Simulation on atomization process of gas–liquid pintle injector in LRE under periodic conditions based on the VOF to DPM method

To study the atomization characteristics of a liquid–centered gas–liquid pintle injector under periodic operating conditions, the gas–liquid interaction, breakup dynamics and spray morphology of the pintle element are simulated based on the three–dimensional volume of fluid to discrete particle model (VOF to DPM) and octree adaptive mesh refinement (AMR) when the liquid jet velocity changes according to sinusoidal law. The simulation results show that: (1) The fragmentation mechanism of liquid jets under periodic operating conditions can be divided into column breakup caused by Rayleigh–Taylor (R–T) instability and surface breakup caused by Kelvin–Helmholtz (K–H) instability. (2) Under specific operating conditions, the “flow interruption” phenomenon occurs. When the variation amplitude of liquid jet velocity increases from 3.125 m/s to 12.5 m/s, the occurrence time of “flow interruption” decreases by 10.46%, the spread angle increases by 36.79%, and the dimensionless length of liquid jet before “interruption point” decreases by 59.89%. (3) Additional disturbance waves occur due to the klystron effect. The gas–liquid interaction increases at the location where liquid flow accumulates. When the variation frequency of liquid jet velocity increases from 8 kHz to 16 kHz, the reduction amplitude of λ₁, λ₂ and λ₃ is all around 50%.