Active Rotor Alignment Control System And Method

Abstract

A rotating machine, such as a gas turbine, includes an active rotor alignment clearance control system wherein a plurality of actuators are circumferentially spaced around at least one rotor shaft bearing. The actuators are configured to eccentrically displace the bearing, and thus the rotor shaft, relative to stationary outer casing structure. A plurality of sensors are circumferentially spaced around a component of the casing structure, such as an inner shroud, and measure a parameter indicative of an eccentricity, such as blade tip clearance between the rotor blades and the structure, as the rotor rotates within the structure. A control system in communication with the sensors and actuators is configured to control the actuators to eccentrically displace the rotor by moving the shaft bearing to compensate for eccentricities detected between the rotor and casing structure.

Description

FIELD OF THE INVENTION[0001]The present invention relates generally to rotating machines, such as gas turbines, and more particularly to a system and method for measuring and controlling clearance between the rotor and a surrounding casing structure.BACKGROUND OF THE INVENTION[0002]Rotating machines such as gas turbines have portions commonly referred to as rotors that rotate within stationary casing components, such as a shroud. Clearance dimensions must be maintained between the rotor and the shroud to prevent impacts between the components. This is a particular concern in gas turbines.[0003]A gas turbine uses hot gases emitted from a combustion chamber to rotate a rotor, which typically includes a plurality of rotor blades circumferentially spaced around a shaft. The rotor shaft is coupled to a compressor for supplying compressed air to the combustion chamber and, in some embodiments, to an electric generator for converting the mechanical energy of the rotor to electrical energy....

AI Technical Summary

Benefits of technology

[0008]The present invention provides an active alignment control system and methodology that address certain of the shortcomings of prior control systems. Additional aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

Problems solved by technology

On the other hand, if the amount of clearance is too small, then thermal expansion and contraction of the blades, the shroud, and other components may cause the blades to rub the shroud, which can result in damage to the blades, the shroud ring, and the turbine in general.

The conventional passive air-cooling systems, however, assume a uniform circumferential expansion of the rotor and / or shroud and cannot account for eccentricities that either develop or are inherent between the rotor and shroud.

Anticipated eccentricities must be accounted for in design and, thus, these eccentricities limit the amount of minimum designed clearance that can be achieved without rubbing between the blades and shrouds.

This method, however, cannot accurately account for the variations in eccentricities that develop during the operational life of the turbine.

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