A STUDY ON THE TRANSMISSION LOSS OF FLOW-THROUGH TYPE REACTIVE MUFFLERS

• Main Authors: Lo, Hau, 羅浩
• Other Authors: Chen， Y.N.
• Format: Others
• Language: zh-TW
• Published: 1994
• Online Access: http://ndltd.ncl.edu.tw/handle/15373026504218792104

博士 === 國立臺灣大學 === 機械工程研究所 === 82 === Ever since the invention of reciprocating internal (I.C.) engine, exhaust noise has been a major source of urban noise pollution. In recent years, consumer awareness as well as government regulations are encouraging the use of sophisticated design procedures to develop low engine exhaust noise as well as efficiency of engine performance. In order to guarantee good attenuation at the firing frequency (or any of its multiples),where the unattenuated pulsating noise resulting from I.C. engine is maximum, various geometrical configurations of the perforated elements (e.g., concentric-tube resonators, and cross-flow elements) have been developed. These configurations may be one of the straight- through types or the reversed-flow types. Straight-through type mufflers are normally preferred because they result in broadband frequency attenuation without significant increase in resistance to the flow of gas, whereas reversed-flow type mufflers are used when an exhaust system is being designed to achieve large amplitude, narrowband frequency attenuation as in the case of an I.C. engine that runs at constant speed. Generally, straight-through type mufflers offer low resistance to the flow of gases and, consequently, maintain lower engine back-pressures. These are, however, acoustically not very effective. Mufflers with flow reversals, on the other hand, offer increased attenuation but at the cost of higher engine back-pressures. Finally, some comments are offered on the design thumb of perforated element mufflers. By tuning the length and associate physical parameter to the in-situ case of various tubular elements, one can achieve rapid and economical modeling these that are frequently used in commercial reactive mufflers as well as in many other industrial applications. The aeroacoustic modeling ability is very useful for vehicular muffler designer especially in the preliminary design stage.