Characterization of a Rotating Detonation Engine with an Air Film Cooled Outer Body

Rotating Detonation Engines (RDEs) and pressure gain combustion (PGC) present a pathway to increased performance and fuel savings due to improved thermal efficiency and power density. RDEs utilize detonations to combust reactants, which provides higher thermal efficiencies than deflagration combustion. This increase in efficiency comes from increases in total pressure achieved across the detonation front, whereas deflagrations produce losses in total pressure. However, high thermal loads have limited uncooled and conventionally manufactured RDE test duration. Currently there is a need to develop novel cooling schemes that minimize the associated performance penalty, provide adequate cooling to extend test duration, and characterize changes in RDE performance and operability. This investigation was aimed at quantifying film cooling when applied to the unsteady and adverse pressure gradient of a RDE. Two film cooled outer-body combustion liners were manufactured and tested using a H2-air operated 6-inch RDE with an aerospike plug nozzle, heat sink center-body, and a 0.64 inch detonation channel width. Additionally, a control liner without holes was manufactured and tested. The two film cooled liners varied film pressure drop to characterize changes in RDE operability, temperature response, and cooling manifold pressure unsteadiness. All liners used approximately equivalent total flow area, as well as diameter weighted axial and circumferential spacing to allow comparison. The combustion air injection area ratio was set to 0.33, and the nozzle area ratio set to 1.0 and 0.66 relative to the channel area. Combustion air manifold pressures, cooling air manifold pressures, cooling air temperature, combustion liner temperature, operating mode, detonation stability, and detonation wave speed were analyzed for an array of combustion air mass flow rates, equivalence ratios, cooling air mass flow rates, and liner geometries. A high-speed camera was utilized to confirm operating mode. Operability, temperature rise rate, and cooling air manifold pressure unsteadiness were analyzed. It was found that the introduction of film cooling air to the detonation channel significantly decreased stability and operability. The changes in stability and operability were found to be a function of the cooling air mass flow rate and equivalence ratio. Cooling air manifold pressure unsteadiness was found to be largely dependent on operation. The temperature rise rates decreased with increased cooling air mass flow