空调器新型轴流风扇叶尖涡的研究

RESEARCH ON THE TIP VORTEX IN THE AXIAL FLOW FAN FOR AIR-CONDITIONER

本文采用Navier-Stokes方程和Spalart-Allmaras湍流模型,对只在叶轮尾缘带有导流罩的低压轴流风扇进行了三维稳态内流模拟,详细分析了叶顶流场中叶尖涡的产生和发展轨迹。研究结果表明,叶尖涡在距叶尖前缘约1/4叶顶轴向弦长的吸力面附近形成,在叶轮出口附近消失,在切向约占3/4流道,近似形成一个涡环,阻塞主流.在回转面上,叶尖涡涡核先沿流线方向发展,在导流罩附近逐渐转为切向方向发展;在径向方向,叶尖涡先沿外径方向发展,在导流罩附近转向内径方向移动。空调室外机系统的不对称结构引起叶尖涡在叶轮旋转过程中的相对位移.流量的变化对叶尖涡的轴向位置影响较大,而对其径向位置的影响不明显;小流量时叶尖涡的轴向移动能力减弱,切向移动能力增强,消失位置向前缘方向移动.

The formation and development of the tip vortex in the axial flow fan with a shroud cover- ing only the rear region of the rotor tips had been analyzed numerically by solving three-dimensional Reynolds-averaged Navier-Stokes viscous partial differential equations with the Spalart-Allmaras tur- bulent model.It was found that the tip vortex was formed near the blade tip suction side about one fourth of the chord downstream of the leading edge,and disappeared near the rotor exit.It occupied about three fourths of the tip flow passage along the circumferential direction,formed a vortex ring around the rotor tips,and had a large blockage effect on the main flow.The tip vortex moved nearly along the axial and outward radial direction at the beginning of the formation,and then turned to move along the tangential and inward radial direction near the shroud.There was a little difference among the trajectories at different circumferential location,due to the asymmetry of the outdoor unit of split room air conditioners.The flow rates had a large effect on the axial position of the tip vortex. However,its effects on radial position of the tip vortex were not notable.At low flow rates,the move- ment of the tip vortex was enhanced in the tangential direction and weakened in the axial direction, and disappeared at a location more close to the leading edge.