Effects of Injector/Wave Coupling on the Operation of a Rotating Detonation Engine*

We experimentally investigate how the coupled dynamics of the air and fuel injection systems affect the properties of the detonation wave in a laboratory scale rotating detonation engine (RDE) operated under different fuel injection schemes and operating conditions (mass flux and equivalence ratio). Specifically, we evaluate how the dynamic response of the inlet/injector, i.e. its propensity to transmit pressure waves from the channel to the plenums, affects the stability of the wave. Wave stability is quantified in terms of the cycle-to-cycle variation of speed and pressure profiles extracted from simultaneous measurements of dynamic pressure in the air/ fuel plenums and detonation channel, and high speed chemiluminescence imaging marking the location of the detonation wave. We compare two configurations: (1) an axial air inlet with rear facing angled fuel injection; and (2) a radial air inlet with transverse fuel injection. Under operation they exhibit different dynamics that result in the formation of counter-propagating secondary acoustic waves that influence the strength and stability of the primary detonation wave, ultimately affecting the overall properties and performance of the device.