除湿槽对涡轮叶栅非平衡凝结流动的影响

Influence of moisture removal slot on wet steam non-equilibrium condensation flow in turbine cascade

摘要:

为准确模拟汽轮机末级长叶片湿蒸汽流场,基于双流体模型开发了汽液两相非平衡凝结流动计算方法,对表面开设除湿槽的某汽轮机末级叶片进行数值研究,分析涡轮叶栅内不同除湿槽结构对非平衡凝结流动的影响及作用特点．结果表明,在叶片表面吸力面开设的除湿槽能有效降低叶栅喉部水滴成核率,从而降低相变引起的非平衡凝结损失,使叶栅出口的较大直径水滴数目显著减少;具有较大的来流进口宽度和引流结构的除湿槽结构,有利于提高湿蒸汽级长叶片表面的水膜抽吸效果．

Abstract:

To provide precise simulation for the flow field of steam turbine last stage, the calculation method for the vapor-liquid two-phase non-equilibrium condensing flow was developed based on the two-fluid model. The numerical simulation of moisture removal slot on the surface of a steam turbine last stage blades was carried out, and the influence of different moisture removal slot structures on the non-equilibrium condensing flow of turbine cascade was analyzed. The results show that the moisture removal slot set on the blade suction surface can effectively reduce the nucleation rate of water droplets near the throat region of cascade,therefore decrease the loss of non-equilibrium condensation caused by phase transition,significantly reduce the number of larger diameter water droplets at the outlet of the blade cascade. Due to larger inflow width and more reasonable moisture removal structure, the scheme II is more beneficial to improve the suction effect of the water film on the surface of long blade in the wet steam stage.