Safety Assessment Of Jacketed Cryogenic Liquefied Tanker Based On Fluid-solid Coupling

When the liquefied tanker occurs the emergency braking or the emergency avoidance turning,the liquid sloshing flow in the tank and the tanker wall surface will form the fluid-solid coupling effect,and induce liquid hammer impact on the tank wall surface,thus affecting the tank strength,which may cause the tanker to rollover and induces the traffic accidents,or which may cause the tanker the strength failure,and induces the explosion safety accidents.So it’s of great scientific significance to establish the scientific design theory of cryogenic liquefied tanker that systematically studies influence of the tanker induced liquid hammer impact on its structural strength and motion stability in the emergency braking and emergency avoidance turning process.This paper takes the jacketed cryogenic liquefied tanker as the research objective,and systematically simulates and studies the formation mechanism of liquid hammer impact induced by the liquefied tanker’s liquid sloshing in the emergency avoidance turning,and the relationship between the liquid hammer impact and the key control parameters,which clearing the key control parameters,and the influence of the liquid hammer impact induced by fluid-solid coupling effect in the emergency avoidance turning process on the dynamic response and failure of liquefied tanker.The research results will lay a scientific theoretical foundation for the establishment of scientific cryogenic liquefied tanker design theory and method.The liquid sloshing phenomenon induced in the emergency avoidance turning process is the asymmetric ring liquid sloshing along the inner surface of the tank,and the fluid-solid coupling effect of the asymmetric ring liquid sloshing can induce the obvious liquid hammer impact.The maximum liquid hammer shock pressure induced by the fluid-solid coupling effect of the asymmetric ring liquid sloshing in the emergency avoidance is 246 times as many as the static pressure of the liquid column,and obviously larger than that induced by the emergency braking.The study shows that the liquefied tanker emergency avoidance is the most dangerous working condition.The technical measure of adding four transverse anti-wave boards and one longitudinal anti-wave board in the tank can make the maximum liquid hammer shock pressure of the jacketed cryogenic liquefied tanker in the actual emergency avoidance condition reduce from 2.46 MPa to 1.28 MPa,and the reduction range is as high as 48%.The study shows that the addition of the longitudinal anti-wave board can obviously suppress the liquid hammer shock effect induced by fluid-solid coupling of the asymmetric ring liquid sloshing in the emergency avoidance turning.The tank structure stress under the combined load conditions of design pressure and actual emergency avoidance liquid hammer shock pressure is obviously larger than that under the combined load conditions of ASME code section XII volume design criteria’s design pressure and inertia force.It is the unsafe and unscientific treatment method that using the inertia force to reflect the inertia effects of actual emergency avoidance turning at ASME code section XII volume design criteria.Its unscientific place is that only consider the mechanical stress to satisfy the force balance of the inertia force induced by the inertia acceleration at the tank,and don’t truly reflect the obvious liquid hammer shock pressure generated by the fluid-solid coupling effect of the asymmetric ring liquid sloshing induced by the actual emergency avoidance inertia.The research results of the stress analysis safety assessment show that the tank designed by according the combined load conditions of ASME code section XII volume design criteria’s design pressure and inertia force and satisfying the analytical design strength conditions doesn’t necessarily satisfy the analytical design strength conditions under the combined loads conditions of design stress and actual emergency avoidance liquid hammer pressure.The liquefied tanker’s design must take into account the influence of the actual emergency avoidance liquid hammer pressure.For this reason,the scientific design method of the cryogenic liquefied tanker was put forward,in which the long-term design pressure load and transient short-term emergency avoidance liquid hammer shock pressure load have been comprehensively considered.