TURBOMACHINE FOR AN AIRCRAFT
The turbomachine incorporates an internal tube and automatic pad braking system to mitigate torsional torque and stress on the low-pressure shaft by engaging brakes when excessive torque is detected, addressing the issue of torsional overtorque and stress during fan blade breakage.
Patent Information
- Application Number
- FR2024001940
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2024-02-28
- Publication Date
- 2026-01-30
- Estimated Expiration
- 2044-02-28
AI Technical Summary
Current turbomachines lack a solution to reduce torsional torque in the low-pressure shaft, particularly in the event of a fan blade breakage (FBO), which leads to significant torsional overtorque and stress due to the imbalance and radial eccentricity, causing high torque and angle of twist.
A tubular shaft with an internal tube and an automatic pad braking system that engages when torsional force exceeds a threshold, applying brakes at the downstream end to mitigate torsional torque and reduce stress on the shaft.
The system effectively limits torsional torque and reduces stress on the shaft by engaging the braking system automatically, preserving mechanical integrity during extreme events like FBO, thereby reducing the angle of torsion and torque.
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Abstract
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] As is well known, 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, with low-pressure and high-pressure components respectively, 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 unit comprises a high-pressure shaft that 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 unit. This low-pressure shaft connects the rotor of the low-pressure compressor to the rotor of the low-pressure turbine and is further connected, either directly or via a mechanical reducer, to the blower shaft.
[0005] In the event of a failure such as the breakage of a fan blade, known as a FBO (Fan Blade Ounce), a significant imbalance is created, resulting in a substantial radial eccentricity from the upstream end of the rotor to the point of contact between the fan and its surrounding housing. 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 angle of twist 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 most applications corresponds to the load case designating this shaft.
[0006] In current technology, there are decoupler systems that reduce the radial load transmitted to the turbomachine. However, 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 offers 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 that extends axially inside the shaft and that includes a upstream end fixed in rotation to 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 stroke, and which is connected to this downstream end of the tube by an automatic pad braking system, the braking system being mobile from a non-functional retracted position in which the pads are at a radial distance from a stator which surrounds the downstream end of the shaft, when the shaft is subjected to a torsional force about 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 an ultimate load (UL) of the FBO type. Indeed, an FBO event results in 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 reduce stress on its design. In fact, the torsional torque of the shaft results from a difference in torque between the upstream and downstream ends when the upstream end 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 angle of torsion experienced by the shaft. To achieve this, a "tube" is added inside the shaft, fixed in rotation to the shaft upstream and with at least one degree of freedom downstream, for example in roll, with respect to the shaft.A braking system of the pad or drum type, capable of cooperating with a turbomachine stator, such as a bearing support(s), is also added downstream.
[0015] The turbomachine according to the invention may comprise one or more of the following features, taken individually or in combination with each other: - the stator is a bearing support(s) which carries at least one guide bearing
[0016]
[0017]
[0018]
[0019]
[0020] the downstream end of the tree; - the braking system comprises a pair of elongated arms, each arm 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 arm 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 with respect to a circumference centered on said longitudinal axis; — the arms and connecting rods extend in a plane perpendicular to said axis; - each of the skates has a curved shape and includes a radially external bearing face which has a convex curved shape; - each of the skates has an angular range greater than or equal to 20° around said longitudinal axis; - said angular stroke 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 roller bearing; - the downstream end of the tube is centered in the downstream end of the shaft by at least one support member; - it also includes 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 suitable for collecting oil-free air from a lubrication chamber 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 features and advantages will become apparent from the following description of a non-limiting embodiment of the invention with reference to the accompanying drawings in which: [Fig.1] [Fig.1] is a partial schematic axial cross-sectional view 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 pad braking system which is shown 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 rim brake system. Detailed description of the invention
[0022] Figure 1 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 twin-body type and comprises a low-pressure body and a high-pressure body.
[0025] The turbomachine 10 includes a gas generator which includes 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 housing. The stators of the high-pressure compressor 14 and 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 housing. The stators of the low-pressure compressor 12 and 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 housing 38. This intermediate housing 38 is located axially between the compressors 12, 14.
[0029] These bearings 24, 32 are preferably housed in a lubrication chamber E in which an oil mist is present. The oil-laden air contained in this chamber 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 freed 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 housing 44. This exhaust housing 44 is located axially downstream of the turbines 18, 20.
[0031] The low-pressure shaft 28 is further connected, either directly or via a mechanical reducer, to a drive shaft 46 of a blower 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 blower 48 rotates inside a blower housing 50 which can be connected to the aforementioned intermediate housing 38.
[0033] Fig. 2 illustrates a torsion phenomenon of a shaft, such as a low-pressure shaft 28, during an FBO type failure for example.
[0034] This failure results in significant imbalance and radial eccentricity of the blower 48 with the housing 50 surrounding 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 drive the low-pressure shaft 28. Consequently, the low-pressure shaft 28 is subjected to a very significant torsional overtorque and twists. The angle of twist during such an event can reach high values, up to several tens of degrees. This angle is related to a high torque in the low-pressure shaft 28, which in most applications corresponds to the design load case for this shaft 28.
[0035] The invention solves this problem by means of a system that reduces the maximum torsional torque experienced by the shaft in extreme cases, thereby reducing the stress on its design. This system is an automatic or passive pad braking system. In this 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 during operation.
[0036] For this purpose, the low-pressure shaft 28 is traversed axially by a tube 52.
[0037] Advantageously, this tube 52 is a degassing tube, that is to say a tube suitable for conveying the aforementioned oil-free 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 includes an upstream end 52a fixed in rotation to 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 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 stroke.
[0042] The downstream end 28b of the shaft 28 is connected to the downstream end 52b of the tube 52 by the automatic pad braking system 54.
[0043] This braking system 54, one embodiment of which is illustrated in Figures 3 and 4, can adopt a non-functional retracted position ([Fig. 3]) in which the pads 56 are at a radial distance 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.
[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 is subjected to 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 stroke [3] between the shaft 28 and the tube 52 is for example between 1 and 10°.
[0047] In the example shown in [Fig. 1], the stator 58 is formed by the bearing support 42 or a part connected to this bearing support. As will be described below, the stator 58 corresponds to the track on which the braking system 58 will exert pressure when the system is actuation.
[0048] In a preferred embodiment, the braking system 54 comprises a pair of elongated arms 60. Each arm 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 arm 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 can be positioned tangentially with respect 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 include a radially external bearing face 56a which has a convex curved shape. This face is configured to bear against an internal cylindrical surface of the stator 58 in the example shown.
[0053] Each of the skates 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 a non-functional position ([Fig. 3]). If the shaft 28 is subjected to a torsional force below 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 system is actuation triggered by a position differential between the shaft 28 and the tube 52. A rotational phase shift is created between the two, which results in the movement of the connecting rods 62 and the pads 56. As soon as the shaft 28 is subjected to a torsional force greater than the threshold, the arms 60 are deployed and the pads 56 take support on the stator to brake the shaft and reduce the torque and the angle of torsion which this shaft is subjected to.
[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 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
Demands
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 includes an upstream end (52a) rotationally fixed to an upstream end (28a) of the shaft (28), characterized in that the shaft (28) includes a downstream end (28b) which is free to rotate relative to a downstream end (52b) of the tube (52) over a predetermined angular stroke (|3), and which is connected to this downstream end (52b) of the tube (52) by an automatic brake system with pads (54),the braking system (54) being mobile from a non-functional retracted position in which the pads (56) are at a radial distance from a stator (58) which surrounds the downstream end (28b) of the shaft (28), when the shaft (28) is subjected to a torsional force about 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, wherein the stator (58) is a bearing support (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, wherein the braking system (54) comprises a pair of elongated arms (60), 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, wherein the arms (60) are diametrically opposed with respect to said longitudinal axis (X).
5. Turbomachine (10) according to claim 3 or 4, wherein the arms (60) are positioned tangentially with respect to a circular conference centered on said longitudinal axis (X).
6. Turbomachine (10) according to any one of claims 3 to 5, wherein each of the skids (56) has a curved shape and includes a radially external bearing face (56a) which has a convex curved shape.
7. Turbomachine (10) according to claim 6, wherein each of the skids (56) has an angular extent (a) greater than or equal to 20° about said longitudinal axis (X).
8. Turbomachine (10) according to any one of the preceding claims, wherein said angular stroke (|3) is between 1 and 10°.
9. Turbomachine (10) according to any one of claims 1 to 8, wherein 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 any one of claims 1 to 8, wherein 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 any one of the preceding claims, wherein 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, wherein the tube (52) is a degassing tube whose upstream end (52a) is adapted to collect oil-free air from a lubrication chamber (E) of said at least one bearing (32) of the upstream end (28a) of the shaft (28).
13. Turbomachine (10) according to any one of the preceding claims, said turbomachine (10) being double-body and comprising a low-pressure body and a high-pressure body, said shaft (28) being part of the low-pressure body.