Experimental study and mechanism analysis of pool fire suppression by effervescent-atomized water mist

A series of pool fire suppression experiments were performed by using a new effervescent-atomized water mist fire protection system,and the extinguishing mechanisms as well as the factors that affect the water mist performance were studied.Effervescent atomization is a new atomization technology that was recently introduced into fire fighting area and it is used in generating water mist.In this paper, a new effervescent atomized water mist fire protection system was developed and the fire suppression experiments were conducted.The experiments were performed in a space of 9m×9m×4 m use a manner of local application.The nozzle was fixed at 2.0m height from the pool and the water mist was sprayed vertically down to the pool fire.The pool fire was a 36 cm-diameter round gasoline pan with fire power 130 kW and pre-ignition time of 90 s.The nozzle was operated with compressed nitrogen and water,so the water flow rate was different in the same water jet pressure due to different gas-liquid ratio. During the experiments,the jet pressure and the flow rate of water were varied.The range of nozzle pressure was from 1.1 MPa to 0.5 MPa and 6-8 water flow rate were carried out for each pressure. The shape,temperature and radiation flux density of the flame and the fire extinguishment time was recorded.The results show that the pool fire can be put out by effervescent-atomized water mist in a very short time under specific conditions.According to the results the extinguishments can be classified into four types:instantaneous,short time,long time and unsuccessful.The main extinguishing mechanism of each type was different.The main extinguishing mechanism of the instantaneous extinguishment was blowing out,while the short time extinguishment was the combination of blowing out and cooling.For the long time extinguishing,the mechanism was only caused by cooling. The experiment results also show that when the pressure is decreased, the range of the water flow rate for successful and rapid fire extinguishment is reduced.When the pressure is 0.5 MPa,the nozzle can put out the pool fire with only one water flow rate.