Method and apparatus for turbine engine rotor automatic self balancing

An online real time steam or gas turbine engine rotor balancing system is incorporated in a rotor balance plane. A selectively displaceable balancing weight is coupled to the rotor and is selectively displaced by a motor that is coupled to the balancing weight. The motor selectively displaces the balancing weight along a displacement path that is in the balance plane. A turbine engine rotor vibration monitoring system monitors rotor vibration in real-time. A control system is coupled to rotor vibration monitoring system and the motor, for determining in real time a desired balance weight displacement position to counteract the monitored rotor vibration. The controller selectively causes the motor to displace the balancing weight to the desired displacement position. The motor power source is an inductive power source or a permanent magnet generator.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to systems and methods for operational turbo machinery, such as steam or combustion gas turbine engines, vibration monitoring and automatic balancing of the rotor/shaft in response to the monitored vibration. More particularly the invention relates to motorized balancers coupled to shaft/rotor balancing rings that displace balancing weights to counteract the monitored vibration. The motors are controlled by a control system that determines in real time a desired balance weight displacement position to counteract the monitored vibration and causes the motor to displace the balancing weight to the desired displacement position.

2. Description of the Prior Art

Turbo-machinery shafts generally require rotational mechanical balancing to avoid vibration when they are at running speed.FIG. 1shows an exemplary known compressor and torque tube portion of a combustion turbine rotor20, comprising a rotor shaft22and balancing rings24. The turbine section portion of the known rotor is not shown. The balancing rings' locations are often referred to as “balance planes” that are perpendicular to the rotor's rotational axis. Threaded plugs26are inserted into threaded bores that are arrayed about the rotor at the plane. Other methods of installing balance weights such as capturing the weight in a toothed slot, or other methods may be used in some applications.

During initial fabrication of the rotor20prior to initial balancing rotor vibrations are monitored during a spinning procedure. For previously operational rotors during service refurbishment prior history of monitored rotor vibration is also often utilized. For either new or refurbished rotors, the monitored vibrations are used to determine a balance weight array pattern of weight and bore locations along the balance plane that will be expected to counteract the monitored vibration. In a so-called “balance move” service procedure, the rotor is brought to a standstill and the balancing weights are installed in accordance with the previously determined balance weight array pattern. The balance move procedure is repeated iteratively, if necessary, to establish rotor balance within functional specifications. Upon completion of the balancing procedure the balancing weight mass and positions remain static until the next rotor service outage.

During turbo-machine operation, such as combustion turbine engine operation, a rotor20can become out of balance due to disassembly and reassembly during maintenance, normal wear of seals and other components, engaging of clutches, or thermal expansion of the rotor. If the rotor20out of balance condition is not so severe as to require immediate turbine engine shut down, the engine may continue to be operated until the next scheduled maintenance outage, but nonetheless at a higher than desired vibration level. If vibration levels increase beyond acceptable specifications the turbine engine may have to be shut down for balancing maintenance ahead of the next scheduled outage, resulting in an unscheduled engine service disruption.

SUMMARY OF THE INVENTION

Accordingly, a suggested object of the invention is to perform automatic turbo machinery shaft balancing, such as automatic steam or combustion turbine rotor balancing, during machine/engine operation, in order to compensate for new imbalances developed during such operation or to tune vibration performance during such operation.

Another suggested object of the invention is to perform automatic turbo machinery shaft balancing, such as automatic steam or combustion turbine rotor balancing, after initial shaft/rotor fabrication or after service refurbishment, so as to reduce or eliminate the need to perform single or repetitive manual “balance moves” of static balancing weights at one or more of the balance planes, by inserting the balance weights into one of a ring of threaded holes, a weight inserted into a toothed slot in the rotor, or any other static method of attaching a balance weight to the rotor.

These and other objects are achieved, in one or more embodiments of the invention, by an online real time turbo-machinery steam or gas turbine engine rotor balancing system, which is incorporated in the rotor, such as in a balancing ring. A selectively displaceable balancing weight is coupled to the rotor at a balance plane and is selectively displaced by a motor that is coupled to the balancing weight . . . . The motor selectively displaces the balancing weight along a displacement path in the balance plane. A turbine engine rotor vibration monitoring system monitors rotor vibration in real-time. A control system is coupled to rotor vibration monitoring system and the motor, for determining, in real time, a desired balance weight displacement position to counteract the monitored rotor vibration. The controller selectively causes the motor to displace the balancing weight to the desired displacement position. In described exemplary embodiments of the invention the motor power source is an inductive power source or a permanent magnet generator or other known power source.

Embodiments of the invention feature an online real time rotor balancing system for steam or combustion gas turbine engines, which includes a rotor having a rotation axis and one or more balance planes. A selectively displaceable balancing weight is coupled to the rotor. A motor is coupled to the balancing weight for selectively displacing the balancing weight along a displacement path in the balance plane. A turbine engine rotor vibration monitoring system monitors rotor vibration in real-time. A control system coupled to rotor vibration monitoring system and the motor determines, in real time, a desired balance weight displacement position to counteract the monitored rotor vibration and selectively causes the motor to displace the balancing weight to the desired displacement position.

Other embodiments of the invention feature a method for online real time steam or combustion gas turbine engine rotor balancing by providing a turbine engine including a rotor having a rotation axis and one or more balance planes. The provided turbine engine further includes a selectively displaceable balancing weight that is coupled to the rotor. A motor is coupled to the balancing weight for selectively displacing the balancing weight along a displacement path in the balance plane. A turbine engine rotor vibration monitoring system monitors rotor vibration in real-time. Further, a control system is provided that is in turn coupled to rotor vibration monitoring system and the motor. The control system determines in real time a desired balance weight displacement position to counteract the monitored rotor vibration and selectively causes the motor to displace the balancing weight to the desired displacement position. The method is further performed by operating the turbine engine and monitoring operational rotor vibration with the vibration monitoring system. The controller determines in real time a desired balance weight displacement position to counteract the monitored rotor vibration; and causes the motor to displace the balancing weight to the desired displacement position. A weight position sensing system is provided in some exemplary embodiments to provide sensed weight position information to the controller. The sensed weight position is utilized by the controller as a control parameter for determining the desired weight position.

Additional embodiments of the invention feature a gas turbine engine, comprising compressor, combustor and turbine sections. A rotor is captured within the engine, having a rotation axis and one or more balance plane(s). A selectively displaceable balancing weight is coupled to the rotor. A motor is coupled to the balancing weight for selectively displacing the balancing weight along a displacement path in the balance plane. A turbine engine rotor vibration monitoring system is coupled to the engine, for monitoring rotor vibration in real-time. A control system is coupled to rotor vibration monitoring system and the motor, for determining in real time a desired balance weight displacement position to counteract the monitored rotor vibration and for selectively causing the motor to displace the balancing weight to the desired displacement position.

The respective objects and features of the invention embodiments may be applied jointly or severally in any combination or sub-combination by those skilled in the art.

DETAILED DESCRIPTION

After considering the following description, those skilled in the art will clearly realize that the teachings of various embodiments of the invention can be utilized in a motorized vibration balancer that is coupled to shaft/rotor at a balance plane, such as in a balancing ring. One or more motors displace one or more respective balancing weights to counteract monitored vibration, such as monitored vibration detected by a turbine engine vibration monitoring system. The motors are controlled by a control system that determines in real time a desired balance weight displacement position to counteract the monitored vibration and causes the motor to displace the balancing weight to the desired displacement position. In exemplary embodiments of the invention, one or more balancing weights have displacement paths that may be non-orthogonally aligned on one or more balance planes that are perpendicular to the rotor/shaft rotational axis. In exemplary embodiments the respective weight displacement paths are directed on the balance plane radially or tangentially relative to the rotor rotational axis. In other exemplary embodiments of the invention a balancing weight displacement sensor provides sensed weight displacement information that is coupled to the controller. The controller utilizes the sensed weight displacement information as a control parameter for determining the desired weight displacement position. In embodiments of the invention the motors are powered by a motor power source comprising an inductive power source having a stationary coil external to the rotor and a moving coil coupled to the rotor. In other embodiments the power source is a permanent magnet generator power source having a stationary magnet and at least one moving coil coupled to the rotor. Other power sources may be applicable to the envisioned design.

FIGS. 2 and 3show an embodiment of the turbo-machinery automatic self-balancing system in an exemplary combustion turbine engine30that includes a compressor section32, a combustion section34with a ring of combustors, a turbine section36and a rotor38that is rotatively mounted with the aforementioned turbine sections. The exemplary rotor38has three balancing rings40that define balance planes normal to the rotor's rotational axis. Motorized balancers60may be non-orthogonally aligned on the balance plane. WhileFIGS. 2 and 3show an exemplary rotor38with three balance planes and three motorized balancers60in each balancing ring40, an operational self-balancing system can be constructed with at least one or greater desired number of balance planes and at least one motorized balancer in each balance plane. Power is supplied to the motorized balancers60by a balancer power system including a stationary balancer power transfer device42mounted near the balance plane40(or anywhere within the rotor structure so long as power is transferred to the motorized balancers) and a balancer power source43that is coupled to the balancer power transfer device. As will be described in greater detail herein with respect toFIGS. 4-9, various embodiments of the motorized balancers60incorporate displaceable balancing weights that are displaced by motors60and their respective powered motor shafts64.

Sensor44is mounted near the balance plane40for monitoring operation of the motorized balancers60in the ring, for determining sensed weight displacement, generating sensed weight displacement information. Each sensor44is coupled to balance system controller46and provides sensed weight displacement information to the controller. The controller46is in communication with the turbine engine30vibration monitoring system (VMS)48that receives monitored engine vibration information provided by one or more VMS sensors49. As shown inFIG. 2, the VMS48is incorporated into the controller46, which may be structurally or operationally incorporated into the turbine engine30overall operational control system. The controller46is optionally coupled to a balancing system data storage device50, a human machine interface (HMI)52for providing operational information about the automatic balancing system to human operators and a communications pathway54, all of which may be incorporated into the overall turbine engine30operational monitoring and control system (not shown). In the exemplary embodiment ofFIG. 2, the sensor44sensed weight displacement information is utilized by the controller46and functions as a control parameter for determining the desired weight displacement position, desirably in a feedback control loop along with the VMS48monitored engine vibration information.

Exemplary embodiments of motorized balancer systems60are shown in detail inFIGS. 4-9. All of these embodiments functionally utilize a motor62to displace selectively a displacement weight along a displacement path that may be non-orthogonally aligned with its respective balancing ring140balance plane. Exemplary displacement paths are oriented or directed radially or tangentially relative to the rotor rotational axis. The balance system controller46in real time, utilizing available monitored motor vibration information and sensed weight displacement position from the corresponding sensor44(if available) determines a desired balance weight displacement position to counteract the monitored rotor vibration and selectively causes the motor to displace the balancing weight to that desired displacement position. The automatic balancing system is expected to attain steady state operation within a number of rotations of the rotor38. Given initial efforts to achieve at least first order static balance of the rotor38during initial fabrication or after service refurbishment it is not contemplated that balancing weights need to weigh more than approximately one pound and weight displacement along displacement paths are not contemplated to exceed a few inches in the radially oriented embodiment since movement is limited by the physical dimensions of the rotor, but may traverse the entire perimeter of the rotor at the balance plane location for the tangentially oriented embodiment. Accordingly, within appropriately designed weight displacement power requirements micro fractional horsepower motors in combination with high gear ratio should be sufficient to drive weight displacement in most turbo-machinery applications.

In the first motorized balancer system60embodiment ofFIG. 4the driven balancing weight66has internal female first drive screw threads68that engage with mating male second drive threads defined by a drive screw72, which in turn is coupled to the motor shaft64. The balancing weight66displaces within a radially oriented bore70that is defined in the balancing ring40. The motor62is rigidly coupled to the rotor38.

In the second motorized balancer system60embodiment ofFIG. 5, the driven weight74defines external circumferential threads76that are in mating engagement with the threaded ring bore78. The motor62is rigidly coupled to the rotor38with its motor shaft64directly coupled to the balancing weight74. Motor shaft64rotation drives the balancing weight74along the mating screw thread engaged surfaces.

Balancing weights in the embodiments ofFIGS. 6-9are displaced in tangential paths along the balance plane relative to the rotor38rotational axis along rails that are attached in fixed position on the rotor. In the third motorized balancer system60embodiment ofFIG. 6the driven weight80has an internal weight bore82that rides along the rail86. Drive screw88threads engage mating threads formed on the weight82. The motor62is attached in fixed position to the balancing ring40, with its motor shaft64coupled to the drive screw88. In the fourth motorized balancer system60embodiment ofFIG. 7the driven weight90also defines an internal weight bore92that rides along the fixed rail94. The motor62is affixed to the driven weight96, its own motor weight contributing to the aggregate weight of the displaced mass. The motor shaft64is coupled to a drive screw96and mates with a corresponding fixed position female threaded drive screw block98. In the fifth motorized balancer system60embodiment ofFIG. 8a rotatively mounted combination drive screw and rail100is retained in a fixed position within the balancing ring40. Weight102defines an internal cavity104within which motor62is rigidly coupled. Bearing blocks102allow the weight assembly to be displaced along the drive screw/rail100by mating engagement of opposing threads on drive gear108that is in turn coupled to the motor shaft64. The sixth motorized balancer system60embodiment ofFIG. 9is similar to the system ofFIG. 8, substituting a gear segment100′, formed in a rim of the balancing ring40. The weight102is displaced along the segment100′ by mating engagement of opposing threads on drive gear108′ that is in turn coupled to the motor shaft64.

Exemplary embodiments of the invention include motor62power sources, shown in9and10. InFIG. 9, the motor power source is an inductive pulse transmission system, having a stationary coil110in the power transfer device42and passing in close proximity a moving coil112in the balancing ring40that is coupled to the motor62of one of the weights. The relative motion between the two inductive pulse transmission system components creates a rapidly changing magnetic field with in the moving coil112, which induces a current pulse and in turn energizes the motor62. Weight displacement along the displacement path that is caused by the motor shaft64can be sensed by a remote sensor44or by monitoring the timing of the back EMF to the stationary coil110relative to a known angular location of the shaft. Sensed weight displacement is utilized by the balancing system controller46in a feedback loop to determine subsequent desired balance weight displacement positions and possible fault conditions, as previously described.

InFIG. 11the motor power source is a permanent or electro magnet generator power source having a stationary magnet120proximal the balancing ring40and at least one moving coil122that is coupled to the balancing ring. The magnet120excites the moving coil122and generates an induced current that powers the motor62. InFIG. 10the moving coil122comprises a known three phase alternating current generating coil arrangement and its induced current is rectified to direct current by a known rectifier124. Power is selectively switched to one or more motors62in one or more balancing rings40by one or more power triggering switches126, such as by known solid state switches. The switch126is in turn controlled by switching commands generated by remote sensor44(such as a known Hall Effect sensor) as the balancing ring40and its rotor38rotate past the remote sensor. Alternatively the motors62can be powered via known stationary contact brushes and rotor slip rings (not shown).