极低负荷工况下单缸核湿汽轮机末三级流动特性分析

Analysis of Last Three Stages Flow Characteristics under Extremely Low Load Condition for Single-cylinder Nuclear Wet Steam Turbine

基于Bladegen-Turbogrid实体叶片参数化建模方法与叶栅流道结构化网格划分方法,采用两相均质数值模型与湿蒸汽平衡相变模型,对不同容积流量工况下船用核动力湿汽轮机末三级进行了全三维定常数值计算,重点分析了极低负荷工况下湿汽轮机末三级的流动特性。结果表明:随着容积流量的降低,湿汽轮机末三级级内蒸汽流动紊乱度增加,湍动能分布波动程度加大,级内损失逐渐增加,湿度逐渐升高;极低负荷工况下湿汽轮机级内蒸汽流动最为复杂,末三级被涡流占据整个通流域通道,末级甚至次末级焓降为负值,做负功,这表明此时末两级不做功反而耗功,形成扩压段。

The full three-dimensional steady numerical calculation of the last three stages of marine nuclear power wet steam turbines under different volume flow conditions was conducted based on the Bladegen-Turbogrid solid blade parameterized modeling method and the cascade channel structured meshing method,and the two-phase homogeneous numerical model and the wet vapor equilibrium phase transition model were adopted.The flow characteristics of the last three stages of a wet turbine under extremely low load conditions were emphatically analyzed.The results show that with the reduction of volume flow rate the flow stability in the last three stages of wet steam turbine gradually decreases,the fluctuation degree of turbulent kinetic energy distribution increases,the loss in the stage and the humidity increases gradually.The steam flow in the wet steam turbine stage is most complicated under very low load condition.The last three stages are occupied by the vortex in the whole channel of the basin,and the enthalpy drop of the final stage and even the sub-final stage is negative to do negative work.This indicates that the last two stages do not do work but consume work instead of forming a pressure expansion section.