Experimental study on combustion characteristics of water-in-oil emulsified diesel pool fire with water sublayer

•Emulsified diesel fire floating on water undergoes four stages: flame growth, quasi-steady combustion, boilover and extinguishing.•Boilover loss rate of emulsified diesel declines as water content rises from ξ = 0% to 5%.•Boilover loss rate of emulsified diesel rises initially and declines afterwards as ξ rises.•Maximal boilover intensity is is 1/4 to 1/6 times that of 0# diesel fuel. Study on the combustion of emulsified diesel facilitates the application of ISB method and enriches the theory of thermal engineering. The unsteady combustion behavior of emulsified diesel fuel with water sublayer is investigated using pool of 100,150 and 200 mm, oil thickness of 5, 7.5, 10, 12.5 and 15 mm, and water content of 0%, 5%, 10%, 15% and 20%. The boilover occurs once the temperatures of the fuel-water interface and the water in the fuel layer exceed the boiling temperature of water. An optimal water content to remove spilled emulsified diesel fuel floating on water is suggested. The liquid-phase convection heat transfer involving the boilover process of emulsified diesel fuel floating on water is analyzed. The nucleate boiling and interfacial layer bubbles in water promote the mixing of fluids, and the characteristic diameter of the bubble is attained according to the relative magnitude of liquid buoyancy (causing the bubble to detach) and surface tension (causing the bubble to attach to the surface). The maximal boilover intensity is quantitative calculate under various initial thicknesses and ratios of water content, thus the potential applications of emulsion boilover in the field of thermal engineering and fire prevention are proposed.