The Effects of Parasitic Combustion on Detonation Wave Propagation

Rotating detonation engines (RDEs) are a feasible approach to realizing pressure gain combustion. However, practical implementation of these devices requires the use of non-premixed discrete fuel-oxidizer injection. Turbulent mixing of the fuel and oxidizer streams enforces reactant stratification inside the combustor annulus. Parasitic deflagrative combustion of the freshly-injected fuel-oxidizer mixture introduces partially-burnt gases to the detonation wave and diminishes heat release. Numerical studies of full-scale RDE systems have suggested that up to 35-50\% pre-burning of the fuel-oxidizer mixture is prevalent within the combustor. The primary objective of this work is to understand the interaction of the detonation wave and a spatially-inhomogeneous mixture. To this end, a high-fidelity numerical simulation approach is utilized to understand how partially-burnt mixtures affect the detonation wave structure by inducing different fractional levels of reactant mixture pre-burning with reference to the fully-burnt equilibrium state. The effect of pre-burning on detonation wave stability and characteristics are discussed to provide insight into the difference between theoretical Chapman-Jouguet detonation and the detonative combustion observed in practical combustors.