This paper outlined the noise generation mechanism of high frequency intermittent noise during deceleration and of high frequency noise when the engine is under load in a dual-thin-wall 4-1 manifold, by exhaust gas pressure measurements, analysis on an actual engine, and CFD. (1) This research demonstrates that high frequency intermittent noise during deceleration is caused by reverse flow in the exhaust manifold. Elimination of the gap at the edge of the ports of the dual-wall manifold reduced the level of negative pressure waves, thus reducing the generated noise level. (2) This research demonstrates a correlation between the impact of the gas flow against the exhaust manifold chamber wall and the generation of high frequency noise when the engine is under load. Modification of the port exit shapes and the chamber (angle of incidence of the ports) changes the gas flow, thus reducing the high frequency component of exhaust pressure fluctuation. The development of a noise reduction method to reduce excitation force enabled the achievement of a noise level equivalent to that produced by a 4-2-1 exhaust manifold while retaining a low heat-mass structure.
Research on reduction technology of high frequency noise in low heat-mass 4-in-1 exhaust manifold
Forschung zur Reduzierung des Hochfrequenzlärms eines doppelt-dünnwandigen 4 auf 1 Abgasrohrkrümmers
Review of Automotive Engineering (JSAE) ; 27 , 4 ; 559-564
2006
6 Seiten, 17 Bilder, 4 Quellen
Aufsatz (Zeitschrift)
Englisch
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