Affiliations: Department of Mechanical Engineering, Tokyo Denki
University, 2-2 Kanda-Nishiki-cho, Chiyoda-ku, Tokyo 101- 8457, Japan.
Abstract: This paper describes the noise generation in an exhaust system of a
reciprocating engine and focuses on the noise generated by shock/vortex
interaction. The pulsating flow through the exhaust pipe consists of the
compression and expansion wave, shock wave being generated by the non-linearity
of the compression wave at its head. The jet noise is produced when the
pulsating flow is discharged from the pipe end into atmosphere. The numerical
simulation based on a finite difference method and experiment were made, the
result of both of them being compared. First, the flow field in the pipe was
obtained to easily discuss the characteristic of the pulsating jet in terms of
the pressure history in the pipe. The jet structure was visualized by using
schlieren and shadowgraph techniques. Sound pressure measurements at various
locations were made in order to survey the directivity of the noise. The
comparison between the result of numerical calculation and experiment showed a
good agreement. A noise source related to shock/vortex interaction was
confirmed by the numerical study clearly.