Spray characteristics of pintle injector with high gas-liquid momentum ratio

Abstract

Experimental and numerical simulation methods were employed to investigate the spray characteristics of a pintle injector under high gas-liquid momentum ratio conditions. In the experiments, water and nitrogen were used as the working media. The spray angle and spray modes were investigated using background light imaging and dynamic mode decomposition techniques. Numerical simulations were carried out using a three-dimensional Volume of Fluid to Discrete Particle Model (VOF to DPM) to explore the spray field configuration, Sauter Mean Diameter (SMD) of droplets, and droplet distribution. The results indicate that the spray pattern of the high momentum ratio gas-liquid pintle injector is distinct from that of the traditional hollow cone, presenting as a solid cylindrical spray with reduced size and lower turbulence levels in the recirculation zone. An empirical formula was derived for the spray angle, expressed as $\theta =32{\left(\frac{M}{\sqrt{\text{We}}}\right)}^{-0.63}$, incorporating the Weber number as a significant factor influencing the spray angle. Furthermore, the spray modes were classified into three types based on the gas-liquid momentum ratio (M) and Weber number (We), and their oscillation patterns were analyzed individually. The M was found to significantly influence the droplet diameter and distribution: a higher ratio resulted in a smaller droplet size but also led to droplet accumulation below the injector's central axis, potentially compromising the thermal protection of the pintle tip.