In this study, a numerical analysis was conducted to investigate the effect of the tip clearance on the aerodynamic performance, internal flow characteristics, and stall region characteristics of an axial fan. Three-dimensional steady and unsteady Reynolds-averaged Navier-Stokes (RANS) calculations were conducted with a shear stress transport (SST) turbulence model. Tip clearance ratios of 0, 0.01, and 0.02 were applied to the impeller. As the tip clearance ratio increased, the aerodynamic performance of the axial fan decreased at both the design and the off-design conditions. The correlation between the tip leakage vortex (TLV) and the flow angle of the velocity triangle was presented for the difference in the tip clearance and flow rate. As the flow rate increased, the differences in the aerodynamic performance induced by the tip clearance ratio decreased. As the tip clearance ratio increased, the size of the TLV increased and gradually moved in the circumferential direction to interfere with the main flow at the low flow rate. Meanwhile, the size of the TLV was similar and gradually moved in the axial direction even if the tip clearance ratio increased at the high flow rate. The pressure fluctuations were observed by the fast Fourier transformation (FFT) analysis to compare and analyze internal flow characteristics at the stall region and design point. The static pressure was converted to the appropriate magnitude. The locations of the highest magnitude were shown to be different at the stall region and the design point, respectively.

在这项研究中，进行了数值分析，以研究叶尖间隙对轴流风扇的空气动力性能，内部流动特性和失速区域特性的影响。使用剪切应力传输（SST）湍流模型进行了三维稳态和非稳态雷诺平均Navier-Stokes（RANS）计算。叶轮的叶梢间隙比分别为0、0.01和0.02。随着叶尖间隙比的增加，轴流风扇的空气动力学性能在设计和非设计条件下均下降。针对尖端间隙和流速的差异，提出了尖端泄漏涡（TLV）与速度三角形的流动角之间的相关性。随着流量的增加，尖端间隙比引起的空气动力性能差异减小。随着尖端间隙比的增大，TLV的尺寸增大，并沿圆周方向逐渐移动，从而以低流速干扰主流。同时，即使在高流速下尖端间隙比增加，TLV的尺寸也相似并且沿轴向方向逐渐移动。通过快速傅立叶变换（FFT）分析观察压力波动，以比较和分析失速区域和设计点的内部流动特性。将静压转换为适当的大小。最高震级的位置在失速区域和设计点分别显示为不同。TLV的尺寸增加，并在周向上逐渐移动，以低流量干扰主流。同时，即使在高流速下尖端间隙比增加，TLV的尺寸也相似并且沿轴向方向逐渐移动。通过快速傅立叶变换（FFT）分析观察压力波动，以比较和分析失速区域和设计点的内部流动特性。将静压转换为适当的大小。最高震级的位置在失速区域和设计点分别显示为不同。TLV的尺寸增加，并在周向上逐渐移动，以低流量干扰主流。同时，即使在高流速下尖端间隙比增加，TLV的尺寸也相似并且沿轴向方向逐渐移动。通过快速傅立叶变换（FFT）分析观察压力波动，以比较和分析失速区域和设计点的内部流动特性。将静压转换为适当的大小。最高震级的位置在失速区域和设计点分别显示为不同。TLV的大小相似，即使在高流速下尖端间隙比增加，TLV也会沿轴向方向逐渐移动。通过快速傅立叶变换（FFT）分析观察压力波动，以比较和分析失速区域和设计点的内部流动特性。将静压转换为适当的大小。最高震级的位置在失速区域和设计点分别显示为不同。TLV的大小相似，即使在高流速下尖端间隙比增加，TLV也会沿轴向方向逐渐移动。通过快速傅立叶变换（FFT）分析观察压力波动，以比较和分析失速区域和设计点的内部流动特性。将静压转换为适当的大小。最高震级的位置在失速区域和设计点分别显示为不同。