Gasodynamic analysis of the exhaust system. Gas dynamics of resonant exhaust pipes. For pipeline with square cross section
Use of resonant exhaust pipes On the motor models of all classes allows you to dramatically increase the sports results of the competition. However, the geometric parameters of pipes are determined, as a rule, by the method of trial and error, since so far there is no clear understanding and clear interpretation of the processes occurring in these gas-dynamic devices. And in the few sources of information on this occasion, conflicting conclusions that have an arbitrary interpretation are given.
For a detailed study of processes in the pipes of a customized exhaust, a special installation was created. It consists of a stand for running engines, an adapter Motor - a pipe with fittings for the selection of static and dynamic pressure, two piezoelectric sensors, two-beam oscilloscope C1-99, a camera, a resonant exhaust pipe from the R-15 engine with a "telescope" and a homemade tube with black Surfaces and additional thermal insulation.
Pressures in the pipes in the exhaust area was determined as follows: the motor was displayed on resonant revisions (26000 rpm), data from the Piezoelectric sensors attached to the octuers of the Piezoelectric sensors were displayed on the oscilloscope, the frequency of the sweep of which is synchronized with the engine rotation frequency, and the oscillogram was recorded on the film.
After the film is manifested in a contrasting developer, the image was transferred to the traction on the scale of the oscilloscope screen. The results for the pipe from the engine R-15 are shown in Figure 1 and for a homemade tube with black and additional thermal insulation - in Figure 2.
On schedules:
P dyn - dynamic pressure, p st - static pressure. OSO - Opening of the exhaust window, NMT - Lower dead point, the link is the closure of the exhaust window.
Analysis of curves allows you to identify the distribution of pressure at the input of the resonant tube in the function of the crankshaft rotation phase. Increasing the dynamic pressure from the moment the exhaust window is discovered with the diameter of the output nozzle 5 mm occurs for R-15 approximately 80 °. And its minimum is within 50 ° - 60 ° from the bottom of the dead point at maximum purge. Increased pressure in the reflected wave (from a minimum) at the time of closing the exhaust window is about 20% of the maximum value of R. delay in the action of reflected exhaust wave - from 80 to 90 °. For static pressure, it is characterized by an increase in 22 ° C "Plateau" on the chart up to 62 ° from the opening of the exhaust window, with a minimum of 3 ° from the bottom of the dead point. Obviously, in the case of using a similar exhaust pipe, purge fluctuations occur at 3 ° ... 20 ° after the bottom of the dead point, and by no means 30 ° after the opening of the exhaust window was previously thought.
These studies of the homemade pipe differ from the data R-15. Increased dynamic pressure up to 65 ° from the opening of the exhaust window is accompanied by a minimum located 66 ° after the bottom of the dead point. At the same time, the increase in pressure of the reflected wave from the minimum is about 23%. Loading in the action of exhaust gases is less, which is probably due to increasing temperature in the heat insulated system, and is about 54 °. Purge oscillations are marked at 10 ° after the bottom of the dead point.
Comparing graphics, it can be noted that static pressure in the heat insulated pipe at the time of closing the exhaust window is less than in R-15. However, dynamic pressure has a maximum of a reflected wave of 54 ° after the closure of the exhaust window, and in R-15, this maximum shifted by 90 "! The differences are associated with the difference in the diameters of the exhaust pipes: on R-15, as already mentioned, the diameter is 5 mm, and on the heat insulated - 6.5 mm. In addition, due to the more advanced geometry of the pipe R-15, the coefficient of restoration of static pressure is more.
The efficiency coefficient of the resonant exhaust pipe largely depends on the geometric parameters of the pipe itself, the cross-section of the exhaust pipe of the engine, temperature regime, and gas distribution phases.
The use of control traverses and selecting the temperature regime of the resonant exhaust pipe will allow to shift the maximum pressure of the reflected exhaust gas wave by the time the exhaust window is closed and thus sharply increase its efficiency.
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 Estimated research Efficiency 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 the service personnel from burns, the exhaust pipe 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 large engines, compensators also combine individual sections of exhaust pipelines, which are compiled according to technological reasons.
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, neither in this nor in other 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 of engines with gas turbine supervision applies a permanent pressure supercharge 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 often cases of inconsistency of the projected and real dependences of the expenditure characteristics from the geometry of the channel.
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 ripples of the gas flow for 1x to 150 mm would be much less with a period than IPI \u003d 115 ms, the current should be characterized as a course with a high degree of non-stationary. 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. Disc 1 was installed with an electric motor 4 so that one of the disk teeth corresponds to the position of the piston in the upper dead point, and the other, respectively, the bottom dead point and mounted to the shaft of the coupling 3. The motor of the electric motor and camshaft The piston engine was 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 volume flow VX through the outlet channels of different execution from the rotational speed crankshaft P. They indicate that in the entire range of the rotation frequency of the crankshaft, with a constant ejection, the volume flow rate through the exhaust system increases, which should lead to better cleaning of cylinders from exhaust gases and increase 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.
Size: px.
Start showing from page:
Transcript.
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 bottlenecks in 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 solution will allow to carry out a reasonable choice of design and technological solutions, increase the scientific technical level of design, will provide an opportunity to reduce the engine creating cycle and obtain 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 of a mathematical model of 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 of tasks allows to achieve the main objective of the work - the creation of an engineering method for calculating the local parameters of convective heat exchange in the GVK of the 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. first used mathematical model, 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 the fundamental laws of conservation of energy, mass, pulse with appropriate 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 the experimental study, as well as satisfactory agreement 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. The overall characteristic of the work is given. 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. A review of the constructive forms of graduation and intake channels in the head of the cylinder block and the analysis of the methods and results of experimental and emission-theoretical studies of both stationary and non-stationary gas flows in the gas-air paths of internal combustion engines are carried out. 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 the closed engine working cycle includes the calculated relationships describing the processes in the engine cylinders and parts of the intake and outcomes. 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. The measurements were carried out both by speed and loading characteristics at different constant frequencies of rotation of the 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 the outer surfaces - the outlet channel -B-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.
For the rights of the manuscript of Bulgakov Nikolai Viktorovich Mathematical modeling and numerical studies of turbulent heat and mass transfer in internal combustion engines 05.13.18 - Math modeling,
Reviewed by the official opponent of Dragomirov Sergey Grigorievich on the dissertation of Smolensk Natalia Mikhailovna "Improving engine efficiency with spark ignition by applying gas composite
Review of the official opponent K.T.N., Kudinov Igor Vasilyevich on the dissertation of Supernyak Maxim Igorevich "Investigation of cyclic processes of thermal conductivity and thermal hemogeneousness in the thermal layer of solid
Laboratory work 1. Calculation of similarity criteria for the study of heat and mass transfer processes in liquids. The purpose of the work is to use MS Excel spreadsheets in the calculation
On June 12, 2017, the joint process of convection and thermal conductivity is called convective heat exchange. Natural convection is caused by the difference in specific scales unevenly heated medium, is carried out
Estimated experimental method for determining the flow rate of the purge windows of the two-stroke engine with crank-chamber EA Herman, A.A. Balashov, A.G. Kuzmin 48 Power and Economic Indicators
UDC 621.432 Methods for estimating boundary conditions When solving the problem of determining the thermal state of the engine piston 4ч 8.2 / 7.56 GV Lomakin proposed a universal method of assessing boundary conditions when
Section "Piston and gas turbine engines". Method of increasing the filling of the cylinders of the high-speed motor of the internal combustion of D.T.N. prof. FOMIN V.M., K.T.N. Runovsky K.S., K.T.N. Apelinsky D.V.,
UDC 621.43.016 A.V. Trin, Cand. tehn Science, A.G. Kosulin, Cand. tehn Science, A.N. Abramenko, Ing. Using local air cooling valve assembly for forced autotractor diesel engines
The heat transfer coefficient of the exhaust manifold DVS Sukhonos R. F., Magistrand SNTU Head of Mazin V. A., Cand. tehn Sciences, Doc. The SNTU with the distribution of combined FCs becomes important
Some scientific and methodological activities of employees of the DPO system in AltGTU Calculated and experimental method for determining the coefficient of flowing output windows of a two-stroke engine with a crank chamber
State Space Agency of Ukraine State Enterprise "Design Bureau" Southern ". MK Yangel "on the rights of manuscript Shevchenko Sergey Andreevich UDC 621.646.45 Improvement of the pneumatic system
Abstract discipline (training course) M2.DV4 Local heat transfer in DVS (cipher and the name of the discipline (training course)) The current development of technology requires widespread introduction of new
Thermal conductivity in the nonstationary process The calculation of the temperature field and heat fluxes in the process of thermal conductivity will look at the example of heating or cooling solids, since in solids
Review of the official opponent on the dissertation work Moskalenko Ivan Nikolayevich "Improving the methods of profiling of the side surface of the pistons of internal combustion engines" represented by
UDC 621.43.013 E.P. Voropaev, Ing. Modeling the external high-speed engine characteristic Sportbike Suzuki GSX-R750 Introduction The use of three-dimensional gas-dynamic models in the design of piston
94 Equipment and Technology UDC 6.436 P. V. Dvorkin St. Petersburg State University of Communications Communication Definition of the heat transfer coefficient in the walls of the combustion chamber currently does not exist
Review of the official opponent on the dissertation work Chichilanova Ilya Ivanovich, made on the topic "Improving methods and means of diagnosing diesel engines»For a scientific degree
UDC 60.93.6: 6.43 E. A. Kochetkov, A. S. Kuryvlev Province of the studio of the studio of the cavitation wear on the engines of cavitation wear
Laboratory work 4 Study of heat transfer with free air movement Task 1. To carry out heat engineering measurements to determine the heat transfer coefficient of horizontal (vertical) pipe
UDC 612.43.013 Workflows in DVS A.A. Handrimailov, Inzh., V.G. Malt, Dr. Tehn. Sciences The structure of the air charge flow in the diesel cylinder on the intake and compression tact. Introduction The process of volume and film
UDC 53.56 Analysis of the equations of the laminar boundary layer of the DCC. tehn Sciences, prof. Yesman R. I. Belarusian National Technical University when transporting liquid energy in canals and pipelines
Approve: LD in I / - GT L. Eractor for scientific work and a * ^ 1 Doctor biological! Ssor M.G. Baryshev ^., - * C ^ x \\ "L, 2015. Recreation of a leading organization on the dissertation work of Britia Elena Pavlovna
Heat transfer plan: 1. Heat transfer at the free movement of fluid in a large volume. The heat transfer at the free movement of the fluid in a limited space 3. The forced movement of fluid (gas).
Lecture 13 Calculated equations in heat transfer processes Definition of heat transfer coefficients in processes without changing the aggregate state of coolant heat exchange processes without changing the aggregate
Review of the official opponent on the dissertation of Nekrasova Svetlana Olegovna "Development of a generalized engine design methodology with an external heat supply with a pulsation pipe" presented to protection
15.1.2. Convective heat transfer under the forced movement of the fluid in pipes and channels In this case, the dimensionless heat transfer coefficient of the criterion (number) of nusselt depends on the criterion of the GraolsHof (
Reviewing the official opponent of Tsydipova Baldanjo Dashievich on the dissertation work of Dabayeva Maria is acknowledged "Method of studying oscillations of solids systems installed on an elastic rod, based on
Russian Federation (19) RU (11) (51) MPK F02B 27/04 (2006.01) F01N 13/08 (2010.01) 169 115 (13) U1 RU 1 6 9 1 1 5 U 1 Federal Intellectual Property Service (12) Description of the useful model
MODULE. Convective heat exchange in single-phase media Specialty 300 "Technical Physics" Lecture 10. The similarity and modeling of the processes of convective heat exchange modeling of convective heat exchange processes
UDC 673 RV Kolomiets (Ukraine, Dnepropetrovsk, Institute of Technical Mechanics of the National Academy of Sciences of Ukraine and the Civil Code of Ukraine) Convective heat exchange in AeroFoundation Dryer Setting the problem
Reviewing the official opponent on the dissertation work of the sublyega Victoria Olegovna "Multi-scale numerical modeling of gas flows in the channels of technical microsystems" provided for a scientist
Review of the official opponent on the dissertation of Alukov Sergey Viktorovich "The scientific foundations of inertial stepless gears of increased load ability", submitted for a scientific degree
Ministry of Education and Science of the Russian Federation State Educational Institution of Higher Professional Education Samara State Aerospace University named after academician
Reviewed by the official opponent Pavlenko Alexandra Nikolayevich on the dissertation of Bakanova Maxim Olegovich "Investigation of the dynamics of the thorough formation process during thermal processing of foam cellular charge", presented
D "SPBPU A" ROTEYA O "" and IIII I L 1 !! ^ .1899 ... Millofunuki Russia Federal State Autonomous Educational Institution of Higher Education "St. Petersburg Polytechnic University
Review of the official opponent on the dissertation of Lepichkin Dmitry Igorevich on the topic "Improving Diesel performance in operating conditions with an increase in the stability of the fuel equipment" presented
Review of the official opponent on the dissertation work Kobyakova Yulia Vyacheslavovna on the topic: "Qualitative analysis of the creep of non-woven materials at the stage of organizing their production in order to increase competitiveness,
Tests were carried out by motor bench With the injection engine VAZ-21126. The engine was installed on a brake bench of the MS-VSETIN type, equipped with measuring equipment that allows you to control
Electronic Journal "Technical Acoustics" http://webceter.ru/~eeaa/ejta/ 004, 5 Pskov Polytechnic Institute Russia, 80680, Pskov, ul. L. Tolstoy, 4, e-mail: [Email Protected] About sound speed
Review of the official opponent on the dissertation work of Egorova Marina Avinirovna on the topic: "Development of methods for modeling, forecasting and evaluation operational properties Polymeric textile ropes
In speedspace. This work is actually aimed at creating an industrial package for calculating the flows of sparse gas on the basis of a solution of a kinetic equation with a model integral collision.
Basics of the theory of heat exchange lecture 5 Lecture plan: 1. General concepts of the theory of convective heat exchange. Heatthilling with free movement of fluid in large volume 3. Heat pump with free fluid motion
An implicit method of solving the conjugate tasks of the laminar borderline layer on the plate Plan Occupation: 1 Operation Operation Differential equations of the heat border layer 3 Description of the solved problem 4 solution method
Methods for calculating the temperature condition of the heads of the elements of rocket and space technology during their ground operation # 09, September 2014 Kopytov V.S., Puchkov V. M. Udk: 621.396 Russia, MSTU them.
Stresses and real work of foundations for low-cycle loads, taking into account the prehistory of loading. In accordance with this, the topic of research is relevant. Evaluation of the structure and content of work in
Review of the official opponent of the Doctor of Technical Sciences, Professor Pavlova Pavel Ivanovich on the dissertation work of Kuznetsova Alexei Nikolaevich on the topic: "Development of a system of active noise reduction in
1 Ministry of Education and Science of the Russian Federation Federal State Budgetary Educational Institution of Higher Professional Education "Vladimir State University
In the dissertation council D 212.186.03, FGBOU in Penza State University, a scientist, D.T., Professor Voyacheku I.I. 440026, Penza, ul. Red, 40 reviews of the official opponent Semenova
I argue: First Vice Rector, Vice-Rector for Scientific and Innovative Work of the Federal State Budgetary Educational Academy of Education ^ ^ ^ Sudar University) Igorievich
Discipline control and measuring materials Power units»Questions to test 1. For which the engine is intended, and what types of engines are installed on domestic cars? 2. Classification
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 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
Laboratory work 2 Investigation of heat transfer under forced convection The purpose of the work is experimental determination of the dependence of the heat transfer coefficient from the air velocity in the pipe. Obtained
Lecture. Diffusion border layer. The equations of the theory of the borderline layer in the presence of mass transfer The concept of the boundary layer, considered in paragraph 7. and 9. (for hydrodynamic and thermal border layers
An explicit method for solving the equations of a laminar boundary layer on a plate Laboratory work 1, Plan of classes: 1. The purpose of the work. Methods for solving the equations of the boundary layer (Methodological material) 3. Differential
UDC 621.436 N. D. Chingov, L. L. Milkov, N. S. Malatovsky Methods for calculating the coordinated temperature fields of the cylinder cover with valves A method for calculating the coordinated cylinder cover fields is proposed
# 8, August 6 UDC 533655: 5357 Analytical formulas for calculating heat fluxes on the blocked bodies of small lengthening of wolves MN, student Russia, 55, Moscow, MSTU NE NE Bauman, Aerospace Faculty,
Review of the official opponent on the dissertation of Samoilova Denis Yuryevich "Information and measuring system for the intensification of oil production and determination of waterproof products",
Federal Agency for Education State Educational Institution of Higher Professional Education Pacific State University Thermal Tension Details of DVS Methodical
Review of the official opponent of Doctor of Technical Sciences, Professor Labunda Boris Vasilyevich on the dissertation work Xu Yuna on the topic: "Increase the bearing capacity of compounds of elements of wooden structures
Review of the official opponent Lviv Yuri Nikolayevich on the dissertation of Melnikova Olga Sergeyevna "Diagnostics of the main isolation of force oil-filled electric power transformers on statistical
UDC 536.4 Gorbunov A.D. Dr. tech. Sciences, prof., DGTU Definition of heat transfer coefficient in turbulent flow in pipes and channels Analytical method Analytical calculation of heat transfer coefficient
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.
Significant effect on the cylinder filling provide different kinds supervision. 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.
With the resonant superior group of cylinders with the same flash intervals attach short tubes to resonant receiver, which through resonant pipes It is connected to the atmosphere or with a prefab 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 inlet resonator is set between throttle valve 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 geometry means internal engine volumes - intake and exhaust pipelines, an atrigible volume of the cylinder) using various standard formats files. 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 the work of the DVS - 7200 P.K.V., number of iterations and frequency of preserving 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.
|
|
|
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) on the flow rate in the valve slit it is clear that the maximum consumables It has an upgraded channel with the receiver. Consumption value is higher than 200 g / s. The increase is observed for 60 G.P.K.V.
Since the opening of the intake valve (348 G.K.V.) The flow rate (Fig. 3) begins to grow from 0 to 170 m / s (at the upgraded inlet 210 m / s, with the -190m / s receivers) 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.
|
|
|
|
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.
|
|
|
|
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"
In parallel, the development of the devastating exhaust systems, the systems developed, conventionally referred to as "silencers", but designed not so much to reduce the noise level of the operating engine, how much to change its power characteristics (engine power, or its torque). At the same time, the task of stitching noise went to the second plan, such devices are not reduced, and cannot significantly reduce the exhaust noise of the engine, and often enhance it.
The work of such devices is based on resonant processes within the "silencers" themselves, possessing, like any hollow body with the properties of the gameholts resonator. Due to the internal resonances of the exhaust system, two parallel problems are solved at once: the cleaning of the cylinder is improved from the residues of the combustible mixture in the previous tact, and the filling of the cylinder is a fresh portion of the combustible mixture for the next compression tact.
The improvement in the cleaning of the cylinder is due to the fact that the gas pillar in the graduate manifold, who scored some speed during the output of gases in the previous tact, due to inertia, like a piston in the pump, continues to suck out the remains of the gases from the cylinder even after the cylinder pressure comes With pressure in the graduate manifold. At the same time, another, indirect effect occurs: due to this additional minor pumping, the pressure in the cylinder decreases, which favorably affects the next purge tact - in the cylinder it falls somewhat more than a freshly combustible mixture than could get if the cylinder pressure was equal to atmospheric .
In addition, the reverse wave of exhaust pressure, reflected from the confusion (rear cone of the exhaust system) or blend (gas-dynamic diaphragm) installed in the cavity of the silencer, returning back to the exhaust window of the cylinder at the time of its closure, additionally "rambling" fresh fuel mixture in the cylinder , even more increasing its filling.
Here you need to clearly understand that it is not about the reciprocal movement of gases in the exhaust system, but about the wave oscillatory process within the gas itself. Gas moves only in one direction - from the exhaust window of the cylinder in the direction of the outlet at the outlet of the exhaust system, first with sharp jesters, the frequency of which is equal to the vehicle turnover, then gradually the amplitude of these jolts is reduced, in the limit turning into a uniform laminar movement. And "There and here" the pressure waves are walking, the nature of which is very similar to acoustic waves in the air. And the speed of these vibrations of pressure is close to the speed of sound in the gas, taking into account its properties - primarily density and temperature. Of course, this speed is somewhat different from the known value of the speed of sound in the air, under normal conditions equal to about 330 m / s.
Strictly speaking, the processes flowing in the exhaust systems of DSV is not quite correctly called pure acoustic. Rather, they obey the laws used to describe the shock waves, albeit weak. And this is no longer standard gas and thermodynamics, which is clearly stacked in the framework of isothermal and adiabatic processes described by laws and the equations of Boylya, Mariotta, Klapaireron, and others like them.
I came across this idea a few cases, the witness of which I myself was. The essence of them is as follows: Resonance Dudges of high-speed and racing motors (Avia, Court, and Auto), working on the proceedable modes, in which the engines are sometimes unchecked up to 40,000-45.000 rpm, and even higher, they start "sailing" - they are literally In the eyes change the shape, "pinpoint", as if not made of aluminum, but from plasticine, and even tritely roast! And it happens on the resonant peak of the "twin". But it is known that the temperature of the exhaust gases at the exit of the exhaust window does not exceed 600-650 ° C, while the melting point of pure aluminum is slightly higher - about 660 ° C, and its alloys and more. At the same time (the main thing!), It is more often melted and a non-exhaust tube megaphone is deformed, adjacent directly to the exhaust window, where it would seem the most heat, and the worst temperature conditions, and the cone cone-confusion region, to which exhaust gas It reaches a much smaller temperature, which decreases due to its expansion inside the exhaust system (remember the basic laws of gas dynamics), and besides, this part of the muffler is usually blown by the incident air flow, i.e. Additionally cooled.
For a long time I could not understand and explain this phenomenon. Everything fell into place after I accidentally hit the book in which the processes of shock waves were described. There is such a special section of gas dynamics, the course of which is read only on special taps of some universities that are preparing explosive technicians. Something similar happens (and studied) in aviation, where half a century ago, at the dawn of supersonic flights, they also encountered some inexplicable facts of destruction of the aircraft glider's design at the time of the supersonic transition.
