Interactions between a propagating detonation wave and circular water cloud in hydrogen/air mixture

TL;DR

This study investigates how circular water clouds affect hydrogen/air detonations, revealing effects of droplet size, concentration, and cloud radius on wave behavior, including propagation modes, re-ignition, and extinction mechanisms.

Contribution

It introduces a detailed Eulerian-Lagrangian simulation approach to analyze the complex interactions between detonation waves and water clouds, identifying key parameters influencing detonation quenching and re-ignition.

Findings

Droplet size, concentration, and cloud radius significantly influence detonation pressure trajectories.

Three propagation modes identified: perturbed, re-detonation, and extinction.

Critical cloud size for quenching decreases with higher droplet concentration.

Abstract

Interactions between a propagating hydrogen/air detonation wave and circular water cloud are studied. Eulerian Lagrangian method involving two-way gas-droplet coupling is applied. Different droplet (diameter, concentration) and cloud (diameter) properties are considered. Results show that droplet size, concentration and cloud radius have significant effects on peak pressure trajectory of the detonation wave. Three propagation modes are identified: perturbed propagation, leeward re-detonation, and detonation extinction. Leeward re-detonation is analyzed from unsteady evolutions of gas and liquid droplet quantities. The detonation is re-initiated by a local hot spot from shock focusing of upper and lower diffracted detonations. Disintegration of water droplets proceeds when the detonation wave crosses the cloud. In addition, detonation extinction is featured by quickly fading peak pressure trajectories when the detonation wave passes the larger cloud, and no local autoignition occurs in the shock focusing area. Evolutions of thermochemical structures from the shocked area in an extinction process are also studied. The transfer rates of mass, energy and momentum of detonation success and failure are analyzed. Moreover, parametric studies demonstrate that the critical cloud size to quench a detonation decreases when the droplet concentration is increased. However, when the droplet concentration is beyond 0.84 kg/m3, the critical cloud size is negligibly influenced due to small droplets. Two-phase fluid interfacial instability is observed, and the mechanism of cloud evolution is studied with the distributions of droplet, vorticity, density / pressure gradient magnitudes, and gas velocity.