Experimental study on the interaction of water mist spray with two buoyant non-premixed flames

Single-fire and double-fire extinguishments by water mist were conducted to assess the similarities and differences. The double-fire extinguishment requires higher applied volume flux of the water mist and spray momentum, while it is achieved faster than the single-fire extinguishment, owing to the smaller size of the single flames of the double-fire. Both the air entrainment restriction among the two flames of the double-fire and the typical re-ignition phenomenon have a significant effect on the double-fire extinguishment. A double-fire merging from the burner surface is more difficult to be extinguished in terms of the critical operating pressure since the air entrainment restriction among the two flames of the double-fire is more intense. A double-fire with a smaller flame spacing requires a longer extinguishing time since re-ignition happens more easily. The equivalent diameter (De) is applied to calculate the plume–spray thrust ratio of the double-fire and evaluate the competition between the double-fire and the water mist quantitatively.