Leakage And Diffusion Of Oil Vapour From The Rim Seal Of The Large Floating-roof Tank In Strong Wind

With increase of the capacity of the floating-roof tank,the rim seal has become a weak point threatening the safe operation of the oil storage tank.Leakage of the oil vapour induced by the sealing failure of the rim seal in extreme weather will lead to energy waste,environment pollution and sometimes even fire and explosion.Hence,studying the structure failure and gas leakage characherisitcs of the rim seal is of great significance to the security of the floating-roof tank oil storage in our country.In this thesis,leakage and diffusion of oil vapour from the rim seal of the floating-roof tank in strong wind are analyzed numerically using the large eddy simulation(LES)method.Firstly,benchmark models for the wind load and oil vapour diffusion from a floating-roof tank are established and the corresponding LES solution procedures are proposed,respectively.Using experimental results reported by other authors,accuracy and stability of the two LES solution procedures are validated,with a relative error lower than 26.45%.Secondly,using LES method proposed for turbulent flow around the floating-roof tank,effects of wind speed and liquid level on the wind loads of the inneral and external tank walls are studied.The wind pressure distribution characteristics are analyzed using the instantaneous vortex structures in the flow domain.Based on the numerical resutls,the risk of tank capsizing,windward wall buckling and floating roof movement under strong wind is estimated.Finally,using the LES solution procedure proposed for oil vapour diffusion,the vertical,circumferencial and spatial distribution of oil vapour around the foating-roof tank are investiaged.The results show that: when the liquid level of the storage tank is low,the oil vapour concentration on the windward side is higher than that on the leeward side,and the combustible area on the leeward side is the largest.As the liquid level rises,the vertical dilution characteristicsof oil vapour increase,the circumferential transport operation is weakened,and the area of the combustible area decreases.The results obtained in this thesis are consistent with the points of primary seal separating from tank wall and the location of rim seal fire of field tanks.This paper provided four fire prevention and control measures.