Unsteady flow characteristics in hyper-burner with trapped vortex cavity during mode transition

To capture the flow characteristics during transitions in a trapped vortex cavity hyper-burner, a rectangular model was designed. A three-dimensional dynamic mesh simulation method was employed to investigate the flow characteristics of the hyper-burner under three different regulation schemes of rear variable area bypass injector (RVABI): baseline scheme (Case A), slow-then-fast scheme (Case B), and fast-then-slow scheme (Case C). The operating conditions included a mass flow rate of 1.5 kg/s, turbine inlet temperature of 550 K, ramjet inlet temperature of 300 K, and a RVABI movement duration of 2 s. The flow characteristics, mass flow distribution characteristics, and the mixing characteristics were obtained. The results indicated that: the flow characteristics of the three schemes were basically consistent. 0—0.16 s, although the adjustment of the RVABI affected the shape and core position of vortex within cavity, a complete and stable vortex structure can still be established. The flat RVABI had a relatively weak mixing, which was less than 0.3. Among the three schemes for 0.25 s, Case B had the largest mass flow ratio of cooling channel and the smallest total pressure loss. The total pressure loss mainly occurred within region 0.36>x/D>0.63 (where x was the position along flow direction, D was the length of hyper-burner).