Supersonic Boundary-Layer Combustion of Hydrogen with Porous and Multi-Porthole Injector Array Injection

An experimental investigation was conducted into the effectiveness of two novel boundary-layer fuel injector types, a porous plate and a multi-porthole injector array (MPIA), in initiating and sustaining boundary-layer combustion. These injectors were limited to a global equivalence ratio of 0.05 and fueled by hydrogen, which corresponds to a localized equivalence ratio within the boundary layer of approximately 0.86. High-speed schlieren imaging investigated the flow structure and compared the disturbances to the flow from each injector. Planar laser-induced fluorescence, alongside long exposure chemiluminescence imaging, was used to validate and determine the location and structure of combustion within the boundary layer. Heat transfer and pressure measurements characterized the flow with and without combustion. From the optical techniques, it was observed that the porous injector provided a more stable layer of combusting fuel within the boundary layer, minimally disturbed by turbulent flow structures. The MPIA had a more delayed ignition but more rapid local combustion immediately after ignition had been achieved. Heat transfer measurements indicated that combustion close to the wall was occurring at the start of the sensor plate but was either completing combustion or moving away from the wall near the exit of the experimental model.