Muffler Performance Analysis Based On Finite Element Method

With the rapid development of Engineering Machinery, Manufacturing technologies and user experience of the heavy machinery equipment are required to provide a new criterion.The noise pollution becomes much more serious, thus people take a high attention to control the noise. The noise of Engineering Machinery is mainly come from the engine. The most efficient method is to install an exhaust muffler. An exhaust muffler has a simple structure and a good performance in low and middle frequency band, which can give a convenient way to engineer noise. So the study of muffler will have a real value. In this paper, we will use theoretical and simulated analysis method to study the muffler in dump trucks.The main contents of this paper is to optimize structure parameters of prototype muffler using Three-dimensional simulation software LMS_Virtual_lab_Acoustics and Fluent. Firstly,we introduced the theoretical basis of muffler design. In order to determine the direction of muffler optimization, we identified five evaluation index of muffler performance. To get the point how the structural parameters effect transmission loss and pressure loss, we study the simple muffler units, such as expansion proportion, expansion chamber length, the length of inserted pipe, the form of inserted muffler, the perforated diameter and the rate of perforated muffler. Then we focused on the acoustic properties of the prototype muffler. We found that the transmission loss according to the simulation results cannot meet the requirements which is lower than 10 dB in middle or higher frequency band. Therefor, we make some change on the original structure of prototype muffler. The method we take is to add a perforated baffle in the two large expansion chambers. According to the simulation results, the acoustics performance in the middle and higher frequency band has been significantly improved. In the end, we research the distribution of the flow field inside the muffler. From the pressure imagery, it’s obvious that the pressure gradient is small and the back pressure is 5.245 kPa which can meet the design requirement. Finally, the final optimization method on the muffler is remove the perforation structure on the tail pipe, increase a perforated baffle in expansion chambers and add sound-absorbing material.The innovation of this paper is to simplify the complex structure muffler into three simplestructure muffler series. By comparing the transmission loss of each chamber and the whole muffler, we derived that we can reduce the noise when removing perforated structure on the tail pipe. The final optimization method is to add a perforated baffle in the two larger intermediate expansion chamber and remove the perforated structure on the tail pipe.According to the simulation results, the method is effective and suitable.