EP2771618B1 - 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 is more particularly an annular wall for direct combustion chamber or reverse flow cooled by a process known as "multiperforation".

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

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

Thus, so-called "primary" and "dilution" holes are formed in these ferrules to convey air inside the combustion chamber. The air passing through the primary holes helps to create an air / fuel mixture that is burned in the chamber, while the air from the dilution holes is intended to promote the dilution of the same air / fuel mixture.

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

To ensure their cooling, additional holes called multiperforation holes are also drilled through these ferrules over their entire surface. These multiperforation orifices, generally inclined at 60 °, allow the air circulating outside the chamber to penetrate inside thereof by forming cooling air films along the shells.

However, in practice, it has been found that the zone of the inner and outer rings which is situated directly downstream of each of the primary or dilution holes, in particular because of the absence of orifices resulting from the laser drilling technology used. , enjoys a low level of cooling with the risk of formation of cracks that implies.

In order to solve this problem, the document US 6,145,319 proposes to make transition holes in the zone of the walls situated directly downstream of each of the primary and dilution holes, these transition holes having a greater inclination than that of the multiperforation orifices. However, since it is a spot treatment, this solution is unfortunately particularly expensive and significantly increases the time of manufacture of the walls. The document US 2007/0084219 A1 shows an annular turbomachine combustion chamber wall according to the preamble of claim 1.

Object and summary of the invention

The present invention therefore aims to overcome such drawbacks by providing an annular combustion chamber wall which provides adequate cooling of the areas directly downstream of the primary and dilution holes.

For this purpose, there is provided an annular wall of a turbomachine combustion chamber according to claim 1. The presence of the 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 efficient cooling with respect to the classical axial multiperforation where the film of air is stopped by the presence of these holes and this without modifying the flow in the primary zone.

Preferably, it further comprises, at a transition zone formed downstream of said plurality of rows of additional orifices, at least two rows of orifices whose geometric axes of each of said orifices are inclined, with respect to a plane perpendicular to said axial direction D, of a different determined inclination for each of said two rows.

According to an advantageous embodiment of the invention, said inclination θ2 of said additional orifices relative to the normal N to said annular wall is identical to that θ1 of said cooling orifices.

Advantageously, a diameter d2 of said additional orifices is identical to a diameter d1 of said cooling orifices and a pitch p2 of said additional orifices is identical to a pitch p1 of said cooling orifices and said additional orifices may have a greater densification just downstream of the holes. primary and dilution holes.

When it comprises these two rows of orifices, said inclinations are 30 ° and 60 ° respectively. 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 in downstream of a row of additional orifices, or a row of additional orifices and a row of adjacent cooling orifices.

When it comprises several rows of orifices, said inclinations are regularly distributed between 0 ° and 90 °.

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 features and advantages of the present invention will emerge from the description given below, with reference to the accompanying drawings which illustrate an embodiment having no limiting character. In the figures:

• the figure 1 is a longitudinal sectional view of a turbomachine combustion chamber in its environment;
• the figure 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 figure 3 is a partial view in perspective of a part of the annular wall of the figure 2 .

Detailed description of the invention

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

The combustion chamber is of the annular type. It is formed of an inner annular wall 16 and an outer annular wall 18 which are joined upstream by a transverse wall 20 forming the chamber bottom. It can be direct as illustrated or reverse flow. In this case, a return bend that can also be cooled by multi-piercing is placed between the combustion chamber and the turbine distributor.

The inner annular walls 16 and outer 18 extend along a longitudinal axis slightly inclined relative 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, furnishes with the combustion chamber 10 annular spaces 26 into which compressed air for combustion is admitted. dilution and cooling of the chamber.

The inner annular walls 16 and outer 18 each have a cold side 16a, 18a disposed on the side of the annular space 26 in which the compressed air circulates and a hot side 16b, 18b turned towards the inside of the combustion chamber ( figure 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 of the previous one (the downstream means with respect to a general axial direction of flow of the gases resulting from the combustion of the air / fuel mixture inside the combustion chamber and represented by the arrow D).

The air that feeds the primary zone of the combustion chamber is introduced by a circumferential row of primary holes 28 formed in the inner annular walls 16 and outer 18 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 borrows a plurality of dilution holes 30 also formed in the inner annular walls 16 and outer 18 all around the circumference of these annular walls. These dilution holes 30 are aligned in a circumferential row which is axially offset downstream from the rows of the primary holes 28 and may have diameters different with alternating large and small holes. In the configuration illustrated in figure 2 these dilution holes of different diameters, however, present a downstream edge aligned on the same line 30A.

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

These orifices 32, which provide a cooling of the walls 16, 18 by multiperforation, are distributed in a plurality of circumferential rows spaced axially from each other. These rows of multiperforation orifices cover the entire surface of the annular walls of the chamber with the exception of specific areas which are the subject of the invention and are precisely delimited and situated between the line 28A, 30A forming an upstream transition axis and a transition axis. downstream axially offset downstream relative to this upstream axis and is substantially in front of the dilution holes (for the downstream axis 28B) is 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 be identical or not for all the rows. Furthermore, the adjacent rows of cooling orifices are arranged so that the orifices 32 are staggered as shown in FIG. figure 2 .

As illustrated on the figure 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. With respect 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 air film thus formed flows in the direction of flow of the combustion gases inside the chamber (represented by the arrow D ).

By way of example, for an annular wall 16, 18 made of metallic or ceramic material and having a thickness between 0.6 and 3.5 mm, the diameter d1 of the cooling orifices 32 may be between 0.3 and 1 mm, the pitch d1 between 1 and 10 mm and their inclination θ1 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 the primary holes 28 and dilution holes 30 and distributed in several circumferential rows, typically at least 5 rows, from the upstream transition axis 28A, 30A and up to the downstream transition axis 28B, 30B, a plurality of additional cooling orifices 34. However, unlike previous cooling orifices which deliver a film of air flowing in the axial direction D, the air film delivered by these additional orifices flows in a perpendicular direction due to their arrangement in a plane perpendicular to this axial direction D of flue gas flow. This multiperforation carried out perpendicularly to the axis of the turbomachine (in the following description, it will speak of multiperforation gyratory as opposed to the axial multiperforation of the cooling orifices) allows to bring the additional orifices of the primary holes or dilution and therefore d 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 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 may, while remaining within the previously defined ranges of values, be substantially different from those of the cooling orifices 32, that is to say that the inclination θ2 of the additional orifices of a The same row relative 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 of the cooling orifices 32.

However, depending on the desired cooling requirement, the additional orifices 34 behind the row of primary holes 28 may further advantageously have different inclination, diameter, or pitch characteristics than those disposed behind the row of dilution holes. and, more particularly, within the same zone a difference of the diameter d2 and the pitch p2 can also be achieved to densify this cooling in the most thermally stressed parts, that is to say those just downstream of the holes primary and large dilution ports, when these are formed alternately of large and small orifices as illustrated in figure 2 .

Between the row of the primary holes and that of the dilution holes, the introduction of the gyratory multiperforation allows limiting the rise of the thermal gradient to prevent the formation of cracks downstream of the primary holes 28. The multiperforation upstream of the holes of dilution 30 from the downstream transition axis 28B remaining axial type, it is necessary to provide a transition zone made for example in two rows in which the additional cooling holes 34 are 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 these additional holes in these inclined planes remaining unchanged.

Similarly, at the chamber outlet, more precisely from the downstream transition axis 30B ( figure 2 ), the introduction of the axial multiperforation makes it possible to fill the local level of gyration so as not to lose the TuHP efficiency of the combustion chamber. Preferably, it is also advisable to provide a gyratory-axial multiperforation 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 because of the more efficient mixture thus obtained. This transition zone may for example be made in two rows of additional cooling holes each disposed in a plane inclined at 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 the additional holes in these inclined planes remaining unchanged. In the case of a reverse-flow combustion chamber, this area from the 30B axis may not exist or be integrated with the return elbow.

Note that if the transition zone has been described at the level of the gyratory multiperforation, however, there is no prohibition to achieve it at the level of the axial multiperforation or still riding with a row of axial multiperforation inclined at 30 ° and a row of multiperforation gyratory inclined at 60 °. Similarly, this transition zone may comprise more than two rows, the inclination of the orifices then being evenly distributed between 0 ° (multiperforation axial) and 90 ° (multiperforation gyratory). For example, with three rows, the inclination of the orifices will be respectively 22.5 °, 45 ° and 67.5 °.

With the invention, the flow in the primary zone is not modified, the gyration does not impact the orientation of the dilution jets and overcoming the thermal barrier allows a gain in weight and therefore cost. Note also that to respect the flow direction in the DHP and avoid aerodynamic detachments and thus maintain the efficiency of the high pressure turbine, the direction of drilling of the multiperforation gyratory is fixed by the orientation of the blades of the High Pressure distributor ( DHP) downstream of the combustion chamber.

Claims (11)

1. An 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) 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 create an air/fuel mixture;

   . a plurality of 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 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; and

   . a plurality of additional cooling orifices (34) arranged on the one hand directly downstream of said primary holes and on the other hand directly downstream of said dilution holes and distributed according to a plurality of circumferential rows spaced axially from one another,

   characterised in that the geometric axes of each of said additional cooling orifices (34) are 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.
2. The wall as claimed in Claim 1, characterised in that said inclination θ2 of said additional orifices (34) relative to the normal N to said annular wall is identical to that θ1 of said cooling orifices.
3. The wall as claimed in Claim 1 or Claim 2, characterised in that a diameter d2 of said additional orifices (34) is identical to a diameter d1 of said cooling orifices (32) and a pitch p2 of said additional orifices is identical to a pitch p1 of said cooling orifices.
4. The wall as claimed in Claim 1, characterised in that said additional orifices (34) exhibit greater densification just downstream of the primary holes and the dilution holes.
5. The wall as claimed in any one of Claims 1 to 4, characterised in that it further comprises at the level of a transition zone (28B, 30B), formed downstream of said plurality of rows of additional orifices, at least two rows of orifices whereof the geometric axes of each of said orifices are inclined, relative to a plane perpendicular to said axial direction D, by an inclination determined as different for each of said two rows.
6. The wall as claimed in Claim 5, characterised in that it comprises two rows of orifices and said inclinations are 30° and 60° respectively.
7. The wall as claimed in Claim 6, 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.
8. The wall as claimed in Claim 5, characterised in that it comprises several rows of orifices and said inclinations are distributed evenly between 0° and 90°.
9. The wall as claimed in any one of Claims 1 to 8, 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.
10. A combustion chamber (10) of a turbine engine, comprising at least one annular wall (16, 18) as claimed in any one of Claims 1 to 9.
11. A turbine engine comprising a combustion chamber (10) having at least one annular wall (16, 18) as claimed in any one of Claims 1 to 9.

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