Study On Thermal Management And Attenuation Performance Of Automobile Exhaust Muffler

When the high temperature gas discharged from the engine of automobile flows into the muffler,it will have a great influence on the performance of muffler.High temperatures can not only change the properties of the gas,but also affect the sound propagation within the muffler.Therefore,it is very necessary to explore the effect of temperature on attenuation performance of muffler.This paper presents an heat exchanging system of exhaust that can effectively reduce exhaust temperature,and carries out simulation analysis and experimental verification to prove the feasibility of the design.In addition,this paper also explores the influence of exhaust heat management on attenuation performance of muffler,and analyzes the effect of structural parameters of muffler on anechoic characteristics.The main contents of this paper are delivered as followings :(1)Aiming at the effect of high temperature on attenuation performance of muffler,an heat exchanging system of exhaust is proposed to reduce the temperature of exhaust gas and further reduce exhaust noise.The an heat exchanging system of exhaust mainly includes a water tank of engine and a heat exchange structure,both of which are connected by pipelines.The high temperature gas of engine exchanges heat with circulating fluid of cooling in the heat exchange structure to reduce temperature of the gas flowing into muffler.(2)CFD simulation of the heat transfer structure of the exhaust heat exchange system was performed using Fluent software.The distribution cloud maps of pressure field,velocity field and temperature field were obtained.The calculation results show that heat exchange structure is matched with exhaust muffler to meet the back pressure requirements of exhaust system.The heat exchange structure can reduce exhaust temperature by 130°C,and ensure that the temperature rise of coolant does not exceed 5°C and does not affect cooling system of engine normally working.At the same time,verifying on the test bench,the error between test results and simulation results is within 5%,indicating that the simulation result is accurate,and the design of heat exchange structure has certain feasibility.(3)An acoustic simulation analysis was used to study the effect of thermal management on attenuation characteristics in exhaust muffler.A coupling model of engine,heat transfer structure and muffler was established in GT-Power software.The effect of temperature was considered in the analysis.Transmission loss of muffler and tail pipe noise on two states—exhaust heat exchange system working and non-working were obtained.The results show that when exhaust heat exchange system is in operation,the transmission loss curve moves to the low-frequency direction integratedly.It effectively reduce the low-frequency noise,and the noise of tail pipe is obviously improved.(4)By analyzing the effect of three structural parameters of muffler—perforation rate of perforation tube,perforation radius and perforation number of spacer on attenuation performance,the structure of original muffler is optimized and an optimization scheme is formulated in this paper.Comparing transmission loss of muffler and noise of tail pipe before and after optimization,it shows that transmission loss after optimization is significantly improved,and the noise of tail pipe is improved very well,which indicats that the optimization design has a certain role in improving the attenuation performance of muffler.