FR3057333A1 - CLAMPING ASSEMBLY WITH SEAL - Google Patents

Abstract

The invention relates to an assembly comprising a first annular piece (16) carrying a first annular flange (24) applied and held by clamping means (32) on a second annular flange (26) of a second piece (22) defining with the first flange an annular cavity (34) formed partly in the first flange (24) and for another part in the second flange (26), characterized in that the cavity (34) is arranged radially outside the clamping means (32) and accommodating an annular seal (36) circumferentially and axially constrained between the first flange (24) and the second flange (26).

Description

Holder (s): SAFRAN AIRCRAFT ENGINES Simplified joint-stock company.

Extension request (s)

Agent (s): ERNEST GUTMANN - YVES PLASSERAUD SAS.

Pty CLAMPING ASSEMBLY WITH SEAL.

FR 3 057 333 - A1 ftY / The invention relates to an assembly comprising a first annular part (16) carrying a first annular flange (24) applied and held by clamping means (32) on a second annular flange (26) d '' a second part (22) defining with the first flange an annular cavity (34) formed partly in the first flange (24) and for another part in the second flange (26), characterized in that the cavity (34) is arranged radially outside the clamping means (32) and houses an annular seal (36) circumferentially and axially constrained between the first flange (24) and the second flange (26).

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CLAMP ASSEMBLY WITH SEAL

The present invention relates to the field of turbomachinery and more particularly the sealing at the junction between two casings of a turbomachine.

The housings of a turbomachine are generally annular, more specifically of substantially cylindrical or frustoconical shape and coaxial along a longitudinal axis of the turbomachine. Two adjacent housings each have an annular flange by which they are joined together, usually by bolting.

FIG. 1 shows a detail in section of a turbomachine 2 of the prior art, comprising a high pressure compressor 4 having, in an upstream part, and movable blades 6 and fixed blades 8, and in a downstream part, a centrifugal impeller 10 extended by a diffuser 12 rectifier supplying air to a combustion chamber 14 of the turbomachine 2.

The high pressure compressor 4 is delimited externally by an annular casing 16 in several parts. The axially downstream end of the casing 16 comprises a radial annular flange 18 assembled by bolting to a radial annular flange 20 upstream of an external annular casing 22 of the combustion chamber 14.

These two flanges 18, 20 define between them an annular housing in which an O-ring is inserted so as to avoid the passage of air between the flanges, from the inside of the casings to the outside, and vice versa.

Such an assembly is known from French patent application FR 2 891 606 in the name of the applicant, in which the O-ring is a seal widely used in trade such as a solid rubber seal.

However, the use of such a seal is not suitable for assembling an external casing of the combustion chamber with an external casing of the high pressure compressor of a turbomachine. In fact, in this zone of the turbomachine, the temperatures are very high, so that the deformation of the parts is significant. Thus, the joint must also be able to deform to accompany the expansion of the parts and thus, the evolution of the size of the housing in which it is located.

An ordinary joint, that is to say a commercial joint without particular characteristics, does not allow such a deformation and quickly loses its elasticity and reliability of sealing with high temperatures.

In addition, the temperature range to which the seal is subjected is large since, in addition to the high temperatures during operation of the turbomachine, the seal is subjected to ambient temperatures when the turbomachine is not in operation. These temperatures can in particular be negative, for example in winter or in the Scandinavian countries. Thus, the seal can be subjected to a sudden change in recurrent temperature during the various starts of the turbomachine. These sudden changes in temperature eventually lead to a degradation of the characteristics of the seal, and in particular of its flexibility and of its ability to adapt to the housing, therefore of its sealing power.

In addition, the proximity of the seal to the longitudinal axis of the turbomachine, and in particular of the combustion zone of the turbomachine, increases the risks of degradation of the seal.

The invention aims in particular to provide a simple, effective and economical solution to these problems.

To this end, the invention proposes, an assembly comprising a first annular piece carrying a first annular flange applied and held by clamping means on a second annular flange of a second piece defining with the first flange an annular cavity formed in part in the first flange and for another part in the second flange, characterized in that the cavity is arranged radially outside the clamping means and houses an annular seal constrained circumferentially and axially between the first flange and the second flange.

Such a seal can deform by opening as the two flanges, by the high temperature and pressure to which they are subjected, are pressed against each other. Thus, by deforming, the annular seal continues to ensure its sealing function.

The opening of the two flanges in their radially lower part relative to the clamping means generates a clamping of the flanges between them in their radially upper part so that the seal is immobilized between the two flanges pressed against each other by the pinch effect. The tightness between the flanges is thus reinforced.

In addition, this joint makes it possible to use fewer bolted connections for the benefit of the simplicity of production of the flanges since only a groove is necessary on each flange, a groove that can be obtained by turning, unlike the prior art for which each flange had to undergo a large number of holes and / or bores.

Advantageously, the annular cavity is delimited by a first axial annular groove of the first flange arranged opposite a second axial annular groove of the second flange, the first groove and the second groove forming together, in section, a Radially external continuous concave surface passing through the support plane of the first and second flanges and against which a complementary convex portion of the annular seal is forced.

The concave shapes of each of the grooves and their vis-à-vis position makes it possible to maintain the annular seal in a centered position so that during its deformation the seal is always constrained.

Preferably, the concave surface has the shape of an open circle, the free ends of which join at a point arranged radially away from the clamping means.

The spacing of the junction of the free ends of the concave surface makes it possible to limit the stresses of ruptures near the clamping zone. Thus, around the clamping zone of the two flanges one on the other, each flange comprises a zone full of material ensuring good clamping of flanges one on the other, this zone then presenting a low risk of rupture. mechanical stress.

In one aspect, the annular seal has a C section, the opening of which is oriented radially inward.

The inward orientation of the opening of the annular seal allows the seal to be pressed against the surface of the grooves by the pressure exerted by the air so as to ensure the sealing on either side of the flanges.

Advantageously, the first annular groove is symmetrical with the second annular groove with respect to a transverse plane, and / or the cavity has a symmetry of revolution.

This makes it possible in particular to facilitate the manufacture of each of the grooves, of the seal and the positioning of the seal in the grooves.

Preferably, the clamping means comprise a plurality of bolts, the screw of which passes through the first flange and the second flange radially inside the annular cavity.

The plurality of bolts makes it possible to keep the flanges in contact with one another and, thus, to keep the joint constrained in the groove.

Advantageously, the seal is a metal seal.

A metal joint will be more resistant to high temperatures and sudden (or at least rapid) variations in temperature and pressure. In addition, compared to a rubber seal and in connection with temperature variations, a metal seal will have a longer service life.

The invention also provides a turbomachine such as a turbojet or a turboprop, comprising an assembly such as qe previously described.

Advantageously, the first part is formed by an external casing of a high pressure compressor and the second part is formed by an external casing of a combustion chamber.

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 nonlimiting example with reference to the appended drawings in which:

- Figure 1 is a detailed sectional view of a turbomachine of the prior art showing the fixing by bolting of a high pressure compressor housing with a combustion chamber housing;

- Figure 2 is a schematic sectional view showing the sealing connection according to the invention of two annular flanges;

- Figure 3 is an exploded perspective view of the assembly of Figure 2, and

- Figure 4 is a sectional view of the seal of Figures 2 and 3 between the two flanges.

For the detailed description of the invention, reference will be made to FIG. 1 for the elements common with the prior art, the numerical references of which will be kept, except for the flanges which are different from the prior art and which will therefore bear new references. digital.

There is shown in Figure 2, a detailed view in section along a longitudinal plane, the assembly of a first annular flange 24 downstream of a first annular part, here the housing 16 of the high pressure compressor 4, ci- after casing 16 HP, with a second annular flange 26 upstream of a second annular part, here the casing 22 of the combustion chamber, hereinafter casing 22 C.

The casing 16 HP is located upstream of the casing 22 C, according to the direction of flow of the air in the turbomachine 2 (that is to say from left to right). The annular flange 24 of the casing 16 HP is provided with holes 28 circumferentially equidistant from each other (a single hole 28 being shown in FIG. 3).

The flange 26 of the casing 22 C is provided with holes 30 circumferentially equidistant from each other (a single hole 30 being shown in FIG. 3).

The housings 16, 22 are assembled to each other by tightening means 32, in this case bolts comprising a nut 32a and a screw 32b successively passing through the hole 28 of the flange 24 of the housing 16 HP and the hole 30 of the flange 26 of the casing 22 C. The assembly is considered to have been carried out when the flanges 24, 26 are applied and held one against the other.

When assembled with each other, the flanges 24, 26 form between them an annular cavity 34 in which is housed an annular seal 36.

As seen in Figures 2 and 3, the annular cavity 34 is formed partly in the flange 24 of the housing 16 HP and for another part in the flange 26 of the housing 22 C.

The annular cavity 34 is arranged radially outside the clamping means 32. In other words, the clamping means 32 are located radially between the longitudinal axis A of the turbomachine 2 and the annular cavity 34.

The cavity 34 is delimited by a first axial annular groove 34a of the annular flange 24 arranged opposite a second axial annular groove 34b of the annular flange 26, the first groove 34a and the second groove 34b forming together, in section, a radially external continuous concave surface 38 crossing a support plane P of the first and second flanges 24, 26.

The surface 38 concave in the form of an open circle the free ends of which join at a point 40 arranged radially away from the clamping means 32, on the plane P, outside the clamping means 32 in the radial direction .

Thus, in section, the annular groove 34 comprises a shape substantially in the form of an inverted drop of water, or else a portion of a radially external sphere combined with a radially internal cone.

As shown in the figures, the first annular groove 34a 5 is symmetrical with the second annular groove 34b relative to said support plane P, which is in this case a transverse plane.

In addition, the cavity has a symmetry of revolution around the longitudinal axis A of the turbomachine 2.

The annular seal 36 has a C section, the opening of which is oriented radially inwards when the seal 36 is mounted in the groove 34.

As shown in FIG. 4, the seal 36 has a convex central portion 36a and two lateral portions 36b, 36c on either side of the central portion 36a. In position, the seal 36 is constrained circumferentially and axially in the groove 34, the central convex portion 36a of the seal 36 being forced to bear against the concave surface 38 of the groove 34. The pressure P exerted on the seal 36 tends to press that -this against the walls 34a, 34b of the groove 34.

By constrained, it is meant that the seal 36 is elastically deformed, that is to say that in the absence of stresses, the seal 36 recovers its original shape.

Preferably, the seal 36 is a metal seal, for example produced by rolling a flat sheet.

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Claims (8)

1. Assembly comprising a first annular part (16) carrying a first annular flange (24) applied and held by means (32) of clamping on a second annular flange (26) of a second part (22) defining with the first flange an annular cavity (34) formed partly in the first flange (24) and for another part in the second flange (26), characterized in that the cavity (34) is arranged radially outside the means (32 ) tightening and houses an annular seal (36) circumferentially and axially constrained between the first flange (24) and the second flange (26). 2. The assembly of claim 1, wherein the annular cavity (34) is delimited by a first annular groove (34a) of the first axial flange (24) arranged opposite a second annular groove (34b) axial of the second flange (22), the first groove (34a) and the second groove (34b) together forming, in section, a concave surface (38) radially continuous passing through the plane (P) of support of the first and second flanges (24, 26) and against which is constrained a convex portion (34a) complementary to the annular seal (36). 3. The assembly of claim 2, wherein the concave surface (38) has the shape of an open circle whose free ends join at a point (40) arranged radially away from the clamping means (32) . 4. The assembly of claim 2 or 3, wherein the annular seal (36) has a C section whose opening is oriented radially inward. 5. Assembly according to one of claims 1 to 4, wherein the first annular groove (34a) of the first flange (24) is symmetrical with the second annular groove (34b) of the second flange (26) with respect to a support plane (P) of the first and second flanges (24, 26). 6. Together according to Moon any of claims previous, in which the cavity (34) presents a symmetry of revolution. 7. Together according to Moon any of claims 5 above, in which the clamping means (32) comprise a plurality of bolts, the screw (32b) of which passes through the first flange (24) and the second flange (26) radially inside the annular cavity (34). 8. Assembly according to any one of the preceding claims, in which the seal (36) is a metal seal. 9. Turbomachine (2) such as a turbojet or a turboprop, comprising an assembly according to any one of the preceding claims. 10. Turbomachine (2) according to claim 9 wherein the first part (16) is formed by an external annular casing 15 of a high pressure compressor (4) and the second part (22) is formed by an external casing of a combustion chamber (14). 1/2 2 = 3