Is the centrifugal pump large or small?
Centrifugal pump, the smaller the better the cavitation.1, centrifugal pump cavitation less, anti cavitation performance is better, the pump cavitation is called the necessary cavitation margin or pump inlet dynamic pressure drop, the smaller the better. Generally speaking, the pump cavitation is the need for cavitation, the pump inlet pipe said effective cavitation margin, that is, the device cavitation margin. For a given pump, at a given speed and flow rate required NPSH is called pump necessary NPSH, also called NPSH, is required to achieve the performance parameters of the pump cavitation, the internal flow and the centrifugal pump is composed of pump head itself, its physical meaning is that liquid drop in pump inlet pressure part degree, is to guarantee the pump cavitation does not occur, with surplus energy exceeds the vaporization pressure head at the inlet of the pump unit weight of liquid. The cavitation must be independent of the device parameters. It is only related to the parameters of the inlet of the pump. These parameters are determined by the geometric parameters at a given speed and flow.
NPSH is also called cavitation, cavitation is too big to be.3, pump the liquid when working in the impeller inlet will produce vapor due to a certain vacuum pressure, vaporization of the air bubbles in the liquid particle movement under the impact of erosion on the impeller, the metal surface, thus undermining the impeller and other metal, then vacuum pressure is called vaporization pressure, NPSH is excess vaporization pressure of surplus the energy position of the unit weight of the liquid in the pump suction port of. The unit with annotation, (NPSH) r with. The absorption process is necessary NPSH H: pump suction fluid allows the vacuum pump installation height is allowed, in meters.
When the liquid is lowered at a certain temperature to the vapor pressure at this temperature, the liquid bubbles. The phenomenon of producing bubbles is called cavitation. When the bubbles are flowing to the high pressure, the volume of the bubbles is reduced so that they are destroyed. This due to the pressure of rising bubbles disappear in the liquid in the phenomenon called cavitation bubble collapse. The local pump is in operation if the over-current part (usually the impeller blade inlet somewhere later) for some reason, the absolute pressure of pumping the liquid was reduced to liquid vapor pressure temperature, liquid vaporization began there, produce a lot of steam bubble formation, when the liquid contains a lot of bubbles by forward high pressure impeller Zone, high pressure liquid around the bubbles in the bubble decreases drastically and rupture. Condensation in the bubble burst and the liquid particle at high speed to fill a hole in this moment has a very strong effect of water hammer and the impact of high frequency against the metal surface, the impact stress of hundreds to thousands of atmospheric pressure, impact frequency can be up to tens of thousands of times per second, serious breakdown when the wall thickness will be. The process of cavitation in a pump is caused by the bursting of bubbles and bubbles in the water pump and the destruction of the over-current components. Water pump cavitation, in addition to the over-current components will have a destructive effect, but also produce noise and vibration, and lead to the performance of the pump down, seriously when the pump will be interrupted liquid, can not work properly.
