ACOUSTIC BEHAVIOR OF SHORT ELLIPTICAL CHAMBERS WITH END CENTRAL INLET AND END OFFSET OR SIDE OUTLET

摘要

The elliptical chamber is a commonly used silencer configuration in the breathing system of engines. Yet, with the exception of a few recent investigations, its acoustic behavior has not been studied in detail. Denia et al. [1] apply the finite element method (FEM) and the point source technique to analyze such configurations. They provide comparisons with the circular case and some experimental results, establishing that the eccentricity has an important effect on the acoustic performance. In an attempt to represent the production exhaust and tail pipe locations that are usually on the major axis of an ellipse, the authors have considered only the cases with end offset inlet/outlet. The side inlet and outlet ports, on the other hand, are known to modify the acoustic behavior drastically for circular configurations [2, 3]. Therefore, the present study investigates the effect of side ports in elliptical configurations, including the angular locations over the outer surface. The effect of the location of end outlet ports (minor versus major axis) is also examined. The investigation is confined to short chambers, where the transverse propagation dominates [4, 5]. The experimental transmission loss for one selected configuration is shown to agree well with the FEM predictions.