Gas turbine engine assembly and methods of assembling same

A method for assembling a gas turbine engine includes providing a core gas turbine engine including a high-pressure compressor, a combustor, and a turbine, and coupling a counter-rotating fan assembly to the core gas turbine engine such that air discharged from the counter-rotating fan assembly is channeled directly into an inlet of the gas turbine engine compressor.

BACKGROUND OF THE INVENTION

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 forward fan, a core engine, and a power turbine. The core engine includes at least one compressor, a combustor, a high-pressure turbine and a low-pressure turbine coupled together in a serial flow relationship. More specifically, the compressor and high-pressure turbine are coupled through a shaft to define a high-pressure rotor assembly. 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 such that the shaft, in turn, rotatably drives the compressor.

The gas stream expands as it flows through the low-pressure turbine positioned forward of the high-pressure turbine. The low-pressure turbine includes a rotor assembly having a fan coupled to a drive shaft. The low-pressure turbine rotatably drives the fan through the drive shaft. To facilitate increasing engine efficiency, at least one known gas turbine engine includes a counter-rotating low-pressure turbine that is coupled to a counter-rotating fan and a booster compressor.

An outer rotating spool, a rotating frame, a mid-turbine frame, and two concentric shafts, are installed within the gas turbine engine to facilitate supporting the counter-rotating low-pressure turbine. The installation of the aforementioned components also enables a first fan assembly to be coupled to a first turbine and a second fan assembly to be coupled to a second turbine such that the first fan assembly and the second fan assembly each rotate in the same rotational direction as the first turbine and the second turbine, respectively. Accordingly, the overall weight, design complexity and/or manufacturing costs of such an engine are increased.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, a method of assembling a gas turbine engine is provided. The method includes providing a core gas turbine engine including a high-pressure compressor, a combustor, and a turbine, and coupling a counter-rotating fan assembly to the core gas turbine engine such that air discharged from the counter-rotating fan assembly is channeled directly into an inlet of the gas turbine engine compressor.

In another aspect, a turbine engine assembly is provided. The turbine engine assembly includes a core gas turbine engine including a high-pressure compressor, a combustor, and a turbine, and a counter-rotating fan assembly coupled to the core gas turbine engine such that air discharged from the counter-rotating fan assembly is channeled directly into an inlet of the gas turbine engine compressor.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a cross-sectional view of a portion of an exemplary turbine engine assembly10having a longitudinal axis11. In the exemplary embodiment, turbine engine assembly10includes a core gas turbine engine12generally defined by a frame13. A low-pressure turbine14is coupled axially aft of core gas turbine engine12and a counter-rotating fan assembly16is coupled axially forward of core gas turbine engine12.

Core gas turbine engine12includes an outer casing20that defines an annular core engine inlet22. In one embodiment, core gas turbine engine12is a core CFM56 gas turbine engine available from General Electric Aircraft Engines, Cincinnati, Ohio.

A high-pressure, multi-stage, axial-flow compressor26receives pressurized air directly from fan assembly16, without passing through a booster compressor, and further increases the pressure of the air to a second, higher pressure level. More specifically, air is discharged from the counter-rotating fan assembly16at a first operating pressure, channeled through a gooseneck78, and received at core gas turbine high-pressure compressor26at approximately the first or same operational pressure. The high-pressure air is channeled to a combustor28and is mixed with fuel. The fuel-air mixture is ignited to raise the temperature and energy level of the pressurized air. The high energy combustion products flow to a first or high-pressure turbine30for driving compressor26through a first rotatable drive shaft32, and then to second or low-pressure turbine14to facilitate driving counter-rotating fan assembly16through a second rotatable drive shaft34that is coupled coaxially with first drive shaft32. After driving low-pressure turbine14, the combustion products leave turbine engine assembly10through an exhaust nozzle36to provide propulsive jet thrust. In the exemplary embodiment,FIG. 1illustrates a high-pressure turbine30having a single stage. Optionally, high-pressure turbine30may have a plurality of stages a quantity of which is selected based on the overall desired compression ratio of the turbine engine assembly.

In one embodiment, counter-rotating fan assembly discharges a predetermined quantity of air based on the gas turbine engine compression ratio to the core gas turbine engine. More specifically, high-pressure compressor26includes a plurality of stages27wherein each stage further increases the pressure from the previous stage such that core gas turbine engine12has a compression ratio based on the quantity of stages27utilized within high-pressure compressor26. Moreover, although a single core gas turbine is illustrated, it should be realized that the gas turbine engine12may include a compressor having any quantity of compression stages, and thus a wide variety of compression ratios.

Accordingly, in one embodiment, core gas turbine engine12includes a plurality of compression stages27that are predetermined based on the quantity and/or pressure of the compressed air discharged from the counter-rotating fan assembly. For example, a core gas turbine engine having a first compression ratio may be coupled to a fan assembly16having a first compression ratio. If the compression ratio of fan assembly is increased, the fan assembly16may be utilized with a core gas turbine engine12having a reduced compression ratio. Alternatively, if the compression ratio of the fan assembly16is reduced, fan assembly16may be utilized with a core gas turbine engine12that includes an increased quantity of stages and thus has an increased compression ratio. In the exemplary embodiment, high-pressure compressor26includes at least six compression stages27. Therefore, fan assembly16may be selectively sized to be coupled to a wide variety of core gas turbine engines. Optionally, a single core gas turbine engine compressor may be modified by either increasing or decreasing the quantity of compression stages, i.e. greater or lesser than six stages, to facilitate coupling the core gas turbine engine to the fan assembly.

Counter-rotating fan assembly16includes a first or forward fan assembly50and a second or an aft fan assembly52configured to rotate about longitudinal axis11. The terms “forward fan” and “aft fan” are used herein to indicate that fan assembly50is coupled axially upstream from fan assembly52. In one embodiment, fan assemblies50and52are positioned at a forward end of core gas turbine engine12, as shown inFIGS. 1-3. In an alternative embodiment, fan assemblies50and52are positioned at an aft end of core gas turbine engine12. Fan assemblies50and52each includes at least one row of rotor blades60and62, respectively, and are positioned within a nacelle64. Rotor blades60are coupled to rotor disk66and rotor blades62are coupled to rotor disk68. In one embodiment, turbine engine assembly10a gooseneck78that extends between and facilitates coupling fan assembly16to core gas turbine engine12. Moreover, gooseneck78includes a structural strut and/or aero strut to facilitate channeling air discharged from aft fan assembly52, through gooseneck78, to core gas turbine engine12. As such, the configuration of gooseneck78and the structural strut facilitate substantially reducing and/or eliminating ice and/or foreign particle ingestion into core gas turbine engine12since core inlet gooseneck substantially “hides” the core gas turbine engine inlet from the main air flowstream that is channeled axially past the exterior surface of gooseneck78in an aftward direction.

As shown inFIG. 1, low-pressure turbine14is coupled to forward fan assembly50through shaft34such that forward fan assembly50rotates in a first rotational direction80. Aft fan assembly52is coupled to drive shaft34and/or low-pressure turbine14such that aft fan assembly52rotates in an opposite second rotational direction82.

FIG. 2is a schematic diagram of a portion of counter-rotating fan assembly16shown inFIG. 1. In one embodiment, first fan assembly50includes a cone84positioned about longitudinal axis11. Cone84is connected at a first or forward end86to rotor disk66and at a second or aft end88to drive shaft34, as shown inFIG. 2. Second fan assembly52includes a cone90positioned coaxially about at least a portion of cone84along longitudinal axis11. Cone90is coupled at a first or forward end92to rotor disk68and at a second or aft end94to an output of a gearbox100and/or to aft end88of cone84via a rolling bearing assembly, as described in greater detailed below.

FIG. 3is a schematic diagram of a portion of the counter-rotating fan assembly16shown inFIG. 2. In one embodiment, counter-rotating fan assembly16also includes a gearbox100that is coupled between aft fan assembly52and drive shaft34to facilitate rotating aft fan assembly52in opposite rotational direction82with respect to rotational direction80in which forward fan assembly50rotates. Gearbox100has a generally toroidal shape and is configured to be positioned circumferentially about drive shaft34to extend substantially about drive shaft34. As shown inFIG. 3, gearbox100includes a support structure102, at least one gear103coupled within support structure102, an input104and an output106.

In one embodiment, gearbox100has a gear ratio of approximately 2.0 to 1 such that forward fan assembly50rotates at a rotational speed that is approximately twice the rotational speed of aft fan assembly52. In another embodiment, forward fan assembly50rotates with a rotational speed that is between approximately 0.67 and approximately 2.1 times faster than the rotational speed of aft fan assembly52. In this embodiment, forward fan assembly50may rotate at a rotational speed greater than, equal to or less than the rotational speed of aft fan assembly52.

In one embodiment, a first bearing assembly, such as thrust bearing assembly110as shown inFIGS. 1-3, is positioned about drive shaft34and/or longitudinal axis11. Thrust bearing assembly110operatively couples and/or is mounted between drive shaft34and frame13of core gas turbine engine12. Referring further toFIG. 3, in one embodiment, thrust bearing assembly110includes a radially positioned inner race111that is mounted with respect to drive shaft34. As shown inFIG. 3, inner race111is mounted to a drive shaft extension112operatively coupled to drive shaft34so that inner race111is rotatable about longitudinal axis11with drive shaft34. In one particular embodiment, drive shaft extension112is splined to drive shaft34. Inner race111has a surface113defining an inner groove114of thrust bearing assembly110. Surface113defining inner groove114has a generally arcuate profile.

Thrust bearing assembly110includes a radially positioned outer race116securely coupled to frame13. In one embodiment, outer race116and/or frame13acts as a ground for the transfer of thrust loads and/or forces developed or generated by counter-rotating fan assembly16, as discussed in greater detail below. Outer race116has a surface117, generally opposing surface113, which forms an outer groove118of thrust bearing assembly110. Surface117defining outer groove118has a generally arcuate profile. At least one roller element, such as a plurality of bearings119, is movably positioned between inner race111and outer race116. Each bearing119is in rolling contact with inner groove114and outer groove118to allow drive shaft34to rotate freely with respect to gearbox100.

Referring toFIG. 4, a second bearing assembly, such as thrust bearing assembly120, is positioned radially about longitudinal axis11. In one embodiment, thrust bearing assembly120operatively couples and/or is mounted between a forward end portion of first fan assembly50, such as at or near forward end86of cone84, and a forward end portion of second fan assembly52, such as at or near forward end92of cone90. In one embodiment, thrust bearing assembly120includes a radially positioned inner race122that is mounted with respect to an outer surface of cone84. As shown inFIG. 4, inner race122is mounted to cone84so that inner race122is rotatable about longitudinal axis11with first fan assembly50. Inner race122has a surface123defining an inner groove124of thrust bearing assembly110. Surface123defining inner groove124has a generally arcuate profile.

Thrust bearing assembly120includes a radially positioned outer race126that is mounted with respect to an inner surface of cone90. As shown inFIG. 4, inner race122is mounted to cone90so that outer race126is rotatable about longitudinal axis11with second fan assembly52. Outer race126has a surface127, generally opposing surface123, which forms an outer groove128of thrust bearing assembly120. Surface127defining outer groove128has a generally arcuate profile. At least one roller element, such as a plurality of bearings129, is movably positioned between inner race122and outer race126. Each bearing129is in rolling contact with inner groove124and outer groove128to facilitate relative rotational movement of first fan assembly50and/or second fan assembly52.

In one embodiment, thrust bearing assemblies110and/or120facilitate maintaining forward fan assembly50and/or aft fan assembly52in a relatively fixed axial position. During operation of counter-rotating Ian assembly16, thrust loads and/or forces generated by first fan assembly50are transferred directly from first fan assembly50to first thrust bearing assembly110, Further, thrust loads and/or forces generated by second fan assembly52during operation are transferred from second fan assembly52to second thrust bearing assembly120and from second thrust bearing assembly120through drive shaft34to first thrust bearing assembly110. As a result of transferring thrust loads and/or forces to thrust bearing assembly110and/or thrust bearing assembly120, the transfer of thrust loads and/or forces through gearbox100, operatively coupled to second fan assembly52, 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 assembly110and/or bearing assembly120.

In one embodiment, a bearing assembly, such as roller bearing assembly130, is positioned about the outer surface of cone90at or near forward end92, as shown inFIG. 4. Roller bearing assembly130is connected between frame13and forward end92. In one embodiment, roller bearing assembly130acts as a differential bearing assembly in combination with thrust bearing assembly120to support second fan assembly52and/or transfer thrust loads and/or forces from second fan assembly52to frame13. In one embodiment, roller bearing assembly130includes an inner race132that is mounted with respect to cone90, as shown inFIG. 4. Inner race132is mounted to forward end92of cone90so that inner race132is rotatable about longitudinal axis11with second fan assembly52. Inner race132has a surface133defining an inner groove134of roller bearing assembly130.

Roller bearing assembly130includes an outer race136that is securely coupled to frame13. In one embodiment, outer race136is securely coupled with respect to structural support member15and/or frame13. Structural support member15and/or frame13acts as a ground for the transfer of thrust loads and/or forces developed or generated by counter-rotating fan assembly16. Outer race136has a surface137, generally opposing surface133, which forms an outer groove138of roller bearing assembly130. At least one roller element, such as a plurality of rollers139, is movably positioned between inner race132and outer race136. Each roller139is in rolling contact with inner groove134and outer groove138.

In one embodiment, a bearing assembly, such as roller bearing assembly140, is positioned about the outer surface of cone84at or near aft end88, as shown inFIG. 3. Roller bearing assembly140is connected between cone84and cone90. Roller bearing assembly140includes an inner race142that is mounted with respect to aft end88, as shown inFIG. 2. Inner race142is mounted to cone84so that inner race142is rotatable about longitudinal axis11with first fan assembly50. Inner race142has a surface143defining an inner groove144of roller bearing assembly140.

Roller bearing assembly140includes an outer race146that is mounted with respect to aft end94of cone90, as shown inFIG. 3. Outer race146is mounted to cone90so that outer race146is rotatable about longitudinal axis11with second fan assembly52. Outer race146has a surface147, generally opposing surface143, which forms an outer groove148of roller bearing assembly140. At least one roller element, such as a plurality of rollers149, is movably positioned between inner race142and outer race146. Each roller149is in rolling contact with inner groove144and outer groove148to facilitate relative rotational movement of cone84and/or cone90.

In this embodiment, roller bearing assemblies130and140facilitate providing rotational support to aft fan assembly52such that aft fan assembly52can rotate freely with respect to forward fan assembly50. Accordingly, roller bearing assemblies130and140facilitate maintaining aft fan assembly52in a relatively fixed radial position within counter-rotating fan assembly16. 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 assembly130and/or bearing assembly140.

In one embodiment, gearbox100is connected to a fixed or stationary component of gas turbine engine10, such as frame13of core turbine engine12, as shown inFIG. 3. Gearbox input104is rotatably coupled to second drive shaft34through drive shaft extension112that is splined to drive shaft34. Gearbox output106is rotatably coupled to aft fan assembly52through an output structure160. A first end of output structure160is splined to gearbox output106and˜a second end of output structure160is coupled to aft fan forward shaft168to facilitate driving aft fan assembly52.

Referring toFIG. 3, in one embodiment, gas turbine engine assembly10includes a spline system200for mounting gearbox100to counter-rotating fan assembly16. Gearbox100is fixedly or securely coupled to frame13of core gas turbine engine12, for example at gearbox support structure102. Spline system200isolates gearbox100from first fan assembly50and/or second fan assembly52to prevent or limit thrust loads and/or forces exerted on gearbox100as a result of counter-rotating fan assembly16operation. First fan assembly50is rotatably coupled to input104such that first fan assembly50rotates in a first direction, as indicated by rotational arrow80inFIG. 1. Second fan assembly52is rotatably coupled to output106such that second fan assembly52rotates in a second direction, as indicated by rotational arrow82inFIG. 1, opposite the first direction.

As shown inFIG. 3, spline system200includes a plurality of spline assemblies, such as spline assembly202,204,206and/or208. In one embodiment, a first spline assembly202couples input104to drive shaft extension112. Drive shaft extension112includes a first portion210and a second portion212, as shown inFIG. 3. First spline assembly202couples input104to first portion10and a second spline assembly204, the same or similar to first spline assembly202, couples first portion210to second portion212to rotatably couple input104to drive shaft34. Further, second spline assembly204facilitates movement of thrust bearing assembly110with respect to gearbox100in the axial direction, i.e., along or parallel with longitudinal axis11of turbine engine assembly10.

In one embodiment, spline assembly204includes a member forming a plurality of splines positioned about a periphery of the member. The member, connected to second portion212of drive shaft extension112, is positionable within a cavity formed in a cooperating housing, connected to first portion210, such that the plurality of splines mesh or interfere with slots formed on an inner periphery of the housing to transfer torsional loads and/or forces from second portion212to first portion210of drive shaft extension112. Further, the member is positioned within the cooperating housing to facilitate movement of the member within the housing in an axial direction, e.g., along or parallel with longitudinal axis11, which facilitates axial movement of second portion212with respect to first portion210.

In one particular embodiment, each spline assembly204,206and208are the same or similar, as described above with reference to spline assembly204. A third spline assembly206slidably couples output106to output structure160. Third spline assembly206facilitates axial movement of aft fan forward shaft168with respect to gearbox100. In one embodiment, a fourth spline assembly208slidably couples second portion212of drive shaft extension112to drive shaft34. During operation, spline assemblies202,204,206and/or208pass only torsional or torque loads and/or forces to gearbox100such that gearbox100remains in a substantially fixed position with respect to the frame of low-pressure turbine14.

In one embodiment, drive shaft extension112and/or output structure160include at least one flexible arm compensating for a radial deflection of gearbox100. In a particular embodiment, first portion210includes a radially inner portion230that is coupled to input104through spline assembly202and a radially outer portion232that is coupled to second portion212through spline assembly204. First portion210has a first thickness at or near inner portion230and a second thickness at or near outer portion232, which is less than first thickness240. In this particular embodiment, a thickness of first portion210gradually decreases from radially inner portion230to radially outer portion232. The second thickness is selected such that first portion230will separate from second portion232, i.e. first portion210will break, when first portion210is subjected to a determined torsional load and/or force. During operation of engine assembly10, relatively large radial loads and/or forces may be applied to aft fan assembly52. To compensate for the relatively large radial loads and/or forces, and to ensure continued engine operation, in one embodiment first portion210breaks such that forward fan assembly50continues to operate as aft fan assembly52freewheels.

During operation, as second drive shaft34rotates, second drive shaft34causes input104to rotate in first rotational direction80, which subsequently rotates output106in opposite second rotational direction82. Because output structure160is coupled to aft fan assembly52, drive shaft34causes aft fan assembly52to rotate via gearbox100in opposite second direction82. In one embodiment, gearbox100is located within a sump170at least partially defined between output structure160and structural support member15configured to support aft fan assembly52. During operation, gearbox100is at least partially submerged within lubrication fluid contained in sump170to continuously lubricate gearbox100during engine operation.

The gas turbine engine assembly described herein includes a counter-rotating fan assembly having a geared single rotation low-pressure turbine. The assembly facilitates reducing at least some of the complexities associated with known counter-rotating low-pressure turbines. More specifically, the gas turbine engine assembly described herein includes a front fan that is rotatably coupled to a single rotation low-pressure turbine, and an aft fan that is rotatably coupled together, and driven by, the low-pressure turbine via a gearbox. Moreover, the aft fan assembly is driven at the same speed, which, in one embodiment, is approximately one-half the front fan speed. Additionally, the gas turbine engine assembly described herein is configured such that approximately 30% of power generated by the low-pressure turbine is transmitted through the gearbox to the aft fan assembly to facilitate reducing gear losses. Therefore, in the event of a gearbox failure, the aft Ian assembly will cease to rotate. However, the front fan assembly will continue to rotate because the front Ian assembly is directly driven by the low-pressure turbine.

Additionally, the above-described gas turbine engine does not include a booster compressor. As a result, eliminating the booster compressor results in a simpler, lower cost, and lower weight engine than at least one known counter-rotating engine.

More specifically, the booster can be eliminated because a high-pressure ratio core is used in conjunction with the increased core stream pressure ratio that can be obtained with the two counter rotating fans. The systems described herein facilitate reducing the size of the gear and gear losses since the gear horsepower may be reduced by approximately 25%, i.e. from approximately 40% to approximately 30%, the speed ratio between the two counter-rotating fans is optimized for performance since no booster stage count issues exists, the interaction loss between the high-pressure turbine (HPT) and the low-pressure turbine (LPT) is substantially eliminated thus resulting in approximately 0.8% increase in LPT efficiency, the two-stage HPT is approximately 3% more efficient than the known single stage HPT thus increasing overall pressure ratio for additional thermodynamic improvements. Moreover, the LPT shaft horsepower and torque are reduced by approximately 10%, which will result in a smaller shaft, and allowing smaller HPT disk bores which will increase parts life by lowering stress and lowering weight. Additionally, no variable bleed valves (VBV) bleed doors are utilized, and ice and foreign particle ingestion is substantially eliminated because the booster-less engine will allow the core inlet gooseneck to be hidden.

Further, the two-stage HPT facilitates increasing the capability of power extraction off the HP spool. The LPT power requirements (Aero Dynamic Loading) are reduced by about 10% resulting in either an improvement in efficiency and/or reduced weight, a simpler thrust reverser design can be utilized, additional space tinder the core cowl may he available to locate the accessory gearbox and larger multiple generators, a shorter fan case, and a simpler, lighter, thinner inlet fan duct.

Exemplary embodiments of a gas turbine engine assembly and methods of assembly the gas turbine engine assembly are described above in detail. The assembly and method arc 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.