Active direction control of rotating detonation waves by swirl injection

Le résumé fourni par la source

In this study, the directional controllability of detonation waves in a rotating detonation engine (RDE) operated with gaseous ethylene and oxygen was experimentally investigated using swirl injection. A doublet tangential injector imparted azimuthal momentum to the propellant supply, with swirl angles ( ψ inj ) of 0, 30, 45, and 60 deg and combustor lengths ( L ) of 20 and 80 mm. The propagation direction and structure of the detonation wave and the behavior of the injector jet were visualized in the axial and radial directions using high-speed imaging. Across 22 trials with various swirl configurations, the rotating detonation wave propagated exclusively in the swirl-positive direction, affording a significantly higher probability of directional alignment. The underlying mechanism was elucidated by visualizing the transient initiation process in which the deflagration was triggered outside the combustor exit and propagated into the chamber. Transient observations revealed the azimuthal asymmetry of the wave structure and mixture layer between counter-propagating waves. The negative-direction wave exhibited liftoff from the combustor base, an irregularly shaped wavefront, and nonideal deflagration within the mixture layer. The positive-direction wave remained near the combustor base, with a rectified wave surface and a stratified mixture layer. Following collision with the counter-propagating waves, the positive wave survived, and the system settled into stable two-wave propagation. Steady-state radial visualization confirmed canonical structure of the detonation wave, including an oblique shock wave and a parasitic combustion layer. The filling height of the mixture layer decreased significantly with the wave number, whereas the swirl angle had an insignificant effect under constant-wave conditions, indicating incomplete attainment of the designated swirl momentum during detonation. The effective jet occupancy increased monotonically with the swirl angle, with higher swirl promoting the scavenging of residual burnt gas and suppressing nonideal combustion. Novelty and significance statement Active control of the propagation direction in a rotating detonation engine via swirl injection was experimentally demonstrated, supported by direct high-speed visualization of the underlying azimuthal asymmetry during transient initiation. The mechanism underlying the swirl-induced directional selectivity and steady-state mixture layer structure was elucidated, offering a compact, mechanically simple pathway for controllable RDE operation.

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