Channel Width Impact on RDE Performance with Fuel Injection Parity

The influence of viscous forces and heat transfer in rotating detonation engines can directly result in a significant loss in measured system performance. Both loss terms scale with the combustor surface area and their relative impact on performance can be reduced by increasing the combustor volume-to-surface area ratio per unit length. This was observed by increasing the engine channel gap width, but could also be achieved by decreasing the overall system length. Fuel injection for all configurations occurred at the mid-gap location and utilized an injector designed to deliver nearly identical mixing in a nominal 145 mm centerline diameter rotating detonation engine with channel gap widths of 7.62 mm, 11.43 mm, and 19.0 mm. The back-pressurization of the system was designed to be able to support testing of three nozzle restrictions and provide the required base drag pressure readings to determine the equivalent available pressure and resulting pressure gain across the system for the multiple configurations using two complementary techniques. The multiple configurations therefore allowed the wall-related losses to be held nearly constant while improving the amount of higher-quality channel flow. Pressure-gain was observed to substantially increase as channel width increases, improving over 20% from the smallest to the largest channel widths when other geometry ratios are held constant. The best results obtained delivered a pressure gain of -3.1% and indicate the likelihood of further improvements as the nozzle to air-inlet area ratio is driven further towards a value of 1.0, especially for the larger channel widths.