汽轮机叶片正弯对叶顶间隙泄漏流动影响的数值模拟

Numerical Simulation of the Influence of Blade Positive Curving on Tip Leakage Flow in Steam Turbines

以某汽轮机高压级动叶为研究对象,采用κ-ε湍流模型,应用SIMPLEC算法对在相同叶顶间隙高度下的常规扭叶片和正弯扭叶片的叶顶间隙流动进行了数值模拟。研究结果表明:与常规扭叶片相比,叶片正弯提高了汽流在叶顶区的最低压力值,减小了叶顶压力边与吸力边的横向压力梯度;汽流在正弯扭叶片吸力面附近形成的泄漏涡的影响范围和对通道主流的扰动弱于在常规扭叶片内形成的影响;正弯扭叶片使汽流在吸力面和压力面上形成了叶顶部正径向压力梯度、叶根部负径向压力梯度的"C"型压力分布,同时降低了叶片上端部附近的总压损失。叶片正弯既降低了叶顶泄漏损失,又降低了叶栅通道内的掺混损失。

This paper reports a numerical study on leakage flow with same blade tip clearances of conventional twisted and positive curve - twisted blade in high-pressure stage of a steam turbine. The κ - ε turbulence model is adopted, and SIMPLEC arithmetic is used. The results shows that comparing with the conventional twisted blade, the positive curve-twisted blade improves the lowest pressure of steam flow in blade tip area and reduces the crosswise pressure gradient between pressure side and suction side. The influence scope and disturbance on channel flow of leakage vortex formed near suction side of the positive curve-twisted blade of steam flow is weaker than the conventional twisted blade. ＂ C＂-type pressure distribution which is positive radial pressure gradient in blade tip and negative radial pressure gradient in blade root is formed on pressure side and suction side of the positive curve-twisted blade of steam flow, and total pressure loss is reduced near the blade upper. The positive curve - twisted blade reduces leakage loss of tip clearance and mixing loss in the cascade channel.