Spray combustion dynamics in a strut-cavity integrated afterburner with closely-coupled fuel injection

Integrated afterburners with strut-cavity coupled flameholders offer the potential for low pressure loss and compact, high-intensity combustion, yet their combustion dynamics and stabilization mechanisms remain insufficiently understood under closely-coupled fuel injection. In this work, a Eulerian-Lagrangian large-eddy simulation framework is employed to investigate spray combustion in a strut-cavity integrated afterburner. The present integrated configuration exhibits a coupled flame stabilization mechanism governed by the interaction between the strut recirculation zone (SRZ) and the cavity recirculation zone (CRZ). Hot products and fuel-rich gases from the SRZ are entrained into the cavity, while the cavity flame propagates toward the strut and assists flame anchoring near the strut-cavity junction. This bidirectional exchange forms a self-sustained strut-cavity stabilization loop, enabling robust cavity combustion even without cavity fueling. Two different fuel-jet velocities are examined to explore how fuel distribution affects flame dynamics. The results show that injection momentum strongly alters fuel penetration and mixing upstream of the strut, producing distinct heat-release distributions and temperature ratios across the shear layer and the SRZ. These variations modulate the strength of the Bénard-von Kármán (BVK) instability, yielding either asymmetric large-scale shedding flames or more symmetric flames with reduced fluctuations. In the far wake region, the BVK response is further found to be radially non-uniform and governed by local velocity scaling, rather than by a globally synchronized shedding mode.