Liquid jet breakup behind a pylon in supersonic flow

Abstract

The thin pylon has been found to be one of the most promising hypermixers, offering enhanced mixing of fuel with minimum pressure loss. In the present study, the effect of pylon height and the angled injection on the liquid jet breakup and its effect on atomization in a free stream of Mach 1.71 has been studied experimentally. Acetone is used as the liquid medium to characterize the liquid jet injection in supersonic flow. Acetone is injected into the flow in the transverse direction behind the pylon at different mass flow rates for 3 different pylon geometries and 3 angled injection cases. The height of the pylon is varied (17.32 mm, 10 mm, 6 mm) and the injection angle is such that it impinges against the pylon wall at three different angles of 30°, 45° and 60° while maintaining the other geometrical features to be the same. The study includes Schlieren imaging to find the effect of liquid injection and Pylon on the compressible flow field, and Shadowgraphy visualization was employed to evaluate the jet disintegration and atomization; Mie Scattering visualization techniques were used for evaluating the lateral spread of liquid jet spray. Mathematical techniques such as temporal variance, POD and DMD are used to analyze the temporal behavior of the jet spread. It is observed that the pylon height not only increases the penetration height but also has a significant effect on the jet breakup and atomization. The shear layer also plays a major role in jet atomization and penetration height. Angled injection case was observed to perform better than transverse injection in terms of penetration height and jet spread.