FR3128741A1 - Device for varying a bypass ratio of a turbojet engine with variable length blades - Google Patents

Abstract

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

Description

Device for varying a bypass ratio of a turbojet engine with variable length blades

The present invention relates to aircraft turbojets.

The present invention relates more particularly to the fan of an aircraft turbojet engine and in particular the parameters of the fan blades which can influence the bypass rate of the turbojet engine.

Prior techniques

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

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

We represented on the 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 stream 7 and a secondary stream 8.

The compressor compresses the air from the primary stream 7.

The combustion chamber is used to mix compressed air and ignited kerosene to perform combustion allowing the propulsion of the aircraft.

The turbine expands the mixed gas to recover energy and drive the compressor, the primary air flow 7 exiting through a nozzle.

The bypass ratio of a turbojet is the ratio between the secondary flow 8 and the primary flow 7. When the bypass ratio is high, fuel consumption is reduced, which reduces the environmental impact of the turbojet. Currently, bypass ratios greater than 10/1 exist and require a very wide air inlet so that a significant secondary flow is created in the turbojet engine.

However, a larger air intake involves different aerodynamic issues and leads to a lower fan and turbine rotation speed, which impacts the performance of the turbojet engine. However, certain phases of flight, in particular on takeoff, require full power from the turbojet engine.

Existing solutions use reduction gears, for example, to ensure rapid rotation of the turbine while the fan rotates more slowly.

The present invention therefore aims to overcome the aforementioned drawback by proposing an alternative turbojet architecture that can offer a variable bypass rate.

The subject of the present invention is a device for varying the bypass rate of a turbojet engine comprising a fan comprising blades of variable length and an abradable ring, the blades each comprising a root and a radially movable end, the abradable ring comprising an element for adjusting the perimeter of the abradable ring so that the diameter of the abradable ring is variable.

Thus, the bypass rate of the turbojet 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 widened during a cruise flight phase in order to increase the dilution rate.

In one embodiment, the abradable ring comprises a ring comprising a radial slot, the adjustment element comprising a trapezium movable radially in the slot so that the width of the slot varies according to the position of the adjustment element. setting.

In another embodiment, the abradable ring comprises a ring comprising a radial slot and an internal housing capable of receiving the adjustment element, the adjustment element comprising a hoop capable of being deployed outside the internal housing so that the width of the slot varies according to the deployment of the adjustment element.

Advantageously, each blade comprises at least one fixing means capable of securing the root and the mobile end of each blade.

Advantageously, each blade comprises at least one helical compression spring placed around the at least one fixing means

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.

In a particular embodiment, the root of each blade comprises a pneumatic or hydraulic circuit capable of setting the mobile end of the blade in motion.

In another particular embodiment, the means for fixing each blade comprises a threaded nut fixed to the movable end, and an endless screw motorized from the foot and able to pass through the nut and to set the blade in motion. moving end.

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

The invention further relates to an aircraft comprising a turbojet engine as defined above.

Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which:

which has already been mentioned, schematically illustrates a view of the air inlet of a turbojet engine according to the state of the art;

schematically illustrates a view of the air inlet of a turbojet according to the invention;

schematically illustrates a view of a first embodiment of a blade of a device for varying a dilution rate according to the invention;

schematically illustrates a view of a second embodiment of a blade of a device for varying a dilution rate according to the invention;

schematically illustrates a view of a third embodiment of a blade of a device for varying a dilution rate according to the invention;

schematically illustrates a view of a fourth embodiment of a blade of a device for varying a dilution rate according to the invention;

And

schematically illustrate views of a fifth embodiment of a blade of a device for varying a dilution rate according to the invention;

And

schematically illustrate views of a first embodiment of an abradable ring of a device for varying a dilution rate according to the invention;

schematically illustrates a view of a second embodiment of an abradable ring of a device for varying a dilution rate according to the invention.

Detailed description of at least one embodiment

We represented on the a schematic view of the air inlet of a turbojet engine 10 comprising a casing 11 and a device 12 for varying the bypass rate of the turbojet engine.

The device 12 comprises a fan 13 comprising an abradable ring 14, blades 15 and a cone 16. At the outlet of the fan 13, the incoming air flow is split into a primary flow 17 and a secondary flow 18.

The blades 15 comprise a foot 20 fixed to the cone 16 and a movable end 21 able to move radially. Depending on the radial position of the movable ends 21, the blades 15 thus have a variable length. The mobile ends 21 have a profile similar to the profile of the root 20 of each blade 15.

The abradable ring 14 comprises an adjustment element (not shown in the ) thus making it possible to vary the perimeter and the diameter of the abradable ring 14.

In a take-off phase, the turbojet engine 10 must have power and be efficient. It is therefore useful not to increase the dilution rate too much. In a take-off phase, the abradable ring 14 has a minimum diameter and the vanes 15 have a minimum length.

In a cruising phase, the performance of the turbojet engine 10 can be optimized and allow lower fuel consumption by increasing the bypass ratio. In a cruising 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.

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 a sliding contact always exists between the moving ends 21 and the abradable ring 14. Likewise, when the dimensions of the abradable ring 14 vary, the dimensions of the blades 15 also vary so that a sliding contact always exists between the moving ends 21 and the abradable ring 14.

The abradable ring 14 is made of a material offering a minimum of friction during sliding contact with the movable ends 21. The abradable ring 14 is able to wear slightly on contact with the movable ends 21.

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

Schematically represented on the a first embodiment of a vane 15 of variable length of a device for varying the dilution rate.

The blade 15 comprises a foot 20 and a radially movable end 21. The foot 20 comprises a hollow gutter 22 capable of receiving a shoulder 23 of the mobile end 21. The gutter 22 also makes it possible to guide the mobile end 21 radially during its radial deployment.

The blade 15 further comprises at least one means 25 for fixing the mobile end 21 to the foot 20 in order to secure the foot and the mobile end. Each fastening means 25 comprises a head 26. To guarantee good solidity of the blade 15, the blade comprises for example two fastening means 25. A fastening means 25 comprises for example a screw positioned in the length of the dawn 15.

The movable end 21 comprises, for example, longitudinal cavities 27 through which the fixing means 25 can be inserted through the shoulder 23 and then screwed into the bottom 28 of the gutter 22 of the foot 20. The head 26 of each means of attachment 25 is positioned in a longitudinal cavity 27 without contact with 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.

Each vane 15 also comprises a helical compression spring 30 positioned around each fixing means 25.

Each foot 20 of blade 15 comprises 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 the one hand and to a surface of support 31 in the bottom 28 of the gutter 22 of the foot on the other hand.

In this embodiment, the blades 15 have a minimum length during a take-off phase of the aircraft. They are held to a minimum length by sliding contact with the abradable ring 14 and/or with a latch (not shown). During a 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 makes it possible to damp the movements of the movable end 21. In particular, each compression spring 30 is sized to be capable of deforming under the effect of the centrifugal force exerted on the blades 15 set in motion.

Schematically represented on the a second embodiment of a vane 15 of variable length of a device for varying the dilution rate.

The blade 15 comprises a foot 20 and a radially movable end 21. The foot 20 comprises a hollow gutter 22 capable of receiving a shoulder 23 of the mobile end 21. The gutter 22 also makes it possible to guide the mobile end 21 radially during its radial deployment.

The blade 15 further comprises at least one means 25 for fixing the mobile end 21 to the foot 20 in order to secure the foot and the mobile end. Each fastening means 25 comprises a head 26. To guarantee good solidity of the blade 15, the blade comprises for example two fastening means 25. A fastening means 25 comprises for example a screw positioned in the length of the dawn 15.

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

Each vane 15 also comprises a helical compression spring 30 positioned around each fixing means 25.

In this embodiment, each compression spring 30 is fixed to the head 26 on the one hand and to the base 29 on the other hand. In this way, the tightening of the fixing 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 configurations.

In this embodiment, the blades 15 have a minimum length during a take-off phase of the aircraft. They are held to a minimum length by sliding contact with the abradable ring 14 and/or with a latch (not shown). During a 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 makes it possible to damp the movements of the movable end 21. In particular, each compression spring 30 is sized to be capable of deforming under the effect of the centrifugal force exerted on the blades 15 set in motion.

Schematically represented on the a third embodiment of a vane 15 of variable length of a device for varying the dilution rate.

The blade 15 comprises a foot 20 and a radially movable end 21. The foot 20 comprises a hollow gutter 22 capable of receiving a shoulder 23 of the mobile end 21. The gutter 22 also makes it possible to guide the mobile end 21 radially during its radial deployment.

The blade 15 further comprises at least one means 25 for fixing the mobile end 21 to the foot 20 in order to secure the foot and the mobile end. Each fastening means 25 comprises a head 26. For example, the blade includes a fastening means 25 comprising a screw positioned in the length of the blade 15.

The movable end 21 comprises for example a longitudinal cavity 27 through which the fixing means 25 can be inserted through the shoulder 23 and then screwed into the bottom 28 of the gutter 22 of the foot 20. Each longitudinal cavity comprises a base 29 .

Each vane 15 also comprises a helical compression spring 30 positioned around the fixing means 25.

In this embodiment, each compression spring 30 is fixed to the head 26 on the one hand and to the base 29 on the other hand. In this way, the tightening of the fixing 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 configurations.

In this embodiment, the foot comprises a pneumatic or hydraulic circuit. The pneumatic circuit 35 comprises two deployment pipes 36 opening via the bottom 28 into the gutter 22. The pneumatic circuit 35 also comprises a balancing pipe 37 connecting the two deployment pipes 36.

The movable ends 21 each comprise two pistons 38 capable of being inserted into the deployment pipes 36 of the foot 20. Each piston 38 is surrounded by an O-ring 39 for sealing.

In this embodiment, the blades 15 have a minimum length during a take-off phase of the aircraft. 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 vanes 15 is increased by increasing the pressure in the pneumatic circuit 35 which pushes the movable end 21 back. Each compression spring 30 makes it possible to damp the movements of the movable end 21.

Schematically represented on the a fourth embodiment of a vane 15 of variable length of a device for varying the dilution rate.

The blade 15 comprises a foot 20 and a radially movable end 21. The foot 20 comprises a hollow gutter 22 capable of receiving a shoulder 23 of the mobile end 21. The gutter 22 also makes it possible to guide the mobile end 21 radially during its radial deployment.

The blade 15 further comprises at least one means 40 for fixing the mobile end 21 to the foot 20 in order to secure the foot and the mobile end. The fixing means 40 comprises a threaded nut 41 and a tube 42. The tube 42 is fixed to the shoulder 23 of the movable end 21 on the one hand, and to the contours of the threaded nut 41 on the other hand, so that the threaded nut 41 is fixed relative to the movable end 21. The fixing means 40 further comprises a motorized endless screw 43 passing through the threaded nut 41. The fixing means 40 comprises also a motor 45 and a gear 46 capable of rotating the endless screw 43.

In this embodiment, the rotating worm 43 sets the nut in motion longitudinally so that the movable end 21 is movable and lengthens or reduces the length of the blade 15.

A fifth embodiment of a blade 15 of variable length of a device for varying the dilution rate has been shown schematically in FIGS. 7A and 7B.

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

The blade 15 further comprises at least one means 50 for fixing the mobile end 21 to the foot 20 in order to secure the foot and the mobile end. The fixing means 50 comprises for example a pivot connection.

There represents a blade 15 of shorter length than the blade 15 shown in .

There is shown in Figures 8A and 8B a first embodiment of an abradable ring 14 in a housing 11. The abradable ring comprises a ring 51 comprising a radial slot 52. Slot 52 creates an interruption in the material of ring 51.

The abradable ring 14 comprises an adjustment element 53 of the perimeter of the abradable ring 14. The adjustment element 53 comprises a radially movable trapezoid in the slot 52 so that the width of the slot 52 varies according to the position of the adjustment element 53. The trapezoidal shape of the adjustment element 53 makes it possible to easily separate the slot 52 when the faces of the slot 52 are inclined. There represents an abradable ring 14 with a diameter smaller than the diameter of the abradable ring 14 shown in , the radial position of the adjusting element 53 being different.

We represented on the a view of a second embodiment of an abradable ring 14. The abradable ring 14 comprises a ring 55 comprising a slot 56 radially. The slot 56 creates an interruption in the material of the ring 55. The ring 55 also comprises an internal housing 57.

The abradable ring 14 comprises an adjustment element 58 of the perimeter of the abradable ring 14. The adjustment element 58 comprises a hoop.

The internal housing 57 is capable of receiving the adjustment element 58 and the adjustment element 58 is capable of being deployed outside the internal housing so that the width of the slot 56 varies according to the deployment of the adjustment element. setting 58.

Claims (10)

Device for varying the bypass rate of a turbojet, characterized in that it comprises a fan (13) comprising vanes (15) of variable length and an abradable ring (14), the vanes (15) each comprising a foot (20) and a radially movable end (21), the abradable ring (14) comprising an adjustment element (53; 58) of the perimeter of the abradable ring (14) so that the diameter of the ring abradable is variable. Device according to Claim 1, in which the abradable ring comprises a ring (51) comprising a radial slot (52), and in which the adjustment element (53) comprises a radially movable trapezium in the slot (52) so that the width of the slot varies depending on the position of the adjustment element. Device according to Claim 1, in which the abradable ring comprises a ring (55) comprising a radial slot (56) and an internal housing (57) capable of receiving 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). Device according to any one of Claims 1 to 3, in which each vane (15) comprises at least one fixing means (25; 40; 50) suitable for securing the foot (20) and the movable end (21) of each dawn (15). Device according to Claim 4, in which each vane (15) comprises at least one helical compression spring (30) placed around the at least one fixing means (25). Device according to Claim 5, in which the 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 movement. Device according to Claim 5, in which the root (20) of each vane (15) comprises a pneumatic (35) or hydraulic circuit capable of setting the movable end (21) of the vane in motion. Device according to Claim 4, in which the fixing means (40) of each blade comprises a threaded nut (41) fixed to the movable end, and a worm (43) motorized from the foot and able to pass in threaded nut (41) and moving the movable end. Aircraft turbojet, comprising a device (12) according to any one of claims 1 to 8. Aircraft comprising a turbojet engine according to claim 9.