
Fluid entering a centrifugal pump is
immediately directed to the low pressure area at the center
or eye of the impeller. As the
impeller and blading rotate, they transfer momentum to
incoming fluid. A
transfer of momentum to the moving fluid increases the fluids
velocity. As the fluids velocity
increases its kinetic energy increases. Fluid of high kinetic
energy is forced out of the impeller
area and enters the volute.
The volute is a region of continuously
increasing crosssectional area designed to convert the
kinetic energy of the fluid into
fluid pressure. The mechanism of this energy conversion is
the same as that for
subsonic flow through the diverging section of a nozzle. The
mathematical analysis of
flow through the volute is based on the general energy
equation, the continuity equation,
and the equation relating the internal properties of a
system. The key parameters influencing
the energy conversion are the expanding crosssectional area
of the volute, the higher system
back pressure at the discharge of the volute, and the
incompressible, subsonic flow of the fluid.
As a result of the interdependence of these parameters, the
fluid flow in the volute, similar to
subsonic flow in a diverging nozzle, experiences a velocity
decrease and a pressure increase.
