Methods and apparatus for controlling variable stator vanes

An actuation system for a plurality of variable stator vanes pivotally mounted in a casing of a compressor. The system includes a plurality of levers each having a proximal end and an opposite distal end. Each of the proximal ends are fixedly coupled to a corresponding stator vane of the plurality of variable stator vanes for pivoting the corresponding stator vane about a stator vane axis. The system also includes an actuation ring coaxially surrounding the casing adjacent the plurality of levers. The actuation ring is coupled to the distal ends of each of the plurality of levers for pivoting the levers as the actuation ring is rotated about a compressor rotation axis. The actuation ring includes a pin extending outward from a radially outward surface of the actuation ring. The system also includes a template comprising a slot for receiving at least a portion of the actuation ring pin. The slot includes a shape configured to guide rotation of the actuation ring about the compressor rotation axis when the template is moved relative to the actuation ring.

BACKGROUND OF THE INVENTION

This invention relates generally to compressors, and more specifically to compressor variable stator vane assemblies.

In gas turbine engines, air is pressurized in a compressor and channeled to a combustor wherein it is mixed with fuel and ignited for generating hot combustion gases. The hot combustion gases flow downstream into one or more turbine stages which extract energy therefrom for powering the compressor and producing useful work. At least some known compressors have a plurality of axial stages which compress the air in turn as it flows downstream. Each compressor stage may include a row of rotor blades extending radially outwardly from a compressor spool or disk, and a cooperating row of stator vanes extending radially inwardly from an annular casing.

To control performance and stall margin of the compressor, at least some known stator vane rows are variable for selectively adjusting an angle of the vanes relative to the air being compressed. At least some known variable stator vanes include a spindle which extends radially outwardly through a casing and to which is attached a lever. The lever in turn is pivotally joined to an actuation ring coaxially surrounding the compressor casing. At least some known variable stator vane assemblies join each of the actuation rings for different variable stages to a common beam pivotally joined to the casing at one end and joined to a suitable actuator at an opposite end. The actuator pivots the beam which in turn rotates the actuation rings connected thereto which in turn rotates the respective levers attached thereto for pivoting the corresponding stator vanes. However, an amount of stator vane pivoting may vary from stage to stage since the several actuation rings are joined to the common beam at correspondingly different pivoting lengths from the pivoting end of the beam. Moreover, the common actuation beam and/or interconnections between the beam and the actuation rings may increase the complexity and/or weight of some known variable stator vane assemblies, and therefore may increase costs and maintenance.

Because gas turbine engines sometimes operate over a range of output power, the operation of the compressor may be correspondingly scheduled for maximizing efficiency of operation without undergoing undesirable aerodynamic stall. Vane scheduling is controlled by the kinematic motion of the levers, actuation rings, and actuation beam. However, at least some known variable stator vane assemblies may be limited to unidirectional tracking of the stator vanes, which may result in a compromised schedule of the stator vanes. Moreover, once at least some known variable stator vane assemblies are configured for a predetermined schedule, it may be difficult and costly to adjust the schedule.

BRIEF SUMMARY OF THE INVENTION

In one aspect, an actuation system is provided for a plurality of variable stator vanes pivotally mounted in a casing of a compressor. The system includes a plurality of levers each having a proximal end and an opposite distal end. Each of the proximal ends are fixedly coupled to a corresponding stator vane of the plurality of variable stator vanes for pivoting the corresponding stator vane about a stator vane axis. The system also includes an actuation ring coaxially surrounding the casing adjacent the plurality of levers. The actuation ring is coupled to the distal ends of each of the plurality of levers for pivoting the levers as the actuation ring is rotated about a compressor rotation axis. The actuation ring includes a pin extending outward from a radially outward surface of the actuation ring. The system also includes a template comprising a slot for receiving at least a portion of the actuation ring pin. The slot includes a shape configured to guide rotation of the actuation ring about the compressor rotation axis when the template is moved relative to the actuation ring.

In another aspect, a compressor includes a variable stator vane assembly. The variable stator vane assembly includes a plurality of variable stator vanes pivotally mounted in a casing of the compressor for rotation about a stator vane axis. The assembly also includes a plurality of levers each having a proximal end and an opposite distal end. Each of the proximal ends is fixedly coupled to a corresponding stator vane of the plurality of variable stator vanes for pivoting the corresponding stator vane about the stator vane axis. An actuation ring coaxially surrounds the casing adjacent the plurality of levers. The actuation ring is coupled to the distal ends of each of the plurality of levers for pivoting the levers as the actuation ring is rotated about a compressor rotation axis. The actuation ring includes a pin extending outward from a radially outward surface of the actuation ring. The assembly also includes a template including a slot for receiving at least a portion of the actuation ring pin. The slot includes a shape configured to guide rotation of the actuation ring about the compressor rotation axis when the template is moved relative to the actuation ring.

In another aspect, an actuation system is provided for a plurality of variable stator vanes pivotally mounted in a casing of a compressor. The system includes a plurality of levers each having a proximal end and an opposite distal end. Each of the proximal ends fixedly coupled to a corresponding stator vane of the plurality of variable stator vanes for pivoting the corresponding stator vane about a stator vane axis. The system also includes a template including a pin extending inward from a radially inward surface of the template. An actuation ring coaxially surrounds the casing adjacent the plurality of levers. The actuation ring is coupled to the distal ends of each of the plurality of levers for pivoting the levers as the actuation ring is rotated about a compressor rotation axis. The actuation ring includes a slot for receiving at least a portion of the template pin. The slot includes a shape configured to guide rotation of the actuation ring about the compressor rotation axis when the template is moved relative to the actuation ring.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a schematic illustration of a gas turbine engine10including a low, or intermediate, pressure compressor12, a high pressure compressor14, and a combustor assembly16. Engine10also includes a high pressure turbine18, and a low, or intermediate, pressure turbine20arranged in a serial flow relationship. Compressor12and turbine20are coupled by a first shaft22, and compressor14and turbine18are coupled by a second shaft24. Engine10includes an axis of rotation26, which may be referred to herein as a “compressor rotation axis” and/or an “engine rotation axis”, about which components of compressors12and14and turbines18and20rotate during operation of engine10. In one embodiment, engine10is an LM6000 engine commercially available from General Electric Company, Cincinnati, Ohio.

In operation, air flows through low pressure compressor12from an upstream side28of engine10and compressed air is supplied from low pressure compressor12to high pressure compressor14. Compressed air is then delivered to combustor assembly16where it is mixed with fuel and ignited. The combustion gases are channeled from combustor16to drive turbines18and20.

FIG. 2is a schematic view of a section of high pressure compressor14. Compressor14includes a plurality of stages50, wherein each stage50includes a row of rotor blades52and a row of variable stator vane assemblies56. Rotor blades52are typically supported by rotor disks58, and are connected to rotor shaft24. Rotor shaft24is a high pressure shaft that is also connected to high pressure turbine18(shown inFIG. 1). Rotor shaft24is surrounded by a stator casing62that supports variable stator vane assemblies56.

Each variable stator vane-assembly56includes a plurality of variable vanes74each having a respective vane stem76. Vane stem76protrudes through an opening78in casing62. Each variable vane assembly56also includes a lever arm assembly80extending from variable vane74that is utilized to rotate variable vanes74. Vanes74are oriented relative to a flow path through compressor14to control air flow therethrough. In addition, at least some vanes74are attached to an inner casing82.

FIG. 3is a partly sectional axial view of a portion of variable stator vane assembly56.FIG. 4is a perspective view of a portion of variable stator vane assembly56. To facilitate increasing efficiency of compressor14and/or maintaining a suitable stall margin, variable vanes74are selectively pivotable over a scheduled range of pivot angles A to correspondingly vary the orientation of individual vanes74relative to the flow of air through compressor14. To facilitate pivoting vanes74, each variable vane assembly56is coupled to an actuation ring84of the corresponding compressor stage50. Each actuation ring84coaxially surrounds stator casing62adjacent lever arm assemblies80of the corresponding variable vane assembly56. Although any suitable structure and/or means may be used, whether described and/or illustrated herein, in the exemplary embodiment each variable vane74is coupled to the corresponding actuation ring84utilizing lever arm assembly80. More specifically, in the exemplary embodiment lever arm assembly80includes a first, or proximal, end86that is removably coupled to a corresponding variable vane74, and a second, or distal, end88that is removably coupled to actuation ring84. Lever arm assembly proximate ends86may each be coupled to the corresponding vane74using any suitable structure and/or means, whether described and/or illustrated herein. Similarly, lever arm assembly distal ends88may each be coupled to the corresponding actuation ring84using any suitable structure and/or means, whether described and/or illustrated herein, such as, but not limited to, a slip joint89, as will be described in more detail below.

During operation, actuation ring84is rotated, which may also be referred to herein as translated, around engine rotation axis26(shown inFIG. 1). Because lever arm assembly80is coupled to actuation ring84, translating actuation ring84about engine rotation axis26causes lever arm80to move vane stem76, and thus variable vane74around a stator vane axis87that is about normal to engine rotation axis26. Actuation rings84are translated about engine rotation axis26using a template90. Template90is coupled to stator casing62for movement relative to casing62. Although template90may be coupled to stator casing62for movement relative thereto in any direction and/or along any axis that enables template90to function as described and/or illustrated herein, in the exemplary embodiment template90moves along engine rotation axis26. Template90is positioned relative to stator casing62such that template90extends over a radially outward surface92of one or more actuation rings84. Although template90is illustrated as extending over three actuation rings84, template90may extend over any number of actuation rings. Accordingly, template90may translate any number of actuation rings84about engine rotation axis26.

In the exemplary embodiment, template90includes three elongate slots94extending therethrough. Each slot94receives a portion of an actuation pin96that extends radially outward from a corresponding actuation ring radially outward surface92. Generally, as template90is moved along engine rotation axis26, inner surfaces95of each slot94contact the corresponding actuation pin96causing pin96to move along slot94and thereby causing the corresponding actuation ring84to translate about engine rotation axis26. In other words, each slot94guides movement of the corresponding actuation pin96, which in turn rotates the corresponding actuation ring84. Each slot94includes a shape and/or size that is configured to guide rotation of the corresponding actuation ring84between a predetermined scheduled range of pivot angles for the corresponding stator vanes74coupled thereto. As such, a shape and/or size of each of slots94can be predetermined to facilitate increasing an efficiency of compressor14and/or maintaining a suitable stall margin. Slots94may have any shape and/or size, whether described and/or illustrated herein, that enable slots94to function as described herein, for example to guide translation of the corresponding actuation ring84between a predetermined scheduled range of pivot angles for the corresponding stator vanes74coupled thereto. Examples of shapes of slots94include, but are not limited to, slots94including one or more curved portions and/or slots including one or more straight portions. Although three slots94are illustrated, template90may include any number of slots94for guiding rotation of any number of actuation rings84.

In some embodiments, for example in addition or alternative to slots94and/or actuation pins96, template90includes a pin (not shown) that extends radially inward from a radially inward surface98of template90and one or more of actuation rings84includes a slot (not shown) for receiving the pin. Similar to the exemplary embodiment, as template90is moved along engine rotation axis26, each template pin contacts corresponding radially inner surfaces (not shown) of each actuation ring slot causing the template pin to move along the actuation ring slot and thereby causing the corresponding actuation ring84to translate about engine rotation axis26. In other words, each actuation ring slot guides rotation of the corresponding actuation ring84. Moreover, similar to the exemplary embodiment each actuation ring slot includes a shape and/or size that is configured to guide rotation of the corresponding actuation ring84between a predetermined scheduled range of pivot angles for the corresponding stator vanes74coupled thereto. As such, a shape and/or size of each of the actuation ring slots can be predetermined to facilitate increasing an efficiency of compressor14and/or maintaining a suitable stall margin. Other than their locations, the actuation ring slots and template pins are substantially identical to slot94and pin96, respectively, and therefore will not be described in more detail herein. As they are substantially identical, anything described and/or illustrated herein with respect to slot94and/or pin96is applicable to the actuation ring slots and/or the template pins, respectively.

FIG. 5is a top plan view of a portion of variable stator vane assembly56illustrating an embodiment wherein one or more slots94and their corresponding actuation pins96include a plurality of teeth configured to interdigitate to facilitate movement of pins96within slots94. More specifically, one or more actuation pins96are rotatably coupled to the corresponding actuation ring84for rotation relative thereto about a central longitudinal axis100of each pin96. In the embodiment illustrated inFIG. 5, a portion of inner surfaces95of slot(s)94include a plurality of teeth102extending radially inward (relative to longitudinal axis100) therefrom that interdigitate with a plurality of teeth104extending radially outward (relative to longitudinal axis100) from a radially outer surface106of actuation pin(s)96. Teeth102and104and the rotation of pin(s)96may facilitate movement of pin(s)96within the corresponding slot(s)94and, in some embodiments, may facilitate securing pin(s)96at one or more predetermined locations within the corresponding slot(s)94and thereby may facilitate securing the corresponding actuation ring84in one or more predetermined positions about engine rotation axis26.

Referring again toFIGS. 3 and 4, movement of template90along engine rotation axis26may be driven by any suitable structure and/or means, such as, but not limited to electrical, pneumatic, and/or hydraulic power. In the exemplary embodiment, an actuator108is coupled to an end portion110of template90via an actuation rod112. Movement of actuation rod112along engine rotation axis26causes movement of template along axis26. Although template90may be coupled to stator casing62in any suitable other fashion, manner, configuration, arrangement, and/or by any other suitable structure and/or means, in the exemplary embodiment portions of template90are received within openings114of a plurality of retaining clips116, which are coupled to stator casing62. Retaining clips116may facilitate maintaining a general position of template90over one or more actuation rings84. Moreover, retaining clips may facilitate guiding movement of template90along engine rotation axis26.

A plurality of circumferentially spaced apart ring guides118are fixedly coupled to casing62for guiding circumferential movement (i.e. rotation/translation) of actuation rings84about engine rotation axis26. More specifically, ring guides118facilitate restraining or limiting movement of actuation rings84along engine rotation axis26while guiding circumferential movement about axis26. Although ring guides118may have any suitable configuration, arrangement, location, orientation, and/or may include any suitable structure and/or means, in the exemplary embodiment ring guides118are coupled to stator casing62on opposite axial sides of actuation rings84. In the exemplary embodiment, ring guides118may include suitable rollers to facilitate reducing friction between guides118and actuation rings84.

As discussed above, in the exemplary embodiment each lever arm assembly end86is coupled to the corresponding actuation ring84using a slip joint89. However, in some embodiments some or all of lever arm assembly ends88are coupled to the corresponding actuation ring84without using a slip joint89. Slip joints facilitate accommodating the limit or restraint of movement of actuation rings84along engine rotation axis26by varying a pivot length of lever arm assemblies80as actuation rings84are rotated about engine rotation axis26. Slip joints89may also facilitate non-linear motion, or scheduling, between actuation rings84and their corresponding stator vanes74, which may facilitate optimization and/or tailoring of scheduling of vanes74. Although slip joints89may be any type of slip joint have any suitable arrangement, configuration, structure, and/or means, in the exemplary embodiment slip joints89include a pin120extending radially outwardly from actuation ring radially outer surface92and an elongate slot122within each lever arm assembly distal end88. At least a portion of each pin120is received within a corresponding slot122. As actuation rings84rotate about engine rotation axis26to vary the position of the corresponding lever arm assembly80, pins90move within the corresponding slot122to vary the pivot length of the lever arm assembly80. Each slot122has a suitable length124which allows the corresponding pin120to move between opposite ends of the slot122over the intended maximum range of rotation of the corresponding lever arm assembly80. Because movement of actuation rings84along axis26is limited or restrained by ring guides118, pins120generally remains in the same axial plane even as actuation rings84are rotated. Because lever arm assemblies80each rotate relative to stator vane axis87, slots120may each facilitate preventing binding between a lever arm assembly80and the corresponding actuation ring84to facilitate allowing the lever arm assembly80to be turned over its full intended pivoting range, with the corresponding pin120sliding along slot length124. Although as illustrated each slot122generally extends straight along a longitudinal axis128of the corresponding lever arm assembly80, in some embodiments one or more of slots122are angled relative to axis128, curved, and/or arcuate to further facilitate non-linear motion, or scheduling, between actuation rings84and their corresponding stator vanes74. In addition or alternative to pins120and slots122, one or more slip joints89may include a pin (not shown) extending from a lever arm assembly80and a slot (not shown) within a corresponding actuation ring84.

During operation, as template90is moved along engine rotation axis26, slot inner surfaces95contact the corresponding actuation pin96causing pin96to move along slot94and thereby causing the corresponding actuation ring84to translate about engine rotation axis26. Because lever arm assembly80is coupled to actuation ring84, translating actuation ring84about engine rotation axis26causes lever arm80to move vane stem76, and thus variable vane74around stator vane axis87. As template90moves along axis26to thereby rotate vanes74, the size and/or shape of slots94guides rotation of the corresponding actuation ring84between a predetermined scheduled range of pivot angles for the corresponding stator vanes74coupled thereto.

The above-described variable stator vane assembly56may facilitate non-unidirectional scheduling of stator vanes74. More specifically, at least some known vane schedules are determined as a function of corrected speed of the engine. For example, as the corrected speed of the engine increases, the stator vanes may be rotated to be generally more “open” relative to air flowing through the engine compressor. As the corrected speed of the engine decreases, the stator vanes may be rotated to be generally more “closed” relative to air flowing through the engine compressor. As such, at least some known vane schedules may be unidirectional relative to engine corrected speed. However, template90, and for example slots94, of variable stator vane assembly56may facilitate non-unidirectional scheduling of variable stator vanes74. More specifically, the size and/or shape of template slots94may be configured to rotate stator vanes74such that they are generally more “open” as a corrected speed of engine10increases. However, once the corrected speed of engine10increases above a predetermined threshold, the size and/or shape of slots94may be configured to rotate stator vanes74to be move “closed” as the corrected speed increases above the predetermined threshold. Similarly, the size and/or shape of template slots94may be configured to rotate stator vanes74such that they are generally more “closed” as a corrected speed of engine10decreases. However, once the corrected speed of engine10decreases below a predetermined threshold, the size and/or shape of slots94may be configured to rotate stator vanes74to be more “open” as the corrected speed decreases below the predetermined threshold. Accordingly, variable stator vane assembly56may facilitate non-unidirectional scheduling of variable stator vanes. Moreover, because a particular schedule of stator vanes74can be changed by changing template90, variable stator vane assembly56may facilitate easier changing between different schedules as compared to at least some known variable stator vane assemblies.

Although the assemblies, systems, and methods described and/or illustrated herein are described and/or illustrated with respect to a gas turbine engine, and more specifically a gas turbine engine compressor, practice of the systems and methods described and/or illustrated herein is not limited to gas turbine engine compressors, nor gas turbine engines or compressors generally. Rather, the assemblies, systems, and methods described and/or illustrated herein are applicable to any variable stator vane assembly.

Exemplary embodiments of systems, assemblies, engines, and methods are described and/or illustrated herein in detail. The systems, assemblies, engines, and methods are not limited to the specific embodiments described herein, but rather, components of each system, engine, and assembly, as well as steps of each method, may be utilized independently and separately from other components and steps described herein. Each component, and each method step, can also be used in combination with other components and/or method steps.

When introducing elements/components/etc. of the systems, engines, assemblies, and methods described and/or illustrated herein, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the element(s)/component(s)/etc. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional element(s)/component(s)/etc. other than the listed element(s)/component(s)/etc.