Study On The Performance Experiment And Simulation Of Automotive Exhaust Muffler

In recent years, the production and sales of auto industry in our country grew veryquickly, relevant laws and regulations continuously improved, national standards and industrystandards constantly updated, people’s requirement of life quality also constantly rising. As abig public hazard of city life, car traffic noise problem drags the attention of people more andmore, so the requirement of automotive exhaust muffler performance is also becoming higher.In this paper, firstly，based on the national standard and the existing engine benchlaboratory, a performance experiment system was established for an automobile exhaustmuffler. The steady-state and transient experiments for the original exhaust muffler andequivalent straight pipe were performed and the data of exhaust back pressure and exhaustnoise sound pressure level were obtained. According to the experimental results, originalexhaust muffler’s insertion loss is greater than20dB(A) at low speed and noise eliminationeffect is very good; at the middle and high speed, the insertion loss decreases continuously, sothe noise eliminating performance becomes worse; at high speed, insertion loss is less than10dB(A), thus the noise elimination effect is poor. According to the noise spectrum, largerturbulence noise generates when exhaust air flows through the main muffler at the middle andhigh speed, which results in the reduction of insertion loss and noise elimination effect.Secondly,1D pipeline model of engine was established In GT-Power software and thenthe model was verified. Comparing the Power and torque data obtained by simulation with theexperimental results, the maximum error is within5%, which demonstrates that the enginemodel is qualified. The main muffler and auxiliary muffler were modeled in MUFFLERsoftware. Importing the.dat files of the mufflers into GT-Power,1D pipeline models could beachieved. Connecting the exhaust system model to the engine model by internal connectionmode, the whole simulation model was established and the exhaust pressure and transmissionloss simulation for the original exhaust muffler were conducted.Finally，the flow field and sound field simulation for the original muffler at5600rpmwere performed in Fluent software. The pressure distribution, velocity distribution andturbulent kinetic energy figure, noise cloud map of the main and auxiliary muffler wereachieved. According to the bench test data and the simulation analyses in GT-Power andFluent,6groups of improvement scheme were proposed to change the structure of the mainmuffler，in which transfer loss of scheme3was biggest and its exhaust back pressuredecreased a little, so scheme3was taken as the optimized design scheme for the originalmuffler and then the verification experiment was conducted. Experimental results show that both the noise elimination performance and the dynamic performance of the optimizedmuffler are greatly improved.