Rotating Detonation Waves in Scramjet Engines Using Preheated Kerosene for Pressure-Gain Combustion

Rotating Detonation Scramjet Engines (RDSJs) enable pressure-gain combustion through continuous, self-sustained detonation waves traveling within an annular chamber, offering improved efficiency and reduced combustor length relative to conventional scramjets. However, stable detonation operation with liquid fuels such as kerosene remains challenging due to evaporation time-scales, ignition delay, and multi-phase flow effects. This study investigates the fundamental physics governing wave propagation, stability limits, and performance metrics for kerosene-air fueled RDSJs through a combined analytical and computational framework. ZND-based detonation structure analysis and theoretical CJ calculations establish expected detonation speeds of 1780–1880 m/s near stoichiometry, while transient CFD simulations reveal realistic wave propagation at 1600–1800 m/s (80–90% CJ) under Mach-2.5 inflow with preheated kerosene. Results demonstrate that ignition delay reduction through fuel preheating (500–800 K) and annular-width alignment with detonation cell size (λ ≈ 12–22 mm) are critical for maintaining single-wave stability and suppressing multi-wave or extinction modes. Numerical evidence highlights a narrow stability window (ϕ ≈ 0.9–1.1), with pressure-gain up to 15–22% and thrust consistency >95% during stable rotation. These findings provide new insights into detonation-wave confinement, injectioninduced non-uniformities, and the physical origins of instability, offering design guidelines for next-generation pressure-gain hypersonic propulsion systems.