Study On The Matching Of Exhaust System With Vehicle Based On NVH Performance

Exhaust system is a main source that affects the NVH performance of vehicle.Good NVH performance of vehicle mainly depends on reasonable match betweensubsystems. Therefore, the reasonable match of exhaust system with other subsystemis one of the key technologies for the design and development of exhaust system. Inthis paper, the matching of exhaust system with powertrain and car body waspresented. The main contents of this paper are as follows:1. The finite element model of exhaust system and simplified powertrain wereestablished. Their constraint modals and modal shapes were analyzed and the modalresults were verified by test. The result shows the finite element model of exhaustsystem which ignored the powertrain has good accuracy. Then, the influence of therigid-body modal of powertrain on the dynamic performance of exhaust system wasinvestigated. The result shows that the first-order Z-direction constraint modal ofexhaust system should steer clear of the the rigid modal of powertrain. Finally,considering the modal planning and decoupling ratio requirements, the power systemwas optimized.2. Test isolation method was applied to analyze and recognize the noisecontribution of exhaust system when a car was under the idle condition. Through theisolation of the radiated noise, tail pipe noise and structure noise, the structure noisewas diagnosed as the main source of the idle interior noise. Then the structure noisecontribution was quantitatively analyzed. Finally, an optimization program wasproposed to improve the idling noise of the car. The effectiveness of theoptimization program proved that the test isolation method can provide referencedirections for the matching of exhaust system with car body.3. When match the exhaust system with the noise and vibration of car body, amethod based on hybrid transfer path analysis was proposed. The method mainlyincludes these aspects: hybrid transfer path analysis, recognition of the contributionand the optimization of transmission path. This method was applied to solve thebooming noise problem of a passenger car under neutral gear WOT condition. Thetransfer path of exhaust system which contributed most to the interior acoustics wasfound and frequency response analysis was carried out to optimize the exhausthanger location. After optimization, the peak acoustic pressure value at30Hz of thedriver right ear position cut down5.2dB(A), sound pressure level response decreased 2.9dB(A). The subjective feeling of the booming noise disappeared, which provedthe effectiveness of this method.