The impact of jet orifice configurations on atomization in gas-liquid orifice type pintle injectors

The pintle injector, valued for its combustion stability and structural simplicity, has been widely applied in commercial rocket engines. However, studies on the mechanisms and characteristics of atomization influenced by different orifice configurations remain insufficient, making modeling analysis urgently needed. In this study, high-fidelity simulations of Gas-Liquid Orifice Type Pintle (GLOP) atomization with height-to-width ratios (h/d) ranging from 0.5 to 8 were performed and compared with experimental observations. The results show that under the same Local Momentum Ratio (LMR), the h/d has a pronounced effect on the atomization angle, whereas the effect is weaker under the same momentum flux ratio q. The atomization field exhibits a distribution of high-speed small droplets, low-speed large droplets, high-speed small droplets along the jet height. With increasing h/d, the upper boundary of atomization transitions from an arc-shaped to a deflected form. Kelvin-Helmholtz (K-H) instability weakens and then intensifies (weakest for circular orifices), while Rayleigh-Taylor (R-T) instability intensifies and then weakens (strongest for circular orifices). The instability wave alternation frequency increased from 1666 Hz to 2500 Hz. In addition, the spatial and size distributions of droplets become more uniform, primarily due to changes in the dominant breakup mode, jet morphology, morphology of detached liquid fragments, primary atomization location, and overall flow-field structures. A unified correlation for atomization angle evolution was established for different orifice configurations. The consistency between experimental and simulation results validates the modeling approach, providing a solid foundation for the application of GLOP injectors with varying orifice configurations in high-performance liquid rocket engines.