小型风扇叶顶间隙内部流动数值模拟

Numerical Simulation on the Small Cooling Fan Internal Flowing

通过对不同叶顶间隙小型风扇内部数值模拟,得出不同叶顶间隙小型风扇的静特性曲线、相同S面间隙涡流变化及叶顶到机闸内表面各回转面涡流变化。研究得出:当流量Q小于0.006 5 m3/s时,4个不同叶顶间隙的总压变化趋势一致,均随叶顶间隙的增加总压减小。流量增加时,叶顶间隙为2.5 mm时性能较好;在相同S面上,间隙涡流现象随叶顶间隙的增大而减弱;对于同一个风扇模型,轮毂到叶顶之间不同回转面上无涡流出现,叶顶到机闸内表面之间不同回转面涡强随半径增加而增强,在r=43.5所对应的回转面上达到最大,在机闸对应的回转面上涡强减弱,且出现二次涡;当其他条件不变、只改变叶顶间隙时,相同半径回转面上的涡强随着叶顶间隙的增加而减弱,且涡核逐渐沿吸力面弧线向下游移动。最大涡强均出现在r=43.5回转面上,且叶顶间隙为2 mm和3 mm时,回转面上出现较明显的二次涡。以上结论为分析不同叶顶间隙对小型风扇气动性能的影响提供了一定的理论依据。

In this paper,the internal of small cooling fan with different tip clearance are numerically simulated.The static characteristic curve of small fan at different tip clearance,changes of tip clearance vortex on the same S surface and changes of vortex on revolution surface from blade top to surface of machines inside are obtained.The results are： when flow rate is smaller than 0.0065 m3/s,the trend of total pressure change on four different tip clearances are same,that is to say,the total pressure decreases with the increasing of tip clearance.Compared four different tip clearance models,performance of the small fan with 2.5 mm tip clearance is the best when flow rate increases,and in the same S surface,the tip clearance vortex weakens with tip clearance increasing;For the same fan model,there is no vortex from hub to blade top,but on the revolution surface from blade top to radial radius r=43.5 mm,the vortex intensity increases with the radial radius increasing,which reaches the maximum value on the revolution surface of r=43.5 mm;vortex intensity is weakened and secondary vortex is generated on the internal surface of machines;Changing the tip clearance and maintaining other conditions unchanged,the vortex on revolution surface weakens with tip clearance increases,and vortex core offsets gradually along the suction surface arc downstream.Overall,for four models,there is the strongest vortex in the r=43.5 revolution surface,obvious secondary vortex appears in revolution surface that tip clearance are 2 mm and 3 mm.These conclusions for analysis of different tip clearance have an effect on small fan aerodynamic performance on a certain theoretical basis.