EP1731839B1 - System for fixing an injection system to the dome of turbine combustion chamber and method of fixation - Google Patents

Description

TECHNICAL AREA

The invention relates to a system for fixing an injection system on a turbojet engine combustion chamber bottom.

The combustion chambers of the turbojet engines comprise an inner wall and an outer wall connected at their upstream end by an annular bottom to define a combustion chamber bottom. Regularly distributed injection systems on the periphery of the bottom of the combustion chamber deliver a mixture of air and fuel which is ignited to provide combustion gases.

Each injection system includes a venturi in which air and fuel mix. A bowl, located downstream of the venturi, has the function of bursting the jet of air / fuel mixture leaving the venturi. In addition, a deflector protects the chamber bottom of the flames of the combustion chamber.

The document US 6,502,400 B1 shows a fastening system according to the preamble of claim 1.

In a known realization ( US 4,584,834 ) the injection system is mounted downstream that is to say from the rear of the turbojet engine. In a system of this type, the injection system is brazed to the chamber bottom directly or through an intermediate piece; the deflector and the bowl are brazed on the injection system. If the solder between the injection system and the bowl gives way, the latter comes crashing the combustion chamber and the downstream part of the engine, including the HP turbine, which can lead to an explosion of the engine. In the same way, if the brazing situated between the injection system and the deflector gives way, the latter will initially be retained by the bowl but the additional forces exerted on the bowl will eventually also give up the solder located between the injection system and the bowl so that the two parts will be projected simultaneously in the combustion chamber and in the downstream part of the engine with the same consequences as before.

In addition, apart from this problem of risk of breaking a solder, it is difficult to disassemble an injection system to ensure its maintenance or replacement. Indeed, this operation requires removing three solders at the same time, which is difficult and usually requires the sacrifice of a part, usually the injection system itself. The present invention relates to an injection system and a fixing method that overcomes these disadvantages.

These aims are achieved by the fact that the deflector comprises an annular portion having a shoulder forming a retaining shoulder directed towards the front of the turbojet and the fact that the injection system comprises a collar on which is formed a retaining shoulder. directed towards the rear of the turbojet and bearing against the retaining shoulder of the deflector.

In one embodiment, the baffle has a retaining groove and a retaining ring has a rim inserted into the retaining groove.

With these characteristics, the deflector is always mounted by the downstream part of the chamber but is mechanically retained by the flange of the retaining ring inserted into its retaining groove. Thus, even in case of breakage of the solder between the chamber bottom and the deflector, the latter can not be sucked into the combustion chamber.

On the other hand, the bowl of the injection system is mounted by the front part of the turbojet engine. Its retaining shoulder provides a mechanical attachment so that it can not, either, be sucked into the combustion chamber of the turbojet engine.

Advantageously, the deflector and the retaining ring are brazed in the same brazing operation.

The injection system is attached to the retaining ring by welding beads.

These weld seams do not provide mechanical strength since the forces are taken up by the retaining shoulder of the injection system. They are therefore less likely to break, and even if this were to happen, the injection system would still be held in front of the chamber floor.

In a particular embodiment, the retaining ring is a split ring.

In another embodiment, the flange of the injection system further comprises a shoulder directed towards the front of the turbojet engine and the retaining ring has a second flange which blocks the second shoulder of the injection system.

In a particular embodiment the retaining ring consists of a split inner ring or formed of two half rings and a closure ring which surrounds the inner ring.

Advantageously, the split ring has a conical bearing to eliminate axial play.

The inner ring is attached to the closure ring by welding points.

Advantageously, the first shoulder directed towards the front of the turbojet and the second shoulder directed towards the rear of the turbojet engine are formed on a collar of a bowl forming part of the injection system.

• on introduit un déflecteur comportant une partie annulaire présentant un chant formant un épaulement de retenue dirigé vers l'avant du turboréacteur dans un trou du fond de chambre ;
• on monte une bague de retenue sur le déflecteur par l'avant du turboréacteur ;
• on brase le déflecteur sur le fond de chambre et simultanément la bague de retenue sur le déflecteur ;
• on introduit par l'avant du turboréacteur un système d'injection dans le déflecteur, le système d'injection comportant un épaulement dirigé vers l'arrière du turboréacteur qui vient prendre appui sur l'épaulement de retenue du déflecteur ;
• on soude le système d'injection sur la bague de retenue par des cordons de soudure.

According to the method of fixing an injection system on a turbojet combustion chamber bottom:

• introducing a baffle having an annular portion having a singing forming a retaining shoulder directed towards the front of the turbojet in a hole of the chamber bottom;
• a retaining ring is mounted on the deflector by the front of the turbojet engine;
• the deflector is pressed against the chamber bottom and simultaneously the retaining ring on the deflector;
• an injection system is introduced through the front of the turbojet engine into the deflector, the injection system having a shoulder directed towards the rear of the turbojet which comes to rest on the retaining shoulder of the deflector;
• the injection system is welded to the retaining ring by welding beads.

• on introduit un déflecteur comportant une partie annulaire présentant un chant formant un épaulement de retenue dirigé vers l'avant du turboréacteur dans un trou du fond de chambre, le déflecteur comportant une gorge de retenue ;
• on brase le déflecteur sur le fond de chambre ;
• on introduit par l'avant du turboréacteur un système d'injection dans le déflecteur le système d'injection comportant un premier épaulement dirigé vers l'arrière du turboréacteur qui vient prendre appui sur l'épaulement de retenue du déflecteur et un second épaulement dirigé vers l'avant du turboréacteur ;
• on monte une bague de retenue comportant un premier rebord qui vient se loger dans la gorge de retenue du déflecteur et un second rebord qui vient bloquer le second épaulement du système d'injection ;
• on fixe le système d'injection sur le déflecteur en réalisant des cordons de soudure entre la bague de retenue et la bague de fermeture.

According to a variant of the process:

• introducing a deflector comprising an annular portion having a singing forming a retaining shoulder directed towards the front of the turbojet in a hole of the chamber bottom, the deflector having a retaining groove;
• the deflector is pressed against the chamber floor;
• a injection system is introduced through the front of the turbojet into the deflector, the injection system comprising a first shoulder directed towards the rear of the turbojet which bears on the retaining shoulder of the deflector and a second shoulder directed towards the the front of the turbojet engine;
• mounting a retaining ring having a first rim which is housed in the retaining groove of the deflector and a second rim which blocks the second shoulder of the injection system;
• the injection system is fixed on the deflector by producing weld beads between the retaining ring and the closure ring.

Other features and advantages of the invention will become apparent upon reading the following description of exemplary embodiments given by way of illustration with reference to the appended figures.

• la figure 1 est une vue en coupe d'un premier mode de réalisation d'un système d'injection conforme à la présente invention ;
• la figure 2 est une vue de détail agrandie de la figure 1 ;
• la figure 3 est une demie vue en coupe d'un deuxième mode de réalisation du système de fixation de l'invention ;
• la figure 4 est une vue en perspective du bol monté sur le déflecteur du système d'injection de la figure 3 ;
• la figure 5 est une vue en coupe d'un troisième mode de réalisation du système de fixation de l'invention.

In these figures:

• the figure 1 is a sectional view of a first embodiment of an injection system according to the present invention;
• the figure 2 is an enlarged detail view of the figure 1 ;
• the figure 3 is a half sectional view of a second embodiment of the fastening system of the invention;
• the figure 4 is a perspective view of the bowl mounted on the deflector of the injection system of the figure 3 ;
• the figure 5 is a sectional view of a third embodiment of the fastening system of the invention.

On the figure 1 , the injection system, generally designated by the general reference 2 consists of a fixed part consisting of a ring 4, a twist 6, a venturi 8 and a bowl 10. The spin 6 and the bowl 10 are connected to each other by an intermediate ring 12. A sliding bushing 14 is slidably mounted on the ring 4. The auger has two stages of blades which have the function of driving the air in rotation around the longitudinal axis YY of the injection system. The bowl 10 has a flared shape 16 whose function is to burst the jet of the mixture of air and fuel leaving the venturi 8.

A deflector 20 is mounted on the chamber bottom 22. The chamber bottom itself has two clamping zones 24 and 26. The clamping zone 24 is connected to an outer chamber wall (not shown) and the inner clamping area 26 is connected to an inner chamber wall, also not shown. A plurality of injection systems, typically thirteen to thirty two, regularly spaced angularly are mounted on the chamber bottom 22 (only one injection system has been shown on the figure 1 ).

The deflector 20 comprises a plate 30 and an annular portion 32 brazed to the chamber bottom. The plate 30 serves to protect the part of the chamber bottom located around the injection system 2 of the flames of the combustion chamber. The annular portion 32 is inserted into a hole 33 formed in the chamber bottom. It comprises a shoulder 100 which bears against the downstream wall of the chamber bottom. Internally, the annular portion 32 has a bore 36 in which is housed a cylindrical portion 38 of the bowl 10. In addition, the annular portion 32 of the deflector comprises a retaining groove 40. The edge 42 of the annular portion 32 of the deflector constitutes a retaining shoulder. The cylindrical portion 38 of the bowl 10 is extended by a flange 44 of larger diameter having a retaining shoulder 46 directed towards the rear of the turbojet and bearing against the retaining shoulder 42 of the baffle. A split retaining ring 50 has a flange 52 inserted into the retaining groove 40 of the deflector 20. Welding beads 54, for example three or four (see FIG. figure 2 , provide a connection between the flange 44 of the bowl 10 and the retaining ring 50.

The assembly of the injection system on the chamber floor is carried out as follows. Firstly, the baffle 20 is inserted into the hole 33 made in the chamber bottom and the split retaining ring 50 is mounted on the deflector in such a way that the flange 52 is housed inside the retaining groove. annular 40 of the deflector. These two parts are then assembled together and at the chamber bottom 22 by a single brazing operation. The injection system is then mounted by the front of the turbojet, as shown schematically by the arrow 56 ( figure 1 ) so that the cylindrical portion 38 of the bowl comes to be mounted within the bore 36 of the baffle. In this position the shoulder 46 formed on the portion 44 of the bowl bears on the edge 42 of the annular portion 32 forming a retaining shoulder. Advantageously, the front end of the portion 44 is at the same level as the front end of the split ring 50 so that it is possible to produce weld beads 54 to secure these two parts.

In this embodiment, as can be seen, the deflector 20 is mechanically retained by the flange 52 of the split ring 50. In this way, even assuming that the solder connecting the deflector to the chamber bottom 22 comes to yield, the latter can not be sucked into the front part of the turbojet. On the other hand, the injection system 2, and more particularly the bowl 10, are mounted by the front of the turbojet and they are mechanically retained by the abutment of the shoulder 46 of the flange 44. of the bowl against the shoulder of the deflector 42. Thus, the weld points 54 do not provide mechanical strength but simply function to prevent the rotation of the injection system 2 relative to the split ring 50.

Furthermore, the disassembly operations of the injection system are facilitated, for example when it is desired to replace a defective injection system. It suffices to grind the welding beads 54, which releases the injection system and allows it to be removed by moving it in a direction opposite to the direction of the arrow 56 ( figure 1 ). The solder baffles on the chamber bottom and the split ring on the baffle are not affected. In the same way, the introduction of the new injection system is very simple since it is sufficient to insert it into the bore 36 and redo new welding beads 54. Thus, this device provides many advantages, on the one hand because it eliminates the risk that parts are entrained in the combustion chamber and in the downstream part of the engine, in particular the high pressure turbine, and secondly because it facilitates the operations of maintenance and repair making it much easier to replace a defective injection system.

We have shown on the figure 3 an alternative embodiment of the fastening system of figures 1 and 2 .

In the embodiment of figures 1 and 2 , as explained, neither the deflector nor the injection system bowl can not be driven to the rear of the turbojet in case of breakage of solders because they are mechanically retained. However, if a bias is exerted on the injection system in opposite direction, that is to say in the opposite direction to that of the arrow 56 of the figure 1 , the effort will be taken up by the weld seams which can then give way. A solicitation of this type can occur when the injectors are placed on the sliding bushing because there may be an arcboutement of the injectors. The forces experienced by the weld points in such a situation could eventually cause them to break. In this case, the bowl would be separated from the bottom chamber 22. This situation would have fewer disadvantages than the opposite situation in which the bowl could be driven to the rear of the turbojet because the injection system would be maintained by the injectors and the pressure. However, in order to avoid this drawback, an embodiment of the invention represented on the figures 3 and 4 wherein the injection system, and particularly the bowl part of the injection system, is mechanically retained in both directions without any effort being exerted on the weld seams.

In this embodiment, the shape of the deflector 20 is identical. On the other hand, the constitution of the retaining ring differs. The retaining ring 60 consists of an inner ring 62 and a closure ring 64. The inner ring can be split as in the embodiment previous or it may consist of two half rings. It comprises, as before, a flange 52 which is housed in the groove 40 of the baffle and further a second flange 66 which immobilizes a flange 44 located at the end of the cylindrical portion 38 of the bowl. The flange 44 is thus immobilized in both directions. Towards the rear of the turbojet, it is immobilized as previously by the edge 42 of the annular portion of the deflector 20. In the other direction, that is to say towards the front of the turbojet, it is immobilized by the second flange 66 of the inner ring 62. The closure ring 64 circles the inner ring 62 so as to prevent the split ring or the two half-rings from moving apart. Welding beads 54 solidify the closure ring 64 and the inner ring 62. However, in this embodiment, unlike the previous one, the weld beads 54 do not support any mechanical load. The stop in translation of the injection system, in both directions being provided exclusively by the flanges 52 and 66. However, as can be seen on the figure 4 it is necessary to provide anti-rotation means. Indeed, in the embodiment of figures 1 and 2 , anti-rotation function is provided by the solder points 54 themselves, which is no longer the case in the present embodiment. That is why ( figure 4 ), the deflector comprises a lug 70, of section for example substantially rectangular, which is housed in a corresponding notch 72 of the same shape and the same section formed in the collar 44 of the bowl 10. On thus ensures immobilization in rotation of the bowl relative to the deflector which is itself brazed to the bottom wall as previously exposed.

We have shown on the figure 5 a third embodiment of the invention which combines the characteristics of the first mode and the second embodiment of the figures 1 and 2 on the one hand and 3 and 4 on the other hand. In this embodiment, the baffle 20 is fixed to the chamber bottom 22 both by brazing and mechanically by means of a brazed split ring 150 having a flange 152 which penetrates into a circular groove 140 formed in the annular portion 32 of the deflector 20. This embodiment is similar to the embodiment of the figures 1 and 2 . Furthermore, the annular portion of the deflector comprises a second circular groove 158 intended to receive one of the flanges of a retaining ring 160. As described above with reference to the figures 3 and 4 , the retaining ring consists of an inner ring 162 and a closure ring 164 which surrounds the inner ring 162.

As before, the inner ring 162 may be constituted by a split ring or by two half rings. The inner ring has a first flange 166 and a second flange 168. The inner ring has tapered bearing surfaces for removing axial clearances. The axial forces tending to open the split ring or the two half rings are taken up by the closure ring 164. Welding beads 154 provide a connection between the inner ring 162 and the closure ring 164. These weld seams are not mechanically stressed.

This embodiment also works if the staves are not tapered. There then remains a slight axial play due to manufacturing tolerances.

Claims (13)

1. A system of attaching an injection system (2) to a turbojet combustion chamber base (22), the system comprising a deflector (20) brazed onto the chamber base (22), characterized in that the deflector comprises an annular portion (32) having an edge (42) forming a retaining shoulder directed toward the front of the turbojet and wherein the injection system (2) comprises a collar (44) on which is formed a retaining shoulder (46) directed toward the rear of the turbojet and pressing against the retaining shoulder (42) of the deflector (20).
2. The attachment system as claimed in claim 1, characterized in that the deflector (20) comprises a retaining groove (40) and wherein a retaining ring comprises a rim (52) inserted into the retaining groove.
3. The attachment system as claimed in one of claims 1 or 2, characterized in that the retaining ring (50) and the deflector (20) are brazed in one and the same welding operation.
4. The attachment system as claimed in claim 3, characterized in that the injection system (2) is attached to the retaining ring (50) by seam welds (54).
5. The attachment system as claimed in one of claims 3 or 4, characterized in that the retaining ring (50) is a split ring.
6. The attachment system as claimed in one of claims 1 or 2, characterized in that the collar (44) of the injection system (2) also comprises a second shoulder (68) directed toward the front of the turbojet and wherein the retaining ring comprises a second rim (66) that comes to immobilize the second shoulder (68) of the injection system.
7. The attachment system as claimed in claim 6, characterized in that the retaining ring (60) consists of an inner ring (62) that is split or formed of two half-rings and a fastening ring (64) which encircles the inner ring (62).
8. The attachment system as claimed in claim 7, characterized in that the inner ring has conical bearing surfaces.
9. The attachment system as claimed in one of claims 6 to 8, characterized in that the first shoulder of the injection system directed toward the rear of the turbojet and wherein the second shoulder of the injection system directed toward the front of the turbojet are formed on a collar of a bowl forming part of an injection system (2).
10. A combustion chamber fitted with an attachment system as claimed in one of claims 1 to 9.
11. A turbomachine comprising a combustion chamber as claimed in claim 10.
12. A method of attaching an attachment system to a turbojet combustion chamber base (22), characterized in that:

    - a deflector (20) comprising an annular portion (32) having an edge (42) forming a retaining shoulder directed toward the front of the turbojet is inserted into a hole (33) of the chamber base;

    - a retaining ring (50) is mounted onto the deflector via the front of the turbojet;

    - the deflector is brazed onto the chamber base and simultaneously the retaining ring is welded onto the deflector;

    - via the front of the turbojet, an injection system (2) is inserted into the deflector (20), the injection system (2) comprising a shoulder directed toward the rear of the turbojet that comes to press on the retaining shoulder of the deflector (20);

    - the injection system (2) is welded onto the retaining ring by seam welds (54).
13. A method of attaching an injection system (2) to a turbojet combustion chamber base (22), characterized in that:

    - a deflector (20) comprising an annular portion (32) having an edge (42) forming a retaining shoulder directed toward the front of the turbojet is inserted into a hole (33) of the chamber base, the deflector comprising a retaining groove;

    - the deflector (20) is welded onto the chamber base;

    - via the front of the turbojet, an injection system (2) is inserted into the deflector (20), the injection system (2) comprising a first shoulder directed toward the rear of the turbojet that comes to press on the retaining shoulder of the deflector and a second shoulder directed toward the front of the turbojet;

    - a retaining ring comprising a first rim that comes to lodge itself in the retaining groove of the deflector and a second rim that comes to immobilize the second shoulder of the injection system are mounted;

    - the injection system is attached with the deflector by producing seam welds (54) between the retaining ring and the fastening ring.

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