Research And Improvement Of The Vehicle Exhaust System NVH Performance

With people’s environment consciousness and consumption consciousness changing, people put forward higher requirements on the car noise. People not only require the car ’quiet’, that is the noise should be small, and also ’harmony’, that is people also consider the frequency components and require it to bring the unique hearing. And the adjustment of the sound quality mainly depends on exhaust air intake system and the exhaust system. How to design exhaust system NVH performance in the early stage, make it match with the engine and vehicle, and let car, people and the environment achieve the harmonious, this is one of the key technology of the modern car energy saving and purify.At present domestic automotive product development is also in passive noise reduction stage, it depends on the physical model test and measurement technology and improvement. This serious lags behind automobile product development. In this paper the commercial vehicle’s noise is below standard, according to the noise source experimental data, the exhaust system is determined as the main research object. Acoustic model is built by GT-Power software, then the muffler’s transfer loss, exhaust system’s insert loss and the engine’s power loss is analysed, the exhaust system tailpipe noise target curve is set to make the tailpipe noise reach the target noise and meet the automotive exhaust muffler assembly technical specification through changing the muffler’s structure. At last the muffler’s radiation noise is predicted and controlled, this showed modification of the muffler can reduce shell radiation noise.Exhaust system hanger location is researched after changing the muffler’s structure. The original hanger location is set by the modal analysis. Then the hanger location is adjusted to make the hanger’s force as even as possible and the vibration transfered to the body accord with the target. At last the final solution of the hanger location is determined.NVH top-down design process for automobile exhaust system is put forward through the analysis of the exhaust system acoustic performance and the research of the exhaust system hanger location. This method designs NVH performance in the exhaust system development stage, it shortens the test time greatly and reduces development costs. Different from exhaust system noise traditional control, NVH top-down design process starts from the target, and also bases on sound quality demand of customer. Exhaust system NVH top-down design, is not only the important link of vehicle NVH design, but also reference for the other system NVH top-down design, and automotive NVH performance will overall upgrade finally.