FR3074286A1 - DEVICE FOR DETECTING A DEFECT ON A SURFACE OF A MATERIAL ABRADABLE FROM A TURBOMACHINE CARTER - Google Patents

Abstract

Device for detecting a defect on a surface (18b) of an abradable material (18) of a turbomachine casing (10), the device (4) being intended to be positioned on a turbomachine casing (10), longitudinal axis (A), provided with an abradable material (18) having a longitudinal annular main surface (18b) delimited at each of its longitudinal ends by a radial flank (18a), characterized in that the device (4) comprises a comparator (9) for detecting a variation of the thickness of the abradable material (18) during a displacement of the device (4), the detection device (4) being configured to move in a same circumferential direction (B), on one of the radial flanks (18a) and on the main surface (18b) of the abradable material (18).

Description

TECHNICAL AREA

The present invention relates to a device for detecting a fault on the surface of an abradable material of a turbomachine casing, in particular of an abradable material of a fan casing of a turbomachine. It also relates to a method implementing the device.

STATE OF THE ART

A turbomachine comprises at its upstream end (with reference to the flow of gases in the turbomachine) a fan comprising an impeller which is surrounded by a fan casing, called a retention casing because of its function of retaining the blades in case of rupture of these. The fan housing also forms the aerodynamic vein of the engine to channel the air flow.

To obtain maximum efficiency, the clearance between the blades and the housing must be minimum. This technical constraint is resolved by placing an abradable material on the casing, facing the blade. When the blades start to move, during the first rotations of the motor, the blades lengthen and the residual play is filled. The vanes can rub on the abradable material and remove part of it, which allows zero play in operation.

However, the dawn can only remove a reduced quantity of abradable material (of the order of a few tenths of a mm, and the machining of the abradable material must therefore be very precise. The definition plane indicates a shape tolerance on the entire surface of the fan housing. This characteristic is measured with a three-dimensional measuring machine (CMM) in manufacturing plants.

This tolerance must be obtained on a new part, but also after retouching and repairing the part.

The measurement, carried out using the three-dimensional measuring machine, is however not suitable in the case of retouching of the part. For example, it can happen that the machining of the abradable material reveals air bubbles included in it. In this case where one or more air bubbles remain, a touch-up is carried out by resealing each bubble with the addition of abradable material. The excess material is sanded down so that the shape tolerance is respected again. In this case, there is no simple way to check that the retouching does not have any hollow or bump.

The invention seeks to remedy this drawback by proposing a device for detecting a fault on a surface of an abradable material of a turbomachine casing, the device being both simple to use and reliable. It also proposes a method implementing the device.

STATEMENT OF THE INVENTION

The subject of the invention is therefore a device for detecting a fault on a surface of an abradable material of a turbomachine casing, the device being intended to be positioned on a turbomachine casing, of longitudinal axis, provided with 'an abradable material having a longitudinal annular main surface delimited at each of its longitudinal ends by a radial flank.

The device according to the invention comprises a comparator making it possible to detect a variation in the thickness of the abradable material during movement of the device, the detection device being configured to move, in the same circumferential direction, on one of the radial sides and on the main surface of the abradable material.

Thus, thanks to the specific positioning of the detection tool on the abradable material, the detection tool can move laterally over the entire perimeter of the abradable material, and it is possible to precisely and easily position the comparator on the main surface of the abradable material, and thus detect any hollow or bump on the surface.

The invention is very useful for repairing the abradable surface during maintenance operations, following for example holes in the abradable material which are linked to impacts in flight. The invention makes it possible to dispense with complex measuring devices and therefore to carry out maintenance in more workshops, or even directly under the wing of the aircraft.

The comparator is advantageously configured to move longitudinally along the detection tool, which makes it possible to adjust the longitudinal position of the comparator and thus measure any anomaly on the surface of the abradable material.

The device can be configured to extend longitudinally between each longitudinal end of the abradable material, and it can comprise a first series of wheels arranged longitudinally and intended each to be supported on the radial flank of a first longitudinal end of the abradable material, as well as a second series of wheels arranged radially and intended each to be supported on the main surface of the abradable material, the first series of wheels and the second series of wheels being intended to be positioned at the level of the first longitudinal end of the material abradable.

The device may comprise at least one wheel arranged radially and bearing on the main surface of the abradable material, said wheel being intended to be positioned at a second longitudinal end of the abradable material.

The comparator may be a mechanical comparator comprising a needle capable of moving radially under the effect of a variation in the thickness of the abradable material.

A support of abradable material is typically disposed between the casing and the abradable material.

The casing is advantageously a fan casing.

The invention also relates to an assembly comprising the housing and the detection device.

The invention also relates to a method for detecting a fault on a surface of an abradable material of a turbomachine casing.

The method according to the invention implements a device described above.

The process can include the following steps:

- positioning of the detection tool on the abradable material,

- displacement of the detection tool over a predetermined area of the abradable material, and

- detection of a fault when the comparator has detected a variation in the thickness of the abradable material.

The housing can be positioned on a plane orthogonal to the longitudinal axis of the housing, so that the first series of wheels bears on the upper radial flank of the abradable material.

DESCRIPTION OF THE FIGURES

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

- Figure 1 is a schematic perspective view of an annular fan casing of a turbomachine, this casing comprising a layer of abradable material;

- Figure 2 is a schematic half-view in axial section of the housing of Figure 1;

- Figure 3 is a partial perspective view of a device according to the invention;

- Figure 4 is a schematic sectional view of the device of Figure 3; and

- Figure 5 is a partial schematic view of Figure 3 illustrating different stages of a detection method according to the invention.

DETAILED DESCRIPTION

Reference is first made to FIGS. 1 and 2 which show an annular casing 10 of an aircraft turbomachine. Conventionally, a turbomachine comprises from upstream to downstream, in the direction of flow of the gases, a blower, at least one compressor, an annular combustion chamber, at least one turbine, and a nozzle for ejecting the gases of combustion. The air flow passing through the blower is divided into a first air flow, called the primary flow or hot flow, which enters the compressor, to be compressed there, then burned in the chamber, before flowing into the turbine and to be ejected into the nozzle, and a second flow, called secondary flow or cold flow, which flows between the engine (comprising the compressor, the combustion chamber and the turbine) and a nacelle of the turbomachine. The blower comprises a wheel which rotates inside an annular casing such as that of FIG. 1, which is commonly called retention casing for the reasons mentioned above.

The annular casing 10 has a generally substantially cylindrical shape with an axis of revolution A. It comprises an annular fixing flange 12 at each of its axial ends. These flanges 12 are used to fix the casing 10 to annular walls of the nacelle of the turbomachine. The casing 10 can also comprise annular stiffeners 14.

The casing 10 comprises a radially internal annular surface 16 covered with a layer of abradable material 18. This layer 18 is continuous over 360 ° and has an axial length or dimension, along the axis A, which represents from 20 to 40 % of the length of the housing in the example shown. This layer 18 is here located near the upstream end of the casing 10 and is intended to extend opposite the top of the blades of the fan wheel. Layer 18 is obtained by polymerization of a resin which is prepared from at least two components A and B.

The terms "internal" and "external", "longitudinal" and "radial" are defined with respect to the axis A of the housing 10.

FIG. 3, in which the elements identical to those of FIGS. 1 and 2 bear the same references, illustrates the radially internal face 16 of the casing 10. A support 2 of abradable material is placed under the layer 18 of abradable material. The support 2 is typically a honeycomb structure, covered with a composite material. A fixing material 3, such as glue, is placed outside the support 2 and makes it possible to fix the support 2 on the casing 10.

A device for detecting faults on the surface of the abradable material according to the invention, in the form of a tool 4, will now be described, in conjunction with FIGS. 3 to 5.

The tool 4 comprises at each of its longitudinal ends displacement elements, typically wheels or casters, allowing the device to move laterally over the entire perimeter of the abradable material 18. The tool 4 thus comprises at a first longitudinal end two series of wheels, namely a first series of two wheels 5 arranged longitudinally and each intended to rest on a radial portion of the abradable material, at a first longitudinal end of the abradable material 18, and a second series of two wheels 6 arranged radially and intended each to rest on a longitudinal portion of the abradable material, at the level of the first longitudinal end of the abradable material 18. In particular, the wheels 5 are supported, at the level of the first longitudinal end, on a radial flank 18a of the abradable material 18, while the wheels 6 are supported, at the level of the first longitudinal end, on the main longitudinal surface 18b of the abradable material 18.

At the second longitudinal end of the tool 4 is disposed a wheel 7 intended to bear on the main surface 18b, at the second longitudinal end of the abradable material 18. The wheels 5, 6, 7 are positioned at longitudinal ends of the abradable material 18, and move over healthy, unrepaired areas of the abradable material 18.

The tool 4 can thus move laterally over the entire perimeter of the abradable material 18, in a lateral (circumferential) direction B which follows the perimeter of the abradable material 18, each wheel 5, 6, 7 moving simultaneously in the lateral direction B .

The tool 4 is thus precisely positioned on two surfaces of the abradable material 18, which are the radial flank 18a on which the wheels 5 rest, and the main surface 18b on which the wheels 6, 7 rest. are chosen directly on the abradable material 18, which makes it possible to be particularly precise, since the tool 4 is positioned directly on the element to be measured.

The tool 4 comprises a support 8, typically made of sheet metal, on which the wheels 5, 6, 7 are fixed. The support 8 comprises a longitudinal main part 8a which extends longitudinally to the tool 4. The longitudinal main part 8a is connected, on the side of the first longitudinal end, to a support part 8b on which is fixed the second series of wheels 6. The support part 8b extends radially and connects the two wheels 6 together, each wheel 6 being fixed to one end of the support part 8b. The support part 8b of the second series of wheels 6 is itself connected to a support part 8c on which the first series of wheels is fixed 5. The support part 8c of the first series of wheels 5 extends longitudinally and connects the two wheels 5 together, each wheel 5 being fixed to one end of the support part 8c. The main longitudinal part 8a of the support 8 is connected, on the side of the second longitudinal end, to a support part 8d on which the wheel 7 is fixed. The support part 8d extends radially.

The main longitudinal part 8a of the support 8 is also laterally connected to a comparator 9, via a comparator support 8e, on one side, and to a gripping element 8f, of the handle type, on the other side. The comparator support 8e and the gripping element 8f extend radially. The comparator 9 can be moved longitudinally in translation along the comparator support 8e, so that it is possible to adjust the position of the comparator 9 relative to the abradable material 18 longitudinally.

The comparator 9 is a device making it possible to detect variations in the thickness of the abradable material 18 (or in an equivalent manner variations with respect to the flatness of the surface 18b of the abradable material 18, or in other words making it possible to detect an irregularity on the surface 18b of the abradable material 18) with respect to a nominal reference position, the deviation possibly being positive or negative. The comparator 9 can be provided with a needle 9a capable of moving radially under the effect of the variation in the thickness of the abradable material 8, in particular in the event of a bump or hollow on the surface of the abradable material 8. One or several return elements, not shown, can maintain the position of the needle 9a in a standard position. The needle 9a is symbolized by an arrow in FIGS. 4 and 5. The comparator illustrated is of the mechanical type, but one could also use any device making it possible to detect deviations in depth, such as for example an optical comparator, or with a laser beam .

FIG. 5 illustrates the surface 18b of the layer of abradable material 18. Due to the presence of an air bubble on the surface, the bubble was capped by adding abradable material. We can thus distinguish on the surface of the abradable material 8 the machined surface 18b and a retouched surface 18c which has an excess of material.

After such retouching of abradable material, the excess material 18c must be removed by sanding. This bead 18c is conventionally measured by hand, by touch, and the relevance of the measurement is thus questionable. The device according to the invention makes it possible to measure the height of the bead 18c by scanning the surface of the layer of abradable material 18 by the comparator 9.

FIG. 5 illustrates three different positions of the comparator 9, the comparator being able to move laterally by means of the wheels, in the directions of the arrows. In a first position, illustrated on the left of the figure, the comparator 9 is located opposite a healthy portion of the surface 18b. Since the thickness of the abradable material 18 is at this point the nominal thickness, the needle 9a indicates that the deviation from the nominal position is zero. By moving the comparator 9 to the right, as illustrated in the middle position of the figure, the comparator 9 finds itself facing the bead 18c. The needle 9a is then deflected towards the center of the comparator 9, and it indicates a deviation of -0.22 mm from the nominal position. With this value of the height of the bead 18c, the operator can sand the abradable material with a stick to avoid leaving too large a bead or even forming a hollow in the event of excessive sanding. By continuing to move the comparator 9 to the right, the comparator 9 is found vis-à-vis a healthy portion of the surface 18b, and the needle 9a again indicates that the deviation from the nominal position is no.

The device according to the invention thus implements a simple tool of reduced size. Setting the device on the abradable material is easily carried out via the casters, and the device can move laterally stably, and this over the entire circumference of the abradable material. The axial position of the comparator is adjustable, which makes it possible to measure any anomaly on the surface of the abradable material.

Claims (9)

1. Device (4) for detecting a fault (18c) on a surface (18b) of an abradable material (18) of a turbomachine casing (10), the device (4) being intended to be positioned on a turbomachine casing (10), of longitudinal axis (A), provided with an abradable material (18) having a longitudinal annular main surface (18b) delimited at each of its longitudinal ends by a radial flank (18a), characterized in that the device (4) comprises a comparator (9) making it possible to detect a variation in the thickness of the abradable material (18) during movement of the device (4), the detection device (4) being configured to moving, in the same circumferential direction (B), on one of the radial sides (18a) and on the main surface (18b) of the abradable material (18). 2. Device (4) according to claim 1, characterized in that the comparator (9) is configured to move longitudinally along the device (4). 3. Device (4) according to claim 1 or 2, characterized in that it is configured to extend longitudinally between each longitudinal end of the abradable material (18), and in that it comprises a first series of wheels ( 5) arranged longitudinally and each intended to be supported on the radial flank (18a) of a first longitudinal end of the abradable material (18), as well as a second series of wheels (6) arranged radially and intended each to be in bearing on the main surface (18b) of the abradable material (18), the first series of wheels (5) and the second series of wheels (6) being intended to be positioned at the level of the first longitudinal end of the abradable material (18) . 4. Device (4) according to claim 3, characterized in that it comprises at least one wheel (7) disposed radially and bearing on the main surface (18b) of the abradable material (18), said wheel (7) being intended to be positioned at a second longitudinal end of the abradable material (18). 5. Device (4) according to one of claims 1 to 4, characterized in that the comparator (9) is a mechanical comparator comprising a needle (9a) able to move radially under the effect of a variation of l thickness of the abradable material (18). 6. Device (4) according to one of claims 1 to 5, characterized in that the casing (10) is a fan casing. 7. Method for detecting a defect on a surface (18b) of an abradable material (18) of a turbomachine casing (10), characterized in that it implements a device (4) according to the one of claims 1 to 6. 8. Method according to claim 7, characterized in that it comprises the following steps: - positioning of the detection device (4) on the abradable material (18), displacement of the detection device (4) over a predetermined area of the abradable material, and - detection of a fault when the comparator (9) has detected a variation in the thickness of the abradable material (18). 9. Method according to claim 7 or 8, in conjunction with claim 3, characterized in that the housing (10) is positioned on a plane orthogonal to the longitudinal axis (A) of the housing (10), so that that the first series of wheels (5) is in abutment on the upper radial flank (18a) of the abradable material (18).