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

TL;DR

This study numerically investigates how water spray clouds affect hydrogen/air detonations, revealing different propagation modes and extinction mechanisms influenced by droplet and cloud properties.

Contribution

It introduces a detailed numerical analysis of detonation-water cloud interactions, highlighting the effects of droplet size, concentration, and cloud radius on detonation behavior.

Findings

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

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

Water clouds can cause detonation extinction without autoignition.

Abstract

Inhibition of hydrogen explosion is crucial to realize its wide applications and fine water spray is an ideal mitigant due to numerous advantages. In this work, interactions between a propagating hydrogen/air detonation wave and circular water cloud are numerically studied. Eulerian-Lagrangian method involving two-way gas-droplets coupling is applied, with a two-dimensional configuration. Different droplet (diameter, concentration) and cloud (diameter) properties are considered. Our results show that droplet size, concentration and cloud radius have significant effects on peak pressure trajectory of the detonation wave. After interacting with cloud, the detonation wave exhibits three propagation modes, including perturbed propagation, leeward re-detonation, and detonation extinction. Leeward re-detonation is analyzed from unsteady evolutions of gas and liquid droplet quantities. The refracted detonation wave inside the cloud is decoupled and propagates more slowly than the one outside the cloud. The detonation re-initiation is from a local hot spot, caused by shock focusing from upper and lower diffracted detonations. Disintegration of water droplets proceeds when the detonation wave crosses the cloud and multiphase interfacial instability is observed due to the difference in effective density of the two fluids. Furthermore, detonation extinction is observed when we consider various water cloud size. It is featured by quickly fading peak pressure trajectories when the detonation passes the 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. Moreover, parametric studies considering various droplet concentrations and cloud radii are performed.