出气边形状对叶栅中凝结流动影响机理的数值研究

NUMERICAL STUDY OF EFFECTS OF TRAILING EDGE SHAPES ON CONDENSING FLOW IN CASCADE

湿蒸汽两相凝结流中凝结过程对流场参数的变化敏感。本文对一个叶型五种出气边形状对应的凝结流动进行了比较,以初步揭示几何参数影响凝结流动的机理。结果显示,出气边形状的改变影响凝结流中水滴状态、熵增、湿度、出口气流角的分布。在本文计算条件下,当出气边为平行于切向的平面时,流动中熵增最小,叶栅出口处湿度也最小,其原因在于这种出气边形状造成的流场参数改变使叶栅中蒸汽凝结过程受到抑制,叶栅出口蒸汽仍然维持了较高的非平衡程度。

The condensing process is sensitive to the variation of local flow field. A numerical study has been performed for the condensing flows in a cascade, which has five different trailing edge shapes. This is intended to preliminarily reveal how geometry affects the condensing flow. The computations show that the droplets distribution, entropy increase, wetness fraction, and flow angle are changed when the shape of trailing edge varies. The predicted entropy increase and wetness fraction at trailing edge are both the least when the trailing edge takes the shape of plane parallel to the tangential direction. The reason leading to this is that the condensing process is weakened when the flow field is changed by taking this trailing edge shape. The steam flow at outlet of cascade still remains relatively high level of non-equilibrium state.