Large eddy simulation of fuel/air co-flow jet mixing enhancement in supersonic crossflow

Efficient mixing is critical for combustion organization in a high Mach number flows, and fuel/air co-flow jets continue to gain attention as a potential injection scheme. To further investigate the flow and mixing characteristics of co-flow transverse jets in a supersonic crossflow, high-fidelity Large Eddy Simulations are conducted by implementing a low numerical dissipation scheme. The reliability of the numerical method is confirmed by comparison with the experimental data. Then the effects of central air jet pressure, annular fuel jet pressure, and central jet activation/deactivation on the mixing process are systematically analyzed. Current research indicates that increasing central air jet pressure suppresses velocity fluctuations in the windward shear layer, while raising annular fuel jet pressure enhances mixing in this region. Deactivating the central jet introduces an additional recirculation zone, weakens jet penetration, reduces the leeward recirculation zone, and concentrates turbulent kinetic energy in the jet shear layer and wake. Mixing efficiency analysis shows that increasing central jet pressure or deactivating the central jet elevates downstream mixing efficiency to approximately 45 %, which is significantly better than the annular fuel jet pressurization scheme. Vortex dynamics investigation demonstrates that higher annular fuel jet pressure increases the average vorticity peak. The baroclinic term and the compressible dilatational stretching term show a bidirectional adjustment effect on the shear layer/wake region. Increased central jet pressure introduces supplementary air, raising the viscous term contribution to 48 % and significantly inhibiting vorticity growth. Furthermore, the vorticity stretching term and compressible dilatational stretching term dominate the vorticity generation and transport processes. This study provides theoretical foundations for enhancing the mixing performance of co-flow jet configurations.