Study of Silencer Characteristics in a Gas Flow with Shock Wave : 1st Report, Propagation of Shock Wave in the Silencer

Abstract

In connection with the reduction of exhaust noise in automobile gasoline engines an experimental investigation was carried out on the initiation and propagation of shock waves in the exhaust gas flow. The pressure measurement along the exhaust gas pipe clearly shows a non linear transition of compression waves into shock waves. In order to obtain direct evidence of shock waves in the exhaust gas pipe, a holographic interfherometric flow visualization study was also conducted. Shock waves of Ms = 1.1 were observed. For the purpose of obtaining data for designing a silencer configuration which can effectively suppress a shock wave, shock tube experiments and numerical simulations were carried out. Resultsindicate that, in the design of silencers, the non linear wave propagation effect should be takeninto account and a double-chamber silencer is preferable.