Performance by Various Water Mist Nozzles in Extinguishing Liquid Pool Fires

Water mist based systems have emerged as potentially lucrative alternatives to Halon-based fire suppression systems and have been extensively studied in the literature. In the present work, experimental investigations are carried out on the performance of the water mist nozzles in extinguishing pool fires of diameter 0.1 m, 0.2 m, and 0.3 m with diesel and heptane as fuels. The growth of the fire is studied for these fires by measuring the transient mass burning rates. Water mist is generated by passing plain water at room temperature through single-head solid-cone pressure-swirl nozzles with X-type swirl-inserts. The nozzle is directed vertically downwards and operated at various heights (0.75 m to 2 m) from the fuel surface with the injection pressure ranging from 6 bar to 10 bar. The extinction performances of four nozzles with orifice diameters of 1.2 mm, 1.65 mm, 1.9 mm, and 2.45 mm are investigated through videography. A comparison of the extinction performances by all the nozzles is presented and the optimal nozzle based on the consumption of water is reported for a given fire. An empirical correlation for the extinction time is reported in both the dimensional and non-dimensional form. Observed interactions of the spray with fuel surface are reported depicting probable undesired phenomena in the application of the water-mist system with top injection.