Interplay between water-mist spatial continuity and droplet response in hydrogen deflagration suppression

An Eulerian–Lagrangian gas–liquid model was developed to investigate ultrafine water-mist suppression of hydrogen deflagration in confined spaces. Continuous, two-section, and three-section mist distributions were examined for droplet diameters of 10–45 μm. Continuous mist maintained sustained evaporative cooling and dilution, whereas sectioned arrangements produced a “suppression–recovery–resuppression” response because of mist-free gaps. Increasing droplet diameter weakened thermal response and overall suppression, and reduced the influence of spatial distribution. The onset of divergence among overpressure curves was delayed from about 5.0 ms at 10 μm to 8.0 ms at 45 μm. For 10 μm droplets, flame-propagation suppression efficiencies were 17.65%, 17.23%, and 12.46% for continuous, two-section, and three-section distributions, respectively. At 45 μm, the efficiencies decreased to 1.93–2.73%, while the distribution-induced difference narrowed from 5.19 to 0.80 percentage points. Under the conditions investigated, suppression performance was governed primarily by the temporal alignment between droplet evaporation and flame-front propagation, rather than by the peak evaporation rate alone.