透平级轴向间隙对非定常流动干涉影响的研究

Influence of Axial Clearance on Unsteady Flow Interaction in Turbine Stage

针对透平级在两个轴向间隙下的非定常流场,应用全三维黏性非定常数值模拟方法分析比较了不同轴向间隙下的流场干涉现象,并引入了损失非定常波动机理.结果表明:透平级轴向间隙增大近1倍后,势干涉的变化在静叶和动叶前缘处体现得更为明显,壁面静压波动幅值分别降低了80%和60%左右,叶栅间的位势干涉强度较负射流强度下降的快;当负射流迁移至动叶吸力面尾部时,对气流分离会起到抑制作用,为沉寂效应的产生引入了一种新的诱发机制;针对静叶吸力面边界层内气流,通过耗散函数建立了静压与熵值之间的耦合关系,发展了分析非定常流场中损失波动的方法.

The full three-dimensional viscous numerical simulation is employed to analyze and compare the interaction phenomena of the unsteady flow field at two axial clearances in an axialflow turbine stage and then the mechanism of the unsteady loss fluctuation is adopted to describe the reason of entropy fluctuation. The results indicate that when the axial clearance is doubled, the potential interaction changes significantly at the entire stator and the leading edge of the rotor, and the fluctuation amplitude of wall static pressure decreases by about 80% and 60%, respectively. The descending of the potential interaction strength is much faster than that of the negative jet. When the negative jet arrives at the trailing edge of the rotor suction side, the repression effect on the flow separation will occur, resulting in a new triggering mechanism of the calming effect. In addition, the coupling relation between static pressure and entropy in the boundary layer flow of the stator suction side is built by a dissipation function, and a method to analyze the loss fluctuation in the unsteady flow field is developed.