中压低温透平膨胀机膨胀端三维数值模拟

采用CFD方法对某型号中压低温透平膨胀机膨胀端进行整机全周数值模拟,全面考虑了进气蜗壳、叶顶间隙气封、轮背气封和轴封等细节结构对膨胀端气动性能和流场的影响.研究结果表明:进气蜗壳的几何形状是造成喷嘴进口气流沿叶高方向分布不均匀的主要原因;轮背气封、叶顶气封和轴封内存在明显的旋涡流动,且叶顶气封是典型的后台阶流动,齿封内和台阶后旋涡涡轴方向相反;喷嘴和叶轮之间过小的间隙导致气流在喷嘴压力面一侧形成激波,激波/附面层干扰使叶片和下端壁附面层同时分离,在上、下端壁角区各形成一个弯曲的涡管,最后终止于动静交界面.

Numeral Simulation of Turbocharged End in Medium-pressure Cryogenic Turboexpander

In order to study the influence of volute geometry, tip clearance seal, impeller back seal and shaft end seal in aerodynamic performance, the three-dimensional steady flow in medium-pressure cryogenic turboexpander was simulated via the computational dynamics fluid method in this paper.The results show that volute geometry was the main cause of the uneven flow distribution along the nozzle blade.There was obvious vortex-flow in three above seals, which in tip clearance was the typical backward-facing step flow.Also, a too small gap between nozzle and impeller caused the formation of shock waves in pressure side of nozzle, and shock-boundary layer interactions led to airfoil boundary layer separation and a curved vortex tube formation, finally terminated in rotor-stator interface.The computational results provided a basis for aerodynamic optimization and modified the design of turboexpander.