Fire Extinguishing Performance Evaluation of the Downward Water Mist to Methane-Air Premixed Laminar Flame

In many engineering processes such as gas turbines and ignition engines, premixed combustion is the main form of energy conversion. The fire safety rising from such industrial buildings becomes a growing concern. In this study, a McKenna burner made for calibration is used to generate the laminar flame with the equivalence ratio of 0.78 ~ 2.0. The effect of the downward water mist spray on the extinction of methane-air premixed laminar flame is investigated by using hydroxide planar laser-induced fluorescence (OH-PLIF). The variation of water flow rate for flame extinction is analyzed by hydroxyl radical concentration distribution and effective water mist flow rate. The required water flow rate for flame extinction is higher in the cases of rich-fuel mixtures. The maximum critical extinguishing water flow rate for the methane-air premixed laminar flame is about 0.00955 L/min under the conditions of water mist spray with 45° solid cone spray angle and 24 μm droplet size. Furthermore, the evolution of OH-PLIF flame behavior revealed that the stability of the hydroxyl radical concentration at the base of the flame is mainly contributed to the flame extinction. These results are valuable for optimum safety design of such fire accidents.