Gas turbine engine assembly and method of assembling same

This invention relates generally to gas turbine engines, and more specifically to gas turbine engine assemblies and methods of assembling the same.

At least some known gas turbine engines include a fan assembly, a core engine, and a low-pressure or power turbine. The core engine includes at least one compressor, a combustor, and a high-pressure turbine that are coupled together in a serial flow relationship. Air entering the core engine is mixed with fuel and ignited to form a high energy gas stream. The high energy gas stream flows through the high-pressure turbine to rotatably drive the high-pressure turbine and thus the compressor via a first drive shaft. The gas stream expands as it flows through the high-pressure turbine to facilitate driving the low-pressure turbine which rotatably drives the fan assembly through a second drive shaft.

To improve engine efficiency, it is desirable to operate the fan assembly at a relatively low speed to improve fan efficiency and to operate thehigh-pressurelow-pressureturbine at a relatively high speed to improve turbine efficiency. Accordingly, neither the fan speed nor thehigh-pressurelow-pressureturbine speed may be totally optimized to improve overall engine efficiency.

As such, at least one known gas turbine engine includes a gearbox coupled between the low-pressure turbine and the fan assembly to facilitate reducing the operational speed of the fan assembly. However, utilizing a gearbox to reduce the speed of the fan assembly and thus increase the efficiency of the fan assembly reduces the quantity of airflow channeled to the booster compressor. As a result, additional stages may be added to the booster compressor to achieve proper pressure, thus increasing the overall weight, design complexity and/or manufacturing costs of such an engine.

is a schematic illustration of an exemplary gas turbine engine assemblyhaving a longitudinal axis. Gas turbine engine assemblyincludes a fan assembly, and a core gas turbine enginethat includes a high-pressure compressor, a combustor, and a high-pressure turbine. In the exemplary embodiment, gas turbine engine assemblyalso includes a low-pressure turbineand a booster compressor(also referred to as booster 22 herein).

Fan assemblyincludes an array of fan bladesextending radially outward from a rotor disk. Enginehas an intake sideand an exhaust side. Boosterand low-pressure turbineare coupled together by a first drive shaft, and compressorand high-pressure turbineare coupled together by a second drive shaft. Fan assemblyis supported on a novel frameand driven by shaftthrough reduction gearbox.

is a schematic diagram of a portion of gas turbine engine assemblyshown in. As shown in, boosterincludes a plurality of circumferentially-spaced inlet guide vanes (IGV)to facilitate channeling airflow entering gas turbine enginedownstream through booster. In the exemplary embodiment, gas turbine engine assemblyalso includes a plurality of outlet guide vane (OGV) assembliesthat are coupled downstream from booster compressor. In one embodiment boosterincludes less than four stagesof rotor bladesthat are each coupled to a respective rotor disk. In the exemplary embodiment, booster compressorincludes two stagesof rotor blades.

In the exemplary embodiment, boosteris coupled to low-pressure turbinevia shaft. For example, in the exemplary embodiment, gas turbine engineincludes a cone or diskthat is connected at a first or forward enddriven byto a shaft extension 70, which is coupled toshaftutilizing a plurality of splines, and at a second or aft endtoaftdisk, as shown in. As such, boosteris coupled to low-pressure turbinesuch that boosterand low-pressure turbine20rotate at the same rotational speed in a first rotational direction. More specifically, gas turbine engineincludesatheshaft extensionthat includes a first or forward endthat is coupled to diskand a second or aft endthat is coupled to drive shaft, and thus low-pressure turbinevia splines.

In the exemplary embodiment, gas turbine enginealso includes a gearboxthat is coupled between fan assemblyand drive shaftto facilitate rotating fan assembly. In one embodiment, gearboxis an epicyclical gearbox that is configured to rotate fan assemblyin opposite rotational directionwith respect to rotational directionin which low-pressure turbineand boostereach rotate. Gearboxhas a generally toroidal shape and is configured to be positioned circumferentially about drive shaftto extend substantially about drive shaft. As shown in, gear-boxincludes a support structurethat is configured to provide structural support to gearboxsuch that gearboxis maintained in a substantially fixed position within gas turbine engine. As such, gearboxincludes an inputthat is coupled to shaftvia shaft extensionand an outputthat is coupled to fan assemblyto facilitate driving fan assembly.

In the exemplary embodiment, gas turbine enginealso includes a flex connectionthat is coupled between inputand shaft extensionto facilitate providing both axial and radial support between gearboxand shaft. For example, during operation, flex connectionmay absorb any rotational torque that is transmitted between gearboxand shaftto facilitate extending the operational life of both gearboxand shaft. Moreover, flex connectionmay also be utilized to facilitate aligning gearboxand shaftduring engine operation.

In one embodiment, gearboxhas a gear ratio of approximately 2.0 to 1 such that fan assemblyrotates at a rotational speed that is approximately one-half the rotational speed of low-pressure turbine.

A first bearing assembly, such as thrust bearing assembly, is positioned about drive shaftand/or longitudinal axis. Thrust bearing assemblyoperatively couples and/or is mounted between drive shaftand a frameof core gas turbine engine. Thrust bearing assemblyincludes a radially positioned inner racethat is mounted with respect to drive shaft. As shown in, inner raceis mounted to drive shaft extensionoperatively coupled to drive shaftso that inner raceis rotatable about longitudinal axiswith drive shaft. Bearing assemblyalso include a radially outer racethat is coupled to frameand acts as a ground for the transfer of thrust loads and/or forces developed or generated by gearbox, and at least one roller element, such as a plurality of bearingsthat are movably positioned between inner raceand outer race.

A second bearing assembly, such as thrust bearing assembly, is positioned between fan assemblyand gearbox output. As such, thrust bearing assemblyoperatively couples fan assemblyto gearboxand acts to ensure that thrust loads and/or forces developed or generated by fan assemblyare not transferred to gearbox. Thrust bearing assemblyincludes a radially positioned inner racethat is mounted with respect to gearbox outputand a radially outer racethat is coupled to a frameand acts as a ground for the transfer of thrust loads and/or forces developed or generated by fan assembly, and at least one roller element, such as a plurality of bearingsthat are movably positioned between inner raceand outer race. Framecarries the fan radial, thrust, and overturning moment generated from bearingand. Framealso transfers these loads to the outer engine structure and mounts. By use of frame, framecan be minimized with respect toits'itsoverall axial dimensions thus minimizing weight of the engine system.

As a result of transferring thrust loads and/or forces to thrust bearing assembly, the transfer of thrust loads and/or forces through gearbox, operatively coupled to fan assembly, is prevented or limited. In alternative embodiments, any suitable bearing assembly known to those skilled in the art and guided by the teachings herein provided can be used for, or in addition to, bearing assemblyand/or bearing assembly.

To facilitate maintaining gearbox outputisina substantially fixed radial position, gas turbine engine assemblyalso include a roller bearing assemblythat is coupled between gearbox outputand support structure. Specifically, bearing assemblyincludes a rotating inner racethat is coupled to gearbox output, a stationaryinnerouterrace that is coupled to support structure, and a plurality of roller elementsthat are positioned betweentheinner and outer racesand, respectively.

In the exemplary embodiment, thrust bearing assemblyand roller bearing assemblyfacilitate providing rotational support to fan assemblysuch that fan assemblyand gearbox outputmay rotate freely with respect to support structureand. Accordingly, bearing assembliesandfacilitate maintaining fan assemblyin a relatively fixed radial position within gas turbine engine assembly.

In the exemplary embodiment, gas turbine engine assemblyalso includes a first pair of labyrinth sealsthat facilitate sealing an upstream side of boosterfrom sump, and a second pair of labyrinth sealsthat facilitate sealing a downstream side of boosterfrom sump.

To assemble gas turbine engine, a core gas turbine engine including a high-pressure compressor, a combustor, and a turbine is provided. A low-pressure turbine is coupled axially aft from the core gas turbine engine, and a fan assembly is coupled axially forward from the core gas turbine engine. The booster compressor is then coupled to the low-pressure turbine such that the booster compressor and the low-pressure turbine rotate at a first rotational speed.

More specifically, a drive shaft is coupled to the low-pressure turbine, and a gearbox coupled between the drive shaft and the fan assembly such that the fan assembly rotates at a second rotational speed that is different and/or less than the first rotational speed. To facilitate absorbing thrust loads, a first thrust bearing assembly is coupled between the drive shaft and the gearbox such that the thrust loads generated by the gearbox are transferred to ground, and a second thrust bearing assembly between the gearbox and the fan assembly such that the thrust loads generated by the fan assembly are transferred to ground.

During operation, as drive shaftrotates, drive shaft extensioncauses gearbox inputto rotate in first rotational direction, which subsequently rotates gearbox out-putin opposite second rotational direction. Because gearbox outputis coupled to fan assembly, drive shaftcauses fan assemblyto rotate via gearboxin opposite second direction, i.e. in an direction that is opposite from the rotational directions of both low-pressure turbineand booster. In one embodiment, gearboxis located within a sumpsuch that lubrication fluid within the sump may be utilized to lubricate at least portions of gearbox. For example, during operation, gearboxis continuously lubricated within sump.

The gas turbine engine assembly described herein includes a booster compressor that is coupled directly to the low-pressure turbine via a drive shaft to enable the booster compressor to operate at a rotational speed that is greater than the rotational speed of the fan assembly. Moreover, that gas turbine engine assembly includes a gearbox coupled between the low-pressure turbine and the fan assembly. As a result, the rotational speeds of both the fan assembly and the booster compressor can be optimized. Specifically, the speed of the fan assembly can be reduced to optimize the airflow produced by the fan assembly, and the speed of the booster compressor can be increased to optimize the booster compressor stage count and drive the turbine stage count lower. As a result, the fan booster is driven at the low-pressure turbine speed thus reducing booster stage count and increasing turbine efficiency which may be used for power extraction in an electric accessory aircraft.

Exemplary embodiments of a gas turbine engine assembly and methods of assembling the gas turbine engine assembly are described above in detail. The assembly and method are not limited to the specific embodiments described herein, but rather, components of the assembly and/ or steps of the method may be utilized independently and separately from other components and/or steps described herein. Further, the described assembly components and/or the method steps can also be defined in, or used in combination with, other assemblies and/or methods, and are not limited to practice with only the assembly and/or method as described herein.

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.