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.

1 . A gas turbine with a clearance control system, comprising:
 a rotor with at least one stage of rotor blades rotationally supported within a casing structure;   said rotor comprising opposite shaft ends, with each said shaft end supported by a respective shaft bearing;   a plurality of actuators configured with at least one of said shaft bearings to move said shaft bearing and thereby eccentrically displace said rotor relative to said casing structure;   a plurality of sensors circumferentially spaced around said casing structure and configured to measure a parameter indicative of an eccentricity between said rotor and said casing structure as said rotor rotates within said casing structure; and   a control system in communication with said plurality of sensors and said plurality of actuators and configured to control said plurality of actuators to displace said shaft bearing relative to said casing structure to compensate for eccentricities detected between said rotor and said casing structure by said plurality of sensors.   
     
     
         2 . The gas turbine as in  claim 1 , further comprising an additional plurality of actuators configured with the other respective said shaft bearing, said additional plurality of actuators in communication with said control system such that said rotor is displaced relative to said casing structure by movement of one or both of said shaft bearings. 
     
     
         3 . The gas turbine as in  claim 1 , comprising at least four said actuators spaced 90 degrees apart around said shaft bearing. 
     
     
         4 . The gas turbine as in  claim 1 , wherein said plurality of actuators are any combination of pneumatic, mechanical, electrical, thermal, or hydraulic mechanisms. 
     
     
         5 . The gas turbine as in  claim 1 , wherein said control system comprises a closed-loop feedback system. 
     
     
         6 . The gas turbine as in  claim 5 , wherein said control system comprises software implemented programs that calculate a magnitude and rotational position of a rotor eccentricity from signals received from said plurality of sensors, and control said plurality of actuators to compensate for the calculated rotor eccentricity as the rotor rotates within said casing structure. 
     
     
         7 . The gas turbine as in  claim 1 , wherein said plurality of sensors are active clearance sensors circumferentially spaced around said shroud that transmit and receive a signal reflected from said rotor blades to measure tip clearance between said rotor blades and said shroud. 
     
     
         8 . The gas turbine as in  claim 1 , wherein said plurality of sensors are passive clearance sensors circumferentially spaced around said casing structure to measure tip clearance between said rotor blades and said shroud. 
     
     
         9 . The gas turbine as in  claim 1 , wherein said plurality of actuators support said shaft bearing relative to said casing structure. 
     
     
         10 . A method for clearance control between a rotor and casing structure in a machine wherein a rotor rotates within the casing structure, said method comprising:
 detecting eccentricities between the rotor and casing structure by sensing a parameter indicative of an eccentricity as the rotor rotates within the casing structure; and   in response to any detected eccentricities, eccentrically displacing the rotor relative to the casing structure to compensate for the detected eccentricity as the rotor rotates within the casing structure.   
     
     
         10 . The method as in  claim 9 , comprising sensing clearance between the rotor and casing structure at a plurality of locations around the casing structure, and calculating a magnitude and relative rotational position of the eccentricity so as to continuously compensate for the eccentricity as the rotor rotates within the casing structure. 
     
     
         11 . The method as in  claim 9 , comprising actively sensing clearance between the rotor and casing structure with active sensors circumferentially spaced around the casing structure. 
     
     
         12 . The method as in  claim 9 , comprising passively sensing clearance between the rotor and casing structure with passive sensors circumferentially spaced around the casing structure. 
     
     
         13 . The method as in  claim 9 , wherein the rotor is rotationally supported relative to the casing structure by respective shaft bearings at opposite ends of the rotor, and comprising eccentrically displacing the rotor relative to casing structure by controlling a plurality of actuators configured between at least one of the shaft bearing and the casing structure. 
     
     
         14 . The method as in  claim 13 , comprising sensing clearance between the rotor and casing structure at a plurality of locations around the casing structure, calculating a magnitude and relative rotational position of the eccentricity, and in a closed-loop feed back system continuously controlling the actuators to displace the shaft bearing so as to compensate for the eccentricity as the rotor rotates within the casing structure. 
     
     
         15 . A rotor to casing alignment system, comprising:
 a rotor rotationally supported within a casing structure;   said rotor comprising opposite shaft ends, with each said shaft end supported by a respective shaft bearing;   a plurality of actuators configured with at least one of said shaft bearings to move said shaft bearing and thereby eccentrically displace said rotor relative to said casing structure;   a plurality of sensors circumferentially spaced around said casing structure and configured to detect an eccentricity between said rotor and said casing structure as said rotor rotates within said casing structure; and   a control system in communication with said plurality of sensors and said plurality of actuators and configured to control said plurality of actuators to displace said rotor relative to said casing structure by moving said shaft bearing to compensate for eccentricities detected between said rotor and said casing structure by said plurality of sensors.   
     
     
         16 . The system as in  claim 15 , further comprising an additional plurality of actuators configured with the other respective said shaft bearing, said additional plurality of actuators in communication with said control system such that said rotor is displaced relative to said casing structure by movement of one or both of said shaft bearings. 
     
     
         17 . The system as in  claim 15 , wherein said plurality of actuators are any combination of pneumatic, mechanical, or hydraulic mechanisms. 
     
     
         18 . The system as in  claim 15 , wherein said control system comprises a closed-loop feedback system with software implemented programs that calculate a magnitude and rotational position of a rotor eccentricity from signals received from said plurality of sensors, and controls said plurality of actuators to compensate for the calculated rotor eccentricity as the rotor rotates within said casing structure. 
     
     
         19 . The system as in  claim 15 , wherein said plurality of sensors comprise any combination of active or passive sensors circumferentially spaced around said casing structure to measure clearance between said rotor and said casing structure. 
     
     
         20 . The system as in  claim 15 , wherein said plurality of actuators support said shaft bearing relative to said casing structure.