Study On Characteristics Of Small-Scale Boilover With Different Fuel Layers And Sub-layers

Petroleum is an indispensable energy resource and raw material for modern production,and strategic petroleum reserves for national energy security have been constructed globally.Large numbers of fuel storage tanks were utilized by refineries and chemical plants around the world.The fire caused by leakage in the tank farm may easily change into boilover,which is one of the most dangerous disasters.The splashing burning droplets during the boilover can cause the "Domino effect" disaster by igniting the adjacent combustibles,thereby deteriorate the fire accident.Boilover is an extremely complex process involving many physical and chemical changes.The mechanism of boilover is still in need of exploration and improvement.Therefore,this work is to study the mechanism of boilover by conducting a series of small-scale boilover experiments with various fuel layers and sub-layers.Three fuel layers(diesel,kerosene,and n-hexadecane)and three sub-layers(water,saturated sodium chloride(NaCl)solution,and saturated magnesium chloride(MgCl2)solution)under the different oil pan diameter and initial fuel layer thickness were selected to investigate various boilover results.The experimental results and theoretical analysis showed that:(1)The development process of small-scale boilover with different fuel layers are similar,which can be divided into four stages:quasi-steady stage,boilover premonitory stage,boilover stage and decay stage.The development of small-scale boilover varied with different sub-layers.Under the influence of sub-layers,the third stage of smallscale boilover with the saturated NaCl solution sub-layer is a pseudo-boilover stage.The development process of small-scale boilover with the saturated MgCl2 solution sub-layer can be divided into three stages:the first quasi-steady stage,transition stage and the second quasi-steady stage.(2)Boilover is affected by the joint influence of fuel layer and sub-layer.Different fuel layers affect the sub-layer’s boiling bubble’s behavior through physical properties such as the initial fuel thickness,surface tension,boiling point,latent heat of vaporization of the fuel,which result into different patterns of boilover including single boilover,multiple boilover or no-boilover.The sub-layer can affect the super-heated limit of the fuel-sub-layer interface and the sub-layer’s post-boiling bubble’s behavior by changing the sub-layer physical parameters such as surface tension,boiling point,saturation vapor pressure,so as to achieve inhibition of boilover to varying degrees.(3)Bubble’s behavior is strongly linked to the magnitude of the boilover intensity.The boilover intensity is positively affected by the number of bubbles in the fuel layer,the continuity and density of bubbles distribution.(4)Bubble’s behavior is bound up with the occurrence of boilover,the expansion of the flame,the splashing burning droplets during the boilover.The occurrence of boilover is attributed to a sufficiently large bubble in the fuel layer.And the expansion of the flame in all directions and the splashing droplets at diverse heights and in various directions is relevant with the collapse of different bubbles in the fuel layer.