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Before talking about the cavitation of multistage centrifugal pumps, let's understand the vaporization of liquids; the pressure when liquids vaporize is the vaporization pressure of liquids, also known as saturated vapor pressure. The vaporization pressure of a liquid is related to the temperature. The higher the temperature, the more intense the molecular motion and the greater the vaporization pressure. The vaporization pressure of water at room temperature at 20°C is 233.8Pa, while that of water at 100°C is 101296Pa. Therefore, when the pressure drops to 233.8Pa, clean water at room temperature at 20°C will start to vaporize. It can be seen that pressure is an external factor that promotes the vaporization of liquid at a certain temperature.
When the multistage centrifugal pump transports the medium at a certain temperature and reduces the pressure to the vaporization pressure at that temperature, the medium will produce gas-filled bubbles, which is the root cause of the cavitation of the multistage centrifugal pump. Air or other bubbles decomposed from the conveying medium have a different effect on cavitation than steam bubbles. The bubbles generated during the cavitation of the multistage centrifugal pump will decrease in volume and burst when they flow to a high pressure place. This phenomenon of bubbles disappearing in a liquid due to pressure rise is called bubble collapse.
The root cause of cavitation in horizontal multistage centrifugal pumps is that the absolute pressure of the liquid is lower than the vaporization pressure.
Caused by a decrease in internal pressure. The following is a brief introduction to the performance of cavitation in horizontal multistage centrifugal pumps:
1. Generate vibration and noise;
2. Corrosion and damage of wetted parts;
3.性能下降。