Device for varying the bypass ratio of a variable-length bladed turbojet engine

Abstract

This device for varying the bypass ratio of a turbojet engine comprises a fan (13) including variable-length blades (15) and an abradable ring (14), the blades (15) each comprising a foot (20) and a radially movable end (21), the abradable ring (14) including an adjustment element (53; 58) for the perimeter of the abradable ring (14) such that the diameter of the abradable ring is variable. Figure for the abbreviation: Fig 2

Description

Title of the invention: Device for varying the bypass ratio of a variable-length bladed turbojet engine technical field

[0001] The present invention relates to aircraft turbojet engines.

[0002] The present invention relates more particularly to the fan of an aircraft turbojet and in particular to the parameters of the fan blades which can influence the bypass ratio of the turbojet. Previous techniques

[0003] A turbojet is a propulsion system generally and schematically comprising a fan, a compressor, a combustion chamber and a turbine.

[0004] The fan comprises blades and accelerates the air entering the turbojet engine. The fan directs part of the air to a primary flow passing through the compressor, the combustion chamber and then the turbine, and another part to a secondary flow which is ejected without passing through the compressor, the combustion chamber and the turbine.

[0005] Figure 1 shows a schematic view of the air inlet of a turbojet engine 1 comprising a casing 2 and a fan 3 comprising an abradable ring 4, blades 5 and a cone 6. At the outlet of the fan 3, the air is split into a primary flow 7 and a secondary flow 8.

[0006] The compressor compresses the air from the primary stream 7.

[0007] The combustion chamber allows the compressed air and burning kerosene to be mixed to carry out the combustion enabling the propulsion of the aircraft.

[0008] The turbine expands the mixed gas to recover energy and drive the compressor, the primary airflow 7 exiting through a nozzle.

[0009] The bypass ratio of a turbojet engine is the ratio between the secondary flow 8 and the primary flow 7. When the bypass ratio is high, fuel consumption is reduced, thus lowering the turbojet's environmental impact. Currently, bypass ratios greater than 10:1 exist and require a very large air inlet to create a significant secondary flow within the turbojet.

[0010] However, a larger air intake implies different aerodynamic problems and leads to a lower fan and turbine rotational speed, which impacts the performance of the turbojet. Yet, certain flight phases, particularly takeoff, require full turbojet power.

[0011] Existing solutions use, for example, reducers to ensure rapid rotation of the turbine while the blower rotates more slowly. Description of the invention

[0012] The present invention therefore aims to overcome the aforementioned drawback by proposing an alternative turbojet architecture capable of offering a variable bypass ratio.

[0013] The present invention relates to a device for varying a dilution rate of a turbojet engine comprising a fan including variable length blades and an abradable ring, the blades each including a foot and a radially movable end, the abradable ring including an element for adjusting the perimeter of the abradable ring so that the diameter of the abradable ring is variable.

[0014] Thus, the bypass ratio of the turbojet engine is made variable by the possibility of enlarging the air inlet by increasing the diameter of the abradable ring and the length of the blades. In particular, the diameter is reduced during takeoff and enlarged during the cruise phase in order to increase the bypass ratio.

[0015] In one embodiment, the abradable ring comprises a ring including a radial slot, the adjustment element comprising a trapezoid movable radially in the slot so that the width of the slot varies according to the position of the adjustment element.

[0016] In another embodiment, the abradable ring comprises a ring including a radial slot and an internal housing adapted to accommodate the adjustment element, the adjustment element comprising a hoop adapted to be deployed outside the internal housing so that the width of the slot varies according to the deployment of the adjustment element.

[0017] Advantageously, each blade includes at least one fastening means suitable for securing the foot and the movable end of each blade.

[0018] Advantageously, each blade comprises at least one helical compression spring placed around at least one fastening means

[0019] Advantageously, the compression spring of each blade is capable of deforming under the effect of the centrifugal force exerted on the blade when the blade is set in motion.

[0020] In a particular embodiment, the base of each blade includes a pneumatic or hydraulic circuit capable of setting the movable end of the blade in motion.

[0021] In another particular embodiment, the means for fixing each blade comprises a threaded nut fixed to the movable end, and a worm screw motorized from the base and capable of passing through the nut and setting the movable end in motion.

[0022] The invention also relates to a turbojet engine of an aircraft, comprising a device as defined previously.

[0023] The invention further relates to an aircraft comprising a turbojet engine as defined above. Brief description of the drawings

[0024] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings in which:

[0025] [Fig. 1] which has already been mentioned, schematically illustrates a view of the air inlet of a turbojet according to the prior art;

[0026] [Fig.2] schematically illustrates a view of the air inlet of a turbojet engine according to the invention;

[0027] [Fig.3] schematically illustrates a view of a first embodiment of a blade of a device for varying a dilution rate according to the invention;

[0028] [Fig.4] schematically illustrates a view of a second embodiment of a blade of a device for varying a dilution rate according to the invention;

[0029] [Fig.5] schematically illustrates a view of a third embodiment of a blade of a device for varying a dilution rate according to the invention;

[0030] [Fig.6] schematically illustrates a view of a fourth embodiment of a blade of a device for varying a dilution rate according to the invention;

[0031] [Fig.7A]

[0032] and

[0033] [Fig.7B] schematically illustrate views of a fifth embodiment of a blade of a device for varying a dilution rate according to the invention;

[0034] [Fig. 8 A]

[0035] and

[0036] [Fig.8B] schematically illustrate views of a first embodiment of an abradable ring of a device for varying a dilution rate according to the invention;

[0037] [Fig. 9] schematically illustrates a view of a second embodiment of an abradable ring of a device for varying a dilution ratio according to the invention. Detailed description of at least one embodiment

[0038] Figure 2 shows a schematic view of the air inlet of a turbojet engine 10 comprising a casing 11 and a device 12 for varying the dilution rate of the turbojet engine.

[0039] The device 12 includes a blower 13 comprising an abradable ring 14, blades 15 and a cone 16. At the outlet of the blower 13, the incoming airflow is split into a primary flow 17 and a secondary flow 18.

[0040] The blades 15 comprise a foot 20 fixed to the cone 16 and a movable end 21 capable of radial movement. Depending on the radial position of the movable ends 21, the blades 15 thus have a variable length. The movable ends 21 have a profile similar to the profile of the foot 20 of each blade 15.

[0041] The abradable ring 14 includes an adjustment element (not shown in [Fig.2]) thus allowing the perimeter and diameter of the abradable ring 14 to be varied.

[0042] During takeoff, the turbojet 10 must have sufficient power and perform well. Therefore, it is important not to increase the bypass ratio too much. During takeoff, the abradable ring 14 has a minimum diameter and the blades 15 have a minimum length.

[0043] During the cruise phase, the performance of the turbojet 10 can be optimized to achieve lower fuel consumption by increasing the bypass ratio. During the cruise phase, the diameter of the abradable ring 14 is increased to a maximum diameter. Similarly, the length of the blades 15 is increased to a maximum length.

[0044] The movable ends 21 and the abradable ring 14 are in sliding contact with each other. When the dimensions of the blades 15 vary, the dimensions of the abradable ring 14 also vary so that sliding contact always exists between the movable ends 21 and the abradable ring 14. Similarly, when the dimensions of the abradable ring 14 vary, the dimensions of the blades 15 also vary so that sliding contact always exists between the movable ends 21 and the abradable ring 14.

[0045] The abradable ring 14 is made of a material offering minimal friction during sliding contact with the movable ends 21. The abradable ring 14 is capable of wearing slightly in contact with the movable ends 21.

[0046] The movable ends 21 are made of a soft material so that the abradable ring 14 is not excessively damaged during sliding contact. The material used is, for example, brass or Teflon (registered trademark). Each movable end 21 can thus be replaced if it is damaged by contact with the abradable ring 14.

[0047] A first embodiment of a variable length blade 15 of a dilution rate variation device has been schematically represented in [Fig.3].

[0048] The blade 15 comprises a foot 20 and a radially movable end 21. The foot 20 includes a hollow groove 22 adapted to receive a shoulder 23 of the movable end 21. The groove 22 also allows the movable end 21 to be guided radially during its radial deployment.

[0049] The blade 15 further comprises at least one means 25 for attaching the movable end 21 to the foot 20 in order to secure the foot and the movable end. Each The fastening means 25 includes a head 26. To ensure good strength of the blade 15, the blade includes, for example, two fastening means 25. A fastening means 25 includes, for example, a screw positioned along the length of the blade 15.

[0050] The movable end 21 includes, for example, longitudinal cavities 27 through which the fastening means 25 can be inserted through the shoulder 23 and then screwed into the bottom 28 of the groove 22 of the foot 20. The head 26 of each fastening means 25 is positioned in a longitudinal cavity 27 without contacting the base 29 of the cavity when the blade 15 has a reduced length. Conversely, the head 26 of each fastening means 25 is positioned in the longitudinal cavity 27 bearing against the base 29 when the blade 15 has a maximum length.

[0051] Each blade 15 also includes a helical compression spring 30 positioned around each fastening means 25.

[0052] Each blade foot 20 15 includes a bearing surface 31 for each compression spring 30 so that each compression spring 30 is fixed to the shoulder 23 of the movable end 21 on one side and to a bearing surface 31 in the bottom 28 of the gutter 22 of the foot on the other side.

[0053] In this embodiment, the blades 15 have a minimum length during the aircraft's takeoff phase. They are maintained at a minimum length by sliding contact with the abradable ring 14 and / or with a latch (not shown). During the cruise flight phase, the diameter of the abradable ring 14 is increased and the length of the blades 15 is increased by applying centrifugal force to each movable end 21. Each compression spring 30 dampens the movements of the movable end 21. In particular, each compression spring 30 is dimensioned to be able to deform under the effect of the centrifugal force exerted on the moving blades 15.

[0054] A second embodiment of a variable length blade 15 of a dilution rate variation device has been schematically represented in [Fig.4].

[0055] The blade 15 comprises a foot 20 and a radially movable end 21. The foot 20 includes a hollow groove 22 adapted to receive a shoulder 23 of the movable end 21. The groove 22 also allows the movable end 21 to be guided radially during its radial deployment.

[0056] The blade 15 further includes at least one means 25 for attaching the movable end 21 to the foot 20 in order to secure the foot and the movable end. Each means 25 includes a head 26. To ensure the blade 15 is sufficiently robust, the blade includes, for example, two means 25. One means 25 includes, for example, a screw positioned lengthwise along the blade 15.

[0057] The movable end 21 includes, for example, longitudinal cavities 27 through which the fastening means 25 can be inserted through the shoulder 23 then screwed into the bottom 28 of the gutter 22 of the foot 20. Each longitudinal cavity includes a base 29.

[0058] Each blade 15 also includes a helical compression spring 30 positioned around each fastening means 25.

[0059] In this embodiment, each compression spring 30 is fixed to the head 26 on one side and to the base 29 on the other. In this way, tightening the fastening means 25 ensures the calibration of the compression springs, which can be tightened to a precise torque in order to adapt the deployment of the movable end for different motor configurations.

[0060] In this embodiment, the blades 15 have a minimum length during the aircraft's takeoff phase. They are maintained at a minimum length by sliding contact with the abradable ring 14 and / or with a latch (not shown). During the cruise flight phase, the diameter of the abradable ring 14 is increased and the length of the blades 15 is increased by applying centrifugal force to each movable end 21. Each compression spring 30 dampens the movements of the movable end 21. In particular, each compression spring 30 is dimensioned to be able to deform under the effect of the centrifugal force exerted on the moving blades 15.

[0061] A third embodiment of a variable length blade 15 of a dilution rate variation device has been schematically represented in [Fig.5].

[0062] The blade 15 comprises a foot 20 and a radially movable end 21. The foot 20 includes a hollow groove 22 adapted to receive a shoulder 23 of the movable end 21. The groove 22 also allows the movable end 21 to be guided radially during its radial deployment.

[0063] The blade 15 further includes at least one means 25 for attaching the movable end 21 to the foot 20 in order to secure the foot and the movable end. Each means 25 includes a head 26. For example, the blade includes a means 25 comprising a screw positioned along the length of the blade 15.

[0064] The movable end 21 includes, for example, a longitudinal cavity 27 through which the fastening means 25 can be inserted through the shoulder 23 and then screwed into the bottom 28 of the groove 22 of the foot 20. Each longitudinal cavity includes a base 29.

[0065] Each blade 15 also includes a helical compression spring 30 positioned around the fastening means 25.

[0066] In this embodiment, each compression spring 30 is fixed to the head 26 on one side and to the base 29 on the other. In this way, tightening the fastening means 25 ensures the calibration of the compression springs, which can be tightened to a precise torque in order to adapt the deployment of the movable end for different engine configuration.

[0067] In this embodiment, the foot includes a pneumatic or hydraulic circuit 35. The pneumatic circuit 35 includes two deployment lines 36 opening from the bottom 28 into the gutter 22. The pneumatic circuit 35 further includes a balancing line 37 connecting the two deployment lines 36.

[0068] The movable ends 21 each comprise two pistons 38 suitable for inserting into the deployment channels 36 of the foot 20. Each piston 38 is encircled by a sealing O-ring 39.

[0069] In this embodiment, the blades 15 have a minimum length during the aircraft's takeoff phase. They are maintained at a minimum length by sliding contact with the abradable ring 14 and / or with a latch (not shown) and / or by a vacuum in the pneumatic circuit 35. During a cruise flight phase, the diameter of the abradable ring 14 is increased and the length of the blades 15 is increased by increasing the pressure in the pneumatic circuit 35, which pushes back the movable end 21. Each compression spring 30 dampens the movements of the movable end 21.

[0070] A fourth embodiment of a variable length blade 15 of a dilution rate variation device has been schematically represented in [Fig.6].

[0071] The blade 15 comprises a foot 20 and a radially movable end 21. The foot 20 includes a hollow groove 22 adapted to receive a shoulder 23 of the movable end 21. The groove 22 also allows the movable end 21 to be guided radially during its radial deployment.

[0072] The blade 15 further includes at least one means for securing the movable end 21 to the foot 20 in order to secure the foot and the movable end. The means for securing 40 includes a threaded nut 41 and a tube 42. The tube 42 is fixed to the shoulder 23 of the movable end 21 on one side, and to the contours of the threaded nut 41 on the other, so that the threaded nut 41 is fixed relative to the movable end 21. The means for securing 40 further includes a motorized worm gear 43 passing through the threaded nut 41. The means for securing 40 also includes a motor 45 and a gear 46 suitable for rotating the worm gear 43.

[0073] In this embodiment, the rotating worm screw 43 moves the nut longitudinally so that the movable end 21 is movable and lengthens or reduces the length of the blade 15.

[0074] Figures 7A and 7B show schematically a fifth embodiment of a variable length blade 15 of a dilution rate variation device.

[0075] The blade 15 comprises a foot 20 and a radially movable end 21.

[0076] The blade 15 further comprises at least one means 50 for attaching the movable end 21 to the foot 20 in order to secure the foot and the movable end. The means 50 for attaching comprises, for example, a pivot joint.

[0077] Fig.7A represents a blade 15 of shorter length than the blade 15 shown in Fig.7B.

[0078] Figures 8A and 8B show a first embodiment of an abradable ring 14 in a housing 11. The abradable ring comprises a ring 51 having a radial slot 52. The slot 52 creates an interruption in the material of the ring 51.

[0079] The abradable ring 14 includes an adjustment element 53 for the perimeter of the abradable ring 14. The adjustment element 53 comprises a trapezoid that can be moved radially within the slot 52 such that the width of the slot 52 varies depending on the position of the adjustment element 53. The trapezoidal shape of the adjustment element 53 allows the slot 52 to be easily widened when the faces of the slot 52 are inclined. [Fig. 8A] shows an abradable ring 14 with a diameter smaller than the diameter of the abradable ring 14 shown in [Fig. 8B], the radial position of the adjustment element 53 being different.

[0080] Figure 9 shows a view of a second embodiment of an abradable ring 14. The abradable ring 14 comprises a ring 55 having a radial slot 56. The slot 56 creates an interruption in the material of the ring 55. The ring 55 further comprises an internal housing 57.

[0081] The abradable ring 14 includes an adjustment element 58 for the perimeter of the abradable ring 14. The adjustment element 58 includes a hoop.

[0082] The internal housing 57 is suitable for receiving the adjustment element 58 and the adjustment element 58 is suitable for being deployed outside the internal housing so that the width of the slot 56 varies depending on the deployment of the adjustment element 58.

Claims

Demands

1. Device for varying a dilution ratio of a turbojet engine, characterized in that it comprises a fan (13) including blades (15) of variable length and an abradable ring (14), the blades (15) each comprising a foot (20) and a radially movable end (21), the abradable ring (14) including an adjustment element (53; 58) for the perimeter of the abradable ring (14) such that the diameter of the abradable ring is variable.

2. Device according to claim 1, wherein the abradable ring comprises a ring (51) including a radial slot (52), and wherein the adjusting element (53) comprises a trapezoid movable radially in the slot (52) such that the width of the slot varies according to the position of the adjusting element.

3. Device according to claim 1, wherein the abradable ring comprises a ring (55) including a radial slot (56) and an internal housing (57) adapted to accommodate the adjustment element (58), the adjustment element comprising a hoop adapted to be deployed outside the internal housing (57) so that the width of the slot (56) varies according to the deployment of the adjustment element (58).

4. Device according to any one of claims 1 to 3, wherein each blade (15) comprises at least one fastening means (25; 40; 50) suitable for joining the foot (20) and the movable end (21) of each blade (15).

5. Device according to claim 4, wherein each blade (15) comprises at least one helical compression spring (30) placed around at least one fastening means (25).

6. Device according to claim 5, wherein at least one compression spring (30) of each blade (15) is capable of deforming under the effect of the centrifugal force exerted on the blade when the blade is set in motion.

7. Device according to claim 5, wherein the foot (20) of each blade (15) comprises a pneumatic (35) or hydraulic circuit capable of setting in motion the movable end (21) of the blade.

8. A device according to claim 4, wherein the fastening means (40) for each blade comprises a threaded nut (41) fixed to the movable end, and a worm screw (43) motorized from the foot and capable of passing through the threaded nut (41) and moving the end mobile.

9. Aircraft turbojet engine, comprising a device (12) according to any one of claims 1 to 8.

10. Aircraft comprising a turbojet engine according to claim 9.

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