Gas dynamics of resonant exhaust pipes. Mashkur Mahmoud a. Mathematical model of gas dynamics and heat exchange processes in intake and exhaust systems of the engine GAZ Dynamar processes in the exhaust tract of ship

This 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. Dydykin A. M., Zholobov L. A. Gazodynamic dVS studies Methods of numerical simulation // Tractors and agricultural machines. 2008. № 4. P. 29-31.

3. Pritr D. M., Turkish V. A. Aeromechanics. M.: Oborongiz, 1960.

4. Heilov M. A. Calculated pressure fluctuation equation in the absorbing pipe engine internal combustion // 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. To the issue of the development of mathematical and software Calculation of gas-dynamic processes in DVS: materials of the IX International Scientific and Practical Conference. Vladimir, 2003. P. 213-216.

The magnitude of the torque of the engine is proportional to the mass of air, attributed to the frequency of rotation. Increasing the filling of the cylinder of gasoline engine, by upgrading the intake path, will lead to an increase in the pressure of the end of the intake, improved mixing formation, an increase in the technical and economic indicators of the engine operation and a decrease in the toxicity of exhaust gases.

The basic requirements for the inlet path are to ensure minimal resistance to the inlet and the uniform distribution of the combustible mixture through the engine cylinders.

Ensuring the minimum resistance to the inlet can be achieved by eliminating the roughness of the inner walls of pipelines, as well as sharp changes in the flow direction and eliminate sudden narrowings and extensions of the tract.

A significant effect on the filling of the cylinder provides various types of boost. The simplest type of superior is to use the dynamics of the incoming air. A large volume of the receiver partially creates resonant effects in a specific rotational speed range, which lead to improved filling. However, they have, as a result, dynamic disadvantages, for example, deviations in the composition of the mixture with a rapid change in the load. Almost the ideal torque flow ensures that the inlet tube is switching, in which, for example, depending on the engine load, the rotational speed and position of the throttle are possible variations:

The length of the pulsation pipe;

Switch between pulsation pipes of different lengths or diameter;
- selective shutdown of a separate pipe of one cylinder in the presence of a large amount of them;
- Switching the volume of the receiver.

In the resonant superior of the cylinder group with the same flagel interval attach short pipes to resonant receiver, which are connected through the resonant pipes with the atmosphere or with the collection receiver acting as a gölmgolts resonator. It is a spherical vessel with an open neck. The air in the neck is the oscillating mass, and the volume of air in the vessel plays the role of an elastic element. Of course, such separation is true only approximately, since some of the air in the cavity has inertial resistance. However, with a sufficiently large value of the area of \u200b\u200bthe opening to the area of \u200b\u200bthe cross section of the cavity, the accuracy of such an approximation is quite satisfactory. The main part of the kinetic oscillation energy is concentrated in the neck of the resonator, where the oscillatory velocity of air particles has the greatest value.

The intake resonator is established between the throttle and cylinder. It begins to act when the throttle is covered enough so that its hydraulic resistance becomes comparable to the resistance of the resonator channel. When the piston moves down, the combustible mixture enters the engine cylinder not only from under the throttle, but also from the tank. With a decrease in the vacuum, the resonator begins to suck the combustible mixture. This will follow the same part, and quite large, reverse ejection.
The article analyzes the flow movement in the intake channel of 4-stroke gasoline engine at the rated crankshaft rotation frequency on the example of the VAZ-2108 engine at the rotational speed of the crankshaft N \u003d 5600min-1.

This research task was solved by the mathematical way using the software package for modeling gas-hydraulic processes. Simulation was carried out using the FlowVision software package. For this purpose, geometry was obtained and imported (under 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 set mathematical model (a set of laws of changes in the physical parameters of gas for this task).

In this case, a substantially subsonic flow of gas is taken at small Reynolds numbers, which is described by the model of the turbulent flow of fully compressible gas using standard K-E Turbulence models. 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 maximum speed in it.

Before starting to calculate the created option, you must specify the parameters of numerical modeling. At the same time, the time to continue the calculation is equal to one full cycle of operation of the engine, 7200 PK., The number of iterations and the frequency of saving these calculation options. For subsequent processing, certain stages of calculation are preserved. Set the time and options for the calculation process. This task requires a time step setting - a method of choice: an implicit scheme with a maximum step 5E-004C, explicit number of CFL - 1. This means that the time step determines the program itself, depending on the convergence of the pressure equations itself.

The postprocessor is configured and the parameters of the visualization of the results are interested in. Simulation allows you to obtain the required layers of visualization after the completion of the main calculation, based on the calculation stages remained with a certain frequency. In addition, the postprocessor allows you to transmit the resulting numeric values \u200b\u200bof the parameters of the process under study in the form of an information file into external electronic table editors and to obtain the time dependence of such parameters as speed, consumption, pressure, etc.

Figure 1 shows the installation of the receiver on the inlet channel of the DVS. The volume of the receiver is equal to the volume of one engine cylinder. The receiver is set as close as possible to the inlet channel.

The own frequency of the Helmholtz resonator is:

(12)

where F is the frequency, Hz; C0 - sound speed in the air (340 m / s); S - hole cross section, m2; L is the length of the pipe, m; V is the volume of the resonator, M3.

For our example, we have the following values:

d \u003d 0.032 m, s \u003d 0.00080384 m2, v \u003d 0.000422267 m3, L \u003d 0.04 m.

After calculating F \u003d 374 Hz, which corresponds to the rotational speed of the crankshaft N \u003d 5600min-1.

After setting the calculated option and, after setting the parameters of numerical simulation, the following data were obtained: flow rate, speed, density, pressure, gas flow temperature in the inlet channel of the intensity of the Crankshaft rotation.

From the graph presented (Fig. 2), in terms of flow flow in the valve slit, it is clear that the upgraded channel with the receiver has the maximum consumables. Consumption value is higher than 200 g / s. The increase is observed for 60 G.P.K.V.

Since the opening of the inlet valve (348 G.K.V.) The flow rate (Fig. 3) begins to grow from 0 to 170m / s (at the modernized intake channel 210 m / s, with the -190m / s receivers) in the interval Up to 440-450 G.K.V. In the channel with the receiver, the speed value is higher than in a standard approximately 20 m / s starting from 430-440. P.K.V. The numeric value of the channel in the channel with the receiver is significantly more even than the upgraded inlet channel, during the opening of the inlet valve. Next, there is a significant reduction in the flow rate, up to the closure of the inlet valve.

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.

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.

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GOU VPO "Ural State Technical University - UPI named after the first president of Russia B.N. Yeltsin "

For manuscript rights

Thesis

for the degree of candidate of technical sciences

Gas dynamics and local heat transfer in the inlet system piston DVS

Carpenters Leonid Valerevich

Scientific adviser:

doctor Physico-Mathematical Audience,

professor Zhilkin B.P.

Ekaterinburg 2009.

piston Engine Gas Dynamics Intake System

The thesis consists of administration, five chapters, conclusion, a list of references, including 112 names. It is set out on 159 pages of computer dialing in the MS Word program and is equipped with text 87 drawings and 1 table.

Keywords: gas dynamics, piston DVS, intake system, transverse profiling, consumables, Local heat transfer, instant local heat transfer coefficient.

The object of the study was the non-stationary air flow in the inlet system of the piston engine of internal combustion.

The goal of the work is to establish the patterns of changes in the gas-dynamic and thermal characteristics of the inlet process in the piston internal combustion engine from geometric and regime factors.

It is shown that by placing the profiled inserts, it is possible to compare with a traditional channel of the constant round, to acquire a number of advantages: an increase in the volume flow of air entering the cylinder; The increase in the steepness of the dependence V on the number of rotation of the crankshaft N in the operating range of the rotation frequency at the "triangular" insert or linearization of the expenditure characteristic in the entire range of rotation numbers of the shaft, as well as suppressing high-frequency air flow pulsations in the inlet channel.

Significant differences in the patterns of changing the coefficients of heat transfer coefficients from the velocity W in the stationary and the pulsating flow of air in the inlet system of the DVS are established. The approximation of the experimental data was obtained equations for calculating the local heat transfer coefficient in the inlet tract of the FEA, both for stationary flow and for a dynamic pulsating flow.

Introduction

1. State of the problem and setting the objectives of the study

2. Description of the experimental installation and measurement methods

2.2 Measurement of the rotational speed and corner of the crankshaft rotation

2.3 Measurement of the instantaneous consumption of suction air

2.4 System for measuring instantaneous heat transfer coefficients

2.5 Data Collection System

3. Gas dynamics and consumables input process in the internal combustion engine at various intake system configurations

3.1 Gas dynamics of the intake process without taking into account the effect of the filter element

3.2 Influence of the filter element on the gas dynamics of the intake process in various intake system configurations

3.3 Consumables and spectral analysis of the inlet process with various intake system configurations with different filter elements

4. The heat transfer in the intake channel of the piston engine of internal combustion

4.1 Calibration of the measuring system to determine the local heat transfer coefficient

4.2 Local heat transfer coefficient in the inlet channel of the internal combustion engine at inpatient mode

4.3 Instant local heat transfer coefficient in the inlet channel of the internal combustion engine

4.4 Influence of the configuration of the inlet system of the internal combustion engine on the instantaneous local heat transfer coefficient

5. Questions of practical application of work results

5.1 Constructive and technological design

5.2 Energy and resource saving

Conclusion

Bibliography

List of basic designations and abbreviations

All symbols are explained when they are first used in the text. The following is only a list of only the most consumable designations:

d -Diameter of pipes, mm;

d e is an equivalent (hydraulic) diameter, mm;

F - surface area, m 2;

i - current strength, and;

G - mass flow air, kg / s;

L - Length, m;

l is a characteristic linear size, m;

n is the rotational speed of the crankshaft, min -1;

p - atmospheric pressure, PA;

R - resistance, Ohm;

T - absolute temperature, to;

t - the temperature on the Celsius scale, O C;

U - voltage, in;

V - air flow rate, m 3 / s;

w - air flow rate, m / s;

An excess air coefficient;

g - angle, hail;

The angle of rotation of the crankshaft, hail., P.K.V.;

Thermal conductivity coefficient, W / (M K);

Kinematic viscosity coefficient, m 2 / s;

Density, kg / m 3;

Time, s;

Resistance coefficient;

Basic cuts:

p.K.V. - rotation of the crankshaft;

DVS - internal combustion engine;

NMT - upper dead point;

NMT - Lower Dead Point

ADC - analog-to-digital converter;

BPF - Fast Fourier transformation.

Numbers:

Re \u003d WD / - Rangeld's number;

Nu \u003d D / - number of nusselt.

Introduction

The main task in development and improvement piston engines Internal combustion is to improve the filling of the cylinder with a fresh charge (or in other words, an increase in the filling coefficient). Currently, the development of the DVS has reached such a level that the improvement of any technical and economic indicator at least on the tenth share of the percentage with minimal material and temporary costs is a real achievement for researchers or engineers. Therefore, to achieve the goal, the researchers offer and use a variety of methods among the most common can be distinguished by the following: dynamic (inertial) reducing, turbocharging or air blowers, inlet channel of variable length, adjustment of the mechanism and phases of gas distribution, optimization of the intake system configuration. The use of these methods allows to improve the filling of the cylinder with a fresh charge, which in turn increases the engine power and its technical and economic indicators.

However, the use of most of the methods under consideration require significant material investments and a significant modernization of the design of the inlet system and the engine as a whole. Therefore, one of the most common, but not the simplest, to date, the methods of increasing the filling factor is to optimize the configuration of the engine inlet path. In this case, the study and improvement of the inlet channel of the engine is most often carried out by the method of mathematical modeling or static purges of the intake system. However, these methods cannot give correct results at the modern level of engine development, since, as is known, the real process in the gas-air paths of the engines is a three-dimensional gas inkjet expiration through the valve slot into a partially filled space of the variable volume cylinder. An analysis of the literature showed that the information on the intake process in real dynamic mode is practically absent.

Thus, reliable and correct gas-dynamic and heat exchange data for the intake process can be obtained exclusively in studies on dynamic MODELS OF DVS or real engines. Only such experienced data can provide the necessary information to improve the engine at the present level.

The aim of the work is to establish the patterns of changing the gas-dynamic and thermal characteristics of the process of filling the cylinder with a fresh charge of piston internal combustion engine from geometric and regime factors.

The scientific novelty of the main provisions of the work is that the author for the first time:

The amplitude-frequency characteristics of the pulsation effects arising in the stream in the intake manifold (pipe) of the piston engine;

A method for increasing air flow (on average by 24%) entering the cylinder using profiled inserts in the intake manifold, which will lead to an increase in engine power;

The patterns of changes in the instantaneous local heat transfer coefficient in the piston engine inlet tube are established;

It is shown that the use of profiled inserts reduces the heating of fresh charge at the intake by an average of 30%, which will improve the filling of the cylinder;

Generalized in the form of empirical equations The obtained experimental data on the local heat transfer of the pulsating flow of air in the intake manifold.

The accuracy of the results is based on the reliability of experimental data obtained by the combination of independent research methodologies and confirmed by the reproducibility of experimental results, their good agreement at the level of test experiments with these authors, as well as the use of a complex of modern research methods, selection of measuring equipment, its systematic testing and targeting.

Practical significance. The experimental data obtained create the basis for the development of engineering methods for calculating and designing ink-ink systems, and also expand theoretical representations about gas dynamics and local air heat transfer during the intake in piston engine. The individual results of the work were made to the implementation of the Ural Diesel Motor Plant LLC in the design and modernization of 6DM-21L and 8DM-21l engines.

Methods for determining the flow rate of the pulsating air flow in the inlet pipe of the engine and the intensity of instantaneous heat transfer in it;

Experimental data on gas dynamics and an instantaneous local heat transfer coefficient in the inlet channel of the input channel in the intake process;

The results of the generalization of the data on the local coefficient of air heat transfer in the inlet channel of the DVS in the form of empirical equations;

Approbation of work. The main results of studies set forth in the thesis reported and were presented at the "Reporting Conferences of Young Scientists", Yekaterinburg, UGTU-UPI (2006 - 2008); scientific seminars Department "Theoretical heat engineering" and "Turbines and engines", Yekaterinburg, UGTU-UPI (2006 - 2008); Scientific and Technical Conference "Improving Efficiency power plants Wheel and Crawler Machines ", Chelyabinsk: Chelyabinsk Higher Military Automobile Communist Party School (Military Institute) (2008); Scientific and Technical Conference "Development of Engineering in Russia", St. Petersburg (2009); on the Scientific and Technical Council under Ural Diesel Motor Plant LLC, Yekaterinburg (2009); On the Scientific and Technical Council for OJSC NII Autotractor Technology, Chelyabinsk (2009).

The dissertation work was performed at the departments "Theoretical heat engineering and" turbines and engines ".

1. Review of the current state of the study of piston inlet inlet systems

To date, there are a large number of literature, in which the constructive performance of various systems of piston engines of internal combustion, in particular, individual elements of the inlet systems of the ink systems are considered. However, there is practically no substantiation of the proposed design solutions by analyzing gas dynamics and heat transfer of the inlet process. And only in individual monographs provide experimental or statistical data on the results of operation, confirming the feasibility of one or another constructive performance. In this regard, it can be argued that until recently, insufficient attention was paid to the study and optimization of piston engines inlet systems.

In recent decades, in connection with the tightening of economic and environmental requirements for internal combustion engines, researchers and engineers are beginning to pay more and more attention to improving intake systems of both gasoline and diesel engines, believing that their performance is largely dependent on the perfection of processes occurring In gas-air paths.

1.1 Basic elements of piston inlet inlet systems

The intake system of the piston engine, in general, consists of a air filter, an intake manifold (or inlet tube), cylinder heads that contain intake and outlet channels, as well as the valve mechanism. As an example, in Figure 1.1, a diagram of the intake system of the YMZ-238 diesel engine is shown.

Fig. 1.1. Scheme of the intake system of the YMZ-238 diesel engine: 1 - intake manifold (tube); 2 - rubber gasket; 3.5 - connecting nozzles; 4 - Estimated gasket; 6 - hose; 7 - Air filter

The choice of optimal structural parameters and the aerodynamic characteristics of the intake system predetermine the efficient workflow and high level of output indicators of internal combustion engines.

Briefly consider each composite element inlet system and its main functions.

The cylinder head is one of the most complex and important elements in the internal combustion engine. From the correct selection of the shape and size of the main elements (first of all, the perfection of filling and mixing processes is largely depends on the size of intake and exhaust valves).

The cylinder heads are mainly made with two or four valves on the cylinder. The advantages of the two-flame design are the simplicity of manufacturing technology and the design scheme, in smaller structural mass and value, the number of moving parts in the drive mechanism, maintenance and repair costs.

The advantages of four-flaped structures consists in better use of the area limited by the cylinder circuit, for the passing areas of the valve gorlovin, in a more efficient gas exchange process, in a smaller thermal tension of the head due to a more uniform thermal state, in the possibility of central placement of the nozzle or candles, which increases the uniformity of the thermal state details piston group.

There are other designs of cylinder heads, for example, with three inlet valves and one or two graduation per cylinder. However, such schemes are applied relatively rare, mainly in highly affiliated (racing) engines.

The influence of the number of valves on gas dynamics and heat transfer in the inlet path is generally practically not studied.

The most important elements of the cylinder head from the point of view of their influence on gas dynamics and heat exchange input process in the engine are the types of inlet channels.

One of the ways to optimize the filling process is profiling inlet channels in the cylinder head. There is a wide variety of shapes of profiling in order to ensure the directional movement of fresh charge in the engine cylinder and improving the mixing process, they are described in the most detailed.

Depending on the type of mixing process, the intake channels are performed by one-functional (disgustable), providing only filling with cylinders with air, or two-function (tangential, screw or other type) used for inlet and twisting air charge in the cylinder and combustion chamber.

Let us turn to the question of the features of the design of intake collectors of gasoline and diesel engines. An analysis of the literature shows that the intake collector (or ink tube) is given little attention, and it is often considered only as a pipeline for supplying air or fuel-air mixture into the engine.

Air filter It is an integral part of the piston engine inlet system. It should be noted that in the literature, more attention is paid to the design, materials and resistance of the filter elements, and at the same time the effect of the filtering element on gas-dynamic and heat exchanged indicators, as well as the expenditure characteristics of piston internal combustion system, is practically not considered.

1.2 Gas dynamics of flow in inlet channels and methods for studying the inlet process in piston engine

For a more accurate understanding of the physical essence of the results obtained by other authors, they are outlined simultaneously with the theoretical and experimental methods used, since the method and result are in a single organic communication.

Methods for the study of inlet systems of the KHOs can be divided into two large groups. The first group includes theoretical analysis of the processes in the inlet system, including their numerical simulation. To the second group, we will draw all the ways to experimentally study the inlet process.

The choice of research methods, estimates and adjusting intake systems is determined by the goals set, as well as existing material, experimental and calculated possibilities.

To date, there are no analytic methods that allow it to be fairly accurate to estimate the level of intensity of gas in the combustion chamber, as well as solve private problems associated with a description of the movement in the intake path and the gas expiration from the valve gap in the real unsaluable process. This is due to the difficulties of describing the three-dimensional flow of gases on curvilinear channels with sudden obstacles, a complex spatial stream structure, with a jet gas outlet through the valve slot and a partially filled space of a variable volume cylinder, the interaction of flows between themselves, with the walls of the cylinder and the movable bottom of the piston. Analytical determination of the optimal field of velocity in the inlet tube, in the ring valve slot and the distribution of flows in the cylinder is complicated by the lack of accurate methods for evaluating aerodynamic losses arising from a fresh charge in the inlet system and when gas in the cylinder and flow around its internal surfaces. It is known that in the channel there are unstable zones of the transition of the flow from laminar to the turbulent flow mode, the region of the separation of the boundary layer. The flow structure is characterized by variables by time and the place of Reynolds, the level of non-stationarity, intensity and the scale of turbulence.

Many multidirectional work is devoted to numerical modeling of the movement of the air charge on the inlet. They produce modeling of the vortex intake-flux of the inlet of the inlet of the inlet of the inlet valve, the calculation of the three-dimensional flow in the inlet channels of the cylinder head, modeling the stream in the inlet window and the engine cylinder, an analysis of the effect of direct-flow and swirling streams on the mixing process and calculated studies of the effect of the charge twisting in the diesel cylinder The magnitude of emissions of nitrogen oxides and indicator cycle indicators. However, only in some of the works, numerical simulation is confirmed by experimental data. And solely on theoretical studies it is difficult to judge the accuracy and degree of applicability of the data. It should also be emphasized that almost all numerical methods are mainly aimed at studying the processes in the already existing design of the inlet of the inlet system of the intensity of the DVS to eliminate its deficiencies, and not to develop new, effective design solutions.

In parallel, the classical analytical methods for calculating the workflow in the engine and separate gas exchange processes in it are applied. However, in the calculations of the flow of gas in the inlet and exhaust valves and channels, the equations of one-dimensional stationary flow are mainly used, taking the current quasi-stationary. Therefore, the calculation methods under consideration are exclusively estimated (approximate) and therefore require experimental refinement in laboratory or on a real engine during bench tests. Methods for calculating the gas exchange and the main gas-dynamic indicators of the inlet process in a more difficult formulation are developing in the works. However, they also give only general information about the processes discussed, do not form a sufficiently complete representation of gas-dynamic and heat exchange rates, since they are based on statistical data obtained in mathematical modeling and / or static purges of the inlet tract of the ink and on the methods of numerical simulation.

The most accurate and reliable data on the inlet process in the piston engine can be obtained in the study on real-operating engines.

To the first studies of the charge in the engine cylinder on the shaft test mode, the classic experiments of Ricardo and the Cash can be attributed. Riccardo installed an impeller in the combustion chamber and recorded its rotational speed when the engine shaft is checked. The anemometer fixed the average gas speed value for one cycle. Ricardo introduced the concept of "vortex ratio", corresponding to the ratio of the frequency of the impeller, measured the rotation of the vortex, and the crankshaft. The CASS installed the plate in the open combustion chamber and recorded the effect on the air flow. There are other ways to use plates associated with tensidate or inductive sensors. However, the installation of plates deform the rotating stream, which is the disadvantage of such methods.

Modern research of gas dynamics directly on engines requires special Tools measurements that are capable of working under adverse conditions (noise, vibration, rotating elements, high temperature and pressure when combustion of fuel and in exhaust channels). In this case, the processes in the DVS are high-speed and periodic, so the measuring equipment and sensors must have very high speed. All this greatly complicates the study of the inlet process.

It should be noted that at present, methods of natural research on engines are widely used, both to study the flow of air in the inlet system and the engine cylinder, and for the analysis of the effect of vortex formation on the inlet for the toxicity of exhaust gases.

However, natural studies, where at the same time a large number of diverse factors acts, do not allow to penetrate the details of the mechanism of a separate phenomenon, do not allow to use high-precision, complex equipment. All this is the prerogative of laboratory studies using complex methods.

The results of the study of gas dynamics of the intake process, obtained in the study on engines are quite detailed in the monograph.

Of these, the greatest interest is the oscillogram of changes in the air flow rate in the input section of the inlet channel of the engine of C10.5 / 12 (D 37) of the Vladimir Tractor Plant, which is presented in Figure 1.2.

Fig. 1.2. Flow parameters in the input section of the channel: 1 - 30 s -1, 2 - 25 s -1, 3 - 20 s -1

Measurement of the air flow rate in this study was carried out using a thermoemometer operating in DC mode.

And here it is appropriate to pay attention to the very method of thermoemometry, which, thanks to a number of advantages, received such widespread gas-dynamics of various processes in research. Currently, there are various schemes of thermoanemometers depending on the tasks and the field of research. The most detailed theory of thermoenemometry is considered in. It should also be noted a wide variety of thermoemometer sensor designs, which indicates the widespread use of this method in all areas of industry, including engineering.

Consider the question of the applicability of the thermoenemometry method for studying the inlet process in piston engine. Thus, the small dimensions of the sensitive element of the thermoemometer sensor do not make significant changes in the nature of the flow of air flow; High sensitivity of the anemometers allows you to register fluctuations with small amplitudes and high frequencies; The simplicity of hardware scheme makes it possible to easily record the electrical signal from the output of the thermoemometer, followed by its processing on a personal computer. In thermomemometry, it is used in the sizing modes of one-, two- or three-component sensors. A thread or films of refractory metals with a thickness of 0.5-20 μm and a length of 1-12 mm are usually used as a sensitive element of the thermoemometer sensor, which is fixed on chromium or chromium-leather legs. The latter pass through a porcelain two-, three-way or four-grate tube, which is put on the metal case sealing from the breakthrough, the metal case, oked into the block head for the study of the intra-cylinder space or in pipelines to determine the average and ripple components of the gas velocity.

And now back to the oscillogram shown in Figure 1.2. The chart draws attention to the fact that it presents a change in the air flow rate from the angle of rotation of the crankshaft (P.K.V.) only for the intake tact (? 200 degrees. P.K.V.), whereas the rest Information on other clocks as it were "cropped". This oscillogram is obtained for the rotation frequency of the crankshaft from 600 to 1800 min -1, while in modern engines Range of operating speeds is much wider: 600-3000 min -1. Attention is drawn to the fact that the flow rate in the tract before opening the valve is not zero. In turn, after closing the intake valve, the speed is not reset, probably because in the path there is a high-frequency reciprocating flow, which in some engines is used to create a dynamic (or inertigice).

Therefore, it is important for understanding the process as a whole, data on the change in air flow rate in the inlet tract for the entire workflow of the engine (720 degrees, PKV) and in the entire operating range of the crankshaft rotation frequency. These data is necessary for improving the inlet process, searching for ways to increase the magnitude of a fresh charge entered into the engine cylinders and creating dynamic supercharow systems.

Briefly consider the peculiarities of dynamic supercharged in piston engine, which is carried out in different ways. Not only the gas distribution phases, but also the design of intake and graduation paths affect the intake process. The movement of the piston when the intake tact leads to an open intake valve to the formation of the backpressure wave. At an open intake pipeline, this pressure wave occurs with a mass of fixed ambient air, reflected from it and moves back to the inlet pipe. The fluctuate airfold of the air column in the inlet pipeline can be used to increase the filling of cylinders with fresh charge and, thereby obtaining a large amount of torque.

With a different form of dynamic superchard - inertial superior, each inlet channel of the cylinder has its own separate resonator tube, the corresponding length acoustics connected to the collecting chamber. In such resonator tubes, the compression wave coming from cylinders can spread independently of each other. When coordinating the length and diameter of individual resonator tubes with phases of the gas distribution phase, the compression wave, reflected in the end of the resonator tube, returns through the open inlet valve of the cylinder, thereby ensures its best filling.

The resonant reducing is based on the fact that in the air flow in the inlet pipeline at a certain rotational speed of the crankshaft there are resonant oscillations caused by the reciprocating movement of the piston. This, with the correct layout of the intake system, leads to a further increase in pressure and an additional adhesive effect.

At the same time, the mentioned dynamic boost methods operate in a narrow range of modes, require a very complex and permanent setting, since the acoustic characteristics of the engine are changed.

Also, gas dynamics data for the entire workflow of the engine can be useful to optimize the filling process and searches for increasing air flow through the engine and, accordingly, its power. At the same time, the intensity and scale of the turbulence of the air flow, which are generated in the inlet canal, as well as the number of vortices formed during the inlet process.

The rapid flow of charge and large-scale turbulence in the air flow provide good mixing of air and fuel and, thus, complete combustion with a low concentration of harmful substances in the exhaust gases.

One of the way to create the vortices in the intake process is the use of a flap that shares the intake path into two channels, one of which can overlap it, controlling the movement of the charge of the mixture. There are a large number of design versions to give the tangential component of the flow movement in order to organize directional vortices in the inlet pipeline and engine cylinder
. The purpose of all these solutions is to create and manage vertical vortices in the engine cylinder.

There are other ways to control the filling fresh charge. The design of a spiral intake canal is used in the engine with a different step of turns, flat venues on the inner wall and sharp edges at the channel output. Another device for regulating the vortex formation in the Cylinder of the engine is a spiral spring installed in the inlet channel and rigidly fixed by one end before the valve.

Thus, it is possible to note the trend of researchers to create large whirlwinds of different distribution directions on the inlet. In this case, the air flow must mainly contain large-scale turbulence. This leads to an improvement in the mixture and subsequent combustion of fuel, both in gasoline and diesel engines. And as a result, the specific consumption of fuel and emissions of harmful substances with spent gases are reduced.

However, in the literature there are no information about attempts to control the vortex formation using transverse profiling - a change in the form cross section Canal, and it is known to strongly affect the nature of the flow.

After the foregoing, it can be concluded that at this stage in the literature there is a significant lack of reliable and full information According to the gas dynamics of the intake process, namely: change in the air flow rate from the corner of the crankshaft rotation for the entire workflow of the engine in the operating range of the crankshaft rotation frequency; The effect of the filter on the gas dynamics of the intake process; the scale of the turbulence occurs during the intake; The influence of hydrodynamic nonstationarity on the consumables in the inlet tract of DVS, etc.

The urgent task is to search for the methods of increasing air flow through the engine cylinders with minimal engine refinement.

As already noted above, the most complete and reliable input data can be obtained from studies on real engines. However, this direction of research is very complex and expensive, and for a number of issues is almost impossible, therefore, the combined methods of studying processes in ICC have been developed by experimenters. Consider widespread from them.

The development of a set of parameters and methods of calculating and experimental studies is due to the large number of comprehensive analytical descriptions of the design of the inlet system of piston engine, the dynamics of the process and movement of the charge in inlet channels and the cylinder.

Acceptable results can be obtained when a joint study of the intake process on a personal computer using numerical modeling methods and experimentally through static purges. According to this technique, many different studies have been made. In such works, either the possibility of numerical simulation of swirling flows in the inlet system of the ink system, followed by testing the results using a purge in static mode on an inspector installation, or a calculated mathematical model is developed based on experimental data obtained in static modes or during the operation of individual modifications of engines. We emphasize that the basis of almost all such studies is taken experimental data obtained by the help of static blowing of the inlet system of the ink system.

Consider a classic way to study the intake process using a porch anemometer. With fixed valve lips, it produces a purge of the test channel with various second air consumption. For purge, real cylinder heads are used, cast from metal, or their models (collapsible wooden, gypsum, from epoxy resins, etc.) assembled with valves that guide bush lines and saddles. However, as described comparative tests, this method provides information on the effect of the form of the path, but the impeller does not respond to the action of the entire flow of air in cross section, which can lead to a significant error when estimating the intensity of the charge in the cylinder, which is confirmed mathematically and experimentally.

Another widespiliated method of studying the filling process is a method using a hidden lattice. This method differs from the previous one by the fact that the absorbed rotating air flow is sent to the fairing on the blade of the hidden grid. In this case, the rotating stream is stolen, and a jet moment is formed on the blades, which is recorded by the capacitive sensor in the magnitude of the Torcion spin angle. The hidden stream, having passed through the grille, flows through an open section at the end of the sleeve into the atmosphere. This method allows you to comprehensively evaluate the intake channel for energy indicators and by the magnitude of aerodynamic losses.

Even despite the fact that the methods of research on static models give only the most general idea of \u200b\u200bthe gas-dynamic and heat exchange characteristics of the inlet process, they still remain relevant due to their simplicity. Researchers are increasingly using these methods only for preliminary assessment of the prospects of intake systems or conversion already existing ones. However, for a complete, detailed understanding of the physics of phenomena during the inlet process of these methods is clearly not enough.

One of the most accurate and efficient ways to study the inlet process in the engine are experiments on special, dynamic installations. In the assumption that gas-dynamic and heat exchange features and characteristics of the charge in the inlet system are functions of only geometric parameters and regime factors for the study, it is very useful to use a dynamic model - an experimental installation, which most often represents a single-cylinder engine model on various high-speed modes acting with The help of a crankshaft test from an extraneous energy source, and equipped with different types of sensors. In this case, you can estimate the total effectiveness from certain solutions or their effectiveness is element. In general, such an experiment is reduced to determine the flow characteristics in various elements of the intake system (instantaneous values \u200b\u200bof temperature, pressure and speed), varying the corner of the rotation of the crankshaft.

Thus, the most optimal way to study the inlet process, which gives full and reliable data is the creation of a single-cylindrous dynamic model of piston engine, driven to rotation from an extraneous energy source. In this case, this method allows to investigate both gas-dynamic and heat exchangers of the filling process in the piston internal combustion engine. The use of thermoenemometric methods will make it possible to obtain reliable data without a significant effect on the processes occurring in the intake system of the experimental engine model.

1.3 Characteristics of heat exchange processes in the inlet system of piston engine

The study of heat exchange in piston internal combustion engine began in fact from the creation of the first working machines - J. Lenoara, N. Otto and R. Diesel. And of course at the initial stage, special attention was paid to the study of heat exchange in the engine cylinder. The first classic works in this direction can be attributed.

However, only work carried out by V.I. Grinevik, became a solid foundation, which turned out to be possible to build the theory of heat exchange for piston engines. The monograph in question is primarily devoted to the thermal calculation of intra-cylinder processes in the OI. At the same time, it can also find information about the heat exchanged indicators in the inlet process of interest to us, namely, there are statistical data on the magnitude of the heating of fresh charge, as well as empirical formulas to calculate the parameters at the beginning and end of the intake tact.

Further, researchers began to solve more private tasks. In particular, V. Nusselt received and published a formula for heat transfer coefficient in a piston engine cylinder. N.R. The brilling in his monograph clarified the formula of Nusselt and quite clearly proved that in each case (engine type, method of mixing formation, speed-rate, booming level) Local heat transfer coefficients should be clarified by the results of direct experiments.

Another direction in the study of piston engines is the study of heat exchange in the flow of exhaust gases, in particular, obtaining data on heat transfer during a turbulent gas flow in the exhaust pipe. A large number of literature is devoted to solving these tasks. This direction is quite well studied both in static purge conditions and under hydrodynamic nonstationarity. This is primarily due to the fact that, by improving the exhaust system, it is possible to significantly increase the technical and economic indicators of the piston internal combustion engine. In the course of the development of this area, many theoretical works were conducted, including analytical solutions and mathematical modeling, as well as many experimental studies. As a result of such a comprehensive study of the release process, a large number of indicators characterizing the process of release were proposed for which the quality of the design of the exhaust system can be assessed.

The study of heat exchange of the intake process is still given insufficient attention. This can be explained by the fact that studies in the field of heat exchange optimization in the cylinder and the exhaust tract were initially more effective in terms of improving the competitiveness of piston engine. However, currently the development of the engine industry has reached such a level that an increase in the engine indicator at least a few tenths percent is considered to be a serious achievement for researchers and engineers. Therefore, taking into account the fact that the directions of improving these systems are mainly exhausted, currently more and more specialists are looking for new opportunities for improving the workflows of piston engines. And one of such directions is the study of heat exchange during the inlet in the inlet.

In the literature on heat exchange in the intake process, work can be distinguished on the study of the influence of the intensity of the vortex flow of charge on the inlet on the thermal state of the engine parts (cylinder head, intake and exhaust valve, cylinder surfaces). These works are of great theoretical nature; Based on solving the nonlinear Navier-Stokes equations and Fourier-Ostrogradsky, as well as mathematical modeling using these equations. Taking into account a large number of assumptions, the results can be taken as a basis for experimental studies and / or be estimated in engineering calculations. Also, these works contain experimental studies to determine local non-stationary heat fluxes in a diesel combustion chamber in a wide range of intensity inlet air intensity.

The above-mentioned heat exchange work in the inlet process most often do not affect the influence of gas dynamics on the local intensity of heat transfer, which determines the size of the heating of fresh charge and temperature voltages in the intake manifold (pipe). But, as is well known, the magnitude of the heating of fresh charge has a significant effect on the mass consumption of fresh charge through the engine cylinders and, accordingly, its power. Also, a decrease in the dynamic intensity of heat transfer in the inlet path of the piston engine can reduce its temperature tension and thus will increase the resource of this element. Therefore, the study and solving these tasks is an urgent task for the development of the engine building.

It should be indicated that currently for engineering calculations use static purging data, which is not correct, since non-stationarity (flow pulsation) strongly affect heat transfer in the channels. Experimental and theoretical studies indicate a significant difference in heat transfer coefficient in nonstationary conditions from a stationary case. It can reach a 3-4-fold value. The main reason for this difference is the specific restructuring of the turbulent stream structure, as shown in.

It is established that as a result of the effect on the flow of dynamic nonstationarity (stream acceleration), it takes place in the kinematic structure, leading to a decrease in the intensity of heat exchange processes. Also, the work was found that the acceleration of the flow leads to a 2-3-to-alarm increase in the tanning tangent stresses and the subsequently as much as the decrease in local heat transfer coefficients.

Thus, for calculating the size of the heating of fresh charge and determining the temperature stresses in the intake manifold (pipe), data on the instantaneous local heat transfer is needed in this channel, since the results of static purges can lead to serious errors (more than 50%) when determining the heat transfer coefficient in the intake tract that is unacceptable even for engineering calculations.

1.4 Conclusions and setting the objectives of the study

Based on the above, the following conclusions can be drawn. Technological characteristics The internal combustion engine is largely determined by the aerodynamic quality of the intake path as a whole and individual elements: the intake manifold (intake pipe), the channel in the cylinder head, its neck and valve plates, combustion chambers in the bottom of the piston.

However, it is currently the focus on the optimization of the channel design in the cylinder head and complex and expensive cylinder filling systems with a fresh charge, while it can be assumed that only by profiling intake manifold can be affected by gas-dynamic, heat exchange and engine consumables.

Currently, there are a wide variety of means and measurement methods for a dynamic study of the inlet input process, and the main methodological complexity consists in their proper choice and use.

Based on the above analysis of literature data, the following dissertation tasks may be formulated.

1. To establish the effect of the intake manifold configuration and the presence of the filtering element on the gas dynamics and the consumables of the piston engine of the internal combustion, as well as reveal the hydrodynamic factors of the heat exchange of the pulsating stream with the walls of the inlet channel channel.

2. Develop a method for increasing air flow through an inlet system of piston engine.

3. Find the main patterns of changes in the instantaneous local heat transfer in the inlet path of the piston engine in the conditions of hydrodynamic nonstationarity in the classic cylindrical channel, and also find out the effect of the intake system configuration (profiled inserts and air filters) To this process.

4. To summarize the experimental data on an instantaneous local heat transfer coefficient in the piston inlet inlet manifold.

To solve the tasks to develop the necessary techniques and create an experimental setup in the form of a tool model of piston engine, equipped with a control and measuring system with automatic collection and data processing.

2. Description of the experimental installation and measurement methods

2.1 Experimental installation for the study of the inlet inlet

The characteristic features of the studied intake processes are their dynamism and frequency due to a wide range of rotation of the engine of the crankshaft of the engine, and a violation of the harmony of this periodicals associated with the unevenness of the piston movement and change in the configuration of the intake path in the zone valve assembly. The last two factors are interconnected with the action of the gas distribution mechanism. Reproduce such conditions with sufficient accuracy can only with the help of a field model.

Since gas-dynamic characteristics are functions of geometric parameters and regime factors, dynamic model Must correspond to the engine of a certain dimension and to work in characteristic high-speed modes of the crankshaft test, but already from an extraneous energy source. Based on this data, it is possible to develop and evaluate the total effectiveness from certain solutions aimed at improving the intake path as a whole, as well as separately by different factors (constructive or regime).

For the study of gas dynamics and heat transfer process in the piston engine of internal combustion, an experimental installation was designed and manufactured. It was developed on the basis of the engine model 11113 VAZ - Oka. When creating the installation, the prototype details were used, namely: connecting rod, piston finger, piston (with refinement), gas distribution mechanism (with refinement), crankshaft pulley. Figure 2.1 shows a longitudinal section of the experimental installation, and in Figure 2.2 is its transverse section.

Fig. 2.1. Lady cut of the experimental installation:

1 - elastic coupling; 2 - rubber fingers; 3 - rod cervical; 4 - native cervix; 5 - cheek; 6 - nut M16; 7 - counterweight; 8 - Nut M18; 9 - indigenous bearings; 10 - supports; 11 - Bearings connecting rod; 12 - rod; 13 - piston finger; 14 - piston; 15 - cylinder sleeve; 16 - cylinder; 17 - base of the cylinder; 18 - cylinder supports; 19 - Fluoroplast Ring; 20 - reference plate; 21 - hexagon; 22 - gasket; 23 - inlet valve; 24 - graduation valve; 25 - distribution shaft; 26 - pulley distribution Vala; 27 - crankshaft pulley; 28 - toothed belt; 29 - Roller; 30 - tensioner stand; 31 - tensioner bolt; 32 - Maslenka; 35 - Asynchronous Engine

Fig. 2.2. Transverse section of experimental installation:

3 - rod cervical; 4 - native cervix; 5 - cheek; 7 - counterweight; 10 - supports; 11 - Bearings connecting rod; 12 - rod; 13 - piston finger; 14 - piston; 15 - cylinder sleeve; 16 - cylinder; 17 - base of the cylinder; 18 - cylinder supports; 19 - Fluoroplast Ring; 20 - reference plate; 21 - hexagon; 22 - gasket; 23 - inlet valve; 25 - distribution shaft; 26 - camshaft pulley; 28 - toothed belt; 29 - Roller; 30 - tensioner stand; 31 - tensioner bolt; 32 - Maslenka; 33 - Insert profiled; 34 - measuring channel; 35 - Asynchronous Engine

As can be seen from these images, the installation is a natural model of the single-cylinder internal combustion engine of dimension 7.1 / 8.2. Torque S. asynchronous engine Transmitted through an elastic coupling 1 with six rubber fingers 2 on the crankshaft of the original design. The clutch used is capable of significantly compensate for the inconseability of the compound of the shafts of the asynchronous motor and the crankshaft of the installation, as well as to reduce dynamic loads, especially when starting and stopping the device. The crankshaft in turn consists of a connecting rod cervix 3 and two indigenous necks 4, which are connected to each other with cheeks 5. The rod cervix is \u200b\u200bpressed with tension in the cheek and fixed using nuts 6. To reduce vibrations to cheeks are fastened with anti-test bolts 7 . The axial movement of the crankshaft hinders the nut 8. The crankshaft rotates in the closed rolling bearings 9 fixed in the supports 10. Two closed rolling bearing 11 are installed onto a connecting rod neck, on which the connecting rod 12 is mounted. The use of two bearings in this case is associated with the landing size of the connecting rod . To the connecting rod with a piston finger 13, the piston 14 is mounted on the cast-iron sleeve 15, pressed in the steel cylinder 16. The cylinder is mounted on the base 17, which is placed on the cylinder supports 18. One wide fluoroplastic ring 19 is installed on the piston, instead of three standard Steel. The use of pig-iron sleeve and fluoroplastic ring provides a sharp decline in friction in pairs of piston - sleeves and piston rings - sleeve. Therefore, the experimental installation is capable of working a short time (up to 7 minutes) without a lubrication system and cooling system on the operating frequencies of the crankshaft rotation.

All major fixed elements of the experimental installation are fixed on the base plate 20, which, with two hexagons, 21 is attached to the laboratory table. To reduce the vibration between the hexagon and the support plate there is a rubber gasket 22.

The mechanism of timing experimental installation is borrowed from the VAZ 11113 car: a block head is used assembly with some modifications. The system consists of an inlet valve 23 and an exhaust valve 24, which are controlled using a camshaft 25 with pulley 26. The camshaft pulley is connected to the crankshaft pulley 27 with a toothed belt 28. On the crankshaft of the installation shaft placed two pulleys to simplify the drive belt tension system camshaft. The belt tension is controlled by roller 29, which is installed on the rack 30, and the tensioner bolt 31. Masliners 32 were installed for lubrication of the camshaft bearings, oil, of which gravity comes to the sliding bearings of the camshaft.

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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.

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 inverse cone-confusion region, to which the exhaust gas is already reducing with 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.

The gas-dynamic supervision includes methods for increasing the charge density at the inlet by use:

· The kinetic energy of air moving on the receiving device in which it is converted to the potential pressure of pressure when braking the stream - high-speed supervision;

· Wave processes in intake pipelines -.

In the thermodynamic cycle of the engine without boosting the beginning of the compression process occurs at pressure p. 0, (equal atmospheric). In the thermodynamic cycle of the piston engine with a gas-dynamic supervision, the beginning of the compression process occurs at pressure p K. , due to the increase in the pressure of the working fluid outside the cylinder from p. 0 BE p K.. This is due to the transformation of the kinetic energy and the energy of the wave processes outside the cylinder into the potential energy of pressure.

One of the energy sources to increase the pressure at the beginning of the compression may be the energy of the incident air flow, which takes place when the aircraft, car, etc. means. Accordingly, adding in these cases is called high-speed.

High-speed supervision Based on aerodynamic patterns of transformation of high-speed air flow in static pressure. Structurally, it is realized as a diffuser air intake nozzle, aimed at towing air flow when driving vehicle. Theoretically increase the pressure Δ p K.=p K. - p. 0 Depends on speed c. H and density ρ 0 incident (moving) air flow

High-speed supervision finds use mainly on aircraft with piston engines and sports carswhere speed speeds are more than 200 km / h (56 m / s).

The following varieties of gas-dynamic supervision of engines are based on the use of inertial and wave processes in the engine inlet system.

Inertial or dynamic reducing takes place at relatively high speed of moving fresh charge in the pipeline c. Tr. In this case, equation (2.1) takes

where ξ t is a coefficient that takes into account the resistance to the movement of gas in length and local.

Real speed c. The gas flow of gas in intake pipelines, in order to avoid elevated aerodynamic losses and deterioration in the filling of cylinders with fresh charge, should not exceed 30 ... 50 m / s.

The frequency of processes in the cylinders of piston engines is the cause of oscillatory dynamic phenomena in gas-air paths. These phenomena can be used to substantially improve the main indicators of engines (liter power and economy.

Inertial processes are always accompanied by wave processes (fluctuations in pressure) arising from the periodic opening and closing of the inlet valves of the gas exchange system, as well as the return-transit movement of the pistons.

At the initial stage of inlet in the inlet nozzle before the valve, a vacuum is created, and the corresponding wave of pouring, reaching the opposite end of the individual inlet pipeline, reflects the compression wave. By selecting the length and passage section of the individual pipeline, you can get the arrival of this wave to the cylinder at the most favorable moment before closing the valve, which will significantly increase the filling factor, and therefore torque M E. Engine.

In fig. 2.1. A diagram of a tuned intake system is shown. Through the inlet pipe, bypassing throttle valveThe air enters the receiving receiver, and the input pipelines of the configured length to each of the four cylinders from it.

In practice, this phenomenon is used in foreign engines (Fig. 2.2), as well as domestic engines for passenger cars with configured individual intake pipelines (for example, ZMZ engines), as well as on a 2h8.5 / 11 dysperse of a stationary electric generator having one configured pipeline on Two cylinders.

The greatest efficiency of gas-dynamic supervision takes place with long individual pipelines. Advance pressure depends on the coordination of the engine rotation frequency n., pipeline lengths L. Tr and corners

bending the closure of the intake valve (organ) φ A.. These parameters are related addiction

where is the local sound speed; k. \u003d 1.4 - the adiabatic index; R. \u003d 0.287 kJ / (kg ∙ hail.); T. - average gas temperature for the pressure period.

Wave and inertial processes can provide a noticeable increase in charge in a cylinder at large valve discoveries or in the form of increasing recharge in compression tact. The implementation of effective gas-dynamic supervision is possible only for a narrow range of engine rotation frequency. The combination of the phases of the gas distribution and the length of the intake pipeline must provide the greatest filling coefficient. Such selection of parameters are called setting the inlet system.It allows you to increase the engine power by 25 ... 30%. To preserve the effectiveness of gas-dynamic supervision in a wider range of rotational frequency of the crankshaft can be used various methods, in particular:

· Applying a pipeline with a variable length l. Tr (for example, telescopic);

· Switching from a short pipeline for long;

· Automatic regulation of gas distribution phases, etc.

However, the use of gas-dynamic supervision for engine boost is associated with certain problems. First, it is not always possible to rationally comply with sufficiently extended intake pipelines. It is especially difficult to do for low-speed engines, because with a decrease in the speed of rotation, the length of the adjusted pipelines increases. Secondly, fixed pipelines geometry gives dynamic setting only in some, quite a certain range of speed mode.

To ensure the effect in a wide range, a smooth or step adjustment of the length of the configured path is used when moving from one speed mode to another. Step regulation using special valves or rotary dampers is considered more reliable and successfully used in automotive engines of many foreign firms. Most often use control with switching into two customized pipeline lengths (Fig. 2.3).

In the position of the closed flap, the corresponding mode up to 4000 min -1, air supply from the intake receivers of the system is carried out along a long path (see Fig. 2.3). As a result (compared to the base version of the engine without gas-dynamic supervision), the flow of torque curve is improved on an external speed characteristic (at some frequencies from 2500 to 3500 min -1, the torque increases on average by 10 ... 12%). With increasing rotation speed N\u003e 4000 min -1 Feed switches to a short path and this allows you to increase the power N E. on nominal mode by 10%.

There are also more complex all-life systems. For example, designs with pipelines covering a cylindrical receiver with a rotary drum having windows for messages with pipelines (Fig. 2.4). When the cylindrical receiver is rotated, the length of the pipeline is increased and vice versa, when turning clockwise, it decreases. However, the implementation of these methods significantly complicates the engine design and reduces its reliability.

In multi-cylinder engines with conventional pipelines, the efficiency of gas-dynamic supervision is reduced, which is due to the mutual influence of intake processes in various cylinders. In the car engines, intake systems "set up" usually on the maximum torque mode to increase its stock.

The effect of gas-dynamic superior can also be obtained by the corresponding "setting" of the exhaust system. This method finds use on two-stroke engines.

To determine the length L. Tr and inner diameter d. (or passage section) of the adjustable pipeline it is necessary to carry out calculations using numerical methods of gas dynamics describing the non-stationary flow, together with the calculation of the workflow in the cylinder. The criterion is the increase in power,

torque or reducing the specific fuel consumption. These calculations are very complex. More simple methods Definitions L. three d. Based on the results of experimental studies.

As a result of the processing of a large number of experimental data to select internal diameter d. The adjustable pipeline is proposed as follows:

where (μ. F. Y) MAX is the most effective area of \u200b\u200bthe inlet valve slot. Length L. The trifle pipeline can be determined by the formula:

Note that the use of branched tuned systems such as a common pipe - receiver - individual pipes turned out to be very effective in combination with turbocharging.