前向多翼式离心风机蜗舌附近流场的PIV试验研究

EXPERIMENT STUDY ON THE ELOCITY FIELD NEAR THE TONGUEOF A FORWARD CURVED MULTI-BLADES CENTRIFUGAL FAN

对前向多翼式离心风机建立了性能及流场测试台位,性能试验重复性良好。用粒子图像速度场仪(Particleimage velocimetry,PIV)技术对蜗舌附近速度矢量场做了详细的变工况测量及分析。结果表明,蜗舌附近的主要流动特征由冲向蜗舌的速度矢量方向及蜗舌周围滞止区的影响范围所决定。小流量时,滞止区影响范围主要在蜗舌间隙流道内,造成速度矢量向叶轮内偏斜,蜗舌下游易形成分离旋涡而恶化;大流量时,滞止区影响范围偏向蜗壳出口流道,蜗舌间隙流动较好。此外,在蜗舌间隙沿轴向不同位置返回蜗壳的流量也不同,这主要与叶片不同段做功能力不同有关。

In order to investigate in detail the velocity field near the tongue of a forward curved multi-blades centrifugal fan in various working conditions, a performance test is firstly conducted which insures the rig's reliable repeatability. Then the particle image velocimetry (PIV) is used to measure the velocity field near the tongue at different operating conditions and different axial location. The analysis shows that the flowpattern near the tongue mainly has relation with the influence of the stagnation area around the tongue as well as the direction of velocity vector bearing down on the tongue. When small flow rate state of working conditions, the influence of the stagnation region chiefly focuses near the passage inlet of the tongue clearance so that the clearance flow downstream is prone to separate from the tongue wall and deteriorates. When flow rate increasing, however, the influence of the stagnation area leans towards the passage of the volute outlet and the flow in tongue clearance does not form a distinct separating region.Furthermore, the flow rate returning into the volute through the tongue clearance varies from impeller shroud to hub by working difference of the blade at different segment, near the inlet end of the fan is low. The knowledge is very useful in improving fan performance.