不同容积流量下汽轮机低压缸末三级定常流动数值研究

Numerical Investigation on Flow Characteristics in Steam Turbine Low Pressure Cylinder and LPEH under Different Volume Flow Rate Conditions

借助商用计算流体动力学软件CFX,对不同容积流量下某大型核电汽轮机低压缸和排汽缸联合进行了全三维黏性定常流动的数值研究,详细分析了低压缸末三级的流动特性。结果表明:在40%设计流量下,末级动叶根部受逆压梯度的作用,在吸力面近尾缘区域开始发生流动分离,并随着流量的进一步减小,逆压区域向径向发展而形成回流;在30%设计流量下,负攻角导致末级动叶顶部压力面的近前缘区域发生流动分离,随着流量的进一步减小,该分离向叶根发展;在10%设计流量下,末级静叶顶部及根部受负攻角的作用而导致压力面近前缘区域发生流动分离;末级动叶在靠近叶顶处的绝对出口气流角会随着流量的减小不断增大,通过绝对出口汽流角在叶高方向的转折点可以判断回流区径向扩展的位置。

A numerical investigation on full-three-dimensional steady viscous flow fields in the last three stages and low pressure exhaust hood（LPEH） of a steam turbine was conducted using the commercial computational flow dynamics software CFX.The flow fields in the last three stages were analyzed in detail.The results show that a separation caused by the adverse pressure gradient occurs at the hub section near the trailing edge of the last stage rotor at 40% of the design mass flow rate.Moreover,a separation caused by the negative attack angle occurs at the tip section near the leading edge of the last stage rotor at 30% of the design mass flow rate.A separation also caused by the negative attack angle occurs near the leading edge of the last stage stator at 10% of the design mass flow rate.In addition,the absolute outlet flow angle of the last stage rotor at the tip section increases with the decrease in volume flow rate,and the radial location of the reverse flow can be determined by the turning point of the absolute outlet flow angle in the blade radial direction.