Impeller (flow machine)
An impeller is a moving ( rotating ) part of a fluid flow machine (e.g. turbine , centrifugal pump , turbo compressor ) that either extracts or adds work to the flowing fluid . The counterpart to the moving impeller is the stationary stator or tail unit , which directs the flow to the impeller. A stator and an impeller together form a "stage". In a multi-stage machine, several guide and runner wheels are alternately connected in series (see picture).
The sum of all wheels with the connecting shaft is rotor or rotor mentioned. Simple, free-standing impellers, especially in water turbines, drives for ships or aircraft, are sometimes also called screws or propellers .
construction
An impeller consisting of a ring of blades ( vanes , rotor blades, ...), which are held by a suitable fastening on the shaft.
The frictional connection must be given both to transmit the torque to the shaft and to compensate for the centrifugal force , which can be considerable in large and fast-rotating machines. (In the case of the end blades of large steam turbines, this centrifugal force can be several hundred tons for a single blade.) Here material -locking connections ( cast from one piece or welding) or form-locking connections ( dovetail , Christmas tree ...) can be selected, the latter having the advantage that they are solvable.
If necessary, the blades can be connected to one another by a " shroud " on the outside for stabilization against vibrations and for axial sealing .
history
The American Samuel B. Howd , who relocated the impeller inside the tail unit in 1838 , and the Englishman James Thomson , who introduced adjustable guide vanes and curved impeller blades , invented major changes in the development of turbine runners .