Bifurcation in Rotating Detonation Engine Operation with Continuously Variable Fuel Injection Location

Abstract

Sensitivity of rotating detonation engine operation and performance to the location of fuel injection was characterized using continuous variation of the injector geometry during an experiment. The fuel injector location was translated in relation to the oxidizer throat in a jet-in-crossflow configuration to study the influence of injection dynamics on combustor operation. The injector was translated toward and away from the stationary oxidizer throat for a range of operating conditions. High-speed measurements of pressure and flame chemiluminescence intensity, along with thrust, were used to characterize the detonation wave propagation in the experiment and evaluate combustor performance. Higher wave speeds were observed at injector locations closest to the oxidizer throat, with decreased wave speed and eventual transition to deflagrative operation occurring at locations farther downstream. Variation in fuel injection location induced bifurcations in the number of waves, resulting in corresponding changes in wave speed and gross thrust. Hysteresis was observed in these quantities as the direction of injector translation was reversed. Active translation promoted detonative operation of the experiment at conditions and configurations that hitherto operated only in a deflagrative mode with fixed combustor geometry.