Shock Wave Development and Propagation in Automobile Exhaust Systems 880082

For the purpose of exhaust noise reduction in an automobile engine, an experimental investigation was carried out to confirm the existence of shock waves in the exhaust system. Pressure measurments were conducted along the exhaust pipe of an in-line 4-cycle automobile engine, and the results clearly show that the compression waves at the exhaust port of the engine develop into the shock waves as they propagate in the exhaust pipe with the engine running at high speed. This nonlinear developing process of the shock wave was numericaly simulated using 2-dimentional unsteady Euler equations. Flow visualization study was also conducted using holographic interpherometer in order to prove the existence of shock waves in the exhaust pipe, and shock waves of Mach 1.1 were observed.

Consequently, it is found that the nonlinear effects in the compression wave development should be taken into account in the design phase of the engine muffler.