Comparison of Two Pintle-Style Hydrogen Injectors in a Rotating Detonation Combustor

This study presents a comparative analysis of two pintle-style hydrogen injectors in a rotating detonation engine (RDE) configuration for pressure-gain combustion applications. Using the National Energy Technology Laboratory’s water-cooled RDE test rig, the performance of wide-body (area ratio of 0.36) and narrow-body (area ratio of 0.55) pintle injectors was evaluated under varying flow and backpressure conditions. The equivalent available pressure (EAP), which is a key indicator of pressure gain, was estimated using capillary-tube-average-pressure measurements and isentropic flow assumptions. High-speed chemiluminescence imaging provided insight into wave dynamics, enabling automated determination of wave speed and count. Complementary large-eddy simulations using ANSYS FLUENT were performed to investigate the influence of injector geometry on internal flowfields and exit flow choking assumptions. The narrow-body pintle demonstrated an approximately 10-point improvement in pressure-gain performance, as indicated by the higher EAP across a range of conditions. Experimental results showed strong agreement with model predictions and comparable data in the literature, underscoring the importance of injector geometry in optimizing RDE performance. These findings contribute to the design of hydrogen-fueled RDE systems aimed at increasing gas turbine efficiency through pressure-gain combustion.