Effect of cavity depth on air-breathing rotating detonation engine fueled by liquid kerosene

In our recent experimental investigation, the feasibility of a liquid-kerosene-fueled air-breathing/ramjet rotating detonation engine featuring a cavity-based annular combustor has been experimentally demonstrated. Achieving stable operation and organized detonation combustion within the rotating detonation combustor presents significant challenges that demand further investigation. Thus, this study aimed to deepen our understanding of the optimal geometrical configuration of a cavity-based annular combustor operating in air-breathing mode. Numerous experiments were conducted to evaluate the impact of varying cavity depths on combustion performance under a supersonic incoming flow with a total temperature of 860 K. The findings indicate that adequate cavity depth is essential for the generation of kerosene-fueled rotating detonation waves in air-breathing mode. Notably, a kerosene-air rotating detonation wave was achieved in combustors with cavity depths ranging from 10 to 30 mm while maintaining a supersonic heated air mass flow rate of approximately 1000 g/s and a minimum equivalence ratio of 0.77. However, at a cavity depth of 10 mm, both the propagation velocity and peak pressure of the rotating detonation waves were significantly lower compared to those at 20 and 30 mm, thereby suggesting that the depth of 10 mm may require optimization. Additionally, optical observations revealed that the detonation reaction zone was located further from the combustor head as cavity depth increased. This indicates that deeper cavity depths allow for longer mixing and preheating times of the combustible mixture before detonation, thereby enhancing detonation performance. This study clarifies how cavity depth influences liquidfueled rotating detonation and provides guidelines for designing cavity-based annular combustors in airbreathing rotating detonation engines.