Cavitation allowance of water pump
I. Cavitation process:
The pressure at which a liquid vaporizes is called vaporization pressure (saturation vapor pressure). The pressure at which a liquid vaporizes is related to temperature. The higher the temperature, the greater the pressure at which the molecules move more violently.The vaporization pressure of fresh water at 20℃ is 233.8Pa, and that of water at 100℃ is 101296Pa(one atmosphere).It can be seen that pressure at a certain temperature is an external factor contributing to the vaporization of liquid.When a liquid at a certain temperature is reduced to the pressure of vaporization at that temperature, bubbles are formed in the liquid. This phenomenon is called cavitation erosion.
Cavitation bubbles reduce in size and burst as they flow to high pressure.This rise in pressure and the disappearance of bubbles into the liquid is called cavitation collapse.
In order to ensure that the pump is not cavitation, the pump impeller inlet unit weight of the liquid must have more than the vapor pressure of excess energy.The following is a brief explanation:
When centrifugal pump suction height and the liquid at high temperature, as to make the suction pressure of less than or equal to the saturated vapor pressure of liquid liquid will boil at the pump inlet, vaporization in the pump shell to form a space filled with steam, with the pump rotation, bubbles into the high, due to the differential effect, compression of air bubble burst and condensation, again, at the moment of condensation particle smashed into each other, producing a high partial pressure, if the bubbles near the metal surface cracking and condensation, the liquid particle is like countless small warhead, continuous hit in the metal surface, the surface cracks on wire products, metal and even local produce flaking off,The impeller surface is honeycomb, at the same time some active gas such as oxygen bubble into the metal surface crack, with the help of the heat released when the bubble condensation, the metal by chemical corrosion, the phenomenon.