Extinction Limit of Diesel Pool Fires Suppressed by Water Mist

This work describes an experimental and theoretical investigation of extinction limit of diesel pool fires suppressed by water mist. A downward-directed nozzle produced a fine water spray over small-scale opposed diesel pool fires. The fire extinction limit is obtained from minimum nozzle injection pressure or maximum fire size when the fire extinguishment took place. For the conditions tested, it is observed that there are two distinct regions in the relationship between the injection pressure and fire size, i.e., a fire suppression region and a fire intensification region. The transition of the two regions is dependent on the effective water flux and the plume-spray thrust ratio. It is also revealed that the fuel surface cooling is the dominant mechanism for diesel pool fires at extinction limit in the tests. The failure to cause fire extinction is mainly due to the insufficient water flux applied to remove enough heat from the fuel surface.