Liquid and aerated jets behind different pylon configurations in supersonic crossflow

Abstract

Effects of different pylon configurations on the liquid and aerated jets injected in supersonic crossflow of Mach number 1.65 were investigated experimentally. Pylon configurations with different bottom curvatures at the trailing edge were explored. Two liquid jets with momentum flux ratio of 0.1 and 0.4, and two aerated jets with gas-to-liquid mass ratio of 2% and 4% were selected in the current study. Acetone and air were used as the secondary liquid jet and the aeration gas, respectively. For the atomization quality of the jet, the droplet velocity field was obtained using fluorescence-based particle image velocimetry. The high-speed shadowgraph and cross-sectional planar laser-induced fluorescence experiments were performed for the mixing characteristics, such as penetration height and spreading area. The high-speed images were also used for the dynamic mode decomposition, which revealed dominant structures and their associated frequencies. Curved pylons with 45°and 60°trailing edge curvatures produced higher droplet velocity distribution than the other cases for liquid and aerated jets, respectively. The penetration height of the liquid jet at low momentum flux ratio tends to traverse towards the wall downstream of the injection. Aeration substantially improves the penetration height for the same liquid flow rate due to the annular nature of the aerated jet with a gas-to-liquid mass ratio of 2%. Cross-sectional planar laser-induced fluorescence results revealed a considerable increase in the spreading of the jet for the aerated jets as compared with the low momentum flux ratio liquid jet. This was due to the higher shear layer interaction of the aerated jet than that of the liquid jet. The aerated jets produced 60% higher spreading area than the liquid jet with the same mass flow rate. The curved pylons exhibited at least 10% increment in the spreading area as compared to the standard pylon cases for all the liquid and aerated jets. Three distinct modes were observed in the DMD analysis. The convective mode was the typical first and second modes of all the cases. The shear layer flapping and shear-induced entrainment breakup modes have also been observed with frequencies around 5 kHz.