Effects of cryogenic temperature on propagation of hydrogen-air rotating detonation waves

• First investigation of rotating detonation waves (RDWs) fuelled by cryogenic hydrogen. • Cryogenic conditions significantly enhance detonation wave pressure and speed. • Lower inflow temperatures lead to higher mixture density and stronger combustion-driven wave dynamics. • Higher inflow pressures slightly enhance detonation pressure with negligible speed effects. • Findings demonstrate the potential of cryogenic hydrogen for advanced propulsion systems. This study presents a comprehensive numerical investigation into the formation and propagation of rotating detonation waves (RDWs) in hydrogen-air mixtures at cryogenic temperatures, with the objective of evaluating the performance benefits and feasibility of using cryogenic hydrogen in propulsion systems. This represents the first reported study of RDWs fuelled by cryogenic hydrogen, a fuel of interest due to its high density and potential for high-efficiency, carbon-free combustion. The cryogenic flow is modelled using the Noble-Abel Stiffened Gas (NASG) equation of state, coupled with a detailed chemical reaction mechanism. Simulations are performed across a range of inflow total temperatures (100 K to 1000 K) and pressures (3 to 7 bar) to examine their influence on RDW dynamics. Under cryogenic conditions (100 K), the detonation pressure significantly exceeds typical Chapman-Jouguet (C-J) values. Decreasing the inflow temperature increases mixture density and turbulence intensity, leading to enhanced detonation strength and faster wave propagation. In contrast, increasing the inflow pressure moderately raises detonation pressure but has only a slight effect on wave speed. These findings demonstrate that cryogenic hydrogen enables improved detonation performance and offers a promising pathway for developing high-efficiency, low-emission rotating detonation engines (RDEs). This work lays the foundation for future experimental studies and the advancement of cryogenic detonation-based propulsion technologies.