EP3267111B1 - Annular wall of a combustion chamber with improved cooling at the primary and/or dilution holes - Google Patents

Description

Background of the invention

The present invention relates to the general field of turbomachine combustion chambers. It relates more particularly to an annular wall for a direct or reverse-flow combustion chamber cooled by a so-called “multiperforation” process.

Typically, a turbomachine annular combustion chamber is formed of an inner annular wall (also called inner shroud) and an outer annular wall (also called outer shroud) which are connected upstream by a transverse wall forming the bottom of the chamber.

The inner and outer shrouds are each provided with a plurality of various holes and orifices allowing air circulating around the combustion chamber to penetrate inside the latter.

Thus, so-called “primary” and “dilution” holes are formed in these shrouds to convey air inside the combustion chamber. The air passing through the primary holes contributes to creating an air/fuel mixture which is burned in the chamber, while the air coming from the dilution holes is intended to favor the dilution of this same air/fuel mixture.

The inner and outer shrouds are subjected to the high temperatures of the gases resulting from the combustion of the air/fuel mixture.

In order to ensure their cooling, additional so-called multiperforation orifices are also drilled through these shrouds over their entire surface. These multi-perforation orifices, generally inclined at 60°, allow the air circulating outside the chamber to penetrate inside the latter by forming films of cooling air along the shrouds.

However, in practice, it has been found that the area of the inner and outer shrouds which is located directly downstream of each of the primary or dilution holes, due in particular to the absence of orifices resulting from the laser drilling technology used , benefits from a low level of cooling with the risk of formation of cracks that this implies.

In order to solve this problem, the document US 6,145,319 proposes making transition holes in the area of the walls located directly downstream of each of the primary and dilution holes, these transition holes having a greater inclination than that of the multiperforation orifices. However, given that it is a localized treatment, this solution unfortunately proves to be particularly expensive and it notably increases the manufacturing time of the walls.

The document US 2007/0169484 A1 shows a turbomachine combustion chamber wall according to the preamble of claims 1 and 3 respectively.

Subject matter and summary of the invention

The object of the present invention is therefore to overcome such drawbacks by proposing an annular combustion chamber wall which ensures adequate cooling of the zones located directly downstream of the primary and dilution holes.

• une pluralité de trous primaires ou de trous de dilution répartis selon une rangée circonférentielle pour permettre à de l'air circulant du côté froid de ladite paroi annulaire de pénétrer du côté chaud afin respectivement de créer un mélange air/carburant ou d'assurer la dilution du mélange air/carburant ; et
• une pluralité d'orifices de refroidissement pour permettre à l'air circulant du côté froid de ladite paroi annulaire de pénétrer du côté chaud afin de former un film d'air de refroidissement le long de ladite paroi annulaire, lesdits orifices de refroidissement étant répartis selon une pluralité de rangées circonférentielles espacées axialement les unes des autres et les axes géométriques de chacun desdits orifices de refroidissement étant inclinés, dans une direction axiale D d'écoulement des gaz de combustion, d'un angle d'inclinaison θ1 par rapport à une normale N à ladite paroi annulaire ;
• une pluralité d'orifices additionnels de refroidissement disposés directement en aval desdits trous primaires ou de dilution et répartis selon une pluralité de rangées circonférentielles espacées axialement les unes des autres,

les axes géométriques de chacun desdits orifices additionnels de refroidissement étant disposés dans un plan perpendiculaire à ladite direction axiale D et inclinés d'un angle d'inclinaison θ2 par rapport à une normale N à ladite paroi annulaire, caractérisée en ce qu'elle comporte en outre, au niveau d'une zone de transition formée directement en aval de ladite pluralité de rangées d'orifices additionnels et directement en amont de ladite pluralité de rangées d'orifices de refroidissement, exactement deux rangées d'orifices dont les axes géométriques de chacun desdits orifices sont inclinés respectivement de 30° et 60°, par rapport à un plan perpendiculaire à ladite direction axiale D.For this purpose, an annular turbomachine combustion chamber wall is provided, comprising a cold side and a hot side, which may also comprise:

• a plurality of primary holes or dilution holes distributed along a circumferential row to allow air flowing on the cold side of said annular wall to penetrate on the hot side in order respectively to create an air/fuel mixture or to provide dilution the air/fuel mixture; and
• a plurality of cooling holes to allow the air circulating on the cold side of said annular wall to penetrate the hot side in order to form a film of cooling air along said annular wall, said cooling holes being distributed according to a plurality of circumferential rows spaced axially from each other and the geometric axes of each of said cooling holes being inclined, in an axial direction D of flow of the combustion gases, by an angle of inclination θ1 with respect to a normal N to said annular wall;
• a plurality of additional cooling orifices arranged directly downstream of said primary or dilution holes and distributed in a plurality of circumferential rows spaced axially from each other,

the geometric axes of each of said additional cooling orifices being arranged in a plane perpendicular to said axial direction D and inclined by an angle of inclination θ2 with respect to a normal N to the said annular wall, characterized in that it further comprises, at the level of a transition zone formed directly downstream of the said plurality of rows of additional orifices and directly upstream of said plurality of rows of cooling orifices, exactly two rows of orifices whose geometric axes of each of said orifices are inclined respectively by 30° and 60°, with respect to a perpendicular plane to said axial direction D.

The presence of additional cooling orifices arranged in an inclined manner in a plane perpendicular to the direction of flow of the combustion gases, directly downstream and as close as possible to the primary and dilution holes, makes it possible to ensure effective cooling with respect to the conventional axial multiperforation where the air film is stopped by the presence of these holes and this without modifying the flow in the primary zone. The gyratory-axial multi-perforation transition zone allows, by smoothing the flows, to reduce the thermal gradient at the origin of crack initiation. The average temperature profile at the chamber outlet is improved due to the more effective mixing thus obtained.

When it comprises two rows of orifices, said two rows of orifices are then either two rows of additional orifices arranged immediately upstream of a row of cooling orifices, or two rows of cooling orifices arranged immediately downstream of a row of additional orifices, or else a row of additional orifices and an adjacent row of cooling orifices.

When it comprises three rows of orifices, said geometric axes of each of said orifices are inclined respectively by 22.5°, 45° and 67.5°, with respect to a plane perpendicular to said axial direction D.

Advantageously, the direction of inclination of said additional orifices is constrained by the direction of flow of the air/fuel mixture downstream of said combustion chamber.

The present invention also relates to a combustion chamber and a turbomachine (having a combustion chamber) comprising an annular wall as defined above.

Brief description of the drawings

• la figure 1 est une vue en coupe longitudinale d'une chambre de combustion de turbomachine dans son environnement ;
• la figure 2 est une vue partielle et en développé de l'une des parois annulaires de la chambre de combustion de la figure 1 selon un mode de réalisation de l'invention ; et
• la figure 3 est une vue partielle et en perspective d'une partie de la paroi annulaire de la figure 2.

Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate an exemplary embodiment thereof which is devoid of any limiting character. In the figures:

• the figure 1 is a longitudinal sectional view of a turbomachine combustion chamber in its environment;
• the picture 2 is a partial and developed view of one of the annular walls of the combustion chamber of the figure 1 according to one embodiment of the invention; and
• the picture 3 is a partial perspective view of part of the annular wall of the picture 2 .

Detailed description of the invention

The figure 1 illustrates in its environment a combustion chamber 10 for a turbomachine. Such a turbomachine includes in particular a compression section (not shown) in which air is compressed before being injected into a chamber casing 12, then into the combustion chamber 10 mounted inside the latter. Compressed air is introduced into the combustion chamber and mixed with fuel before being burned there. The gases resulting from this combustion are then directed towards a high-pressure turbine 14 arranged at the outlet of the combustion chamber.

The combustion chamber is of the annular type. It is formed of an internal annular wall 16 and an external annular wall 18 which are joined upstream by a transverse wall 20 forming the bottom of the chamber. It can be direct as shown or reverse flow where a return elbow which can also be cooled by multi-boring is placed between the combustion chamber and the turbine nozzle.

The inner 16 and outer 18 annular walls extend along a longitudinal axis slightly inclined with respect to the longitudinal axis 22 of the turbomachine. The chamber bottom 20 is provided with a plurality of openings 20A in which fuel injectors 24 are mounted.

The chamber casing 12, which is formed of an inner casing 12a and an outer casing 12b, forms with the combustion chamber 10 annular spaces 26 into which is admitted compressed air intended for combustion, dilution and cooling of the chamber.

The internal 16 and external 18 annular walls each have a cold side 16a, 18a arranged on the side of the annular space 26 in which the compressed air circulates and a hot side 16b, 18b facing the interior of the combustion chamber ( picture 3 ).

The combustion chamber 10 is divided into a so-called "primary" zone (or combustion zone) and a so-called "secondary" zone (or dilution zone) located downstream from the previous one (downstream is understood in relation to a general axial flow direction of the gases resulting from the combustion of the air/fuel mixture inside the combustion chamber and materialized by the arrow D).

The air that supplies the primary zone of the combustion chamber is introduced through a circumferential row of primary holes 28 made in the internal 16 and external 18 annular walls of the chamber over the entire circumference of these annular walls. These primary holes have a downstream edge aligned on the same line 28A. As for the air supplying the secondary zone of the chamber, it passes through a plurality of dilution holes 30 also formed in the internal 16 and external 18 annular walls over the entire circumference of these annular walls. These dilution holes 30 are aligned along a circumferential row which is offset axially downstream with respect to the rows of primary holes 28 and they can have different diameters with in particular an alternation of large and small holes. In the configuration shown in picture 2 , these dilution holes of different diameters however then have a downstream edge aligned on the same line 30A.

In order to cool the annular inner 16 and outer 18 walls of the combustion chamber which are subjected to the high temperatures of the combustion gases, a plurality of cooling holes 32 are provided (illustrated in the figures 2 and 3 ).

These orifices 32, which provide cooling of the walls 16, 18 by multiperforation, are distributed according to a plurality of rows circumferential spaced axially from each other. These rows of multi-perforation orifices cover the entire surface of the annular walls of the chamber with the exception of particular zones which are the subject of the invention and which are precisely delimited and included between the line 28A, 30A forming an upstream transition axis and a transition axis downstream offset axially downstream with respect to this upstream axis and either substantially in front of the dilution holes (for the downstream axis 28B) or substantially in front of the exit plane of the chamber (for the downstream axis 30B).

The number and the diameter d1 of the cooling orifices 32 are identical in each of the rows. The pitch p1 between two orifices of the same row is constant and may or may not be identical for all the rows. Furthermore, the adjacent rows of cooling orifices are arranged so that the orifices 32 are staggered as shown in the picture 2 .

As illustrated on the picture 3 , the cooling orifices 32 generally have an angle of inclination θ1 with respect to a normal N to the annular wall 16, 18 through which they are pierced. This inclination θ1 allows the air passing through these orifices to form a film of air along the hot side 16b, 18b of the annular wall. Compared to non-inclined orifices, it makes it possible to increase the surface of the annular wall which is cooled. In addition, the inclination θ1 of the cooling orifices 32 is directed so that the film of air thus formed flows in the direction of flow of the combustion gases inside the chamber (schematized by the arrow D ).

By way of example, for an annular wall 16, 18 made of metallic or ceramic material and having a thickness of between 0.6 and 3.5 mm, the diameter d1 of the cooling orifices 32 can be between 0.3 and 1 mm, the pitch d1 comprised between 1 and 10 mm and their inclination θ1 comprised between +30° and +70°, typically +60°. By way of comparison, for an annular wall having the same characteristics, the primary holes 28 and the dilution holes 30 have a diameter of the order of 4 to 20 mm.

According to the invention, each annular wall 16, 18 of the combustion chamber comprises, arranged directly downstream of primary 28 and dilution 30 holes and distributed in several circumferential rows, typically at least 5 rows, from the axis of upstream transition 28A, 30A and up to the downstream transition axis 28B, 30B, a plurality of additional cooling orifices 34. However, unlike the previous cooling orifices which deliver a film of air flowing in the axial direction D, the film of air delivered by these additional orifices flows in a perpendicular direction due to their arrangement in a plane perpendicular to this axial direction D of flow of the combustion gases. This multi-perforation made perpendicular to the axis of the turbomachine (in the rest of the description, we will speak of gyratory multi-perforation as opposed to the axial multi-perforation of the cooling orifices) makes it possible to bring the additional orifices closer to the primary or dilution holes and therefore to improve the efficiency of the air/fuel mixture.

The additional orifices 34 of the same row have the same diameter d2, preferably identical to the diameter d1 of the cooling orifices 32, are spaced apart by a constant pitch p2 which may or may not be identical to the pitch p1 between the cooling orifices 32 and have an inclination θ2, preferably identical to the inclination θ1 of the cooling orifices 32 but arranged in a perpendicular plane. However, these characteristics of the additional orifices 34 can, while remaining within the ranges of values defined above, be substantially different from those of the cooling orifices 32, that is to say that the inclination θ2 of the additional orifices of a same row with respect to a normal N to the annular wall 16, 18 may be different from that θ1 of the cooling orifices, and the diameter d2 of the additional orifices of the same row may be different from that d1 of the cooling orifices 32.

However, depending on the desired cooling need, the additional orifices 34 behind the row of primary holes 28 can also advantageously have characteristics in terms of inclination, diameter or pitch different from those arranged behind the row of dilution holes 30 and, more particularly, within the same zone a difference in the diameter d2 and the pitch p2 can also be made to densify this cooling in the most thermally stressed parts, that is to say those just downstream of the holes primary and large dilution orifices, when the latter are formed by alternating large and small orifices as illustrated in picture 2 .

Between the row of primary holes and that of the dilution holes, the introduction of the gyratory multiperforation makes it possible, by limiting the rise in the thermal gradient, to avoid the formation of cracks downstream of the primary holes 28. The multiperforation upstream of the dilution 30 from the downstream transition axis 28B remaining of the axial type, it is necessary to provide a transition zone made in two rows in which the additional cooling holes 34 are each arranged in an inclined plane, one of 30° and the other 60° with respect to the axial direction D, the other parameters, namely the diameter d2, the pitch p2 and the inclination θ2 of these additional holes in these inclined planes remaining unchanged.

Similarly, at the chamber outlet, more precisely from the downstream transition axis 30B ( picture 2 ), the introduction of the axial multiperforation makes it possible to fill the local level of gyration in order not to lose the TuHP efficiency of the combustion chamber. Preferably, it is also advisable to provide a gyratory-axial multi-perforation transition zone making it possible, by smoothing the flows, to reduce the thermal gradient at the origin of crack initiation. The average temperature profile at the chamber outlet is improved due to the more effective mixing thus obtained. This transition zone is made on two rows of additional cooling holes each arranged in an inclined plane, one of 30° and the other of 60° with respect to the axial direction D, the other parameters, namely the diameter d2 , the pitch p2 and the inclination θ2 of the additional holes in these inclined planes remaining unchanged. In the case of a reverse flow combustion chamber, this zone from axis 30B may not exist or be integrated into the return elbow.

It will be noted that if the transition zone has been described at the level of the gyratory multi-perforation, nothing however prohibits carrying it out at the level of the axial multi-perforation or even straddling a row of axial multi-perforation inclined at 30° and a row of gyratory multi-perforation inclined at 60°. Similarly, this transition zone can comprise three rows, the inclination of the orifices will then be 22.5°, 45° and 67.5° respectively.

With the invention, the flow in the primary zone is not modified, the gyration not impacting the orientation of the dilution jets and by being freed from the thermal barrier allows a saving in mass and therefore in cost. It should also be noted that to respect the direction of the flows in the DHP and avoid aerodynamic separations and thus preserve the efficiency of the high pressure turbine, the direction of the drilling of the gyratory multiperforation is fixed by the orientation of the blades of the High Pressure distributor ( DBH) downstream of the combustion chamber.

Claims (6)

1. Annular wall (16, 18) of a turbine engine combustion chamber (10), comprising a cold side (16a, 18a) and a hot side (16b, 18b), said annular wall comprising:

   . a plurality of primary holes (28) or dilution holes (30) distributed according to a circumferential row to allow circulating air of the cold side (16a, 18a) of said annular wall to enter the hot side (16b, 18b) to respectively create an air/fuel mixture or ensure dilution of the air/fuel mixture; and

   . a plurality of cooling orifices (32) to allow the circulating air of the cold side (16a, 18a) of said annular wall to enter the hot side (16b, 18b) to form a film of cooling air along said annular wall, said cooling orifices being distributed according to a plurality of circumferential rows spaced axially from one another and the geometric axes of each of said cooling orifices being inclined, in an axial direction D of flow of combustion gases, by an angle of inclination θ1 relative to a normal N to said annular wall;

   . a plurality of additional cooling orifices (34) arranged directly downstream of said primary holes or dilution holes and distributed according to a plurality of circumferential rows spaced axially from one another,
   the geometric axes of each of said additional cooling orifices being arranged in a plane perpendicular to said axial direction D and inclined by an angle of inclination θ2 relative to a normal N to said annular wall, characterized in that it further comprises at the level of a transition zone (28B, 30B) formed directly downstream of said plurality of rows of additional orifices (34) and directly upstream said plurality of rows of cooling orifices (32), exactly two rows of orifices whereof the geometric axes of each of said orifices are inclined of 30° and 60° respectively, relative to a plane perpendicular to said axial direction D.
2. Wall as claimed in Claim 2, characterised in that said two rows of orifices are two rows of additional orifices arranged immediately upstream of a row of cooling orifices, two rows of cooling orifices arranged immediately downstream of a row of additional orifices, or even a row of additional orifices and an adjacent row of cooling orifices.
3. Annular wall (16, 18) of a turbine engine combustion chamber (10), comprising a cold side (16a, 18a) and a hot side (16b, 18b), said annular wall comprising:

   . a plurality of primary holes (28) or dilution holes (30) distributed according to a circumferential row to allow circulating air of the cold side (16a, 18a) of said annular wall to enter the hot side (16b, 18b) to respectively create an air/fuel mixture or ensure dilution of the air/fuel mixture; and

   . a plurality of cooling orifices (32) to allow the circulating air of the cold side (16a, 18a) of said annular wall to enter the hot side (16b, 18b) to form a film of cooling air along said annular wall, said cooling orifices being distributed according to a plurality of circumferential rows spaced axially from one another and the geometric axes of each of said cooling orifices being inclined, in an axial direction D of flow of combustion gases, by an angle of inclination θ1 relative to a normal N to said annular wall;

   . a plurality of additional cooling orifices (34) arranged directly downstream of said primary holes or dilution holes and distributed according to a plurality of circumferential rows spaced axially from one another,
   the geometric axes of each of said additional cooling orifices being arranged in a plane perpendicular to said axial direction D and inclined by an angle of inclination θ2 relative to a normal N to said annular wall, characterized in that it further comprises at the level of a transition zone (28B, 30B) formed directly downstream of said plurality of rows of additional orifices (34) and directly upstream said plurality of rows of cooling orifices (32), exactly three rows of orifices whereof the geometric axes of each of said orifices are inclined of 22.5°, 45° and 67.5° respectively, relative to a plane perpendicular to said axial direction D.
4. Wall as claimed in any one of Claims 1 to 3, characterised in that the direction of inclination of said additional orifices is restricted by the direction of flow of the air/fuel mixture downstream of said combustion chamber.
5. Combustion chamber (10) of a turbine engine, comprising at least one annular wall (16, 18) as claimed in any one of Claims 1 to 4.
6. Turbine engine comprising a combustion chamber (10) having at least one annular wall (16, 18) as claimed in any one of Claims 1 to 4.

Images