multiimpeller

Multiimpeller is a term used to describe a pump, turbine, or other turbomachine that employs more than one impeller to transfer energy to a fluid. In pumping systems, multiimpeller configurations are most common in centrifugal machines in which several impellers are mounted on a single shaft either in series (staged) to develop higher head, or in parallel to increase flow capacity at a given head. In some designs, impellers are arranged in cascaded stages with interstage components to control pressure and flow.

In a staged centrifugal pump, each impeller adds head to the circulating fluid; the total head is approximately the sum of the individual stage heads. The presence of multiple wheels on one shaft also introduces axial thrust that must be balanced by proper bearing arrangements and, if needed, thrust rings or balance discs. Fluid flow between stages must be controlled to minimize recirculation and vibration.

Advantages of multiimpeller configurations include higher discharge heads from a compact package, modularity to tailor performance by adding or removing stages, and potential redundancy in certain designs. Disadvantages include increased mechanical complexity, higher manufacturing and maintenance costs, greater sensitivity to flow rate and clearance, and more demanding alignment and balancing requirements.

Typical applications include boiler feedwater pumps, high-head water supply and irrigation pumps, chemical processing and refinery services, and other industries requiring large head at moderate flows. See also multi-stage pump, staged turbine.