Numerical Investigation of Kerosene-Assisted Aluminum Combustion in a Scramjet with Varying Cavity Spacing

A comprehensive numerical investigation is conducted to evaluate the impact of tandem cavity spacing on a scramjet combustor using a kerosene-assisted aluminum powder combustion scheme. An Euler–Lagrange model is established to analyze the flow-field evolution and combustion characteristics under different cavity configurations. The results show that high-temperature exhaust gases from upstream kerosene pilot combustion provide effective flame-holding relay, maintaining final kerosene combustion efficiency above 95%. Cavity spacing strongly affects heat release, combustion efficiency, and aerodynamic total-pressure recovery. Narrow spacing promotes rapid ignition but causes local flow deceleration and high-temperature regions exceeding 3200 K, increasing total-pressure loss. In contrast, excessive spacing increases inter-stage heat dissipation and reduces aluminum combustion efficiency to 69%. A moderate cavity spacing provides a balance between combustion enhancement and total-pressure recovery, maintaining aluminum combustion efficiency within 85–90% while avoiding severe flow deceleration. These results demonstrate that tandem cavity spacing is a key parameter governing multiphase combustion and thermal characteristics in kerosene-assisted aluminum-fueled supersonic combustors.