Experimental and Numerical Study of Single Chamber Muffler

• Main Authors: Chien-Hung Liu, 劉建宏
• Other Authors: James Shih-Shyn Wu
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/99357553999179603766

碩士 === 國立中興大學 === 機械工程學系所 === 100 === Muffler is a common ancillary equipment in power machines. Transmission loss and the sound pressure distribution are key points of the improvement of the muffler performance and it’s structures. The experiment of estimating muffler performance is mature. It has numerous studies published related to the muffler design in the past two decades. In this study, we made a group of single-chamber muffler system and use the measuring instruments to read some basic experimental information first. Next, we build up a acoustic finite element model of the experimental muffler and use the self-developed FEAST acoustic finite element module to solve for a set of results. Finally, we compare the previous two sets of data to investigate the demerits of experiments and appropriate modification for the numerical simulation. In experiment, in addition to make a real object of single-chamber muffler pipe, the measurement equipments include full-range speakers, amplifiers, impedance tube, signal spectrum analyzer and two sets of microphones. During the experiment we can read the sound pressures from the spectrum signal analyzer in up and down pipes at the measuring locations. Then we use the Dipole Transfer Function to calculate the transmission loss of the muffler by such recorded sound pressures. Having completed with experiment, we build up a three-dimensional acoustic finite element model similar to the experimental muffler accompanied with appropriate boundary and loading conditions. After then, we use FEAST acoustic finite element FORTRAN module developed by Professor Wu to perform the numerical simulation analysis and to obtain the transmission loss of the muffler. Finally, results of transmission loss obtained from finite element analysis are compared with those from the experiments. Thus, we can not only understand the demerits of experiments, but also derive more information from the finite element models for purpose of design. In manufacturing high-performance mufflers, the study may provide powerful information to the engineer designers.