The effect of mono-dispersed water mist on the suppression of laminar premixed hydrogen–, methane–, and propane–air flames

Computational simulations are used to predict and understand the influence of fine water mists on the suppression of laminar, freely propagating methane–, propane–, and hydrogen–air atmospheric-pressure premixed flames. The model solves a coupled, chemically reacting, two-phase-flow problem. Flame suppression is measured in terms of a reduction in burning velocity. The effects of droplet diameter, net water loading, and fuel–air stoichiometry are reported. The results show similar qualitative features for all the flames. Generally speaking, smaller droplets are more effective than the larger droplets. Sufficiently small droplets (approximately 10 μm diameter for methane–air flames) are in a small-droplet limit, where even smaller droplets have the same suppression characteristics for the same net mass loading. Droplets above a certain diameter (approximately 30 μm for methane–air flames) lead to a turning-point extinction, where the burning velocity at the turning point is approximately half of the unperturbed burning velocity without any water-mist loading.