Research On Optimization Of Engine Exhaust Noise Based On Numerical Simulation

Noise pollution,together with air pollution and water pollution,is currently recognized as the three major environmental hazards in the world and seriously affects people's normal lives.Among them,automobile noise has become the primary source of noise in modern cities.In the face of increasingly stringent national laws and regulations on automobile noise and people's increasing demand for automotive noise control,engine exhaust noise,as one of the main noise sources of automotive noise,has also received increasing attention.The research work in this paper combines specific engineering problems encountered in engineering projects such as excessive engine idle noise and excessive exhaust muffler power loss.And based on engine exhaust noise control,the method of engine exhaust noise generation mechanism,control method and numerical simulation & optimization was studied in depth.Then,using GT-Power engine simulation analysis software and its pre-processing tool GEM3 D,the whole engine and the exhaust muffler were modeled and simulated,and the model was calibrated through the test data to be used for simulation & optimization of engine exhaust noise.Based on the calibrated GT-Power simulation model,through simulation analysis of the exhaust noise of the original engine,it was pointed out that the excessive engine idle noise of the original engine was mainly caused by the unreasonable matching of the acoustic structure design of the exhaust muffler.Then the key factors,which affected the exhaust noise of the engine,were analyzed in depth.Through the analysis of the connection structure of multiple basic muffler units of the muffler and the influence of exhaust temperature,exhaust pipe diameter,and exhaust tail pipe length on the exhaust noise,it can be found that,for the exhaust muffler,The units with different frequencies of anechoic can be designed,to expand the band of frequency of noise elimination in series and increase its noise attenuation performance by reasonably designing the distance between the series of the silencer units;The exhaust temperature has a great influence on the noise attenuation performance of the exhaust muffler,and with the higher temperature gradient of the exhaust system,the influence of the exhaust temperature gradient should be fully considered in the exhaust muffler design;Reducing the exhaust pipe diameter can reduce the exhaust noise at low engine speed,while the exhaust noise will be increased at high speed and high load conditions.And the tendency of flow noise generation and exhaust muffler power loss will be increased.By increasing the tailpipe length,the engine exhaust noise can be significantly reduced.With the exhaust muffler be designed,we can satisfy the acoustic design goal by increasing the length of tailpipe appropriately.Based on the analysis of the key influencing factors of engine exhaust noise,and through the reasonably design of the exhaust muffler,the engine idling exhaust noise in the engineering problem is reduced by 6dB compared with the original machine,and the maximum power loss is controlled within 10%,which meet the design requirements and was finally verified by test.In this paper,the GT-Power numerical simulation method is used to guide the optimal design of engine exhaust muffler,and it has achieved very good practical results,shortened the development cycle,saved development costs,and has important guiding significance for engine exhaust system noise control.