FR3085991A1 - AIRCRAFT TURBOMACHINE ELEMENT AND METHOD FOR CONTROLLING THE SAME - Google Patents

Abstract

Turbomachine element, in particular of an aircraft, comprising a metal part, such as a distributor (31), this part comprising a surface (54), called the first surface and configured to be supported on a surface (56) of a sheet (52), called the second surface, a brazing layer being disposed between said first and second surfaces for fixing the sheet to the part, characterized in that the sheet has at least one through slot (58) s extending from an edge (52aa) of said sheet and opening onto said second surface, this slot having a thickness (E) between 0.3mm and 5mm, and a width (D) which is between 0.05 and 2mm.

Description

AIRCRAFT TURBOMACHINE ELEMENT AND ITS CONTROL METHOD

TECHNICAL FIELD The present invention relates to the general field of turbomachinery and in particular to a turbomachine element which comprises a metal part on which a sheet metal is fixed by brazing. The invention applies for example but not exclusively to a turbine distributor on which a sheet is brazed.

STATE OF THE ART [0002] The state of the art notably includes the document FR-A1-2 928 963.

A turbomachine turbine, in particular an aircraft turbine, comprises several stages, each comprising an impeller and a distributor. Each impeller comprises a disc carrying at its outer periphery substantially radial vanes, the discs of the different wheels being connected coaxially to each other and to the drive shaft of the turbine rotor by suitable means.

Each distributor comprises an internal annular platform and an external annular platform between which extend substantially radial blades. The external platform of the distributor comprises means for hooking and fixing to an external casing of the turbine. Its internal annular platform carries annular elements of abradable material intended to cooperate with external annular wipers of an element of the rotor, so as to form a seal of the labyrinth type. This seal makes it possible to control the air flow passing axially through the annular space situated between the internal periphery of the distributor and the rotor of the turbine.

In the current technique, the elements of abradable material are carried by an annular ring which is connected to the internal platform of the distributor by a radial wall. The crown, the radial wall and the internal platform of the distributor are formed from a single piece of casting.

Distributor platforms define between them the annular gas flow stream in the turbine. It is preferable to limit gas leaks outside the stream to optimize the performance of the turbine and therefore of the turbomachine. The flow of gas which escapes from the vein passing radially inside, upstream and downstream of each distributor must therefore be limited. These gas flows pass upstream of the distributor, between the disc of an upstream wheel, on the one hand, and the platform of the distributor, on the other hand, and downstream of the distributor between the internal platform of the distributor, of a hand, and the disc of the downstream wheel, on the other hand.

These leakage gas flows radially towards the inside of the vein are limited by baffle effect, by means of projecting spoilers provided on the wheel discs and the internal platforms of the distributors. The disc spoilers are generally formed in one piece with these discs, while they are formed by added plates and fixed by brazing on the internal platforms of the distributors.

The brazing of a sheet on a dispenser currently includes pointing the sheet on the internal platform, the radial wall or the crown, to hold it in position. The brazing paste is put in place then the assembly is heated in an oven for melting the paste which, in the liquid state, will diffuse between the surfaces to be connected of the distributor and of the sheet. A step of checking the conformity of the assembly is then necessary to check the quality of the soldering.

The control of the good diffusion of the solder is an essential step which makes it possible to ensure the good behavior of the brazed sheet on the part. Ideally, this check should be done visually by an operator to be quick. When such a control is implemented, it is not always reliable and does not guarantee that the operator does not make a control error, by fatigue or repetitive visual checks.

The present invention provides a simple, effective and economical solution to this problem.

PRESENTATION OF THE INVENTION The present invention provides a turbomachine element, in particular an aircraft, comprising a metal part such as a distributor, this part comprising a surface, called the first surface and configured to be in bearing on a surface of a sheet, called the second surface, a brazing layer being disposed between said first and second surfaces for fixing the sheet to the part, characterized in that the sheet has at least one through slot s 'extending from an edge of said sheet and opening onto said second surface, this slot having a thickness of between 0.3mm and 5mm, and a width which is of between 0.05mm and 2mm.

We thus understand that the invention applies to any sheet metal fixed by brazing to a metal part to form a turbomachine element. The sheet and the part have surfaces applied one on top of the other and fixed to each other by a brazing layer. According to the invention, the sheet includes at least one slot which will allow an operator to check the conformity of the brazing during a visual inspection step. The slot is sized to accommodate a gauge block. As will be explained in the following, the gauge block is dimensioned to have a shape complementary to the slot. The slot is further dimensioned so that it can be filled at least in part with the brazing paste after diffusion of the latter. This filling is preferably carried out by capillarity. For this, the dimensions of the slit, and in particular its width, are determined so that the solder paste, with its viscosity and its known surface tension in the liquid state, fills the width of the slit by capillarity. Similarly, the length and thickness of the slit can be determined so that the solder paste fills in at least part of the length and / or thickness of the slit. Control by an operator therefore consists in taking the gauge block and trying to insert it into the slot. If the gauge block does not fit into the slot, it is because the solder paste has spread well and has filled the slot, which therefore cannot receive the wedge. The soldering is then in conformity since the solder paste has spread in the liquid state up to the slot and therefore up to the edge of the sheet. If, on the contrary, the gauge block enters the slot, it is because the solder paste has not correctly or sufficiently diffused and does not sufficiently fill the slot. The brazing is then non-compliant.

The method according to the invention may include one or more of the characteristics and / or steps below, taken in isolation from one another or in combination with each other:

the width of the slot is between 0.1 and 1 mm, and preferably between 0.1 and 0.6 mm,

the slot comprises a straight elongated portion which has a length of between 0.5 and 50mm, and preferably between 0.5 and 20mm, and more preferably between 1 and 10mm,

the slit comprises a second portion extending between said first portion and said edge, this second portion having a generally triangular or trapezoidal shape so that the slit widens on the side of said edge,

- Said second portion includes a large base on the side of said edge, which has a width between 1 and 50mm, preferably between 1 and 20mm, and more preferably between 2 and 10mm, as well as a small base on the side of said first portion and located at a distance from said edge which is between 0.5 and 20mm, preferably between 1 and 10mm and more preferably between 1 and 5mm,

- the sheet includes several slots; these slots can be identical or different and can also extend from the same edge or several edges of this sheet; different slots could for example be shaped and located in zones as a function of conformity criteria for the mechanical strength of the brazing in these zones,

the sheet has a generally annular or circumferential shape around an axis A and has in axial section a general shape in V or L, this sheet comprising first and second annular branches, respectively internal and external, said external branch forming a spoiler aerodynamics and said internal branch forming a fixing branch comprising said second surface as well as said at least one slot which extends from an internal peripheral edge of this branch,

- This part is a turbine distributor, possibly sectorized, and includes two annular platforms, respectively internal and external, the internal platform carrying annular elements in abradable material as well as the sheet.

The method can be preceded by a step of fixing by brazing the sheet on the metal part, in which a brazing paste is deposited between the sheet and the part, at or near said first and second surfaces, along a line substantially parallel to and at a distance from said edge.

The invention also provides a method for checking an element as described above, in order to verify that the sheet is correctly fixed by brazing on the part, this process comprising:

a) a step of attempting to insert a gauge block into said at least one slot, this gauge block having one end configured to be inserted into the slot and having a thickness corresponding to 0.1 to 0.95 times the width from the slot, and

b) a step of classifying the part according to the conformity of the brazing of the sheet, the brazing being compliant if the gauge block fails to be inserted, or not completely, in the slot due to the at least partial filling of this slot by the solder, and being non-compliant if the gauge block manages to be inserted into the slot.

Step a) may consist in trying to insert one end of the gauge block in the first aforementioned portion of the slot.

BRIEF DESCRIPTION OF THE FIGURES 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 drawings annexed in which:

FIG. 1 is a half schematic view in axial section of an aircraft turbomachine turbine, FIG. 1 also showing a detail on a larger scale, FIG. 2 is a very schematic view of an element according to the invention, showing a sheet metal fixed by brazing to a metal part, FIGS. 3a to 3f are views similar to that of FIG. 2 and showing steps for fixing and checking the element, and FIG. 4 is a flow diagram showing steps of a control method according to the invention.

DETAILED DESCRIPTION OF AN EMBODIMENT First of all, reference is made to FIG. 1 which is a diagrammatic half-view in section of a low-pressure turbine 10 of a turbomachine, in a plane passing through the axis of rotation of the turbine rotor.

The turbine rotor comprises four discs 12, 14, 16, 18 assembled coaxially to each other by annular flanges 20 and carrying annular rows of movable blades 22 which are mounted by the feet of blades, by example in dovetail or the like, at their radially inner ends on the outer periphery of the discs 12, 14, 16, 18.

The rotor is connected to a turbine shaft by means of a drive cone 24 fixed by means of an annular flange 26 between the annular flanges 20 of the discs 14 and 16.

Annular flanges 28 for axially retaining the moving blades on the discs are further mounted between the discs 12, 14, 16, 18 and each comprise a radial wall 30 axially clamped between the annular flanges 20 of two adjacent discs.

Between the rows of movable blades 22 are distributors 31 which each comprise two annular platforms 32, 34, respectively internal and external (the terms internal and external being expressed radially with respect to the axis of rotation of the turbine rotor), interconnected by an annular row of fixed blades 36.

The external platforms 34 of the distributors 31 are hung by appropriate means on a casing 38 of the low-pressure turbine. The internal platforms 32 of the distributors 31 each comprise a radial wall 40 which extends radially inwards from an internal surface of the platform and which is connected at its internal periphery to a cylindrical ring 42 for supporting annular elements 44 in abradable material.

These abradable elements 44 are arranged radially outside and facing external annular wipers 46 carried by the flanges 28. The wipers 46 are intended to cooperate by friction with the elements 44 so as to form labyrinth seals and to limit the passage of air in the axial direction through these seals.

The cylindrical ring 42 comprises upstream and downstream of the annular spoilers 48 which extend substantially axially on the side opposite to the radial wall 40 of the internal platform 32 of the dispenser. Upstream and downstream annular spoilers 50 are formed in axial projection on the feet of the movable vanes 22 and cooperate by baffle effect with these annular spoilers 48 and with the upstream and downstream edges of the internal platforms 32 to limit the passage of hot gases from the turbine stream radially inward at the labyrinth seals. The crown 42 and the radial wall 40 of each distributor are formed in a single piece of casting with the internal platform 32 of this distributor, and the spoilers 48 are formed by plates added and fixed on the crown 42, the wall 40 and / or platform 32.

Each sheet 52 (one of which is visible on a larger scale in Figure 1) has a generally annular shape around the axis of the distributor 31 and is optionally sectorized when the distributor 31 is itself sectorized. Each sheet 52 has in axial section a general shape in V or L. Each sheet 52 has first and second annular branches, respectively radially internal 52a and external 52b. The external branch 52b forms the aerodynamic spoiler 48 and the internal branch 52a makes it possible to fix the sheet 52 to the distributor.

The dispenser 31 comprises a first surface 54 in general planar bearing of a second surface 56 in general plane of the sheet 52. In the case mentioned above, these surfaces extend in a plane substantially perpendicular to the distributor axis 31.

Figure 2 shows on a larger scale a part of a sheet 52 and the first surface 54 of the dispenser 31 on which it is fixed. FIG. 2 more precisely shows the first radially internal annular branch 52a of the sheet 52 which extends perpendicular to the axis of the distributor 31 in the context mentioned above. The sheet 52 includes a radially internal peripheral edge 52aa.

As seen in Figure 2, the sheet 52 includes one or more slots 58 which are shaped and dimensioned to each receive a gauge block 60 during a process of visual control of the quality of the solder (Figures 3a - 3f).

In the example shown, the slot 58 is through and thus has a thickness equal to the thickness E of the sheet 52. The slot 58 extends from the free edge 52aa and comprises two portions in the example shown , a first portion 58a elongated rectilinear and a second flared portion 58b which connects the first portion to the edge 52aa.

The first portion 58a has a length L of between 0.5 and 50mm, preferably between 0.5 and 20mm, and more preferably between 1 and 10mm.

The slot 58 has a thickness E between 0.3mm and 5mm (Figure 1), and a width D which is between 0.05 and 2mm at the portion 58a, preferably between 0.1 and 1mm , and more preferably between 0.1 and 0.6mm.

The second portion 58b has a general triangular or trapezoidal shape so that the slot 58 widens on the edge side 52aa.

This second portion 58b includes a large base on the edge side 52aa, which has a width R of between 1 and 50mm, preferably between 1 and 20mm, and more preferably between 2 and 10mm, as well as a small base of the side of the first portion 58a, and located at a distance H from the edge 52aa which is between 0.5 and 20mm, preferably between 1 and 10mm and more preferably between 1 and 5mm.

The sheet 52 preferably comprises several slots 58 of this identical type extending from the same edge 52aa of this sheet.

0n now refers to Figures 3a to 3f which illustrate steps of a control method according to the invention, these steps being schematically represented by the flow diagram of Figure 4.

Step X2 illustrated in FIG. 3a consists in depositing a solder paste 62 between the part and the sheet to be fixed, and therefore between the distributor 31 and the sheet 52 in the above example.

Due to the elongated shape of the sheet 52, the paste 62 can be deposited along a line (circumferential) substantially parallel to the edge 52aa. It is here deposited at one end of the support area of the surfaces 54, 56, located opposite the edge 52aa, as is schematically shown in the detail in FIG. 1.

This step X2 can be preceded by a step X1 of pointing the sheet 52 on the distributor 31 to keep it in position. Welding points are then formed between the sheet and the distributor.

The distributor 31 and the sheet 52 are then heated in an oven during a step X3 shown in Figures 3b and 3c. Heating the solder paste 62 above its melting temperature causes the paste to transform into a liquid state which can then diffuse between the surfaces 54, 56 and up to the edge 52aa.

0n therefore notes that the solder paste 62 liquid covers the bottom of the portion 58a of the slot 58, on the surface 54 and at least partially fills it by capillary action. The other portion 58b of the slot, due to its shape and dimensions, does not fill (completely) by capillary action.

After cooling and solidification of the dough, the brazing control can be performed during a step X4 shown in Figures 3d to 3f.

The gauge block 60 is then used in step X4 and comprises an end 60a which is shaped and dimensioned to be engaged in the slot 58 and more particularly in its first portion 58a. This means that, when the sheet 52 is not yet fixed on the distributor 31, the end 60a of the shim 60 is capable of being engaged, preferably without play or with minimal play, in the slot 58.

The second flared portion 58b of the slot 58 makes it easier to approach and insert the wedge 60 into the first portion 58a, as shown in FIG. 3d. The operator approaches the wedge 60 of the slot 58 and the wedge can then be guided to the first portion 58a by pressing and sliding the end 60a of the wedge on the inclined edges of the second portion which converge towards the first portion.

At this time, there are two possibilities in step X5.

If the gauge block 60 does not fit into the first portion 58a of the slot 58, it is because the solder paste 62 has spread well and has filled the slot which therefore cannot receive the wedge (FIG. 3rd). The brazing is then declared to be in conformity (abbreviation "C >> in FIG. 4) by the operator since the paste 62 has spread in the liquid state up to the slot and therefore up to the edge of the sheet, and has therefore spread correctly.

If on the contrary the standard block 60 fits into the first portion 58a of the slot, it is that the solder paste 62 has not been correctly or sufficiently diffused and does not fill the slot sufficiently. The brazing is then declared non-compliant (abbreviation "NC") by the operator.

In other variants not shown, the sheet could include several different slots and located in zones according to specific compliance criteria for the mechanical strength of the brazing in these zones.

Claims (10)

1. Turbomachine element, in particular of an aircraft, comprising a metal part, such as a distributor (31), this part comprising a surface (54), called the first surface and configured to be supported on a surface (56) of a sheet (52), called the second surface, a brazing layer being disposed between said first and second surfaces for fixing the sheet to the workpiece, characterized in that the sheet has at least one slot (58) through extending from an edge (52aa) of said sheet and opening onto said second surface, this slot having a thickness (E) between 0.3mm and 5mm, and a width (D) which is between 0.05mm and 2mm. 2. Element according to claim 1, wherein the width (D) of the slot (58) is between 0.1 and 1mm, and preferably between 0.1 and 0.6mm. 3. Element according to claim 1 or 2, wherein the slot (58) comprises a portion (58a) elongated rectilinear which has a length (L) of between 0.5 and 50mm, and preferably between 0.5 and 20mm, and more preferably between 1 and 10mm. 4. Element according to one of the preceding claims, wherein the slot (58) comprises a second portion (58b) extending between said first portion (58a) and said edge (52aa), this second portion having a generally triangular shape or trapezoidal so that the slot widens on the side of said edge. 5. Element according to the preceding claim, wherein said second portion (58b) comprises a large base on the side of said edge (52aa), which has a width (R) of between 1 and 50mm, preferably between 1 and 20mm, and more preferably between 2 and 10mm, as well as a small base on the side of said first portion and located at a distance (H) from said edge which is between 0.5 and 20mm, preferably between 1 and 10mm and more preferably between 1 and 5mm. 6. Element according to one of the preceding claims, in which the sheet (52) comprises several identical slots (58) extending from the same edge (52aa) or several edges of this sheet. 7. Element according to the preceding claim, in which the sheet (52) has a generally annular or circumferential shape around an axis A and has in axial section a general shape in V or L, this sheet comprising first and second annular branches (52a, 52b), respectively internal and external, said external branch forming an aerodynamic spoiler (48) and said internal branch forming a fixing branch comprising said second surface (56) as well as said at least one slot (58) which s extends from an internal peripheral edge of this branch. 8. Element according to one of the preceding claims, in which this part is a turbine distributor (31), optionally sectorized, and comprises two annular platforms (32, 34), respectively internal and external, the internal platform carrying annular elements (44) of abradable material as well as the sheet (52). 9. Method for controlling an element according to one of the preceding claims, in order to verify that the sheet (52) is correctly fixed by brazing on the part, this method comprising: a) a step (X4) of attempting to insert a gauge block (60) into said at least one slot (58), this gauge block comprising an end (60a) configured to be inserted into the slot and having a thickness corresponding to 0.1 to 0.95 times the width of the slit, and b) a step (X5) of classifying the part according to the conformity of the brazing of the sheet (52), the brazing being in conformity (C) if the gauge block fails to be inserted, or not completely, in the slot of the makes at least partial filling of this slot with the solder, and being non-compliant (NC) if the gauge block manages to be inserted in the slot. 10. The method of claim 9, wherein the slot (58) is as defined in claim 4 or 5, wherein step a) consists of trying to insert one end of the gauge block (60) in the first portion of the slot (58).