1996-08-01

A Study on the Relation Between Pulsating Flow and the Noise 961822

Behavior of pressure waves in exhaust pipes of a reciprocating internal combustion engine influences greatly the noise generated at the end of pipe.
To find the relation between the flow pattern throughout the exhaust pipe and exhaust noise, a pulsating flow through a pipe with and without a nozzle, the area ratio of the nozzle to the pipe being 0.25, was experimentally examined. The pulsating flow was generated by the rotary valve.
The pressure histories at each station along the pipe and the noise generated at the end of the pipe were measured against the different rotational speeds of the rotary valve. The pressures were differentiated with respect to time so that the intensity of the pressure waves was estimated, and wave diagram was constructed.
As a result, the relation between the increase and decrease in the intensity of the pressure wave and the rotational speed was found to be related to the arrival time of the compression waves at the rotary valve and the end of pipe. Intensity of the compression wave which is produced when the valve is about to open contributed most to the generation of the noise.

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