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Experimental and Numerical Study on a Straight Exhaust Pipe

Published online by Cambridge University Press:  07 December 2011

S.-M. Liang  and
C.-J. Wang
S.-M. Liang*
Affiliation:
Department of Computer Application Engineering, Far East University, Tainan, Taiwan 74448, R.O.C.
C.-J. Wang
Affiliation:
Department of Mechanical Engineering, Far East University, Tainan, Taiwan 74448, R.O.C.
*
*Professor, corresponding author
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Abstract

In this study, radiated noise is investigated by experimental and numerical methods for a straight exhaust pipe of diameter 23mm that replaces the original exhaust pipe of a motorcycle of EZ 125cc provided by Kwang Yang Motor Co. In experiment, temperature, pressure and flow speed of the exhausted gas have been measured for different engine speeds ranging from 3000-5000rpm without loading. Sound pressure levels (SPL) at a distance of 0.5m from the exhaust pipe exit for different inclination angles (0° ∼ 90°) were recorded and compared with the result of simulation. In numerical simulation, a high-resolution 5th-order Euler solver was used and conducted on a parallel computation system with a cluster of 4 personal computers with dual processors. It is found that the back-and-forth reflection of expansion waves inside the pipe due to the shock wave diffraction around the pipe exit is the mechanism of radiating sound waves from the exhaust pipe. The numerical result shows the exhausted-gas flow with complicated vortex rings and its associated acoustic field. The acoustic field indicates that there are three sound lobes with different directivities for the engine speed of 4000rpm.

Keywords

Blast waveVortex ringEuler equationsSound pressure levelRadiated noise
Type
Articles
Information
Journal of Mechanics , Volume 27 , Issue 4 , December 2011 , pp. 597 - 605
Copyright
Copyright © The Society of Theoretical and Applied Mechanics, R.O.C. 2011

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