Jet mixing manipulation with asymmetric orientation of tabs

Abstract

The jet mixing caused by two rectangular and triangular tabs of geometric blockage 2.5% each, separated by 90⁰ at the nozzle exit plane of a Mach 2 circular jet, in the presence of varying levels of expansion, corresponding to nozzle pressure ratio (NPR) 4–8, was investigated experimentally. The relative mixing promoting capability of these tabs was assessed. It is found that the rectangular tabs at 90⁰ interval retards mixing for NPRs 4, 5, and 6, and promotes mixing at NPRs 7 and 8. Comparison of the present result for rectangular tabs at 90⁰ interval with that of Arun Kumar and Rathakrishnan 8 for 180⁰ interval shows that the mixing promoting capability of 90⁰ and 180⁰ intervals are comparable, at NPR 7. But at NPR 8, the mixing performance of rectangular tabs at 90⁰ interval is better than 180⁰ interval. For NPRs 7 and 8, the core length reduction due to rectangular tabs at 90⁰ and 180⁰ are 26% and 36%, and 28% and 26%, respectively. On the contrary, the triangular tabs at 90⁰ interval promote mixing at all NPRs of the present study. The mixing caused by triangular tabs at 180⁰ interval reported in literature 8 is only marginally better than triangular tabs at 90⁰ interval studied in this work. For NPR 4, 5, 6, 7, and 8, the core length reduction caused by triangular tabs, at 90⁰ and 180⁰ intervals, are 24%, 58%, 69%, 80%, and 76%; and 38%, 65%, 77%, 87%, and 85%, respectively.