【摘要】 采用数值方法研究了小流量条件下汽轮机低压缸末五级的气动性能及流动特性。分析了6种工况下低压缸末级气动参数和流场结构的变化规律,得到低压缸末五级的效率、焓降分配、子午面流线,以及末级流动结构、气流角和温度的分布规律。结果表明:减小相对质量流量会导致低压缸末五级总-总等熵效率和输出功率降低,在5.6%相对质量流量时,末五级总-总等熵效率、输出功率相对于设计工况分别下降23.5%和89.9%;随着相对质量流量的减小,末级动叶进口相对气流角逐渐增大,压力面近前缘处因负攻角发生流动分离,吸力面近尾缘处因逆压梯度产生流动分离,末级叶片温度显著上升;在小流量条件下,低压缸出口出现回流,末级动叶叶顶出现环形涡流;在14.2%相对质量流量下,末级动叶回流区沿径向发展至60%相对叶高处;在5.6%相对质量流量下,回流区从末级扩展至次末级。更多还原

【Abstract】 The aerodynamic performance and flow characteristics of the last five stages of the low-pressure cylinder of steam turbine under small flow rate were studied by numerical method. The variation of aerodynamic parameters and flow field structure of the final stage of the low-pressure cylinder under six working conditions were analyzed. The efficiency, enthalpy drop distribution, meridian streamline, flow structure, flow angle and temperature distribution of the last five stages of the low-pressure cylinder were obtained. Results show that the total-total isentropic efficiency and power output of the last five stages in the low-pressure cylinder decrease as the inlet mass flow rate decreases. At 5.6% design mass flow rate, the total-total isentropic efficiency and output power of the last five stages decrease by 23.5 % and 89.9 % respectively compared with the design condition. As the inlet mass flow rate decreases, the inlet relative flow angle of last rotor blade is increased gradually. The flow separation occurs near the leading edge of the pressure surface due to the negative attack angle, and the flow separation occurs near the trailing edge of the suction surface due to the inverse pressure gradient. As the inlet mass flow rate decreases, the temperature on last stage rotor blade is increased. Under the condition of small flow rate, backflow appears at the outlet of low-pressure cylinder and annular vortex appears at the top of last stage rotor blade. Under the relative mass flow rate of 14.2%, the recirculation zone of the final rotor develops to 60% relative leaf height along the radial direction. Under the condition of 5.6% relative mass flow rate, the recirculation zone extends from the last stage to the penultimate stage.更多还原