离心泵内纤维悬浮流的PIV实验及CFD-DEM模拟研究

Study on Internal Flow Field of Centrifugal Pump based on PIV Test and CFD-DEM Coupling

中文关键词:  纸浆泵  CFD-DEM  PIV  内流场  纤维

Key Words:pulp pump  CFD-DEM  PIV  internal flow field  fiber

中文摘要:

      为研究离心泵叶轮流道内纤维颗粒对液相流场的影响，首先采用CFD-DEM耦合方法模拟离心泵内纤维颗粒悬浮液的流动情况；然后采用透明有机玻璃材料制造模型泵，通过外特性实验及PIV实验对叶轮流道内头发纤维悬浮液的流动进行可视化实验验证；最后基于PIV实验结果对叶轮流道内流场进行分析。结果表明，随着泵内纤维质量浓度提高，泵效率随之提高；纤维质量浓度达到0.2%时，明显呈现出减阻效应。在小流量工况下，当输送相同质量浓度纤维时，沿叶轮流道中段压力面附近会产生低速区，且低速区随着流量的减小逐渐向中间流道扩散；叶片扭曲程度会影响垂直于泵轴的不同截面叶轮流道内相对速度分布，随着叶片扭曲程度增大，各位置相对速度差值增大；纤维质量浓度的变化会影响叶轮流道内相对速度分布，当流量逐渐增大时，较高质量浓度纤维悬浮液内液相相对速度会逐渐超过低质量浓度纤维悬浮液。在大流量工况下，各质量浓度纤维悬浮液在叶轮流道内从吸力面至压力面的相对速度总体呈下降趋势。

Abstract:

      In order to study the impacts of fiber particles on the liquid flow field in the impeller passage of a centrifugal pump， the CFD-DEM coupling model was used to simulate the flow of fiber suspension in the pump. A model pump made of transparent organic glass was used to perform the experimental tests. Visual verification of the flow of fiber （hair） suspension in the impeller passage was conducted through the external characteristics experiment and PIV test. The flow field in the impeller passage was analyzed based on the PIV results， which indicated that the pump efficiency was improved by the increase of the fiber mass concentration in the pump. The drag reduction effect was clearly observed as the fiber mass concentration reached 0.2%. When fibers of the same mass concentration were transported under small flowrate， a low-speed zone near the pressure surface along the middle of impeller passage was generated. The low-speed zone would gradually spread to the middle passage with the decrease of flowrate. Distortion of blade curvature would affect the relative velocity distribution in different cross-sections along impeller passage perpendicular to the pump shaft. Specifically， the difference of relative velocity between different positions would increase as the distortion extent of blades continued to increase. The relative velocity distribution in the passage was affected by the mass concentration， the relative velocity of the liquid phase in high concentration fiber suspension gradually exceeded that of the low concentration fiber suspension as the flowrate increasing gradually. Meanwhile， the relative velocity from suction side to pressure side in the impeller passage of various concentration of suspension tended to decrease under large flowrate.