开式离心纸浆泵叶轮流道内部流场PIV试验研究

PIV measurement of internal flow field in open-impeller flow passages of centrifugal pulp pump

为研究开式纸浆泵叶轮流道内纤维颗粒对液相流场的影响,采用透明有机玻璃材料制造模型样机,以清水和0.1%质量浓度的头发纤维悬浮液为介质,通过PIV试验对叶轮流道内的流动进行可视化研究.试验结果表明:当输送清水介质时,在大流量工况下叶轮流道内流动稳定,未出现旋涡和低速区;在小流量工况下,当叶轮流道旋转到蜗壳隔舌附近位置时,在叶轮流道中段压力面附近开始产生低速区,且低速区随着叶轮流道靠近隔舌位置和流量减小逐渐增大,在远离隔舌位置的叶轮流道内未产生明显的低速区;受叶片扭曲的影响,在叶轮流道内垂直于泵轴的不同截面上的相对速度大小不同,且随着叶片扭曲程度减小,相对速度差减小;输送头发纤维悬浮液介质时,在纤维颗粒的影响下,叶轮流道内的液相流动相对速度降低,导致在小流量工况下叶轮流道中段压力面附近低速区面积增大;在大流量工况下,纤维颗粒存在使液相流动的相对速度大小分布更均匀.

In order to investigate the influence of fiber particles on liquid flow field in the open impeller of a centrifugal pulp pump,the model pump was constructed by using plexiglas materials,and the flow in the impeller passages was visualized by PIV experimentally with water and 0.1%hair fiber suspension,respectively.The experimental results show that the flow in the impeller passages is stable at high flow rates,and there are no vortex and low-velocity region in the passages.At low flow rates,a low-velocity zone starts to occur near the blade pressure side in the middle portion of a passage when it rotates close to the volute tongue.Additionally,the size of the low-velocity zone gradually increases with decreasing distance of the passage to the tongue and reducing flow rate.Specially,there is no obvious low-velocity zone generated in the passages far away from the tongue.Due to blade twist,the re-lative velocity varies in the blade spanwise direction,and the smaller the twist,the less the velocity varies.When transporting the hair fiber suspension,the relative velocity of liquid phase decreases in the impeller passages owing to the influence of hair fibers,resulting in an increased area of the low-velocity zone under low flow rate conditions.At high flow rates,the existence of hair fibers makes the relative velocity distribution of liquid phase fluid more uniform.