Simulation And Optimization Of Muffler Base On Temperature Field

The noise level directly affects the comfort of the passengers. Higher ridingcomfort requirement from customers and more and more intensive marketcompetition focus the manufacturers’ attention to the importance of the vehicles’comfort. As the main source of Vehicles, the exhaust noise became one of themost important factors of vehicles NVH control. To control the exhaust noise, themost effective method is to use the exhaust muffler to reduce its acoustic pressurelevel. During the developing process of exhaust muffler, using computers tosimulate the performance of the mufflers can shorten the developing period andreduce the develop expense.The1-D sound analysis have been widely used in engineering, however theaccuracy can not meet our demand when the frequency is high. Temperatureaffects the muffler’s performance heavily. During the simulation, temperature isusually assumed as it is constant or change linearly, which greatly influence theaccuracy of the simulation result.Virtual-lab is applied as the basic tool and first the finite element methodwas applied in the prediction of a normal muffler structure and the transferadmittance was adapted to show the perforated structure with no flow, and theinfluence of structure and temperature was analyzed.Based on the model which coupled the temperature field and the acousticmesh files, the transmission loss of the vehicle muffler under different workconditions was calculated. An improved structure was developed to solve thenoise problem under idle condition. Then the transmission of the improvedstructure was calculated. The simulation result shows that the muffler’stransmission loss between20-500Hz increased a lot and the muffler’s silencingperformance in low frequency improved greatly. The engine-muffler coupledmodel was built for both the structures before and after the improvement inGT-power. The calculation result of the tail pipe noise shows that the acousticpressure level of the improved structure reduces in the whole speed range. At the speed of2800rpm, the tail pipe noise reduced from93.5dB to89.6dB after thestructure improvement.The muffler before and after improvement was load to the car and the noiseexperiment of both was carried out. The experiment result shows that theimproved structure can reduce the vehicle noise was reduced effectively and thesound pressure levels excessive problem at the middle and rear seat tail pipe wassolved. The noise between the stalls full throttle acceleration period reduced.