基于近壁湍流拟序结构的离心泵内沙粒冲蚀角研究

流体机械中的泥沙磨损现象是一个国内外至今尚处于探讨阶段的问题。多年来有关学者们从试验、计算、理论研究等多方面对这一现象进行了大量的研究与探讨。本文尝试从近壁区湍流的拟序结构出发,研究离心泵内的泥沙磨损问题。文中首先从沙粒近壁BBO方程出发得出了沙粒近壁区法向运动速度upy,然后基于拟序结构导出了沙粒"扫掠"情况下的流向速度upx。最后用两个速度得到了基于近壁湍流拟序结构的离心泵内的沙粒对叶轮壁面的冲击角。研究表明在离心泵内正是由于近壁区湍流拟序结构时的"扫掠"作用造成了小粒径沙粒在叶轮壁面附近的小角度切削破坏,这与国外学者的试验观测结果相吻合。

Study on sand erosion angle in centrifugal pump based on burst structure of near-wall turbulences

Sand abrasion in fluid machinery remains at the exploratory stage in spite of tremendous previous efforts in experimental, numerical and theoretical studies in recent years. This paper presents a preliminary study on sand abrasion in centrifugal pump from the perspective of turbulent coherent structure in near-wall region. We derive the near-wall sand velocity normal to the wall using the BBO equation of sand motion, and obtain the sand velocity along the local flow in a sweep considering the behaviors of burst structure. Then, we can calculate the impact angle of sand particles on the impeller surface of a centrifugal pump. The results show that in a centrifugal pump, the small angle cutting damage of small sand particles to impeller surfaces is caused by the sweep of coherent structures in near-wall turbulences. This conclusion is supported by previous experimental tests in literature.