Method of positioning seals in turbomachinery utilizing electromagnetic bearings

Abstract

A method of positioning a shaft and an associated seal in turbomachinery utilizing electromagnetic bearings. The method comprises the steps of applying electrical power to the windings of the electromagnetic bearings in which the shaft center is in a first position and wherein the shaft is in contact with the associated seal. By adjusting the power to the electromagnetic bearings, the seal can be manipulated with the shaft by movement of the shaft in a series of moves of decreasing amplitude to a position in which the seal is out of contact with the shaft when the shaft is rotated at its centered position during normal operation of the turbomachinery. The shaft is in its centered position during normal operation when the shaft axis is substantially coaxial with an axis of the electromagnetic bearings. The series of movements of decreasing amplitude may include oscillations of decreasing amplitude about one or more axes, or may include rotation in a spiral with a radius of decreasing amplitude to move the center of the shaft from an initial position to a final position. Movement of the shaft is accomplished by adjusting the electrical power to the windings of the electromagnetic bearings.

Description

Background of the invention [0001] The methods and apparatus set forth in this specification relate generally to turbomachinery, such as compressors or turbines, having bearings utilizing active magnetic technology, and more particularly to improvements in sealing arrangements for turbine shafts. [0002] Active magnetic technology is currently used in some turbines in the form of electromagnetic bearings to float the rotor and shaft, replacing traditional technologies such as rolling element bearings or fluid film bearings. The position of the rotor is monitored by position sensors. Usually there are at least 4 position sensors equally spaced around the bore of the magnetic bearing. These sensors feed information to a controller which in turn adjusts the current supplied to the electromagnetic bearing to maintain the center of the shaft at a desired position or within a desired tolerance range. Typically, the bearing electronics try to keep the shaft equidistant from all se...

AI Technical Summary

Problems solved by technology

Materials must be selected to withstand this friction without excessive wear and heat, making the design more complex and expensive

Despite these design efforts, seals will eventually exhibit a certain amount of wear and performance degradation

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