Influence Of Structural Parameters of Planar Adjustable Pintle Injector on Flow and Mixing Characteristics

Abstract

The pintle injector is widely employed in propulsion systems owing to its simplicity and high performance. While fixed-geometry designs have been extensively investigated, the impact of structural parameters on adjustable configurations remains unclear. This study conducted experimental and numerical investigations of a planar adjustable pintle injector. Experimentally, spray behavior was analyzed at different throttling rates, capturing spray patterns and angles under various conditions. Numerically, the effects of orifice width, blockage factor, and skip distance on spray development and mixing performance were evaluated. The reliability of the simulation approach was verified through comparison with experimental data. Results revealed that reducing the orifice width blurred the boundary between the kerosene liquid film–dominated area and the crushing and mixing zone, while it slightly increased spray angle, enhanced inter-orifice vortex intensity, and improved kerosene utilization, from 0.443 at 3.6 mm to 0.756 at 1.2 mm. Increasing the blockage factor expanded the kerosene liquid film zone, contracted the mixing zone, fragmented the liquid film structure, accelerated jet deformation, reduced the spray angle, and increased kerosene utilization from 0.562 at 0.35 mm to 0.734 at 0.45 mm. By contrast, variations in skip distance had a negligible influence on spray structure and mixing efficiency, causing a minor increase in spray angle and stable kerosene utilization rates (fluctuating between 0.607 and 0.617, <1% variation as the skip distance increased from 0.048 to 0.12). The findings contribute to the design optimization and performance enhancement of adjustable pintle injectors, facilitating deep, efficient, and stable throttling for rocket engines.