Patent Description:
As gas turbine engine compressor pressure ratios and internal temperatures continue to increase throughout a larger and wider operating envelope, material capabilities in the rear of the high pressure compressor start to become a limiting factor. If the high temperatures cannot be mitigated with large or complex air coolers, then flight restrictions will be needed. <CIT> discloses a clutched compressor section for a gas turbine engine. <CIT> discloses another clutched compressor section for a gas turbine engine.

Disclosed is a clutched compressor section of a gas turbine engine coupled to a rotor shaft according to claim <NUM>.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the decoupleable stage is located downstream of the group of stages.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the decoupleable stage is coupled to a shaft that is coaxially oriented with the rotor shaft.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the first engagement member and the second engagement member are disposed in an interference fit condition in the coupled condition, wherein a threshold centrifugal force overcomes the interference fit condition to dispose the first engagement member and the second engagement member in the decoupled condition.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the relative position of the first engagement member and the second engagement member is controlled with an electromagnetic field applied proximate the clutch mechanism.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the electromagnetic field is generated from a stator pack located proximate the clutch mechanism.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the first engagement member and the second engagement member are aero-viscously coupled to each other.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the decoupled condition is provided when the rotational speed of the rotor shaft exceeds a predetermined speed to reduce fluid compression and compressor temperature.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the plurality of rotor stages are part of a high pressure compressor.

Also disclosed is a gas turbine engine including the clutched compressor section according to claim <NUM>, a combustor section, and a turbine section.

The clutched compressor section according to claim <NUM> includes a plurality of compressor rotor stages axially spaced from each other and operatively coupled to each other, the at least one decoupleable rotor stage being one of the plurality of compressor rotor stages. Also included is a group of stages of the plurality of compressor rotor stages coupled to each other and to the rotor shaft, the at least one decoupleable rotor stage being coupled to the group of stages in the coupled condition and decoupled from the group of stages in the decoupled condition, the decoupled condition allowing the decoupleable rotor stage to freely rotate independently of the group of stages.

In the clutched compressor section according to claim <NUM>, the clutch mechanism includes a first engagement member extending from a disk of one of the rotor stages. The clutch mechanism also includes a second engagement member extending from a disk of the decoupleable stage, the relative position of the first engagement member and the second engagement member determining if the decoupleable stage and the remainder of the stages are in the coupled condition or the decoupled condition.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the decoupleable stage is located downstream of the remainder of stages.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that each of the remainder of the stages are coupled to each other and to a rotor shaft that directly drives the remainder of the stages.

Further disclosed is a method of controlling a temperature of a gas turbine engine compressor section according to claim <NUM>.

In one disclosed embodiment, the engine <NUM> bypass ratio is greater than about ten (<NUM>:<NUM>), the fan diameter is significantly larger than that of the low pressure compressor <NUM>, and the low pressure turbine <NUM> has a pressure ratio that is greater than about five (<NUM>:<NUM>). The geared architecture <NUM> may be an epicycle gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about <NUM>:<NUM>. It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present disclosure is applicable to other gas turbine engines including direct drive turbofans.

The fan section <NUM> of the engine <NUM> is designed for a particular flight condition--typically cruise at about <NUM> Mach and about <NUM>,<NUM> feet (<NUM>,<NUM> meters). The flight condition of <NUM> Mach and <NUM>,<NUM> feet (<NUM>,<NUM> meters), with the engine at its best fuel consumption--also known as "bucket cruise Thrust Specific Fuel Consumption ('TSFC')"--is the industry standard parameter of lbm of fuel being burned divided by lbf of thrust the engine produces at that minimum point.

The compressor section <NUM> includes a plurality of variable vanes. The variable vanes are positioned on a sync ring (not shown) and the orientation of the variable vanes is controlled by an actuator system. In particular, multiple vanes are disposed circumferentially about the compressor section <NUM> along, and operatively coupled to, a sync ring that synchronizes articulation of the variable vanes.

Referring to <FIG>, a portion of the compressor section <NUM> is shown in greater detail. In some embodiments, the portion of the compressor section <NUM> is the high pressure compressor <NUM>. The compressor section <NUM> includes a plurality of rotor stages <NUM> axially spaced from each other. Each rotor stage <NUM> includes a plurality of airfoils that are circumferentially spaced from each other. In the sectional view, a single rotor from each stage is illustrated. It is to be appreciated that more or fewer stages may be present in various embodiments. In the orientation of <FIG>, fluid is routed through the compressor section <NUM> from left to right and compressed therein. Therefore, rotor stages are considered "downstream" relative to other stages that are shown to the left in the illustration.

At high speed operation of the compressor section <NUM> under certain operating conditions, pressure ratio and temperature must be mitigated. To reduce the temperature, a clutch mechanism <NUM> described herein allows one or more of the plurality of rotor stages <NUM> to be decoupled from the remainder of the rotor stages <NUM>. In the illustrated embodiment, a single rotor stage <NUM> is decoupleable from the remainder of the rotor stages <NUM> and may be referred to herein as a decoupleable rotor stage <NUM>, but it is to be appreciated that more than one rotor stage may be decoupleable from the remainder of the rotor stages <NUM>. The remainder of the rotor stages <NUM> may also be referred to as a group of rotor stages <NUM>. In the illustrated embodiment, the decoupleable rotor stage <NUM> is a last stage of the rotor stages <NUM>, such that it is located axially downstream of the remainder of the rotor stages <NUM>. The aft portion of the compressor section <NUM> typically is subjected to the highest temperature, such that avoiding fluid compressive work in this region is beneficial, as described herein.

In one embodiment, each of the remainder of rotor stages <NUM> are coupled to a rotor shaft <NUM>, via respective disks <NUM>, that directly drives rotation of the remainder of rotor stages <NUM> during operation of the turbine section <NUM>. In other words, rotation of the rotor shaft <NUM> always results in rotation of the remainder of rotor stages <NUM>. As will be appreciated from the disclosure herein, the decoupleable rotor stage <NUM> is switchable between a coupled condition and a decoupled condition. In the coupled condition, the decoupleable rotor stage <NUM> is also rotationally driven by the rotor shaft <NUM> and is commonly rotated with the remainder of the rotor stages <NUM>. The rotation is driven by a coupled connection with the remainder of rotor stages <NUM>. In the decoupled condition, the decoupleable rotor stage <NUM> is disengaged from the remainder of rotor stages <NUM> and is free to rotate independently of the rotor shaft <NUM>. The decoupleable rotor stage <NUM> is operatively coupled to a shaft <NUM>, via a disk <NUM>, the shaft <NUM> being coaxially aligned with the rotor shaft <NUM> and concentrically positioned thereabout. In an alternative embodiment, the rotation of a decoupleable rotor stage <NUM> may be driven directly a by connection with the rotor shaft <NUM> when in the coupled condition such that the clutch mechanism <NUM> is situated between the decoupleable rotor stage <NUM> and the rotor shaft <NUM> without any other rotor stages <NUM> situated therebetween.

The clutch mechanism <NUM> includes a first engagement member <NUM> and a second engagement member <NUM> that are engageable with each other. The first engagement member <NUM> is operatively coupled to, or integrally formed with, one of the disks <NUM> of the remainder of rotor stages <NUM>. The second engagement member <NUM> is operatively coupled to, or integrally formed with, the disk <NUM> of the decoupleable rotor stage <NUM>. The first and second engagement members <NUM>, <NUM> extend toward each other and are in an overlapping condition, such that the length of each member extends past each other to define an overlapped region of the members. The engagement members <NUM>, <NUM> may be formed in any suitable shape, such as a substantial cylinder extending at least partially about the rotor shaft <NUM>.

The relative position of the engagement members <NUM>, <NUM> determines whether the decoupleable rotor stage <NUM> is in the coupled or decoupled condition. Various embodiments of the clutch mechanism <NUM> are contemplated. In some embodiments, the engagement members <NUM>, <NUM> are disposed in an interference fit condition in the coupled condition. In such an embodiment, the interference fit is loosened or eliminated once the rotational speed of the compressor section <NUM> provides a centrifugal force that exceeds a threshold force by radially growing or moving one of the engagement members <NUM>, <NUM>, relative to the other. In some embodiments, components such as pawls or the like may be included on one or both of the engagement members <NUM>, <NUM>, with the centrifugal force disengaging these components once the threshold force is exceeded. Once the speed is reduced, the centrifugal force is reduced, thereby facilitating re-engagement of the components to reposition the clutch mechanism <NUM> into the coupled condition. Alternatively, the engagement members <NUM>, <NUM> may be configured so that the interference fit is increased once the rotational speed of the compressor section <NUM> provides a centrifugal force that exceeds a threshold force by radially growing or moving one of the engagement members <NUM>, <NUM>, relative to the other. In this alternative embodiment, once the speed is reduced, the centrifugal force is reduced, thereby facilitating dis-engagement of the components to reposition the clutch mechanism <NUM> into the decoupled condition.

In other embodiments, an electromagnetic field is utilized to control the relative position of the engagement members <NUM>, <NUM>, thereby controlling the coupled or decoupled conditions. Many contemplated components and locations of the electromagnetic field are suitable. In one embodiment, the electromagnetic field is generated from a stator pack located proximate the clutch mechanism <NUM>. Additionally, it is contemplated that the engagement members <NUM>, <NUM> are coupled aero-viscously.

In operation, the at least one decoupleable rotor stage <NUM> is driven by the rotor shaft <NUM> in the coupled condition and not driven by the rotor shaft <NUM> in the decoupled condition. In the coupled condition, the decoupleable rotor stage <NUM> provides compressive work. In one embodiment, the decoupleable rotor stage <NUM> is able to spin freely when in the decoupled condition due to the connected relationship to shaft <NUM>, but is not adding any work or subsequent temperature rise to the fluid. The independent spinning allows for close speed matching as the main compressor speed is reduced and recoupling of stage <NUM> and stages <NUM> occurs, thus improving durability. Alternatively, the decoupleable rotor stage <NUM> may be locked into an aerodynamically ideal rotational position that optimizes operation when locked and also when started back up and when in coupled condition. The selectively coupleable nature of stage <NUM> can avoid unnecessary compression, thereby reducing the temperature within the compressor section <NUM>.

Claim 1:
A clutched compressor section (<NUM>) of a gas turbine engine (<NUM>) coupled to a rotor shaft (<NUM>), comprising:
at least one decoupleable rotor stage (<NUM>), the decoupleable rotor stage being switchable between a coupled condition and a decoupled condition with a clutch mechanism (<NUM>), the coupled condition coupling the decoupleable rotor stage with the rotor shaft, the decoupled condition decoupling the decoupleable rotor stage from the rotor shaft;
a plurality of compressor rotor stages (<NUM>) axially spaced from each other and operatively coupled to each other, the at least one decoupleable rotor stage being one of the plurality of compressor rotor stages;
a group of stages of the plurality of compressor rotor stages being coupled to each other and to the rotor shaft, the at least one decoupleable rotor stage (<NUM>) being coupled to the group of stages in the coupled condition and decoupled from the group of stages in the decoupled condition, the decoupled condition allowing the decoupleable rotor stage to freely rotate independently of the group of stages;
a first engagement member (<NUM>) extending from a disk of one of the stages of the group of stages; and
a second engagement member (<NUM>) extending from a disk of the decoupleable stage,
characterized in that
the relative position of the first engagement member and the second engagement member determines if the decoupleable stage and the group of stages are in the coupled condition or the decoupled condition.