Exhaust System Resistance And Temperature Field Distribution Law Study Of Heavy-Duty Commercial Vehicle

With the increasing of motor vehicles, especially the heavy-duty commercial vehicles, problems, such as vehicle exhaust gas and noise, are becoming serious matters influencing the people’s daily life. However, exhaust system on present commercial vehicles usually have the problems that exhaust noise of engine could not be reduced effectively and exceeds the limit value of84dB specified in national regulations, so noise abatement ability is weak. Meanwhile, because of the high resistance of exhaust and the high power loss of engine, fuel consumption is increased. Consequently, it becomes more and more important to increase the noise abatement ability and reduce the exhaust resistance. Exhaust muffler, which is concerned with more branches of knowledge, such as fluid mechanics, heat transmission, vibration, acoustics, engine performance and so on. Domestic studies and researches are mostly based on experiments and experiences of application developers, for the more and more complicated structures of muffler, it could not satisfy the requirements for theoretical guidance and practical design.The article, through numerical modeling the exhaust system of commercial vehicle, adopts allocation method of mixed grid and standard k-ε module, applys FLUENT numerical modeling software to simulate the inner flow field and the temperature field of muffler and calculates the distribution situations of parameters of inner pressure, velocity, temperature and so on. After analyzing, it is concluded that the resistance is various, because the gas is getting through the tube, and pressure will then reduce greatly, the fluid expands inside the chamber, and turbulent flow on panel is too large. The temperature will be axially reduced gradually along the muffler, the temperature difference of inlet and outlet will be200℃, and the wall temperature of muffler will be about70℃to90℃. Gas velocity inside the chamber will be increased with the pressure rising, fluid radial velocity on panels is high, and turbulence energy is big, turbulent flow is serious, so the resistance is increasing.According to the analysis results, the inner structure of muffler is optimized, the insert depth of the tube and the allocation of chamber volume are improved, and tail pipe is added. After modification, the pressure allocation of inner fluid field is evenly distributed on the second chamber, large turbulence is obviously reduced to prevent causing secondary noise and the temperature changes distinctively in the two chambers, then the outlet temperature can be lowered down and the completed performance of muffler is perfected.