Cavitation is a kind of high-noise and very destructive phenomenon that often occurs in hydraulic machinery. In vacuum acquisition equipment, the cavitation of water ring DVE vacuum pumps is also well-known, and the damage to DVE vacuum pumps is accumulated over time. The process is easy to cause perforation of the impeller.

Its generation principle is: due to the action of hydrodynamics, when the partial pressure of the moving liquid is reduced to the vaporization pressure at this temperature, the liquid begins to vaporize and form a vapor bubble. The vapor bubble is filled with liquid vapor and a small amount is dissolved in the liquid. gas. When the bubble reaches the area where the static pressure exceeds the critical pressure with the moving liquid, the vapor in the bubble suddenly condenses and the bubble bursts.

Because the pressure in the bubble is always lower than or close to the critical value, and the pressure of the outside liquid is relatively large, when the bubble bursts, the surrounding liquid rushes to the center of the bubble at a high speed to form a high frequency The action of water hammer produces high local stress and local temperature rise, and generates noise and vibration.

The repeated process of the generation and destruction of this kind of bubbles will cause damage to the surface of the parts in this area, coupled with the chemical and electrochemical corrosion effects of the liquid and the parts materials, and finally result in a sponge or honeycomb-like characteristic vapor. Eclipse damage.

Studies have also shown that even above the critical pressure, cavitation may occur. Because when the pressure is reduced, the air and other gases dissolved in the liquid will be analyzed, and the vapor of the liquid will also be brought out to form bubbles filled with liquid vapor and gas. These bubbles are especially easy to produce on the surface of the moving parts. When it grows up, it is taken away by the liquid, and it suddenly condenses and bursts when the pressure is high. The critical pressure at which cavitation occurs varies with the nature of the liquid, the temperature and the nature of the dissolved gas.

According to the information about the water pump, for degassed water at room temperature, the saturated vapor pressure equivalent to the water temperature can be used as the critical pressure value for the occurrence of vapor bubbles.
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