Pintle Injector Performance Sensitivity to the Radial Injection Arrangement

Pintle injectors represent a promising technology in the realm of space access, owing to their unique capabilities for thrust modulation and combustion stability. Furthermore, their suitability for reusability and cost-effective manufacturing makes them an attractive choice for future space propulsion systems. This study focuses on an oxidizer-centered pintle injector engine fueled with gaseous methane (GCH4) and liquid oxygen (LOx), utilizing two rows of radial rectangular slots. We investigate the impact of varying the mass flow rate ratio between these two rows of injectors on the flame topology and combustion efficiency. The analysis is performed through a series of three-dimensional reacting multiphase unsteady Reynolds-averaged Navier-Stokes simulations relying on finite rate chemical kinetics and the Eulerian-Lagrangian approach. When the mass flow rate of the secondary injectors exceeds that of the primary injectors, a distinctive impact on the interaction among gas, liquid, and reactive processes is observed. When most of the oxidizer is injected from the primary injectors, the annular flow reaches the pintle head, cooling it effectively. At the same time, this significantly affects combustion efficiency. Conversely, an increase in the mass flow rate in the secondary injectors allows for the radial jets to divert the annular flow, enhancing both mixing and combustion efficiency at the cost of significantly elevated temperatures at the pintle tip. The pronounced influence of the mass flow rate ratio on critical performance parameters, such as combustion efficiency and thermal loads, underlines the importance of managing this variable at the design level.