Detonation Structure in Ethylene/Air-Based Non-Premixed Rotating Detonation Engine

Abstract

Rotating detonation engines (RDEs) are gaining significant interest as a practical approach to increasing the operating efficiency of propulsion systems through pressure gain combustion. To use RDEs in practical gas turbines, their stability and performance with regard to hydrocarbon fuels need to be tested. Prior experimental work has shown that ethylene/air systems exhibit suppressed wave propagation, with speeds that are nearly half the ideal wave speeds. The purpose of this study is to simulate realistic RDE configurations that have been experimentally studied to gain insight into this wave suppression. Detailed numerical simulations using a reduced 8-species 2-step and a 21-species 38-step chemistry model are conducted. When ethylene is diluted with hydrogen, the system reaches a stable mode comparable to detonation propagation after unsteady transition period between a weak deflagrative and a stronger detonation mode. It is further shown that pure ethylene cases stay in the weak regime with weak pressure propagation aided by deflagration along the wave path. Species, temperature, and pressure profiles normal to the wave front show a weak pressure rise followed by a broad reaction zone. As a result, heat release is not confined to the near-shock region but is distributed across the detonation chamber.