Modern problems of science and education. Exhaust systems of internal combustion engines Analysis of gas-dynamic processes of the exhaust system of the DVS
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 Efficiency Studies graduation systems. 17
1.3 Settlement studies of the effectiveness of graduation systems 27
1.4 Characteristics of heat exchange processes in the exhaust system of piston internal combustion engine 31
1.5 Conclusions and setting Tasks 37
Chapter 2. Research methodology and description of experimental installation 39
2.1 Choosing a methodology for the study of gas dynamics and heat exchange characteristics of the process of output of the piston engine 39
2.2 Constructive execution of the experimental installation for the study of the process of release in the Piston DVS 46
2.3 Measurement of the angle of rotation and speed distribution Vala 50
2.4 Definition of instant flow 51
2.5 Measurement of instantaneous local heat transfer coefficients 65
2.6 Measurement of overpressure flow in the graduation path 69
2.7 Data Collection System 69
2.8 Conclusions to chapter 2 s
Chapter 3. Gas dynamics and expenditure characteristics of the release process 72
3.1 Gas dynamics and expenditure characteristics of the release process in the piston engine of internal combustion without chance of 72
3.1.1 with a pipeline with a circular cross section 72
3.1.2 For pipeline with square cross section 76
3.1.3 with a pipeline of a triangular cross section 80
3.2 Gas dynamics and consumables for the process of output of the piston internal combustion engine with reducing 84
3.3 Conclusion to Chapter 3 92
Chapter 4. Instant heat transfer in the exhaust channel of the piston engine of internal combustion 94
4.1 Instant local heat transfer process of an internal combustion of an internal combustion engine without supercharow 94
4.1.1 with pipeline with round cross section 94
4.1.2 For pipeline with square cross section 96
4.1.3 with a pipeline with a triangular cross section 98
4.2 Instant heat transfer process of the outlet of the piston engine of internal combustion with reducing 101
4.3 Conclusions to Chapter 4 107
Chapter 5. Stabilization of the flow in the exhaust channel of the piston engine of internal combustion 108
5.1 Changing the flux pulsations in the exhaust channel of the piston engine using a constant and periodic ejection 108
5.1.1 Suppression of flux pulsations in the outlet using a constant ejection 108
5.1.2 Changing the pulsations of flow in the exhaust channel by periodic ejection 112 5.2 Constructive and technological design of the exhaust tract with ejection 117
Conclusion 120.
Bibliography
Estimated studies of the effectiveness of graduation systems
The exhaust system of piston engine is to remove the exhaust gas engine cylinders and supplying them to the turbocharger turbine (in supervising engines) in order to convert the energy left after the workflow mechanical work on the TK tree. The exhaust channels are performed by a shared pipeline, cast from gray or heat-resistant cast iron, or aluminum in the case of cooling, or from separate cast iron nozzles. To protect service personnel from burns exhaust pipeline It can be cooled with water or coated with heat insulating material. The heat-insulated pipelines are more preferable for engines with gas turbine superimposses. Since in this case, the loss of exhaust gas energy is reduced. Since when heated and cooled the length of the exhaust pipeline changes, then special compensators are installed before the turbine. On the large engines The compensators also combine individual sections of exhaust pipelines, which according to technological reasons make composite.
Information about the parameters of the gas before the turbochargeor turbine in the dynamics during each DVS working cycle 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 Engines with gas turbine superior applies a constant pressure boost system before turbine.
The supervision of the impulse converter is intermediate and combines the benefits of pressure pulsations in the exhaust manifold (reducing the poverty operation and improving the cylinder purge) with a winner from reducing pressure ripples before the turbine, which increases the efficiency of the latter.
Figure 3 - Superior system with pulse converter: 1 - nozzle; 2 - nozzles; 3 - camera; 4 - Diffuser; 5 - pipeline
In this case, the exhaust gases on pipes 1 (Figure 3) are summarized through nozzles 2, into one pipeline, which combines the releases from cylinders, the phases of which are not superimposed by one to another. At a certain point in time, the pressure pulse in one of the pipelines reaches a maximum. In this case, the maximum gas expiration rate from the nozzle connected to this pipeline becomes the maximum, which results in the effect of ejection to the resolution in another pipeline and thereby facilitates the purge of cylinders attached to it. The process of expiration of the nozzles is repeated with a high frequency, therefore, in chamber 3, which performs the role of a mixer and a damper, a more or less uniform stream is formed, the kinetic energy of which in the diffuser 4 (speed reduction) is transformed into a potential due to increase in pressure. From the pipeline 5 gases enter the turbine at almost constant pressure. A more complex structural diagram of the pulse converter consisting of special nozzles at the ends of the exhaust pipes, combined by a common diffuser, is shown in Figure 4.
The flow in the exhaust pipeline is characterized by pronounced nonstationarity caused by the frequency of the process itself, and the nonstationarity of gas parameters at the borders of the exhaust pipeline-cylinder and the turbine. Channel rotation, profile breakdown and periodic change of its geometrical characteristics at the input section of the valve slot serve the cause of the separation of the boundary layer and the formation of extensive stagnant zones, the dimensions of which are changed over time. In stagnation zones, a refundable flow with large-scale pulsating vortices, which interact with the main flow in the pipeline and largely determine the flow characteristics of the channels. The nonstationarity of the stream is manifested in the exhaust channel and under stationary boundary conditions (with a fixed valve) as a result of ripples of congestion zones. The dimensions of non-stationary vortices and the frequency of their ripples can significantly determine only by experimental methods.
The complexity of experimental study of the structure of non-stationary vortex flows forces designers and researchers to use when choosing the optimal geometry of the exhaust channel by comparing the integral consumables and energy characteristics of the flow, usually obtained under stationary conditions on physical models, that is, with static purge. However, the substantiation of the reliability of such studies is not given.
The paper presents the experimental results of studying the stream structure in the exhaust channel of the engine and carried out comparative analysis structures and integral characteristics of streams under stationary and nonstationary conditions.
The test results of a large number of output variants indicate the insufficient effectiveness of the usual approach to profiling based on the perpetrators of the stationary flow in the knees of pipes and short pipes. There are no discrepancy cases of predicted and valid dependencies consumables from channel geometry.
Measurement of the angle of rotation and frequency of rotation of the camshaft
It should be noted that the maximum differences between the values \u200b\u200bof the TPs defined in the center of the channel and near its wall (the variation on the radius of the channel) are observed in control sections close to the input to the channel under study and reach 10.0% of the IPI. Thus, if the forced gas flow pulsations for 1x to 150 mm were with a period of a lot less than the IPI \u003d 115 ms, the current should be characterized as the current high degree Nonstationarity. This suggests that the transitional flow regime in the channels of the energy installation has not yet been completed, and the next indignation has already affected. And on the contrary, if the pulsations of the flow would be much more with a period than TR, the current should be considered a quasistationary (with a low degree of nonstationary). In this case, before the occurrence of the perturbation, the transitional hydrodynamic mode has time to complete, and the course to be aligned. And finally, if the flow rate of flow was close to the value of TR, the current should be characterized as moderately non-stationary with an increasing degree of nonstationary.
As an example of the possible use of characteristic times proposed to assess the characteristic times, the flow of gas in graduation channels piston DVS. First, refer to Figure 17, at which the dependences of the WX flow rate from the angle of rotation of the crankshaft F (Figure 17, a) and on the time T (Figure 17, b). These dependences were obtained on the physical model of the same-cylinder DVS dimension 8.2 / 7.1. From the figure, it can be seen that the representation of the dependence WX \u003d F (φ) is a little-informative, since it does not accurately reflect the physical essence of the processes occurring in the graduation channel. However, it is precisely in this form that these graphics are taken to submit in the field of engine field. In our opinion, it is more correct to use temporal dependences WX \u003d / (T) to analyze.
We analyze the dependence WX \u003d / (T) for n \u003d 1500 min. "1 (Figure 18). As can be seen, at this crankshaft rotation frequency, the length of the entire release process is 27.1 ms. The transitional hydrodynamic process in the outlet begins after opening the exhaust valve. At the same time, the most dynamic area of \u200b\u200bthe lift can be distinguished (the time interval during which there is a sharp increase in flow rate), the duration of which is 6.3 ms. After that, the growth of the flow rate is replaced by its recess. As shown earlier (Figure 15), for this The configuration of the hydraulic system relaxation time is 115-120 ms, i.e. significantly larger than the duration of the lifting section. Thus, it should be assumed that the beginning of the release (lifting section) occurs with a high degree of nonstationary. 540 Ф, HRAD PKV 7 A)
The gas was supplied from the total network on the pipeline, on which the pressure gauge 1 was installed to control the pressure on the network and the valve 2, to control the flow. The gas flowed into the tank receiver 3 with a volume of 0.04 m3, it contained an alignment grille 4 to quench pressure pulsations. From the tank-receiver 3, the gas pipeline was supplied to the cylinder-blowing chamber 5, in which Honeycomb 6 was installed. Honaycomb was a thin grille, and was intended to clean residual pressure ripples. The cylinder-blowing chamber 5 was attached to the cylinder block 8, while the inner cavity of the cylinder-cell chamber was combined with the inner cavity of the head of the cylinder block.
After opening the exhaust valve 7, the gas from the simulation chamber went through the exhaust channel 9 to the measuring channel 10.
Figure 20 shows in more detail the configuration of the exhaust path of the experimental installation, indicating the locations of the pressure sensors and the thermoemometer probes.
Due limited quantity Information on the dynamics of the release process as the original geometric base was chosen a classic direct outlet channel with a circular cross section: an experimental exhaust pipe was attached to the head of the cylinder block 2, the pipe length was 400 mm, and a diameter of 30 mm. In the pipe, three holes were drilled at distances L \\, lg and b, respectively, 20,140 and 340 mm for the installation of pressure sensors 5 and thermo-chaser sensors 6 (Figure 20).
Figure 20 - configuration of the exhaust channel of the experimental installation and location of the sensor: 1 - cylinder - blowing chamber; 2 - the head of the cylinder block; 3 - exhaust valve; 4 - an experimental graduation tube; 5 - pressure sensors; 6 - thermoemometer sensors for measuring the flow rate; L is the length of the outlet pipe; C_3- Diases to the locations of the thermo-chaser sensors from the exhaust window
The installation measurement system made it possible to determine: the current corner of the rotation and the rotational speed of the crankshaft, the instantaneous flow rate, the instantaneous heat transfer coefficient, excess flow pressure. Methods for defining these parameters are described below. 2.3 Measurement of the corner of rotation and frequency of rotation of the distribution
To determine the speed of rotation and the current angle of rotation of the camshaft, as well as the moment of finding the piston in the upper and lower dead points, a tachometric sensor was applied, the installation scheme, which is shown in Figure 21, since the parameters listed above must be unambiguously determined in the study of dynamic processes in ICC . four
The tachometric sensor consisted of a toothed disk 7, which had only two teeth located opposite each other. The disk 1 was installed with an electric motor 4 so that one of the discs of the disk corresponded to the position of the piston in the upper dead point, and the other, respectively, the bottom dead point and was attached to the shaft using the coupling 3. The motor shaft and the piston engine shaft were connected by the belt transmission.
When passing one of the teeth near the inductive sensor 4, fixed on the tripod 5, the output of the inductive sensor is formed a voltage pulse. Using these pulses, you can determine the current position of the camshaft and, accordingly, determine the position of the piston. In order for the signals corresponding to NMT and NMT, the teeth were performed from each other from each other, the configuration is different from each other, due to which the signals at the outlet of the inductive sensor had different amplitudes. The signal obtained at the outlet from the inductive sensor is shown in Figure 22: the voltage pulse of a smaller amplitude corresponds to the position of the piston in the NTC, and the pulse of a higher amplitude, respectively, position in NMT.
Gas dynamics and consumables process of the output of the piston internal combustion engine with a superposition
In classical literature on the theory of workflow and engineering, the turbocharger is mainly considered as the most effective method of engine forcing, due to an increase in the amount of air entering the engine cylinders.
It should be noted that in literary sources, the influence of the turbocharger on the gas-dynamic and thermophysical characteristics of the gas flow of the exhaust pipeline is extremely rare. Mainly in the literature, the turbine turbine turbine is considered with simplifications, as an element of a gas exchange system, which has hydraulic resistance to the flow of gases at the outlet of the cylinders. However, it is obvious that the turbocharger turbine plays an important role in the formation of the flow of exhaust gases and has a significant impact on the hydrodynamic and thermophysical characteristics of the flow. This section discusses the results of the study of the effect of the turbocharger turbine on the hydrodynamic and thermophysical characteristics of the gas flow in the exhaust pipeline of the piston engine.
Studies were carried out on an experimental setup, which was previously described, in the second chapter, the main change is the installation of a TKR-6 turbocharger with a radial-axial turbine (Figures 47 and 48).
Due to the influence of the pressure of the exhaust gases in the exhaust pipeline to the workflow of the turbine, the patterns of changes in this indicator are widely studied. Compressed
The turbine turbine installation in the exhaust pipeline has a strong effect on the pressure and flow rate in the exhaust pipeline, which is clearly seen from the plugness of the pressure and the flow rate in the exhaust pipe with the turbocharger from the corner of the crankshaft (Figures 49 and 50). Comparing these dependencies with similar dependencies for the exhaust pipeline without a turbocharger under similar conditions, it can be seen that the installation of a turbocharger turbine into the exhaust pipe leads to the emergence of a large number of ripples throughout the entire output of the output caused by the action of the blade elements (nozzle apparatus and impeller) of the turbine. Figure 48 - General type of installation with turbocharger
One more characteristic feature These dependencies is a significant increase in the amplitude of pressure fluctuations and a significant reduction in the amplitude of the speed fluctuation in comparison with the execution of the exhaust system without a turbocharger. For example, at with the rotation frequency of the crankshaft of 1500 minutes, the maximum gas pressure in the pipeline with a turbocharger is 2 times higher, and the speed is 4.5 times lower than in the pipeline without a turbocharger. Increased pressure and Reducing the speed in the graduation pipeline is caused by the resistance created by the turbine. It is worth noting that the maximum pressure value in the turbocharger pipeline is shifted relative to the maximum pressure value in the pipeline without a turbocharger by up to 50 degrees of the rotation of the crankshaft. SO
The dependences of the local (1x \u003d 140 mm) excess pressure of the PC and the flow rate of the WX in the exhaust pipeline of the circular cross-section of the piston engine with a turbocharger from the angle of rotation of the crankshaft p at an overpressure of the release of the P t \u003d 100 kPa for different crankshaft speeds:
It was found that in the exhaust pipeline with a turbocharger, the maximum flow rate values \u200b\u200bare lower than in the pipeline without it. It is worth noting that at the same time the moment of achieving the maximum flow rate value towards an increase in the corner of the crankshaft turn is characteristic of all installation modes. In the case of turbocharger, the rate of speed is most pronounced at low speeds of rotation of the crankshaft, which is also characteristic and in the case without a turbocharger.
Similar features are characteristic and for dependence Px \u003d / (P).
It should be noted that after closing the exhaust valve, the gas speed in the pipeline in all modes is not reduced to zero. Installing the turbocharger turbine in the exhaust pipeline leads to the smoothing of the flow rate pulsations on all modes of operation (especially with the initial overpressure of 100 kPa), both during the output tact and after its end.
It is worth noting that in the pipeline with a turbocharger, the intensity of the attenuation of the fluctuations of the flow pressure after the exhaust valve is closed higher than without a turbocharger
It should be assumed that the changes described above the changes in the gas-dynamic characteristics of the flow when the turbocharger is installed in the exhaust pipeline, the flow of flow in the outlet canal, which inevitably should lead to changes in the thermophysical characteristics of the release process.
In general, the dependence of the pressure change in the pipeline in DVS with the superior is consistent with the previously obtained.
Figure 53 shows dependence graphs mass flow G through the exhaust pipeline from the speed of rotation of the crankshaft under the various values \u200b\u200bof the redundant pressure of the P and the configurations of the exhaust system (with the turbocharger and without it). These graphics were obtained using the technique described in.
From the graphs shown in Figure 53, it can be seen that for all values \u200b\u200bof the initial overpressure, the mass flow rate G of gas in the exhaust pipeline is about the same as if there is a TK and without it.
In some modes of operation of the installation, the difference of the expenditure characteristics slightly exceeds a systematic error, which is about 8-10% to determine the mass flow rate. 0.0145 g. kg / s
For pipeline with square cross section
The exhaust system with ejection functions as follows. The exhaust gases into the exhaust system come from the engine cylinder into the channel in the cylinder head 7, from where they pass to the exhaust manifold 2. In the exhaust manifold 2, an ejection tube 4 is installed in which air is supplied via an electropneumoclap 5. Such an execution allows you to create a discharge area immediately behind the channel Cylinder head.
In order for the ejection tube does not create significant hydraulic resistance in the exhaust manifold, its diameter should not exceed 1/10 diameter of this collector. It is also necessary in order to create a critical mode in the exhaust manifold, and the ejector locking appears. The position of the ejection tube axis relative to the exhaust collector axis (eccentricity) is selected depending on the specific configuration of the exhaust system and the engine operation mode. In this case, the effectiveness criterion is the degree of purification of the cylinder from the exhaust gases.
Search experiments showed that the discharge (static pressure) created in the exhaust manifold 2 using the ejection tube 4 should be at least 5 kPa. Otherwise, insufficient leveling of the pulsating flow will occur. This can cause the formation of feed currents in the channel, which will lead to a decrease in the efficiency of the cylinder purge, and, accordingly, reduce the power of the engine. The electronic motor control unit 6 must organize the operation of the electropneumoclap 5, depending on the rotational speed of the engine crankshaft. To enhance the effect of ejection at the output end of the ejection tube 4, a subsonic nozzle may be installed.
It turned out that the maximum values \u200b\u200bof the flow rate in the outlet canal with constant ejection is significantly higher than without it (up to 35%). In addition, after closing the exhaust valve in the exhaust channel with a constant ejection, the speed of the output flow drops slower compared to the traditional channel, which indicates the continuing cleaning of the channel from the exhaust gases.
Figure 63 shows the dependences of the local 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 can be feasible by setting. electronic block Motor control, or applying a special control unit, the diagram of which is shown in Figure 66.
This scheme developed by the author (Figure 64) is applied if it is impossible to ensure the control of the ejection process using the engine control unit. The principle of operation of such a scheme consists in the following, special magnets should be installed on the engine flywheel, special magnets must be installed, the position of which would correspond to the moments of opening and closing the engine outlet valves. Magnets must be installed in different poles relative to the Hall bipolar sensor, which in turn should be in the immediate vicinity of magnets. Passing next to the sensor Magnet, set by respectively the point of opening of the exhaust valves, causes a small electrical pulse, which is enhanced by the signal amplification unit 5, and is fed to the electropneumoclap, the conclusions of which are connected to the outputs 2 and 4 of the control unit, after which it opens and air supply begins . It happens when the second magnet runs next to the sensor 7, after which the electropneumoclap closes.
We turn to experimental data that were obtained in the range of rotation frequencies of the crankshaft P from 600 to 3000 minutes. 1 with different permanent overpressure pins on the release (from 0.5 to 200 kPa). In experiments, compressed air with a temperature of 22-24 with The ejection tube received from the factory highway. Deflection (static pressure) for the ejection tube in the exhaust system was 5 kPa.
Figure 65 shows the graphs of the local pressure dependences Px (y \u003d 140 mm) and the WX flow rate in the exhaust pipeline of the round transverse section of the piston engine with a periodic ejection from the angle of rotation of the crankshaft r under the excess pressure of the № \u003d 100 kPa for various rotation frequencies of the crankshaft .
From these graphs, it can be seen that throughout the entire tact of release there is a oscillation of absolute pressure in the graduation path, the maximum values \u200b\u200bof pressure oscillations reach 15 kPa, and the minimum reaches the discharge of 9 kPa. Then, as in the classic graduation path of the circular cross section, these indicators are respectively 13.5 kPa and 5 kPa. It is worth noting that the maximum pressure value is observed at the speed of the crankshaft of 1500 min. "1, on the other modes of operation of the pressure oscillation engine do not reach such values. Recall. That in the initial pipe of the round cross section, the monotonous increase in the amplitude of pressure fluctuations was observed depending on the increase The rotation frequency of the crankshaft.
From the charts of the local gas flow rate of the gas flow from the corner of the crankshaft rotation, it can be seen that local speeds during the release tact in the channel using the effect of periodic ejection is higher than in the classic channel of the circular cross section on all modes of the engine. This indicates the best cleaning of the graduation channel.
Figure 66, graphs of comparing the dependences of the volumetric flow rate of the gas from the rotational speed of the crankshaft in the round cross section of without ejection and the round cross section with a periodic ejection at various overpressure at the inlet input canal are considered.
UDC 621.436
Effect of aerodynamic resistance of intake and exhaust systems of automotive engines on gas exchange processes
L.V. Carpenters, bp Zhilkin, Yu.M. Brodov, N.I. Grigoriev
The paper presents the results of an experimental study of the influence of the aerodynamic resistance of intake and exhaust systems piston engines on gas exchange processes. The experiments were carried out on the on-line models of single-cylinder engine. Installations and methods for conducting experiments are described. The dependences of the change in the instantaneous speed and pressure of the flow in the gas-air paths of the engine from the corner of the crankshaft rotation are presented. The data was obtained at various coefficients of resistance of intake and exhaust systems and different frequencies of rotation of the crankshaft. Based on the data obtained, conclusions were made of the dynamic features of gas exchange processes in the engine at different conditions. It is shown that the use of the noise muffler smoothes the flow ripple and changes the flow characteristics.
Keywords: piston engine, gas exchange processes, process dynamics, speed pulsation and flow pressure, noise muffler.
Introduction
A number of requirements are made to intake and outcomes of piston engines of internal combustion, among which the main decrease in aerodynamic noise and minimal aerodynamic resistance are the main. Both of these indicators are determined in the interconnection of the design of the filter element, inlet silencers and the release, catalytic neutralizers, the presence of a superior (compressor and / or turbocharger), as well as the configuration of intake and exhaust pipelines and the nature of the flow in them. At the same time, there are practically no data on the influence of additional elements of intake and exhaust systems (filters, silencers, turbocharger) on gas dynamics in them.
This article presents the results of a study of the effect of the aerodynamic resistance of intake and exhaust systems on gas exchange processes in relation to the piston engine of dimension 8.2 / 7.1.
Experimental plants
and data collection system
Studies of the effect of aerodynamic resistance of gas-air systems on gas exchange processes in piston engineers were carried out on the simulation model of the dimension 4.2 / 7.1, driven by rotation asynchronous engineThe frequency of rotation of the crankshaft of which was adjusted in the range n \u003d 600-3000 min1 with an accuracy of ± 0.1%. An experimental installation is described in more detail.
In fig. 1 and 2 show the configurations and geometric sizes of the intake and exhaust path of the experimental installation, as well as the installation location for the measurement of instantaneous
the values \u200b\u200bof the average speed and pressure of the flow of air.
For measurements of instant pressure values \u200b\u200bin the stream (static) in the PC channel, the pressure sensor £ -10 was used by Wika, the speed of which is less than 1 ms. The maximum relative average mean-square pressure measurement error was ± 0.25%.
To determine the instantaneous medium in the section of the air flow channel, the thermoenemometers of the constant temperature of the original design, the sensitive element of which was the nichrome thread with a diameter of 5 μm and a length of 5 mm. The maximum relative average mean-of-mean error of measuring the speed WX was ± 2.9%.
The measurement of the rotation frequency of the crankshaft was carried out using a tachometric meter consisting of a toothed disk fixed on the crankshaft shaft and an inductive sensor. The sensor formed a voltage pulse at a frequency proportional to the rotation speed of the shaft. According to these pulses, the frequency of rotation was recorded, the position of the crankshaft (angle f) was determined and the moment of passing the piston of VMT and NMT.
Signals from all sensors entered an analog-to-digital converter and transmitted to a personal computer for further processing.
Before conducting experiments, a static and dynamic targeting of the measuring system as a whole was carried out, which showed the speed required for the study of the dynamics gas-dynamic processes In the inlet and exhaust systems of piston engines. The total average mean-of-mean error of experiments on the effect of the aerodynamic resistance of gas-air systems of DVS. Gas exchange processes were ± 3.4%.
Fig. 1. Configuration and geometric sizes of the intake path of the experimental installation: 1 - cylinder head; 2-bubbling pipe; 3 - measuring tube; 4 - thermoanemometer sensors for measuring air flow rate; 5 - Pressure Sensors
Fig. 2. Configuration and geometric dimensions of the exhaust path of the experimental installation: 1 - cylinder head; 2 - working plot - graduation pipe; 3 - pressure sensors; 4 - thermoemometer sensors
The effect of additional elements on the gas dynamics of intake and release processes was studied with different system resistance coefficients. Resistance was created using various intake filters and release. So, as one of them, a standard air automobile filter was used with a resistance coefficient of 7.5. A tissue filter with a resistance coefficient 32 was chosen as another filter element. The resistance coefficient was determined experimentally through static purge in laboratory conditions. Studies were also conducted without filters.
Effect of aerodynamic resistance on the inlet process
In fig. 3 and 4 show the dependences of the air flow rate and PC pressure in the inlet can
le from the angle of rotation of the crankshaft f at different of its rotation frequencies and when using various intake filters.
It has been established that in both cases (with a silencer and without) pulsation of pressure and air flow rates are most expressed at high speed of rotation of the crankshaft. At the same time in the intake canal with the silencer of noise maximum speed Air flow, as it should be expected, less than in the channel without it. Most
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Fig. 3. The dependence of the air velocity WX in the intake channel from the angle of rotation of the crankshaft shaft at different frequencies of the rotation of the crankshaft and different filtering elements: a - n \u003d 1500 min-1; B - 3000 min-1. 1 - without a filter; 2 - standard air filter; 3 - fabric filter
Fig. 4. The dependence of the PC pressure in the inlet channel from the angle of rotation of the crankshaft f at different frequencies of rotation of the crankshaft and different filtering elements: a - n \u003d 1500 min-1; B - 3000 min-1. 1 - without a filter; 2 - standard air filter; 3 - fabric filter
it was brightly manifested with high frequencies of rotation of the crankshaft.
After closing the intake valve, the pressure and speed of the air flow in the channel under all conditions do not become equal to zero, and some of their fluctuations are observed (see Fig. 3 and 4), which is also characteristic of the release process (see below). At the same time, the installation of the inlet noise muffler leads to a decrease in pressure pulsations and air flow rates under all conditions both during the intake process and after the intake valve is closed.
Effect of aerodynamic
resistance to the release process
In fig. 5 and 6 shows the dependences of the air flow rate of the WX and the pressure PC in the outlet from the angle of rotation of the crankshaft form at different rotational frequencies and when using various release filters.
The studies were carried out for various frequencies of rotation of the crankshaft (from 600 to 3000 min1) at different overpressure on the release of PI (from 0.5 to 2.0 bar) without a silent noise and if it is presented.
It has been established that in both cases (with the silencer and without) pulsation of the air flow rate, the most brightly manifested at low frequencies of the crankshaft rotation. In this case, the values \u200b\u200bof the maximum air flow rate remain in the exhaust channel with the noise silencer
merilly the same as without it. After closing the exhaust valve, the air flow rate in the channel under all conditions does not become zero, and some speed fluctuations are observed (see Fig. 5), which is characteristic of the inlet process (see above). At the same time, the installation of the noise muffler on the release leads to a significant increase in the pulsations of the air flow rate under all conditions (especially at ry \u003d 2.0 bar) both during the release process and after the exhaust valve is closed.
It should be noted the opposite effect of aerodynamic resistance on the characteristics of the inlet process in the engine, where air filter Pulsation effects in the intake process and after closing the inlet valve were present, but they were clearly faster than without it. In this case, the presence of a filter in the inlet system led to a decrease in the maximum air flow rate and weakening the dynamics of the process, which is consistent well with previously obtained results in the work.
An increase in the aerodynamic resistance of the exhaust system leads to a certain increase in the maximum pressures in the process of release, as well as the displacement of peaks for NMT. In this case, it can be noted that the installation of the silencer of the noise of the output leads to a decrease in the pulsations of the pressure of the air flow under all conditions both during the production process and after the exhaust valve is closed.
hY. m / s 118 100 46 16
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Opening of ipical |<лапана ^ 1 1 А ікТКГ- ~/М" ^ 1
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540 (P, Grab, P.K.Y. 720 NMT NMT
Fig. 5. The dependence of the air velocity WX in the outlet from the angle of rotation of the crankshaft shaft at different frequencies of the rotation of the crankshaft and different filtering elements: a - n \u003d 1500 min-1; B - 3000 min-1. 1 - without a filter; 2 - standard air filter; 3 - fabric filter
Px. 5pr 0,150
1 1 1 1 1 1 1 1 1 II 1 1 1 II 1 1 L "A 11 1 1 / \\ 1. ', and II 1 1
Opening | Yypzskskaya 1 Іклапана Л7 1 h І _ / 7 / ", g s 1 \\ h Closing of the Bittseast G / CGTї Alan -
c- "1 1 1 1 1 І 1 l l _Л / І І h / 1 1
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Fig. 6. The dependence of the pressure PC in the outlet from the angle of rotation of the crankshaft f at different frequencies of rotation of the crankshaft and different filtering elements: a - n \u003d 1500 min-1; B - 3000 min-1. 1 - without a filter; 2 - standard air filter; 3 - fabric filter
Based on the processing of dependency changes in the flow rate for separate tact, a relative change in the volume flow of air q was calculated through the exhaust channel when the muffler is placed. It has been established that with low overpressure on the release (0.1 MPa), the consumption q in the exhaust system with a silencer is less than in the system without it. At the same time, if at the frequency of rotation of the crankshaft 600 min-1, this difference was approximately 1.5% (which lies within the error), then with n \u003d 3000 min4 this difference reached 23%. It is shown that for high overpressure of 0.2 MPa, the opposite tendency was observed. The volume flow of air through the exhaust channel with the silencer was greater than in the system without it. At the same time, at low frequencies of rotation of the crankshaft, this exceeded was 20%, and with n \u003d 3000 min1 - 5%. According to the authors, such an effect can be explained by some smoothing of the pulsations of the air flow rate in the exhaust system in the presence of a silent noise.
Conclusion
The conducted study showed that the inlet engine of internal combustion is significantly influenced by the aerodynamic resistance of the intake path:
The increase in the resistance of the filter element smoothes the dynamics of the filling process, but at the same time reduces air flow rate, which corresponds to the filling coefficient;
The effect of the filter is enhanced with the increasing rotation frequency of the crankshaft;
The threshold value of the filter resistance coefficient (approximately 50-55), after which its value does not affect the flow rate.
It has been shown that the aerodynamic resistance of the exhaust system also significantly affects the gas-dynamic and consumables of the release process:
Increasing the hydraulic resistance of the exhaust system in the piston DVS leads to an increase in the pulsations of the air flow rate in the exhaust channel;
With low overpressure on the release in the system with a silent noise, there is a decrease in volumetric flow through the exhaust channel, while at high ry - on the contrary, it increases compared to the exhaust system without a silencer.
Thus, the results obtained can be used in engineering practice in order to optimally choose the characteristics of the inlet and outbuilding silencers, which can provide
the influence on the filling of the cylinder of the fresh charge (filling coefficient) and the quality of the cleaning of the engine cylinder from the exhaust gases (the residual gas coefficient) on certain high-speed modes of the work of the piston engine.
Literature
1. Draganov, B.H. Construction of intake and exhaust channels of internal combustion engines / B.Kh. Draganov, MG Kruglov, V. S. Obukhov. - Kiev: Visit School. Head ed, 1987. -175 p.
2. Internal combustion engines. In 3 kN. Kn. 1: Theory of workflows: studies. / V.N. Lou-Kanin, K.A. Morozov, A.S. Khachyan et al.; Ed. V.N. Lukanina. - M.: Higher. Shk., 1995. - 368 p.
3. Champraozs, B.A. Internal combustion engines: theory, modeling and calculation of processes: studies. In the course "Theory of workflows and modeling of processes in internal combustion engines" / B.A. Chamolaoz, M.F. Faraplatov, V.V. Clementev; Ed. Castle Deat. Science of the Russian Federation B.A. Champrazov. - Chelyabinsk: SUURSU, 2010. -382 p.
4. Modern approaches to the creation of diesel engines for passenger cars and small-calm
zovikov /a. Blinov, P.A. Golubev, Yu.E. Dragan et al.; Ed. V. S. Peponova and A. M. Mineyev. - M.: NIC "Engineer", 2000. - 332 p.
5. Experimental study of gas-dynamic processes in the inlet system of piston engine / b.p. Zhokkin, L.V. Carpenters, S.A. Korzh, I.D. Larionov // Engineering. - 2009. -№ 1. - P. 24-27.
6. On the change in gas dynamics of the process of release in piston engine in the installation of the muffler / L.V. Carpenters, bp Zhokkin, A.V. Cross, D.L. Padalak // Bulletin of the Academy of Military Sciences. -2011. - № 2. - P. 267-270.
7. Pat. 81338 RU, MPK G01 P5 / 12. Thermal mechanical temperature of constant temperature / S.N. Pochov, L.V. Carpenters, bp Vilkin. - No. 2008135775/22; Stage. 09/03/2008; publ. 03/10/2009, Bul. № 7.
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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 narrow places in the theory of DVS. In this regard, the creation of reliable, experimentally substantiated calculation methods for the study of local convective heat exchange in GVK, which makes it possible to obtain reliable estimates of the temperature and heat-stressed state of DVS parts, is an urgent problem. Its 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. For the first time, a mathematical model was used, rationally combining one-dimensional representation of gas-dynamic processes in the intake and exhaust system of the engine with a three-dimensional representation of gas flow in GVK to calculate the parameters of local heat exchange. 2. The methodological basis for the design and finishing of the gasoline engine is developed by upgrading and clarifying methods for calculating local thermal loads and the thermal state of the elements of the cylinder head. 3. New calculated and experimental data on the spatial gas flows in the inlet and exhaust channels of the engine and the three-dimensional temperature distribution in the body of the head of the gasoline engine cylinders are obtained. The reliability of the results is ensured by the application of approved methods of calculating analysis and experimental studies, common systems of equations reflecting the fundamental laws of energy conservation, mass, pulse with appropriate initial and boundary conditions, modern numerical methods for implementing mathematical models, the use of guests and other regulatory acts corresponding to the graduation of measuring elements 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. The general aspects of the application of one-dimensional mathematical models by the method of characteristics (closed working body) are considered and some results of the calculation of the change in gas flow parameters in cylinders and in inlet and outcomes of single and multi-cylinder engines are considered. 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 booth with a car engine VAZ of the cylinder head preparation performed 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. - - -B- rice. 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. Calculation and experimental study of the temperature of the engine cylinder block // Engineering: Scientific and technical collection, tested by the 100th anniversary of the Honored Worker of Science and Technology of the Russian Federation Professor N.Kh. Dyachenko // P. ed. L. E. Magidovich. St. Petersburg: Publishing House of Polytechnic Un-Ta, from Shabanov A.Yu., Zaitsev A.B., Mashkir M.A. A new method for calculating the boundary conditions of thermal loading of the head of the cylinder block of the piston engine // Engineering, N5 2004, 12 s. 5. Shabanov A.Yu., Makhmud Mashkir A. The use of the method of finite elements in determining the boundary conditions of the thermal state of the cylinder head // XXXIII Science Week of SPbGPU: Materials of the Inter-University Scientific Conference. SPb.: Publishing House of Polytechnic University, 2004, with Mashkir Mahmud A., Shabanov A.Yu. The use of the method of characteristics to the study of gas parameters in gas-air channels of DVS. XXXI SPBGPU Science Week. Part II. Materials of the Interuniversity Scientific Conference. SPB: Publishing House of SPbGPU, 2003, with
18 The work was carried out at the State Educational Institution of Higher Professional Education "St. Petersburg State Polytechnic University", at the Department of Internal Combustion Engines. Scientific leader - Candidate of Technical Sciences, Associate Professor Shabanov Aleksandr Yuryevich Official opponents - Doctor of Technical Sciences, Professor Erofeev Valentin Leonidovich Candidate of Technical Sciences, Associate Professor Kuznetsov Dmitry Borisovich Leading organization - GUP "Tsnidi" Protection will be held in 2005 at the meeting of the dissertation council The state educational institution of higher professional education "St. Petersburg State Polytechnic University" at the address :, St. Petersburg, ul. Polytechnic 29, Main Building, Aud .. The dissertation can be found in the Fundamental Library of GOU "SPbGPU". Abstract of the Dissertation Council Scientific Secretary of the Dissertation Council, Doctor of Technical Sciences, Associate Professor Khrustalev B.S.
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The use of resonant exhaust pipes on 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.
