The pintle injector is a reusable, deeply throttable, and combustion-stable injection that has been widely adopted in modern liquid rocket engines. However, the effect of gas-film height on atomization in gas–liquid orifice type pintle (GLOP) injector remains insufficiently understood, motivating targeted numerical and experimental studies. In this work, high-fidelity numerical simulations are conducted for gas-film heights from 4 to 65 mm, complemented by atomization experiments at 4–12 mm. The results show that the gas-film height has only a minor effect on the atomization angle, which is primarily governed by the local momentum ratio. In contrast, increasing gas-film height includes a significant transition in the atomization morphology. For a narrow gas film, the spray exhibits a triangular distribution, whereas when the gas-film height ratio (W/D) exceeds 28, the atomization pattern progressively approaches that of subsonic liquid jets in crossflow, resulting in a logarithmic-like distribution. The Kelvin–Helmholtz (K–H) instability intensifies first and then weakening, similarly Rayleigh–Taylor (R–T) instability first grows and then gradually diminishes. For a fixed gas Weber number, the instability-wave frequency remains nearly unchanged. Although the average droplet size varies little, the Sauter mean diameter decreases rapidly before reaching a plateau, and the droplet field becomes increasingly uniform. Droplet velocity increases monotonically, accompanied by the disappearance of velocity stratification, and the droplet size–velocity distribution evolves from an “L-shaped” to a “triangular” pattern. The agreement between experiments and simulations validates the modeling approach, providing a foundation for the design of GLOP injectors for staged-combustion high-thrust engines.
Zhou et al. (Wed,) studied this question.