This experimental study aims to investigate the decay characteristics of larger-lipped circular and noncircular supersonic jets. The supersonic jet in this study was emitted from a convergent-divergent nozzle with three exit geometries: circular, elliptical and rectangular. All three nozzles were designed with an identical exit area of 108 mm2 and an exit Mach number of 1.8, respectively.
Centerline pressure decay, lateral pressure distribution, Pitot pressure gradient and shock structures were presented. Schlieren flow visualization has been extensively used to capture the shock cell structure of the different jet configurations.
The centerline pressure decay of the supersonic jet with larger lip thickness of rectangular cross section nozzle shows a significant reduction in the supersonic core length compared to the elliptical and circular case. This reduction in the supersonic core length is primarily attributed to the formation of a corner vortex from the noncircular jets.
To carry out a larger number of data runs, the run time of the compressor system becomes more critical. Hence, the experiments were performed only for the overexpanded and nearly correctly expanded cases.
Supersonic noncircular jets have numerous applications in aerospace, automobile and manufacturing engineering. Understanding the flow field of these jets will assist engineers and scientists in enhancing performance, particularly in applications such as jet mixing characteristics in fuel injectors and noise reduction in exhaust nozzles.
Experiments were performed for overexpanded and nearly correctly expanded nozzle pressures ratio of 3.6 and 5.5, respectively. Three different nozzle geometries such as circular, elliptical and rectangular cross section exits were considered. In this study, the lip thickness of the nozzles is set as 1.9 times the hydraulic diameter for all nozzles.
