基于改进欧拉算法的双吸离心泵泥沙磨损特性研究

固液两相流算法对双吸离心泵泥沙磨损模拟精度有直接影响。采用改进的固液两相流欧拉算法,考虑了相间阻力和泥沙扩散系数两方面因素,对典型悬移质泥沙粒径条件下的双吸离心泵流场进行了数值计算。研究发现,叶片表面湍流强度在头部和尾部较大,可达6%~10%;叶片头部和尾部的颗粒动态尺度大于中部。由湍流强度和颗粒动态尺度组成的湍动尺度效应,在叶片头部和尾部表现强烈,湍动尺度效应使固液相间阻力增大,更有利于颗粒的扩散,避免了颗粒聚集,对大颗粒的作用强于小颗粒。湍动尺度效应导致叶片表面固相体积分数分布范围减小,大颗粒的变化值大于小颗粒,叶片头部和尾部的改变值大于中部,叶片表面的严重磨损部位为叶片工作面尾部的块状磨损区,这比采用传统算法得到的带状磨损区和偏磨区计算结果,更符合离心泵实际磨损情况,考虑湍动尺度效应后得到的磨损率也有所增大。在此基础上,提出了双吸离心泵叶片水力设计和表面喷涂防护原则,为提高双吸离心泵抵抗泥沙磨损能力奠定了基础。

Erosion Characteristics of Double Suction Centrifugal Pump Based on Modified Eulerian Algorithm

The computational accuracy for sediment erosion numerical simulation of double suction centrifugal pump is influenced by solid-liquid two phase flow algorithm. The modified Eulerian algorithm for solid-liquid two-phase flow was adopted, both characteristics of inter-phase drag force and sediment diffusion coefficient were considered in the modified algorithm. Then the flow field of double suction centrifugal pump was simulated for typical suspended load sediment particle diameters. The results showed that the turbulence intensity on the front and back of blade were greater, which were 6%~10%. The particle dynamic scales were greater on the front and back of blade rather than on the middle of the blade in consideration of the location. The turbulence scale effect was composed of the turbulence intensity and the particle dynamic scale. The turbulence scale effect gave more obvious influence on the front and back of blade rather than on the middle of the blade. The particles were easier to diffuse because of the increasing inter-phase drag force led by the turbulence scale effect, the particles gathering phenomenon was then avoided. The turbulence scale effect gave more obvious influence on large particles rather than on small particles in consideration of the particles scale. So interval range between maximum value and minimum value of the calculated solid concentration distributions on blade pressure surface was decreased. The calculated solid volume fraction had larger variation for the large particles than the small particles, and larger variation on the front and back of blade than the middle of blade, because turbulence scale effect was considered. The block erosion area located in blade pressure surface trailing edge was severe erosion area, the result calculated by the modified algorithm was agreed well with the actual erosion conditions of centrifugal pump rather than the results of the zonary erosion area and partial erosion area calculated by traditional algorithm. There was an increase in the erosion ratio with the turbulence scale effect considered. Then on this basis, the principles of the blade hydraulic design and the blade surface spraying protection for double suction centrifugal pump were proposed. The principles laid the foundation for improving abrasion resistance of double suction centrifugal pump.