An experimental study of the effects of water mist characteristics on pool fire suppression

Abstract

Suppression of pool fire by a water mist is influenced by mist characteristics, its location and orientation relative to the fire. A heptane pool fire was generated in 1m×1m×1m chamber in a 125mm diameter pan. Mist was generated with a pair of twin-fluid atomizers installed at the ceiling centre. Nitrogen at 4–8bar and 104–136LPM flow rate aspirated water at 0.18–0.22LPM. Mean droplet diameter and velocity measured at 500mm and 850mm from the atomizer were 18–30μm and 2.2–3.2m/s, respectively. The fire was produced at four locations and mist was activated 30s after fire initiation. Temperatures were measured along the flame centreline at 160, 360 and 560mm above the fuel surface. CO, CO2 and O2 concentrations were also measured. Mean droplet diameter decreased and velocity increased with increasing nitrogen pressure. Fire suppression time decreased with increasing gas pressure approaching asymptotic value for pressures greater than 6bar for all location of fire. The fastest suppression (12–18s) was achieved for fire at the chamber centre where mist spray was symmetrical and slowest (47–68s) for farthest location of fire from mist.