The Design And Simulation Research On Acoustics And Aerodynamic Performance Of Automobile Exhaust Muffler

The engine noise is the main source of traffic noise and exhaust noise of engine is the main noise source of engine. The main way to control engine exhaust noise is to install exhaust muffler. The acoustic performance is the transmission loss of the muffler, which reflects the noise elimination size of the muffler. The aerodynamic performance is the pressure loss of the muffler, which reflects the exhaust backpressure and the loss of engine power. This paper is aimed at an enterprise's engine noise and studies the two aspects of the muffler's acoustic performance and aerodynamic performance.At first, an acoustic finite element model of a single expansion chamber muffler will be built with traditional empirical formula and CAE technology, simulating its transmission loss through acoustic software and pressure loss based on computational fluid dynamics software Fluent.Secondly, in order to optimize the structure design of the muffler and meet the required performance time at the same time, we carry out a detailed research on the transmission loss and pressure loss of the basic unit structure of the muffler. The basic unit of muffler, such as the expansion ratio of the muffler, the number of the cavity, the length of the cavity, the layout and length of the inserted tube, the perforation rate, the number of the tail pipe and so on. The research shows that with the increase of the expansion ratio, the transmission of the muffler is gradually increased; with the increase of the expansion ratio, the pressure loss increases first, and then decreases and tends to be gentle after a critical ratio gradually. In this way, through we study the performance of transmission loss and pressure loss of other basic units respectively, which can pave the way for the design of the muffler structure.At last, through testing the exhaust spectrum noise of a certain type of engine, a muffler that satisfies the acoustic performance and aerodynamic performance will be designed. By comparing the muffler with different structures on acoustic and aerodynamic performance, optimizing the structural style, we will achieve the design requirements finally and provide an idea of design of muffler.