Abstract
A crankshaft assembly for a gas turbine engine guide vane actuator. Example embodiments include a crankshaft assembly for a gas turbine engine guide vane actuator, the crankshaft assembly comprising: a crankshaft mounted for rotation about a central axis; a lug mounted to the crankshaft for rotation with the crankshaft about the central axis, the lug having a first end with a crankshaft connection securing the lug to the crankshaft and a second opposing end for connecting the lug to a control rod such that rotation of the crankshaft causes actuation of the control rod in a direction orthogonal to the central axis, wherein the crankshaft connection is adjustable to allow the first end of the lug to be secured relative to the crankshaft over a range of rotational positions about the central axis.
Claims
1. A crankshaft assembly for a gas turbine engine guide vane actuator, the crankshaft assembly comprising: a crankshaft mounted for rotation about a central axis; a lug mounted to the crankshaft for rotation with the crankshaft about the central axis, the lug having a first end with a crankshaft connection securing the lug to the crankshaft and a second opposing end for connecting the lug to a control rod such that rotation of the crankshaft causes actuation of the control rod in a direction orthogonal to the central axis, wherein the crankshaft connection is adjustable to allow the first end of the lug to be secured relative to the crankshaft over a range of rotational positions about the central axis.
2. The crankshaft assembly of claim 1 wherein the crankshaft connection comprises interlocking teeth on the crankshaft and the lug.
3. The crankshaft assembly of claim 2 wherein the teeth on the lug are biased into contact with the teeth on the crankshaft.
4. The crankshaft assembly of claim 3 wherein the teeth on the lug are configured to separate from contact with the teeth on the crankshaft to allow the crankshaft to rotate relative to the lug.
5. The crankshaft assembly of claim 4 comprising an adjustment element comprising the teeth on the lug, the adjustment element connected to the lug by first and second pivot points and comprising first and second arms extending from opposing sides of the lug, wherein actuation of the first or second arms causes the adjustment element to pivot about the respective second or first pivot points to separate the interlocking teeth from each other.
6. The crankshaft assembly of claim 5 comprising first and second end stops arranged to contact the first and second arms respectively upon rotation of the crankshaft beyond an angular rotation limit to cause the interlocking teeth to separate from each other.
7. The crankshaft assembly of claim 4 comprising an actuator connected to the teeth on the lug and configured upon actuation to separate the teeth on the lug from the teeth on the crankshaft to allow rotation of the crankshaft relative to the lug.
8. The crankshaft assembly of claim 2 wherein the lug comprises a worm gear, rotation of the worm gear causing rotation of the crankshaft relative to the lug.
9. The crankshaft assembly of claim 1 comprising a releasable clamping element between the lug and the crankshaft.
10. A guide vane actuator assembly for a gas turbine engine, comprising: a hydraulic actuator connected for actuating a first control rod; a crankshaft assembly according claim 1, the crankshaft assembly comprising an actuator lug pivotally connected to the first control rod; a second control rod pivotally connected between the second end of the lug and a guide vane actuator ring, the guide vane actuator ring connected to a series of actuator levers connected to ends of a corresponding series of pivotally mounted guide vanes.
11. 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; a fan located upstream of the engine core, the fan comprising a plurality of fan blades; a guide vane assembly located downstream of the fan, the guide vane assembly comprising a guide vane actuator assembly according to claim 9.
12. The gas turbine engine according to claim 11 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.
13. The gas turbine engine according to claim 12, wherein: the turbine is a first turbine, the compressor is a first compressor, and the core shaft is a first core shaft; the engine core further comprises a second turbine, a second compressor, and a second core shaft connecting the second turbine to the second compressor; and the second turbine, second compressor, and second core shaft are arranged to rotate at a higher rotational speed than the first core shaft.
Description
[0053] Embodiments will now be described by way of example only, with reference to the accompanying drawings, in which:
[0054] FIG. 1 is a sectional side view of a gas turbine engine;
[0055] FIG. 2 is a close up sectional side view of an upstream portion of a gas turbine engine;
[0056] FIG. 3 is a partially cut-away view of a gearbox for a gas turbine engine;
[0057] FIG. 4 is a schematic side view of a guide vane actuator assembly comprising a conventional crankshaft assembly;
[0058] FIG. 5A is a schematic plan view of a unison ring and an associated guide vane actuator levers with the levers in a central position;
[0059] FIG. 5B is a schematic plan view of the arrangement of FIG. 5A with the guide vane actuator levers actuated clockwise by rotation of the unison ring;
[0060] FIG. 6A is a schematic sectional diagram of an example crankshaft and control rod assembly for a conventional guide vane actuator with a first length of control rod;
[0061] FIG. 6B is a schematic sectional diagram of the arrangement of FIG. 6A with a longer length of control rod;
[0062] FIG. 7A is a schematic sectional diagram of an example crankshaft and control rod assembly according to the present disclosure;
[0063] FIG. 7B is a schematic sectional diagram of the arrangement of FIG. 7A with an altered position of the pivot connection;
[0064] FIG. 8 is a schematic sectional diagram of an example crankshaft assembly;
[0065] FIG. 9A is a schematic sectional diagram of the crankshaft assembly of FIG. 8 operating in normal mode with the crankshaft rotated clockwise to the second angular limit;
[0066] FIG. 9B is a schematic sectional diagram of the arrangement of FIG. 9A with the crankshaft assembly in a central position;
[0067] FIG. 9C is a schematic sectional diagram of the arrangement of FIG. 9A with the crankshaft assembly rotated anticlockwise to the first angular limit;
[0068] FIG. 10A is a schematic sectional diagram of the crankshaft assembly of FIG. 8 operating to adjust a rotation of the crankshaft relative to the lug with the crankshaft rotated beyond the first angular limit;
[0069] FIG. 10B is a schematic sectional diagram of the arrangement of FIG. 10A with the relative rotation of the crankshaft and lug being offset from each other;
[0070] FIG. 10C is a schematic sectional diagram of the arrangement of FIG. 10A with the position of the lug being offset relative to FIG. 10B;
[0071] FIG. 11 is a schematic sectional diagram of an alternative crankshaft assembly;
[0072] FIG. 12 is a schematic sectional diagram of a further alternative crankshaft assembly; and
[0073] FIG. 13 is a schematic sectional diagram of a further alternative crankshaft assembly.
[0074] 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.
[0075] 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.
[0076] 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.
[0077] 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.
[0078] 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.
[0079] 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.
[0080] 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.
[0081] 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.
[0082] 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.
[0083] Optionally, the gearbox may drive additional and/or alternative components (e.g. the intermediate pressure compressor and/or a booster compressor).
[0084] 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.
[0085] 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.
[0086] FIG. 4 illustrates schematically an example guide vane actuator assembly 400. A hydraulic actuator 401, which is typically fed with aircraft engine fuel as hydraulic fluid (and may therefore be termed a fueldraulic actuator), actuates a first control rod 402 in the direction indicated by arrow 403. A first pivot connection 404 connects the first control rod 402 to a first actuator lug 405 on a rotatably mounted crankshaft 406. Actuation of the first control rod 402 causes the crankshaft 406 to rotate in the direction indicated by arrow 407. A second control rod 408 is connected by a second pivot connection 409 to a second lug 410 extending from the crankshaft 406. Rotation of the crankshaft 406 causes the second lug 410 to rotate and actuate the second control rod 408 in the direction indicated by arrow 411. The second control rod 408 is connected at an opposing end to a guide vane actuation ring 412, commonly known as a unison ring. The unison ring 412 extends around a part of the outer housing of the engine containing the guide vanes, which are located downstream of the fan blades. Rotation of the unison ring 412 by actuation of the second control rod 408 in the direction indicated by arrow 413 causes levers connected to each of a series of guide vanes to rotate, causing the guide vanes to actuate in unison. This is illustrated schematically in FIGS. 5a and 5b, which shows a section of the unison ring 412 and associated levers 501, each of which is connected to the tip 502 of a pivotally mounted guide vane. FIG. 5a shows the levers 501 in a central position, and FIG. 5b shows the levers 501 actuated clockwise by rotation of the unison ring 412.
[0087] The above described mechanism allows for rotation of the guide vanes by a few degrees, typically around +/5 degrees about a central position. More than one set of guide vanes may be actuated by a common crankshaft via separately connected lugs and control rods, allowing multiple unison rings to be actuated with a single fueldraulic actuator.
[0088] A problem with such conventional guide vane actuator assemblies is that, once installed, the range of actuation provided for each set of guide vanes is fixed. During engine development programmes in particular, this can be an issue because the range of actuation may need to be adjusted, either for all sets of guide vanes or for each set separately. With the type of guide vane actuator assembly described above, this is typically achieved by adjusting the length of either the first control rod 402 (which affects all sets of actuated guide vanes) or the second control rod 408 (which affects each set separately). Replacing control rods, however, requires removal, adjustment and replacement of the control rods, which requires extensive disassembly of the engine, involving a long period of downtime for the engine for even a small adjustment. An alternative route may involve replacement of the crankshaft 406 and lugs 405, 410 to reposition the lugs 405, 410 relative to each other. Again, this requires extensive disassembly and downtime, along with manufacture of a new crankshaft.
[0089] FIGS. 6a and 6b illustrate schematically the effect of altering the length of a control rod 601 attached to a lug 602 on a crankshaft 603, with FIG. 6a showing a first length of control rod 601 and FIG. 6b with a longer control rod 601. Changing the control rod 601 length allows the position of the pivot connection 604 to the unison ring to be altered with the crankshaft in the same position, thereby providing an offset to the unison ring position, and thereby to the position of the guide vanes.
[0090] FIGS. 7a and 7b illustrate an alternative way of providing an offset to the position of the pivot connection 604. The crankshaft 603, lug 602 and control rod 601 in FIG. 7a are in the same relative positions as in FIG. 6a. In FIG. 7b, however, the position of the pivot connection 604 is altered not by changing the length of the control rod 601 but instead by adjusting the relative rotational position of the lug 602 and crankshaft 603. In this way a range of offset positions can be provided to the pivot connection 604 without replacing the control rod 601. There are various ways of achieving this change in rotational position, some examples of which are detailed in the following described embodiments, all of which may be incorporated in a guide vane actuator assembly of the type described above.
[0091] FIG. 8 illustrates an example crankshaft assembly 800 comprising a crankshaft 801 with a lug 802 mounted for rotation about a central axis 811 with the crankshaft 801, the lug 802 having a first end 803 with a crankshaft connection 820 securing the lug 802 to the crankshaft 801. In this example, the crankshaft connection 820 comprises interlocking teeth 804a, 804b on the crankshaft 801 and the lug 802. The interlocking teeth 804b on the lug 802 are biased against the teeth 804a on the crankshaft 801 by biasing element such as springs 806 that maintain a force to keep the teeth 804a, 804b interlocked. The teeth 804b form part of an adjustment element 809 that is mounted to a second end 805 of the lug 802. The adjustment element 809 is connected to the crankshaft by first and second pivot points 807a, 807b and comprises first and second arms 808a, 808b. Actuation of the first or second arms 808a, 808b causes the adjustment element 809 to pivot about the respective second or first pivot points 807b, 807a to separate the interlocking teeth 804a, 804b from each other. Actuation of the arms 808a, 808b may for example be achieved by forcing the second end 805 of the lug 802 against an end stop, which is illustrated further in FIG. 10. Under normal operation, i.e. with the arms 808a, 808b not actuated, the crankshaft 801 and lug 802 operate together such that rotation of the crankshaft 801 causes corresponding rotation of the lug 802.
[0092] Normal operation of the crankshaft 801 and lug 802 is illustrated in FIG. 9. In FIG. 9b the crankshaft 801 is in a central position, with a maximum range of rotation indicated by first and second angular limits 901, 902. FIG. 9a illustrates the crankshaft 801 rotated clockwise to the second angular limit 902, while FIG. 9c illustrates the crankshaft 801 rotated anticlockwise to the first angular limit 901. This range corresponds to the normal operational range for actuating a unison ring to cause a set of guide vanes to actuate over a desire range of rotation, which may for example be typically +/5 degrees. Reference points 903, 904 on the lug and crankshaft respectively indicate that the relative rotational position of the lug and crankshaft stays constant.
[0093] FIG. 10 illustrates a process of adjusting the relative position of the lug 802 and crankshaft 801 by forcing the adjustment element 809 against an end stop. In FIG. 10a, the crankshaft 801 is rotated beyond the first angular limit 901, causing the second arm 808b to contact an end stop 1001b and cause the adjustment element 809 to pivot about the first pivot point 807a and separate the interlocking teeth on the crankshaft 801 and lug 802. Further rotation beyond the angular limit 901 causes the teeth to move relative to each other by one or more teeth pitch increments. Rotating the crankshaft back from the angular limit 901 then results in the teeth reengaging at an offset position, resulting in the relative rotation of the crankshaft 801 and lug 802 being offset from each other, as indicated by the offset in reference points 903, 904 in FIG. 10b. Further operation of the crankshaft within the normal angular limits 901, 902 then results in the position of the lug being offset relative to previously, as illustrated in FIG. 10c. This series of operations allows the relative rotational position of the crankshaft and lug to be determined solely by how far the crankshaft is actuated, which can be done without the need for any mechanical adjustment or replacement of the actuator assembly. A predefined software limit can be set to maintain actuation within the angular limits 901, 902 during normal operation. When the relative position of the crankshaft and lug needs to be altered, an adjustment routine can be run that takes the crankshaft beyond its normal angular limit so that a desired offset is then applied, which is then maintained during further normal operation.
[0094] A further end stop 1001a is also provided on the opposing side of the lug 802 to allow the relative rotational position of the crankshaft and lug to be adjusted in the opposite sense, the adjustment routine then being the reverse of that described above.
[0095] The type of adjustment element described above may, in alternative arrangements, be provided in more than one part, for example with two parts individually pivoted to allow each part to be separately released upon reaching an end stop. Each part may be arranged to allow relative movement in one direction but not the other, so that when one part is released by an end stop the other ratchets along the interlocking teeth.
[0096] The above described embodiment allows the relative rotation of the lug and crankshaft to be adjusted using only a single input, being that of rotating the crankshaft using the fueldraulic actuator. In some cases more flexibility may be required, for example where multiple lugs are provided on a common crankshaft that operate multiple unison rings. In such cases, adjustments may be required to each lug that are different. To do this, a different mechanism for adjusting the relative position of the crankshaft and lug may be required, based on a similar principle of interlocking teeth on the crankshaft and lug. One example of this is illustrated in FIG. 11, in which a crankshaft 1101 and lug 1102 are connected for common rotation by interlocking teeth 1104a, 1104b. The interlocking teeth 1104b on the lug are part of an adjustment element 1109 that is connected to an actuator 1110. The actuator 1110, which may for example be a solenoid, can be operated to separate the teeth 1104b on the lug 1102 from the teeth 1104a on the crankshaft 1101. An adjustment operation can therefore involve providing an actuation signal to the actuator 1110 to separate the teeth 1104a, 1104b from each other, followed by movement of the crankshaft 1101 to rotate the crankshaft 1101 relative to the lug 1102 by a desired offset, corresponding to one or more teeth pitch increments. The actuation signal can then be removed, allowing the teeth 1104b on the lug 1102 to return into contact with the teeth 1104a on the crankshaft 1101 at the desired offset. Operation of the crankshaft can then continue with the crankshaft 1101 offset from the lug 1102.
[0097] A further alternative example embodiment is illustrated in FIG. 12, in which the teeth 1204a on the crankshaft 1201 are engaged with corresponding teeth 1204b on a worm screw 1210 in the lug 1202 in a worm drive arrangement. The worm screw 1210 can be turned about a longitudinal axis 1211 to cause the rotational position of the crankshaft 1201 to be adjusted relative to the lug 1202. One complete turn of the worm screw 1210 then corresponds to an adjustment of the lug 1202 one tooth pitch relative to the crankshaft 1201. This adjustment may for example be achieved by manually adjusting the worm screw 1210 or by driving the worm screw using a motor (not shown), which may be a servo motor arranged to rotate the worm screw by known increments. Adjustment of the relative position of the crankshaft 1201 and lug 1202 can be carried out simply by rotating the worm screw 1210. If using a motor to drive the worm screw 1210 this may even be carried out during normal operation of the crankshaft assembly.
[0098] A further alternative example of a crankshaft assembly 1300 is illustrated in FIG. 13 in which, rather than interlocking teeth, the lug 1302 and crankshaft 1301 are clamped together by friction with a releasable clamping element 1309. The clamping element 1309 is in the example shown in the form of a shoe that provides a clamping force against the crankshaft, similar in form to a railway brake shoe. The clamping element 1309 is biased against the crankshaft 1301 to maintain a clamping force, and may be released from contact either manually or with an actuator such as a solenoid 1310 in a similar way to the example shown in FIG. 11. Other clamping arrangements may also be possible, such as the use of more than one clamping element distributed around the crankshaft or a clamping ring wrapped around the crankshaft that tightens around the crankshaft to secure the lug to the crankshaft. The clamping element may alternatively be provided as part of the crankshaft so that the clamping element operates in a way similar to an automobile drum brake.
[0099] 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.
