周向弯曲低压轴流风机叶顶泄漏流动数值研究

NUMERICAL STUDY OF TIP LEAKAGE FLOW OF THE LOW PRESSURE AXIAL FLOW FANS WITH CIRCUMFERENTIAL SKEWED BLADES

本文采用数值模拟的方法,对三种带有周向弯曲叶片的低压轴流通风机(原型叶轮、周向前弯及后弯叶轮)的叶顶泄漏流动进行了研究。在数值计算与试验测量结果较为吻合的条件下,从流场和压力场等不同角度分析探讨了叶片周向弯曲后,叶顶泄漏流动和泄漏涡的形成和发展规律。数值计算结果表明,叶顶周向前弯加剧了泄漏涡与主流的掺混;周向后弯叶轮比前弯叶轮有助于减弱叶顶泄漏流动;强度大、衰减慢的泄漏涡,降低了叶顶的通流能力,同时与主流的掺混加剧也增大了叶轮的端部损失;此外,顶部间隙高度的增加,泄漏流动加强,旋涡的起始点更靠近叶片后缘。

In this paper, the numerical simulation was used to investigate the tip leakage flow fields in a lower pressure axial flow fan with three kinds of circumferential skewed rotors, including the traditional radial rotor, the forward-skewed rotor and the backward-skewed rotor. Based on the measured and simulated results of the velocity and pressure fields, the characteristics of tip leakage flow and tip leakage vortex were studied, and effects of the circumferential skewed rotors and the heights of the tip clearance on the performance of the fan were described and analyzed. The results show that the mixing process between the tip leakage vortex and main flow is stronger in the forward-skewed rotor than in the backward-skewed rotor, the backward-skewed rotor can reduce the tip leakage flow. When the tip leakage vortex being stronger and decaying slower, the flux capability of the cascade is lower, and the end-wall losses increase because of the strong mixing process between the tip leakage vortex and main flow. Moreover, with the increase of the height of blade tip clearance, the tip leakage flow is stronger and the origination position of the tip leakage vortex is closer to the trailing edge of the blade.