Numerical Simulation Of Acoustic Performace On Air Filters Of Vehicles

Energy shortage and environment problems are not only the bottlenecks in automobile industry, but also directly relates to national sustainable development strategy of normal implementation. Air intake system directly affects the engine power, fuel economy and noise levels. The research of high volumetric efficiency and low noise level of air intake system is the ultimate goal of designers. And noise regulations and vehicle performance of harshness (NVH) those double requirements put forward noise problems much more big challenge to air intake system. The exhaust noise reduced to an acceptable level, and on the basis of air intake system noise improvement is imperative.This article is a study about acoustic preformance of vehicles air filters through test combining simulation method. The study includes two aspects which are the aerodynamic noise and radiation noise of air filters. aerodynamics noise research is mainly based on the transmission and insertion loss of air filters.firstly,A test bench of Semi-anechoic chamber was built according to the national standard "GB/T4760-1995 acoustics-- measurement procedure for silencers"and the transmission loss of air filters was tested. Secondly, the insertion loss simulation of air filters was tested indirectly through an engine external characteristic performance test matching the target air filters. The above two work well provide the basis for the numerical simulation and boundary conditions.Aerodynamic noise simulation studies were mainly completed on the platform of the GT-Power. after verification test the transmission loss of model, the white noise signal and engine complex noise signals were used for transmission loss,both results are different, which objectively proved the optimized design of air filters based on transmission loss can not meet the real car needs.As a part of vehicles,air filters design must take into account the actual engine noise signals.The insert loss of air filters was simulated after the platform of engine modal completed.The results showed that empty filter silencing performance and engine speed exist certain relations. filter silencing effects are obvious in high speed but little in low speed. And air filters became "encumbrance," adding the resistance of the air in intake system. Based on this point, it is necessary to design a variable air filter modal which could balance its discretion of speed.finally, According to the high noise at individual band frequency of real car, This paper solved this problem by the design of Hemlthz resonance muffler.Air filter radiation noise simulation study was simulated on the platform of Sysnoise. the outside sound field was simulated through the finite element structure model and boundary element fluid model coupled to air filters.the results showed radiation noise at the top of the air filters was strong. The air filters modal analysis found that radiation noise and air filters of vibration model exist obvious correlation. It means big deformation may cause big noise radiation By using local strengthening structure made the air filters modals move to the high frequency and the radiation noise move to the high frequency,greatly reducing the low frequency phase of the radiation noise. And strengthen structure changed the original location of air filter radiation noise, and this point has directionality significance on subsequent jobs.