Atomization dynamics of gas-liquid orifice type pintle injectors at different throttling levels

The pintle injector, valued for its simple structure and wide throttling range, is widely employed in liquid rocket engines. However, the atomization characteristics of Gas-Liquid Orifice Type Pintle (GLOP) injectors under varying throttling conditions remain insufficiently understood. This study uses high-fidelity simulations to examine GLOP atomization over a range of gas-film Weber numbers (Weg). With increasing Weg, interfacial instability shifts from Rayleigh–Taylor (R–T) dominance to surface waves driven by Kelvin–Helmholtz (K–H) instability, accompanied by a denser spray and more confined ligament distribution. Across different throttling levels, the atomization exhibits periodic evolution with corresponding frequencies of 1000, 1666, 5000, and 20000 Hz. Despite substantial variations in liquid profiles, gas-film structures, and vorticity fields, the Column Breakup Location (CBL) remains nearly constant. Four breakup modes and four atomization morphologies are identified, linked to distinct Weg and Local Momentum Ratios (LMR), with the Penetrated and Deflected Jet yielding the best atomization performance. Droplet statistics reveal fine, high-speed droplets within the inner gas film and larger, slower droplets outward. As Weg increases, droplet size–velocity patterns transition from “L-shape” to “triangular,” showing smaller, more uniform droplet sizes and higher velocities. The strong agreement between simulations and experiments validates the compressible VOF–LPT model, offering guidance for deep-throttling GLOP injector design in reusable rocket engines.