Dynamic thrust balancing for centrifugal compressors

Abstract

Systems and methods for dynamically balancing axial loads in centrifugal compressors to reduce residual axial loads on the bearings used therein are described. A sensor or probe detects a parameter associated with the axial load acting on the bearing. Based on the detected parameter, the pressure in a balance chamber is controlled to adjust the compensating axial force generated by a balance drum.

What is claimed is: 
     
         1 . A centrifugal compressor comprising:
 a rotor assembly including at least one impeller;   a bearing connected to, and for rotatably supporting, the rotor assembly;   a stator;   a balance drum disposed between said at least one impeller and said bearing;   a balance chamber, defined at least in part by an outboard side of said balance drum, and having a balance line connected thereto;   a sensor for sensing a parameter which is associated with an axial load on said bearing; and   a control valve for varying a pressure within said balance chamber based on said sensed parameter.   
     
     
         2 . The centrifugal compressor of  claim 1 , further comprising:
 control logic configured to receive an output of said sensor and to control said control valve according to a predetermined function.   
     
     
         3 . The centrifugal compressor of  claim 2 , wherein said predetermined function operates to increase pressure in said balance chamber when said axial load on said bearing exceeds a predetermined value. 
     
     
         4 . The centrifugal compressor of  claim 1 , wherein said bearing is an active magnetic bearing. 
     
     
         5 . The centrifugal compressor of  claim 1 , wherein said bearing is an oil-lubricated bearing. 
     
     
         6 . The centrifugal compressor of  claim 1 , wherein said sensed parameter is displacement of said bearing. 
     
     
         7 . The centrifugal compressor of  claim 1 , wherein said sensed parameter is axial load on said bearing. 
     
     
         8 . The centrifugal compressor of  claim 1 , wherein said sensor is an induction sensor. 
     
     
         9 . The centrifugal compressor of  claim 1 , wherein said sensor is a piezoelectric sensor. 
     
     
         10 . The centrifugal compressor of  claim 1 , wherein said sensor is an eddy current sensor. 
     
     
         11 . A method for dynamically balancing axial load acting on a bearing in a centrifugal compressor, the method comprising:
 detecting a parameter associated with said axial load; and   controlling a pressure in a balance chamber proximate a balance drum in said centrifugal compressor based on said detected parameter to dynamically balance said axial load acting on said bearing.   
     
     
         12 . The method of  claim 11 , wherein said step of controlling further comprises:
 opening or closing a valve connected to a balance line which controls said pressure in said balance chamber.   
     
     
         13 . The method of  claim 11 , wherein said step of controlling operates to increase pressure in said balance chamber when said axial load on said bearing exceeds a predetermined value. 
     
     
         14 . The method of  claim 11 , wherein said bearing is an active magnetic bearing. 
     
     
         15 . The method of  claim 11 , wherein said bearing is an oil-lubricated bearing.