Influence of Injector Count and Sizing on Rotating Detonation Engine Dynamics

Rotating detonation engines (RDEs) promise improved thermodynamic efficiency over traditional combustion engines, improved energy density, mechanical simplicity, and continuous operation. Nevertheless, several questions remain on how to optimize the injection system for these devices, which controls the flow distribution inside the combustor and the coupling between the combustion chamber and reactant plenum. To address these obstacles, we studied a 2-dimensional “unwrapped” computational model of an RDE with simplified reaction kinetics. Two different inlets were explored: a) equally spaced zones of constant mass flux separated by isothermal walls and b) equally spaced slots separating a combustion chamber from a reactant plenum. The number and area ratio of these injectors were varied over several individual simulations, and the impacts of these parameters were assessed using both quasi-Monte-Carlo analyses and simulations in which area ratio was continuously varied. Results revealed that more injectors promote a definite band of limit cycles with more detonations, but this is conditioned on area ratio. The physics affecting stability of certain modes, and how they are affected by injector coupling, were investigated. When the mass flow rate was varied at fixed injector parameters, the dominant number of detonations increased before decreasing beyond a certain transition. This was found to be mainly caused by increased mixture density due to increasing chamber pressure.