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Aeroacoustic studies of beveled and asymmetric-chevron nozzles
Date Issued
01-12-2009
Author(s)
Tide, P. S.
Indian Institute of Technology, Madras
Abstract
Experimental investigations have been carried out on beveled and asymmetric chevron nozzles to assess the influence of beveling the flow on noise reduction benefits. Acoustic measurements such as overall sound pressure level, spectra and directivity of sound pressure have been carried out for the nozzle configurations over a range of nozzle pressure ratio from 1.5 to 5, that corresponds to fully expanded jet Mach number varying in between 0.75 and 1.70. Shadowgraph images of the shock-cell structure of jets from round, bevel and asymmetric chevron nozzles have also been captured for different nozzle pressure ratios and compared. These images clearly show flow vectoring in the direction of shorter lip for the beveled nozzle and towards the longer chevron lobes for the asymmetric chevron nozzle. Of the geometries studied, asymmetric chevron nozzle gives the maximum noise reduction, especially at higher pressure ratios. Bevel nozzle gives marginal noise reduction for all emission angles when compared with baseline round nozzle. Asymmetric chevron nozzle is found to be free from screech unlike round and bevel nozzles. The directivity measurements show that the asymmetric chevron nozzle is directive at 50°, whereas round and bevel nozzles are directive at 30° when the measurements are taken in such a way that the jet exit corresponds to 0°. Copyright © 2009 by the American Institute of Aeronautics and Astronautics, Inc.