Abstract: In order to take into account the local density of gas-liquid mixing area in cavitation flow field in impeller tip region of axial flow pump, the turbulent viscosity term in SST k-ω turbulence mode was corrected. NPSH curves, cavitation characteristic and blade loading were analyzed based on full cavitation model with simulation and experimental methods. The investigation results show that the modified SST k-ω turbulence model and cavitation model can predict the cavitation flow field with gas-liquid two-phase flow in the impeller tip region, and the relative error of the critical cavitation number between experimental and predicted values is 7.79% under design conditions, which is satisfactory for the computational accuracy. The high speed phohography experiments show that the cavitation inception is induced by blowing cavitation, clearance attached cavitation and tip leakage vortex cavitation, and the cavitation region continually spreads with the decrease of cavitation number. The break of cavitation bubble cluster occurs at the aft of the blade, and the position of bubble break moves toward the middle of the blade span. The angular interval between -13° and +13° is the main region of the suction side with low pressure. Within the 3% area attached to the blade tip clearance, the pressure gradually decreases with the increase of radius coefficient r^*, decreasing the blade surface loading. Near the tip clearance, the blade loading decreases more obviously.

Key words: axial-flow pump, cavitation, blade loading, numerical simulation, high speed photograph

摘要： 针对轴流泵叶顶区空化流气液混合区域密度变化，以SST k-ω湍流模型为基础，对湍流黏度项进行了修正。基于输运方程的完全空化模型对轴流泵NPSH曲线、空化特性及其叶片载荷进行了数值模拟和分析，并与实验结果进行了对比。研究结果表明，修正的SST k-ω湍流模型和空化模型较准确地预测了叶顶区空化流，临界空化数预测误差为7.79%。通过高速摄影实验观测到轴流泵的初生空化为刮起涡空化、间隙附着空化和涡带区空化，空化区域也随着空化数的降低而不断扩大，直至在叶片后缘脱落和爆破，爆破位置也不断向叶片中部移动；叶片吸力面的低压区主要集中在叶顶翼型间隔角为-13°～+13°的区域；在叶轮叶顶间隙的3%区域，随着半径系数增大，叶片压力面压力逐渐减小，叶片载荷不断降低，且越接近间隙边缘，叶片载荷降低越明显，从机理上找到了空化诱导轴流泵性能下降的原因。

关键词: 轴流泵, 空化, 叶片载荷, 数值模拟, 高速摄影