不同叶顶间隙下斜流泵内部 流动特性的数值模拟

为研究轮缘叶顶间隙对斜流泵性能和流动不稳定特性的影响,基于SST k-ω湍流模型对某斜流泵选取了0, 0.25, 1.00, 2.00 mm 4种尺寸的叶顶间隙进行数值计算,分析间隙区域内压差分布、泄漏量、叶顶泄漏涡旋强度以及进口轴面速度分布.结果表明:不同运行工况下,斜流泵泄漏量从叶轮进口到叶轮出口先增大后减小,其与间隙区内压差变化趋势相吻合.叶顶泄漏量随着间隙尺寸的增大而增大,导致泵的能量损失增大.经对比发现,间隙尺寸是影响叶顶泄漏量的主要因素.小流量工况下,随着叶顶间隙尺寸的增大,叶顶泄漏流与主流卷吸作用形成的泄漏涡强度逐渐增强.部分泄漏流进入相邻叶片通道,导致其流动失稳.随着叶顶间隙的增大,斜流泵能量损失明显增多,且内流不稳定性明显加剧.增大流量后,不同间隙下叶顶泄漏涡旋转强度均逐渐降低.

Numerical simulation of different blade tip clearances on internal flow characteristics in mixed-flow pump

To investigate the effects of tip clearance on the performance and unsteady flow in the mixed-flow pump, four sizes of tip clearances, 0, 0.25, 1.00, 2.00 mm, were selected to conduct simulation calculation based on SST k-ω turbulence model. The pressure difference distribution, lea-kage flow rate, inlet axial velocity distribution and tip leakage vortex rotation intensity were analyzed. The results show that the leakage of the model pump from impeller inlet to impeller outlet shows a ten-dency of increasing first and then decreasing under different operating conditions, which is the same as the variation trend of pressure difference in the clearance. With the increase of the gap size, the lea-kage of the blade tip also increases, which leads to the increase of the energy loss of the pump. It is found by comparison that the clearance size is the main factor affecting the leakage. Under the part-loading conditions, the rotation intensity of the leakage vortex formed by the interaction between tip blade leakage flow and main flow gradually increases with the increase of blade tip clearance.Part of leakage flow enters the passage of adjacent blades, leading to flow instability. As a result, the energy loss and flow instability of the pump show an increasing trend with the increase of gap size. With the increase of flow rate, the rotation intensity of tip leakage vortex gradually decreases at different clearances.