Small-scale Experiment Study Of Crude Oil Boilover Fire Behavior And Hazard Characteristics Under Cross Air Flow

Boilover fire is a special form of fire in crude oil storage tank,boiling will make the flame temperature and radiation instantly increases.The spilled fire around the tanks,which caused by spilled oil,makes the rescue crews difficult to get close to the tanks.What’s more,it also poses a threat to the surrounding equipments and may cause disastrous consequences.Meanwhile,because of the particularity of the location of the storage tank,horizontal wind often exists during the combustion of boilover fire.The cross air flow can promote the mixture of combustible gas and air,make the flame tilt,change the thermal feedback of the flame to the fuel,and enhance the thermal radiation of the flame to the downwind direction.All of these put forward a new chanllenge to the rescue work of the boilover fire.Therefore,it is of great significance to study the combustion characteristics of the boilover fire under cross air flow.In order to investigate the combustion behavior and hazard characteristics of the boilover fire under the cross air flow,a series of small scale experiments with ShengLi crude oil were carried out to simulate the boilover fire in this paper.Fuel mass data of each tests can be obtained by electronic balance,and the characteristics of the mass burning rate of boilover fire under different combustion conditions are obtained.The boilover fire under cross air flow and burning in quiescent ambient with the same combustion process.Based on the evolution of mass burning rate,the combustion process of boilover fire can be divided into four stages: growth stage,quasi-steady stage,boilover stage and decay stage.Steady burning rate increase with pool diameter.It also decreases when cross wind speed is smaller than 1.0m/s and increases with cross wind speed when wind speed exceeds 1.0m/s.Meanwhile,the steady burning rate is independent on the initial fuel layer thickness.Boilover stage burning rate increases with initial fuel layer thickness,and its evolution with the pool diameter was similar with steay burning rate but the minimum value occurs when the cross wind speed in 0.5m/s.The flame length and tilt angle are analyzed by image processing program.The results showed that the steady flame length is mainly influenced by the mass burning rate in quiescent ambient,while the boilover flame length is also influenced by the wind speed under cross air flow.The mathematical models of flame length at different stages of ShengLi crude oil boilover fire under different environmental conditions are built with dimensionless analysis.Flame tilt angle increases with the increase of wind speed and the decrease of pool diameter.The flame tilt angle at boilover stage is smaller 1-3 degres than that in steady stage.The tangent(tan)value of the tilt angle is proportional to the reciprocal of dimensionless Richardson number linearly.The occurrence of boilover is determined by the crack noise of bubble before oil droplets are ejected.The maximum boilover intensity concept was proposed and the calculation method of boilover intensity was improved.In quiescent ambient,the boilover onset time decreases with the diameter and proportional to the initial fuel layer thickness.Boilover intensity increases with the initial fuel layer thickness and decrease with the pool diameter.The boilover onset time and boilover intensities are proportional to the ratio of the initial fuel layer thickness and the pool diameter,and the prediction models are built based on this relationship.Under cross air flow,boilover onset time and intensities increase with wind speed from 0m/s to 1.0m/s,and decrease when wind speed exceeds 1.0m/s.Based on the dimensionless mass burning rate and the dimensionless Froude number,the prediction models of boiliver onset time and intensities under cross air flow were obtained.