进汽参数对拉伐尔喷管中水蒸气自发凝结的影响

Effects of Inlet Parameters on Spontaneous Condensation of Water Steam in a Laval Nozzle

针对不同进汽参数条件下水蒸气从过热区膨胀进入湿蒸汽区的自发凝结规律问题,采用数值模拟方法研究其流过拉伐尔喷管时在非平衡和平衡条件下的凝结特性,分析了进汽参数对水蒸气非平衡凝结过程的过冷度、液滴数、湿度、压比以及马赫数的影响,比较了其平衡凝结和非平衡凝结特性的差异。结果表明:当进汽压力较低时,水蒸气非平衡凝结过冷度较大,压力和马赫数的突跃现象显著;随着进汽压力提高,非平衡凝结造成的参数突跃变化减小,出口湿度逐渐增大,当p/p c为0.8时,出口湿度超过了20%。通过比较水蒸气的平衡凝结和非平衡凝结特性,发现喷管进汽压力较低时,水蒸气非平衡凝结与平衡凝结计算结果的差异显著,Wilson点在平衡态中湿度达到8.40%;而当进汽压力接近临界压力时,平衡凝结的计算结果基本接近非平衡凝结的结果,Wilson点在平衡态中的湿度仅为1.98%。

In view of the spontaneous condensation laws of water steam expanding from the superheated zone into the wet steam zone under different inlet parameters,a numerical simulation method is adopted to study the condensation characteristics of water steam flowing through a Laval nozzle under non-equilibrium and equilibrium conditions.Effects of inlet steam parameters on the supercooling,droplet number,humidity,pressure ratio and Mach number of the water vapor in the non-equilibrium condensation process are analyzed.And then the differences between the equilibrium condensation characteristics and non-equilibrium condensation characteristics are contrasted.Results show that the supercooling of non-equilibrium condensation is greater,and the changes in pressure and Mach number are more significant when the inlet pressure is lower.With the increase of the inlet pressure,the changes in pressure and Mach number are reduced gradually,and the outlet humidity increases and exceeds 20%when p/p c reaches to 0.8.By comparing the equilibrium condensation and non-equilibrium condensation,it is found that when the inlet pressure is low,the calculation results of non-equilibrium condensation and equilibrium condensation are significantly different,and the humidity of Wilson point reaches to 8.40%in equilibrium condition.When the inlet pressure is close to the critical pressure,the result of equilibrium condensation is basically close to that of non-equilibrium condensation,and the humidity of Wilson point in equilibrium condition is only 1.98%.