Diffuser or Turbine Centrifugal Pumps
This form of centrifugal pumps employs a system of stationary diffusion vanes which surround the impeller. Gradually enlarging areas are provided between the diffusers and in these passageways the velocity of the liquid leaving the tips of the 
rotor bladed is decreased and most of its velocity head transformed into pressure head. The velocity pressure conversion does not take place in the casing scroll alone as in the volute form of pump. Diffuser construction may be employed in pumps of two or more stages.
Other infomation on pumps:
Types of Centrifugal pumps, Volute pump, Turbine pumps, axial units, Rotary pumps.
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