Method and apparatus for reducing windage losses in rotating equipment

Abstract

A rotating flood cooled machine having reduced windage losses comprises a stator having an inner periphery and a rotor rotatably positioned within the stator separated from the stator by a gap which is filled with fluid. A film divider is rotatably positioned within this gap and is allowed to rotate freely. In such a machine, when the rotor rotates at a speed .omega., the film divider is caused to rotate at a speed of approximately .omega./2. At this speed, the film divider obtains a radial position during rotation of approximately midway between the outer periphery of the rotor and the inner periphery of the stator. This radial position is preferably maintained by the hydrodynamic bearing action of the fluid within the gap, or alternatively through the use of radial positioning or retaining mechanisms. The use of axial constraint mechanisms to maintain the film divider within the air gap under the shear forces of the fluid during operation is also contemplated. The film divider may also include a plurality of holes to facilitate a flow of fluid within the air gap. This flow may be further facilitated within and trough the air gap by dividing the film divider in two halves along a midline. A method of reducing the windage loss of a rotating flooded machine, such as, e.g., an electric motor or generator, comprises the steps of placing a film divider in the gap between the rotor and stator and allowing this divider to rotate freely therein during operation.