多工况下混流泵叶轮非定常空化特性分析

叶轮空化是降低混流泵水力效率与使用寿命的重要原因之一。为进一步优化叶轮流道,改善混流泵的空化性能,基于计算流体力学方法对某混流式模型泵进行全流道汽液两相流非定常流动数值模拟,以分析0.5Q~1.0Q工况下混流式叶轮的空化特性。重点探究不同空化余量对空泡体积分数的影响,研究空泡的分布特点,捕捉空泡随时间的变化规律。结果表明,在叶轮背面进口边附近最先初生空化,体积组分大的空泡多集中于叶片头部,若空化余量足够低,整个叶轮流道将被空泡占据。随着流量的降低,混流泵的临界空化余量值有所下降,但流量越低空泡严重发展的速度越快,且空泡含量的变化成指数函数增加。

Unsteady cavitation characteristics of mixed-flow pump impeller operating in multi-conditions

Cavitation is one of the key factors that reduce hydraulic efficiency and service life of pump impeller. This study has conducted full-passage CFD simulations of the unsteady gas-liquid two-phase flows in a mixed-flow pumping system to optimize the impeller and improve the pump performance against cavitation, focusing on unsteady cavitation characteristics at operating flow rate in the range of 0.5Q ~1.0Q, spatial distribution and time variation of cavitation, and effects of different net positive suction head (NPSH) on cavitation volume fraction. The results show that cavitation inception occurs at the inlet edges of blade suction sides and cavitation of higher volume fraction gathers near the inlet edges of blades. In the conditions of NPSH lower than a certain threshold, impeller channels will be dominated by cavitation. As the operating flow rate is reduced, the NPSH threshold is decreasing, but serious cavitation is developing faster and cavity content is increasing exponentially.