Detonation structure evolution in an optically-accessible non-premixed h₂-air rdc using mhz rate imaging

Investigations of the structure of non-premixed rotating detonation waves and the influence of the fuel-air injection system are presented in this work. A hydrogen-air rotating detonation combustor (RDC) with optical access extending from the oxidizer injection plenum to the exit plane is used. Via intensified high-speed cameras, the structure of propagating detonation waves are resolved at frame rates up to 1 MHz. At high mass flux, weaker detonation zones are observed via broadband chemiluminescence near the injection plane and stronger zones further downstream. The detonation wave longitudinally couples with the injection plane and produces minimal observable combustion product back-flow through the injectors. The axial variations in the detonation strength are attributed to fuel stratification, mixing, and local variation in thermodynamic properties of the mixture. The longitudinal coupling is attributed to periodic variations of the height of the detonation wave. These phenomena are investigated for varying mass flux, which affects the detonation wave structure and coupling with the injection plenum. Unsteady Reynolds-Averaged Navier-Stokes simulations are used to complement the experimental observations and provide insight into the fuel-air mixing and product flows for the same combustor geometry and conditions. These investigations are part of ongoing efforts to understand the effects of combustor design and operating parameters on combustion efficiency and RDC operation.