Radial Mass Flow Rate Partition on LOx/GCH4 Pintle Injector Configurations

This study focuses on an oxidizer-centered pintle injector engine fueled with gaseous methane (GCH4) and liquid oxygen (LO𝑥 ), using two rows of discrete radial injectors. The impact of varying the mass flow rate ratio between these two rows of injectors on flame topology, chamber pressure, and combustion efficiency was investigated through a series of three-dimensional reacting unsteady Reynolds-averaged Navier–Stokes simulations relying on an optimized skeletal mechanism and the Eulerian–Lagrangian approach for the evolution of liquid droplets. When most of the oxidizer is injected from the primary injectors, the annular flow reaches and cools the pintle head, thereby negatively affecting the combustion efficiency. Conversely, increasing the mass flow rate of the secondary injectors allows 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. When the mass flow rate of the secondary injectors exceeded that of the primary injectors, a distinctive impact on the interaction between the gas, liquid, and reactive processes was observed. Furthermore, pressure oscillations inside the chamber were observed when the blocking effect of the secondary injectors became relevant. These oscillatory phenomena appear to be related to hydrodynamic mechanisms and their interaction with intrinsically oscillatory combustion processes.