节流阀中己烷凝结流动数值模拟

Numerical simulation of hexane condensing flow in throttle

建立了自发凝结和异质凝结流动统一的数值模型,研究了存在外界凝结核心时天然气中己烷蒸气的节流凝结性质,并对初始颗粒半径、初始颗粒浓度、背压比和总温等因素对己烷凝结性质的影响进行了分析。计算结果表明,己烷在节流后很短距离内凝结,凝结时间很短;己烷自发凝结的极限过饱和度很高;外界核心引起的异质凝结比较显著时会抑制自发凝结,使自发凝结量减小;初始颗粒半径和浓度越大,自发凝结量越小;背压比和总温增加时,凝结总量和自发凝结比重都减小。

If there are foreign nuclei（solid particles or liquid droplets etc.）existing in natural gas flow,condensation of hexane would take place on the foreign nuclei,and thus both homogeneous and heterogeneous condensation would occur in the throttling process.A uniform mathematical model for homogeneous and heterogeneous condensing flow was built to study flow field characteristics and condensation properties of hexane in the throttle valve.The effects of initial particles radius,concentration of the nuclei,back pressure ratio and total temperature on condensation properties of hexane were analyzed.It was shown that differential pressure and velocity of natural gas were very high in the throttle valve,and condensation was completed in a very short time.Owing to the high free energy barrier,homogeneous condensation of hexane could not occur until very high supersaturation ratio was reached.Homogeneous condensation would be restrained if both condensations coexisted in the condensing flow,which would cause the decrease of homogeneous condensation mass fraction.And the suppression effect became obvious when initial radius and concentration of the nuclei increased,under this circumstance the proportion of homogeneous condensation reduced compared to the case that only homogeneous condensation occurred.As back pressure ratio and total temperature increased,supersaturation ratio reduced which would cause the decrease of total condensation mass and proportion of homogeneous condensation simultaneously.