Patent Abstract:
A balancing system and method for reducing imbalance in a rotatable member of a machine is provided. The system includes a plurality of vibration sensors positioned about a stationary portion of the machine, a controller assembly communitively coupled to the plurality of vibration sensors, and a balancing assembly coupled to the rotatable member, said balancing assembly configured to wirelessly communicate with said controller assembly, said balancing assembly configured to modify the weight distribution of the rotatable member in response to a command wirelessly transmitted from the controller assembly. The controller assembly is configured to receive data from the plurality of vibration sensors and determine an imbalance in the rotatable member using the received data.

Full Description:
BACKGROUND OF THE INVENTION 
       [0001]    The field of the invention relates generally to rotary blade systems, and more specifically, to methods and system for wirelessly balancing rotor assemblies. 
         [0002]    Known gas turbine engines include rotor assemblies that are rotatable relative to stationary engine structures. Known rotor assemblies include a number of rotatable components including a central shaft, shaft cones, compressor blades and disks, turbine buckets and wheels, and/or dynamic air seals. Each component is acted upon by static and/or dynamic axial pressure forces. Rotor imbalance may be a common source of vibration in known rotor assemblies. An imbalance in rotary machinery may be evident if the mass axis of a rotating disk or shaft does not substantially coincide with the axis of rotation. In such operating conditions, the rotating shaft or disk rotates about its axis and generates a centrifugal force that is substantially distributed to the bearings and support structure. The centrifugal force may induce a vibrational frequency to the non-rotating structure that is synchronous with rotor speed. The resulting dynamic response of the rotor/stator system may cause amplitudes of motion or may lead to failure of the rotor, bearings, and/or the support structure. 
         [0003]    To reduce the effects of imbalances, at least some known turbofan engines are manually balanced. In such a process, the fan is balances by coupling weights in the fan spinner or an adjacent rotating structure in an attempt to counter the rotor imbalance and to reduce the forced response of the system to acceptable levels. Vibration measurements are taken and used to calculate the distribution (amplitude and phase) of the corrective weights to be installed. The engine is then stopped and the appropriate weight(s) are added to the appropriate rotor assembly component. The engine is then cycled over its full rotor operating range to determine if the corrective weights reduced the vibration levels to acceptable levels. If the vibration levels are not acceptable, the process is repeated until acceptable vibration levels are achieved. Such a balancing procedure may be a time-consuming process that may require cycling the engine through its full rotor operating range several times. Additionally, balancing the fan assembly in this manner requires experienced technicians, expends significant quantities of fuel, and may result in an increase of environmentally undesirable emissions based on the increased engine running time. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    In one aspect, a balancing system for reducing imbalance in a rotatable member of a machine is provided. The system includes a plurality of vibration sensors positioned about a stationary portion of the machine, a controller assembly communitively coupled to the plurality of vibration sensors, and a balancing assembly coupled to the rotatable member, said balancing assembly configured to wirelessly communicate with said controller assembly, said balancing assembly configured to modify the weight distribution of the rotatable member in response to a command wirelessly transmitted from the controller assembly. The controller assembly is configured to receive data from the plurality of vibration sensors and determine an imbalance in the rotatable member using the received data. 
         [0005]    In another aspect, a method for balancing a rotor in a gas turbine engine is provided. The method includes coupling a balancing assembly to the rotor, measuring an imbalance of the rotor, determining a force vector that facilitates reducing the determined imbalance, transmitting, wirelessly, a movement command to the balancing assembly, modifying a weight distribution of the balancing assembly using the movement command, and iteratively performing the aforementioned steps until the imbalance is facilitated being minimized. 
         [0006]    In yet another aspect, a balancing assembly rotatably coupled to a gas turbine engine rotor is provided. The assembly includes a first balancing member, a second balancing member, wherein the first balancing member is positioned radially outward from the second balancing member, and at least one bearing configured to support an associated one of said first and second balancing members. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a cross-sectional view of an exemplary turbofan engine assembly including a balancing assembly. 
           [0008]      FIG. 2  is an exemplary cross-sectional schematic view of an exemplary balancing assembly used with the turbofan engine assembly shown in  FIG. 1 . 
           [0009]      FIG. 3  is a cross-sectional schematic view of a portion of balancing assembly shown in  FIG. 2 . 
           [0010]      FIG. 4  is a cross-sectional end view of the balancing assembly shown in  FIG. 3  and taken along line  4 - 4 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0011]      FIG. 1  illustrates an exemplary gas turbine engine  10  having a longitudinal axis  11 . Engine  10  includes a fan assembly  12 , a core gas turbine engine section  14  coupled downstream from fan assembly  12 , and a low-pressure turbine  16  coupled downstream from the core gas turbine engine section  14 . In the exemplary embodiment, core gas turbine engine section  14  includes a multi-stage booster compressor  17 , a high-pressure compressor  18 , a combustor  20 , and a high-pressure turbine  22 . Fan assembly  12  includes a plurality of fan blades  23  that extend radially outward from a rotor disk  24 , a fan shroud  26 , a fan spinner  28 , and a plurality of circumferentially spaced outlet guide vanes  30  that support fan shroud  26 . Fan spinner  28  is coupled to a spinner support bracket  31 . Engine  10  also includes an inlet  32  and an exhaust  34 . In the exemplary embodiment, low-pressure turbine  16  and booster compressor  17  are coupled together via a first drive shaft  36 , and compressor  18  and high-pressure turbine  22  are coupled together via a second drive shaft  38 . 
         [0012]    In operation, air is drawn into engine inlet  32 , and compressed through booster compressor  17  and high pressure compressor  18 . Compressed air is channeled to combustor  20  wherein it is mixed with fuel and ignited to produce air flow through high pressure turbine  22  and low pressure turbine  16 , and exits through exhaust  34 . 
         [0013]      FIG. 2  is an enlarged cross-sectional schematic view of an a balancing system  50  used with engine  10 . In the exemplary embodiment, balancing system  50  includes a balancing assembly  100  that is removably coupled within engine  10  by at least two support members  102 . More specifically, in the exemplary embodiment, support members  102  are coupled at a first end  103  to a balancing assembly flange  104  and at a second end  108  between fan spinner  28  and spinner support bracket  31 . Support members  102  may be coupled to assembly  100  by any coupling method, for example, by welding, or any other method that enables assembly  100  to function as described herein. In another embodiment, balancing assembly  100  may be integrally formed with, or permanently coupled, to fan spinner  28  such that fan spinner  28  and balancing assembly  100  may be removed and/or installed within engine  10  as a single unit. 
         [0014]    In the exemplary embodiment, balancing assembly  100  includes two rotatable balancing members  110  and  112 . Balancing member  110  is rotated by a first motor  114  and balancing member  112  is rotated by a second motor  116 . Both balancing members  110  and  112  are oriented substantially concentrically along a central rotor  118  having a center axis  119 . Balancing assembly  100  also includes an internal control assembly  120 . Control assembly  120 , balancing members  110  and  112 , and motors  114  and  116  are housed a housing  122 . In the exemplary embodiment, motors  114  and  116  are stepper motors. Alternatively, motors  114  and  116  may be any power source that enables balancing assembly  100  to function as described herein. Additionally, internal control assembly  120  includes a receiver  124 , a processor  126 , a power source  128 , and an antenna  129 . During use, and as described in more detail below, control assembly  120  regulates balancing assembly  100 . 
         [0015]    Additionally, balancing system  50  also includes a controller assembly  200  that includes a processor  202 , a transceiver  204  and an antenna  206 . In the exemplary embodiment, controller assembly  200  is coupled in wireless communication with a plurality of vibration sensors  210  (shown in  FIG. 1 ) coupled within engine  10 . Controller assembly  200  is also coupled in wireless communication with balancing assembly internal control assembly  120 . In operation, controller assembly  200  issues commands balancing assembly internal control assembly  120  to facilitate rotating balancing members  110  and  112  in the calculation of a balancing solution described in more detail below. In the exemplary embodiment, controller assembly  200  and internal control assembly  120  form a closed loop system, such that upon a command being sent from controller assembly  200  to internal control assembly  120 , internal control assembly  120  transmits a position response back to controller assembly  200 . In the alternative embodiment, controller assembly  200  and internal control assembly  120  form an open loop system, such that controller assembly relies solely on input from vibration sensors  210  positioned about engine  10  and transmits commands to internal control assembly  120  in an iterative fashion. 
         [0016]      FIG. 3  is a cross-sectional view of balancing assembly  100  and illustrates the orientation of balancing members  110  and  112 . In the exemplary embodiment, balancing members  110  and  112  are substantially concentrically aligned and each has a radially eccentric weight distribution, as described below. Members  110  and  112  are oriented such that balancing member  110  is radially outward from balancing member  112  when assembly  100  is coupled within engine  10 . A plurality of bearing assemblies  130  and  132  provide support and stability to members  110  and  112 , respectfully. In the exemplary embodiment, bearing assemblies  130  and  132  also provide radial support to balancing assembly  100 . An internal support  134  extends substantially perpendicularly inward from assembly housing  122  (shown in  FIG. 2 ) to facilitate providing additional axial and radial support to assembly  100 . Moreover, in the exemplary embodiment, members  110  and  112  and bearing assemblies  130  and  132  are oriented in the same axial plane such that bearing assembly  130  provides rotational support between internal support  134  and balancing member  112 , and such that bearing assembly  132  provides rotational support between balancing member  110  and balancing member  112 . Alternatively, members  110  and  112  and bearing assemblies  130  and  132  may be oriented in any configuration that enables balancing assembly  100  to function as described herein. 
         [0017]      FIG. 4  illustrates a cross-sectional end view of balancing assembly  100 . In the exemplary embodiment, balancing member  110  has an eccentrically offset center of mass  140 . Similarly, balancing member  112  has an eccentrically offset center of mass  142 . Each member  110  and  112  is rotatably coupled about rotor  118  and center axis  119  such that members  110  and  112  can rotate in a clockwise direction  144  or a counter-clockwise direction  146 . Alternatively, balancing members  110  and  112  and bearing assemblies  130  and  132  may be coupled within balancing assembly  100  in any configuration that enables system  50  to function as described herein. 
         [0018]    During engine operation, system  50  uses wireless communications to automatically determine a balance solution for engine  10 . Balancing assembly  100  is coupled to rotor  118  as described herein, and vibration sensors  210  are positioned about engine  10 . In the exemplary embodiment, sensors  210  include accelerometers, and a key phasor (not shown) used to determine a rotational position of fan assembly  12 . The key phasor is used to establish a phase reference relative to fan spinner  28  and to calibrate the signals from vibration sensors  210 . 
         [0019]      FIGS. 5 and 6  illustrate a cross-sectional end view of balancing assembly  300  and illustrate exemplary force vectors associated with balancing assembly  300 . Balancing assembly  300  is substantially similar to balancing assembly  100  (shown in  FIGS. 1-4 ) and components in balancing assembly  300  that are identical to components of balancing assembly  100  are identified in  FIGS. 5  and  6  using the same reference numerals used in  FIGS. 1-5 . Accordingly, balancing assembly  300  includes balancing members  110  and  112  and respective centers of mass  140  and  142  oriented about a center axis  119 . 
         [0020]    In the exemplary embodiment, centers of mass  140  and  142  of each respective balancing member  110  and  112  are oriented 180° apart at the beginning of the balancing process. Alternatively, centers of mass  140  and  142  of each respective balancing member  110  and  112  may be positioned at any angular location that enables balancing assembly  300  to function as described herein. Balancing assembly  300  has an exemplary force vector  305 , and each balancing member  110  and  112  has a force vector  310  and  320 , respectively. As shown in  FIG. 5 , in the exemplary embodiment, an exemplary resultant force vector  330  is determined via known vector summation  340  for balancing assembly  300 . 
         [0021]    Vibration signals sent to the controller assembly  200  are digitally filtered by processor  202  to obtain the rotor-speed frequency. Upon sensing vibration, vibration sensors  210  wirelessly transmit a signal to controller assembly  200 , which is received by transceiver  204  located therein. Controller assembly processor  202  generates a command signal based on vibration data received from sensors  210 , and transmits the command signal to balancing assembly receiver  124 . Activation of motors  114  and  116  is controlled by commands from controller assembly  200 . 
         [0022]      FIG. 6  illustrates a cross-sectional end view of balancing assembly  300  and illustrates exemplary force vectors associated with balancing assembly  300  following a balancing iteration. More specifically and in the exemplary embodiment, motors  114  and  116  rotate balancing members  110  and  112  to cause the center of mass  140  and/or  142  of each respective balancing member  110  and  112  to be oriented at a determined angle with respect to fan spinner&#39;s  28  rotational speed. Balancing members  110  and  112  are adjusted to facilitate reducing force vector  305 . Resultant force vector  330  is again determined via known vector summation  340  for balancing assembly  300  following the exemplary balancing process iteration. 
         [0023]    In the exemplary embodiment, the controller assembly  200  uses a least-squares method algorithm for computing a balance solution. To calculate the balance solution the algorithm uses plain least squares to facilitate minimizing residual vibration levels at the vibration sensors, and then iterates, using weighted least squares, to facilitate reducing the maximum residual vibration in light of the vibration response from multiple sensors over a range of operating rotor speeds. Alternatively, the balance solution may be calculated by any method that enables balancing assembly  300  to function as described herein. 
         [0024]    In the exemplary embodiment, following an iteration that produces an acceptable vibration level, the controller assembly processor  202  outputs a final balance solution that includes a quantity of balancing weight to be installed and a relative angular position for the installation of the balancing weight relative to the fan spinner, or any rotating engine structure that facilitates reducing the vibration level. At this time, balancing assembly is removed from engine  10  and the appropriate balancing weight is positioned within engine  10  at the determined relative angular position. 
         [0025]    The above-described systems and methods facilitate automatic balancing of rotor blades in a gas turbine engine using an autobalancer that provides an automated means to quickly determine the balance solution for the fan without user intervention and without having to stop and start the engine for multiple vibration measurement and balance shot iterations. Furthermore, this automatic balancing system provides an opportunity to achieve significant fuel and labor cost savings and to significantly reduce CO 2  emissions based on decreased engine running time. As a result, the above-mentioned balancing system facilitates providing 
         [0026]    Although the systems and methods described herein are described in the context of a balancing assembly for gas turbine engine rotors, it is understood that the systems and methods are not limited to such balancing assemblies. Likewise, the system components illustrated are not limited to the specific embodiments described herein, but rather, system components can be utilized independently and separately from other components described herein. 
         [0027]    As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural said elements or steps, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
         [0028]    While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.

Technology Classification (CPC): 6