相同外特性的后掠式轴流泵固液两相分布与缠绕试验

    Solid-liquid two-phase turbulent flow simulation and wound experiment in axial flow pump with back swept blade and same external characteristics

    • 摘要: 针对轴流泵在输送污水介质中的磨损和缠绕问题,设计了外特性相同但后掠角分别为40°和60°后掠叶片,并采用Particle颗粒模型进行固液两相流数值模拟,发现设计流量工况下60°后掠叶片固相分布情况要优于40°后掠叶片,60°后掠叶片压力面上的固相体积分数平均比40°后掠叶片上的固相体积分数小0.1%,60°后掠叶片吸力面上的固相体积分数平均比40°后掠叶片小0.2%。进一步对60°后掠叶片进行研究,发现随着颗粒直径的增加,叶片上的固相体积分数随之增加,且固相集中的区域都很相似;随着初始颗粒体积分数的增加,60°后掠叶片上的固相体积分数也随之增加,但初始颗粒体积分数越大,对后掠叶片压力面上固相体积分数的影响越小。为检验后掠叶片的抗缠绕能力,对60°后掠叶片进行缠绕试验,发现单独的后掠叶片形式的轴流叶轮不易发生缠绕,但当叶轮与套筒配合后,若面对大量棉线,容易在进口边轮缘处发生堆积。该研究为输送污水介质轴流泵的抗磨损和抗缠绕性能的研究提供了参考。

       

      Abstract: Abstract: Demand for urban sewage treatment pumps is increasing annually, especially for sewage axial flow pumps. However, the current design of axial flow pump impeller is with the premise of using water medium, which will lead to serious impeller wear, impeller winding and flow blockage in the actual operation. So it is necessary for the existing axial flow pump impeller design to be modified to adapt to the requirements of the actual delivery of sewage medium. Under the same operation condition, the 40° and 60° back swept impellers were designed and manufactured. Through simulations and pump performance tests, we found that the head curve and efficiency curve of the 2 impellers were basically the same, which verified the reliability of the simulation. Particle model was used to simulate solid-liquid two-phase flow, and we found that solid volume fraction of 60° back swept blade was smaller than that of 40° back swept blade under the designed flow rate. Further, solid volume fraction on pressure surface of 60° back swept blade was 0.1% smaller than that of 40° back swept blade on average, and solid volume fraction on suction surface of 60° back swept blade was 0.2% smaller than that of 40° back swept blade on average. From the simulation results with different particle diameters, we found that with the increase of particle diameter, solid volume fraction of 60° back swept blade increased, and the solid phase concentrated areas were very similar. The radial flow trend of solid phase on the blade pressure surface was stronger and the axial flow trend was weaker; the stronger radial flow meant the solid volume fraction of blade pressure surface should be reduced, while the weaker axial flow trend meant the solid volume fraction of blade pressure surface should be increased. So with the increase of the particle diameter, the axial flow trend was the main factor to solid phase volume fraction on the blade pressure surface. Similarly, on the suction surface, when closer to the inlet, the axial flow trend would be more dominant. From the simulation results, we found with the increase of initial particle volume fraction, the solid volume fraction of 60° back swept blade increased. When the initial particle volume fraction was larger, its impact on the solid volume fraction of the blade pressure surface became smaller. Winding experiments were done with the 60° back swept blade, and we found that when the impeller rotated without sleeve, the anti-winding was strong, but when the impeller rotated with sleeve in water with much cotton, it was easy to block at the rim of the inlet. With different rotating speed, we also found that the faster the rotating speed of the impeller, the faster the cotton hanging on the import edge moved to the flange. This paper provides a reference for the study on anti-wear and anti-winding performance of axial flow pumps.

       

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