Methodology for Exhaust System Design Optimization for Light Weight Passenger Vehicles 2019-26-0269
While designing the exhaust system of passenger car on one hand there is stringent emission regulations, packaging constraints, high NVH performance requirement. On the other hand with light weight vehicle design there is tremendous pressure on weight reduction of exhaust system while keep the same NVH performance levels. Exhaust system consist of muffler, bellows, pipes and hangers. For muffler design both acoustic (transmission loss, pass-by noise, tail pipe noise etc.) and non-acoustic (back pressure) parameters needs to be considered.
In the current paper, methodology for muffler design optimization using 1D acoustic simulation software is presented. The baseline exhaust design consist of two mufflers; main muffler and post muffler. Simulation methodology is developed to optimize main muffler design in order to eliminate post muffler requirement while achieving the same performance of baseline exhaust design. For this purpose a DOE study is conducted by varying primary muffler internal pipe dimensions, baffle location, perforation etc. to achieve transmission loss (TL) and back pressure (BP) of the baseline design.
Based on simulation study a physical prototype is made for optimized exhaust design consisting of only main muffler (with modified design compared to baseline main muffler). Transmission loss and back pressure is measured physically and confirmed that the optimized exhaust design is able to deliver the same NVH performance as that of the baseline exhaust design. Furthermore a vehicle level physical test is conducted to compare the pass-by noise for optimized exhaust design and compared with baseline exhaust design. It is observed that the optimized exhaust design with one muffler is able to maintain the same pass-by noise level as that of the baseline exhaust design with two mufflers.