摘要
液化天然气(LNG)储运过程中受热侵袭造成储罐压力升高具有极大的危险性。用范德华方程描述具有一定过热度的LNG汽化相变过程,引入微分同胚项对其进行变换,发现其形式符合尖点突变平衡点方程,揭示了突变机理是储罐内LNG大规模蒸发现象的本质特征。选取过热区内的LNG作为一个系统,运用系统论和突变动力学方法对势函数及其微商曲线进行研究,得到了极限过热度、失稳过热度及储罐内部压力增量和系统内液化天然气汽化量之间的关系。
The present paper is concerned with a study on the sudden boosting of LNG tank pressure under thermal attack has swinging fatalness during storage and transportation. As more and more people are using LNG for household fuel consumption, the safety of LNG storage and transportation has become an ever more important issue. Lots of accidents have happened in this way, even leading to lots of casualty and material loss. To solve the problem, it is necessary to introduce and use the catastrophe theory, a potential dynamic theory by nature. Seeing that liquefied natural gas is a kind of non-ideal fluid, Van der Wall equation can be used to describe the gas-liquid phase transition of superheated LNG. First of all, the control parameters of the equation can be transformed into dimensionless, after the differentiable homomorphism is used to its simplification. As we know, the equation can be found in the same form as that for cusptype catastrophe. Then the figures of equilibrium curve formed by critical points and the three-dimensional control of the parameter plane of cusp-type catastrophe can be gained. Take the LNG in overheated region as a system, its potential function and differential curve can then be analyzed in conformity with the theory of catastrophe dynamics. The nonlinear effects, which are the most essential factors of large-scale evaporation, are easily proved by using some simple theories. And some figures mentioned above, when the gas-liquid phase transition occurs at μ1 = 0, μ2 〈 0, can be turned from one-phase convection to the nucleus boiling in the LNG storage tank. The unstable superheated degree and limiting superheated degrees can be found. According to the Dalton theorem, there is a direct ratio between the incremental pressure of LNG storage tank and the quantity of evaporation. The higher the operating pressure of the storage tank, the more dangerous it will be. In such a case, some actions should be brought into effect, for example, the security relief valve can be automatically made to work in time and the heat insulation of the LNG storage tank should be credible enough. In doing so, tank invalidation and other catastrophic accidents can practically be avoided.
出处
《安全与环境学报》
CAS
CSCD
2006年第3期9-12,共4页
Journal of Safety and Environment
基金
国家自然科学基金资助项目(50474034)
关键词
安全工程
液化天然气
尖点突变
核态沸腾
失稳过热度
safety engineering
liquefied natural gas
cusp-type catastrophe
nucleus boiling
unstable superheated degree
