FR3024884B1 - METHOD FOR PRODUCING A SECTORIZED SEAL RING AND A TURBOMACHINE TURBINE - Google Patents

Abstract

Process (A) for producing a sectorized sealing ring for a turbomachine, this ring comprising an annular row of ring sectors arranged circumferentially end to end, each ring sector comprising at least one circumferential hook which is configured to cooperating with an annular rail for fastening a turbomachine casing, said at least one circumferential hook having a radius of curvature different from that of said rail so as to be mounted in radial prestressing on said rail, comprising the steps of a) defining a criterion of maximum interference between the circumferential ends of said at least one hook and said rail, b) determining a maximum circumferential dimension of each ring sector from said maximum interference criterion, and c) realizing the sectors of ring, the ring sectors having said maximum circumferential dimension.

Description

Process for producing a sectorized sealing ring and a turbomachine turbine

TECHNICAL AREA

The present invention relates to a method for producing a sectorized sealing ring and a turbomachine turbine.

STATE OF THE ART

A turbomachine turbine comprises one or more stages each comprising a distributor formed of an annular row of stationary vanes carried by a casing of the turbine, and a rotor wheel rotatably mounted upstream or downstream of the distributor. The wheel is surrounded by a sealing ring which is sectored and formed by sectors which are arranged circumferentially end to end and which are hooked on the casing of the turbine.

Each ring sector generally comprises a circumferentially oriented metal plate which carries a block of abradable material attached to the inner surface of the plate. This block is for example of the honeycomb type and is intended to wear by friction on external annular wipers of the vanes of the wheel, to form a labyrinth seal and minimize the radial clearances between the wheel and the ring areas.

Each ring sector comprises at its upstream and downstream ends hooking means on the housing. Each ring sector may comprise at its upstream end two hooks or circumferential edges which define between them an annular groove in which is engaged an annular rail of the housing. The downstream end of the ring sector can be clamped radially on another annular rail of the casing via means of attachment of the distributor located downstream of the wheel. The fastening systems of the ring sectors on the housing make the ring sectors integral with the housing. The upstream hooks of the ring sectors are "pre-arched" with respect to the crankcase rail, that is to say that they have radii of curvature greater than that of the crankcase rail, which allows them to mount with some radial prestressing on the rail.

Furthermore, an annular cavity extends between the ring and the housing and it is important that a seal be provided between the ring sectors to prevent gas leakage between the sectors, radially from the inside towards the outside, that is to say from the vein of the turbine into the aforementioned cavity. Indeed, the role of the vein gases is to transmit energy to the moving wheels in order to drive the turbine which itself drives the compressor rotor of the engine. The higher the leakage rate, the less energy is transmitted to the moving wheels and the lower the efficiency of the turbine. The sealing between the ring sectors is generally ensured by sealing strips mounted between the ring sectors. However, this technology is not always effective.

It has also been found that the production cost of a ring depends in particular on the number of pieces. Reducing the number of ring sectors could therefore reduce the cost of manufacturing the engine.

The present invention is intended to provide a simple, effective and economical solution to this need.

SUMMARY OF THE INVENTION

The present invention thus proposes a method for producing a sectorized sealing ring for a turbomaehine, this ring comprising an annular row of ring sectors arranged circumferentially end to end, each ring sector comprising at least one circumferential hook which is configured to cooperate with an annular gripping rail of a turbomaehine casing, said at least one circumferential hook having a radius of curvature different from that of said rail so as to be mounted in radial prestressing on said rail, characterized in that it comprises the steps of: a) defining a maximum interference criterion between said at least one hook and said rail, and in particular between the circumferential ends of said at least one hook and said rail, b) determining a maximum circumferential dimension of each ring sector from said maximum interference criterion, and c) forming the ring sectors, the ring sectors having the maximum circumferential dimension determined in step b). The invention thus proposes to provide ring sectors having the largest possible circumferential dimension so as to reduce the number of ring sectors. It proposes to determine the circumferential maximum circumferential dimension of its sectors. The criterion is determined to optimize the circumferential dimension without overtraining the ring, which would not result in a risk of plasticization. Step c) may comprise the substeps of: c1) determining a number of ring sectors from a radius of the ring and the maximum circumferential dimension determined in step b), c2) determining the effective circumferential dimension of the ring sectors so that it is the same for all the ring sectors, and c3) forming the ring sectors.

The maximum interference criterion can be defined in step a) from a radius of the ring.

The present invention also relates to a method for producing a turbomachine turbine, this turbine comprising at least one stage comprising a rotor wheel surrounded by a sectorized sealing ring and a sectorized distributor, each ring sector comprising at least one circumferential hook which is configured to cooperate with an annular latching rail of a turbomachine casing, said at least one circumferential hook having a radius of curvature different from that of said rail so as to be mounted in radial prestress on said rail, each dispenser sector having at least one circumferential flange which is configured to cover or to be covered by a circumferential portion of a ring sector, characterized in that it comprises the steps of the method as described above, and it further comprises the steps of: d) defining a recovery criterion nt minimum circumferential between the ring sectors and the distributor sectors of said at least one stage, e) angularly position the ring sectors vis-à-vis the distributor sectors so as to meet the recovery criterion defined in the step d), and f) realize the turbine.

In the case where no angular position makes it possible to comply with the recovery criterion in step e), the method may comprise a substep of increasing the number of ring sectors.

The number of ring sectors may be the same as the number of distributor sectors. In a variant, the number of ring sectors is smaller than the number of distributor sectors. Step f) may comprise a sub-step of reporting and securing anti-rotation means on the ring sectors, and machining notches or holes in a housing rail, said notches or orifices being configured to receive said anti-rotation means.

The anti-rotation means of the ring sectors may be identical and positioned in the same way on all the ring sectors so that they are identical and therefore interchangeable.

The present invention also relates to a sectorized sealing ring or turbomaehine turbine obtained by one of the methods as described above.

DESCRIPTION OF THE FIGURES The invention will be better understood and other details, characteristics and advantages of the invention will become apparent on reading the following description given by way of nonlimiting example and with reference to the appended drawings, in which: Figure 1 is a partial schematic view in axial section of a turbomaehine turbine; - Figure 2 is a schematic sectional view along the line II-II of Figure 1; FIG. 3 is a partial schematic view from above of a turbomaehine turbine; FIG. 4 is a flowchart showing process steps according to the invention; FIGS. 5a and 5b are very schematic representations showing the respective angular positions of ring sectors and distributor sectors of a turbine; and FIG. 6 is a schematic view in perspective and in axial section of a turbine according to the invention.

DETAILED DESCRIPTION

Referring first to Figure 1 which shows a turbine 10, here low-pressure, a turbomaehine such as a turbojet or an airplane turboprop, this turbine having several stages each having a distributor 121; 122 formed of an annular row of vanes carried by a casing 14 of the turbine, and a bladed wheel 16 mounted upstream of the distributor 12Ί, 122 and rotating in a ring 18 attached to the housing 14. The ring 18 is sectorized and formed of several sectors which are worn circumferentially end to end by the casing 14 of the turbine.

Each ring sector 18 comprises a frustoconical wall 20 and a block 22 of abradable material fixed by soldering and / or welding on the radially inner surface of the wall 20, this block 22 being of the honeycomb type and intended for wear by friction on external annular wipers 24 of the vanes of the wheel 16 to minimize the radial clearances between the wheel and the ring sectors 18.

Each ring sector 18 comprises at its upstream end a circumferential member 32 with a C-section whose opening opens upstream and which is engaged axially downstream on a cylindrical rail 34 facing downstream of the distributor 12i. located upstream of the ring sectors 18, on the one hand, and on a cylindrical rail 36 of the casing 14 on which is hooked this distributor, on the other hand. The member 32 of each ring sector 18 comprises two circumferential rims or hooks 38 and 40 extending upstream, radially external and radially inner respectively, which are connected together at their upstream ends by a radial wall 42, and which are respectively applied to a radially outer and inner cylindrical face of the rail 36, the hook 40 holding the cylindrical flange 34 of the dispenser against the rail 36.

The downstream ends of the ring sectors 18 are clamped radially on a cylindrical rail 30 of the housing by the distributor 122 located downstream of the ring sectors.

The ring sectors 18 are radially outwardly bearing on a radially inner cylindrical face of the rail 30 of the housing, and inwardly on a radially outer cylindrical face of a cylindrical rim 28 of the distributor 122.

As can be seen in FIG. 2, the hooks 38, 40 of the ring sectors 18 are "pre-arched" with respect to the casing rail 36, that is to say that they have higher radii of curvature to that of the housing rail 36, which allows to mount them with some radial prestressing on the rail. Due to this pre-bending, the ring sector 18 shown in FIG. 2 has support zones C1, C2, C3 which are not very extensive on the rail 36. The median part of the internal face of the hook 38 of the sector 18 is in support C1 on the outer face of the rail 36 and the end portions of the outer face of the hook 40 are supported C1 and C3 on the inner face of the rail 36.

In order not to over-constrain the ends of the ring 18 (risk of plasticization), a maximum interference criterion at the circumferential ends of its sectors is defined. This interference is defined as the arrow at the ends in support of the ring mounted. This criterion can in particular be derived from experience. For the same ring radius, the interference is dependent on the circumferential dimension D of the ring sectors 18.

Still with the aim of limiting intersecting ring gas leaks, ring sectors 18 and distributor areas 121; 122 are offset circumferentially relative to each other, as can be seen in FIG.

FIG. 3 represents a turbine with at least four stages, each stage comprising a wheel (not visible) surrounded by a segmented ring of which only a sector 18Ί, 182, 183, 184 is represented here, and a distributor situated upstream of the ring and of which only a sector 12-i, 122,123, 124 is also shown. The index i (i ranging from 1 to 4) indicates the number of the stage. Thus, sectors 12Ί, 181 belong to the first floor, sectors 122,182 belong to the second floor, and so on.

L is the circumferential distance between the circumferential end of a ring sector and the circumferential end closest to an adjacent distributor sector of the same stage. In other words, Li corresponds to the minimum circumferential distance between the ring intersectors and the intersectors of the adjacent distributor of the same floor.

According to the invention, a minimum overlap criterion β is defined between the ring sectors and the distributor sectors. The covering corresponds to the circumferential distance L, mentioned above. In the same way, this criterion can in particular be derived from experience.

FIG. 4 represents steps of an exemplary embodiment of methods according to the invention, namely a first method A for producing a sectorized sealing ring for a turbomachine, and a second method B for producing a turbine turbomachine.

The first method A according to the invention comprises the steps of: a) defining the criterion a of maximum interference, for example from the radius of the ring 18, b) determining the maximum circumferential dimension D of each sector of ring 18 from said criterion a, and c) realize the ring sectors 18 which have the maximum circumferential dimension D determined in step b).

The minimum number of ring sectors 18 is achieved by selecting the largest circumferential dimension D of sectors that meets the desired criterion of maximum interference a. Step c) may comprise sub-steps consisting of: c1) determining a number of ring sectors 18 from the radius of the ring and dimension D, c2) determining the effective circumferential dimension D 'of sectors ring so that it is the same for all the ring sectors, and c3) realize the ring sectors.

The second method B according to the invention comprises, in addition to the above steps, the steps of: d) defining the minimum circumferential overlap criterion β between the ring sectors 18 and the distributor sectors 12 of a stage, e ) angularly position the ring sectors 18 vis-à-vis the distributor sectors 12 so as to meet the criterion β, and f) realize the turbine.

In the case where no angular position makes it possible to comply with the recovery criterion in step e), it comprises a sub-step consisting of g) increasing the number of ring sectors. This sub-step g) can be followed by a new step b) in which the dimension D is optimized according to the modified number of ring sectors.

With the number of ring sectors minimized, it is therefore necessary to angularly position the ring sectors so that each sector has an overlap meeting the criterion β fixed. FIG. 5a shows an example of bad angular positioning because it can be seen that the distance L can be very small (in zone I) and is lower than criterion β. FIG. 5b shows an example of good angular positioning because it can be seen that the distance L 'is larger and is greater than the criterion β. The object of the invention is therefore to reduce as much as possible the number of ring sectors. Although it is possible that this number remains equal to the number of distributor sectors of the same floor, as in the prior art, it is also possible that the number of ring sectors here is less than the number of distributor sectors.

When the number of ring sectors is identical to the number of distributor sectors, each ring sector is positioned in the same way with respect to adjacent distributor areas (identical overlaps between the ring and distributor intersectors). In this way, it is possible to create the anti-rotation of the ring sectors by the distributor sectors.

For example, there is known a first anti-rotation technology consisting in blocking the circumferential displacements of the ring sectors by creating a notch upstream of each ring sector. An end of the distributor sector positioned upstream of the ring is housed in this notch so as to prevent the ring sector from rotating tangentially. To increase the support surface of the tangential lock, an anti-rotation pin may be brazed to the ring sector next to its notch.

A second anti-rotation technology is to position a tab downstream of each ring sector. This tongue is housed in a notch in the distributor sector located downstream of the ring, preventing the ring sector from rotating tangentially.

Whether upstream or downstream, the anti-rotation technology is positioned at the same place on all ring sectors and on all distributor sectors because these sectors are identical in number.

By minimizing the number of ring sectors, one seeks to be independent of the number of distributor sectors. The number of minimum ring sectors to install is therefore likely to be different (lower) than the number of adjacent distributor areas.

Under these conditions, it is difficult to ensure the anti-rotation of the rings by the distributors because the positioning of anti-rotation technology (upstream or downstream) should be specific to each sector of ring and to each distributor area. This would imply: - a clean room reference to each ring sector and each distributor sector, and therefore a multiplication of the number of references - a different manufacturing for each ring sector and for each distributor sector of a same floor, and - a non-interchangeability of ring sectors between them and distributor sectors between them, which would result in a complexification of assembly operations and change of parts on fleet engines.

According to the invention, these problems are solved by virtue of the fact that, in the aforementioned step f), the method comprises a substep of reporting and fixing anti-rotation means on the ring sectors, and machining notches or holes in the housing rail, these notches or orifices being configured to receive said anti-rotation means. The anti-rotation means of the ring sectors can thus be identical and positioned in the same way on all ring sectors so that they are identical and therefore interchangeable.

In the example shown in Figure 6, the anti-rotation means of each ring sector 18 comprises a pin 50 which is positioned and fixed, for example by brazing, at the downstream end of the sector. It is here located on the radially outer face of the sector 18 intended to be applied against the rail 30 of the housing 14. The rail 30 comprises a radial notch 52 for receiving the pin 50 of each ring sector 18. The pin 50 is intended to circumferentially engage with the side walls of the notch 52 to tangentially block the ring sector vis-à-vis the housing 14, independently of the distributors.

In addition to the aforementioned advantages of this solution, the realization of notches 52 in the housing rail 30 reduces the stress in this rail in operation. In fact, the rail is no longer continuous over 360 ° and the tangential stresses due to the temperatures cancel out at the circumferential ends of the rail.

Claims (7)

1. Method (A) for producing a sectorized sealing ring (18) for a turbomaehine, this ring comprising an annular row of circumferentially end-to-end ring sectors, each ring sector comprising at least one hook circumferential member (40) which is configured to cooperate with an annular gripping rail (36) of a turbomachine casing (14), said at least one circumferential hook having a radius of curvature different from that of said rail so as to be mounted in radial prestressing on said rail, characterized in that it comprises the steps of: a) defining a criterion (a) of maximum radial interference between said at least one hook and said rail, and in particular between the circumferential ends of said at least one hook and said rail, b) determining a maximum circumferential dimension (D) of each ring sector from said maximum interference criterion and c) providing ring sectors, ring sectors having the maximum circumferential dimension determined in step b). 2. Method (A) according to claim 1, characterized in that step c) comprises the sub-steps of: d) determining a number of ring sectors (18) from a radius of the ring and the maximum circumferential dimension (D) determined in step b), c2) determining the effective circumferential dimension of the ring sectors so that it is the same for all ring sectors, and c3 ) realize your ring areas. 3. Method (A) according to claim 1 or 2, characterized in that the criterion (a) of maximum interference is defined in step a) from a radius of the ring. 4. Method (B) for producing a turbine (10) turbomaehine, the turbine comprising at least one stage having a rotor rooe (16) surrounded by a ring (18) sectorized sealing and a distributor (12 ^ ) sectorized, each ring sector comprising at least one circumferential hook (40) which is configured to cooperate with an annular gripping rail (36) of a turbomaehine casing (14), said at least one circumferential hook having a a radius of curvature different from that of said rail so as to be radially prestressed on said rail, wherein each manifold sector has at least one circumferential flange (28) which is configured to overlap or be covered by a circumferential portion of a sector ring, characterized in that it comprises the steps of the method according to one of the preceding claims, and in that it further comprises the steps of: d) defining a scream circumferential overlap (β) between the ring sectors and the distributor sectors of said at least one stage, e) angularly positioning the ring sectors with respect to the distributor sectors so as to meet the criterion of recovery defined in step d), and f) realize the turbine. 5. Process (B) according to claim 4, characterized in that, in the case where no angular position makes it possible to comply with the recovery criterion (β) in step e), it comprises a sub-step consisting of increasing number of ring sectors (18). 8. Process (B) according to claim 4 or 5, characterized in that the number of ring sectors (18) is identical to the number of distributor sectors (12i). 7. Method (B) according to claim 4 or 5, characterized in that the number of ring sectors (18) is smaller than the number of distributor sectors (12-i). 8. Method (B) according to one of claims 4 to 7, characterized in that step f) comprises a sub-step of reporting and fixing anti-rofation means (50) on the ring sectors (18). ), and to form notches (52) or holes in a housing rail (30), these notches or orifices being configured to receive said anti-rotation means. 9. Method (B) according to claim 8, characterized in that the anti-rotation means (50) of the ring sectors (18) are identical and positioned in the same way on all the ring sectors so that they are identical and therefore interchangeable.