Mechanisms of extinction of liquid fires with water sprays
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Abstract An investigation has been carried out on the extinction by means of water sprays of fires of liquidsburning in a vessel 30 cm in diameter. The effect on the ease of extinction of (1) the nature of the liquid, (2) the time between the ignition of the fire and the application of the spray, (3) the properties of the sprays and (4) the direction of application of the spray have been studied. It was found that liquids like keronine, which can be extinguished by being cooled to the fire point, or by bring diluted, like alcohol, could be extinguished reliably by certain water sprays, although in some cases the extinction took a long time. For liquids like petrol and benzole extinction depended primarily on whether or not stable. These stable flames were very difficult to extinguish and were usually established readily when the preburn time was very short (less than 6 to 10 seconds) and also when the spray was applied in a horizontal direction across the fire. Over the range of conditions under which extinction took place, the extinction time decreased as the rate of flow and the entrained air current in the spray increased and generally also as the drop size of the spray decreased; the effect of drop size for the petrol, benzole and alcohol fires was very marked. There was evidence that for petrol and benzole fires heat transfer between the flame and the water drops, resulting in either cooling of the flames or the formation of steam, played a part in the extinction.