水蒸气跨音速流动中非平衡相变的温度特性

Effect of temperature on non-equilibrium phase change in transonic steam flow

在引入水蒸气非平衡相变的动力模型和水蒸气真实物性模型的基础上,建立了水蒸气跨音速非平衡流动的守恒型数值计算模型,采用对激波捕捉具有高精度和高分辨率的Roe-FDS格式进行计算,数值求解了水蒸气跨音速流动过程中的非平衡相变及凝结激波现象。着重研究了水蒸气跨音速非平衡凝结相变的温度特性,归纳了水蒸气跨音速非平衡流动的凝结特性随温度的变化规律,归纳了蒸汽温度变化对核化凝结、激波形态的影响规律。研究发现,入口温度对蒸汽跨音速流动中的非平衡相变具有显著的影响,进口温度越低,非平衡核化凝结爆发得越早,产生的液滴粒径越大;随着进口温度的升高,非平衡凝结相变的起始点逐渐向喷管出口方向移动,蒸汽需要在缩放喷管中加速膨胀到较高Mach数下达到较高的过饱和度和过冷度时才能产生核化凝结,而成核率也相应较高。

A conservative compressible numerical model coupling with dynamic model for non-equilibrium phase change and virial equations of steam was developed and used to predict the spontaneous condensation phenomenon with homogenous nucleation in the transonic steam flow.In order to capture the transient characteristics of the transonic flow and the condensation shock effect,the improved high resolution Roe-FDS scheme was used.The influence of inlet steam temperature on the homogenous nucleation and the condensation shock was examined,and the effect of temperature change on the thermodynamic characteristic was investigated.It is found that the inlet temperature has a significant influence on the non-equilibrium phase change in the transonic steam flow.With a lower inlet temperature,the non-equilibrium homogenous nucleation occurs earlier and the radius of droplets is larger.As the inlet temperature decreases,the onset of the non-equilibrium condensation will move to the outlet of the nozzle,and the temperature will decrease rapidly to make the expansion steam achieve a higher Mach number,saturation ratio and supercooling temperature,and then the non-equilibrium condensation will occur eventually with a higher nucleation rate.