DESIGN OF A THERMOACOUSTIC MODULE OF A VEHICLE ENGINE

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1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 9, Issue 4, April 2018, pp , Article ID: IJMET_09_04_118 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed DESIGN OF A THERMOACOUSTIC MODULE OF A VEHICLE ENGINE Nikolay Anatolyevich Khripach, Lev Yurievich Lezhnev, Denis Alekseevich Ivanov, Fedor Andreevich Shustrov and Alexey Pavlovich Tatarnikov Moscow Polytechnic University, Russia, , Moscow, st. Bolshaya Semenovskaya, 38 ABSTRACT The use of a thermoacoustic module of a vehicle engine as part of an exhaust system is one of the promising ways to reduce the noise of exhaust gases. The importance of using the module is determined by promising norms for the noise level of exhaust gases from the engine, according to which a noise reduction of up to 71 dba is required. The efficiency of using the thermoacoustic module is achieved by the cooling of exhaust gases at C, reducing the emission noise by more than 2 db. The article presents the main issues of the thermometering of a vehicle internal combustion engine and experimental data obtained as a result of thermometry. The process of thermometering of the exhaust system is the acquisition of data on the temperature distribution of the exhaust gases at the required points of the system. The purpose of thermometering of an internal combustion engine is to choose the location for the thermoacoustic module of the automobile engine and to develop recommendations for its application. The data of the engine exhaust thermometering are used to select the main design parameters of the module and structural materials for the casing elements of the thermoacoustic module, the parts of a heat exchanger, and to choose the material of foamed metal. Key words: internal combustion engine, exhaust gas, measurements, temperature, pressure, thermoacoustic module. Cite this Article: Nikolay Anatolyevich Khripach, Lev Yurievich Lezhnev, Denis Alekseevich Ivanov, Fedor Andreevich Shustrov and Alexey Pavlovich Tatarnikov, Design of a Thermoacoustic Module of a Vehicle Engine, International Journal of Mechanical Engineering and Technology, 9(4), 2018, pp INTRODUCTION Internal combustion engine (ICE), used in automobiles and other vehicles, is a complex device for performing useful mechanical work. During the operation of the ICE side heat is generated, consisting mainly of low-potential heat energy diverted from the ICE through the cooling system and high-potential thermal energy represented by the exhaust gases of the editor@iaeme.com

2 Design of a Thermoacoustic Module of a Vehicle Engine engine [1]. For example, exhaust gases at the exit from the ICE have a high residual temperature, which decreases during the passage of gases through the exhaust system. The exhaust system of an automobile engine consists of several consecutive components. In general, the exhaust system includes a exhaust manifold, a receiving tube, a flexible compensator, a catalytic converter, a resonator and a silencer connected by pipelines [2]. The importance of reducing the noise production is determined by many factors, including a negative impact on the cardiovascular system and mental health of a human. Note that noise occupies the third place of the harmful factors affecting the human body, following the atmospheric air and drinking water pollution by chemical components. The noise produced by vehicles has the greatest impact on the overall level of acoustic pollution and amounts to 60% [3]. The thermoacoustic module of the automobile engine (TAMAE) installed in the exhaust system is one of the modern methods of noise reduction of exhaust gas. It allows meeting the requirements of perspective noise reduction standards up to 71 dba and lower (according to Annex III of Regulation # 540/2014 "Limit Values") without increasing the back pressure of the exhaust system. The change in the exhaust gas temperature along the length of the exhaust system creates its own temperature conditions for the operation of each component of the system. Thus, the initial data for each component of the exhaust system, including temperature, speed, exhaust gas volume flow and other parameters, will differ. To optimize the design and operating conditions of the components of the exhaust system, it is necessary to determine the location of each component. It is recommended to carry out the optimization with the use of an array of data with exhaust temperatures typical for different load and speed modes of the ICE and presented as a graph of a surface with three coordinate axes [4]. Such an array can be obtained as a result of thermometering of the exhaust system. Thermometering is a process of the determination of the exhaust gas temperature distribution along the length of the exhaust system at the required points, using a constant recording of the temperature values, which allows achieving a high density of results. Distribution data of the exhaust gas temperature along the length of the exhaust system is a reliable source of the boundary conditions for the operation of the components of the exhaust system and allows designing the effective components of this system by optimizing their construction in terms of performance and structural materials used. Creating an efficient exhaust system with mutual bracing of components and their parameters is rather difficult without the use of detailed thermometry data. As the value of certain parameters of the exhaust gas, like density, viscosity, and thermal conductivity, depends on the temperature. There are two most commonly used methods to determine the distribution of the exhaust gas temperature along the length of the exhaust system. 1) Computational research using mathematical models and computational complexes for computers, including the use of empirical and other dependencies, improving the calculation accuracy. An examination of gas-dynamic processes occurring in an exhaust pipe a mathematical model was considered in the work [5]. The study focuses on solving the problem of rapid heating of the catalytic converter after starting the engine, which is solved by burning a small volume of the fuel-air mixture presented in the exhaust gas stream. Also, controlling the temperature of the exhaust gas in the catalytic converter is an important task for increasing the efficiency of its operation and durability [6] editor@iaeme.com

3 Nikolay Anatolyevich Khripach, Lev Yurievich Lezhnev, Denis Alekseevich Ivanov, Fedor Andreevich Shustrov and Alexey Pavlovich Tatarnikov Obtaining of high-precision data on temperature and pressure of exhaust gases with a mathematical model is difficult because of the complexity of the external factors influence, presented during the movement of the vehicle. One of these factors is blowing the outer surface of the exhaust system with a counter flow of air [7], which leads to cooling of the pipe surface and a decrease in the temperature of the wall layer of the exhaust gas. The work [8] is devoted to the determination of the temperature profile of the exhaust gas flow in the longitudinal section of the exhaust pipe for the ICE operating under various loads. The above-mentioned examples prove the rather high complexity of the analytical determination of the temperature of exhaust gas moving in the exhaust system. Generally, accurate modeling requires multidimensional computational complexes or mathematical models with empirical data used to improve the accuracy of calculations. There is also the complexity of modeling the combustion process of the fuel-air mixture in the engine cylinder, which determines the exhaust gas temperature. For this purpose, a fuel-air mixture combustion model is used with its own assumptions affecting its accuracy. 2) Conducting bench tests using ICE and dynamometric equipment, with thermometering of the exhaust system. Thermometering is carried out using measuring tools: exhaust system's temperature sensors, a signal converter, and recording equipment. The paper [9] presents the results of studies carried out for the comparative evaluation of the heat transfer coefficients in the pipes of the exhaust system, obtained with the theoretical model and according to the results of the experiment. It was estimated that at the same mass flow rate and exhaust gas temperature at the inlet, the heat transfer coefficient for the intermittent exhaust gas flow is higher than the coefficient measured at the continuous flow. The study [10] conducted three types of tests, including the exhaust gas temperature measurement before and after the oxidative catalyst and the diesel particulate filter (DPF). Thermometering of the exhaust system carried out under the motor stand provides the possibility of obtaining detailed temperature characteristics of the exhaust gas and high reliability of measurements, which, in general, is limited only by the accuracy of the measuring equipment. Thus, this method provides a higher reliability of results in comparison with theoretical studies. Data on the distribution of the exhaust gas temperature along the entire length of the exhaust system is a reliable source of the boundary conditions for the operation of all components of the system. This contributes to the creation of effective components of the exhaust system by optimizing their design in terms of performance and structural materials used. 2. METHODS The base of the procedure for thermometry of the exhaust system is the process of obtaining data on the distribution of exhaust gas temperature at the required points of the exhaust system of an automobile engine operating in the required load-speed range and analyzing the values obtained. Then the values obtained are used to determine the location for the most optimal placement of the TAMAE in the exhaust system. The criteria for optimal locating include the following: The high residual energy of the exhaust gas at the inlet to the TAMAE, determined by the temperature and speed of the exhaust gas; editor@iaeme.com

4 Design of a Thermoacoustic Module of a Vehicle Engine The location of TAMAE must be coordinated with other components of the exhaust system. The test unit is a 4-stroke 4-cylinder gasoline engine ZMZ (ЗМЗ ) equipped with a distributed fuel injection system and installed in a testing laboratory on a chassis dynamometer equipped with the necessary systems. Typically, the process of exhaust system thermometering is the acquisition of an array of data on the distribution of exhaust gas temperature along the entire length of the exhaust system. Moreover, in this study, exhaust gas temperatures are determined when the ICE operates on the load and speed modes, forming its operating range. During thermometering, exhaust gas temperature is measured at 5 points of the exhaust system: 1. before the catalytic converter; 2. after the catalytic converter (before the resonator); 3. after the resonator (before the silencer); 4. after the silencer; 5. at the exit from the exhaust system. Figure 1 on the scale shows the scheme of the exhaust system used for thermometry. The total length of the exhaust system under consideration is 4620 mm, and the locations of the five temperature sensors are indicated by the positions 1 to 5. Figure 1 Exhaust system scheme The thermometering uses the thermal converters with low thermal inertia with the response time not exceeding 0.6 seconds. The presence of thermal inertia of the thermal converters leads to a measurement error in determining the temperature of the variable media, since it takes a certain amount of time to equalize the temperature of the sensor and the medium. In the thermometering method used, measurements of 5 values of the exhaust gas temperatures are carried out at a 1-second interval, and the average temperature value is recorded in the test reports. The construction of the exhaust gas temperature sensor used has sufficient thermal strength, which makes it possible to use the sensor directly in the flow of hot exhaust gases without the use of additional protective covers and shields. The number of tasks to be performed in the process of thermometering is extended by additional measurement of the exhaust gas pressure at selected points of the exhaust system. For this purpose, the measuring equipment includes pressure transducers, as well as components for cooling hot exhaust gases before they enter the measuring cavity of the pressure transducer and various damping devices reducing the pulsation of the exhaust gas flow in the measuring cavity. During the thermometering of the exhaust system, the influence of the oncoming airflow is not taken into account, since the creation of the required flow requires the use of additional air supply systems editor@iaeme.com

5 Nikolay Anatolyevich Khripach, Lev Yurievich Lezhnev, Denis Alekseevich Ivanov, Fedor Andreevich Shustrov and Alexey Pavlovich Tatarnikov 3. RESULTS The section presents the results of additional studies on the measurement of temperature and exhaust gas pressure at 5 points of the exhaust system of an automobile engine conducted under various load and speed conditions of the engine. Figure 2 shows a graph of the change in the exhaust gas temperature along the length of the exhaust system obtained during engine operation at full load and in the range of the crankshaft speed from 850 to 3000 rpm. Each curve of the graph corresponds to the crankshaft speed of the ICE, and the vertical lines correspond to the 5 points in which the measurements are made. Figure 2 Graph of the exhaust gas temperature variation along the length of the exhaust system Figure 3 shows a 3D diagram of the dependence of the exhaust gas temperature on the crankshaft speed (from 850 to 5000 rpm) and the load on the engine (from 0 to 100%.). The diagram used the exhaust gas temperature at point #3 (figure 1), located before the silencer of the exhaust system. The choice of point # 3 for analysis is determined by the fact that this section is most likely for the location of TAMAE in the exhaust system, and the exhaust gas temperatures at point # 3 correspond to the exhaust gas temperatures at the module inlet. Figure 3 Diagram of the exhaust gas temperature change from the load and speed mode of ICE operation editor@iaeme.com

6 Design of a Thermoacoustic Module of a Vehicle Engine The results obtained show that the maximum exhaust gas temperature at the entrance to the silencer is 790 C, which corresponds to a rotation speed of 5000 rpm at full engine load. In this case, depending on the load-speed operating mode of the ICE, the exhaust gas temperature decrease after the passage of the silencer is from 80 to 145 C. It should be noted that the characteristics obtained at full load are of interest from the point of view of determining the maximum values of the exhaust gas temperature and the exhaust gas pressure drop along the length of the exhaust system, but they are not typical for the urban driving cycle. The characteristics obtained at partial loads in the range of 10 to 50% and the speed of rotation to 3000 rpm are of practical interest since these regimes are most typical for the urban driving cycle. So, the exhaust gas temperatures measured at point #3, show the minimum value of 230 C and corresponds to a rotation speed of 850 rpm at a load of 10%, and a maximum temperature of 525 C is achieved at a rotation speed of 3000 rpm and a load of 50%. Figure 4 shows a 3D diagram of the change in exhaust gas pressure at point #3 of the exhaust system. In the diagram, the exhaust gas pressure values obtained during engine operation in the range of engine speed from 850 to 5000 rpm and at partial loads from 0 to 50% were used. Figure 4 Diagram of the change in exhaust gas pressure in the exhaust system, depending on the load and speed conditions of the ICE The results show that the maximum exhaust gas pressure located before the silencer of the exhaust system reaches 111 kpa at a speed of 5000 rpm and a load of 50%. Taking into account the exhaust gas pressures at a point located after the silencer (point #4), it is possible to calculate that the maximum pressure drop in the silencer is 4 kpa at a rotation speed of 3000 rpm and a load of 50%. 4. DISCUSSION The article presents a brief description of the thermometering procedure and the results of thermometry of the standard exhaust system for a gasoline 4-cylinder ICE. The obtained results are of practical interest from the point of view of choosing the location of TAMAE in the exhaust system and designing its construction editor@iaeme.com

7 Nikolay Anatolyevich Khripach, Lev Yurievich Lezhnev, Denis Alekseevich Ivanov, Fedor Andreevich Shustrov and Alexey Pavlovich Tatarnikov Reducing exhaust gas temperature along the length of the exhaust system is connected with the work performed during the exhaust gas expansion. Also, the change in exhaust gas temperature along the length of the exhaust system is affected by thermal losses to the environment through the outer surface of the components of the exhaust system. It should be noted that the exothermic reactions taking place in the catalytic converter during the oxidation of CO and CH occur with the release of heat and can influence the temperature of the exhaust gas. The impact of these reactions is particularly indicative in the engine warm-up modes when an enriched mixture is supplied to accelerate the output of the neutralizer to the operating temperature, which is not reflected in the current research. It is known that an increase in the exhaust gas temperature leads to a proportional increase in the volumetric flow rate of the gas since the density of the exhaust gas decreases. Thus, the exhaust gas volume flow at the inlet to the exhaust system is higher than at the output. It is also obvious that when the exhaust gas is moving in the exhaust system, the exhaust gas pressure drops. This occurs due to the internal hydraulic resistance of each component of the exhaust system. The TAMAE placed in the exhaust system in addition to or instead of the basic silencer should not give rise to a counter pressure that exceeds the limit values for the standard exhaust system. TAMAE construction TAMAE is a split structure, which includes a heat exchanger and case elements. The tubular heat exchanger consists of three separate sections arranged consistently. The flow of exhaust gas moves in the tube space of the heat exchanger, and the coolant circulates in the annular space. The heat exchange elements from the foamed metal are located inside the heat exchange tubes. The body elements of TAMAE are represented by inlet and outlet manifolds having a conical contour. Figure 5 shows a three-dimensional draft of TAMAE, which presents the adopted structural and layout solutions. Figure 5 Construction of TAMAE: a) general view; b) longitudinal section TAMAE arrangement in the exhaust system Exhaust temperature change and exhaust gas pressure along the length of the exhaust system has a direct impact on the choice of the location of TAMAE in the system. There are several conditions for placing TAMAE in the exhaust system. So the exhaust gas at the entrance to TAMAE must have a high residual energy, determined by the editor@iaeme.com

8 Design of a Thermoacoustic Module of a Vehicle Engine temperature and speed of the exhaust gas. Thus, the module should be located at a small distance from the exhaust manifold of the engine. The corresponding requirements for high exhaust temperature are applied to the catalytic converter and it is usually located in modern exhaust systems near the exhaust manifold. Taking into account the joint use of the catalytic converter and TAMAE in the exhaust system, the positioning of TAMAE before the catalytic converter is not possible, since a significant reduction in the exhaust gas temperature occurs at the output of the module. And as for the efficient operation of the neutralizer, it is necessary to introduce exhaust gas at a high temperature into it, the positioning of TAMAE in the exhaust system after the catalytic converter is the only solution. TAMAE should be installed after the catalytic converter using a flexible compensator to reduce the movements and vibrations transmitted to the exhaust system from the running engine. In this case, the exhaust gas energy at the input to the TAMAE is high, which makes it possible to effectively use the module for the total reduction of the output noise. Selection of TAMAE construction design parameters The efficiency of the TAMAE construction design and the design of other components of the exhaust system can be assessed by functional and mass dimensions. Mass dimension indicators are an important direction for optimizing the design in mass production and a highly competitive market. As it was said before, the volume flow of the exhaust gas changes along the length of the exhaust system and this allows determining the geometric parameters of the components of the exhaust system, corrected for this feature, namely, to calculate their cross-section. So the cross-section of the last components of the exhaust system can be reduced compared to the first sections without increasing the counterpressure. The obtained data allowed us to determine some design parameters of TAMAE, as well as to confirm the correctness of the choice of previously adopted solutions. Each of the three sections of the heat exchanger is a shell-and-tube heat exchanger, in which the counterflow is organized. While the annular spaces of each section are connected consistently with each other by means of hoses, as a result of which a single cooling circuit is formed. Inside the heat exchange tubes, there are elements of a foamed metal or other suitable material. This solution provides an increase in the area of the heat exchange surface and an intensification of heat exchange between the exhaust gas and the pipe wall. The shape of the inlet and outlet manifolds is conical, which is aimed at providing a compromise between the overall dimensions, the aerodynamic resistance and the uniformity of the exhaust gas flow distribution at the operating flow and exhaust temperature. The adopted design solutions must ensure the reduction of the exhaust pressure in TAMAE, but not exceeding the values for the standard exhaust silencer. In the TAMAE construction, sound-absorbing materials are used (not shown in Figure 5), located on the inner surface of the collectors and between each section of the heat exchanger. Selection of structural materials The choice of structural materials for the manufacture of pipelines for exhaust systems and components case located before the TAMAE is known in advance and is limited by the properties of aluminized and stainless steels. Therefore, in this section, the basics of the choice of materials for the manufacture of a heat exchanger and foamed metal parts, as well as editor@iaeme.com

9 Nikolay Anatolyevich Khripach, Lev Yurievich Lezhnev, Denis Alekseevich Ivanov, Fedor Andreevich Shustrov and Alexey Pavlovich Tatarnikov the choice of materials for the manufacture of the exhaust system located after TAMAE, will be presented. The existing foamed metals are made of aluminum, copper, nickel, chromium-nickel alloy, etc. The use of aluminum in an aggressive environment in the form of hot exhaust gases is impractical. Copper is suitable for use in TAMAE for various research tasks, but its use in serial samples is limited because the operating conditions can lead to overheating of the foamed metal (misfiring, anomalous combustion, and other ICE malfunctions). Obviously, the creation of durable foamed metal elements is possible from nickel or chromium-nickel alloy. According to Sumitomo Electric Industries [11], the resistance of nickel and chromium-nickel alloy foamed metals to oxidation under long-term heating conditions to 600 ºC and 860 ºC is different. Figure 6 shows a graph of the increase in the mass of samples of the foamed metal, caused by their oxidation. It is indicated the presence of a mechanism in which the oxide films on the surfaces of the chromium-nickel alloy are denser than on nickel. As a result, after the oxidation of the outermost surface, the intake of oxygen is blocked more efficiently, which slows the oxidation process. Figure 6 An increase in weight of various foamed metals The foamed metal used in TAMAE can be heated up to 800 C during operation. Thus, to ensure a sufficient service life, it is recommended to use a foamed metal from a chromiumnickel alloy with operating temperature of at least 1000 C. Among the peculiarities arising when using TAMAE in the exhaust system, there is also a significant reduction in the exhaust gas temperature after the passage of the module. The maximum values of exhaust gas temperatures at the outlet from TAMAE are no more than C, which allows the use of non-metallic structural materials (i.e. plastic) after the module in the course of the exhaust gas flow. This solution significantly reduces weight and increases the durability of components made of plastic, since this material is not susceptible to corrosion. Modern technologies for working with plastics, including die casting, hot forming, etc., allow creating various configurations of components of the exhaust system editor@iaeme.com

10 Design of a Thermoacoustic Module of a Vehicle Engine 5. CONCLUSION As a result of thermometering in 5 points of the exhaust system, an objective idea about the distribution of exhaust gas temperature in the exhaust system of a piston automobile engine was obtained. The results of the change in the exhaust gas temperature in the exhaust system of an internal combustion engine operating at various load-speed regimes covering its operating range are obtained. The values of the measured exhaust temperature, depending on the load on the engine and the engine speed, are presented as a 3D chart. It is noted that the decrease in the exhaust gas temperature along the length of the exhaust system is associated with the performance of work during the expansion of the exhaust gas, as well as the presence of thermal losses to the environment through the outer surface of the components of the exhaust system. The article gives recommendations on the choice of materials for the manufacture of foam-metallic elements used in the TAMAE design and also explains the feasibility of using a chromium-nickel alloy foamed metal. The work also considered the possibility of using non-metallic structural materials for the manufacture of components of the exhaust system located after TAMAE, which became possible due to a significant decrease in the exhaust gas temperature after passing through the module, which would not exceed C. The obtained results of the exhaust system thermometry can be used as reference material or preliminary initial data during the research work related to the study of the ICE work process and the development of components of the exhaust system. ACKNOWLEDGMENTS This work was financially supported by the Ministry of Education and Science of the Russian Federation within the subsidiary grant agreement No dated September 26, Unique identifier: RFMEFI57417X0144. REFERENCES [1] Bourhis, G. and Leduc, P. Energy and Exergy Balances for Modern Diesel and Gasoline Engines. Oil & Gas Science and Technology, Rev. IFP, 65(1), 2010, pp [2] Rajadurai, S., Afnas, M., Ananth, S. and Surendhar, S. Materials for Automotive Exhaust System. International Journal of Recent Development in Engineering and Technology, 2(3), 2014, pp [3] Khripach, N.A., Lezhnev, L.Y., Neverov, V.A., Ivanov, D.A. & Papkin, B.A. Comparative analysis of EG noise suppression systems. International Journal of Civil Engineering and Technology, 8(10), 2017, pp [4] Morgan, R., Dong, G., Panesar, A.S. and Heikal, M. A comparative study between a Rankine cycle and a novel intra-cycle based waste heat recovery concepts applied to an internal combustion engine. Applied Energy, 174, 2016, pp [5] Gasser, I. and Rybicki, M. Modelling and simulation of gas dynamics in an exhaust pipe. Applied Mathematical Modelling, 37(5), 2013, pp [6] Gasser, I., Rybicki, M. and Wollner, W. Optimal control of the temperature in a catalytic converter. Computers & Mathematics with Applications, 67(8), 2014, pp [7] Xiao, G. Transient simulation of heat transfers for vehicle exhaust system, 7th International Conference on Fluid Mechanics, ICFM7. Procedia Engineering, 126, 2015, pp editor@iaeme.com

11 Nikolay Anatolyevich Khripach, Lev Yurievich Lezhnev, Denis Alekseevich Ivanov, Fedor Andreevich Shustrov and Alexey Pavlovich Tatarnikov [8] Brito, C.H. G., Maia, C.B. and Sodré, J.R. A Mathematical Model for the Exhaust Gas Temperature Profile of a Diesel Engine. Journal of Physics: Conference Series, 633, 2015, as.pdf. [9] Sorin, A., Bouloc, F., Bourouga, B. and Anthoine, P. Experimental study of periodic heat transfer coefficient in the entrance zone of an exhaust pipe. International Journal of Thermal Sciences, 47(12), 2008, [10] Gonzales, R.H. Diesel Exhaust Emission System Temperature Test, U.S. Department of Agriculture Forest Service, National Technology & Development Program Fire Management SDTDC, December [11] Okuno, K., Majima, M., Awazu, T., Tsukamoto, K., Tsuchida, H., Saito, H. Development of High Corrosion Resistance Celmet. SEI Technical Review, 75, 2012, pp [12] K. M. Ravichandra, D. Manikanta, M. Kotresh, CFD Simulation of an IC Engine by Producer Gas. International Journal of Civil Engineering and Technology, 8(10), 2017, pp editor@iaeme.com