Combustion and mixing in scramjet combustors with alternating-groove struts

An important design principle of a scramjet combustor is its excellent combustion performance and low total pressure loss. In this study, a strut with bumps, an alternating-wedge strut, and six Alternating-Groove Struts (AGS-1–AGS-6) were constructed based on a conventional strut. Their performances in the combustion and non-reaction states were compared, and the relevant mechanisms were analyzed by conducting numerical simulations with H 2 -fueled scramjet combustors. The important findings are as follows: (A) The combustion performance and total pressure loss in the combustion state are not positively correlated with the corresponding mixing performance and total pressure loss in the non-reaction state. In the non-reaction state compared to the combustion state, the significantly reduced low-speed flow zone and low static pressure near the wake cause varying degrees of changes in the vortex structure and shock wave system formed by each strut, owing to the absence of heat accumulation in the wake region. (B) The mechanisms by which AGS-4 and AGS-6 achieve excellent combustion performance include the following: the alternating grooves increase the combustion zone; the streamwise vortices of AGS-4 and the flow disturbances of AGS-6 induce large-scale heat and mass convection in the near wake; the recirculation vortices formed in the grooves achieve earlier ignition and more stable combustion; and the premixed combustion in the grooves enhances the near-wake turbulent kinetic energy to promote small-scale turbulent mixing. (C) The mechanisms by which AGS-5 and AGS-6 achieve excellent mixing performance include the formation of stable streamwise vortices with a large number and range of effects in the near wake, which leads to excellent large-scale convective mixing, and the high turbulent kinetic energy near the wake maintains small-scale turbulent mixing. (D) The intensity of the shock wave system is positively correlated with the total pressure loss of scramjet combustors. These discoveries are significant for developing scramjet combustors with excellent performances.