文档介绍：The pressure reduction profile within the pump is depicted in Figure 9.

Figure 9: Pressure Profile in a Pump
As shown in Figure 9, the impeller eye is the point where the static pressure is at a
minimum, p4. During pump operation, if the local static pressure of the liquid at the
lowest pressure es equal to or less than the vapor pressure (pv) of the liquid at the
operating temperature, vaporization of the liquid (the formation of bubbles) begins .
when p4 £ pv.

It is at the beginning of the trailing edge of the vanes near the impeller eye where the
pressure actually falls to below the liquid vapor pressure. The region of bubble formation
is shown in Figure 10.

Centrifugal Pumps: Basics Concepts of Operation, Maintenance, and Troubleshooting, Part II
By: Mukesh Sahdev, Associate Content Writer
Presented at The Chemical Engineers’ Resource Page,
Figure 10: Impeller Cavitation Regions
In summary, vaporization of the liquid (bubble formation) occurs due to the
reduction of the static pressure to a value below that of the liquid vapor pressure. The
reduction of static pressure in the external suction system occurs mainly due to friction in
suction piping. The reduction of static pressure in the internal suction system occurs
mainly due to the rise in the velocity at the impeller eye.
Step Two, Growth of bubbles
Unless there is no change in the operating conditions, new bubbles continue to form and
old bubbles grow in size. The bubbles then get carried in the liquid as it flows from the
impeller eye to the impeller exit tip along the vane trailing edge. Due to impeller rotating
action, the bubbles attain very high velocity and eventually reach the regions of high
pressure within the impeller where they start collapsing. The life cycle of a bubble has
been estimated to be in the order of seconds.
Step Three, Collapse of bubbles
As the