多工况高抗汽蚀性能的诱导轮设计

针对某流量调节范围（最大流量/最小流量）为30的低比转数高速离心泵,基于能量匹配法,设计了等螺距和变螺距2种结构形式的诱导轮.采用SST湍流模型和Rayleigh-Plesset空泡动力学模型,对离心泵多工况下的全流场进行汽蚀数值模拟,分析了离心泵多工况下的汽蚀断裂特性和气泡分布等流场特征,揭示了不同工况下带诱导轮离心泵的汽蚀断裂机理.在高速试验台上进行了离心泵外特性水力试验,试验结果与计算结果吻合较好.研究结果表明：能量匹配法是指导高抗汽蚀诱导轮设计的基本方法;随着进口压力的降低,带诱导轮离心泵在各工况下的汽蚀断裂特性不尽相同,大流量工况下的扬程断裂曲线呈大斜率形状快速下降,中流量工况下扬程断裂曲线呈直角形,小流量下扬程断裂曲线呈小斜率形状缓慢下降;相对于等螺距诱导轮,变螺距诱导轮具有更小的冲角和更高的扬程,使高速离心泵具有更宽的稳定工作区间.

Design of inducer with excellent suction performance under multi-operating conditions

Two inducers respectively with constant- anti variable-pitch are designed to improve the suction performance of a low specific speed centrifugal pump with a flow rate ratio of 30 （ maximum flow rate over minimum one） based on a design principle that the head generated by an inducer should match the suction head of the main impeller of a pump. The cavitating flows in the centrifugal pumps with two inducers are simulated by using the SST turbulence model and the mixture cavitation model under a few working conditions, and the head breakdown characteristics and bubble distribution features are analyzed to disclose the mechanisms for the head breakdown caused from cavitation at various flow rates. The performance curves of the pumps with the two inducers are measured on a high-speed pump test rig. The predicted hydraulic and suction performance curves are compared with the measurements, and good agreement is achieved. It is confirmed that the design principle adopted here can be as an essential guidance on design of inducer with excellent suction performance. The head breakdown curves with decreasing inlet pressure are different from one flow rate to another. The slope of the head breakdown curve at a high flow rate is sharper than that at a low flow rate and the head declines slowly with reducing net positive suction head available. The shape of the curve at a middle flow rate is in rectangular shape. Compared with the constant-pitch inducer, the variable-pitch inducer is subject to an even smaller incidence angle and even high head, allowing a high-speed centrifugal pump to have a more wide range of flow rate for stable operation.