Elliptical Tabs as a Mixing Enrichment Tool for Jet Nozzles

Abstract

Mixing efficiency helps to thrust gain and jet noise reduction. Aerospace and aviation research communities around the world are constantly demanding cleaner, quieter and more efficient commercial aircrafts. Though there are many sources of noise during flight, one such is deficient mixing of air at the rear of the nozzle, uneven expansion of nozzle and corresponding engine noise is quite dominant. The mixing proficiency is achieved by mixing of cold air at the surroundings with the hot air that exits through the nozzle. To reduce the engine noise, elliptical tabs are employed at the exit of convergent nozzle. These are passive noise controllers which create vortices to the existing flow and entrains cold mass from the surroundings in order to reduce noise level. This paper is concerned with the various shapes and sizes of tabs to test the mixing efficiency at different Mach numbers. Further, it is evaluated by both qualitative and quantitative analysis of shadowgraph system and the pressure identifying method using some of the propitious pressure scanner.