Effects of Groove Structure on Spray Characteristics of a Throttleable Pintle Injector

Throttleable rocket engines are used for various purposes, including vertical landing of launch vehicles and soft landing on the surface of celestial bodies. The use of a throttleable pintle injector is a representative throttling method because of its ability to maintain the spray characteristics under different throttling levels. However, previous studies have reported changes in the spray characteristics of gas-liquid pintle injectors with varying throttling levels. To address this issue, a pintle tip with groove structure was developed in this study. Cold flow experiments were performed using normal and grooved pintle tips for a gas-liquid pintle injector, and the spray angle and average droplet size of the pintle injector were measured and compared. By changing the momentum and structure of the radial flow with added grooves, the spray angle increased and the droplet size decreased. The results indicate that adopting a grooved pintle tip can improve the spray characteristics of a pintle injector in terms of its correlation with combustion performance, particularly at low throttling levels. Additionally, a grooved pintle tip reduces the changes in spray characteristics under varying throttling levels, which is advantageous from the perspective of design simplicity.