Computational Fluid Dynamics Analysis of Flow Field of Different Hybrid Rocket Engine Oxidizer Injector Designs

Hybrid rockets have constantly gained attention due to their numerous advantages compared to solid and liquid propellant rocket motors. Although hybrid rockets attract due to its throttling capabilities, it is also challenged for its low specific impulse and low regression rates which affect the rocket’s combustion efficiency. Due to the identified issues, it is shown that the flow pattern of the oxidizer has a significant effect on the hybrid rocket motor’s performance. This study focuses on the analysis and comparison of flow field of a hybrid rocket motor using nitrous oxide (N\boldmath$_2$O) as oxidizer. Different oxidizer geometry designs namely, showerhead, hollow-cone, and vortex injectors were analyzed using computational fluid dynamics. The flow patterns and the velocity distributions of the oxidizer along the combustion chamber, 50\% of port radius distance from the combustion chamber centerline and along the fuel grain surface were investigated. Results showed that the vortex injector design had significantly higher velocities for the nitrous oxide flow. Higher velocities are desirable for oxidizer flow to minimize boundary layer during combustion. This work is intended as a preliminary investigation focused exclusively on the oxidizer flow field. Combustion and regression behavior are not simulated directly, the study emphasizes how injector geometry influences boundary layer behavior and velocities near the fuel grain surface. The results are intended to guide early-stage injector design selection and inform future experimental validation.