基于均相理论及流体动力守恒原理，对进口处于近临界区、出口为两相状态及质量流量为5.5 kg/s的透平膨胀机进行设计，得到膨胀机蜗壳、喷嘴和工作轮的基本几何参数，再采用平衡相变模型对膨胀机内流相变特性进行数值分析。结果显示：喷嘴入口处开始产生气体，叶轮出口气体质量分数为27%，等熵效率为65%，与设计值相差9.72%。结果表明，此设计方法可以用来设计两相状态CO2透平膨胀机，平衡相变模型适用于CO2透平膨胀机的内流相变特性研究。

The turboexpander with the inlet in near-critical region,outlet in two-phase state and mass flow rate of 5.5 kg/s was designed and the basic geometric parameters of expander volute,nozzle and rotor were obtained based on homogeneous phase theory and hydrodynamic conservation principle.The characteristics of internal flow phase change in the expander was numerically analyzed with equilibrium phase change model.The results show that gas appears at the nozzle inlet,the mass fraction of gas is 27% at the impeller outlet,and the isentropic efficiency is 65%,which is 9.72% lower than design value.This design method can be used to design the twophase CO2 turboexpander,and the equilibrium phase change model is suitable for studying the internal flow phase change characteristics of CO2 turboexpander.

TB653

国家科技重大专项（2017-V-0012-0064)