轴流泵叶顶泄漏涡空化的数值模拟与可视化实验研究

NUMERICAL SIMULATION AND VISUALIZATION STUDY ON TIP LEAKAGE VORTEX CAVITATION IN AN AXIAL-FLOW PUMP

该文以某一等比例缩放模型泵为研究对象,采用修正的SST k-ω湍流模型和空化模型,对额定工况下轴流泵叶顶泄漏涡空化流进行了数值模拟,并与高速摄影结果进行了对比分析。探讨了叶顶区域泄漏涡空化流场结构,揭示了不同空化数下空化发生位置和空泡形态演变过程。研究结果表明,改进的数值模拟方法准确计算了叶顶区域空化流场的流动结构;轴流泵的初生空化为叶顶间隙空化和叶顶泄漏涡空化,随着空化数σ降低,叶顶泄漏涡卷吸区也出现了剪切层空化;在空化数较小工况下,沿着叶片吸力面在轴向形成空泡云,并在叶片尾缘存在周期性的空泡脱落和爆破过程,破坏了流动稳定性,并诱导产生空化噪声。

Tip leakage vortex cavitation in a scale-model of axial flow pump model at design conditions was simulated using a modified SST k-ω turbulent model and a cavitation model. Numerical results were compared with the high-speed photography experimental data. The structure of a tip leakage vortex cavitation flow field was discussed and the evolution of cavitation bubble cloud was revealed at different cavitation conditions. Investigation results show that the modified numerical method in this paper could simulate the tip leakage vortex cavitation in the tip region of the impeller. The cavitation inception in an axial flow pump occurs in the tip clearance and leakage vortex regions. With cavitation number σ decreasing, the cavitation region is expanded to the rolling-up zone of the tip leakage flow. At a small cavitation number σ condition, the bubble cloud occurs in the suction sides of blades at the axial direction, which could induce flow instability and cavitation noise.