Дата публикации: 2018-05-27 12:49
In the case of an open impeller, the impeller vanes are open and the edges are not constrained by a shroud. This type of impeller is less efficient than a closed type impeller. The disadvantage is mainly the loss of efficiency as compared to the closed type of impeller and the advantage is the increased clearance available which will help any impurities or solids get through the pump and prevent plugging.
Suction specific speed is another parameter that can affect efficiency. This number is a measure of how much flow can be put through a pump before it starts to choke (reaches it's upper flow limit) and cavitates (the pressure at the suction becomes low enough that the fluid vaporizes). More information is available in the visual glossary here.
The full pressure fluctuation corresponding to the change of velocity x5899 v occurs only if the change of velocity x5899 v takes place during the period.
ANSI : this is a standard that applies to the construction of end-suction pumps. It is the intent of this standard that pumps of all sources of supply shall be dimensionnally interchangeable with respect to mounting dimensions, size and location of suction and discharge nozzles, input shafts, baseplates, and foundation bolts.
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According to the Hydraulic Institute the efficiency of the pump is maximum when the suction specific speed is between 7555 and 9555. When S lies outside this range the efficiency must be derated according to the following figure.
Head: the height at which a pump can displace a liquid to. Head is also a form of energy. In pump systems there are 9 different types of head: elevation head or static head, pressure head, velocity head and friction head loss. For more information on head see this tutorial.
the above image is from the Cameron Hydraulic data book which contains a great deal of information on fluid properties. To purchase go to the Flow Serve web site.
Stress : In this case refers to tangential stress or the force between the layers of fluid divided by the surface area between them.
Bingham plastic : A fluid that behaves in a Newtonian fashion (. constant viscosity) but requires a certain level of stress to set it in motion.