倾扭叶片在热电联产级组中的应用

Application of the Twisted and Sloped Blades in the Thermal-Power Co-Generation Turbine Unit

采用了倾扭复合成型的设计方案 ,对国产热电机组CC2 5的低压末两级进行了优化设计 .首先以准三维通流计算为基准 ,对进出口的几何参数进行了调整 ,兼顾了设计工况和变工况下的气动性能要求 ,提高了级组的总体运行效率 .叶型型线设计采用三次B样条控制成型、径向叠加的方法 ,按照进出口汽流角的变化规律进行径向扭曲 ,最终获得三维扭叶片 .进一步对静叶片进行斜置 ,提高了级的流动性能 .结果表明 :采用合理的静、动叶匹配可有效地减少攻角损失 ;对静叶进行合理的斜置和扭曲 ,对动叶采用合理的扭曲规律 ,可控制反动度的分布 ,有效减少根部 /顶部的次流损失以及减弱流动分离 ,减少余速损失 .改型后CC2 5机组低压末两级的内效率提高了 6 6 % .

Two low-pressure stages of CC25 turbine unit are optimized. The twist-slope combined design method is adopted to improve the original blades. Keeping the desired aero-performance both in design and off-design cases, the inlet and outlet geometric parameters of the stages are adjusted based on the quasi-three-dimensional calculations, and thus the efficiency of the turbine unit is increased. Third-order B-spline method is used in the twisted blade design considering the inlet and outlet flow angles. Meanwhile, the static blades are also sloped to improve the flow performance. The results show that proper match of the attack angles between stator and rotor blades can decrease the attack loss. Sloped and twisted stator blades and twisted rotor blades can adjust the reaction distribution along the spanwise direction, decrease the second flow loss at tip and hub, and decrease the exit loss. The inner efficiency of the two low-pressure stages is raised by 6.6 percent after the optimization.