关键词: 凹腔, 超声速, 剪切层, 等离子体激励, 流动控制

Abstract: Restricted by the cavity combustor configuration size and influenced by the high-speed airflow, fuel mixing efficiency within a scramjet combustor is low. To address this issue, based on a pulsed arc plasma actuator matrix, a synchronous actuation mode and two traveling wave actuation modes were designed. High-speed schlieren imaging was employed to conduct experiments on plasma actuation for controlling the supersonic cavity flow field. The control effectiveness of the number of synchronously actuated actuator columns and the different actuation modes on cavity flow fields with three different aft-wall inclination angles were comparatively analyzed by synthesizing flow field evolution and statistical analysis of schlieren images. The results indicate that plasma actuation can effectively excite density fluctuations in the cavity shear layer. Under baseline (no actuation) conditions, as the aft-wall inclination angle increases, the fluctuation intensity of the shear layer exhibits a monotonically increasing trend due to enhanced cavity resonance; moreover, the larger the aft-wall inclination angle, the smaller the increment in density fluctuations induced by plasma actuation. In the synchronous actuation mode, as the number of actuated columns increases, the disturbance range to the flow field expands, leading to a monotonic increase in the amplitude of shear layer density fluctuations. Both traveling wave actuation modes outperform the synchronous mode. The Upstream Traveling Wave (UTW) mode distributes disturbances evenly over one actuation cycle, aiming to increase the equivalent actuation frequency. Conversely, the Downstream Traveling Wave (DTW) mode superimposes the thermal bulbs induced by plasma actuation along the streamwise direction, enhancing the degree of interaction with the shear layer and causing a significant increase in its fluctuation amplitude. Physically, the shock waves and thermal bulbs induced by plasma actuation are the root causes of the disturbances. These disturbances thicken the boundary layer and excite instabilities in the shear layer, thereby leading to the generation of wavy oscillations.

Key words: Cavity, Supersonic flow, Shear layer, Plasma actuation, Flow control