Analysis of Non-Conventional Cavity Flameholders for Turbulence-Driven Flame Stabilization and Enhanced Supersonic Hydrogen Combustion in Scramjet Propulsion

Abstract This study presents a comprehensive numerical investigation into the aerodynamic and combustion performance of cavity-based flameholder geometries integrated within a supersonic scramjet combustor. The objective is to enhance fuel–air mixing, shock-induced recirculation, and overall combustion efficiency under high Mach number conditions using geometries optimized for flow disruption. Four innovative cavity designs—wedge, wavy wall, triangular bump, and circular bump—are systematically evaluated to assess their influence on flow structure, flame holding capability, and energy release. The combustor is modeled with hydrogen (H2) fuel injected at Mach 1 beneath a splitter plate and high-speed air entering at Mach 2.5 above it. Simulations are conducted using the Reynolds-averaged Navier–Stokes equations coupled with the shear stress transport k–ω turbulence model and finite-rate chemistry to resolve the H2–air combustion reaction kinetics. The study analyzes local flow properties, including velocity, static temperature, pressure, Mach number, turbulence intensity, and mass fractions of H2 and H2O across multiple axial locations to determine mixing and combustion behavior. Grid independence and model validation with the experimental and literature data confirm the fidelity of the numerical setup. Among the configurations, the wedge cavity produces the strongest shock–vortex interaction, leading to peak combustion efficiency (>97%), complete hydrogen consumption, and sustained low-Mach, high-temperature regions. The wavy wall design shows distributed flame anchoring and moderate turbulence intensities, resulting in 93% combustion efficiency with more uniform heat release. The triangular and circular bumps, while structurally simple, exhibit weaker flow modulation and underdeveloped reaction zones, limiting their performance. Quantitative metrics reveal that wedge and wavy wall geometries induce 25–28% turbulence intensities, 85–90% mixing efficiency, and produce static temperatures exceeding 2400 K. These findings demonstrate that the cavity geometry significantly influences fuel–air mixing, flame stability, and thrust-producing potential in supersonic combustion environments.