隔舌间隙对自吸离心泵自吸性能的影响

Influence of Gap between Impeller and Tongue on Centrifugal Pump Self-priming Performance

为分析隔舌间隙对泵自吸性能的影响及其原因,进一步掌握泵的自吸机理,对外混式自吸离心泵在不同隔舌间隙时的自吸过程进行了高速摄影试验,通过图像处理技术研究蜗壳扩散段内气泡的数量、大小及运动轨迹,同时测量自吸完成时间。研究结果表明,自吸过程中扩散段靠近气液分离室左侧区域的气泡呈现小而密的特点,右侧区域的气泡呈现大而疏的特点。直径较小的气泡在蜗壳扩散段出口更容易被排出,较大的气泡在扩散段内振荡、回旋,不利于自吸的完成。当隔舌间隙从1.0 mm增加到2.5 mm时,经过隔舌进入扩散段的气泡平均直径从1.2 mm增加到1.9 mm,自吸完成时间从28 s上升到113 s,即隔舌间隙越小,进入蜗壳扩散段的气泡直径越小,这是减小隔舌间隙自吸时间缩短的微观机理。

The high-speed photography system was built to investigate the self-priming process of external mixing self-priming pump to analyze the influence of gap between impeller and tongue on self-priming performance of pumps, and then further grasp the self-priming mechanism. The digital images processing technique based on Matlab was applied to compute the number, average diameter and motions of bubbles in the area of diffuser. The tongue gap was resized alad the self-priming time was measured to research the internal relations between the bubbles characteristics and self-priming mechanism. The results show that self-priming process is a complicated unsteady gas - liquid two phase flow and always accompanied by generation, collapse, gathering and splitting of bubbles. During the self-priming process, bubbles in the left area of diffuser are smaller and der^ser, which are easier to be discharged out of the pump. On the contrary, bubbles in the right area vibrate and rotate, which goes against self-priming and wastes energy. When the gap is increased from 1.0 mm to 2..5 mm, the average diameter of bubbles in the diffuser is increased from 1.2 mm to 1.9 mm and the self-priming time is increased from 28 s to 113 s. It means that the bigger the gap is, the bigger diameter of bubbles from tongue to diffuser will be and the longer the self-priming time will be.