhaust pipeline, which is clearly seen from the plugness of the pressure and the flow rate in the exhaust pipe with the turbocharger from the corner of the crankshaft (Figures 49 and 50). Comparing these dependencies with similar dependencies for the exhaust pipeline without a turbocharger under similar conditions, it can be seen that the installation of a turbocharger turbine into the exhaust pipe leads to the emergence of a large number of ripples throughout the entire output of the output caused by the action of the blade elements (nozzle apparatus and impeller) of the turbine. Figure 48 - General type of installation with turbocharger
One more characteristic feature These dependencies is a significant increase in the amplitude of pressure fluctuations and a significant reduction in the amplitude of the speed fluctuation in comparison with the execution of the exhaust system without a turbocharger. For example, at with the rotation frequency of the crankshaft of 1500 minutes, the maximum gas pressure in the pipeline with a turbocharger is 2 times higher, and the speed is 4.5 times lower than in the pipeline without a turbocharger. Increased pressure and Reducing the speed in the graduation pipeline is caused by the resistance created by the turbine. It is worth noting that the maximum pressure value in the turbocharger pipeline is shifted relative to the maximum pressure value in the pipeline without a turbocharger by up to 50 degrees of the rotation of the crankshaft. SO
The dependences of the local (1x \u003d 140 mm) excess pressure of the PC and the flow rate of the WX in the exhaust pipeline of the circular cross-section of the piston engine with a turbocharger from the angle of rotation of the crankshaft p at an overpressure of the release of the P t \u003d 100 kPa for different crankshaft speeds:
It was found that in the exhaust pipeline with a turbocharger, the maximum flow rate values \u200b\u200bare lower than in the pipeline without it. It is worth noting that at the same time the moment of achieving the maximum flow rate value towards an increase in the corner of the crankshaft turn is characteristic of all installation modes. In the case of turbocharger, the rate of speed is most pronounced at low speeds of rotation of the crankshaft, which is also characteristic and in the case without a turbocharger.
Similar features are characteristic and for dependence Px \u003d / (P).
It should be noted that after closing the exhaust valve, the gas speed in the pipeline in all modes is not reduced to zero. Installing the turbocharger turbine in the exhaust pipeline leads to the smoothing of the flow rate pulsations on all modes of operation (especially with the initial overpressure of 100 kPa), both during the output tact and after its end.
It is worth noting that in the pipeline with a turbocharger, the intensity of the attenuation of the fluctuations of the flow pressure after the exhaust valve is closed higher than without a turbocharger
It should be assumed that the changes described above the changes in the gas-dynamic characteristics of the flow when the turbocharger is installed in the exhaust pipeline, the flow of flow in the outlet canal, which inevitably should lead to changes in the thermophysical characteristics of the release process.
In general, the dependence of the pressure change in the pipeline in DVS with the superior is consistent with the previously obtained.
Figure 53 shows dependence graphs mass flow G through the exhaust pipeline from the speed of rotation of the crankshaft under the various values \u200b\u200bof the redundant pressure of the P and the configurations of the exhaust system (with the turbocharger and without it). These graphics were obtained using the technique described in.
From the graphs shown in Figure 53, it can be seen that for all values \u200b\u200bof the initial overpressure, the mass flow rate G of gas in the exhaust pipeline is about the same as if there is a TK and without it.
In some modes of operation of the installation, the difference of the expenditure characteristics slightly exceeds a systematic error, which is about 8-10% to determine the mass flow rate. 0.0145 g. kg / s
For pipeline with square cross section
The exhaust system with ejection functions as follows. The exhaust gases into the exhaust system come from the engine cylinder into the channel in the cylinder head 7, from where they pass to the exhaust manifold 2. In the exhaust manifold 2, an ejection tube 4 is installed in which air is supplied via an electropneumoclap 5. Such an execution allows you to create a discharge area immediately behind the channel Cylinder head.
In order for the ejection tube does not create significant hydraulic resistance in the exhaust manifold, its diameter should not exceed 1/10 diameter of this collector. It is also necessary in order to create a critical mode in the exhaust manifold, and the ejector locking appears. The position of the ejection tube axis relative to the exhaust collector axis (eccentricity) is selected depending on the specific configuration of the exhaust system and the engine operation mode. In this case, the effectiveness criterion is the degree of purification of the cylinder from the exhaust gases.
Search experiments showed that the discharge (static pressure) created in the exhaust manifold 2 using the ejection tube 4 should be at least 5 kPa. Otherwise, insufficient leveling of the pulsating flow will occur. This can cause the formation of feed currents in the channel, which will lead to a decrease in the efficiency of the cylinder purge, and, accordingly, reduce the power of the engine. The electronic motor control unit 6 must organize the operation of the electropneumoclap 5, depending on the rotational speed of the engine crankshaft. To enhance the effect of ejection at the output end of the ejection tube 4, a subsonic nozzle may be installed.
It turned out that the maximum values \u200b\u200bof the flow rate in the outlet canal with constant ejection is significantly higher than without it (up to 35%). In addition, after closing the exhaust valve in the exhaust channel with a constant ejection, the speed of the output flow drops slower compared to the traditional channel, which indicates the continuing cleaning of the channel from the exhaust gases.
Figure 63 shows the dependences of the local volumetric flow rate of VX through the outlet channels of different designs from the rotational speed of the crankshaft p. They indicate that in the entire range of the rotation frequency of the crankshaft at a constant ejection, the volume flow rate through the exhaust system is increasing, which should lead to The best cleaning of cylinders from exhaust gases and an increase in engine power.
Thus, the study showed that the use of a constant ejection in the exhaust system in the exhaust system improves the cylinder gas purification compared to traditional systems by stabilizing the flow in the exhaust system.
The main principal honors this method From the method of quenching flow pulsations in the exhaust channel of the piston engine, with the effect of constant ejection, the air through the ejection tube is supplied to the exhaust channel only during the release tact. This may be feasible by setting the electronic motor control unit, or the use of a special control unit, the diagram of which is shown in Figure 66.
This scheme developed by the author (Figure 64) is applied if it is impossible to ensure the control of the ejection process using the engine control unit. The principle of operation of such a scheme consists in the following, special magnets should be installed on the engine flywheel, special magnets must be installed, the position of which would correspond to the moments of opening and closing the engine outlet valves. Magnets must be installed in different poles relative to the Hall bipolar sensor, which in turn should be in the immediate vicinity of magnets. Passing next to the sensor Magnet, set by respectively the point of opening of the exhaust valves, causes a small electrical pulse, which is enhanced by the signal amplification unit 5, and is fed to the electropneumoclap, the conclusions of which are connected to the outputs 2 and 4 of the control unit, after which it opens and air supply begins . It happens when the second magnet runs next to the sensor 7, after which the electropneumoclap closes.
We turn to experimental data that were obtained in the range of rotation frequencies of the crankshaft P from 600 to 3000 minutes. 1 with different permanent overpressure pins on the release (from 0.5 to 200 kPa). In experiments, compressed air with a temperature of 22-24 with The ejection tube received from the factory highway. Deflection (static pressure) for the ejection tube in the exhaust system was 5 kPa.
Figure 65 shows the graphs of the local pressure dependences Px (y \u003d 140 mm) and the WX flow rate in the exhaust pipeline of the round transverse section of the piston engine with a periodic ejection from the angle of rotation of the crankshaft r under the excess pressure of the № \u003d 100 kPa for various rotation frequencies of the crankshaft .
From these graphs, it can be seen that throughout the entire tact of release there is a oscillation of absolute pressure in the graduation path, the maximum values \u200b\u200bof pressure oscillations reach 15 kPa, and the minimum reaches the discharge of 9 kPa. Then, as in the classic graduation path of the circular cross section, these indicators are respectively 13.5 kPa and 5 kPa. It is worth noting that the maximum pressure value is observed at the speed of the crankshaft of 1500 min. "1, on the other modes of operation of the pressure oscillation engine do not reach such values. Recall. That in the initial pipe of the round cross section, the monotonous increase in the amplitude of pressure fluctuations was observed depending on the increase The rotation frequency of the crankshaft.
From the charts of the local gas flow rate of the gas flow from the corner of the crankshaft rotation, it can be seen that local speeds during the release tact in the channel using the effect of periodic ejection is higher than in the classic channel of the circular cross section on all modes of the engine. This indicates the best cleaning of the graduation channel.
Figure 66, graphs of comparing the dependences of the volumetric flow rate of the gas from the rotational speed of the crankshaft in the round cross section of without ejection and the round cross section with a periodic ejection at various overpressure at the inlet input canal are considered.
UDC 621.436
Effect of aerodynamic resistance of intake and exhaust systems of automotive engines on gas exchange processes
L.V. Carpenters, bp Zhilkin, Yu.M. Brodov, N.I. Grigoriev
The paper presents the results of an experimental study of the influence of the aerodynamic resistance of intake and exhaust systems piston engines on gas exchange processes. The experiments were carried out on the on-line models of single-cylinder engine. Installations and methods for conducting experiments are described. The dependences of the change in the instantaneous speed and pressure of the flow in the gas-air paths of the engine from the corner of the crankshaft rotation are presented. The data was obtained at various coefficients of resistance of intake and exhaust systems and different frequencies of rotation of the crankshaft. Based on the data obtained, conclusions were made of the dynamic features of gas exchange processes in the engine at different conditions. It is shown that the use of the noise muffler smoothes the flow ripple and changes the flow characteristics.
Keywords: piston engine, gas exchange processes, process dynamics, speed pulsation and flow pressure, noise muffler.
Introduction
A number of requirements are made to intake and outcomes of piston engines of internal combustion, among which the main decrease in aerodynamic noise and minimal aerodynamic resistance are the main. Both of these indicators are determined in the interconnection of the design of the filter element, inlet silencers and the release, catalytic neutralizers, the presence of a superior (compressor and / or turbocharger), as well as the configuration of intake and exhaust pipelines and the nature of the flow in them. At the same time, there are practically no data on the influence of additional elements of intake and exhaust systems (filters, silencers, turbocharger) on gas dynamics in them.
This article presents the results of a study of the effect of the aerodynamic resistance of intake and exhaust systems on gas exchange processes in relation to the piston engine of dimension 8.2 / 7.1.
Experimental plants
and data collection system
Studies of the effect of aerodynamic resistance of gas-air systems on gas exchange processes in piston engineers were carried out on the simulation model of the dimension 4.2 / 7.1, driven by rotation asynchronous engineThe frequency of rotation of the crankshaft of which was adjusted in the range n \u003d 600-3000 min1 with an accuracy of ± 0.1%. An experimental installation is described in more detail.
In fig. 1 and 2 show the configurations and geometric sizes of the intake and exhaust path of the experimental installation, as well as the installation location for the measurement of instantaneous
the values \u200b\u200bof the average speed and pressure of the flow of air.
For measurements of instant pressure values \u200b\u200bin the stream (static) in the PC channel, the pressure sensor £ -10 was used by Wika, the speed of which is less than 1 ms. The maximum relative average mean-square pressure measurement error was ± 0.25%.
To determine the instantaneous medium in the section of the air flow channel, the thermoenemometers of the constant temperature of the original design, the sensitive element of which was the nichrome thread with a diameter of 5 μm and a length of 5 mm. The maximum relative average mean-of-mean error of measuring the speed WX was ± 2.9%.
The measurement of the rotation frequency of the crankshaft was carried out using a tachometric meter consisting of a toothed disk fixed on the crankshaft shaft and an inductive sensor. The sensor formed a voltage pulse at a frequency proportional to the rotation speed of the shaft. According to these pulses, the frequency of rotation was recorded, the position of the crankshaft (angle f) was determined and the moment of passing the piston of VMT and NMT.
Signals from all sensors entered an analog-to-digital converter and transmitted to a personal computer for further processing.
Before carrying out experiments, a static and dynamic targeting of the measuring system was carried out in general, which showed the speed necessary to study the dynamics of gas-dynamic processes in the inlet and exhaust systems of piston engines. The total average mean-of-mean error of experiments on the effect of the aerodynamic resistance of gas-air systems of DVS. Gas exchange processes were ± 3.4%.
Fig. 1. Configuration and geometric sizes of the intake path of the experimental installation: 1 - cylinder head; 2-bubbling pipe; 3 - measuring tube; 4 - thermoanemometer sensors for measuring air flow rate; 5 - Pressure Sensors
Fig. 2. Configuration and geometric dimensions of the exhaust path of the experimental installation: 1 - cylinder head; 2 - working plot - graduation pipe; 3 - pressure sensors; 4 - thermoemometer sensors
The effect of additional elements on the gas dynamics of intake and release processes was studied with different system resistance coefficients. Resistance was created using various intake filters and release. So, as one of them, a standard air automobile filter was used with a resistance coefficient of 7.5. A tissue filter with a resistance coefficient 32 was chosen as another filter element. The resistance coefficient was determined experimentally through static purge in laboratory conditions. Studies were also conducted without filters.
Effect of aerodynamic resistance on the inlet process
In fig. 3 and 4 show the dependences of the air flow rate and PC pressure in the inlet can
le from the angle of rotation of the crankshaft f at different of its rotation frequencies and when using various intake filters.
It has been established that in both cases (with a silencer and without) pulsation of pressure and air flow rates are most expressed at high speed of rotation of the crankshaft. At the same time in the intake canal with the silencer of noise maximum speed Air flow, as it should be expected, less than in the channel without it. Most
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Fig. 3. The dependence of the air velocity WX in the intake channel from the angle of rotation of the crankshaft shaft at different frequencies of the rotation of the crankshaft and different filtering elements: a - n \u003d 1500 min-1; B - 3000 min-1. 1 - without a filter; 2 - standard air filter; 3 - fabric filter
Fig. 4. The dependence of the PC pressure in the inlet channel from the angle of rotation of the crankshaft f at different frequencies of rotation of the crankshaft and different filtering elements: a - n \u003d 1500 min-1; B - 3000 min-1. 1 - without a filter; 2 - standard air filter; 3 - fabric filter
it was brightly manifested with high frequencies of rotation of the crankshaft.
After closing the intake valve, the pressure and speed of the air flow in the channel under all conditions do not become equal to zero, and some of their fluctuations are observed (see Fig. 3 and 4), which is also characteristic of the release process (see below). At the same time, the installation of the inlet noise muffler leads to a decrease in pressure pulsations and air flow rates under all conditions both during the intake process and after the intake valve is closed.
Effect of aerodynamic
resistance to the release process
In fig. 5 and 6 shows the dependences of the air flow rate of the WX and the pressure PC in the outlet from the angle of rotation of the crankshaft form at different rotational frequencies and when using various release filters.
The studies were carried out for various frequencies of rotation of the crankshaft (from 600 to 3000 min1) at different overpressure on the release of PI (from 0.5 to 2.0 bar) without a silent noise and if it is presented.
It has been established that in both cases (with the silencer and without) pulsation of the air flow rate, the most brightly manifested at low frequencies of the crankshaft rotation. In this case, the values \u200b\u200bof the maximum air flow rate remain in the exhaust channel with the noise silencer
merilly the same as without it. After closing the exhaust valve, the air flow rate in the channel under all conditions does not become zero, and some speed fluctuations are observed (see Fig. 5), which is characteristic of the inlet process (see above). At the same time, the installation of the noise muffler on the release leads to a significant increase in the pulsations of the air flow rate under all conditions (especially at ry \u003d 2.0 bar) both during the release process and after the exhaust valve is closed.
It should be noted the opposite effect of aerodynamic resistance on the characteristics of the inlet process in the engine, where air filter Pulsation effects in the intake process and after closing the inlet valve were present, but they were clearly faster than without it. In this case, the presence of a filter in the inlet system led to a decrease in the maximum air flow rate and weakening the dynamics of the process, which is consistent well with previously obtained results in the work.
An increase in the aerodynamic resistance of the exhaust system leads to a certain increase in the maximum pressures in the process of release, as well as the displacement of peaks for NMT. In this case, it can be noted that the installation of the silencer of the noise of the output leads to a decrease in the pulsations of the pressure of the air flow under all conditions both during the production process and after the exhaust valve is closed.
hY. m / s 118 100 46 16
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Opening of ipical |<лапана ^ 1 1 А ікТКГ- ~/М" ^ 1
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540 (P, Grab, P.K.Y. 720 NMT NMT
Fig. 5. The dependence of the air velocity WX in the outlet from the angle of rotation of the crankshaft shaft at different frequencies of the rotation of the crankshaft and different filtering elements: a - n \u003d 1500 min-1; B - 3000 min-1. 1 - without a filter; 2 - standard air filter; 3 - fabric filter
Px. 5pr 0,150
1 1 1 1 1 1 1 1 1 II 1 1 1 II 1 1 L "A 11 1 1 / \\ 1. ', and II 1 1
Opening | Yypzskskaya 1 Іклапана Л7 1 h І _ / 7 / ", g s 1 \\ h Closing of the Bittseast G / CGTї Alan -
c- "1 1 1 1 1 І 1 l l _Л / І І h / 1 1
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Fig. 6. The dependence of the pressure PC in the outlet from the angle of rotation of the crankshaft f at different frequencies of rotation of the crankshaft and different filtering elements: a - n \u003d 1500 min-1; B - 3000 min-1. 1 - without a filter; 2 - standard air filter; 3 - fabric filter
Based on the processing of dependency changes in the flow rate for separate tact, a relative change in the volume flow of air q was calculated through the exhaust channel when the muffler is placed. It has been established that with low overpressure on the release (0.1 MPa), the consumption q in the exhaust system with a silencer is less than in the system without it. At the same time, if at the frequency of rotation of the crankshaft 600 min-1, this difference was approximately 1.5% (which lies within the error), then with n \u003d 3000 min4 this difference reached 23%. It is shown that for high overpressure of 0.2 MPa, the opposite tendency was observed. The volume flow of air through the exhaust channel with the silencer was greater than in the system without it. At the same time, at low frequencies of rotation of the crankshaft, this exceeded was 20%, and with n \u003d 3000 min1 - 5%. According to the authors, such an effect can be explained by some smoothing of the pulsations of the air flow rate in the exhaust system in the presence of a silent noise.
Conclusion
The conducted study showed that the inlet engine of internal combustion is significantly influenced by the aerodynamic resistance of the intake path:
The increase in the resistance of the filter element smoothes the dynamics of the filling process, but at the same time reduces air flow rate, which corresponds to the filling coefficient;
The effect of the filter is enhanced with the increasing rotation frequency of the crankshaft;
The threshold value of the filter resistance coefficient (approximately 50-55), after which its value does not affect the flow rate.
It has been shown that the aerodynamic resistance of the exhaust system also significantly affects the gas-dynamic and consumables of the release process:
Increasing the hydraulic resistance of the exhaust system in the piston DVS leads to an increase in the pulsations of the air flow rate in the exhaust channel;
With low overpressure on the release in the system with a silent noise, there is a decrease in volumetric flow through the exhaust channel, while at high ry - on the contrary, it increases compared to the exhaust system without a silencer.
Thus, the results obtained can be used in engineering practice in order to optimally choose the characteristics of the inlet and outbuilding silencers, which can provide
the influence on the filling of the cylinder of the fresh charge (filling coefficient) and the quality of the cleaning of the engine cylinder from the exhaust gases (the residual gas coefficient) on certain high-speed modes of the work of the piston engine.
Literature
1. Draganov, B.H. Construction of intake and exhaust channels of internal combustion engines / B.Kh. Draganov, MG Kruglov, V. S. Obukhov. - Kiev: Visit School. Head ed, 1987. -175 p.
2. Internal combustion engines. In 3 kN. Kn. 1: Theory of workflows: studies. / V.N. Lou-Kanin, K.A. Morozov, A.S. Khachyan et al.; Ed. V.N. Lukanina. - M.: Higher. Shk., 1995. - 368 p.
3. Champraozs, B.A. Internal combustion engines: theory, modeling and calculation of processes: studies. In the course "Theory of workflows and modeling of processes in internal combustion engines" / B.A. Chamolaoz, M.F. Faraplatov, V.V. Clementev; Ed. Castle Deat. Science of the Russian Federation B.A. Champrazov. - Chelyabinsk: SUURSU, 2010. -382 p.
4. Modern approaches to the creation of diesel engines for passenger cars and small-calm
zovikov /a. Blinov, P.A. Golubev, Yu.E. Dragan et al.; Ed. V. S. Peponova and A. M. Mineyev. - M.: NIC "Engineer", 2000. - 332 p.
5. Experimental study of gas-dynamic processes in the inlet system of piston engine / b.p. Zhokkin, L.V. Carpenters, S.A. Korzh, I.D. Larionov // Engineering. - 2009. -№ 1. - P. 24-27.
6. On the change in gas dynamics of the process of release in piston engine in the installation of the muffler / L.V. Carpenters, bp Zhokkin, A.V. Cross, D.L. Padalak // Bulletin of the Academy of Military Sciences. -2011. - № 2. - P. 267-270.
7. Pat. 81338 RU, MPK G01 P5 / 12. Thermal mechanical temperature of constant temperature / S.N. Pochov, L.V. Carpenters, bp Vilkin. - No. 2008135775/22; Stage. 09/03/2008; publ. 03/10/2009, Bul. № 7.
1This article discusses the assessment of the effect of the resonator on the filling of the engine. In the example of the example, a resonator was proposed - by volume equal to the engine cylinder. The geometry of the intake tract together with the resonator was imported into the FlowVision program. Mathematical modification was carried out taking into account all the properties of the moving gas. To estimate the flow rate through the inlet system, estimates of the flow rate in the system and the relative air pressure in the valve slit, computer simulation was carried out, which showed the effectiveness of the use of additional capacity. An assessment of the flow rate through the valve gap, the speed of flow, flow, pressure and flow density for the standard, upgraded and intake system with the Rexiver was evaluated. At the same time, the mass of the incoming air increases, the flow rate of the flow is reduced and the density of air entering the cylinder increases, which is favorably reflected on the output TV-televons.
inlet tract
resonator
filling a cylinder
math modeling
upgraded canal.
1. Jolobov L. A., Dydykin A. M. Mathematical modeling of the processes of gas exchange DVS: monograph. N.N.: NGSHA, 2007.
2. Dydyskin A. M., Zholobov L. A. Gasodynamic studies of the DVS methods of numerical modeling // Tractors and agricultural machines. 2008. № 4. P. 29-31.
3. Pritr D. M., Turkish V. A. Aeromechanics. M.: Oborongiz, 1960.
4. Khaylov M. A. Calculated pressure fluctuation equation in the suction pipe of the internal combustion engine // Tr. Cyam. 1984. No. 152. P.64.
5. Sonkin V. I. Study of air flow through the valve gap // Tr. US. 1974. Issue 149. P.21-38.
6. Samsky A. A., Popov Yu. P. Difference methods for solving the problems of gas dynamics. M.: Science, 1980. P.352.
7. Rudoy B. P. Applied nonstationary gas dynamics: Tutorial. Ufa: Ufa Aviation Institute, 1988. P.184.
8. Malivanov M.V., Khmelev R. N. On the development of mathematical and software for the calculation of gas-dynamic processes in the DVS: Materials of the IX International Scientific and Practical Conference. Vladimir, 2003. P. 213-216.
The magnitude of the torque of the engine is proportional to the mass of air, attributed to the frequency of rotation. Increasing the filling of the cylinder of gasoline engine, by upgrading the intake path, will lead to an increase in the pressure of the end of the intake, improved mixing formation, an increase in the technical and economic indicators of the engine operation and a decrease in the toxicity of exhaust gases.
The basic requirements for the inlet path are to ensure minimal resistance to the inlet and the uniform distribution of the combustible mixture through the engine cylinders.
Ensuring the minimum resistance to the inlet can be achieved by eliminating the roughness of the inner walls of pipelines, as well as sharp changes in the flow direction and eliminate sudden narrowings and extensions of the tract.
A significant effect on the filling of the cylinder provides various types of boost. The simplest type of superior is to use the dynamics of the incoming air. A large volume of the receiver partially creates resonant effects in a specific rotational speed range, which lead to improved filling. However, they have, as a result, dynamic disadvantages, for example, deviations in the composition of the mixture with a rapid change in the load. Almost the ideal torque flow ensures that the inlet tube is switching, in which, for example, depending on the engine load, the rotational speed and position of the throttle are possible variations:
The length of the pulsation pipe;
Switch between pulsation pipes of different lengths or diameter;
- selective shutdown of a separate pipe of one cylinder in the presence of a large amount of them;
- Switching the volume of the receiver.
In the resonant superior of the cylinder group with the same flagel interval attach short pipes to resonant receiver, which are connected through the resonant pipes with the atmosphere or with the collection receiver acting as a gölmgolts resonator. It is a spherical vessel with an open neck. The air in the neck is the oscillating mass, and the volume of air in the vessel plays the role of an elastic element. Of course, such separation is true only approximately, since some of the air in the cavity has inertial resistance. However, with a sufficiently large value of the area of \u200b\u200bthe opening to the area of \u200b\u200bthe cross section of the cavity, the accuracy of such an approximation is quite satisfactory. The main part of the kinetic oscillation energy is concentrated in the neck of the resonator, where the oscillatory velocity of air particles has the greatest value.
The intake resonator is established between the throttle and cylinder. It begins to act when the throttle is covered enough so that its hydraulic resistance becomes comparable to the resistance of the resonator channel. When the piston moves down, the combustible mixture enters the engine cylinder not only from under the throttle, but also from the tank. With a decrease in the vacuum, the resonator begins to suck the combustible mixture. This will follow the same part, and quite large, reverse ejection.
The article analyzes the flow movement in the intake channel of 4-stroke gasoline engine at the rated crankshaft rotation frequency on the example of the VAZ-2108 engine at the rotational speed of the crankshaft N \u003d 5600min-1.
This research task was solved by the mathematical way using the software package for modeling gas-hydraulic processes. Simulation was carried out using the FlowVision software package. For this purpose, geometry was obtained and imported (under the geometry is understood in the internal volumes of the engine - intake and exhaust pipes, an atrigance of the cylinder) using various standard file formats. This allows SAPR SOLIDWORKS to create a settlement area.
Under the calculation area it is understood as the volume in which the equations of the mathematical model and the border of the volume on which the boundary conditions are determined, then maintain the obtained geometry in the format supported by the FlowVision and use it when creating a new calculated option.
This task used ASCII, Binary format, in the STL extension, type stereolithographyFormat with an angular tolerance of 4.0 degrees and a deviation of 0.025 meters to improve the accuracy of the resulting modeling results.
After receiving the three-dimensional model of the settlement area, a mathematical model is set (a set of laws of changes in the physical parameters of gas for this problem).
In this case, a substantially subsonic gas flow is made at small Reynolds numbers, which is described by the system of turbulent flow of fully compressible gas using the standard K-E of the turbulence model. This mathematical model is described by a system consisting of seven equations: two Navier - Stokes equations, the equations of continuity, energy, the state of the ideal gas, mass transfer and the equation for the kinetic energy of turbulent ripples.
(2)
Energy equation (complete enthalpy)
The equation of the state of the ideal gas:
Turbulent components are associated with the remaining variables through the turbulent viscosity value, which is calculated in accordance with the standard K-ε model of turbulence.
Equations for k and ε
turbulent viscosity:
constants, parameters and sources:
(9)
(10)
σk \u003d 1; σε \u003d 1.3; Cμ \u003d 0.09; Cε1 \u003d 1.44; Cε2 \u003d 1.92
The working substance in the inlet process is air, in this case, considered as the perfect gas. The initial values \u200b\u200bof the parameters are set for the entire settlement area: temperature, concentration, pressure and speed. For pressure and temperature, the initial parameters are equal to reference. The speed inside the calculated region in directions x, y, z is zero. Variable temperature and pressure in FlowVision are represented by relative values, the absolute values \u200b\u200bof which are calculated by the formula:
fa \u003d F + Fref, (11)
where Fa is the absolute value of the variable, F is the calculated relative value of the variable, Fref - the reference value.
Boundary conditions are specified for each of the calculated surfaces. Under the boundary conditions it is necessary to understand the combination of equations and laws characteristic of the surfaces of the calculated geometry. Boundary conditions are necessary to determine the interaction of the settlement area and the mathematical model. On the page for each surface indicates a specific type of boundary condition. The type of the boundary condition is installed on the input channel input windows - free entry. The remaining elements - the wall-bound, which does not let and not transmitting the calculated parameters of the current area. In addition to all of the above boundary conditions, it is necessary to take into account the boundary conditions on the moving elements included in the selected mathematical model.
Movable parts include inlet and exhaust valve, piston. At the boundaries of movable elements, we determine the type of boundary condition of the wall.
For each of the movable bodies, the law of movement is set. Changing the piston rate is determined by the formula. To determine the laws of the valve motion, the valve lift curves were removed in 0.50 with an accuracy of 0.001 mm. Then the speed and acceleration of the valve movement were calculated. The data obtained are converted to dynamic libraries (time - speed).
The next stage in the simulation process is the generation of the computational grid. FlowVision uses a locally adaptive computational net. Initially, an initial computational grid is created, and then the criteria for grinding grid are specified, according to which FlowVision breaks the cells of the initial grid to the desired degree. Adaptation is made in both the volume of the channels of the channels and the cylinder walls. In places with a possible maximum speed, adaptation with additional grinding of the computational grid are created. By volume, the grinding was carried out up to 2 levels in the combustion chamber and up to 5 levels in valve slots, along the walls of the cylinder, adaptation was made up to 1 level. This is necessary to increase the time integration step with an implicit method of calculation. This is due to the fact that the time step is defined as the ratio of the cell size to the maximum speed in it.
Before starting to calculate the created option, you must specify the parameters of numerical modeling. At the same time, the time to continue the calculation is equal to one full cycle of operation of the engine, 7200 PK., The number of iterations and the frequency of saving these calculation options. For subsequent processing, certain stages of calculation are preserved. Set the time and options for the calculation process. This task requires a time step setting - a method of choice: an implicit scheme with a maximum step 5E-004C, explicit number of CFL - 1. This means that the time step determines the program itself, depending on the convergence of the pressure equations itself.
The postprocessor is configured and the parameters of the visualization of the results are interested in. Simulation allows you to obtain the required layers of visualization after the completion of the main calculation, based on the calculation stages remained with a certain frequency. In addition, the postprocessor allows you to transmit the resulting numeric values \u200b\u200bof the parameters of the process under study in the form of an information file into external electronic table editors and to obtain the time dependence of such parameters as speed, consumption, pressure, etc.
Figure 1 shows the installation of the receiver on the inlet channel of the DVS. The volume of the receiver is equal to the volume of one engine cylinder. The receiver is set as close as possible to the inlet channel.
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Fig. 1. Upgraded with the receiver Settlement area in CadsolidWorks |
The own frequency of the Helmholtz resonator is:
(12)
where F is the frequency, Hz; C0 - sound speed in the air (340 m / s); S - hole cross section, m2; L is the length of the pipe, m; V is the volume of the resonator, M3.
For our example, we have the following values:
d \u003d 0.032 m, s \u003d 0.00080384 m2, v \u003d 0.000422267 m3, l \u003d 0.04 m.
After calculating F \u003d 374 Hz, which corresponds to the rotational speed of the crankshaft N \u003d 5600min-1.
After setting the calculated option and, after setting the parameters of numerical simulation, the following data were obtained: flow rate, speed, density, pressure, gas flow temperature in the inlet channel of the intensity of the Crankshaft rotation.
From the graph presented (Fig. 2), in terms of flow flow in the valve slit, it is clear that the upgraded channel with the receiver has the maximum consumables. Consumption value is higher than 200 g / s. The increase is observed for 60 G.P.K.V.
Since the opening of the inlet valve (348 G.K.V.) The flow rate (Fig. 3) begins to grow from 0 to 170m / s (at the modernized intake channel 210 m / s, with the -190m / s receivers) in the interval Up to 440-450 G.K.V. In the channel with the receiver, the speed value is higher than in a standard approximately 20 m / s starting from 430-440. P.K.V. The numeric value of the channel in the channel with the receiver is significantly more even than the upgraded inlet channel, during the opening of the inlet valve. Next, there is a significant reduction in the flow rate, up to the closure of the inlet valve.
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Fig. 2. Consumption of the gas flow in the valve slot for the channels of standard, upgraded and with the receiver at n \u003d 5600 min-1: 1 - standard, 2 - upgraded, 3 - upgraded with the receiver |
Fig. 3. The flow rate of the flow in the valve slot for the channels of standard, upgraded and with the receiver at n \u003d 5600 min-1: 1 - standard, 2 - upgraded, 3 - upgraded with the receiver |
Of the relative pressure graphs (Fig. 4) (atmospheric pressure, P \u003d 101000 PA is received for zero), it follows that the pressure value in the upgraded channel is higher than in the standard, by 20 kPa at 460-480 GP.K.V. (associated with a large flow rate value). Starting from 520 G.K.V. The pressure value is aligned, which cannot be said about the channel with the receiver. The pressure value is higher than in the standard one, by 25 kPa, starting from 420-440 GP.K.V. Up to the closure of the inlet valve.
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Fig. 4. Flow pressure in standard, upgraded and channel with a receiver at n \u003d 5600 min-1 (1 - standard channel, 2 - upgraded channel, 3 - upgraded channel with receiver) |
Fig. 5. Flow density in standard, upgraded and channel with a receiver at n \u003d 5600 min-1 (1 - standard channel, 2 - upgraded channel, 3 - upgraded channel with receiver) |
The flow density in the area of \u200b\u200bthe valve gap is shown in Fig. five.
In the upgraded channel with the receiver, the density value is below 0.2 kg / m3 starting from 440 G.K.V. Compared with a standard channel. This is associated with high pressure and gas flow rates.
From the analysis of graphs, you can draw the following conclusion: the channel of the improved form provides better filling of the cylinder with a fresh charge due to a decrease in the hydraulic resistance of the inlet channel. With the increase in the piston velocity at the time of opening the inlet valve, the channel form does not significantly affect the speed, density and pressure inside the intake channel, it is explained by the fact that during this period the inlet process indicators are mainly dependent on the speed of the piston and the valve slot area ( Only the shape of the intake channel changed in this calculation), but everything changes dramatically at the time of slowing down the movement of the piston. The charge in the standard channel is less inert and more stronger "stretch" along the length of the channel, which in the aggregate gives less filling of the cylinder at the time of reducing the speed of the piston movement. Up to the closure of the valve, the process flows under the denominator of the flow rate already obtained (the piston gives the initial flow rate of the cached volume, with a decrease in the velocity of the piston, the inertia component of the gas flow has a significant role on the filling. This is confirmed by higher speed indicators, pressure.
In the inlet canal with the receiver, due to additional charge and resonant phenomena, in the Cylinder of DVS there is a significantly large mass of the gas mixture, which provides higher technical indicators of the DVS operation. The growth increase in the end of the inlet will have a significant impact on the increase in the technical and economic and environmental performance of the DVS work.
Reviewers:
Gots Alexander Nikolaevich, Doctor of Technical University, Professor of the Department of Heat Engines and Energy Installations of the Vladimir State University of the Ministry of Education and Science, Vladimir.
Kulchitsky Aleksey Ramovich, D.N., Professor, Deputy Chief Designer LLC VMTZ, Vladimir.
Bibliographic reference
Jolobov L. A., Suvorov E. A., Vasilyev I. S. Effect of an additional capacity in the inlet system for filling of DVS // Modern problems of science and education. - 2013. - № 1;URL: http://science-education.ru/ru/Article/View?id\u003d8270 (date of handling: 25.11.2019). We bring to your attention the magazines publishing in the publishing house "Academy of Natural Science"
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Federal Agency for Education
GOU VPO "Ural State Technical University - UPI named after the first president of Russia B.N. Yeltsin "
For manuscript rights
Thesis
for the degree of candidate of technical sciences
Gas dynamics and local heat transfer in the intake system of piston engine
Carpenters Leonid Valerevich
Scientific adviser:
doctor Physico-Mathematical Audience,
professor Zhilkin B.P.
Ekaterinburg 2009.
piston Engine Gas Dynamics Intake System
The thesis consists of administration, five chapters, conclusion, a list of references, including 112 names. It is set out on 159 pages of computer dialing in the MS Word program and is equipped with text 87 drawings and 1 table.
Keywords: gas dynamics, piston engine, inlet system, transverse profiling, consumables, local heat transfer, instantaneous local heat transfer coefficient.
The object of the study was the non-stationary air flow in the inlet system of the piston engine of internal combustion.
The goal of the work is to establish the patterns of changes in the gas-dynamic and thermal characteristics of the inlet process in the piston internal combustion engine from geometric and regime factors.
It is shown that by placing the profiled inserts, it is possible to compare with a traditional channel of the constant round, to acquire a number of advantages: an increase in the volume flow of air entering the cylinder; The increase in the steepness of the dependence V on the number of rotation of the crankshaft N in the operating range of the rotation frequency at the "triangular" insert or linearization of the expenditure characteristic in the entire range of rotation numbers of the shaft, as well as suppressing high-frequency air flow pulsations in the inlet channel.
Significant differences in the patterns of changing the coefficients of heat transfer coefficients from the velocity W in the stationary and the pulsating flow of air in the inlet system of the DVS are established. The approximation of the experimental data was obtained equations for calculating the local heat transfer coefficient in the inlet tract of the FEA, both for stationary flow and for a dynamic pulsating flow.
Introduction
1. State of the problem and setting the objectives of the study
2. Description of the experimental installation and measurement methods
2.2 Measurement of the rotational speed and corner of the crankshaft rotation
2.3 Measurement of the instantaneous consumption of suction air
2.4 System for measuring instantaneous heat transfer coefficients
2.5 Data Collection System
3. Gas dynamics and consumables input process in the internal combustion engine at various intake system configurations
3.1 Gas dynamics of the intake process without taking into account the effect of the filter element
3.2 Influence of the filter element on the gas dynamics of the intake process in various intake system configurations
3.3 Consumables and spectral analysis of the inlet process with various intake system configurations with different filter elements
4. The heat transfer in the intake channel of the piston engine of internal combustion
4.1 Calibration of the measuring system to determine the local heat transfer coefficient
4.2 Local heat transfer coefficient in the inlet channel of the internal combustion engine at inpatient mode
4.3 Instant local heat transfer coefficient in the inlet channel of the internal combustion engine
4.4 Influence of the configuration of the inlet system of the internal combustion engine on the instantaneous local heat transfer coefficient
5. Questions of practical application of work results
5.1 Constructive and technological design
5.2 Energy and resource saving
Conclusion
Bibliography
List of basic designations and abbreviations
All symbols are explained when they are first used in the text. The following is only a list of only the most consumable designations:
d -Diameter of pipes, mm;
d e is an equivalent (hydraulic) diameter, mm;
F - surface area, m 2;
i - current strength, and;
G - mass flow of air, kg / s;
L - Length, m;
l is a characteristic linear size, m;
n is the rotational speed of the crankshaft, min -1;
p - atmospheric pressure, PA;
R - resistance, Ohm;
T - absolute temperature, to;
t - the temperature on the Celsius scale, O C;
U - voltage, in;
V - air flow rate, m 3 / s;
w - air flow rate, m / s;
An excess air coefficient;
g - angle, hail;
The angle of rotation of the crankshaft, hail., P.K.V.;
Thermal conductivity coefficient, W / (M K);
Kinematic viscosity coefficient, m 2 / s;
Density, kg / m 3;
Time, s;
Resistance coefficient;
Basic cuts:
p.K.V. - rotation of the crankshaft;
DVS - internal combustion engine;
NMT - upper dead point;
NMT - Lower Dead Point
ADC - analog-to-digital converter;
BPF - Fast Fourier transformation.
Numbers:
Re \u003d WD / - Rangeld's number;
Nu \u003d D / - number of nusselt.
Introduction
The main task in the development and improvement of the piston internal combustion engines is to improve the filling of the cylinder with a fresh charge (or in other words, an increase in the filling coefficient of the engine). Currently, the development of the DVS has reached such a level that the improvement of any technical and economic indicator at least on the tenth share of the percentage with minimal material and temporary costs is a real achievement for researchers or engineers. Therefore, to achieve the goal, the researchers offer and use a variety of methods among the most common can be distinguished by the following: dynamic (inertial) reducing, turbocharging or air blowers, inlet channel of variable length, adjustment of the mechanism and phases of gas distribution, optimization of the intake system configuration. The use of these methods allows to improve the filling of the cylinder with a fresh charge, which in turn increases the engine power and its technical and economic indicators.
However, the use of most of the methods under consideration require significant material investments and a significant modernization of the design of the inlet system and the engine as a whole. Therefore, one of the most common, but not the simplest, to date, the methods of increasing the filling factor is to optimize the configuration of the engine inlet path. In this case, the study and improvement of the inlet channel of the engine is most often carried out by the method of mathematical modeling or static purges of the intake system. However, these methods cannot give correct results at the modern level of engine development, since, as is known, the real process in the gas-air paths of the engines is a three-dimensional gas inkjet expiration through the valve slot into a partially filled space of the variable volume cylinder. An analysis of the literature showed that the information on the intake process in real dynamic mode is practically absent.
Thus, reliable and correct gas-dynamic and heat exchange data for the intake process can be obtained exclusively in studies on dynamic MODELS OF DVS or real engines. Only such experienced data can provide the necessary information to improve the engine at the present level.
The aim of the work is to establish the patterns of changing the gas-dynamic and thermal characteristics of the process of filling the cylinder with a fresh charge of piston internal combustion engine from geometric and regime factors.
The scientific novelty of the main provisions of the work is that the author for the first time:
The amplitude-frequency characteristics of the pulsation effects arising in the stream in the intake manifold (pipe) of the piston engine;
A method for increasing air flow (on average by 24%) entering the cylinder using profiled inserts in the intake manifold, which will lead to an increase in engine power;
The patterns of changes in the instantaneous local heat transfer coefficient in the piston engine inlet tube are established;
It is shown that the use of profiled inserts reduces the heating of fresh charge at the intake by an average of 30%, which will improve the filling of the cylinder;
Generalized in the form of empirical equations The obtained experimental data on the local heat transfer of the pulsating flow of air in the intake manifold.
The accuracy of the results is based on the reliability of experimental data obtained by the combination of independent research methodologies and confirmed by the reproducibility of experimental results, their good agreement at the level of test experiments with these authors, as well as the use of a complex of modern research methods, selection of measuring equipment, its systematic testing and targeting.
Practical significance. The experimental data obtained create the basis for the development of engineering methods for calculating and designing ink-ink systems, and also expand theoretical representations about gas dynamics and local air heat transfer during the intake in piston engine. The individual results of the work were made to the implementation of the Ural Diesel Motor Plant LLC in the design and modernization of 6DM-21L and 8DM-21l engines.
Methods for determining the flow rate of the pulsating air flow in the inlet pipe of the engine and the intensity of instantaneous heat transfer in it;
Experimental data on gas dynamics and an instantaneous local heat transfer coefficient in the inlet channel of the input channel in the intake process;
The results of the generalization of the data on the local coefficient of air heat transfer in the inlet channel of the DVS in the form of empirical equations;
Approbation of work. The main results of studies set forth in the thesis reported and were presented at the "Reporting Conferences of Young Scientists", Yekaterinburg, UGTU-UPI (2006 - 2008); scientific seminars Department "Theoretical heat engineering" and "Turbines and engines", Yekaterinburg, UGTU-UPI (2006 - 2008); Scientific and Technical Conference "Improving the efficiency of power plants of wheeled and tracked machines", Chelyabinsk: Chelyabinsk Higher Military Automobile Communist Party School (Military Institute) (2008); Scientific and Technical Conference "Development of Engineering in Russia", St. Petersburg (2009); on the Scientific and Technical Council under Ural Diesel Motor Plant LLC, Yekaterinburg (2009); On the Scientific and Technical Council for OJSC NII Autotractor Technology, Chelyabinsk (2009).
The dissertation work was performed at the departments "Theoretical heat engineering and" turbines and engines ".
1. Review of the current state of the study of piston inlet inlet systems
To date, there are a large number of literature, in which the constructive performance of various systems of piston engines of internal combustion, in particular, individual elements of the inlet systems of the ink systems are considered. However, there is practically no substantiation of the proposed design solutions by analyzing gas dynamics and heat transfer of the inlet process. And only in individual monographs provide experimental or statistical data on the results of operation, confirming the feasibility of one or another constructive performance. In this regard, it can be argued that until recently, insufficient attention was paid to the study and optimization of piston engines inlet systems.
In recent decades, in connection with the tightening of economic and environmental requirements for internal combustion engines, researchers and engineers are beginning to pay more and more attention to improving intake systems of both gasoline and diesel engines, believing that their performance is largely dependent on the perfection of processes occurring In gas-air paths.
1.1 Basic elements of piston inlet inlet systems
The intake system of the piston engine, in general, consists of a air filter, an intake manifold (or inlet tube), cylinder heads that contain intake and outlet channels, as well as the valve mechanism. As an example, in Figure 1.1, a diagram of the intake system of the YMZ-238 diesel engine is shown.
Fig. 1.1. Scheme of the intake system of the YMZ-238 diesel engine: 1 - intake manifold (tube); 2 - rubber gasket; 3.5 - connecting nozzles; 4 - Estimated gasket; 6 - hose; 7 - Air filter
The choice of optimal structural parameters and the aerodynamic characteristics of the intake system predetermine the efficient workflow and high level of output indicators of internal combustion engines.
Briefly consider each composite element of the intake system and its main functions.
The cylinder head is one of the most complex and important elements in the internal combustion engine. From the correct selection of the shape and size of the main elements (first of all, the perfection of filling and mixing processes is largely depends on the size of intake and exhaust valves).
The cylinder heads are mainly made with two or four valves on the cylinder. The advantages of the two-flame design are the simplicity of manufacturing technology and the design scheme, in smaller structural mass and value, the number of moving parts in the drive mechanism, maintenance and repair costs.
The advantages of four-flaped structures consists in better use of the area limited by the cylinder circuit, for the passing areas of the valve gorlovin, in a more efficient gas exchange process, in a smaller thermal tension of the head due to a more uniform thermal state, in the possibility of central placement of the nozzle or candles, which increases the uniformity of the thermal state Parts of the piston group.
There are other designs of cylinder heads, for example, with three inlet valves and one or two graduation per cylinder. However, such schemes are applied relatively rare, mainly in highly affiliated (racing) engines.
The influence of the number of valves on gas dynamics and heat transfer in the inlet path is generally practically not studied.
The most important elements of the cylinder head from the point of view of their influence on gas dynamics and heat exchange input process in the engine are the types of inlet channels.
One of the ways to optimize the filling process is profiling inlet channels in the cylinder head. There is a wide variety of shapes of profiling in order to ensure the directional movement of fresh charge in the engine cylinder and improving the mixing process, they are described in the most detailed.
Depending on the type of mixing process, the intake channels are performed by one-functional (disgustable), providing only filling with cylinders with air, or two-function (tangential, screw or other type) used for inlet and twisting air charge in the cylinder and combustion chamber.
Let us turn to the question of the features of the design of intake collectors of gasoline and diesel engines. An analysis of the literature shows that the intake collector (or ink tube) is given little attention, and it is often considered only as a pipeline for supplying air or fuel-air mixture into the engine.
The air filter is an integral part of the inlet system of piston engine. It should be noted that in the literature, more attention is paid to the design, materials and resistance of the filter elements, and at the same time the effect of the filtering element on gas-dynamic and heat exchanged indicators, as well as the expenditure characteristics of piston internal combustion system, is practically not considered.
1.2 Gas dynamics of flow in inlet channels and methods for studying the inlet process in piston engine
For a more accurate understanding of the physical essence of the results obtained by other authors, they are outlined simultaneously with the theoretical and experimental methods used, since the method and result are in a single organic communication.
Methods for the study of inlet systems of the KHOs can be divided into two large groups. The first group includes theoretical analysis of the processes in the inlet system, including their numerical simulation. To the second group, we will draw all the ways to experimentally study the inlet process.
The choice of research methods, estimates and adjusting intake systems is determined by the goals set, as well as existing material, experimental and calculated possibilities.
To date, there are no analytic methods that allow it to be fairly accurate to estimate the level of intensity of gas in the combustion chamber, as well as solve private problems associated with a description of the movement in the intake path and the gas expiration from the valve gap in the real unsaluable process. This is due to the difficulties of describing the three-dimensional flow of gases on curvilinear channels with sudden obstacles, a complex spatial stream structure, with a jet gas outlet through the valve slot and a partially filled space of a variable volume cylinder, the interaction of flows between themselves, with the walls of the cylinder and the movable bottom of the piston. Analytical determination of the optimal field of velocity in the inlet pipe, in the ring valve slot and the distribution of flows in the cylinder is complicated by the lack of accurate methods for evaluating aerodynamic losses arising from a fresh charge in the inlet system and when gas in the cylinder and flow around its internal surfaces. It is known that in the channel there are unstable zones of the transition of the flow from laminar to the turbulent flow mode, the region of the separation of the boundary layer. The flow structure is characterized by variables by time and the place of Reynolds, the level of non-stationarity, intensity and the scale of turbulence.
Many multidirectional work is devoted to numerical modeling of the movement of the air charge on the inlet. They produce modeling of the vortex intake-flux of the inlet of the inlet of the inlet of the inlet valve, the calculation of the three-dimensional flow in the inlet channels of the cylinder head, modeling the stream in the inlet window and the engine cylinder, an analysis of the effect of direct-flow and swirling streams on the mixing process and calculated studies of the effect of the charge twisting in the diesel cylinder The magnitude of emissions of nitrogen oxides and indicator cycle indicators. However, only in some of the works, numerical simulation is confirmed by experimental data. And solely on theoretical studies it is difficult to judge the accuracy and degree of applicability of the data. It should also be emphasized that almost all numerical methods are mainly aimed at studying the processes in the already existing design of the inlet of the inlet system of the intensity of the DVS to eliminate its deficiencies, and not to develop new, effective design solutions.
In parallel, the classical analytical methods for calculating the workflow in the engine and separate gas exchange processes in it are applied. However, in the calculations of the flow of gas in the inlet and exhaust valves and channels, the equations of one-dimensional stationary flow are mainly used, taking the current quasi-stationary. Therefore, the calculation methods under consideration are exclusively estimated (approximate) and therefore require experimental refinement in laboratory or on a real engine during bench tests. Methods for calculating the gas exchange and the main gas-dynamic indicators of the inlet process in a more difficult formulation are developing in the works. However, they also give only general information about the processes discussed, do not form a sufficiently complete representation of gas-dynamic and heat exchange rates, since they are based on statistical data obtained in mathematical modeling and / or static purges of the inlet tract of the ink and on the methods of numerical simulation.
The most accurate and reliable data on the inlet process in the piston engine can be obtained in the study on real-operating engines.
To the first studies of the charge in the engine cylinder on the shaft test mode, the classic experiments of Ricardo and the Cash can be attributed. Riccardo installed an impeller in the combustion chamber and recorded its rotational speed when the engine shaft is checked. The anemometer fixed the average gas speed value for one cycle. Ricardo introduced the concept of "vortex ratio", corresponding to the ratio of the frequency of the impeller, measured the rotation of the vortex, and the crankshaft. The CASS installed the plate in the open combustion chamber and recorded the effect on the air flow. There are other ways to use plates associated with tensidate or inductive sensors. However, the installation of plates deform the rotating stream, which is the disadvantage of such methods.
A modern study of gas-dynamics directly on the engines requires special measuring instruments that are capable of working under adverse conditions (noise, vibration, rotating elements, high temperatures and pressure when combustion of fuel and in exhaust channels). In this case, the processes in the DVS are high-speed and periodic, so the measuring equipment and sensors must have very high speed. All this greatly complicates the study of the inlet process.
It should be noted that at present, methods of natural research on engines are widely used, both to study the flow of air in the inlet system and the engine cylinder, and for the analysis of the effect of vortex formation on the inlet for the toxicity of exhaust gases.
However, natural studies, where at the same time a large number of diverse factors acts, do not allow to penetrate the details of the mechanism of a separate phenomenon, do not allow to use high-precision, complex equipment. All this is the prerogative of laboratory studies using complex methods.
The results of the study of gas dynamics of the intake process, obtained in the study on engines are quite detailed in the monograph.
Of these, the greatest interest is the oscillogram of changes in the air flow rate in the input section of the inlet channel of the engine of C10.5 / 12 (D 37) of the Vladimir Tractor Plant, which is presented in Figure 1.2.
Fig. 1.2. Flow parameters in the input section of the channel: 1 - 30 s -1, 2 - 25 s -1, 3 - 20 s -1
Measurement of the air flow rate in this study was carried out using a thermoemometer operating in DC mode.
And here it is appropriate to pay attention to the very method of thermoemometry, which, thanks to a number of advantages, received such widespread gas-dynamics of various processes in research. Currently, there are various schemes of thermoanemometers depending on the tasks and the field of research. The most detailed theory of thermoenemometry is considered in. It should also be noted a wide variety of thermoemometer sensor designs, which indicates the widespread use of this method in all areas of industry, including engineering.
Consider the question of the applicability of the thermoenemometry method for studying the inlet process in piston engine. Thus, the small dimensions of the sensitive element of the thermoemometer sensor do not make significant changes in the nature of the flow of air flow; High sensitivity of the anemometers allows you to register fluctuations with small amplitudes and high frequencies; The simplicity of hardware scheme makes it possible to easily record the electrical signal from the output of the thermoemometer, followed by its processing on a personal computer. In thermomemometry, it is used in the sizing modes of one-, two- or three-component sensors. A thread or films of refractory metals with a thickness of 0.5-20 μm and a length of 1-12 mm are usually used as a sensitive element of the thermoemometer sensor, which is fixed on chromium or chromium-leather legs. The latter pass through a porcelain two-, three-way or four-grate tube, which is put on the metal case sealing from the breakthrough, the metal case, oked into the block head for the study of the intra-cylinder space or in pipelines to determine the average and ripple components of the gas velocity.
And now back to the oscillogram shown in Figure 1.2. The chart draws attention to the fact that it presents a change in the air flow rate from the angle of rotation of the crankshaft (P.K.V.) only for the intake tact (? 200 degrees. P.K.V.), whereas the rest Information on other clocks as it were "cropped". This oscillogram is obtained for the rotational speed of the crankshaft from 600 to 1800 min -1, while in modern engines the range of operating speeds is much wider: 600-3000 min -1. Attention is drawn to the fact that the flow rate in the tract before opening the valve is not zero. In turn, after closing the intake valve, the speed is not reset, probably because in the path there is a high-frequency reciprocating flow, which in some engines is used to create a dynamic (or inertigice).
Therefore, it is important for understanding the process as a whole, data on the change in air flow rate in the inlet tract for the entire workflow of the engine (720 degrees, PKV) and in the entire operating range of the crankshaft rotation frequency. These data is necessary for improving the inlet process, searching for ways to increase the magnitude of a fresh charge entered into the engine cylinders and creating dynamic supercharow systems.
Briefly consider the peculiarities of dynamic supercharged in piston engine, which is carried out in different ways. Not only the gas distribution phases, but also the design of intake and graduation paths affect the intake process. The movement of the piston when the intake tact leads to an open intake valve to the formation of the backpressure wave. At an open intake pipeline, this pressure wave occurs with a mass of fixed ambient air, reflected from it and moves back to the inlet pipe. The fluctuate airfold of the air column in the inlet pipeline can be used to increase the filling of cylinders with fresh charge and, thereby obtaining a large amount of torque.
With a different form of dynamic superchard - inertial superior, each inlet channel of the cylinder has its own separate resonator tube, the corresponding length acoustics connected to the collecting chamber. In such resonator tubes, the compression wave coming from cylinders can spread independently of each other. When coordinating the length and diameter of individual resonator tubes with phases of the gas distribution phase, the compression wave, reflected in the end of the resonator tube, returns through the open inlet valve of the cylinder, thereby ensures its best filling.
The resonant reducing is based on the fact that in the air flow in the inlet pipeline at a certain rotational speed of the crankshaft there are resonant oscillations caused by the reciprocating movement of the piston. This, with the correct layout of the intake system, leads to a further increase in pressure and an additional adhesive effect.
At the same time, the mentioned dynamic boost methods operate in a narrow range of modes, require a very complex and permanent setting, since the acoustic characteristics of the engine are changed.
Also, gas dynamics data for the entire workflow of the engine can be useful to optimize the filling process and searches for increasing air flow through the engine and, accordingly, its power. At the same time, the intensity and scale of the turbulence of the air flow, which are generated in the inlet canal, as well as the number of vortices formed during the inlet process.
The rapid flow of charge and large-scale turbulence in the air flow provide good mixing of air and fuel and, thus, complete combustion with a low concentration of harmful substances in the exhaust gases.
One of the way to create the vortices in the intake process is the use of a flap that shares the intake path into two channels, one of which can overlap it, controlling the movement of the charge of the mixture. There are a large number of design versions to give the tangential component of the flow movement in order to organize directional vortices in the inlet pipeline and engine cylinder
. The purpose of all these solutions is to create and manage vertical vortices in the engine cylinder.
There are other ways to control the filling fresh charge. The design of a spiral intake canal is used in the engine with a different step of turns, flat venues on the inner wall and sharp edges at the channel output. Another device for regulating the vortex formation in the Cylinder of the engine is a spiral spring installed in the inlet channel and rigidly fixed by one end before the valve.
Thus, it is possible to note the trend of researchers to create large whirlwinds of different distribution directions on the inlet. In this case, the air flow must mainly contain large-scale turbulence. This leads to an improvement in the mixture and subsequent combustion of fuel, both in gasoline and diesel engines. And as a result, the specific consumption of fuel and emissions of harmful substances with spent gases are reduced.
At the same time, in the literature there are no information about attempts to control the vortex formation using transverse profiling - a change in the shape of the transverse section of the channel, and it is known to strongly affect the nature of the flow.
After the foregoing, it can be concluded that at this stage in the literature there is a significant lack of reliable and complete information on the gas dynamics of the inlet process, namely: change the speed of the air flow from the corner of the crankshaft for the entire workflow of the engine in the operating range of the crankshaft rotation frequency shaft; The effect of the filter on the gas dynamics of the intake process; the scale of the turbulence occurs during the intake; The influence of hydrodynamic nonstationarity on the consumables in the inlet tract of DVS, etc.
The urgent task is to search for the methods of increasing air flow through the engine cylinders with minimal engine refinement.
As already noted above, the most complete and reliable input data can be obtained from studies on real engines. However, this direction of research is very complex and expensive, and for a number of issues is almost impossible, therefore, the combined methods of studying processes in ICC have been developed by experimenters. Consider widespread from them.
The development of a set of parameters and methods of calculating and experimental studies is due to the large number of comprehensive analytical descriptions of the design of the inlet system of piston engine, the dynamics of the process and movement of the charge in inlet channels and the cylinder.
Acceptable results can be obtained when a joint study of the intake process on a personal computer using numerical modeling methods and experimentally through static purges. According to this technique, many different studies have been made. In such works, either the possibility of numerical simulation of swirling flows in the inlet system of the ink system, followed by testing the results using a purge in static mode on an inspector installation, or a calculated mathematical model is developed based on experimental data obtained in static modes or during the operation of individual modifications of engines. We emphasize that the basis of almost all such studies is taken experimental data obtained by the help of static blowing of the inlet system of the ink system.
Consider a classic way to study the intake process using a porch anemometer. With fixed valve lips, it produces a purge of the test channel with various second air consumption. For purge, real cylinder heads are used, cast from metal, or their models (collapsible wooden, gypsum, from epoxy resins, etc.) assembled with valves that guide bush lines and saddles. However, as described comparative tests, this method provides information on the effect of the form of the path, but the impeller does not respond to the action of the entire flow of air in cross section, which can lead to a significant error when estimating the intensity of the charge in the cylinder, which is confirmed mathematically and experimentally.
Another widespiliated method of studying the filling process is a method using a hidden lattice. This method differs from the previous one by the fact that the absorbed rotating air flow is sent to the fairing on the blade of the hidden grid. In this case, the rotating stream is stolen, and a jet moment is formed on the blades, which is recorded by the capacitive sensor in the magnitude of the Torcion spin angle. The hidden stream, having passed through the grille, flows through an open section at the end of the sleeve into the atmosphere. This method allows you to comprehensively evaluate the intake channel for energy indicators and by the magnitude of aerodynamic losses.
Even despite the fact that the methods of research on static models give only the most general idea of \u200b\u200bthe gas-dynamic and heat exchange characteristics of the inlet process, they still remain relevant due to their simplicity. Researchers are increasingly using these methods only for preliminary assessment of the prospects of intake systems or conversion already existing ones. However, for a complete, detailed understanding of the physics of phenomena during the inlet process of these methods is clearly not enough.
One of the most accurate and efficient ways to study the inlet process in the engine are experiments on special, dynamic installations. In the assumption that gas-dynamic and heat exchange features and characteristics of the charge in the inlet system are functions of only geometric parameters and regime factors for the study, it is very useful to use a dynamic model - an experimental installation, which most often represents a single-cylinder engine model on various high-speed modes acting with The help of a crankshaft test from an extraneous energy source, and equipped with different types of sensors. In this case, you can estimate the total effectiveness from certain solutions or their effectiveness is element. In general, such an experiment is reduced to determine the flow characteristics in various elements of the intake system (instantaneous values \u200b\u200bof temperature, pressure and speed), varying the corner of the rotation of the crankshaft.
Thus, the most optimal way to study the inlet process, which gives full and reliable data is the creation of a single-cylindrous dynamic model of piston engine, driven to rotation from an extraneous energy source. In this case, this method allows to investigate both gas-dynamic and heat exchangers of the filling process in the piston internal combustion engine. The use of thermoenemometric methods will make it possible to obtain reliable data without a significant effect on the processes occurring in the intake system of the experimental engine model.
1.3 Characteristics of heat exchange processes in the inlet system of piston engine
The study of heat exchange in piston internal combustion engine began in fact from the creation of the first working machines - J. Lenoara, N. Otto and R. Diesel. And of course at the initial stage, special attention was paid to the study of heat exchange in the engine cylinder. The first classic works in this direction can be attributed.
However, only work carried out by V.I. Grinevik, became a solid foundation, which turned out to be possible to build the theory of heat exchange for piston engines. The monograph in question is primarily devoted to the thermal calculation of intra-cylinder processes in the OI. At the same time, it can also find information about the heat exchanged indicators in the inlet process of interest to us, namely, there are statistical data on the magnitude of the heating of fresh charge, as well as empirical formulas to calculate the parameters at the beginning and end of the intake tact.
Further, researchers began to solve more private tasks. In particular, V. Nusselt received and published a formula for heat transfer coefficient in a piston engine cylinder. N.R. The brilling in his monograph clarified the formula of Nusselt and quite clearly proved that in each case (engine type, method of mixing formation, speed-rate, booming level) Local heat transfer coefficients should be clarified by the results of direct experiments.
Another direction in the study of piston engines is the study of heat exchange in the flow of exhaust gases, in particular, obtaining data on heat transfer during a turbulent gas flow in the exhaust pipe. A large number of literature is devoted to solving these tasks. This direction is quite well studied both in static purge conditions and under hydrodynamic nonstationarity. This is primarily due to the fact that, by improving the exhaust system, it is possible to significantly increase the technical and economic indicators of the piston internal combustion engine. In the course of the development of this area, many theoretical works were conducted, including analytical solutions and mathematical modeling, as well as many experimental studies. As a result of such a comprehensive study of the release process, a large number of indicators characterizing the process of release were proposed for which the quality of the design of the exhaust system can be assessed.
The study of heat exchange of the intake process is still given insufficient attention. This can be explained by the fact that studies in the field of heat exchange optimization in the cylinder and the exhaust tract were initially more effective in terms of improving the competitiveness of piston engine. However, currently the development of the engine industry has reached such a level that an increase in the engine indicator at least a few tenths percent is considered to be a serious achievement for researchers and engineers. Therefore, taking into account the fact that the directions of improving these systems are mainly exhausted, currently more and more specialists are looking for new opportunities for improving the workflows of piston engines. And one of such directions is the study of heat exchange during the inlet in the inlet.
In the literature on heat exchange in the intake process, work can be distinguished on the study of the influence of the intensity of the vortex flow of charge on the inlet on the thermal state of the engine parts (cylinder head, intake and exhaust valve, cylinder surfaces). These works are of great theoretical character; Based on solving the nonlinear Navier-Stokes equations and Fourier-Ostrogradsky, as well as mathematical modeling using these equations. Taking into account a large number of assumptions, the results can be taken as a basis for experimental studies and / or be estimated in engineering calculations. Also, these works contain experimental studies to determine local non-stationary heat fluxes in a diesel combustion chamber in a wide range of intensity inlet air intensity.
The above-mentioned heat exchange work in the inlet process most often do not affect the influence of gas dynamics on the local intensity of heat transfer, which determines the size of the heating of fresh charge and temperature voltages in the intake manifold (pipe). But, as is well known, the magnitude of the heating of fresh charge has a significant effect on the mass consumption of fresh charge through the engine cylinders and, accordingly, its power. Also, a decrease in the dynamic intensity of heat transfer in the inlet path of the piston engine can reduce its temperature tension and thus will increase the resource of this element. Therefore, the study and solving these tasks is an urgent task for the development of the engine building.
It should be indicated that currently for engineering calculations use static purging data, which is not correct, since non-stationarity (flow pulsation) strongly affect heat transfer in the channels. Experimental and theoretical studies indicate a significant difference in heat transfer coefficient in nonstationary conditions from a stationary case. It can reach a 3-4-fold value. The main reason for this difference is the specific restructuring of the turbulent stream structure, as shown in.
It is established that as a result of the effect on the flow of dynamic nonstationarity (stream acceleration), it takes place in the kinematic structure, leading to a decrease in the intensity of heat exchange processes. Also, the work was found that the acceleration of the flow leads to a 2-3-to-alarm increase in the tanning tangent stresses and the subsequently as much as the decrease in local heat transfer coefficients.
Thus, for calculating the size of the heating of fresh charge and determining the temperature stresses in the intake manifold (pipe), data on the instantaneous local heat transfer is needed in this channel, since the results of static purges can lead to serious errors (more than 50%) when determining the heat transfer coefficient in the intake tract that is unacceptable even for engineering calculations.
1.4 Conclusions and setting the objectives of the study
Based on the above, the following conclusions can be drawn. The technological characteristics of the internal combustion engine are largely determined by the aerodynamic quality of the intake path as a whole and individual elements: the intake manifold (inlet tube), the channel in the cylinder head, its neck and the valve plate, the combustion chambers in the bottom of the piston.
However, it is currently the focus on the optimization of the channel design in the cylinder head and complex and expensive cylinder filling systems with a fresh charge, while it can be assumed that only by profiling intake manifold can be affected by gas-dynamic, heat exchange and engine consumables.
Currently, there are a wide variety of means and measurement methods for dynamic study of the inlet process in the engine, and the main methodological complexity consists in their correct choice and use.
Based on the above analysis of literature data, the following dissertation tasks may be formulated.
1. To establish the effect of the intake manifold configuration and the presence of the filtering element on the gas dynamics and the consumables of the piston engine of the internal combustion, as well as reveal the hydrodynamic factors of the heat exchange of the pulsating stream with the walls of the inlet channel channel.
2. Develop a method for increasing air flow through an inlet system of piston engine.
3. Find the basic patterns of changes in the instantaneous local heat transfer in the inlet path of the piston engine in hydrodynamic nonstationarity in the classic cylindrical channel, as well as to find out the effect of the intake system configuration (profiled inserts and air filters) to this process.
4. To summarize the experimental data on an instantaneous local heat transfer coefficient in the piston inlet inlet manifold.
To solve the tasks to develop the necessary techniques and create an experimental setup in the form of a tool model of piston engine, equipped with a control and measuring system with automatic collection and data processing.
2. Description of the experimental installation and measurement methods
2.1 Experimental installation for the study of the inlet inlet
The characteristic features of the studied intake processes are their dynamism and frequency due to a wide range of rotational speed of the engine and the harmonicity of this periodicals associated with the uneven piston movement and changes in the intake path configuration in the valve zone zone. The last two factors are interconnected with the action of the gas distribution mechanism. Reproduce such conditions with sufficient accuracy can only with the help of a field model.
Since gas-dynamic characteristics are functions of geometric parameters and regime factors, the dynamic model must match the engine of a certain dimension and operate in characteristic high-speed modes of the crankshaft test, but already from an extraneous energy source. Based on this data, it is possible to develop and evaluate the total effectiveness from certain solutions aimed at improving the intake path as a whole, as well as separately by different factors (constructive or regime).
For the study of gas dynamics and heat transfer process in the piston engine of internal combustion, an experimental installation was designed and manufactured. It was developed on the basis of the engine model 11113 VAZ - Oka. When creating the installation, the prototype details were used, namely: connecting rod, piston finger, piston (with refinement), gas distribution mechanism (with refinement), crankshaft pulley. Figure 2.1 shows a longitudinal section of the experimental installation, and in Figure 2.2 is its transverse section.
Fig. 2.1. Lady cut of the experimental installation:
1 - elastic coupling; 2 - rubber fingers; 3 - rod cervical; 4 - native cervix; 5 - cheek; 6 - nut M16; 7 - counterweight; 8 - Nut M18; 9 - indigenous bearings; 10 - supports; 11 - Bearings connecting rod; 12 - rod; 13 - piston finger; 14 - piston; 15 - cylinder sleeve; 16 - cylinder; 17 - base of the cylinder; 18 - cylinder supports; 19 - Fluoroplast Ring; 20 - reference plate; 21 - hexagon; 22 - gasket; 23 - inlet valve; 24 - graduation valve; 25 - distribution shaft; 26 - camshaft pulley; 27 - crankshaft pulley; 28 - toothed belt; 29 - Roller; 30 - tensioner stand; 31 - tensioner bolt; 32 - Maslenka; 35 - Asynchronous Engine
Fig. 2.2. Transverse section of experimental installation:
3 - rod cervical; 4 - native cervix; 5 - cheek; 7 - counterweight; 10 - supports; 11 - Bearings connecting rod; 12 - rod; 13 - piston finger; 14 - piston; 15 - cylinder sleeve; 16 - cylinder; 17 - base of the cylinder; 18 - cylinder supports; 19 - Fluoroplast Ring; 20 - reference plate; 21 - hexagon; 22 - gasket; 23 - inlet valve; 25 - distribution shaft; 26 - camshaft pulley; 28 - toothed belt; 29 - Roller; 30 - tensioner stand; 31 - tensioner bolt; 32 - Maslenka; 33 - Insert profiled; 34 - measuring channel; 35 - Asynchronous Engine
As can be seen from these images, the installation is a natural model of the single-cylinder internal combustion engine of dimension 7.1 / 8.2. A torque from an asynchronous engine is transmitted through an elastic coupling 1 with six rubber fingers 2 on the crankshaft of the original design. The clutch used is capable of significantly compensate for the inconseability of the compound of the shafts of the asynchronous motor and the crankshaft of the installation, as well as to reduce dynamic loads, especially when starting and stopping the device. The crankshaft in turn consists of a connecting rod cervix 3 and two indigenous necks 4, which are connected to each other with cheeks 5. The rod cervix is \u200b\u200bpressed with tension in the cheek and fixed using nuts 6. To reduce vibrations to cheeks are fastened with anti-test bolts 7 . The axial movement of the crankshaft hinders the nut 8. The crankshaft rotates in the closed rolling bearings 9 fixed in the supports 10. Two closed rolling bearing 11 are installed onto a connecting rod neck, on which the connecting rod 12 is mounted. The use of two bearings in this case is associated with the landing size of the connecting rod . To the connecting rod with a piston finger 13, the piston 14 is mounted on the cast-iron sleeve 15, pressed in the steel cylinder 16. The cylinder is mounted on the base 17, which is placed on the cylinder supports 18. One wide fluoroplastic ring 19 is installed on the piston, instead of three standard Steel. The use of pig-iron sleeve and fluoroplastic ring provides a sharp decline in friction in pairs of piston - sleeves and piston rings - sleeve. Therefore, the experimental installation is capable of working a short time (up to 7 minutes) without a lubrication system and cooling system on the operating frequencies of the crankshaft rotation.
All major fixed elements of the experimental installation are fixed on the base plate 20, which, with two hexagons, 21 is attached to the laboratory table. To reduce the vibration between the hexagon and the support plate there is a rubber gasket 22.
The mechanism of timing experimental installation is borrowed from the VAZ 11113 car: a block head is used assembly with some modifications. The system consists of an inlet valve 23 and an exhaust valve 24, which are controlled using a camshaft 25 with pulley 26. The camshaft pulley is connected to the crankshaft pulley 27 with a toothed belt 28. On the crankshaft of the installation shaft placed two pulleys to simplify the drive belt tension system camshaft. The belt tension is controlled by roller 29, which is installed on the rack 30, and the tensioner bolt 31. Masliners 32 were installed for lubrication of the camshaft bearings, oil, of which gravity comes to the sliding bearings of the camshaft.
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