外混式自吸离心泵瞬态高速摄影试验

为了研究自吸泵在自吸过程中的内部流动变化,设计了可视化自吸离心泵样机,利用LABVIEW虚拟仪器记录了自吸泵在自吸过程中压力、流量、转速等参数随时间的变化,研究了转速对自吸泵出口压力及自吸时间的影响.同时通过高速摄影试验,拍摄了各阶段自吸泵关键部位的气液两相流动状况,分析了自吸泵在自吸过程中气液两相的变化规律.研究结果表明:根据压力和流量随时间的变化规律,自吸泵的自吸过程可以分3个阶段,分别为自吸启动阶段、自吸稳定阶段和自吸突变阶段,且不同转速下的出口压力变化规律也符合这一特征; 叶轮转速越大,自吸泵出口压力在自吸稳定阶段的波动幅度越大,最终稳定的压力值越大,且自吸时间越短; 在自吸过程中,蜗壳和叶轮流道内均存在气泡分裂现象,单个大气泡逐渐拉长呈哑铃状,后随着气泡中间连接通道的消失,分裂成2个小气泡,以促进气体的排出和自吸的完成.

High-speed photography experiment on transient air-water flow in self-priming centrifugal pump with separation chamber

To study the variation of internal flow in self-priming process of the self-priming centrifugal pump, a flow visualizable transparent self-priming centrifugal pump prototype was designed. The pressure, flow rate and rotational speed, etc., were recorded in the self-priming process of the pump with Labview virtual instrument in time domain, and the influence of rotational speed on the outlet pressure and self-priming time of the pump was investigated. Meanwhile, the air-water two-phase flow patterns in the key components of the pump were shot with a high-speed camera at various stages of the self-priming process, and transient variations of the two-phase flow in the pump were analyzed. The results show that the self-priming process of the pump can be divided into three stages in terms of the variations of pressure and flow rate with time, i.e., start-up, stable and sudden change stages. This feature can also be observed in the outlet pressure profiles at different rotating speeds. In the stable self-priming stage, the faster the impeller rotating speed, the larger the fluctuation amplitude in the outlet pressure, the higher the final stable pressure and the shorter the self-priming time. Bubble splitting phenomenon exists in the volute and impeller during the self-priming process. Firstly, a single large bubble is gradually elongated into a bubble in dumbbell shape. Then the connecting channel in the middle of the bubble disappears and the bubble is split into two small ones to promote air separation and complete the self-priming process.