WINDAGE SHIELD

Abstract

A windage shield (200, 200) for mounting on a fan disc (100, 100) of a fan (23) of a gas turbine engine (10), the windage shield (200, 200) comprising: a fan disc contacting portion (215, 215) adapted to contact and structurally support a rear portion of the fan disc (100, 100); wherein the fan disc contacting portion (215, 215) includes one or more stiffening elements (205, 205) to locally increase the hoop stiffness of the windage shield (200, 200).

Claims

1. A windage shield for mounting on a fan disc of a fan of a gas turbine engine, the windage shield comprising: a fan disc contacting portion adapted to contact and structurally support a rear portion of the fan disc; wherein the fan disc contacting portion includes one or more stiffening elements to locally increase the hoop stiffness of the windage shield.

2. A windage shield according to claim 1, wherein at least one of the one or more stiffening elements is integral to the fan disc contacting portion.

3. A windage shield according to claim 1, wherein at least one of the one or more stiffening elements is provided as an insert receivable partially or fully on or in the fan disc contacting portion.

4. A windage shield according to claim 1, wherein at least one of the one or more stiffening elements comprises, or consists essentially of, a composite material such as a metal matrix composite or a ceramic matrix composite.

5. A windage shield according to claim 1, wherein at least one of the one or more stiffening elements comprises, or consists essentially of, a metal or alloy such as nickel alloy, titanium, a titanium alloy, aluminium or an aluminium alloy.

6. A fan for a gas turbine engine, the fan comprising: a fan disc; and at least one windage shield according to claim 1 mounted on the fan disc.

7. A fan according to claim 6, wherein the windage shield is mounted on a rear portion of the fan disc.

8. A fan according to claim 7, the fan disc further comprising disc posts for locating a blade mounted on the fan disc, wherein at least one of the one or more stiffening elements is located on the disc posts radially outwardly of the disc posts.

9. A fan according to claim 7, the fan disc comprising a protrusion extending axially rearwardly, wherein at least one of the one or more stiffening elements is disposed on and/or adjacent the protrusion.

10. A gas turbine engine for an aircraft comprising: an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor; and a fan as claimed in claim 6 located upstream of the engine core.

11. A gas turbine engine according to claim 10, further comprising a gearbox that receives an input from the core shaft and outputs drive to the fan so as to drive the fan at a lower rotational speed than the core shaft.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0052] Embodiments will now be described by way of example only, with reference to the Figures, in which:

[0053] FIG. 1 is a sectional side view of a gas turbine engine;

[0054] FIG. 2 is a close up sectional side view of an upstream portion of a gas turbine engine;

[0055] FIG. 3 is a partially cut-away view of a gearbox for a gas turbine engine;

[0056] FIG. 4 is a cross-sectional view of a fan for a gas turbine engine comprising a windage shield;

[0057] FIG. 5 shows a cross-sectional perspective view of an example of a windage shield mounted on a fan disc;

[0058] FIG. 6 is a close up view of the windage shield shown in FIG. 5; and

[0059] FIG. 7 is a close up cross-sectional perspective view of another example of a windage shield mounted on a fan disc.

DETAILED DESCRIPTION

[0060] 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.

[0061] 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.

[0062] 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.

[0063] Note that the terms low pressure turbine and low pressure compressor as used herein may be taken to mean the lowest pressure turbine stages and lowest pressure compressor stages (i.e. not including the fan 23) respectively and/or the turbine and compressor stages that are connected together by the interconnecting shaft 26 with the lowest rotational speed in the engine (i.e. not including the gearbox output shaft that drives the fan 23). In some literature, the low pressure turbine and low pressure compressor referred to herein may alternatively be known as the intermediate pressure turbine and intermediate pressure compressor. Where such alternative nomenclature is used, the fan 23 may be referred to as a first, or lowest pressure, compression stage.

[0064] 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 claimed invention. Practical applications of a planetary epicyclic gearbox 30 generally comprise at least three planet gears 32.

[0065] 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 linkages 36, 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.

[0066] 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 36, 40 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 and support linkages and bearing locations would typically be different to that shown by way of example in FIG. 2.

[0067] 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.

[0068] Optionally, the gearbox may drive additional and/or alternative components (e.g. the intermediate pressure compressor and/or a booster compressor).

[0069] 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.

[0070] 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.

[0071] FIG. 4 shows a conventional arrangement of a windage shield 200 mounted on a fan disc 100 of a gas turbine engine 10. Also shown mounted on the fan disc 100 is a fan blade 105, and an annulus filler 110. The fan disc 100 comprises disc posts 120 which serve to act as a locating mechanism for the fan blade 105 when the fan blade 105 is mounted on the fan disc 100. The windage shield 200 is located adjacent the annulus filler 110 (axially rearwards of the annulus filler 110).

[0072] The windage shield 200 comprises a fan disc contacting portion 215, a shield portion 210 and a lid 220. The windage shield 200 is mounted on the fan disc 100 via the disc posts 120. The fan disc contacting portion 215 of the windage shield 200 is connected to the disc posts 120 using a nut 125 and a bolt 130. A head of the bolt 130 is countersunk into a rear surface of the fan disc contacting portion 215. The shield portion 210 extends radially outwardly from the fan disc contacting portion 215 and axially rearwardly from the fan disc contacting portion 215. The shield portion 210 extends between the fan disc contacting portion 215 and the lid 220. This arrangement is designed to prevent recirculation of air between a region of air beneath each annulus filler 110 and a region of lower pressure air rearwards of each annulus filler 110, which can act to reduce engine efficiency.

[0073] Referring to FIGS. 5 and 6, there is shown an example of a windage shield 200 in accordance with an embodiment of the disclosure mounted on a fan disc 100. The fan disc 100 is connected to a forward facing drive arm 115. Fan discs connected to a forward facing drive arm can have a tendency to roll forwards (i.e., towards the front of the gas turbine engine in which the fan disc is used) due to gas loads on the fan blades in combination with centrifugal loading during rotation of the fan disc. The result of these interacting loads is greater radial displacements and steady state stresses at the rear of the fan disc.

[0074] The windage shield 200 comprises a fan disc contacting portion 215, a shield portion 210 and a lid 220. The windage shield 200 is mounted on the fan disc 100 via the disc posts 120. The fan disc contacting portion 215 of the windage shield 200 is connected to the disc posts 120. Any suitable joining technique or fasteners may be used to connect the fan disc contacting portion 215 to the disc posts 120. The shield portion 210 extends radially outwardly from the fan disc contacting portion 215 and axially rearwardly from the fan disc contacting portion 215. The shield portion 210 extends between the fan disc contacting portion 215 and the lid 220.

[0075] The fan disc contacting portion 215 is adapted to contact and structurally support a rear portion of the fan disc 100. The fan disc contacting portion 215 comprises a stiffening element 205 protruding from an axially forward face of the fan disc contacting portion 215. The stiffening element 205 may extend or protrude a distance axially to provide a required or desired magnitude of structural support to the rear portion of the fan disc 100. The stiffening element 205 is located outboard (i.e., radially outward) of the disc posts 120. The stiffening element 205 may extend a distance radially to provide a required or desired magnitude of structural support to the rear portion of the fan disc 100. The stiffening element 205 is located on (i.e., is in contact with) an upper surface 135 of at least one of the disc posts 120. The stiffening element 205 extends or spans (e.g., in a circumferential direction or arc) a distance across the axially forward face of the fan disc contacting portion 215. For example, the stiffening element 205 may extend or span at least the distance between upper surfaces 135 of adjacent disc posts 120 (as shown in FIG. 5), such that a lower surface of the stiffening element 205 is in contact with at least a portion of the upper surface 135 of each of the adjacent disc posts 120.). The stiffening element 205 may extend in a circumferential direction across the axially forward face of the fan disc contacting portion 215 to form an annular stiffening element 205, e.g. such that a lower surface of the stiffening element 205 is in contact with at least a portion of the upper surface 135 of each disc post 120 on the fan disc 100.

[0076] The stiffening element 205 locally increases the hoop stiffness of the windage shield 200. The windage shield 200 is configured to reduce peak stresses and radial growth experienced by the rear of the fan disc 100. The stiffening element 205 may shield the rear of the fan disc 100 from at least some of the loads typically experienced by the rear of the fan disc 100 during use by carrying at least a portion of those loads. Similarly, by locally increasing the hoop stiffness of the windage shield 200, the windage shield 200 may help to reduce radial displacements experienced by the rear of the fan disc 100.

[0077] The stiffening element 205 may be integral to the fan disc contacting portion 215. The stiffening element 205 may comprise, or consist essentially of, the same material or materials as one or more other portions of the windage shield 200, e.g. the fan disc contacting portion 215, the shield portion 210 and/or the lid 220.

[0078] FIG. 7 shows an example of a windage shield 200 in accordance with another embodiment of the disclosure mounted on a fan disc 100. The fan disc 100 comprises disc posts 120. The fan disc 100 further comprises a protrusion or flange 145 extending axially rearward from the fan disc 100. The protrusion 145 is located radially inward of an axially rearward-facing outer surface of the fan disc 100. The protrusion or flange 145 may be an arc-shaped or annular protrusion extending in a circumferential direction across a rear surface of the fan disc 100.

[0079] The windage shield 200 comprises a fan disc contacting portion 215, a shield portion 210 and a lid (not shown). The windage shield 200 is mounted on the fan disc 100 via the disc posts 120. The fan disc contacting portion 215 of the windage shield 200 is connected to the disc posts 120. Any suitable joining technique or fasteners may be used to connect the fan disc contacting portion 215 to the disc posts 120. The shield portion 210 extends radially outwardly from the fan disc contacting portion 215 and axially rearwardly from the fan disc contacting portion 215. The shield portion 210 extends between the fan disc contacting portion 215 and the lid (not shown).

[0080] The fan disc contacting portion 215 is adapted to contact and structurally support a rear portion of the fan disc 100. The fan disc contacting portion 215 comprises a stiffening element 205 protruding from an axially rearward face of the fan disc contacting portion 215. The stiffening element 205 may extend or protrude a distance axially to provide a required or desired magnitude of structural support to the rear portion of the fan disc 100. The stiffening element 205 is located inboard (i.e., radially inward) of the disc posts 120. The stiffening element 205 may extend a distance radially to provide a required or desired magnitude of structural support to the rear portion of the fan disc 100. The stiffening element 205 is located on (i.e., is in contact with) at least a portion of an upper surface of the protrusion or flange 145. The stiffening element 205 extends or spans (e.g., in a circumferential direction or arc) a distance across at least a portion of the axially rearward face of the fan disc contacting portion 215. The stiffening element 205 may extend in a circumferential direction across the axially rearward face of the fan disc contacting portion 215 to form an arc-shaped or annular stiffening element 205, e.g. such that a lower or inner surface of the stiffening element 205 is in contact with at least a portion of an upper or outer surface of the protrusion or flange 145.

[0081] The stiffening element 205 locally increases the hoop stiffness of the windage shield 200. The windage shield 200 is configured to reduce peak stresses and radial growth experienced by the rear of the fan disc 100. The stiffening element 205 may shield the rear of the fan disc 100 from at least some of the loads typically experienced by the rear of the fan disc 100 during use by carrying at least a portion of those loads. Similarly, by locally increasing the hoop stiffness of the windage shield 200, the windage shield 200 may help to reduce radial displacements experienced by the rear of the fan disc 100.

[0082] The stiffening element 205 may be integral to the fan disc contacting portion 215. The stiffening element 205 may comprise, or consist essentially of, the same material or materials as one or more other portions of the windage shield 200, e.g. the fan disc contacting portion 215, the shield portion 210 and/or the lid.

[0083] In embodiments, the fan disc contacting portion may comprise any number or arrangement of stiffening elements to locally increase the hoop stiffness of the windage shield.

[0084] One or more of the stiffening elements may be integral to the fan disc contacting portion. One or more of the stiffening elements may be joined or fastened to the fan disc contacting portion. Any suitable joining or fastening means or technique may be employed. One or more of the stiffening elements may be permanently, semi-permanently or releasably joined or fastened to the fan disc contacting portion.

[0085] One or more of the stiffening elements may be provided as an insert receivable at least partially in or on the fan disc contacting portion. The fan disc contacting portion may comprise one or more recesses for receiving, partially or fully, one or more of the stiffening elements.

[0086] The stiffening element(s) may comprise, or consist essentially of, the same material or materials as one or more other portions of the windage shield. Alternatively, the stiffening element(s) may comprise, or consist essentially of, a different material or materials from other portions of the windage shield. The stiffening element(s) may comprise, or consist essentially of, a metal or an alloy, for example titanium, aluminium, a titanium alloy or an aluminium alloy. The stiffening element(s) may comprise, or consist essentially of, a composite material, for example a metal matrix composite material.

[0087] The stiffening elements may be located at a plurality of locations on the fan disc contacting portion to locally increase the hoop stiffness of the windage shield and provide structural support to the rear of the fan disc at the plurality of locations. For example, a windage shield may be provided with a stiffening element in the location as shown in the embodiment of FIGS. 5 and 6 and may also be provided with a stiffening element in the location shown in the embodiment of FIG. 7.

[0088] The windage shield may be mounted to the fan disc in any suitable manner. For example, the windage shield may be mounted to the fan disc by a fastener (e.g., a nut and a bolt, a screw), and/or an adhesive. The windage shield may be mounted to the fan disc via a weld.

[0089] A windage shield according to the present disclosure may be effective for fan discs with a forward facing drive arm, for the reasons discussed above.

[0090] Ordinarily, a windage shield is provided on the rear of a fan disc to reduce or eliminate the effects of windage on engine efficiency. A windage shield according to the present disclosure may perform two roles. The first role is to reduce or eliminate the effects of windage on engine efficiency. The second role is to provide improved load shielding to the rear of the fan disc, e.g. to protect the rear of the fan disc from the greater radial displacements and steady state stresses typically associated with a fan disc connected to a forward facing drive arm. In this way, a proportion of the loads may be borne by the windage shield, rather than by the rear of the fan disc.

[0091] A windage shield in accordance with an embodiment of the disclosure may be effective for fans with a hub to tip ratio of between 0.4 and 0.25, and/or for fans with a fan diameter of greater than 90 inches (2.3 metres).

[0092] It will be understood that the invention is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.