EP1818612A1 - Annular combustion chamber of a turbomachine - Google Patents

Abstract

The combustion chamber (24), having inner and outer walls and a base (30) at the chamber's upstream end, and two metal coupling flanges (27, 29) for connecting the walls to other engine components, has the two walls divided into a number of sectors (126, 128) that are attached to the base of the chamber or to one of the flanges at two or more points (36, 36'). The lateral edges (128a) of the sectors, which are made from a composition material with a ceramic matrix, are inclined circumferentially relative to the main axis of the engine, and each one has a raised lip (60) creating an overlap that leaves a gap for cool air to enter the chamber from the outside.

Description

The invention relates to an annular combustion chamber of a turbomachine, of the type comprising an inner wall, an outer wall, a chamber bottom disposed between said walls in the upstream region of said chamber, and two fastening flanges arranged downstream. of the chamber bottom and for attaching respectively said walls to other parts of the turbomachine, usually inner and outer casings surrounding the combustion chamber.

Previously, said inner and outer walls of the chamber were made of metal or metal alloy and it was necessary to cool these walls so that they can withstand the temperatures reached during operation of the turbomachine.

Today, to reduce the volume of air allocated to the cooling of these walls, they are made of ceramic material rather than metal. In fact, ceramic materials are more resistant to high temperatures and have a lower density than commonly used metals. The gains made in cooling air and in mass make it possible to improve the efficiency of the turbomachine. It should be noted that the ceramic materials used are preferably ceramic matrix composite materials chosen for their good mechanical properties.

With regard to the chamber base and the attachment flanges, the state of the art leads to making these pieces of metal or metal alloy, rather than ceramic material, in order to be able to use the known fastening methods and tested to date, to fix the attachment flanges to the metal casings of the combustion chamber and the injection systems at the bottom of the chamber. It may be, for example, fasteners by welding or bolting.

However, the ceramics used to make the walls often have a coefficient of expansion about three times less than that of the metal materials used to make the chamber bottom and said flanges. Such a gap generates stresses in the assembled parts during their assembly, as well as during the temperature rise thereof during operation. These stresses can be the cause of cracking in the fastening flanges or in the walls, if these flanges are not sufficiently flexible, the ceramic materials being by nature quite fragile.

To solve this problem, a solution described in the document FR 2,855,249 , consists in providing a plurality of flexible fastening tabs connecting the chamber bottom audites walls, these tabs being able to deform elastically depending on the expansion gap between these parts.

The solutions described in the applications are also known FR 2,825,781 and FR 2,825,784 , consisting of connecting the walls to the casings of the combustion chamber by a plurality of flexible fasteners, elastically deformable, replacing the annular attachment flanges.

In all these documents of the prior art, the inner and outer walls of the combustion chamber are made in one piece of generally frustoconical shape.

The main disadvantage of known structures with flexible fastening tabs, lies in the poor dynamic behavior, during operation of the turbomachine, these fastening tabs and, it is often necessary to provide damping systems to limit the deformations of these paws and vibrations generated.

In addition, FR 2,855,249 there are spaces between the fastening tabs at the bottom of the chamber in which the fresh air rushes, which can degrade the efficiency of the combustion chamber by promoting the formation of pollutant emissions, such as for example, unburnt and / or carbon monoxide.

The invention aims to overcome these drawbacks, or at least to mitigate them, and aims to provide a combustion chamber having an alternative structure to structures with flexible fastening tabs, which is able to adapt to differences in expansion between the inner and outer walls, on the one hand, and the chamber bottom and the attachment flanges, on the other hand.

To achieve this object, the invention relates to an annular combustion chamber of the aforementioned type, characterized in that each wall of the chamber is divided into several adjacent sectors, each sector being attached to the chamber bottom and to one of Clamps.

Thanks to the partitioning of the walls, they can deform depending on the expansion of the chamber bottom and the attachment flanges (this expansion being greater than that of the walls). For example, during a rise in temperature, during which the chamber bottom and / or The attachment flanges expand (ie their diameters increase), the adjacent sectors of the walls deviate circumferentially so that the diameters of these walls increase. This avoids the creation of thermomechanical stresses in these parts.

Advantageously, the wall sectors are not attached to the chamber bottom and to the attachment flanges by means of flexible fasteners but, on the contrary, they are rigidly attached to these elements, for example by bolting. Thus, the structure has a better dynamic behavior in operation than a structure with flexible fastening tabs.

Advantageously, the sectors of the walls are provided with lateral edges and the lateral edges of two adjacent sectors overlap, so as to limit the passage of fresh air between the sectors, from the outside to the inside of the combustion chamber. . Indeed, such an air passage, if it is not controlled, causes the introduction of too much air into the chamber, which causes the formation of pollutant emissions such as, for example, unburned and carbon monoxide, and thus reduces the efficiency of the chamber. On the other hand, this passage of air, if it is controlled, can serve for the cooling of the walls, as explained hereafter.

Advantageously, it is desired to cool the inner faces of the inner and outer walls. It is therefore necessary that a certain volume of fresh air reaches these faces.

A known solution is to make a multitude of small perforations in said walls, through which calibrated volumes of fresh air pass. We usually talk about multiperforations. This solution nevertheless has the disadvantage of significantly increasing the cost price of said walls and cause a significant decrease in the characteristics of behavior and mechanical damage.

To solve this additional problem, the invention aims to provide an alternative to multiperforations, which is also more economical.

This objective is achieved thanks to the fact that there is a radial clearance (ie in a direction perpendicular to the axis at the axis of rotation of the turbomachine) between two overlapping adjacent sectors, this clearance allowing the passage of air cool from the outside to the inside of said chamber to cool the inner face of at least one of the sectors.

In this way, the fresh air coming from the outside of the chamber does not penetrate radially inside the chamber since the sectors overlap: it penetrates circumferentially while skirting, at least in part, the inner face of the chambers. inner and outer walls, so as to cool them. In addition, by playing on this radial clearance, it controls the amount of cooling air entering the chamber.

To increase the surface area of the inner faces of the walls benefiting from the cooling, the lateral edges of the sectors are inclined circumferentially with respect to the main axis of the combustion chamber, this main axis corresponding to the axis of rotation of the turbomachine.

In the present patent application, the circumferential direction at a point on the surface of a wall of the chamber is defined as the direction of the tangent to the wall, at this point, in a plane perpendicular to the axis of rotation. of the turbomachine. Thus, when the inner and outer walls are of generally frustoconical shape, it is considered that a lateral sectoral edge is inclined circumferentially with respect to the axis of rotation of the turbomachine, when this edge is inclined with respect to a generator of the wall concerned.

It should be noted that the presence of a radial clearance between the sectors is not, in itself, incompatible with the presence of multiperforations in these sectors.

• la figure 1 est une vue schématique, en demi-section axiale, d'une partie de turbomachine équipée d'une chambre de combustion selon l'invention ;
• la figure 2 est une vue en perspective partielle de la chambre de combustion de la figure 1, vue de l'amont ;
• la figure 3 est une vue en perspective partielle de la chambre de combustion de la figure 1, vue de l'aval ;
• la figure 4 est une demi-coupe axiale de la chambre de combustion de la figure 2, selon le plan IV-IV ; et
• la figure 5 est une vue de détail suivant le repère V de la figure 2.

The invention and its advantages will be clearly understood on reading the following detailed description of a non-limiting example of a combustion chamber according to the invention. This description refers to the accompanying drawings in which:

• FIG. 1 is a diagrammatic view, in axial half-section, of a turbomachine portion equipped with a combustion chamber according to the invention;
• Figure 2 is a partial perspective view of the combustion chamber of Figure 1, seen from upstream;
• Figure 3 is a partial perspective view of the combustion chamber of Figure 1, seen from downstream;
• Figure 4 is an axial half-section of the combustion chamber of Figure 2, in the plane IV-IV; and
• FIG. 5 is a detailed view along the reference V of FIG. 2.

• une enveloppe circulaire interne, ou carter interne 12, d'axe principal 10 correspondant à l'axe de rotation de la turbomachine, réalisée en alliage métallique ;
• une enveloppe circulaire externe, ou carter externe 14, coaxiale, également réalisée en alliage métallique ;
• un espace annulaire 16 compris entre les deux carters 12 et 14 recevant le comburant comprimé, généralement de l'air, provenant en amont d'un compresseur (non représenté) de la turbomachine, au travers d'un conduit annulaire de diffusion 18.

FIG. 1 shows, in axial half section, a portion of a turbomachine (turbojet, turboprop or land gas turbine) comprising:

• an inner circular casing, or inner casing 12, of main axis 10 corresponding to the axis of rotation of the turbomachine, made of metal alloy;
• an outer circular envelope, or outer casing 14, coaxial, also made of metal alloy;
• an annular space 16 between the two housings 12 and 14 receiving the compressed oxidant, generally air, coming upstream of a compressor (not shown) of the turbomachine, through an annular diffusion duct 18.

• un ensemble d'injection formé d'une pluralité de systèmes d'injection 20 régulièrement répartis autour du conduit 18 et comportant chacun une buse d'injection de carburant 22 fixée sur le carter extérieur 14 (dans un souci de simplification, le système de maintien 19, le mélangeur 21 et le déflecteur éventuel 23, associés à chaque buse d'injection 22 n'ont pas été représentés sur la figure 1, mais ces pièces apparaissent sur les figures 2 et 3) ;
• une chambre de combustion 24 comprenant une paroi circulaire 26 radialement interne et une paroi circulaire 28 radialement externe, toutes deux coaxiales d'axe 10, et une paroi transversale qui constitue le fond 30 de cette chambre de combustion et qui comporte deux rabats 32 et 34 attachés respectivement aux extrémités amont des parois 26, 28. Ce fond de chambre 30 est pourvu d'orifices de passage 40 pour permettre l'injection du carburant et d'une partie du comburant dans la chambre de combustion ;
• des brides d'accrochage interne 27 et externe 29, reliant respectivement les parois interne et externe 26 et 28 aux carters interne et externe 12 et 14 ; et
• un distributeur annulaire 42 en alliage métallique formant un étage d'entrée de turbine haute pression (non représentée) et comportant classiquement une pluralité d'aubes fixes 44 montées entre une plate-forme circulaire interne 46 et une plate-forme circulaire externe 48. Le distributeur 42 étant fixé aux carters 12 et 14 de la turbomachine par des moyens de fixation appropriés.

The space 16 comprises from upstream to downstream of the combustion chamber (upstream and downstream being defined with respect to the normal flow direction of the gases inside the turbomachine, indicated by the arrows F):

• an injection assembly formed of a plurality of injection systems 20 regularly distributed around the conduit 18 and each having a fuel injection nozzle 22 fixed to the outer casing 14 (for the sake of simplification, the holding system 19, the mixer 21 and the optional deflector 23, associated with each injection nozzle 22 have not been shown in Figure 1, but these parts appear in Figures 2 and 3);
• a combustion chamber 24 comprising a circular wall 26 radially inner and a circular wall 28 radially external, both coaxial axis 10, and a transverse wall which constitutes the bottom 30 of this combustion chamber and which comprises two flaps 32 and 34 attached respectively to the upstream ends of the walls 26, 28. This chamber bottom 30 is provided with through holes 40 to allow the injection of fuel and a portion of the oxidant into the combustion chamber;
• internal and external hooking flanges 29, respectively connecting the inner and outer walls 26 and 28 to the inner and outer casings 12 and 14; and
• an annular metal alloy distributor 42 forming a high pressure turbine inlet stage (not shown) and conventionally comprising a plurality of stationary vanes 44 mounted between a platform internal circular 46 and an outer circular platform 48. The distributor 42 is fixed to the casings 12 and 14 of the turbomachine by appropriate fastening means.

The chamber bottom 30 and the attachment flanges 27 and 29 are made of metal alloy, while the walls 26 and 28 of the chamber 24 are made of ceramic matrix composite material.

The walls 26 and 28 are respectively divided into several adjacent sectors 126 and 128. Each sector 126 (128) is attached to the chamber bottom 30, on the one hand, and to one of the attachment flanges 27 (29), on the other hand. At least one of these sectors may have multiperforations.

In operation, the chamber floor 30 may tend to rotate about the main axis 10 and angularly shift relative to the flanges 27 and 29. To prevent this, each wall sector 126 (128) is attached to the bottom of the chamber. 30 or one of the attachment flanges 27 (29) at two points of attachment, at least. Thus, each sector 126 (128) is prevented from pivoting relative to the chamber bottom and / or said flange, thereby preventing the angular displacement of the chamber floor 30. In the example, each sector 126 (128) is attached at the bottom of the chamber 30 and at an attachment flange 27 (29) at two attachment points 36 and 36 '.

Advantageously, at least one of these two attachment points 36 'is made by bolting, by passing a bolt 52, through at least one oblong hole 50. This oblong hole 50 can be formed in the flap 32 (34). of the chamber bottom 30, in the sector 126 (128) or in these two pieces at a time. This oblong hole 50 is oriented circumferentially and the bolt 52 can therefore move circumferentially inside the hole 50 as indicated by the double arrow B in FIG. 4. In the example of the figures, all the attachment points 36, 36 ', are made by bolting but only one fixing point 36' out of two is made by bolting through an oblong hole 50. To simplify the figures, only Figure 4 shows bolts 52.

With this type of fastening, when the bottom chamber 30 where the flanges 27, 29, expand or contract depending on the temperature, the fixing points 36, 36 'deviate or are close to one of the another and avoids the creation of thermomechanical stresses in each wall sector 126, 128.

With reference to Figures 2 and 5, we will now describe the particular manner in which the side edges 128a (126a) of two adjacent wall sectors 128 (126) overlap. Each sector 128 (126) includes a lip 60 extending along one of its side edges 128a (126a), preferably substantially the entire length thereof. The other side edge of the sector is devoid of lip and will be hereinafter referred to as simple edge 128b (126b).

The lip 60 projects from one of the inner or outer faces of the sector 128 (126) so as to cover the single edge 128b (126b) of the adjacent sector. In other words, the lip 60 is offset radially inwards or outwards with respect to the sector 128. In the example shown in FIG. 5, the lip 60 projects (outwards) by relative to the outer face of the sector 128. Alternatively, it could be projecting (inwards) relative to the inner face of the sector. The outer and inner faces 126, 128 being turned respectively outwardly and inwardly of the combustion chamber 24.

The lip 60 may be made directly during the manufacture of sector 128 (126), or during a subsequent machining step in its manufacture. The lip 60 may also consist of an added band, for example by gluing, on the lateral edge 128a (126a) of the sector.

According to the various cases, there is a radial clearance J, positive or zero, between the lip 60 and the surface of the single edge 128b (126b), as shown in FIG. 5. This clearance J, when it is positive, allows the fresh air passage following the arrows F 'from the outside to the inside of the chamber 24. This fresh air passes between the lip 60 and the single edge 128b, then through the slot 66 existing between two adjacent sectors, the width L of this slot 66 may vary depending on the spacing of the sectors 128 (126). In fact, the width L varies as a function of the differences in expansion between the chamber bottom 30, the attachment flanges 27, 29 and the wall segments 126, 128. Thus, the higher the temperatures are important inside the chamber. chamber 24, the more sectors 128 (126) deviate (L increases) and the better is the cooling. The ability to cool the walls of the chamber therefore adapts to the temperatures within it. Such an adaptation of the cooling makes it possible to reduce the quantity of cooling air taken off, when the temperatures inside the chamber are low. A system with only multiperforations does not provide such an advantage.

The fresh air flows outside the chamber 24 along the arrows F shown in Figure 1, that is to say in a direction more axial than radial. The clearance J and the slot 66 form a passage which deviates little enough the flow of fresh air F 'entering the combustion chamber 24. Thus, this air flow F' remains sufficiently inclined relative to the radial direction as 1 and 4 to, on the one hand, disturb as little as possible the combustion inside the chamber 24 and, on the other hand, create a protective film of fresh air along the inner face of the wall segments 126, 128, which limits the heating of these segments.

According to another aspect of the invention and with reference to FIG. 2, the lateral edges 126a, 126b, 128a, 128b of the sectors 126, 128 are inclined circumferentially with respect to the main axis of the combustion chamber. As indicated above, this circumferential inclination corresponds to an angle inclination y of the lateral edges relative to the generatrices G of the walls 126, 128. The flow of fresh air F, which circulates outside the chamber 24, goes from upstream to downstream. Tilting the side edges 126a, 126b, 128a, 128b and therefore the slots 66 for fresh air inlet allows to distribute the flow of fresh air F 'entering the chamber 24 in a cooling zone Z plus important that if said lateral edges were oriented along a generatrix G. This cooling zone Z is hatched in FIG. 2. The more the lateral edges 126, 128 are inclined, the more the zone Z is extended, and the better is the cooling of the sectors of walls 126, 128.

Thus, thanks to the invention, it is possible to control the cooling of the walls, 126, 128 by playing on the one hand on the clearance J and on the width L of the slots 66 and, on the other hand, on the inclination y of these slots with respect to the main axis 10.

Claims (9)

Annular combustion chamber (24) of a turbomachine, having a main axis (10) and comprising an inner wall (26), an outer wall (28), a chamber bottom (30) disposed between said walls in the upstream region of said chamber, and two attachment flanges (27, 29) arranged downstream of the chamber bottom and for respectively hanging said walls to other parts (12, 14) of the turbomachine, characterized in that each wall is divided into several adjacent sectors (126, 128), each sector being attached to the chamber bottom (30) and to one of the attachment flanges (27, 29) and in that the side edges (126a, 126b, 128a, 128b) sectors are inclined circumferentially with respect to said main axis (10). Combustion chamber according to claim 1, wherein said sectors (126, 128) are provided with lateral edges (126a, 126b, 128a, 128b) and in which the lateral edges of two adjacent sectors overlap. Combustion chamber according to claim 2, wherein there is a radial clearance (J) between two adjacent sectors (126, 128) which overlap, this clearance allowing the passage of fresh air (F ') from the outside to the outside. interior of said chamber. A combustion chamber according to any one of claims 1 to 3, wherein each sector (126, 128) comprises a lip (60) extending along one of its lateral edges (126a, 128a), said lip being projecting from one of the faces of the sector and covering the lateral edge (126b, 128b) of the adjacent sector. Combustion chamber according to any one of claims 1 to 4, wherein each wall sector (126, 128) is attached to the chamber base (30) or to one of the attachment flanges (27, 29) in two attachment points (36, 36 '), at least. Combustion chamber according to claim 5, wherein at least one of said attachment points (36 ') corresponds to a bolted fastener (52) through at least one oblong hole (50). Combustion chamber according to one of Claims 1 to 6, in which the chamber base (30) and the hooking flanges (27, 29) are metallic, whereas the wall sectors (126, 128) are ceramic matrix composite material. Combustion chamber according to any one of claims 1 to 7, wherein at least one of the sectors (126, 128) is provided with multiperforations. A turbomachine comprising a combustion chamber (24) according to any one of the preceding claims.

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