轴流泵叶轮汽蚀两相流的数值模拟与分析

为了分析某型号轴流泵叶轮汽蚀状态下汽液两相流特征,本文基于均相流模型、RNG k-ε湍流模型与SIM-PLEC算法,分别从外特性和内部流场两方面分析了轴流泵叶轮的空化过程,通过定量分析不同NPSH下轴流泵的扬程下降和空泡分布的对应关系,讨论了不同空化状态下叶轮内部速度场和压力场的分布,寻找出轴流泵空化发生破坏的位置和发展趋势。数值模拟结果表明,空化初生时空泡产生于叶片背面进口轮缘处,随着轴流泵进口压力的不断降低,叶片背面外缘处空泡逐渐向轮毂侧发展,且外缘侧空泡不断向前推进,在装置汽蚀余量NPSH为6.62m时,空泡基本覆盖叶片的背面,此时叶片丧失了部分做功能力,且扬程下降明显。计算模型泵进行了现场运行试验,试验结果表明,数值模拟的空泡分布与实际破坏位置一致,验证了数值计算的准确性,也为解决轴流泵汽蚀破坏问题提供了内流流场参考。

Experiment and Numerical Simulation of Cavitation Flow in Axial-flow Pump Impeller

In order to investigate the characteristics of vapor-liquid two-phase turbulent flow in submersible axial-flow pump,the cavitations process in impeller was analyzed based on homogeneous model,RNG k-ε turbulent model and SIMPLEC algorithm from the external characteristics and internal flow field.The correspondence between the vacuoles distribution and head drop of axial pump under the conditions of different NPSH values was discussed,and the velocity and pressure field in the impeller under different cavitations were analysed to find the cavitation damage position of axial flow pump impeller.Numerical simulation results show that the bubbles occur at the suction side of blades near the rim in the early cavitation process.With the decreasing of inlet pressure,the bubbles near rim of suction side of blades gradually develop to the hub region.The mode pump was tested in the sewage treatment plant of Nanjing Jiangxizhou,and the experimental results show good agreement with numerical results.The bubble distribution predicted by numerical simulation is consistent with the actual destruction position of the blades,and the accuracy of numerical simulation was verified.The conclusions will provide reference for solving cavitation problems in the axial-flow pump impeller.