Rotor thrust balancing apparatus and method

Abstract

Apparatus and method of balancing thrust bearing load on a rotor thrust bearing employ a first thrust balance piston cavity for exerting an aft directed thrust balancing force and a second balance piston cavity for exerting an independently controlled forward directed thrust balancing force to allow flexible and wide range balancing of thrust load on the rotor thrust bearing.

1 . Rotor thrust balancing apparatus for a gas turbine engine having a rotor thrust bearing disposed between stationary stator components and rotatable rotor components comprising: 
 (a) a first thrust balance piston cavity for exerting an aft directed thrust balancing force on a first annular plate connected to high pressure drive shaft; and    (b) a second balance piston cavity for exerting an independently controlled forward directed thrust balancing force on a second annular plate connected to said high pressure drive shaft.    
   
   
       2 . The apparatus of  claim 1  wherein: 
 (a) said first balance piston cavity is connected in flow communication to a first air pressurized volume via a first seal and in flow communication with a first air pressure relief tube connected in flow communication with a first air flow control valve for controlling air pressure in said first balance piston cavity; and    (b) said second balance piston cavity is connected in flow communication to a second air pressurized volume via a second seal and in flow communication with a second air pressure relief tube connected in flow communication with a second air flow control valve controllable independently of said first air flow control valve for controlling air pressure in said second balance piston cavity.    
   
   
       3 . A gas turbine engine comprising: 
 a stator and a rotor including a high pressure compressor and a high pressure turbine connected by a high pressure drive shaft rotatable within and supported by said stator and a rotor thrust bearing disposed between said high pressure drive shaft and said stator;    a first thrust balance piston cavity disposed aft of said rotor thrust bearing and comprising a closed volume defined at its axially aft end by rotatable member connected to said high pressure drive shaft and defined at its axially forward end by stationary surface connected to said stator and connected in air flow communication with high pressure compressor discharge air pressurized volume through a seal and connected in flow communication with an air pressure relief tube and via a first air flow control valve to a first air exhaust tube;    second balance piston cavity disposed forward of said rotor thrust bearing and comprising a closed volume defined at its axially forward end by an annular plate connected to high pressure drive shaft and defined at its axially aft end by an annular plate connected to the stator and connected in air flow communication with a second high pressure compressor discharge air pressurized volume through a second seal and in flow communication with a second air pressure relief tube and via second air flow control valve to a second air exhaust tube.    
   
   
       4 . A method for balancing rotor thrust bearing loads in a gas turbine engine comprising: 
 controlling air pressure in a first balance piston cavity configured to provide an aft directed thrust balancing force to an engine rotor component; and    independently controlling air pressure in a second balance piston cavity configured to provide a forward directed thrust balancing force.    
   
   
       5 . The method of  claim 4 , wherein: 
 controlling air pressure in said first balance piston cavity comprises controlling a first air flow control valve contained within a first air exhaust tube connected in flow communication with said first balance piston cavity to control air flow from said first balance piston cavity to control the force of said aft directed thrust balancing force; and;    controlling air pressure in said second balance piston cavity comprises controlling a second air flow control valve contained within a second air exhaust tube connected in flow communication with said second balance piston cavity to control air flow from said second balance piston cavity to control the force of said forward directed thrust balancing force.    
   
   
       6 . The method of  claim 5 , wherein: 
 controlling air pressure in said first balance piston cavity comprises adjusting said first air flow control valve to increase air flow from said first balance piston cavity to allow air pressure within said first balance piston cavity to drop to reduce the force of the aft directed thrust balancing force; and    controlling air pressure in said second balance piston cavity comprises maintaining said second air flow control valve unchanged to maintain air pressure within said second air flow control valve fixed to maintain said forward directed thrust balancing force constant to produce a net increase in thrust balance force in the axially upstream direction.    
   
   
       7 . The method of  claim 5 , wherein: 
 controlling air pressure in said first balance piston cavity comprises adjusting said first air flow control valve to increase air flow from said first balance piston cavity to allow air pressure within said first balance piston cavity to drop to reduce the force of the aft directed thrust balancing force; and    controlling air pressure in said second balance piston cavity comprises adjusting said second air flow control valve to lower air flow from said second balance piston cavity to raise air pressure within said second air flow control valve fixed to increase the force of said forward directed thrust balancing force to produce a net increase in thrust balance force in the axially upstream direction.    
   
   
       8 . The method of  claim 5 , wherein: 
 controlling air pressure in said first balance piston cavity comprises adjusting said first air flow control valve to maximize air flow from said first balance piston cavity to minimize air pressure within said first balance piston cavity to drop to minimum level to minimize the force of the aft directed thrust balancing force; and    controlling air pressure in said second balance piston cavity comprises adjusting said second air flow control valve to minimize air flow from said second balance piston cavity to maximize air pressure within said second balance piston cavity to maximize said forward directed thrust balancing force constant to produce a maximum net forward directed thrust balancing force.    
   
   
       9 . The method of  claim 5 , wherein: 
 controlling air pressure in said second balance piston cavity comprises adjusting said second air flow control valve to maximize air flow from said second balance piston cavity to minimize air pressure within said second balance piston cavity to minimize air pressure within said second balance piston cavity to minimize the force of the forward directed thrust balancing force; and    controlling air pressure in said first balance piston cavity comprises adjusting said first air flow control valve to minimize air flow from said first balance piston cavity to maximize air pressure within said first balance piston cavity to maximize air pressure within said first balance piston cavity to maximize said aft directed thrust balancing force to produce a maximum net aft directed thrust balancing force.