TURBOMACHINE FOR AN AIRCRAFT

Abstract

Turbomachine (10) for an aircraft, comprising a compressor (12), an annular combustion chamber (16), a turbine (20), and a tube (52) which extends axially inside a shaft (28) and which comprises an upstream end (52a) integral in rotation with an upstream end (28a) of the shaft (28), characterized in that the shaft (28) comprises a downstream end (28b) which is free to move in rotation relative to a downstream end (52b) of the tube (52) over a predetermined angular travel (β), and which is connected to this downstream end (52b) of the tube (52) by an automatic brake system with pads (54). Abstract figure: figure 1

Description

Title of the invention: TURBOMACHINE FOR AN AIRCRAFT Technical field of the invention

[0001] The invention relates to a turbomachine for an aircraft. Technical background

[0002] The state of the art includes in particular documents FR-A1-3 026 774, FR-Al-2 773 586 and WO-A1-2011 / 117560.

[0003] In a well-known manner, an aircraft turbomachine extends along a longitudinal axis and comprises, from upstream to downstream in the direction of gas flow, a fan, at least one compressor, an annular combustion chamber, at least one turbine and finally a combustion gas exhaust nozzle. In the case of a twin-spool turbomachine, respectively low pressure and high pressure, the turbomachine comprises, between the fan and the nozzle, a low pressure compressor, a high pressure compressor, the combustion chamber, a high pressure turbine, and a low pressure turbine.

[0004] The high-pressure body comprises a high-pressure shaft which connects the rotor of the high-pressure compressor to the rotor of the high-pressure turbine. The high-pressure shaft is tubular and axially traversed by the low-pressure shaft of the low-pressure body. This low-pressure shaft connects the rotor of the low-pressure compressor to the rotor of the low-pressure turbine, and is further connected directly or via a mechanical reducer to the fan shaft.

[0005] In the event of damage such as the rupture of a fan blade, called FBO (which is the acronym for Fan Blade Yes), a significant unbalance is created which causes a significant radial eccentricity of the upstream of the rotor until the contact between the fan and a casing which surrounds it. A significant braking torque resulting from this contact appears at the low pressure compressor while at the same time the turbine rotor continues to rotate and drive the low pressure shaft. Consequently, the low pressure shaft is subjected to a very significant torsional overtorque and twists. The torsion angle during such an event can reach high values ​​up to several tens of degrees. This angle is linked to a high torque in the low pressure shaft which in the majority of applications corresponds to the dimensioning load case for this shaft.

[0006] In the current technique, there are decoupler systems for reducing the radial load transmitted to the turbomachine. On the other hand, there is no solution for reducing the torsional torque induced in a shaft, and in particular in the low pressure shaft, by the aforementioned braking.

[0007] The invention provides a simple, effective and economical solution to this need. Summary of the invention

[0008] To this end, the invention proposes a turbomachine for an aircraft, comprising:

[0009] - at least one compressor,

[0010] - an annular combustion chamber,

[0011] - at least one turbine, the turbine comprising a rotor which is connected by a shaft to a compressor rotor, the shaft extending along a longitudinal axis and being tubular, and

[0012] - a tube which extends axially inside the shaft and which comprises a upstream end integral in rotation with an upstream end of the shaft,

[0013] characterized in that the shaft comprises a downstream end which is free to move in rotation relative to a downstream end of the tube over a predetermined angular travel, and which is connected to this downstream end of the tube by an automatic brake pad system, the brake system being movable from a non-functional retracted position in which the pads are radially spaced from a stator which surrounds the downstream end of the shaft, when the shaft is subjected to a torsional force around its axis which is zero or less than a predetermined threshold, and a functional deployed position in which the pads are applied radially against the stator in order to brake the shaft, when the shaft is subjected to a torsional force greater than said threshold.

[0014] The invention thus consists of implementing a system for limiting / reducing the torsional torque in the shaft under ultimate loading of the FBO type. Indeed, an event of the FBO type causes a strong torsion in the shaft. The idea of ​​the invention is to take advantage of this torsion to engage a braking system at the downstream end of the shaft in order to preserve the mechanical strength of the shaft and relieve its dimensioning. Indeed, the torsional torque of the shaft results from a difference in torque between the upstream and downstream when the upstream is subjected to a significant braking torque. If at the same time a braking torque is also applied at the downstream end of the shaft, this will reduce the torque and the torsion angle that this shaft undergoes. To achieve this, a "tube" is added inside the shaft, rotationally fixed to the shaft upstream and with at least one degree of freedom downstream, for example in rolling, with respect to the shaft.A brake system of the pad or drum type is also added downstream, capable of cooperating with a stator of the turbomachine, such as a bearing support(s).

[0015] The turbomachine according to the invention may comprise one or more of the following characteristics, taken in isolation from one another or in combination with one another: - the stator is a bearing support(s) which carries at least one guide bearing of

[0016]

[0017]

[0018]

[0019]

[0020] the downstream end of the shaft; - the braking system comprises a pair of elongated arms, each of the arms having a first longitudinal end articulated on the shaft and a second longitudinal end which is opposite the first end and which carries at least one of the pads, each of the arms being further connected to the tube by a connecting rod; - the arms are diametrically opposed with respect to said longitudinal axis. - the arms are positioned tangentially relative to a circumference centered on said longitudinal axis; — the arms and connecting rods extend in a plane perpendicular to said axis; - each of the pads has a curved shape and includes a radially external bearing face which has a convex curved shape; - each of the pads has an angular extent greater than or equal to 20° around said longitudinal axis; - said angular travel is between 1 and 10°; - the downstream end of the tube is centered and guided in the downstream end of the shaft by at least one rolling bearing; - the downstream end of the tube is centered in the downstream end of the shaft by at least one support member; - it further comprises a bearing support(s) which carries at least one guide bearing for the upstream end of the shaft; - the tube is a degassing tube whose upstream end is capable of collecting de-oiled air from a lubrication enclosure of said at least one guide bearing of the upstream end of the shaft; - the turbomachine is double-body and comprises a low-pressure body and a high-pressure body, said shaft being part of the low-pressure body. Brief description of the figures Other characteristics and advantages will emerge from the following description of a non-limiting embodiment of the invention with reference to the appended drawings in which: [Fig.l] [Fig.l] is a partial schematic view in axial section of an aircraft turbomachine according to the invention; [Fig.2] [Fig.2] is a very schematic view of a shaft torsion phenomenon in an aircraft turbomachine; [Fig.3] [Fig.3] is a schematic cross-sectional view of a shaft and tube of a turbomachine according to the invention, and illustrates an embodiment of the shoe braking system which is here in a non-functional retracted position, and

[0021] [Fig.4] [Fig.4] is a view similar to that of [Fig.3] and illustrates a position functional deployment of the brake pad system. Detailed description of the invention

[0022] [Fig.l] illustrates an aircraft turbomachine 10 in which the invention can be installed. The configuration of the turbomachine 10 is therefore not limiting.

[0023] The turbomachine 10 has a longitudinal axis denoted X.

[0024] The turbomachine 10 is of the double-body type and comprises a low-pressure body and a high-pressure body.

[0025] The turbomachine 10 comprises a gas generator which comprises from upstream to downstream, in the direction of flow of the combustion gases, a low pressure compressor 12, a high pressure compressor 14, an annular combustion chamber 16, a high pressure turbine 18, and a low pressure turbine 20.

[0026] The rotor 14a of the high-pressure compressor 14 is connected by a high-pressure shaft 22 to the rotor 18a of the high-pressure turbine 18, to form the high-pressure body. The stators of the high-pressure compressor 14 and of the high-pressure turbine 18 are not shown in the drawing. The high-pressure shaft 22 is tubular and centered and guided in rotation by bearings 24, 26, respectively at the upstream and downstream ends of the shaft 22.

[0027] The rotor 12a of the low pressure compressor 12 is connected by a low pressure shaft 28 to the rotor 20a of the low pressure turbine 20, to form the low pressure body. The stators of the low pressure compressor 12 and of the low pressure turbine 20 are not shown in the drawing. The low pressure shaft 28 is tubular and passes inside the high pressure shaft 22. The low pressure shaft 28 is centered and guided in rotation by bearings 32, 34, at the upstream and downstream ends of the shaft 28.

[0028] The bearings 24, 32 for guiding the shafts 22, 28 located upstream can be carried by a bearing support 36 which can be connected to an intermediate casing 38. This intermediate casing 38 is located axially between the compressors 12, 14.

[0029] These bearings 24, 32 are preferably housed in a lubrication enclosure E in which an oil mist prevails. The oil-laden air contained in this enclosure E can pass through radial orifices 40 of the shaft 28 for the purpose of separating the air from the oil and evacuating the air discharged from the oil.

[0030] In the example shown, the bearing 26 is an inter-shaft bearing and is mounted between the shafts 22, 28. The bearing 34 located downstream can be carried by another bearing support 42 which can be connected to an exhaust casing 44. This exhaust casing 44 is located axially downstream of the turbines 18, 20.

[0031] The low pressure shaft 28 is further connected, directly or via a mechanical reducer, to a shaft 46 for driving a fan 48. The shaft 46 of the blower 48 is centered and guided in rotation by a bearing 30 carried by the bearing support 36.

[0032] The fan 48 rotates inside a fan casing 50 which can be connected to the aforementioned intermediate casing 38.

[0033] [Fig.2] illustrates a phenomenon of torsion of a shaft, such as a low pressure shaft 28, during a fault of the FBO type for example.

[0034] This damage causes an imbalance and a significant radial eccentricity of the fan 48 with the casing 50 which surrounds it. A significant braking torque resulting from this contact appears at the low pressure compressor 12 while at the same time the rotor 20a of the low pressure turbine 20 continues to rotate and to drive the low pressure shaft 28. Consequently, the low pressure shaft 28 is subjected to a very significant torsional overtorque and twists. The torsion angle during such an event can reach high values ​​up to several tens of degrees. This angle is linked to a high torque in the low pressure shaft 28 which in the majority of applications corresponds to the dimensioning load case for this shaft 28.

[0035] The invention makes it possible to solve this problem by means of a system making it possible to reduce the maximum torsional torque experienced by the shaft in extreme cases and therefore to relieve its dimensioning. This system is an automatic or passive brake pad system. In the present application, automatic or passive means that the system activates itself without any particular intervention, and in particular solely due to the torque or torsional force applied to the shaft in operation.

[0036] For this, the low pressure shaft 28 is axially crossed by a tube 52.

[0037] Advantageously, this tube 52 is a degassing tube, that is to say a tube capable of conveying the aforementioned de-oiled air from upstream to downstream of the turbomachine.

[0038] Alternatively, the tube 52 could not have this degassing function and be installed in the turbomachine solely for its braking function in accordance with the invention.

[0039] The tube 52 extends axially inside the shaft 28 and comprises an upstream end 52a integral in rotation with an upstream end 28a of the shaft 28.

[0040] The downstream end 52b of the tube 52 can be centered and guided in the downstream end 28b of the shaft 28 by at least one rolling bearing 53, or be centered in the downstream end 28b of the shaft 28 by at least one support member 53'.

[0041] The downstream end 28b of the shaft 28 is free to move in rotation relative to the downstream end 52b of the tube 52 over a predetermined angular travel.

[0042] The downstream end 28b of the shaft 28 is connected to the downstream end 52b of the tube 52 by the automatic brake pad system 54.

[0043] This braking system 54, one embodiment of which is illustrated in FIGS. 3 and 4, can adopt a non-functional retracted position ([Fig.3]) in which the pads 56 are radially spaced from a stator 58 which surrounds the downstream end 28b of the shaft 28, when the shaft 28 undergoes a torsional force around its axis X which is zero or less than a predetermined threshold.

[0044] The braking system 54 can adopt a functional deployed position ([Fig.4]) in which the pads 56 are applied radially against the stator 58 in order to brake the shaft 28, when the shaft 28 undergoes a torsional force greater than the aforementioned threshold.

[0045] The braking system 54 and the pads 56 are capable of moving from the retracted position to the deployed position automatically.

[0046] The aforementioned angular travel [3 between the shaft 28 and the tube 52 is for example between 1 and 10°.

[0047] In the example shown in [Fig.l], the stator 58 is formed by the bearing support 42 or a part connected to this bearing support. As will be described in the following, the stator 58 corresponds to the track on which the braking system 58 will exert pressure when the system is actuated.

[0048] In a preferred embodiment, the braking system 54 comprises a pair of elongated arms 60. Each of the arms 60 has a first longitudinal end 60a articulated on the shaft 28 and a second longitudinal end 60b which is opposite the first end 60a and which carries at least one of the pads 56. Each of the arms 60 is further connected to the tube 52 by a connecting rod 62.

[0049] The arms 60 are preferably diametrically opposed with respect to the longitudinal axis X.

[0050] The arms 60 may be positioned tangentially relative to a circumference centered on the longitudinal axis X.

[0051] The arms 60 and the connecting rods 62 preferably extend in a plane perpendicular to the X axis as in the example shown.

[0052] Each of the pads 56 may have a curved shape and comprise a radially external bearing face 56a which has a convex curved shape. This face is configured to bear on an internal cylindrical surface of the stator 58 in the example shown.

[0053] Each of the pads 56 has, for example, an angular extent a greater than or equal to 20° around the longitudinal axis X.

[0054] In normal operation, the braking system 54 is in the non-functional position ([Fig. 3]). If the shaft 28 undergoes a torsional force lower than the predetermined threshold, the braking system 54 remains in its non-functional position or in a position such that the pads 56 remain at a radial distance from the stator. More precisely, the actuation of the system is triggered by a position differential between the shaft 28 and the tube 52. A rotational phase shift is created between the two, which has the consequence of actuating the movement of the connecting rods 62 and the pads 56. As soon as the shaft 28 undergoes a torsional force greater than the threshold, the arms 60 deploy and the pads 56 bear on the stator to brake the shaft and reduce the torque and the torsion angle that this shaft undergoes.

[0055] After a torsional force, either the torsion is less than the elastic limit of the shaft 28 and in this case the system returns by itself to the initial position, or the torsion is greater than the elastic limit of the shaft 28 and, in this case, it would be possible to go so far as to immobilize the rotor which would not be problematic because in the event of an extreme event of this type, the motor is in any case no longer operable in the end and would require maintenance.

Claims

Claims

1. Turbomachine (10) for an aircraft, comprising: - at least one compressor (12), - an annular combustion chamber (16), - at least one turbine (20), the turbine (20) comprising a rotor (20a) which is connected by a shaft (28) to a rotor (12a) of the compressor (12), the shaft (28) extending along a longitudinal axis (X) and being tubular, and - a tube (52) which extends axially inside the shaft (28) and which comprises an upstream end (52a) integral in rotation with an upstream end (28a) of the shaft (28), characterized in that the shaft (28) comprises a downstream end (28b) which is free to move in rotation with respect to a downstream end (52b) of the tube (52) over a predetermined angular travel (|3), and which is connected to this end downstream (52b) of the tube (52) by an automatic brake pad system (54),the braking system (54) being movable from a non-functional retracted position in which the pads (56) are radially spaced from a stator (58) which surrounds the downstream end (28b) of the shaft (28), when the shaft (28) is subjected to a torsional force around its axis (X) which is zero or less than a predetermined threshold, and a functional deployed position in which the pads (56) are applied radially against the stator (58) in order to brake the shaft (28), when the shaft (28) is subjected to a torsional force greater than said threshold.,

2. Turbomachine (10) according to claim 1, in which the stator (58) is a bearing support(s) (42) which carries at least one bearing (34) for guiding the downstream end (28b) of the shaft (28).

3. Turbomachine (10) according to claim 1 or 2, in which the braking system (54) comprises a pair of arms (60) of elongated shape, each of the arms (60) having a first longitudinal end (60a) articulated on the shaft (28) and a second longitudinal end (60b) which is opposite the first end (60a) and which carries at least one of the pads (56), each of the arms (60) being further connected to the tube (52) by a connecting rod (62).

4. Turbomachine (10) according to claim 3, in which the arms (60) are diametrically opposed with respect to said longitudinal axis (X).

5. A turbomachine (10) according to claim 3 or 4, wherein the arms (60) are positioned tangentially relative to a circum- conference centered on said longitudinal axis (X).

6. Turbomachine (10) according to one of claims 3 to 5, in which each of the pads (56) has a curved shape and comprises a radially external bearing face (56a) which has a convex curved shape.

7. Turbomachine (10) according to claim 6, in which each of the pads (56) has an angular extent (a) greater than or equal to 20° around said longitudinal axis (X).

8. Turbomachine (10) according to one of the preceding claims, in which said angular stroke (|3) is between 1 and 10°.

9. Turbomachine (10) according to one of claims 1 to 8, in which the downstream end (52b) of the tube (52) is centered and guided in the downstream end (28b) of the shaft (28) by at least one rolling bearing (53).

10. Turbomachine (10) according to one of claims 1 to 8, in which the downstream end (52b) of the tube (52) is centered in the downstream end (28b) of the shaft (28) by at least one support member (53').

11. Turbomachine (10) according to one of the preceding claims, in which it further comprises a bearing support(s) (36) which carries at least one bearing (32) for guiding the upstream end (28a) of the shaft (28).

12. Turbomachine (10) according to the preceding claim, in which the tube (52) is a degassing tube whose upstream end (52a) is capable of collecting de-oiled air from a lubrication enclosure (E) of said at least one bearing (32) for guiding the upstream end (28a) of the shaft (28).

13. Turbomachine (10) according to one of the preceding claims, this turbomachine (10) being double-body and comprising a low-pressure body and a high-pressure body, said shaft (28) forming part of the low-pressure body.

Images