Patent Publication Number: US-2009226306-A1

Title: Apparatus and method for adjusting a bearing array in a gas turbine aircraft engine

Description:
This application claims the priority of International Application No. PCT/DE2006/000209, filed Feb. 8, 2006, and German Patent Document No. 10 2005 007 776.5, filed Feb. 19, 2005, the disclosures of which are expressly incorporated by reference herein. 
    
    
     BACKGROUND AND SUMMARY OF THE INVENTION 
     The invention relates to a bearing array, specifically for a gas turbine aircraft engine. 
     In gas turbine engines rotors, rotating rotor blades for example, are carried rotatably opposite a stator, for example a fixed housing and similarly fixed guide vanes. Bearing arrays for carrying the rotor opposite the stator have a stator-side, or fixed, bearing ring and a rotor-side, or rotatable, bearing ring, where roller elements are positioned between the stator-side bearing ring and the rotor-side bearing ring. Hydraulic damping elements, known as squeeze-film dampers, are usually located on the stator-side bearing ring which damp the vibrations of the rotor. Such squeeze-film dampers allow a radial displacement of the bearings on the order of up to 0.2 mm. 
     To optimize the efficiency of gas turbine aircraft engines, gaps between the rotor and the stator must be minimized. The gaps in question are, for example, gaps between a hub of the rotor and radially inward lying ends of fixed guide vanes and gaps between radially outward lying ends of the rotor blades and a fixed housing. To maintain these gaps precisely and thus optimize the efficiency of the gas turbine aircraft engine, one of the necessary considerations is exact positioning of the rotor relative to the stator. When a gas turbine aircraft engine is operating, forces or moments affect the bearing arrays, for example as the result of maneuvering loads. As the result of maneuvering loads, operating forces or moments, primarily the housings are deformed, which results in worse gap characteristics. Maneuvering loads further cause undesirable bearing displacement in the case of bearings damped using squeeze-film dampers. This makes it more difficult to position the rotor precisely relative to the stator and to maintain an exact gap between the stator and the rotor. 
     With this as the starting point, the problem underlying the present invention is create a new type of bearing array. 
     In accordance with the invention, transducers are allocated to the stator-side bearing ring on the one hand to determine the position of the stator-side bearing ring, and actuators on the other hand to govern the position of the stator-side bearing ring. 
     In the meaning of the present invention, it is provided to allocate several transducers and several actuators to the stator-side, or fixed, bearing ring. With the aid of the transducers, the position of the fixed bearing ring can be determined, with the actuators it is possible to govern the position of the stator-side, or fixed, bearing ring. Undesirable displacement of the bearings using squeeze-film dampers which results during operation as the result of maneuvering loads, for example, can be equalized or compensated for. 
     Preferably at least three measuring and actuating elements are allocated to the stator-side bearing ring, distributed equidistant around the circumference of the stator-side bearing ring, where each of the measuring and actuating elements has a transducer for determining the position of the stator-side bearing ring and an actuator to govern the position of the stator-side bearing ring. The stator-side bearing ring can be adjusted with the help of the actuators of the measuring and actuating elements in two directions, each running perpendicular to a rotational axis of the rotor-side bearing ring. 
     The sensors and actuators also assume the task of damping the bearing, or compensating for a residual imbalance in the rotor by “tracking” the bearing about the axis of inertia of the rotor. 
     Preferred further developments of the invention emerge from the description following. One embodiment of the invention, without being restricted thereto, is explained more closely using the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a section from a gas turbine aircraft engine in the area of a bearing array in accordance with the invention; and 
         FIG. 2  shows a detail of the bearing array from  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Hereinafter the invention is explained in greater detail with reference to  FIGS. 1 and 2 . 
       FIG. 1  shows a section from a gas turbine aircraft engine in the area of a bearing array  10  in accordance with the invention. The bearing array in accordance with the invention  10  comprises a stator-side, fixed bearing ring  11  and a rotor-side, rotating bearing ring  12 . The stator-side, fixed bearing ring  11  is configured as an outer bearing ring and the rotor-side rotating bearing ring  12  is configured as an inner bearing ring. Several roller elements  13  are located between the outer bearing ring  11  and the inner bearing ring  12 . 
     As can be seen from  FIG. 1 , the rotor-side, rotating inner bearing ring  12  is connected by a flange  14  to a rotor disk  15  of rotating rotor blades and a similarly rotating seal carrier  16 . In accordance with  FIG. 1 , the connection between the rotor-side inner bearing ring  12  and the seal carrier  16  and the rotor disk  15  is made by a threaded connector  17 . The stator-side, fixed outer bearing ring  11  is connected by way of what is known as a circumferential lock plate to a fixed part of the housing  19 . The relative position of the bearing array in the circumferential direction is fixed through the circumferential lock plate  18 . 
     In the meaning of the present invention, several measuring and actuating elements  20  are assigned to the stator-side, fixed outer bearing ring  11 . At least three measuring and actuating elements  20  are assigned to the fixed outer bearing ring  11 , which are distributed equidistant around the circumference of the fixed outer bearing ring  11 . Each of the measuring and actuating elements  20  has a transducer, not shown, and an actuator  21 . With the aid of the transducer, the position of the fixed outer bearing ring  11  can be determined relative to a set position. The transducers transmit corresponding actual values for the position of the outer bearing ring  11  to a control or feedback device, not shown, where the control or feedback device compares the actual values provided by the transducers for the relative position between the fixed outer bearing ring  11  and the set position with specified setpoints and, as a function thereof, generates positioning signals for the actuators  21 . With the aid of the actuators  21 , on the basis of the positioning signals generated by the control or feedback device, not shown, the position of the stator-side outer bearing ring  11 , or the entire bearing array  10 , can be adjusted, specifically in two directions which are both perpendicular to a rotational axis of the rotor, or rotor-side inner bearing ring  12 . The actuators  21  act in consequence in a radial direction on the fixed bearing ring  11 , where the circumferential lock plate  18  allows the bearing array  10  to be shifted in the radial direction. 
     As can be seen in particular from  FIG. 2 , the actuators  21  engage the measuring and actuating elements  20  in recesses  22  in the stator-side outer bearing ring  11 . The actuators  21  in each case are in contact with the outer bearing ring  11  through a crowned contact surface  23 . 
     The actuators are not a press fit in the housing  19  and the outer bearing ring  11 , the connection is established rather by controlling the actuators  21 . By comparing the signals from the transducers, or displacement sensors, and the control voltage of the particular actuator  21 , the point can be determined at which contact still exists at the particular crowned contact surface  23  with the outer bearing ring  11 . From a comparison of the actual values with the set values for the measuring and actuating elements  20 , the crowned contact surfaces  23  are always kept in contact with the outer bearing ring  11  through the controls. It is also possible to determine and regulate the corresponding contact forces. 
     The actuators  21  are in the meaning of the present invention preferably configured as piezo-ceramic actuators. The bearings can be configured as oil bearings, air bearings or magnetic bearings. The measuring and actuating elements  20  are connected to the stator-side part of the housing  19  by threaded connectors. 
     Using the bearing array in accordance with the invention, it is possible in a particularly simple way to compensate for displacement of the bearing array using squeeze-film dampers during operation of the gas turbine aircraft engine by means of an active control. The bearing array can be adjusted by means of actuators in two directions which run perpendicular to the rotational axis of the rotor. In addition, maneuvering loads acting on the gas turbine aircraft engine in particular can be compensated for in order to maintain precise gaps between the rotor and the stator. Vibrations or tumbling motions of the bearing array arising during operation can be compensated for or damped using the bearing array  10 , as the result of which loads acting on an engine suspension can be reduced.