离心泵汽蚀特性分析

根据离心泵汽蚀余量的计算公式来分析影响泵汽蚀特性的因素,主要包括泵体设计和叶轮进口设计.假设泵进口来流无预旋,将由流动变量表征的泵汽蚀比转速公式,改写为由几何参数也就是反应泵体设计和叶轮进口设计的两个系数以及进口叶片安放角和轮毂比表示的形式,并通过绘制汽蚀比转速的图谱来分析影响泵汽蚀比转速的设计因素.通过图谱发现,获得最高汽蚀比转速对应的最优进口叶片安放角在10°-30°之间,叶轮进口处的设计比泵体的设计对泵汽蚀比转速的影响大.另外,根据初生汽蚀比转速的计算公式认为,基本上所有的离心泵都在汽蚀状态下工作.划分了离心泵的容许汽蚀运行区域的边界,即扬程下降0.5%时对应的汽蚀比转速曲线.

Analysis on cavitation characteristic in centrifugal pump

According to the formula of net positive suction head of centrifugal pump, the main factors which affect pump cavitation are the design of pump casing and impeller inlet. The formula of cavitation specific speed is rewritten into a new form related with blade inlet angle, hub-tip ratio and the two factors mentioned above. A diagram is drawn to show the design variables that have effect on the cavitation specific speed. By the diagram, it can be deduced that the optimum blade inlet angle for maximum cavitation specific speed is in the range of 10 to 30 degres. The factor related with impeller has more effect on the cavitation specific speed than that with casing. The cavitation incipient criteria show that any pump works under the condition of cavitation. Therefore, a valid curve, which corresponds to the 0. 5% head-drop curve, is recommended here to limit the running range for pump at cavitation condition.