Two-stage injection mixing enhancement technology for wide-operating-range scramjets

One of the critical challenges in high-Mach scramjet technology is achieving efficient mixing between fuel and incoming air within the shortest possible distance. Building on the conventional alternating-wedge strut（AWS） injection system used in scramjets， this study proposes a novel two-stage injection configuration to address the rapid decline in mixing efficiency as Mach number and equivalent ratio （ER） increases. Large Eddy Simulation （LES） is employed to perform a detailed numerical investigation of the fuel mixing process under a combustion chamber entrance Mach number of 2.5 and 3.5. The flow field structures and the mechanisms of mixing enhancement are thoroughly analyzed. Results indicate that as the Mach number increases， the streamwise vortex pairs generated by the alternating wedge fail to merge effectively， leading to a reduction in mixing efficiency. The lateral injection introduced by the new two-stage strut promotes the merging of streamwise vortex pairs generated by the alternating trailing edges； the induced large-scale coherent structures also making it easier for the streamwise vortices to deform and break apart. Comparing to the alternating-wedge strut， the mixing efficiency is enhanced by 15% to 30%. The mixing efficiency of the novel two-stage strut is also influenced by the flow rate fraction of the lateral injection， with the optimal mixing efficiency occurring when this fraction is around 50%.