旁通装置控制离心泵空化特性的数值模拟与试验

为了研究旁通水路对离心泵空化性能的影响规律,以一台比转速为32的低比转速离心泵为研究对象,在蜗壳第八断面靠进口侧位置处至吸入段搭建一旁通管路。采用修正的SST k-ω湍流模型和Kubota空化模型,在不同空化数下,对原型泵和带有旁通水路的离心泵进行三维非定常数值模拟,并同试验结果进行对比。结果表明:低比转速离心泵在搭建旁通水路后运行时扬程和效率均有小幅下降,在设计工况下,试验值中扬程下降2.30%,效率下降3.07%,模拟值中扬程下降3.10%,效率下降1.80%。空化初生及发展阶段,旁通水路可以有效增大近壁湍动能,改善压力分布,抑制空泡增长及脱落,改善流场结构;扬程断裂后,旁通水路不能有效抑制空化反而加剧了其严重程度。旁通水路对其涉及流域内压力脉动造成小幅扰动。

Numerical simulation and tests for cavitation characteristics of centrifugal pump controlled by bypass device

In order to study the influence law of bypass waterway on cavitation characteristics of centrifugal pump,a low specific speed centrifugal pump with a specific speed of 32 was taken as the study object,a bypass waterway was built from the eighth section of the volute near the inlet side to the suction section.The modified SST k-ω turbulence model and Kubota cavitation model were used to do the 3-D non-steady numerical simulation for the original type pump and the pump with the bypass waterway under different cavitation numbers.The simulation results were compared with test ones.Results showed that both head and efficiency of the low specific speed centrifugal pump decrease slightly after building the bypass waterway;under the designed working condition,test values of head and efficiency decrease by 2.30% and 3.07%,respectively and simulated values of head and efficiency decrease by 3.10% and 1.80%,respectively;in initial and development stage of cavitation,the bypass waterway can effectively increase near-wall turbulent kinetic energy,improve pressure distribution,restrain growth and fall off of cavitation and improve flow field structure;after head is broken,the bypass waterway can’t effectively restrain cavitation,but aggravate its severity;the bypass waterway causes a small disturbance to the pressure fluctuation in flow field involved.