开缝叶片低比转数离心泵空化性能的数值模拟

为了进一步提高低比转数离心泵的空化性能,对离心泵叶轮叶片进口附近的开缝进行研究.考虑开缝的3个参数,设计6组水力模型探究开缝对低比转数离心泵性能的影响.针对离心泵运行过程中产生空化的流动特点,基于Rayleigh-Plesset方程来描述空泡成长和溃灭过程的空泡动力学模型,采用RNG k-ε模型对在相同工况下的离心泵中两相流动进行数值模拟与分析.模拟结果表明:在叶片进口处开缝可以提高泵空化性能,其中第二组模型的空化性能提升比较明显,空化余量由4.447 m下降到3.910 m,降低了12.1%,水力效率由71.56%上升至76.46%;在相同工况下,开缝叶轮流道内的能量分布更加均匀,而扬程在额定流量下只有很小的变化.该模拟结果对研究低比转数离心泵内部流动特性及性能的提升具有一定的参考价值.

Numerical simulation of cavitation performance of low specific speed centrifugal pump with slotted blades

In order to improve cavitation performance of a centrifugal pump, a slot is made through each blade near its leading edge in a low specific speed centrifugal pump. Considering three parameters defining a slot, and six hydraulic models are designed. Cavitating flows in these pump models are simulated in CFX by means of steady Reynolds average N-S equations, a cavitation model, which is based on the Rayleigh-Plesset equation, and the RNG k-ε turbulence model. The simulated results show that slots on blade near their leading edge can improve cavitation performance, especially, in the second model the pump cavitation performance is improved more obviously, namely the hydraulic efficiency is increased to 76.46% from 71.56%, and the NPSH is decreased to 3.910 m from 4.447 m, resulting in a 12.1% reduction. At the duty flow rate, the energy inside the flow channels between the two blades is more uniformly distributed, while the head remains changed a little. The simulated results may have some referential value for investigating features of internal flow in a low specific speed centrifugal pump and its performance improvement.