DRIVESHAFT

Abstract

A turbofan engine driveshaft comprises, in axial sequence along an axial centreline, a driving portion, and a driven portion. The driving portion has a first end and a second end. The second end of driving portion is connected to the driven portion. The driven portion comprises an annular drum having a radially inwardly facing surface, with the annular drum having a stiffener attached to the radially inwardly facing surface.

The driveshaft is supported radially by a bearing assembly at the connection between the driving portion and the driven portion. The driving portion is configured to accommodate a predetermined range of movement of the outer end relative to the inner end.

Claims

1. A turbofan engine driveshaft comprising, in axial sequence along an axial centreline, a driving portion having a first end and a second end; and a driven portion, wherein the second end of the driving portion is connected to the driven portion, the driven portion comprises an annular drum having a radially inwardly facing surface, the annular drum having a stiffener attached to the radially inwardly facing surface, the driveshaft being supported radially by a bearing assembly at the connection between the driving portion and the driven portion, the driving portion being configured to accommodate a predetermined range of movement between the first end and the second end of the driving portion.

2. The driveshaft as claimed in claim 1, wherein the stiffener comprises a plurality of stiffener portions extending radially inwardly from the radially inwardly facing surface.

3. The driveshaft as claimed in claim 2, wherein the stiffener comprises three diaphragm stiffener portions extending radially inwardly from the radially inwardly facing surface.

4. The driveshaft as claimed in claim 1, wherein the driving portion is separably attached to the driven portion by a first joint assembly.

5. The driveshaft as claimed in claim 4, wherein the first joint assembly is a Curvic coupling.

6. The driveshaft as claimed in claim 1, wherein the driving portion comprises an axially extending cylindrical portion between the first end and the second end, the cylindrical portion providing a predetermined range of radial movement between the first end and the second end of the driving portion.

7. The driveshaft as claimed in claim 6, wherein a radial thickness of the cylindrical portion varies along the axial length of the cylindrical portion.

8. The driveshaft as claimed in claim 1, wherein the driving portion comprises a radially extending diaphragm portion between the first end and the second end, the diaphragm portion providing a predetermined range of axial movement between the first end and the second end of the driving portion.

9. The driveshaft as claimed in claim 8, wherein the diaphragm portion extends from a radially inner end to a radially outer end, and an axial thickness of the diaphragm portion at the radially inner end is greater than the axial thickness at the radially outer end.

10. The driveshaft as claimed in claim 1, wherein the driving portion comprises an axially splined coupling between the first end and the second end, the axially splined coupling providing a predetermined range of axial movement between the first end and the second end of the driving portion.

11. The driveshaft as claimed in claim 1, wherein the bearing assembly is positioned radially outwardly of the connection between the driving portion and the driven portion.

12. A gas turbine engine comprising, in axial sequence: a core engine; a gearbox: a driveshaft as claimed in claim 1; and a fan, wherein an output from the gearbox is operatively connected to the driving portion of the driveshaft, and the driven portion of the gearbox is operatively connected to the fan.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0056] There now follows a description of an embodiment of the disclosure, by way of non-limiting example, with reference being made to the accompanying drawings in which:

[0057] FIG. 1 shows a schematic sectional view of a geared turbofan gas turbine engine incorporating a driveshaft according to the present disclosure;

[0058] FIG. 2 shows an enlarged schematic view of the gearbox region of the engine of FIG. 1;

[0059] FIG. 3 shows a schematic axial view of the gearbox of the engine of FIG. 1;

[0060] FIG. 4 is a schematic part-sectional view of the engine of FIG. 1 showing a first embodiment of the driveshaft;

[0061] FIG. 5 is a schematic part-sectional view of the engine of FIG. 1 showing a second embodiment of the driveshaft; and

[0062] FIG. 6 is a schematic part-sectional view of the engine of FIG. 1 showing a third embodiment of the driveshaft.

[0063] It is noted that the drawings may not be to scale. The drawings are intended to depict only typical aspects of the disclosure, and therefore should not be considered as limiting the scope of the disclosure. In the drawings, like numbering represents like elements between the drawings.

DETAILED DESCRIPTION

[0064] FIG. 1 illustrates a gas turbine engine 10 having a principal rotational axis 9. The engine 10 comprises an air intake 12 and a propulsive fan 23 that generates two airflows: a core airflow A and a bypass airflow B. The gas turbine engine 10 comprises a core 11 that receives the core airflow A. The engine core 11 comprises, in axial flow series, a low pressure compressor 14, a high-pressure compressor 15, combustion equipment 16, a high-pressure turbine 17, a low pressure turbine 19 and a core exhaust nozzle 20. A nacelle 21 surrounds the gas turbine engine 10 and defines a bypass duct 22 and a bypass exhaust nozzle 18. The bypass airflow B flows through the bypass duct 22. The fan 23 is attached to and driven by the low pressure turbine 19 via a shaft 26 and an epicyclic gearbox 30.

[0065] In use, the core airflow A is accelerated and compressed by the low pressure compressor 14 and directed into the high pressure compressor 15 where further compression takes place. The compressed air exhausted from the high pressure compressor 15 is directed into the combustion equipment 16 where it is mixed with fuel and the mixture is combusted. The resultant hot combustion products then expand through, and thereby drive, the high pressure and low pressure turbines 17, 19 before being exhausted through the nozzle 20 to provide some propulsive thrust. The high pressure turbine 17 drives the high pressure compressor 15 by a suitable interconnecting shaft 27. The fan 23 generally provides the majority of the propulsive thrust. The epicyclic gearbox 30 is a reduction gearbox.

[0066] An exemplary arrangement for a geared fan gas turbine engine 10 is shown in FIG. 2. The low pressure turbine 19 (see FIG. 1) drives the shaft 26, which is coupled to a sun wheel, or sun gear, 28 of the epicyclic gear arrangement 30. Radially outwardly of the sun gear 28 and intermeshing therewith is a plurality of planet gears 32 that are coupled together by a planet carrier 34. The planet carrier 34 constrains the planet gears 32 to precess around the sun gear 28 in synchronicity whilst enabling each planet gear 32 to rotate about its own axis. The planet carrier 34 is coupled via linkages 36 to the fan 23 in order to drive its rotation about the engine axis 9. Radially outwardly of the planet gears 32 and intermeshing therewith is an annulus or ring gear 38 that is coupled, via linkages 40, to a stationary supporting structure 24.

[0067] The epicyclic gearbox 30 is shown by way of example in greater detail in FIG. 3. Each of the sun gear 28, planet gears 32 and ring gear 38 comprise teeth about their periphery to intermesh with the other gears. However, for clarity only exemplary portions of the teeth are illustrated in FIG. 3. There are four planet gears 32 illustrated, although it will be apparent to the skilled reader that more or fewer planet gears 32 may be provided within the scope of the present disclosure. Practical applications of a planetary epicyclic gearbox 30 generally comprise at least three planet gears 32.

[0068] The epicyclic gearbox 30 illustrated by way of example in FIGS. 2 and 3 is of the planetary type, in that the planet carrier 34 is coupled to an output shaft via driveshaft 100:200:300, with the ring gear 38 fixed. However, any other suitable type of epicyclic gearbox 30 may be used. By way of further example, the epicyclic gearbox 30 may be a star arrangement, in which the planet carrier 34 is held fixed, with the ring (or annulus) gear 38 allowed to rotate. In such an arrangement the fan 23 is driven by the ring gear 38. By way of further alternative example, the gearbox 30 may be a differential gearbox in which the ring gear 38 and the planet carrier 34 are both allowed to rotate.

[0069] It will be appreciated that the arrangement shown in FIGS. 2 and 3 is by way of example only, and various alternatives are within the scope of the present disclosure. Purely by way of example, any suitable arrangement may be used for locating the gearbox 30 in the engine 10 and/or for connecting the gearbox 30 to the engine 10. By way of further example, the connections (such as the linkages 40, and the driveshaft 100:200:300 in the FIG. 2 example) between the gearbox 30 and other parts of the engine 10 (such as the input shaft 26, the output shaft and the fixed structure 24) may have any desired degree of stiffness or flexibility. By way of further example, any suitable arrangement of the bearings between rotating and stationary parts of the engine (for example between the input and output shafts from the gearbox and the fixed structures, such as the gearbox casing) may be used, and the disclosure is not limited to the exemplary arrangement of FIG. 2. For example, where the gearbox 30 has a star arrangement (described above), the skilled person would readily understand that the arrangement of output, support linkages, driveshafts, and bearing locations would typically be different to that shown by way of example in FIG. 2.

[0070] Accordingly, the present disclosure extends to a gas turbine engine having any arrangement of gearbox styles (for example star or planetary), support structures, input and output shaft arrangement, and bearing locations.

[0071] Optionally, the gearbox may drive additional and/or alternative components (e.g. the intermediate pressure compressor and/or a booster compressor, propeller (aero or hydro), or electrical generator).

[0072] Other gas turbine engines to which the present disclosure may be applied may have alternative configurations. For example, such engines may have an alternative number of compressors and/or turbines and/or an alternative number of interconnecting shafts. By way of further example, the gas turbine engine shown in FIG. 1 has a split flow nozzle 20, 22 meaning that the flow through the bypass duct 22 has its own nozzle that is separate to and radially outside the core engine nozzle 20. However, this is not limiting, and any aspect of the present disclosure may also apply to engines in which the flow through the bypass duct 22 and the flow through the core 11 are mixed, or combined, before (or upstream of) a single nozzle, which may be referred to as a mixed flow nozzle. One or both nozzles (whether mixed or split flow) may have a fixed or variable area. Whilst the described example relates to a turbofan engine, the disclosure may apply, for example, to any type of gas turbine engine, such as an open rotor (in which the fan stage is not surrounded by a nacelle) or turboprop engine, for example. In some arrangements, the gas turbine engine 10 may not comprise a gearbox 30.

[0073] The geometry of the gas turbine engine 10, and components thereof, is defined by a conventional axis system, comprising an axial direction (which is aligned with the rotational axis 9), a radial direction (in the bottom-to-top direction in FIG. 1), and a circumferential direction (perpendicular to the page in the FIG. 1 view). The axial, radial and circumferential directions are mutually perpendicular.

[0074] Referring to FIG. 4, a turbofan engine driveshaft according to a first embodiment of the disclosure is designated generally by the reference numeral 100.

[0075] The driveshaft 100 has an axis of rotation 102, which is coincident with the principal rotational axis 9 of the turbofan engine 10. The driveshaft 100 comprises, in axial sequence, a driving portion 110 and a driven portion 130.

[0076] The driving portion 110 has a first end 112 and an opposite second end 114. The second end 114 of the driving portion 110 is connected to the driven portion 130 by a first joint assembly 138. In the present embodiment, the first joint assembly 138, between the driving portion 110 and the driven portion 130, takes the form of a Curvic coupling 140. In alternative embodiments the first joint assembly 138 may take the form of an alternative connection such as, for example, a bolted flange, or a tapered joint.

[0077] In still further alternative embodiments, the first joint assembly 138 may be a permanent connection such as, for example, by welding, brazing or the like. In yet still further alternative embodiments, the driving portion 110 and the driven portion 130 may be integrally formed by any suitable method such as, for example, casting, forging, and additive layer manufacturing.

[0078] The driven portion 130 comprises an annular drum 132 having a radially inwardly facing surface 134. The annular drum 132 has a stiffener 135 attached to the radially inwardly facing surface 134.

[0079] In the embodiment of FIG. 4, the stiffener 135 comprises three diaphragm stiffener portions 136 extending radially inwardly from the radially inwardly facing surface 134. In other embodiments of the disclosure, the stiffener 135 may comprise an alternative quantity (such as, for example, 1 or 2 or 4) of diaphragm stiffener portions 136 extending radially inwardly from the radially inwardly facing surface 134. Alternatively, the stiffener 135 may take the form of another stiffening structure such as, for example, a cellular structure that is attached to the radially inwardly facing surface 134.

[0080] The driveshaft 100 is supported radially by a bearing assembly 150. The bearing assembly 150 is positioned axially along the driveshaft at the connection between the driving portion 110 and the driven portion 130. In other words, the bearing assembly 150 is positioned at the first joint assembly 138.

[0081] The driving portion 110 is configured to accommodate a range of movement 116 between the the first end 112 and the second end 114 of the driving portion 110. In other words, the driving portion 110 is configured to allow the first end 112 to move relative to the second end 114.

[0082] In the embodiment of FIG. 4 the driving portion 110 comprises an axially extending cylindrical portion 118. The driving portion 110 is formed with a serpentine cross-sectional profile in which the axially extending cylindrical portion 118 is embodied. In the present embodiment, the axially extending cylindrical portion 118 has a radial thickness 122 (i.e. a thickness in the radial direction) that varies monotonically axially along the cylindrical portion 118. In an alternative embodiment, the radial thickness 122 is constant axially along the cylindrical portion 118.

[0083] In use, the cantilevered geometrical form of the axially extending cylindrical portion 118 allows the first end 112 of the driving portion 110 to move radially relative to the second end 114 of the driving portion 110. This range of radial movement 120 provides for misalignment between the first end 112 and the second end 114 of the driving portion 110. In the arrangement of FIG. 4, the driving portion 110 is operatively connected to the planet carrier of the epicyclic gearbox 30. The driving portion 110 is also connected to a forward, or upstream, end of a fan shaft 160. The fan shaft 160 extends rearwardly (in a downstream direction) and provides support for the fan.

[0084] Referring to FIG. 5, a turbofan engine driveshaft according to a second embodiment of the disclosure is designated generally by the reference numeral 200. Features of the driveshaft 200 which correspond to those of driveshaft 100 have been given corresponding reference numerals for ease of reference.

[0085] The driveshaft 200 comprises, in axial sequence, a driving portion 210 and a driven portion 130. The driving portion 210 has a first end 212 and an opposite second end 214. The driven portion 130 is identical to that described above in relation to the first embodiment.

[0086] As outlined above, the second end 214 of the driving portion 210 is connected to the driven portion 130 by the first joint assembly 138. The variants of the first joint assembly 138 outlined above in relation to the first embodiment apply equally to the second embodiment.

[0087] The driveshaft 200 is supported radially by a bearing assembly 150 as outlined above in relation to the first embodiment.

[0088] The driving portion 210 is configured to accommodate a range of movement 216 between the first end 212 and the second end 214 of the driving portion 210.

[0089] In the embodiment of FIG. 5 the driving portion 210 comprises a radially extending diaphragm 218. The driving portion 210 is formed with a serpentine cross-sectional profile in which the radially extending diaphragm 218 is embodied. In the present embodiment, the radially extending diaphragm 218 has an axial thickness 226 (i.e. a thickness in the radial direction) that varies monotonically radially along the diaphragm 218. In an alternative embodiment, the axial thickness 226 is constant radially along the diaphragm 218.

[0090] In use, the cantilevered geometrical form of the radially extending diaphragm 218 allows the first end 212 of the driving portion 210 to move axially relative to the second end 214 of the driving portion 210. This range of axial movement 220 provides for misalignment between the first end 212 and the second end 214 of the driving portion 210. In the arrangement of FIG. 4, the driving portion 210 is operatively connected to the planet carrier of the epicyclic gearbox 30. The driving portion 210 is also connected to a forward, or upstream, end of a fan shaft 260. The fan shaft 260 extends rearwardly (in a downstream direction) and provides support for the fan.

[0091] Referring to FIG. 6, a turbofan engine driveshaft according to a third embodiment of the disclosure is designated generally by the reference numeral 300. Features of the driveshaft 300 which correspond to those of driveshaft 100 have been given corresponding reference numerals for ease of reference.

[0092] The driveshaft 300 comprises, in axial sequence, a driving portion 310 and a driven portion 130. The driving portion 310 has a first end 312 and an opposite second end 314. The driven portion 130 is identical to that described above in relation to the first embodiment.

[0093] As outlined above, the second end 314 of the driving portion 310 is connected to the driven portion 130 by the first joint assembly 138. The variants of the first joint assembly 138 outlined above in relation to the first embodiment apply equally to the second embodiment.

[0094] The driveshaft 300 is supported radially by a bearing assembly 150 as outlined above in relation to the first embodiment.

[0095] The driving portion 310 is configured to accommodate a range of movement 316 between the first end 312 and the second end 314 of the driving portion 310.

[0096] In the embodiment of FIG. 6 the driving portion 310 comprises an axially splined coupling 318. The axially splined coupling 318 provides for axial movement of the first end 312 relative to the second end 314 of the driving portion 310.

[0097] In use, the axially splined coupling 318 allows the first end 312 of the driving portion 310 to move axially relative to the second end 314 of the driving portion 310. This range of axial movement 30 provides for misalignment between the first end 312 and the second end 314 of the driving portion 310. In the arrangement of FIG. 6, the driving portion 310 is operatively connected to the planet carrier of the epicyclic gearbox 30. The driving portion 310 is also connected to a forward, or upstream, end of a fan shaft 360. The fan shaft 360 extends rearwardly (in a downstream direction) and provides support for the fan.

[0098] Various example embodiments of the invention are described herein. Reference is made to these examples in a non-limiting sense. They are provided to illustrate more broadly applicable aspects of the invention. Various changes may be made to the invention described and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, process act(s) or step(s) to the objective(s), spirit or scope of the present invention. Further, it will be appreciated by those with skill in the art that each of the individual variations described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope of the present inventions. All such modifications are intended to be within the scope of claims associated with this disclosure.

[0099] In addition, where a range of values is provided, it is understood that every intervening value, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the invention.