轴流泵叶轮区域空化特性数值模拟

为了研究轴流泵内部叶轮区域空化特性,该文基于ANSYSCFX软件,分别应用Standardκ-ε,RNGκ-ε,κ-ω和SSTκ-ω湍流模型、均质多相流模型,对比转数ns=1033轴流泵在不同工况下进行全流道数值计算,将模拟值与试验结果进行对比分析,验证不同湍流模型及多相流模型的适应性并探究叶轮区域的空化特性。结果表明:在设计工况下,基于κ-ω湍流模型较其他3种湍流模型计算准确,临界汽蚀余量NPSHc计算值与试验结果误差为6.32%,可以较好反映轴流泵内部空化特性。随着有效汽蚀余量NPSH值的减小,空化首先在叶片背面进口靠近轮缘处发生,然后沿着主流方向往叶片中部发展直至充满整个流道,在临界汽蚀余量工况下,叶片中部区域空化面积较大,空化较严重时,叶片背面流线在叶片后部较紊乱,在靠近轮毂处形成漩涡微团,并向轮缘处移动,同时引起叶轮出口截面处轴面速度分布不均匀,增加了叶轮区域流场的紊乱性,揭示了叶轮区域内部空化流动特性。

Numerical simulation on cavitating characteristic in impeller of axial-flow pump

In order to study the internal cavitation characteristic of axial flow pump,the steady turbulent flow field of an axial flow pump(ns=1033) at different conditions was simulated by using standard κ-ε turbulence model,RNG κ-ε turbulence model,κ-ω turbulence model,SST κ-ω turbulence model and homogeneous multiphase model based on ANSYS CFX software.The numerical results were compared with the experiment values to verify the adaptability of the different turbulent models and multiphase model,and to study the cavitation characteristics of the impeller region.The results showed that the κ-ε turbulence model has better accuracy than the other three turbulent models in simulation,predictive errors of critical NPSHc is 6.32%,which can reflect the internal cavitation characteristic of the axial flow pump well.With the decrease of the NPSH,along the flow direction,vapor first occurred on the leading edge of the blade close to the tip,and then developed to the middle area of the blades until to the whole passage.On the critical cavitation condition,the vapor area of the middle side along the radical direction of the blade is large.When the cavitation is serious,the streamline at the back of the blade’s suction side is disorder and generate the vortex micro group,which will flow from the hub to the shroud of the impeller,cause the distribution of axial flow velocity at the outlet of the impeller inhomogeneous,and increase the disturbulence of the flow field in impeller region.These phenomena reveal the cavitation characteristics of the axial-flow pump.