Study on combustion characteristics of hydrogen fuel jet based on strut in transonic flow field

It is beneficial to expand the flight envelope of TBCC by improving the working ability of the ramjet combustor under extreme conditions. Using a Reynolds-averaged Navier-Stokes (RANS) simulation, we analyzed the transonic flow field and discovered a novel "shockwave dislocation" phenomenon. Here, variations in the position and strength of local shockwaves created distinct local pressures, which caused the backflow behind the strut to transition into a streamwise vortex. Our findings revealed that the hydrogen injection method significantly influenced this phenomenon. In the case of side injection, increasing the hydrogen jet velocity altered the position and strength of the shockwave, intensifying the dislocation phenomenon and expanding the streamwise vortex range. This enhanced mixing promoted combustion, increasing the outlet temperature uniformity index. However, it also led to local fuel enrichment, which decreased combustion efficiency to a minimum of 0.764. Conversely, with streamwise injection, an increase in hydrogen jet velocity caused the jet to squeeze the high-speed air around the upper strut. The subsequent combustion and expansion of hydrogen led to an enlarged upper recirculation zone. The mixing mechanism transformed into a coupled streamwise vortex with this expanded recirculation zone. This also increased the streamwise vortex range and, consequently, the outlet temperature uniformity index. Nevertheless, combustion efficiency still declined, reaching a minimum of 0.973. At low hydrogen flow rates, the combustion efficiencies of both side and streamwise injection methods were comparable. However, at high flow rates, side injection proved more effective. This was because the shockwave dislocation phenomenon generated by side injection created a larger range of streamwise vortices, leading to more efficient combustion.