Analysis on the interactions of harmonics in exhaust pipes of automotive engines |
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Authors: | Min-Ho?Lee Joon-Seo?Lee Email author" target="_blank">Kyung?Ok?ChaEmail author |
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Affiliation: | (1) Graduate School of Mechanical Engineering, Myong-Ji University, 449-728, Korea;(2) Department of Mechanical Design, Chung-Cheong College, 363-890, Korea;(3) Department of Mechanical Engineering, Myong-Ji University, San 38-2 Nam-dong, 449-728 Yong-in city, Kyunggi-do, Korea |
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Abstract: | In exhaust pipes of automotive engines, the pulsating pressure waves are composed of fundamental frequency and high order
harmonics. The nonlinearities in the exhaust pipe is caused by their interactions. The error between prediction and measurement
is induced by the nonlinearities. We can not explain this phenomenon using linear acoustics theory. So power spectrum, which
is used in linear theory, is not useful. This paper is concerned with the development of useful engineering techniques to
detect and analyze nonlinearity in exhaust pipe of automotive engines. The study of higher order statistics has been dominated
by work on the bispectrum. The bispectrum can be viewed as a decomposition of the third moment (skewness) of a signal over
frequency and as such is blind to symmetric nonlinearities. The phenomenon of quadratic phase coupling (QPC) can be analyzed
by the bicoherence function. Finally the application of these techniques to data from actual exhaust pipe systems is performed. |
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Keywords: | Pulsating Pressure Waves Higher Order Statistics Bispectrum Quadratic Phase Coupling (QPC) Bicoherence |
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