The relationship between the number of detonation waves and the evolution process of the flow field in a rotating detonation engine was investigated through a numerical analysis. The simulations were based on the Euler equation and a detailed chemical reaction model. In the given engine model, the flow-field evolution became unstable when a single detonation wave was released. New detonation waves formed spontaneously, changing the operational mode from single-wave to four-wave. However, when two or three detonation waves were released, the flow field evolved in a quasi-steady manner. Further study revealed that the newly formed detonation wave resulted from an accelerated chemical reaction on the contact surface between the detonation products and the reactive mixture. To satisfy the stable propagation requirements of detonation waves, we proposed a parameter called NL, which can be compared with the number of detonation waves in the combustor to predict the evolution (quasi-stable or unstable) of the flow field. Finally, we verified the effectiveness of NL in a redesigned engine. This study may assist the operational mode control in rotating detonation engine experiments.

In this study, a numerical study based on Euler equations and coupled with detail chemistry model is used to improve the propulsion performance and stability of the rotating detonation engine. The proposed fuel injection called stratified injection functions by suppressing the isobaric combustion process occurring on the contact surface between fuel and detonation products, and thus the proportion of fuel consumed by detonation wave increases from 67% to 95%, leading to more self-pressure gain and lower entropy generation. A pre-mixed hydrogen-oxygen-nitrogen mixture is used as a reactive mixture. The computational results show that the propulsion performance and the operation stability of the engine with stratified injection are both improved, the temperature of the flow field is notably decreased, the specific impulse of the engine is improved by 16.3%, and the average temperature of the engine with stratified injection is reduced by 19.1%.