Interaction of three-dimensional flow characteristics and flame dynamics in a strut-cavity based scramjet combustor

The combustion flow field inside a scramjet combustor exhibits complex three-dimensional (3D) characteristics and interacts with the flame evolution. An experimental study on the 3D multi-sectional flow field visualization and the correlation between flow and flame dynamics within a strut-cavity based scramjet combustor is conducted with particle image velocimetry, high-speed photography, and proper orthogonal decomposition. Both non-reacting (Ma 3, 1600 K) and reacting (Ma 3, 2300 K) flows are tested. Four horizontal planes and one vertical plane in the rear of the strut are measured. Results show that the non-reacting flow is characterized by high-speed free stream on both sides (1100–1300 m/s) and a central low-speed recirculation zone (100–300 m/s). The recirculation zone narrows as it approaches the cavity and the vortices inside become more pronounced. The recirculating flow drives the flame to establish from the rear to the front, with an increasing velocity toward the top of the strut. The reacting flow consists of about 2/3 of the low-speed turbulent zone (100–400 m/s) and a high-speed free stream (900–1200 m/s) on one side. The stabilized flame repeatedly deflects horizontally, causing the relative positions of the high- and low-speed regions to switch. The recirculation behind the strut evolves into a large vortex, driving the detonation-induced flame to enter the cavity, bifurcate, and propagate backward to the upstream of the strut. The acquisition of the three-dimensional flow field and its interaction with flame behaviors helps deepen the understanding of scramjet combustion and provides data reference for engine design.