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The aim of the experiment is to observe the exhaust gas flow starting from the exhaust manifold to the catalytic converter at the 4 stroke engine of the passenger car to enhance the system's improvement. The manifold connects each exhaust pipe from the engine cylinders to the catalytic converter. The velocity pattern inside the exhaust manifold is measured using particle image velocimetry (PIV) meanwhile the time series velocity data is measured by Laser Doppler Anemometer (LDA). In the experiment, flow conditions with four pipes working simultaneously or single pipe working independently are tested. The initial velocity condition shown in the next is set at the upstream where the flow is inside the circular pipe. The initial velocity is 28m/s for the all pipes acting and 14m/s for each pipes acting. There are also 3 conditions of measurement: with catalytic converter, without catalytic converter and with hollow catalytic converter.

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.

Experimental studies were carried out on squeal of a two leading shoe type drum brake, the mechanism of noise generation was clarified, and consequently effective means were found to suppress squeal of 1000 to 4000 Hz frequency. The first approach was to examine the variation of natural frequency of the brake system components whole brake loading. Secondly, studies were focused on the correlation between squeal and the variation in the coefficient of friction and the sliding velocity of the brake shoe lining.