The Rocket-Based Combined Cycle (RBCC) engine is a promising propulsion system for hypersonic and space launch applications due to its capability to operate efficiently over a broad range of flight conditions. This study investigates the influence of total temperature and total pressure on flow patterns in the rocket-ejector mode of a RBCC engine using two-dimensional numerical simulations—a simplification that facilitates efficient parametric analysis while inherently omitting three-dimensional effects. The transition between stable and wavy flow patterns under the Diffusion and Afterburning (DAB) combustion mode is analyzed. Higher total temperatures enhance mixing efficiency but can induce wavy flow patterns, leading to potential instability. Conversely, increased total pressures promote stability through Fabri-choking mechanisms while reducing mixing efficiency by limiting entrainment capacity. A significant hysteresis effect is observed, where transition thresholds for stable and wavy states vary based on operational history. Key mechanisms contributing to this effect are discussed in depth, including momentum flux dynamics, Fabri-choking behavior, shock wave reformation, and mass and heat exchange processes. These findings provide critical insights for optimizing RBCC engine performance by balancing flow stability and mixing efficiency under varying conditions. This study’s insights into flow pattern dynamics, particularly the hysteresis effect, are crucial for developing robust control strategies and optimizing RBCC engine designs for hypersonic and space launch applications.
Wu et al. (Sat,) studied this question.