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Published on Mar 18, 2013
An impeller is the rotating component of a centrifugal pump that accelerates the fluid inside the pump.
The velocity gained by the fluid is transformed later into pressure as the fluid leaves the pump.
The fluid enters the impeller through the eye, then it is pushed by the vanes or blades, and leaves the impeller through the holes.
The impeller has also a bore to attach the drive shaft.
The impeller is the pump component that has more influence on the pump performance. Actually, you can create a brand new pump by just modifying the impeller.
In this slide we can see different impeller designs. We notice each design has a different velocity triangle and thus, different performance curves.
Open, semi-open, enclosed The open impeller consists only of blades attached to a hub. It resembles a propeller. This impeller has low efficiency but it has to be used when it is necessary to clean the impeller and where there is risk of blocking.
The semi-open impeller has a circular plate attached to one side of the blades.
The enclosed impeller (also known as shrouded impeller) has one circular plate on each side.
Radial, axial and mixed flow Radial: high pressure and low flow Axial: the opposite Semiaxial impellers are used when a trade-off between pressure rise and flow is required.
Number of blades The channel of an impeller is the space between two blades.
The number of channels mainly depends on the desired performance and noise constraints as well as the amount and size of solid particles in the fluid.
Impellers with 5-10 channels have proven to give the best efficiency and are used for fluids without solid particles. One, two or three channel impellers are used for fluids with particles such as waste- water.