TURBOMACHINE D’AERONEF

Abstract

Turbomachine (10) for an aircraft, comprising: - a gas generator (12) comprising a shaft (14) rotatable about an axis (X), - a fan (16) driven by the shaft (14) of the gas generator (12) about said axis (X), this fan (16) comprising a hub (28) and blades (30) which extend from the hub (28) radially outwards, the blades (30) each comprising a root (32) connected to the hub (28) and a free tip (34), - an annular casing (18) which surrounds the fan (16) with radial clearances (J), and - a detection device (50) which is permanently installed in said casing (18) and which is capable of detecting the tips (34) of the blades (30), and - a unit (58) for calculating a rotation speed of the blower (16) from information communicated by the detection device (50). Figure for the abstract: Figure 2

Description

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

[0001] The present invention relates to an aircraft turbomachine, as well as to an aircraft equipped with this turbomachine. Technical background

[0002] An aircraft turbomachine typically comprises from upstream to downstream, with reference to the flow of gases in the turbomachine in operation, a propulsion fan, at least one compressor, an annular combustion chamber, at least one turbine, and a combustion gas exhaust nozzle.

[0003] The turbine rotor is connected by a shaft to a compressor rotor to form a rotating body.

[0004] In the case of a twin-spool turbojet engine, respectively high pressure and low pressure, the turbojet engine comprises from upstream to downstream a low pressure compressor, a high pressure compressor, the combustion chamber, a high pressure turbine and a low pressure turbine.

[0005] The high pressure body comprises the rotors of the high pressure compressor and the high pressure turbine, and the high pressure shaft connecting these rotors.

[0006] The low pressure body comprises the rotors of the low pressure compressor and the low pressure turbine, and the low pressure shaft connecting these rotors. The low pressure shaft rotates the fan shaft, either directly or via a mechanical reducer.

[0007] The bodies and the rotors rotate around the same axis which is generally the longitudinal axis of the turbomachine.

[0008] The fan comprises a hub connected to its drive shaft, and blades which extend from the hub radially outward. The blades each comprise a root connected to the hub and a free apex opposite the root.

[0009] The fan is shrouded as opposed to a propulsion propeller which is not shrouded. The fan is thus surrounded by a casing, called a fan casing, which has an internal cylindrical surface separated by radial clearances from the tips of the fan blades.

[0010] The main function of the fan blades is to bring the air entering the turbomachine to a certain compression level, and with a certain flow rate, so as to satisfy aerodynamic objectives of thrust, specific consumption and operability (float, pumping).

[0011] It is important to know precisely the rotation speed of the blower, in particular to deduce the rotation speed of the shaft which drives it, which is generally the low pressure shaft.

[0012] In the current technique, this rotation speed is determined using a probe which is carried by a stator of the turbomachine, downstream of the fan, and which cooperates with a phonic wheel integral in rotation with the low pressure shaft. The phonic wheel comprises an annular row of teeth around the axis and the probe makes it possible to measure the number of teeth of the wheel which pass in front of it and to deduce the rotation speed of the shaft.

[0013] In practice, the probe is located at a longitudinal end of an elongated piece of equipment which is relatively bulky and which is mounted through a tubular service passage arm which crosses a vein of the turbomachine.

[0014] This technology is relatively complex both from a sizing point of view and from an implementation point of view. Linked to the complexity of this technology, the clearance between the probe and the phonic wheel has very strict requirements, particularly with very tight clearance tolerances in order to ensure the correct operation of the measurements. These requirements therefore impose different checks at different stages of assembly and generate significant costs linked to these checks.

[0015] The invention makes it possible to respond to this problem in a simple, effective and economical manner. Summary of the invention

[0016] The invention thus proposes a turbomachine for an aircraft, comprising:

[0017] - a gas generator comprising a shaft movable in rotation around an axis,

[0018] - a blower driven by the shaft of the gas generator around said axis, this fan comprising a hub and blades which extend from the hub radially outwards, the blades each comprising a root connected to the hub and a free apex opposite the root,

[0019] - an annular casing which surrounds the fan and extends around the free tops blades, the casing comprising an internal cylindrical surface which is separated from the tips of the blades by radial clearances,

[0020] characterized in that it further comprises:

[0021] - at least one detection device which is permanently implanted in said casing and which is capable of detecting the tips of the blades when they pass successively in line with this device when the fan rotates around the axis, and

[0022] - a unit for calculating a fan rotation speed from information communicated by the detection device.

[0023] The invention thus proposes to provide one or more devices for detecting the tips of the fan blades so as to then calculate the rotation speed of the fan. For example, the number of blade tip passes detected makes it possible, from the number of fan blades, to determine the number of fan revolutions over a period of time and therefore to deduce the fan rotation speed.

[0024] In view of the issues raised, the advantages of such technology are as follows: • cost savings (parts and assembly labor), • mass gain, • limitation of risk during assembly compared to the use of the aforementioned equipment.

[0025] 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 turbomachine includes several detection devices distributed around the axis; the turbomachine comprises at least two detection devices located axially one behind the other; the or each detection device comprises at least one capacitive sensor; said at least one capacitive sensor has a generally elongated shape and extends in a radial direction relative to the axis; said at least one capacitive sensor has a sensing end which is flush with said inner surface of the housing; the casing comprises a stack of several annular layers comprising, from the outside to the inside, a support wall, a honeycomb structure, a carbon layer and an abradable coating, the or each detection device passing through the abradable coating, the carbon layer and at least a portion of the honeycomb structure; the or each detection device is connected to a wireless communication system.

[0026] The present invention also relates to an aircraft comprising at least one turbomachine as described above, and a cockpit equipped with a display system capable of displaying the rotation speed calculated by the calculation unit. Brief description of the figures

[0027] The invention will be better understood and other details, characteristics and advantages of the invention will appear more clearly on reading the following description given by way of non-limiting example and with reference to the appended drawings in which:

[0028] [Fig-1] [Fig.l] is a partial schematic view in axial section of a tur- aircraft machine according to the invention,

[0029] [Fig.2] [Fig.2] is an enlarged view of part of [Fig.l] and shows a detection device, and

[0030] [Fig.3] [Fig.3] is a partial schematic perspective view of a fan casing and a fan blade, the casing being equipped with detection devices. Detailed description of the invention

[0031] [Fig.l] shows a part of an aircraft turbomachine 10, and in particular a front or upstream part of this turbomachine.

[0032] Conventionally, a turbomachine 10 comprises:

[0033] - a gas generator 12 comprising a shaft 14 movable in rotation around an axis X,

[0034] - a blower 16 driven by the shaft 14 of the gas generator 12 around the axis X, and

[0035] - an annular casing 18 which surrounds the fan 16.

[0036] The gas generator 12 may comprise one or more rotating bodies, and for example a low-pressure body and a high-pressure body. In the example shown, the gas generator 12 comprises a low-pressure compressor 20 located downstream of the blower 16 and a high-pressure compressor 22 located downstream of the low-pressure compressor 20 and axially separated from the latter by an intermediate casing 24 or inter-compressors.

[0037] Although this is not visible in the drawing, the turbomachine 10 successively comprises, downstream of the high-pressure compressor 22, an annular combustion chamber, a high-pressure turbine and a low-pressure turbine.

[0038] The intermediate casing 24 comprises radial arms 26 which connect the gas generator 10 to the casing 18

[0039] The air flow F1 which enters the turbomachine 10 and which passes through the fan 16 is divided into two by an annular separator 28. A first radially internal air flow F2, called the primary flow, flows into the gas generator 12 from the low-pressure compressor 20 to the low-pressure turbine. A second radially external air flow F3, called the secondary flow, flows around the gas generator 12, through the arms 26 of the intermediate casing 24.

[0040] The fan 16 comprises a hub 28 and blades 30 which extend from the hub 28 radially outward. Each of the blades 30 comprises a root 32 connected to the hub 28, and a tip 34 which is free and which is opposite the root 32.

[0041] The casing 18 extends around the free tips 34 of the blades 30 and comprises an internal cylindrical surface 36 which is separated from the tips 34 of the blades 30 by radial clearances J better visible in [Fig.2].

[0042] The casing 18 and its surface 36 have a continuous angular extent around the axis X while the tips 34 of the blades 30 each have a precise angular position around the axis X even if this position varies when the fan 16 rotates.

[0043] In the context of the present application, the tip 34 of each of the blades 30 is separated from the casing 18 and the fan 16 by a radial clearance J. There are therefore as many radial clearances J as there are blades 30. However, a (single) radial clearance between the fan 16 and the casing 30 can be defined as being the average of the radial clearances J between the tips 34 of the blades 30 and the casing 18.

[0044] As seen in [Fig.2], the casing 18 comprises a stack of annular layers.

[0045] From the outside to the inside, the casing 18 comprises a support wall 38 generally made of metal, a cellular structure 40, for example made of honeycomb, a carbon layer 42 formed for example by a superposition of folds or fabrics, and an abradable coating 44 which defines the aforementioned internal surface 36 of the casing 18.

[0046] According to the invention, the turbomachine 10 further comprises:

[0047] - at least one detection device 50 which is permanently implanted in the casing 18 and which is capable of detecting the tips 34 of the blades 30 when they pass successively in line with this device 50.

[0048] - a unit 58 for calculating a rotation speed of the fan 16 from information communicated by the detection device 50.

[0049] The turbomachine 10 may comprise several detection devices 50 distributed around the X axis.

[0050] As seen in [Fig.3], the turbomachine 10 may comprise at least two detection devices 50 located axially one behind the other.

[0051] Preferably, the or each detection device 50 comprises at least one capacitive sensor 52.

[0052] A capacitive sensor is a sensor that uses the capacitive effect to detect a small distance variation. It is very generally made with a disc-shaped electrode surrounded by a guard ring insulated from the central electrode. The electrode forms a planar capacitor with the conductive part to be measured. It is also found in the form of two nested combs, which increases the capacitive surface when a thin sensor is required. The capacitive sensor works on the basis of a variation in the electric field which normally must remain stable. When the capacitor detects an object in its field, oscillations are induced, which causes a change in the capacitor's capacitance.

[0053] Capacitive sensors have a number of advantages. They can detect all materials. They are contactless and therefore virtually wear-free. They are also insensitive to disturbances and impurities such as dust. example.

[0054] In the example illustrated in [Fig.2], the or each capacitive sensor 52 has a generally elongated shape and extends in a radial direction relative to the X axis.

[0055] The or each capacitive sensor 52 has a sensing end 54 which can be flush with the internal surface 36 of the casing 18.

[0056] The or each capacitive sensor 52 can pass through the abradable coating 44, the carbon layer 42 and at least a portion of the honeycomb structure 40.

[0057] The or each detection device 50 is preferably connected to a wireless communication system 56.

[0058] The present invention also relates to an aircraft comprising at least one turbomachine 10 as described above.

[0059] The aircraft further comprises a cockpit 60 equipped with a display system 62 capable of displaying the rotation speed calculated by the calculation unit 51. The display system 62 communicates with the or each detection device 50 using the wireless communication system 56 for example.

Claims

Claims

1. Turbomachine (10) for an aircraft, comprising: - a gas generator (12) comprising a shaft (14) rotatable about an axis (X), - a fan (16) driven by the shaft (14) of the gas generator (12) about said axis (X), this fan (16) comprising a hub (28) and blades (30) which extend from the hub (28) radially outwards, the blades (30) each comprising a root (32) connected to the hub (28) and a free tip (34) opposite the root (32), - an annular casing (18) which surrounds the fan (16) and extends around the free tips (34) of the blades (30), the casing (18) comprising an internal cylindrical surface (36) which is separated from the tips (34) of the blades (30) by radial clearances (J),characterized in that it further comprises: - at least one detection device (50) which is permanently installed in said casing (18) and which is capable of detecting the tips (34) of the blades (30) when they pass successively in line with this device (50) when the fan (16) rotates around the axis (X), and - a unit (58) for calculating a rotation speed of the fan (16) from information communicated by the detection device (50).,

2. Turbomachine (10) according to claim 1, in which it comprises several detection devices (50) distributed around the axis (X).

3. Turbomachine (10) according to claim 1 or 2, in which it comprises at least two detection devices (50) located axially one behind the other.

4. Turbomachine (10) according to one of the preceding claims, in which the or each detection device (50) comprises at least one capacitive sensor (52).

5. Turbomachine (10) according to claim 4, wherein said at least one capacitive sensor (52) has a generally elongated shape and extends in a radial direction relative to the axis (X).

6. A turbomachine (10) according to claim 4 or 5, wherein said at least one capacitive sensor (52) has a sensing end (54) which is flush with said inner surface (36) of the casing (18).

7. Turbomachine (10) according to one of the preceding claims, in which the casing (18) comprises a stack of several anti-

8.

9. nular devices comprising from the outside to the inside, a support wall (38), a honeycomb structure (40), a carbon layer (42) and an abradable coating (44), the or each detection device (50) passing through the abradable coating (44), the carbon layer (42) and at least a portion of the honeycomb structure (40). Turbomachine (10) according to one of the preceding claims, in which the or each detection device (50) is connected to a wireless communication system (56). Aircraft comprising at least one turbomachine (10) according to one of the preceding claims, and a cockpit (60) equipped with a display system (62) capable of displaying the rotation speed calculated by the calculation unit (58).

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