EP1634021B1 - Annular combustion chamber for a turbomachine - Google Patents

Description

TECHNICAL AREA

The present invention relates generally to the field of turbomachine annular combustion chambers, and more particularly to that of means for thermally protecting these combustion chambers.

STATE OF THE PRIOR ART

Typically, an annular turbomachine combustion chamber comprises an outer axial wall and an inner axial wall, these walls being arranged coaxially and interconnected via a chamber bottom.

At the bottom of the chamber of similarly annular shape, the combustion chamber is provided with angularly spaced injection ports, each of which is intended to receive a fuel injector in order to allow the combustion reactions to take place. inside this combustion chamber. It is furthermore noted that these injectors can also make it possible to introduce at least part of the air intended for combustion, which occurs in a primary zone of the combustion chamber situated upstream of a secondary zone. said dilution zone.

In this regard, it is noted that apart from the air requirements required to ensure combustion reactions within the primary zone of the combustion chamber, the latter also requires dilution air generally introduced through dilution orifices on the outer and inner axial walls, and also cooling air capable of protecting all components of the combustion chamber.

According to a known embodiment of the prior art, deflectors are arranged on the chamber bottom, in order to protect it from thermal radiation. Each deflector, also called cup or heat shield, then has at least one injection port for receiving a fuel injector, and a plurality of perforations for passing cooling air inside the nozzle. combustion chamber.

However, the addition of such deflectors generates major drawbacks. Indeed, among these disadvantages, it may be mentioned that it is imperative to allocate a large cooling air flow to cool these baffles. In such a case, the flow of cooling air passing through the perforations made is then evacuated in the form of a "baffle flow" also abundant, which generates freezing effects near the wall and which therefore results in the creation of species of the type CO and CH _x . Consequently, the appearance of such species inside the combustion chamber causes a non-negligible decrease in the combustion efficiency.

On the other hand, it is also indicated that the presence of deflectors is reflected directly by the creation of a strong thermal gradient between the cold parts and the hot parts of the chamber, as well as by a very detrimental increase in the total mass of this combustion chamber.

In an attempt to overcome these drawbacks, it has been proposed another type of combustion chamber, in which the baffles have been removed. Thus, the injection orifices are directly made in the chamber bottom, in the same way as the perforations which are then intended to allow the passage of a flow of cooling air capable of cooling the chamber bottom itself, this cooling air flow being advantageously less than that required in the case of use of deflectors. The documents US 6,155,056 A and US 5,307,637 A describe a combustion chamber of this type. However, with such an embodiment, it has been found that the presented perforations generated either a disturbance of the combustion reactions in the primary zone, or thermal discontinuities at the junctions between the chamber bottom and the external and internal axial walls.

STATEMENT OF THE INVENTION

The invention therefore aims to provide a turbomachine annular combustion chamber, at least partially overcoming the disadvantages mentioned above relating to the embodiments of the prior art.

More specifically, the object of the invention is to present an annular combustion chamber of turbomachine, whose means used to cool the chamber bottom generate neither significant disturbance of the combustion reactions inside the combustion chamber nor thermal discontinuities at the junctions between the chamber bottom and the external axial walls and internal.

For this purpose, the subject of the invention is an annular turbomachine combustion chamber, comprising an outer axial wall, an inner axial wall and a chamber bottom connecting the axial walls, the chamber bottom having a plurality of orifices. injection ports and a plurality of perforations, the injection ports being intended to allow at least the injection of fuel inside the combustion chamber and the perforations being intended to allow the passage of a flow cooling air suitable for cooling the chamber bottom. According to the invention, the bottom chamber is provided on the one hand with an outer portion on which the perforations are made so as to direct a portion of the cooling air flow towards the outer axial wall, and on the other hand, an inner portion on which the perforations are made to direct another portion of the cooling air flow to the inner axial wall, and the chamber is designed such that in axial half-section , taken in any manner between two directly consecutive injection orifices, the value of the acute angles formed between a substantially median line of the half-section situated between the external axial wall and the axial wall internal, and main directions, in this half-section, perforations of the outer portion, evolves decreasingly depending on the distance between the perforations and this substantially middle line, and the value of acute angles formed between the line substantially median and principal directions, in this half-section, perforations of the inner portion, evolves decreasingly depending on the distance between the perforations and this substantially median line.

In other words, the combustion chamber according to the invention is such that the perforations located near a junction between the outer portion and the inner portion of the chamber bottom, that is to say substantially opposite a central annular ring of the combustion chamber, are more inclined towards the axial walls than can be the perforations located near these same axial walls, that is to say substantially facing the annular rings d end of this same combustion chamber.

Advantageously, the perforations located near the junction between the outer portion and the inner portion of the chamber bottom can therefore be strongly inclined towards the axial walls, and therefore allow the cooling air from these perforations s' flow easily and directly along the inner surface of the chamber bottom, substantially radially to the outer and inner axial walls. In the same way, this strong possible inclination indicates that the air of The cooling is only very slightly directed towards the center of the primary zone of the combustion chamber, so that it does not cause a significant disturbance of the combustion reactions.

In addition, the perforations located near the axial walls may be inclined only slightly towards these axial walls, so that the cooling air from these perforations can easily and directly flow along the surfaces. inside these same axial walls. It is specified that at these levels of the chamber bottom where the cooling air can be ejected inside the combustion chamber in a substantially axial direction of the latter, that is to say substantially parallel to the walls axial, the primary zone is sufficiently distant that the introduced cooling air does not cause significant disturbance of combustion reactions.

On the other hand, it is advantageously possible to make a gradual inclination of these perforations as they approach the outer and inner axial walls, so as to obtain a substantially homogeneous cooling flow over the entire inner surface from the chamber bottom, as well as over the entire inner hot surface of the axial walls, located near the chamber bottom.

The combustion chamber according to the invention is therefore perfectly adapted not to cause significant disturbance of the combustion reactions inside the primary zone, which is essential for the stability and ignition of the combustion chamber. In addition, the specific design of this chamber simultaneously ensures a satisfactory thermal continuity at the junctions between the chamber bottom and the outer and inner axial walls. According to the invention, for any two directly consecutive perforations of the outer portion, the two acute angles formed between the main directions of these perforations and the substantially median line have different values, and for any two directly consecutive perforations of the internal portion, the two acute angles formed between the main directions of these perforations and the substantially median line have different values.

This particular configuration makes it possible to obtain a very gradual inclination of the perforations of the chamber bottom.

Preferably, the chamber base is provided with primary sectors of perforations as well as secondary sectors of perforations, the primary sectors being situated substantially between two directly consecutive injection orifices, and the secondary sectors lying on either side of each injection orifice, in a substantially radial direction of the combustion chamber.

With such an arrangement, it is possible to further enhance the homogeneity of the cooling air flow towards the outer and inner axial walls of the combustion chamber. This homogeneity can in particular be obtained by providing that the perforations of the secondary sectors are of greater size than those of the perforations of the primary sectors, because of their presence in a small quantity.

Other advantages and features of the invention will become apparent in the detailed non-limiting description below.

BRIEF DESCRIPTION OF THE DRAWINGS

• la figure 1 représente une vue partielle en demi-coupe axiale d'une chambre de combustion annulaire de turbomachine, selon un mode de réalisation préféré de la présente invention,
• la figure 2 représente une vue partielle en coupe prise le long de la ligne II-II de la figure 1,
• la figure 3 représente une vue en section prise le long de la ligne III-III de la figure 2, et
• la figure 4 représente une vue en section prise le long de la ligne IV-IV de la figure 2.

This description will be made with reference to the appended drawings among which;

• the figure 1 represents a partial axial half-section view of an annular turbomachine combustion chamber, according to a preferred embodiment of the present invention,
• the figure 2 represents a partial sectional view taken along line II-II of the figure 1 ,
• the figure 3 represents a sectional view taken along line III-III of the figure 2 , and
• the figure 4 represents a sectional view taken along line IV-IV of the figure 2 .

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

With reference jointly to figures 1 and 2 , there is shown an annular combustion chamber 1 of a turbomachine, according to a preferred embodiment of the present invention.

The combustion chamber 1 comprises an external axial wall 2, as well as an internal axial wall 4, these two walls 2 and 4 being disposed coaxially along a principal longitudinal axis 6 of the chamber 1, this axis 6 also corresponding to the axis longitudinal main of the turbomachine.

The axial walls 2 and 4 are connected to each other via a chamber bottom 8, the latter being assembled for example by welding to an upstream portion of each of the axial walls 2 and 4.

The chamber bottom 8 preferably takes the form of a substantially flat annular ring, of axis identical to the longitudinal main axis 6 of the chamber 1. Of course, this chamber bottom 8 could also have any other suitable shapes, such as a frustoconical shape of the same axis, without departing from the scope of the invention.

A plurality of injection orifices 10, preferably of cylindrical shape and of circular section, are distributed angularly and in a substantially regular manner on the chamber bottom 8. Each of these injection orifices 10 is designed so as to be able to cooperate with a fuel injector 12, in order to allow the combustion reactions inside this combustion chamber 1. It is specified that these injectors 12 are also designed to so as to allow the introduction of at least a portion of the air for combustion, the latter occurring in a primary zone 14 located in an upstream portion of the combustion chamber 1. In addition, it is also indicated that the air for combustion can also be introduced inside the chamber 1 via primary orifices 16, located all around the external axial walls 2 and internal 4. As can be seen on the figure 1 , the primary orifices 16 are arranged upstream of a plurality of dilution orifices 18, the latter also being placed all around the external axial walls 2 and internal walls 4, and whose main function is to allow the supply of air to a dilution zone 20 located downstream of the primary zone 14.

In addition, it is specified that another part of the air supplied to the combustion chamber 1 is in the form of a cooling air flow D, serving mainly to cool the inner surface 21 of the chamber floor 8. As such, even if the air used to cool the chamber bottom 8 also makes it possible to cool an upstream portion of the inner surfaces 22 and 24 of the external axial walls 2 and internal walls 4, an additional cooling air flow rate ( not shown) is generally allocated to cool all of these interior hot surfaces 22 and 24.

More specifically with reference to the figure 2 , it can be seen that the chamber bottom 8 is of the multi-perforated type, namely that it has a plurality of perforations 26, preferably cylindrical of circular sections, and intended to allow the passage of the cooling air flow D inside the combustion chamber 1.

As can be seen in this figure, the bottom chamber 8 is divided into an outer portion 28 connected to the outer axial wall 2, and an inner portion 30 connected to the inner axial wall 4. Of course, these annular portions 28 and 30 are usually formed in one piece, and their virtual separation may then consist of a center circle C located on the longitudinal main axis 6, and radius R corresponding to a mean radius between an outer radius and an inner radius from the bedroom floor 8.

On this chamber bottom 8, the perforations 26 located on the outer portion 28 are then made to direct a portion D1 of the cooling air flow D towards the outer axial wall 2, in order to cool the entire this outer portion 28, and an upstream portion of the outer axial wall 2. In the same way, the perforations 26 on the inner portion 30 are made to direct another portion D2 of the cooling air flow D in the direction of the inner axial wall 4, in order to cool all of this inner portion 30, as well as an upstream portion of the inner axial wall 4.

Referring now to the figure 3 it can be seen that in axial half-section, the perforations 26 of the outer portion 28 are such that the value of the acute angles A formed between a line substantially median 32 of the half-section and principal directions 34 of the perforations 26 in this half-section, evolves decreasingly as a function of the distance between these perforations 26 and this substantially median line 32.

In other words, in each axial half-section of the combustion chamber 1, taken between any two injection ports and directly consecutive, the inclination of the perforations 26 relative to the outer axial wall 2 decreases progressively as and as these perforations 26 of the outer portion 28 move away from the substantially median line 32, the latter being referred to essentially for reference.

Indeed, by a substantially median line 32 of the half-section, it is naturally to understand that it is the virtual line located approximately equal distance from the upstream portions of the external axial walls 2 and internal 4 considered in half-section, this line 32 can also be noted in that in addition to forming an axis of symmetry of the half-section shown, it virtually separates the outer portions 28 and inner 30 of the chamber bottom 8.

It is specified that in the preferred embodiment described, this substantially median line 32, passing through the circle C, is also substantially perpendicular to the chamber bottom 8, insofar as it itself is substantially perpendicular to the axial walls 2 and 4 .

On the other hand, it is also indicated that in the axial half-section shown on the figure 3 , the main directions 34 of the perforations 26 correspond respectively to their main axes, in the sense that these perforations 26 are all traversed diametrically by the section plane. However, in all other axial half-section where one or more perforations 26 can be cut otherwise than diametrically, each main direction 34 can then be considered as being a line substantially parallel to the two line segments symbolizing the perforation 26 concerned.

Thus, the perforations 26 located near the substantially median line 32 can therefore be strongly inclined, for example so that the acute angle A reaches a value of about 60 °. The cooling air coming from these perforations 26 can therefore flow easily and directly along the inner surface 21 of the outer portion 28 of the chamber bottom 8, substantially radially to the outer axial wall 2, without disturbing combustion reactions in the primary zone 14.

In addition, the perforations 26 located near the outer axial wall 2 may be inclined only slightly towards the wall 2, for example so that the acute angle A reaches a value of about 5 °. The cooling air coming from these perforations 26 can then easily and directly flow along the hot inner surface 22 of the external axial wall 2, without stagnating at the junction between the chamber bottom 8 and this same wall. axial 2.

By providing a value of the acute angle A decreasing progressively closer to the outer axial wall 2, it is then possible to obtain a very homogeneous portion D of the cooling flow D, not creating thermal discontinuity at the various levels. components of the combustion chamber 1.

In the same way and with the aim of availing itself of the same effects on the inner portion 30 of the chamber bottom 8 as on the inner axial wall 4, in axial half-section, the perforations 26 of the inner portion 30 are such that the value of the acute angles B formed between the substantially median line 32 and principal directions 36 of the perforations 26 in this half-section, changes in a decreasing manner as a function of the distance between these perforations 26 and this substantially median line 32.

In a manner similar to that encountered with the outer portion 28 of the chamber bottom 8, the value of the acute angles B formed between on the one hand the main directions 36 of the perforations 26 of the inner portion 30, and on the other hand the line substantially median 32, can progressively evolve from about 60 ° to about 5 °, approaching the inner axial wall 4.

With reference again to the figure 2 it can be seen that the chamber bottom 8 is provided with primary sectors 38 of perforations 26, these primary sectors 38 being situated substantially between two directly consecutive injection orifices 10. As can be seen in this figure, at least a portion of the perforations 26 of each primary sector 38 (a single of them being shown) are arranged to define rows in the form of curved lines centered on the center of the injection port 10 near which these perforations 26 are located.

In addition, the chamber bottom 8 is also provided with secondary sectors 40 of perforations 26, these secondary sectors 40 being each between two consecutive primary sectors 38, on either side of an injection orifice 10 in one direction. substantially radial of the combustion chamber 1.

In other words, in this same substantially radial direction of the combustion chamber 1, a secondary sector 40 is both above and below the injection port 10 concerned.

In this respect, as shown on the figure 4 and similarly to that described above, it can also be provided in axial half-section taken to pass through an injection port 10, the perforations 26 of the outer portion 28 are such that the value of acute angles C formed between a substantially median line 42 of the half-section and principal directions 44 of the perforations 26 in this half-section, evolves in a decreasing manner as a function of the distance between these perforations 26 and this substantially median line 42.

In the same way, the perforations 26 of the inner portion 28 are such that the value of the acute angles D formed between the substantially median line 42 of the half-section and directions main 46 perforations 26 in this half-section, evolves decreasingly depending on the distance between these perforations 26 and this substantially median line 42.

Finally, it is specified that in order to have the circumferentially most homogeneous portions D1 and D2 of flow, the perforations 26 of the secondary sectors 38 are preferably of greater dimensions than those of the perforations 26 of the primary sectors 40, because of their presence. in a lower number.

Of course, various modifications may be made by those skilled in the art to the annular combustion chamber 1 which has just been described, only by way of non-limiting example.

Claims (3)

1. Annular turbine engine combustion chamber (1), where said chamber (1) includes an external axial wall (2), and internal axial wall (4) and a chamber base (8) which links said axial walls (2,4), with the chamber base (8) possessing a series of injection ports (10) and a series of holes (26) with said injection ports (10) being intended to at least allow injection of fuel into the interior of the combustion chamber (1) and said holes (26) being intended to allow a supply of cooling air (D) to pass which is suitable for cooling the chamber base (8), said chamber base (8) being on the one hand equipped with an external portion (28) in which holes (26) are made so as to direct part (D1) of the supply of cooling air (D) towards the external axial wall (2) and on the other hand an internal part (30) in which holes (26) are made so as to direct another part (D2) of the supply of cooling air (D) towards the internal axial wall (4) and by the fact that the chamber (1) is designed so that in axial half-section, taken in any manner whatsoever between two directly successive injection ports (10), the values of acute angles (A) formed between a line that is effectively the median of the half-section (32) located between the external axial wall (2) and the internal axial wall (4) and the principal directions (34), in this half-section, of the holes (26) of the external portion (26) decreases as a function of the distance between the holes (26) and this line that is effectively the median (32), and the value of the acute angles (B) formed between the line that is effectively the median (32) and the principal directions (36), in this half-section, of the holes (26) in the internal portion (30), decrease as a function of the distance between the holes (26) and the line that is effectively the median (32), characterised by the fact that for any two directly successive holes (26) whatsoever in the external portion (28), the two acute angles (A) formed between the principal directions (34) of these holes (26) and the line that is effectively the median (32) will have different values, and by the fact that for two any two directly successive holes whatsoever in the internal portion (30), the two acute angles (B) formed between the principal directions (36) of these holes (26) and the line that is effectively the median (32) will have different values.
2. An annular combustion chamber (1) as described in claim 1, characterised by the fact that the chamber base (8) is equipped with primary sectors (38) of holes (26) and with secondary sectors (40) of holes (26), with the primary sectors (38) being effectively located between two directly successive injection ports (10) and the secondary sectors (40) being located on either side of each injection port (10), in a direction that is effectively radial to said combustion chamber (1).
3. An annular combustion chamber (1) as described in claim 2, characterised by the fact that the holes (26) in the secondary sectors (40) are of larger dimensions than those of the holes (26) in the primary sectors (38).

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