Breakup and Atomization Characteristics of Liquid Jets in Strong Swirling Crossflow Based on the VOF-LPT Method

Abstract

The liquid jet breakup and atomization interacting with a strong swirling crossflow is of significance in designing advanced aeroengines. The Eulerian-Lagrangian method was utilized to simulate the jet breakup and atomization processes. The volume of fluid (VOF) method was employed to track the gas-liquid interface topology evolution during the jet breakup, while the Lagrangian particle tracing (LPT) method was used to track the discrete droplets and obtain the information on far-field liquid dispersion. The crossflow was designed with different swirl numbers, ranging from 0 to 2.5. Momentum ratio q between the liquid jet and the air flow was set to 10, and the gas Weber number was 39. Under these conditions, both the column and shear breakups were observed. The results indicate that, the development of axial waves induced by the Kevin-Helmholtz (KH) instability was the main cause for column breakup. During the surface breakup, ligaments and small liquid jet branches were stripped from the liquid jet surface, primarily driven by azimuthal shear waves. The strong swirling airflow enhances the jet column breakup process, leading to a lower radial height for the breakup location and a shorter breakup time. However, as the swirl number increases, the radial height of the onset of breakup would increase, which suggests the swirl flow would delay the surface breakup of liquid jets. With the increase of the swirl number, the velocity component in the flow direction decreases, and the jet trajectory in the radial direction increases significantly. The deflection angle of the jet shows a linear relationship with the position of the flow direction, with larger air swirl numbers resulting in a steeper slope. Furthermore, as the swirl number increases, the Sauter mean diameter (SMD) of the entire spray field would decrease, and the liquid dispersion would increase.