System for measuring axial and radial play at the tip of a turbomachine blade

Abstract

This disclosure relates to a rotor blade (31) of a turbomachine component, an axial direction being defined by an axis of rotation of the rotor, a radial direction being defined as any direction perpendicular to the axial direction and passing through the axis of rotation of the rotor, a radially external surface (9) at the apex of the blade (31) having an axially upstream flap (5) and an axially downstream flap (6) in a gas flow direction along the axial direction in the turbomachine component when the turbomachine component is in operation, a plurality of targets (7) being arranged in relief on the radially external surface (9) of the blade between the axially upstream flap and the axially downstream flap of the blade, at least two of the targets (7) not being arranged in parallel directions. Figure for the abstract: Fig. 3

Description

Title of the invention: System for measuring axial and radial play at the tip of a turbomachine blade technical field

[0001] This disclosure relates to the measurement of blade displacements during the operation of a turbomachine. More specifically, it relates to a turbomachine component equipped with a blade displacement measurement system, as well as a method for measuring such displacements. STATE OF THE ART

[0002] A turbomachine has a main direction extending along a longitudinal axis, and typically comprises, from upstream to downstream in the direction of gas flow, a blower, a low-pressure compressor, a high-pressure compressor, a combustion chamber, a high-pressure turbine, and a low-pressure turbine.

[0003] By convention, in this application, the terms "upstream" and "downstream" are defined with respect to the direction of airflow in the turbine, i.e., from left to right in [Fig. 1]. Similarly, by convention in this application, the terms "inside" and "outside," and "internal" and "external," are defined radially with respect to the axis of the turbomachine. For a given turbomachine component, such as, for example, a compressor or a turbine, the component extends along a principal direction, also called the axial direction, defined along a longitudinal axis. A radial direction is defined as any direction perpendicular to and passing through the longitudinal axis. A circumferential direction is defined as any direction perpendicular to and not passing through the longitudinal axis.

[0004] By referring to the attached [Fig.1], one can see an example of a turbine 1 for a turbomachine conforming to the prior art.

[0005] This turbine comprises several successive stages, each comprising a downstream distributor 2 and an upstream blade wheel 3.

[0006] Each distributor 2 comprises a radially internal annular platform 21 and a radially external annular platform 22 coaxial, between which extend radial or substantially radial vanes 23, regularly spaced over the entire circumference of said platforms.

[0007] Each distributor 2 is radially attached outwards to an external housing 4 of the turbine.

[0008] The set of distributors 2 forms the fixed part of the motor called the "stator".

[0009] Each blade wheel 3 comprises a disc 30 carrying radial or substantially radial blades 31 on its outer periphery, the discs 30 of the different wheels being coaxially connected to each other and to a drive shaft by appropriate means, so as to form the "rotor" of the turbine (see [Fig.1]).

[0010] To allow the rotor blades 31 to rotate freely around the axis of the rotor disk 30, a radial clearance is provided between the rotor blades 31 and a radially internal surface of the outer casing 4. The value of this radial clearance may vary during the operation of the turbomachine, particularly when the blades 31 undergo a different thermal expansion than the outer casing 4. However, the value of this clearance must fall within ranges defined during the turbomachine design phase. Thus, it is necessary to have both sufficient radial clearance to ensure that the blades 31 do not damage the internal surface of the casing 4, and sufficient clearance to avoid excessive aerodynamic losses.During the construction and maintenance of the turbomachine, the radial clearances between the rotor blades 31 and the outer casing 4 can be compared to the ranges of values ​​specified in the design, in order to ensure the correct positioning of the blades relative to the casing.

[0011] Similarly, in operation of the turbomachine, the rotor blades 31 can move axially, and it is necessary to know the value of this axial displacement so as to ensure that it remains within a predetermined range of value during the design of the turbomachine.

[0012] Several methods for measuring radial clearances and axial displacements of blades are commonly used in the prior art.

[0013] To detect a variation in axial displacement, sensors can be used in front of the blades. These sensors detect an electrical capacitance that can be converted into a distance between the blade and the sensor. Due to the size of such sensors, it is difficult to integrate them into the external housing, so they are generally placed on a shaft of the turbomachine. The axial displacement detected by these sensors therefore does not correspond to the blade tip displacement that one wishes to measure, and it is necessary to extrapolate a value for the axial displacement at the blade tip from the displacement measured by the sensor, which is necessarily less precise than directly measuring the desired displacement.

[0014] To overcome this problem, it is known to place, in addition to or instead of the axial play sensor, a wear indicator made of abradable material on the inner surface of the housing. The blades then erode the wear indicator through mechanical friction during the operation of the turbomachine. However, such a method has limited accuracy depending on the type of abradable material used. Furthermore, the axial displacement can only be determined after the turbine has been disassembled to inspect the abradable wear indicator, and the axial displacement of the blades remains unknown during the time interval between two disassemblies. It is therefore impossible to know the axial displacement corresponding to a given flight phase of the turbomachine.

[0015] To detect a variation in radial clearance, a known method consists of placing a distance sensor opposite a turbine blade tip on the turbine housing. The sensor then detects an electrical capacitance, which can be converted into a distance corresponding to a radial air gap between the tip and the sensor. It is necessary to provide a projection or indentation on the tip to allow the sensor to detect the passage of the blade due to the variation in the air gap distance. The irregularity represented by this projection or indentation causes undesirable aerodynamic losses, and therefore a decrease in turbomachine performance. Furthermore, if axial displacement of the blades has occurred during turbine operation, the radial clearance sensor may no longer be positioned opposite the same part of the blades, and the measurement taken by the sensor is affected.When axial displacement is significant, a shim located axially upstream or downstream of the shim for which the sensor measures axial clearance - for example, a shim belonging to a blade of a stage further upstream or further downstream of the turbomachine component - may further interfere with the measurement performed by the sensor.

[0016] Furthermore, the integration of two separate sensors for measuring radial play and axial displacement of the blades uses a significant portion of the available space in the turbine. Description of the invention

[0017] An object of the invention is to allow the measurement of both a radial clearance between rotor blades and an external housing of a turbomachine component, and an axial displacement of the blades.

[0018] Another object of the invention is to allow a more precise measurement of the axial displacement at the end of the blade.

[0019] Another object of the invention is to allow a more precise measurement of the radial play despite an axial displacement of the blades.

[0020] Another object of the invention is to allow measurement of an axial displacement of the blades without having to dismantle the turbomachine.

[0021] Another object of the invention is to reduce the integration space required for measuring the displacements of the blades in the turbomachine.

[0022] In order to achieve the objectives mentioned above, it is proposed, according to a first aspect of this disclosure, to have a rotor blade of a turbomachine component, an axial direction being defined by an axis of rotation of the rotor, a radial direction being defined as any direction perpendicular to the axial direction and passing by the axis of rotation of the rotor, a radially external surface at the top of the blade having an axially upstream flap and an axially downstream flap in a direction of gas flow along the axial direction in the turbomachine component when the turbomachine component is in operation, a plurality of targets being arranged in relief on the radially external surface of the blade between the axially upstream flap and the axially downstream flap of the blade, at least two of the targets not being arranged in parallel directions.

[0023] Thus, it is possible to measure precisely and in real time both the radial clearance between the blades and the internal surface of the casing and the axial displacement of the blades, using the same sensor, with a limited integration space in the turbomachine.

[0024] According to one embodiment, a projection of the targets onto the radially external surface extends in a substantially straight manner.

[0025] According to one embodiment, the targets are protruding parts of the radially external surface in the direction of the radially internal surface of the external stator housing.

[0026] According to one embodiment, at least one of the targets extends substantially along the axial direction.

[0027] According to one embodiment, a maximum thickness of the targets in the radial direction is at least 2.5 millimeters.

[0028] According to one embodiment, at least one of the targets has a first surface in direct contact with the radially external surface of the blade, the first surface extending substantially along the radial direction.

[0029] Another aspect of this disclosure relates to a turbomachine component comprising: - an external stator housing, and - a rotor equipped with a blade as described above, the rotor being movable relative to the stator,

[0030] the turbomachine component further comprising a capacitive sensor disposed on a radially internal surface of the external casing, the capacitive sensor being arranged so as to allow the measurement of a distance between the capacitive sensor and each target at least during a passage of the target in relation to the capacitive sensor in the radial direction.

[0031] According to one embodiment, the turbomachine component is chosen from a compressor stage or a turbine stage.

[0032] According to one embodiment, the capacitive sensor comprises a cylindrical electrode.

[0033] Another aspect of this disclosure relates to a turbomachine comprising a blade as described above or a turbomachine component as described above.

[0034] Another aspect of this disclosure relates to an aircraft comprising a turbomachine as described above. DESCRIPTION OF THE FIGURES

[0035] Other features, purposes and advantages will become apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings on which:

[0036] Fig. 1 schematically illustrates a turbomachine component according to the prior art;

[0037] Fig. 2 schematically illustrates a view along a circumferential direction of a blade tip of a turbomachine component according to one aspect of the present disclosure;

[0038] Fig. 3 schematically illustrates a view along a radial direction, and from a radially external position, of a blade tip of a turbomachine component according to one aspect of the present disclosure;

[0039] Fig. 4a is a graph representing a time evolution of the distance between a capacitive sensor and a blade apex during blade rotation for two distinct axial positions of the blade relative to the capacitive sensor;

[0040] Fig. 4b is a graph representing a time evolution of the distance between a capacitive sensor and a blade tip during blade rotation for two distinct values ​​of a radial clearance between the capacitive sensor and the blade tip;

[0041] Figure 5 schematically represents an aircraft equipped with a turbomachine component according to one aspect of this disclosure.

[0042] Throughout the figures, similar elements bear identical references.

[0043] DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0044] According to a first aspect, a turbomachine comprises a plurality of components, including in particular one or more compressors and one or more turbines. Figure 1 represents such a turbomachine component, namely a turbine. However, a turbomachine component as defined herein may include any part of a turbomachine comprising a stationary part and a part rotating relative to the stationary part, and for which it may be necessary to measure a variation in axial displacements and radial clearances of the rotating part relative to the stationary part. The rotating part may also, but is not limited to, be a fan stage, a shaft, a disk, a rotating ring, or a shell.

[0045] Figures 2 and 3 represent a radially external surface 9 at the apex of a blade 31 of a blade wheel 3 of a turbine or turbomachine compressor. The radially external surface comprises a blade 5 arranged axially upstream and a blade 6 arranged axially downstream - hereinafter referred to as the "upstream blade" and "downstream blade" respectively, the two blades 5, 6 extending towards an internal surface of an external casing 4 of the turbomachine component.

[0046] A capacitive sensor 8 is fixed relative to the inner surface of the outer housing 4. The capacitive sensor 8 comprises at least one electrode and is connected to information processing means. The capacitive sensor can detect the transit time of a target as well as the distance between the target and its electrode. The radially external surface 9 of the blade 31 comprises at least two targets 7, extending in relief in the space between the upstream 5 and downstream 6 swashplates, these two targets not being parallel. At least a portion of each target 7 has a radial distance from the capacitive sensor 8, when this portion of the target 7 is opposite the capacitive sensor 8, that differs from a radial distance between the radially external surface 9 of the blade and the capacitive sensor 8.Thus, during a rotation of the rotating part of the turbomachine component, the capacitive sensor 8 detects a variation in radial distance when a target 7 passes in front of the capacitive sensor 8.

[0047] According to a first embodiment, shown in Figures 2 and 3, the raised targets 7 are protruding parts of the radially external surface 9, that is to say, at least a part of each target 7 has a radial distance with the capacitive sensor 8, when this part of the target 7 is opposite the capacitive sensor 8, that is less than the radial distance between the radially external surface 9 of the blade and the capacitive sensor 8. This embodiment does not require any recessing in the radially external surface 9, and therefore minimizes aerodynamic leakage between the external casing 4 and the blade 31. Thus, the impact of the presence of the targets 7 on the aerodynamic performance of the turbomachine component is minimized.For this embodiment, the passage of a target 7 in front of the capacitive sensor 8 is identified by means of a temporary decrease in the radial distance between the tip of the blade and the sensor when the target 7 passes in front of the sensor 8.

[0048] The targets 7 may include two first surfaces 13 in direct contact with the radially external surface 9 and a second surface 14 joining the first two surfaces 13. The second surface 14 may extend substantially parallel to the radially external surface 9.

[0049] According to another embodiment, the raised targets 7 are indentations made by removing material from the radially external surface 9, i.e., at least a part of each target 7 has a radial distance from the capacitive sensor 8, when this part of the target 7 is opposite the capacitive sensor 8, greater than the radial distance between the radially external surface 9 of the blade and the capacitive sensor 8. For this embodiment, the passage of a target 7 in front of the capacitive sensor 8 is identified by means of a temporary increase in the distance between the top of the blade and the sensor when the target 7 passes in front of the sensor 8.

[0050] The capacitive sensor 8 is configured to measure a radial clearance 11 between its electrode and the targets 7. A variation in radial clearance 11 is therefore seen by the capacitive sensor 8 as a variation in the distance between a target 7 and the electrode of the capacitive sensor 8. Regardless of the nature of the raised targets 7 - that is, whether they are protruding parts of the radially external surface 9 or indentations made in the radially external surface 9, as described previously - a decrease (respectively increase) in the radial clearance 11 is identified by the capacitive sensor 8, because the distance between a target 7 and the capacitive sensor 8 when the target 7 passes in front of the sensor 8 decreases (respectively increases).

[0051] Figure 4a also illustrates this phenomenon. Curves I and II represent the variation in radial distance between the capacitive sensor 8 and the tip of the blade 31 when the blade is in motion. Curve I corresponds to the case where the radial clearance 11 between the tip of the blade 31 and the capacitive sensor 8 takes on a first value, while curve II corresponds to the case where the radial clearance 11 between the tip of the blade 31 and the capacitive sensor 8 takes on a second value, lower than the first value – the blade 31 having moved closer to the outer casing 4.

[0052] Furthermore, an axial displacement 10 of the blade 31a results in the capacitive sensor 8 not being positioned opposite the same part of the targets 7. Indeed, the sensor electrode has an axial position relative to the targets that can vary between the upstream blade 5 and the downstream blade 6. When this relative axial position varies, because the targets 7 do not extend parallel to each other, the circumferential distance 12 between the two targets 7 seen by the capacitive sensor 8 necessarily changes. More specifically, it is possible to establish a direct correlation between this circumferential distance 12 and the axial position of the targets 7, so that an axial displacement 10 of the blades can be precisely measured, both upstream and downstream.

[0053] For example, with reference to [Fig. 3], two targets 7 extend over the radially external surface 9 with a circumferential distance 12 increasing between them from upstream to downstream. If the capacitive sensor 8 is located opposite a first axial position Pa of the radially external surface 9, the circumferential distance 12 has a value of 12.1. If, during operation of the turbomachine component, the relative axial position of the capacitive sensor 8 with respect to the radially external surface 9 changes so that the capacitive sensor 8 comes to be opposite From a second axial position Pa2 of the radially external surface 9, the circumferential distance 12 between the two targets 7 then has a value of 12.2, greater than the value 12.1. The time between the successive passage of the two targets 7 in front of the electrode is therefore longer at the second axial position Pa2 than at the first axial position Pa[, the variation of this time allowing us to deduce the relative axial displacement of the blade 31 with respect to the capacitive sensor 8.

[0054] Figure 4b also illustrates this phenomenon. Curves I and II represent the variation in radial distance between the capacitive sensor 8 and the tip of the blade 31 when the blade is in motion. Curve I corresponds to the case where the capacitive sensor 8 is at the first axial position Pab, while curve II corresponds to the case where the capacitive sensor 8 is at the second axial position Pa2. It can be seen that, for the second axial position Pa2, the transit time between the two targets 7 is longer than for the first axial position Pab.

[0055] Thus, the assembly formed by the capacitive sensor 8 and the targets 7 makes it possible to determine both the axial displacement 10 of the blades 31 relative to the outer casing 4, and the radial clearance 11 between the sensor 8 and the tips of the blades 31. This assembly occupies a small space in the turbomachine component, compared to systems comprising separate components for measuring the radial clearance 11 and the axial displacement 10. No abradable material is required to determine the variation of the radial clearance 11. Furthermore, the capacitive sensor 8 can be selected with a predetermined frequency so as to obtain measurements of the axial displacement 10 and the radial clearance 11.

[0056] A projection of the targets 7 onto the radially external surface 9 can extend substantially straight, such that there is a linear variation in the circumferential distance 12 between two targets 7 along the axial direction. In this case, a principal axis X7 of each target 7 defines an angle α with the axial direction, preferably between 0° and 80°, preferably 0° to 45°. It is necessary to avoid being close to 90° because this results in a target 7 in the plane perpendicular to the motor axis, and it is no longer possible to measure the rotor speed; only an axial position is measured (which is either the axial position of the capacitive sensor 8 or a different position). The closer the angle α is to 90°, but not to 90°, the worse the measurement accuracy, because the dimension of the target 7 along the circumferential direction becomes very large compared to its effective width.However, the targets are not necessarily placed symmetrically with respect to the axial direction; in fact, there is no advantage to being symmetrical. The aim is rather to adapt to the available space at the blade tip, on the radially external surface 9, or on the rotor portion. It is possible to have a target 7 extending along the axial direction and . A target presenting a non-zero angle α with the axial direction. It therefore seems relevant to discuss the angle between two targets 7. The angle between the two targets 7 must be greater than at least 10° to obtain an effective measurement of axial displacement 10 (the targets 7 must move distinctly apart along the axial direction to associate an axial displacement 10 with a separation between two targets). Space on a blade, on a radially external surface 9, or on a portion of the rotor may be limited, in which case going beyond an angle between two targets 7 greater than 160°, preferably 135°, does not seem appropriate. An angle between 45° and 90° facilitates the interpretation of measurements while ensuring that the circumferential dimension of the targets remains acceptable.

[0057] A maximum thickness 16 of the targets 7 in the radial direction can be at least 2.5 millimeters. Thus, the variation of the radial gap 11 between, on the one hand, the electrode 8 and the radially external surface 9 and, on the other hand, between the electrode 8 and the targets 7 is sufficiently large to ensure the detection of the passage of the targets 7 through the electrode 8.

[0058] A maximum dimension 15 of the targets 7 in the circumferential direction can further be between 2 millimeters and 10 millimeters. The maximum dimension 15 is chosen in particular according to the frequency of the capacitive sensor 8 and the rotational speed of the blade 31, as well as the dimensions of the blade 31, the radially external surface 9 and the rotor comprising the blade 31.

[0059] In particular, a target detection can be considered validly confirmed when at least 3, preferably at least 5 successive target detections are carried out by the capacitive sensor 8.

[0060] The use of a capacitive sensor 8 with a sufficiently high frequency allows for the real-time measurement of the radial clearance 11 and the axial displacement 10 of the blades. The frequency of the capacitive sensor 8 can be, in particular, between 10 Hz and 400 Hz. Specifically, it is therefore possible to study the variations in these distances during the operation of the turbomachine, according to its operating conditions. It is not necessary to disassemble the turbomachine component to determine these variations.

[0061] In one embodiment, the sensor 8 comprises a cylindrical electrode. Compared to a non-circular electrode with edges, for example a polygonal electrode, this avoids edge effects at the electrode corners, which could distort the signal being measured. Such edge effects are particularly problematic because both an axial displacement 10 and a radial clearance 11 are being measured, and these effects can therefore occur in several directions.

[0062] According to one embodiment, at least one of the targets 7 extends substantially along the axial direction, that is to say, the angle α between the axis X7 of said target and the axial direction is 0°. At least one other of the targets 7 then extends along a direction not parallel to the axial direction, with a non-zero angle α. When the circumferential distance between two successive blade tips is small, this allows minimizing the circumferential distance required for target integration 7.

[0063] It is also possible to foresee that the first surface 13 of the targets 7 extends substantially in the radial direction. This also facilitates the detection of the targets 7 by the electrode 8, by ensuring an abrupt variation of the radial gap 11 seen by the electrode 8.

[0064] According to one embodiment, and as shown in [Fig.3], the targets 7 extend substantially from a downstream surface 51 of the upstream slat 5 to an upstream surface 61 of the downstream slat 6. Thus, the targets 7 cover, in the axial direction, all the available space between the slats 5, 6 on the radially external surface 9, and the capacitive sensor 8 can detect the passage of the targets 7 regardless of the axial position at which it is located in the space defined between the two slats 5, 6.

[0065] Another aspect of this disclosure relates to a blade 31 comprising targets 7 as defined above. Such a blade can be used in a turbomachine component equipped with an external housing 4 on an internal surface of which a capacitive sensor 8 is disposed, the capacitive sensor 8 then allowing the measurement of the radial clearance 11 between the blade tip and the capacitive sensor 8 as well as the measurement of the axial displacement 10 of the blade 31.

[0066] Another aspect of this disclosure relates to a turbomachine 18 comprising a turbomachine component as described above. This may include, in particular, a compressor or turbine stage.

[0067] Another aspect of this disclosure, illustrated in [Fig.5], relates to an aircraft 17 equipped with a turbomachine 18 as described in the preceding paragraph.

Claims

Demands

1. Turbomachine component comprising: - an external stator housing (4), and - a rotor equipped with a blade (31), the rotor being movable relative to the stator, an axial direction being defined by an axis of rotation of the rotor, a radial direction being defined as any direction perpendicular to the axial direction and passing through the axis of rotation of the rotor, a radially external surface (9) at the apex of the blade (31) having an axially upstream flap (5) and an axially downstream flap (6) in a direction of gas flow along the axial direction in the turbomachine component when the turbomachine component is in operation, a plurality of targets (7) being arranged in relief on the radially external surface (9) of the blade between the axially upstream flap and the axially downstream flap of the blade, at least two of the targets (7) not being arranged in parallel directions,the turbomachine component further comprising a capacitive sensor (8) disposed on a radially internal surface of the external housing (4), the capacitive sensor (8) being arranged so as to allow the measurement of a distance between the capacitive sensor (8) and each target (7) at least during a passage of the target (7) past the capacitive sensor (8) in the radial direction.

2. Turbomachine component according to claim 1, wherein a projection of the targets (7) onto the radially external surface (9) extends substantially straight.

3. Turbomachine component according to any one of claims 1 and 2, wherein the targets (7) are projecting parts from the radially external surface (9) in the direction of the radially internal surface of the external stator housing (4).

4. Turbomachine component according to any one of claims 1 to 3, wherein at least one of the targets (7) extends substantially along the axial direction.

5. Turbomachine component according to any one of claims 1 to 4, wherein a maximum thickness (16) of the targets (7) along the radial direction is at least 2.5 millimeters.

6. Turbomachine component according to any one of claims 1 to 5, wherein at least one of the targets (7) has a first surface (13) in direct contact with the radially external surface (9) of the blade, the first surface (13) extending substantially in the radial direction.

7. Turbomachine component according to any one of claims 1 to 6, the turbomachine component being selected from a compressor stage or a turbine stage.

8. Turbomachine component according to any one of claims 1 to 7, wherein the capacitive sensor (8) comprises a cylindrical electrode.

9. Turbomachine (18) comprising a turbomachine component according to any one of claims 1 to 8.

10. Aircraft (17) comprising a turbomachine (18) according to claim 9.

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