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Computer-aided Engineering Technique for the Reduction of Exhaust System Noise and Back Pressure

Article of Honda R&D Technical Review Vol.13 No.1

Summary

A technique has been established for predicting the effects of changing cold end parts in an exhaust system on engine output and exhaust discharge noise. This technique enables the sharing of such parameters as velocity and pressure due to the application of flow analysis and acoustic analysis. One-dimensional compressible fluid analysis was used to predict engine output, and a value derived by steady flow analysis using the three-dimensional finite volume method (FVM) was introduced for the effective flow area, which is one of the parameters. Further, it was clarified that exhaust discharge noise is determined by the sum of pulsating noise and flow generated noise. The pulsating noise was predicted by the application of acoustic analysis using the three-dimensional finite element method (FEM). For the FEM input boundary conditions, precision verification was carried out using both pressure fluctuation values derived by compressible fluid analysis and measured values from an actual vehicle, while velocity derivable by steady flow analysis was introduced as a parameter for flow-generated noise prediction. As a result, it was possible to predict the variations of engine output caused by changes in the exhaust system with an accuracy of ±2%, and to predict exhaust discharge noise within ±2 dB. This has made it possible to optimize muffler design by implementing three-dimensional computer-aided design (CAD) modeling to evaluate parts performance from the initial layout investigation stages.

Reference

(1) M. Murakami, et al.: Pipe Line and Duct Fluid Resistance (revised version), Tokyo, The Japan Society of Mechanical Engineers, 1998, p. 3 – 64.
(2) T. Toi, et al.: Development and Application of an Automotive Exhaust System Speaker Vibration System, Chuo University, Preliminary Papers of the Automotive Technology Conference 973, p. 89 – 91 (1997)
(3) Y. Kagawa: Noise and Vibration Engineering using the Finite Element Method, Tokyo, Baifukan, 1981, p. 255 – 266
(4) T. Takenaka et al.: Flow Measurements, Tokyo, The Japan Society of Mechanical Engineers, 1994, p. 166 – 173

Author (organization or company)

Satoshi WATANABE(Tochigi R&D Center)、Tsuyoshi ISHII(Tochigi R&D Center)、Hidekazu AKIYAMA(Tochigi R&D Center)

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