ROTOR OF A FLUID FLOW MACHINE

Abstract

A turbomachine rotor includes a hub and rotor blades. An imbalance correction device is provided which extends radially inside the hub bottom and includes axially front and rear walls, together with the hub bottom, defining a volume of the imbalance correction device. A mass piece, during normal operation of the rotor, is arranged on the axis of rotation. A filler material at least partially fills the volume and surrounds the mass piece in a radial direction. Radial bores extend in a radial direction from the hub bottom side through the rotor hub to a respectively assigned rotor blade. The radial bores and the filler material are formed and coordinated such that, upon loss of a rotor blade, filler material escapes from the thus exposed radial bore assigned to the lost rotor blade, wherein the mass piece moves on the axis of rotation toward the lost rotor blade.

Claims

1. A rotor for a turbomachine, which rotor has: a rotor hub which has a hub top side and a hub bottom side, a multiplicity of rotor blades which project from the hub top side, wherein the rotor has an axis of rotation, wherein an imbalance correction device which extends radially inside the hub bottom side and which is delimited radially to the outside by said hub bottom side, wherein the imbalance correction device has: an axially front wall and an axially rear wall, which, together with the hub bottom side, define a volume of the imbalance correction device, a mass piece which, during normal operation of the rotor, is arranged on the axis of rotation, a filler material which at least partially fills the volume and which surrounds the mass piece in a radial direction, radial bores which extend in a radial direction from the hub bottom side through the rotor hub to a respectively assigned rotor blade, wherein each radial bore is closed off at its radially outer end by the associated rotor blade, wherein the radial bores and the filler material are formed and coordinated with one another such that, in the event of a loss of a rotor blade, filler material escapes from the thus exposed radial bore assigned to the lost rotor blade, wherein the mass piece moves from its position on the axis of rotation in the direction of the lost rotor blade.

2. The rotor according to claim 1, wherein the imbalance correction device forms tracks for the mass piece, which tracks extend in the volume radially outward from the axis of rotation to the hub bottom side and adjoin at least one radial bore.

3. The rotor according to claim 2, wherein the tracks are defined by radially running structures which are spaced apart in a circumferential direction.

4. The rotor according to claim 3, wherein the radially running structures extend from the hub bottom side in the direction of the axis of rotation.

5. The rotor according to claim 2, wherein the tracks have been milled into a base material of the imbalance correction device.

6. The rotor according to claim 1, wherein the imbalance correction device has valve flaps which divide the volume into regions, wherein the valve flaps are each formed so as to prevent filler material of a region from being able to escape from the region in question counter to the radial direction.

7. The rotor according to claim 6, wherein the valve flaps are arranged such that, in the event of loss of a rotor blade, all of the tracks close aside from the track that adjoins the radial bore through which filler material escapes after loss of the rotor blade.

8. The rotor according to claim 6, wherein the valve flaps are each formed by two inner walls which extend substantially in a circumferential direction and, in so doing, are arranged at an angle with respect to one another.

9. the rotor according to claim 6, wherein the imbalance correction device has multiple concentric arrangements of inner walls.

10. The rotor according to claim 1, wherein the mass piece is of cylindrical form or formed as a ball.

11. The rotor according to claim 1, wherein the mass piece is formed from a metal.

12. The rotor according to claim 1, wherein the filler material is formed by a flowable powder or bulk material.

13. The rotor according to claim 1, wherein the filler material is formed by glass beads with a mean grain size in the range between 0.01 mm and 0.1 mm, in particular in the range between 0.04 mm and 0.06 mm.

14. The rotor according to claim 1, wherein the filler material is a liquid or a gas.

15. The rotor according to claim 1, wherein the radial bores are formed such that they end in the respective rotor blade at a radial distance from the hub top side.

16. The rotor according to claim 1, wherein a multiplicity of imbalance correction devices, which are arranged one behind the other in an axial direction in the rotor, with respectively assigned radial bores, wherein the radial bores of the individual imbalance correction devices extend into the rotor blades in a radial direction to different extents.

17. The rotor according to claim 1, wherein the rotor is a fan, and the rotor blades are fan blades.

18. The rotor according to claim 1, wherein the rotor blades and the rotor hub are formed as a single piece.

19. A gas turbine engine having a rotor according to claim 1.

20. A gas turbine engine according to claim 19, said gas turbine engine having: an engine core which comprises a turbine, a compressor and a core shaft connecting the turbine to the compressor and formed as a hollow shaft; a fan which is positioned upstream of the engine core, wherein the fan comprises a plurality of fan blades and is designed; and a gearbox that receives an input from the turbine shaft and outputs drive for the fan so as to drive the fan at a lower rotational speed than the turbine shaft.

Description

[0073] The invention will be explained in more detail hereunder by means of a plurality of exemplary embodiments with reference to the figures of the drawing. In the drawing:

[0074] FIG. 1 shows a sectional lateral view of a gas turbine engine;

[0075] FIG. 2 shows a close-up sectional lateral view of an upstream portion of a gas turbine engine;

[0076] FIG. 3 shows a partially cut-away view of a gearbox for a gas turbine engine;

[0077] FIG. 4 shows a view from the front of an exemplary embodiment of a fan with a fan hub, fan blades and an imbalance correction device, which is arranged within the fan hub and which has a mass piece which, during normal operation of the fan, is arranged on the axis of rotation;

[0078] FIG. 5 shows the fan of FIG. 4 with an enlarged illustration of the imbalance correction device;

[0079] FIG. 6 shows the fan of FIG. 5 with a perspective illustration of the imbalance correction device, wherein

[0080] FIG. 7 shows the fan with imbalance correction device of FIG. 5, in the case of which the mass piece has been moved from the axis of rotation in the direction of the position of a lost blade;

[0081] FIG. 8 shows a perspective and in this case transparent sectional view of the imbalance correction device of FIGS. 4-7; and

[0082] FIG. 9 shows, in axial section, a fan with an imbalance correction device as per FIGS. 4-8.

[0083] FIG. 1 represents a gas turbine engine 10 having a main axis of rotation 9. The engine 10 comprises an air intake 12 and a thrust fan 23 that generates two airflows: a core airflow A and a bypass airflow B. The gas turbine engine 10 comprises a core 11 which receives the core airflow A. In the sequence of axial flow, the engine core 11 comprises a low-pressure compressor 14, a high-pressure compressor 15, a combustion installation 16, a high-pressure turbine 17, a low-pressure turbine 19, and a core thrust nozzle 20. An engine nacelle 21 surrounds the gas turbine engine 10 and defines a bypass duct 22 and a bypass thrust 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 by way of a shaft 26 and an epicyclic gearbox 30.

[0084] During 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 device 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 thrust force. The high-pressure turbine 17 drives the high-pressure compressor 15 by means of a suitable connecting shaft 27. The fan 23 generally provides the majority of the thrust force. The epicyclic gearbox 30 is a reduction gearbox.

[0085] An exemplary assembly for a gearbox 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 gear 28 of the epicyclic gearbox assembly 30. Radially to the outside of the sun gear 28 and meshing therewith are a plurality of planet gears 32 that are coupled to one another by a planet carrier 34. The planet carrier 34 limits the planet gears 32 to orbiting around the sun gear 28 in a synchronous manner whilst enabling each planet gear 32 to rotate about its own axis. The planet carrier 34 is coupled by way of linkages 36 to the fan 23 so as to drive the rotation of the latter about the engine axis 9. Radially to the outside of the planet gears 32 and meshing therewith is an annulus or ring gear 38 that is coupled, via linkages 40, to a stationary supporting structure 24.

[0086] It is noted that the terms low-pressure turbine and low-pressure compressor as used herein can be taken to mean the lowest pressure turbine stage and the lowest pressure compressor stage (that is to say not including the fan 23) respectively and/or the turbine and compressor stages that are connected to one another by the connecting shaft 26 with the lowest rotational speed in the engine (that is to say not including the gearbox output shaft that drives the fan 23). In some literature, the low-pressure turbine and the low-pressure compressor referred to herein can alternatively be known as the intermediate pressure turbine and intermediate-pressure compressor. Where such alternative nomenclature is used, the fan 23 can be referred to as a first compression stage or lowest-pressure compression stage.

[0087] The epicyclic gearbox 30 is shown in an exemplary manner in greater detail in FIG. 3. Each of the sun gear 28, the planet gears 32 and the ring gear 38 comprise teeth about their periphery to mesh 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 person skilled in the art that more or fewer planet gears 32 can be provided within the scope of protection of the claimed invention. Practical applications of an epicyclic gearbox 30 generally comprise at least three planet gears 32.

[0088] 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, wherein the ring gear 38 is fixed. However, any other suitable type of epicyclic gearbox 30 can be used. By way of further example, the epicyclic gearbox 30 can be a star arrangement, in which the planet carrier 34 is held so as to be fixed, wherein the ring gear (or annulus) 38 is allowed to rotate. In the case of such an arrangement, the fan 23 is driven by the ring gear 38. By way of further alternative example, the gearbox 30 can be a differential gearbox in which the ring gear 38 and the planet carrier 34 are both allowed to rotate.

[0089] It goes without saying that the arrangement shown in FIGS. 2 and 3 is merely an example, and various alternatives fall within the scope of protection of the present disclosure. Purely by way of example, any suitable arrangement can be used for positioning 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 example of FIG. 2) 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) can have a certain 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 of the gearbox and the fixed structures, such as the gearbox casing) can 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 person skilled in the art would readily understand that the arrangement of output and support linkages and bearing positions would typically be different to that shown by way of example in FIG. 2.

[0090] Accordingly, the present disclosure extends to a gas turbine engine having an arbitrary arrangement of gearbox types (for example star-shaped or planetary), support structures, input and output shaft arrangement, and bearing positions.

[0091] Optionally, the gearbox can drive additional and/or alternative components (e.g. the intermediate pressure compressor and/or a booster compressor).

[0092] Other gas turbine engines to which the present disclosure can be applied can have alternative configurations. For example, engines of this type can have an alternative number of compressors and/or turbines and/or an alternative number of connecting 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 can 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 can be referred to as a mixed flow nozzle. One or both nozzles (whether mixed or split flow) can have a fixed or variable area. Whilst the example described relates to a turbofan engine, the disclosure can be applied, for example, to any type of gas turbine engine, such as, for example, an open rotor engine (in which the fan stage is not surrounded by an engine nacelle) or a turboprop engine. In some arrangements, the gas turbine engine 10 may not comprise a gearbox 30.

[0093] The geometry of the gas turbine engine 10, and components thereof, is/are 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 view in FIG. 1). The axial, radial and circumferential directions are mutually perpendicular.

[0094] In the context of the invention, what is of significance is a design of the fan 23 such that, in the event of the loss of a fan blade, imbalances associated with this should be minimized. The description of the invention on the basis of a fan 23 is in this case merely exemplary. The principles of the invention apply basically to each rotor.

[0095] FIG. 4 firstly gives an overview of the major components of a fan 23 designed according to the invention. The fan 23 comprises a fan hub 5, which has a hub top side 51 and a hub bottom side 52. A multiplicity of fan blades 230 project from the hub top side 51, which fan blades are arranged equidistantly in the circumferential direction and form a blade ring. The hub top side 51 forms a ring surface, and in so doing delimits the flow duct through the fan 23 radially to the inside.

[0096] The fan 23 is of BLISK design, such that the fan hub 5 and the fan blades 230 are formed as a single piece. The single-piece form may be provided for example by virtue of the fan hub 5 and fan blades 230 being produced integrally, or by virtue of the fan blades 230 being welded to the fan hub 5. An embodiment of BLISK design is however not imperative. Alternatively, the fan blades 23 may each have a blade root, which is fastened with a corresponding recess in the fan hub 5.

[0097] The fan 32 is rotatable about an axis of rotation 9 which runs in the axial direction. This is for example the axis of rotation 9 of FIG. 1.

[0098] Within the fan hub 5, that is to say radially inside the hub bottom side 52, the fan 23 has an imbalance correction device 6. Here, said imbalance correction device is delimited radially to the outside by the hub bottom side 52. The imbalance correction device 6 occupies, within the fan hub 5, a particular volume which is defined by its radial extent from the axis of rotation 9 to the hub bottom side 52 and by an axial extent between an axially front wall and an axially rear wall (as will be discussed in more detail with reference to FIG. 8). The volume occupied by the imbalance correction device 6 is in this case cylindrical or approximately cylindrical.

[0099] In the center of the imbalance correction device 6, that is to say symmetrically with respect to the axis of rotation 9 in the mass distribution of said imbalance correction device, there is arranged a mass piece 8. As will be discussed on the basis of the following FIGS. 5-9, the imbalance correction device 6 is provided and designed to, in the event of the loss of a fan blade 230, cause the mass piece 8 to be moved from its position on the axis of rotation 9 in the direction of the lost fan blade. In FIG. 4, in which a fan blade has been lost in the region X, the mass piece 8 would thus move in the direction of the region X. This is realized using a filler material, which is arranged in the imbalance correction device 6, and by means of radial bores 90, which are formed in the rotor hub 5.

[0100] FIGS. 5-9 show the imbalance correction device 6 in an enlarged illustration, wherein FIG. 5 shows a view from above, FIG. 6 shows a perspective view, FIG. 8 shows a partially sectional perspective and in this case transparent view, and FIG. 9 shows a view in axial section. FIG. 7 illustrates the situation in which, after a loss of a fan blade 230, the mass piece 8 has travelled from its position on the axis of rotation 9 in the direction of the lost fan blade.

[0101] Referring firstly to FIGS. 5 and 6, it can be seen that the volume occupied by the imbalance correction device 6 is structured and forms a multiplicity of tracks 65, along which the mass piece 8 can move in the event of the loss of a fan blade 230. The tracks 65 are defined by radially running structures 66, 67 which are spaced apart in a circumferential direction. Here, first radially running structures 66, which extend from the hub bottom side 52 to a relatively great extent in the direction of the axis of rotation 9, and a second radially running structures 67, which extend from the hub bottom side 52 to a lesser extent in the direction of the axis of rotation 9, alternate with one another.

[0102] The volume occupied by the imbalance correction device 6 is furthermore structured by means of valve flaps 75, which divide the interior of the imbalance correction device into different regions. Each valve flap 75 is formed by two pivotable inner walls 76, 77 which are arranged obliquely with respect to one another. Here, the valve flaps 75 are oriented such that they only open in the outward radial direction, whereas they close in the inward radial direction.

[0103] Here, the inner walls 76, 77 form two substantially concentric arrangements 750, 751 of inner walls, wherein the radially inner concentric arrangement 750 runs approximately in the spacing of the radially inner ends of the first radially running structures 66 and, here, the pivot axes of the inner walls 76, 77 lie against said radially inner ends. The radially outer concentric arrangement 751 runs approximately in the spacing of the radially inner ends of the second radially running structures 67, wherein the pivot axes of the inner walls 76, 77 lie partially against said radially inner ends and partially laterally against the first radially running structures 66.

[0104] Here, in the exemplary embodiment illustrated, the radially inner concentric arrangement 750 forms four valve flaps 75, and the radially outer concentric arrangement 751 forms eight valve flaps 75. It is however pointed out that these are to be understood merely as an example. It is alternatively possible for only one concentric arrangement or more than two concentric arrangements, which are each formed valve flaps, to be provided. Design embodiments are also possible which make do without the implementation of valve flaps.

[0105] The tracks 65 generated by the structuring of the imbalance correction device 6 end in each case at the hub bottom side 52. Radial bores 90 run in the fan hub 5, which radial bores extend in a radial direction from the hub bottom side 52 to a respectively assigned fan blade 230, wherein each radial bore 90 is closed off at its radially outer end by the associated fan blade 230.

[0106] In the perspective illustration of FIG. 6, it can be seen that the structuring, resulting from the radially extending structures 66, 67 and the valve flaps 75 or the substantially concentric arrangements 750, 751 of inner walls, of the imbalance correction device 6 defines numerous cavities of the imbalance correction device 6. Referring to FIG. 8, it is pointed out here that the imbalance correction device 6 forms an axially front wall 61 and an axially rear wall 62, which, together with the hub bottom side 52, define a volume 60 of the imbalance correction device 6. Said volume firstly contains the stated structures 66, 67, 750, 751, and self-evidently the mass piece 8, and secondly has cavities, where the stated structures are not present.

[0107] In this context, it is pointed out once again that the design of valve flaps 75 and concentric arrangements 750, 751 of inner walls relate to merely one exemplary embodiment, and are optional for the invention.

[0108] All of the cavities of the imbalance correction device 6 are filled with a filler material 7, which is however not illustrated in the perspective illustration of FIG. 6 so as not to conceal the structural elements of the imbalance correction device 6.

[0109] The filler material 7 fills in particular all of the raceways 65 for the mass piece 8, and here, surrounds the mass piece 8 in a radial direction. The filler material 7 thus prevents the mass piece 8 from being able to move out of its position on the axis of rotation 9 during the normal operation of the fan.

[0110] The filler material 7 is formed by a flowable material. This is, in one exemplary embodiment, a flowable powder or bulk material, for example glass beads with a mean grain size in the range between 0.01 mm and 0.1 mm, in particular in the range between 0.04 mm and 0.06 mm. In another exemplary embodiment, the filler material 7 is a liquid.

[0111] In the exemplary embodiment illustrated, the mass piece 8 is of cylindrical form. It is composed for example of a metal, for example of tungsten. In one exemplary embodiment, a cylindrical mass piece 8 formed from tungsten has an axial length in the range between 40 mm and 120 mm and a radial diameter in the range between 50 mm and 100 mm. The mass piece 8 may however basically have a shape which deviates from a cylindrical shape, for example may be formed as a ball.

[0112] During the normal operation of the fan 23, that is to say in the case of intact fan blades 230, the radial bores 90 are closed off radially to the outside by the respectively assigned fan blades 230. This state changes if a loss of a fan blade 230 or a blade breakage occurs. In the region X, in which a fan blade is missing after such a loss, the associated radial bore 90 is then open at its radially outer end. This means that the filler material 7 present in the tracks 65 of the imbalance correction device 6 can escape from the imbalance correction device 6 through said bore 90. This will also occur owing to the imbalance that arises after a blade loss.

[0113] This however means that the massive forces that act on the mass piece 8 owing to the imbalance that arises after the loss of the fan blade can now push said mass piece in the direction of the escaping filler material 7, because the escaping filler material 7 opens up a corresponding volume. Here, the mass piece 8 is automatically pushed into that one of the tracks 65 which ends at the radial bore 90 from which the filler material is escaping after the loss of the fan blade 230.

[0114] In this context, it is pointed out that, in the exemplary embodiment illustrated, each track 65 ends at a multiplicity of radial bores 90, though this is not imperative. Otherwise, the tracks 65 would have to be formed with a small diameter, which in turn would reduce the diameter of the mass piece and thus the mass thereof.

[0115] It is also pointed out that it is not the case that the radially running first and second structures 66, 67, in the region in which they adjoin the hub bottom side 52, would close off the radial bores 90 formed there. As can be seen from the perspective illustration of FIG. 6, the first and second radial running structures 66, 67 rather form material recesses 660, 661, by means of which the adjoining radial bores 90 are exposed to the hub bottom side 520, such that filler material can also escape via these bores in the event of the loss of a fan blade 230.

[0116] By contrast to the illustration in the figures, provision may be made for the radial bores 90 to extend into the fan blades 230 over a certain radial height, and to end for example in internal cavities that the fan blades 230 may have depending on their type of construction. Such an embodiment is associated with the advantage that, even in the event of an only partial breakaway of a fan blade 230, a radial bore 90 is opened at its radially outer end, and filler material 7 can escape.

[0117] A further embodiment provides for several of the imbalance correction devices 6 to be positioned axially one behind the other. Here, the radial bores 90 assigned to the individual imbalance correction devices 6 extend into the blades 230 to different extents. Provision is furthermore made for the individual imbalance correction devices 6 to be equipped with mass pieces 8 of different weight, wherein, in the case of an imbalance correction device in which the assigned radial bores 90 extend into the blades 230 over a relatively great radial length, the mass piece 8 is of correspondingly more lightweight form. If a blade 230 breaks away further to the outside, a more lightweight mass piece 8 is accordingly forced outward.

[0118] FIG. 7 shows the situation in which, after loss of a fan blade in the region X, the mass piece 8 has been moved from its position on the axis of rotation 9, along a track 65 in the direction of the lost fan blade, onto the hub bottom side 52. Owing to this displacement of the mass piece 8, the imbalance generated as a result of the loss of the fan blade is considerably reduced.

[0119] In the sectional illustration of FIG. 9, it can additionally be seen that the hub 5 receives the imbalance correction device 6 only over a part of the axial length of said hub. This axial length is determined by the axial distance between the front wall 61 and the rear wall 62 of the imbalance correction device 6. In this axial portion, the hub bottom side 52 is, in the exemplary embodiment illustrated but not imperatively, of rectilinear form, such that, in the exemplary embodiment illustrated, the imbalance correction device 6 occupies, overall, a cylindrical volume 60.

[0120] In a manner known per se, the hub 5 has further structures. Accordingly, at the axially front end, there are provided fastening means 55 for connection to a nose cone. At the axially rear end, the hub forms a wall region 53, which extends obliquely radially inward and ends in a flange 54, which serves for connecting the fan 23 via fastening means 95 to a drive shaft, for example corresponding with the FIG. 2.

[0121] Further alternative design embodiments provided for the hub 8 to furthermore form a rotor disk, which is formed axially in front of or axially behind the imbalance correction device 6. This is the case in particular in situations in which the imbalance correction device is formed not in the hub of a fan but rather in the hub of some other rotor, for example of a rotor of a compressor stator of a turbine stage.

[0122] It is pointed out that air holes (not illustrated) may be formed in the axially front wall 61 and/or in the axially rear wall 62, which air holes ensure that, in the event of the breakage of a fan blade, the escape of the filler material 7 is not impaired by a negative pressure in the imbalance correction device 6. Such air holes are for example formed such that filler material cannot pass through them. This may be achieved for example by means of the size of said air holes, and/or valves.

[0123] It goes without saying that the invention is not limited to the above-described embodiments, and various modifications and improvements can be made without departing from the concepts described herein. For example, provision may be made whereby the tracks formed in the imbalance correction device for the mass piece are provided in some other form and/or by means of other structures.

[0124] It is furthermore pointed out that any of the features described can be used separately or in combination with any other features, unless they are mutually exclusive. The disclosure also extends to and comprises all combinations and sub-combinations of one or a plurality of features which are described here. If ranges are defined, said ranges thus comprise all of the values within said ranges as well as all of the partial ranges that lie in a range.