Water spray mitigation of hydrogen-air detonations: Steady-state regimes and detonability limits

Hydrogen–air detonations present significant safety hazards due to their supersonic propagation and extreme pressures and temperatures. Water-spray injection has been proposed as an effective mitigation strategy in the past. This study investigates the interaction between hydrogen–air detonations and a monodisperse water spray using a one-dimensional, steady, multi-continua model with detailed chemical kinetics and two-phase mass, momentum, and energy transfer. Non-calorically perfect gas effects and droplet vaporization are included. Results show that detonation behavior is primarily controlled by water mass loading and droplet size, subject to simplifying modeling assumptions. Small droplets vaporize rapidly, allowing detonation velocity to be predicted via a global energy balance accounting for latent heat, with the Chapman–Jouguet condition satisfied at thermochemical equilibrium. Increasing water loading in this regime can lead to complete detonation quenching. For larger droplets, pathological detonations occur, where vaporization and heat release decouple from the driving mechanism, and the propagation speed is determined by the internal detonation structure rather than a global energy balance. Very large droplets vaporize too slowly to significantly influence the detonation, and propagation speeds approach those of the dry hydrogen–air mixture. These findings clarify the parametric regimes for effective detonation mitigation in hydrogen safety applications, and permit us to redraw the theoretical detonability limits of hydrogen–air mixtures in presence of a liquid-water disperse phase.