WO2014053728A1

WO2014053728A1 - Combustion chamber comprising a flame tube fixed by means of three centring members

Info

Publication number: WO2014053728A1
Application number: PCT/FR2013/052203
Authority: WO
Inventors: Bernard CARRERE; Philippe OLHARAN
Original assignee: Turbomeca
Priority date: 2012-10-01
Filing date: 2013-09-23
Publication date: 2014-04-10
Also published as: FR2996289B1; FR2996289A1

Abstract

The invention concerns a combustion chamber (1), comprising -an annular outer housing (10), -the flame tube (20), arranged inside the outer housing (10) of the combustion chamber (1), and -fixing means (30) for fixing the wall (22) of the flame tube (20) to the outer housing (10) of the combustion chamber (1), comprising exactly three centring members (30a) distributed in a fixing plane (P) normal to the longitudinal axis (X) of the flame tube (20), at least one of the fixing means (30) being an injector or a spark plug.

Description

Combustion chamber comprising a flame tube fixed by means of three centering elements

The invention generally relates to the field of combustion chambers for turbomachines, and more particularly the fixing and centering of a flame tube in a combustion chamber of a turbomachine.

A turbomachine generally comprises, from upstream to downstream in the direction of the gas flow, a blower, one or more stages of compressors, for example a low pressure compressor and a high pressure compressor, a combustion chamber, one or more turbine stages, for example a high pressure turbine and a low pressure turbine, and a gas exhaust nozzle.

The combustion chamber is delimited by internal and external revolution housings which extend one inside the other and are connected upstream to an annular housing of the chamber bottom. The outer casing of the chamber is fixed on an outer casing of the turbomachine, while the inner casing of the chamber is fixed on an inner casing thereof.

The combustion chamber further comprises a "flame tube

Or "hearth," which is the seat of the burning of gases.

The flame tube may be generally toric and direct flow, and comprise annular walls of revolution joined at an upstream end by a bottom and a fairing having fuel injector passage holes carried by the combustion chamber. .

Alternatively, the flame tube may be "reverse flow", and have a bent annular shape for returning the gas flow downstream of the turbine engine (towards the turbine). The flow of gases is then successively from downstream to upstream and again downstream of the combustion chamber. The injectors are then generally arranged at the flame tube head, and help attach the flame tube to the combustion chamber.

However, it is necessary to center the flame tube in the combustion chamber very precisely to ensure its alignment with the other parts of the turbomachine.

The document FR 2 392 232 therefore proposed to fix in addition the flame tube on the outer casing of the combustion chamber by means of air guiding bodies, provided on an outer wall and a head of the flame tube. Moreover, in order to compensate for the thermal expansion and contraction of the flame tube, the walls of the flame tube are welded together only at the level of the injectors, while permitting axial sliding relative to each other.

It has furthermore been proposed to fix the flame tube by means of a large number of fasteners, in particular four equidistant fastening sleeves fitted to the flame tube and also movable bushings, to the outer casing of the flame tube. the combustion chamber.

However, these fastening systems have very small dimensional and geometric tolerances so that the flame tube is precisely centered in the combustion chamber, in order to ensure its alignment with the other parts of the turbomachine. In addition, to improve the accuracy of the positioning of the flame tube in the combustion chamber, the assembly is generally hyperstatic. However, this has the consequence of making the assembly delicate and of accelerating the wear of the parts and fastening means, which are also subjected to high thermal and mechanical stresses during operation of the turbomachine, thus reducing the service life. of the combustion chamber. These parts are also not easy to replace as they tend to deform during operation and the positioning and dimensional tolerances are very severe.

It has also been proposed, in document EP 1 793 095, a direct flow combustion chamber of a turbomachine whose tube flame is fixed by means of a multitude of fastening means on the outer casing of the combustion chamber. These multiple attachment means are therefore particularly bulky and increase the overall mass of the combustion chamber.

An object of the invention is therefore to propose a combustion chamber comprising a flame tube, in particular an inverted-flow tube, whose fixing and positioning is ensured in a simple and fast manner, the dimensional and geometric tolerances of which can be wider so to reduce its cost of production, while ensuring a precise centering of the flame tube in the combustion chamber and limiting its size, and whose parts can be more easily changed to facilitate the maintenance of the combustion chamber.

For this, the invention proposes a combustion chamber of a turbomachine, comprising

an outer annular casing,

the flame tube comprising an annular wall having a main direction extending along a longitudinal axis, the flame tube being arranged inside the outer casing of the combustion chamber, and means for fixing the wall of the flame tube on the outer casing of the combustion chamber, comprising exactly three centering elements distributed in a plane of attachment normal to the longitudinal axis of the flame tube, at least one of the fixing means is an injector or a spark plug.

Some optional but non-limiting features of the combustion chamber are as follows:

the fastening means each comprise a fixing pin, the outer casing comprises insertion orifices, and the wall of the flame tube comprises receiving orifices facing the insertion orifices of the outer casing,

the fixing pins being each inserted and fixed in an insertion orifice of the outer casing and in the receiving orifice facing the wall of the flame tube,

the wall of the flame tube and / or the external casing comprise, at their receiving orifices and / or their insertion orifices respectively, a boss extending radially with respect to the longitudinal axis,

the axes for fixing the centering elements are inserted and fixed without play in the insertion orifice of the outer casing and in the receiving orifice of the wall of the flame tube,

the fastening means furthermore comprise at least one fixing element extending radially in the fastening plane, the fastening pins of the fastening elements being inserted and fixed loosely in the corresponding insertion holes of the outer casing and in the corresponding receiving holes of the wall of the flame tube,

it comprises at least three fastening elements distributed in the fastening plane, preferably six fastening elements,

at least one of the fixing means is an injector or a spark plug, and

the fastening means are distributed equidistantly in the fastening plane.

According to a second aspect, the invention also proposes a turbomachine comprising such a combustion chamber, as well as a method of manufacturing such a combustion chamber, during which the annular wall of the flame tube is fixed without clearance to the casing. annular of the combustion chamber using the three centering elements.

Some optional but non-limiting features of the manufacturing process are as follows: the fastening means furthermore comprise at least one fixing element each comprising a fixing pin, the outer casing comprising insertion orifices, and the wall of the flame tube comprising receiving orifices facing the insertion orifices. of the outer casing, and the manufacturing method comprises a step during which the fixing pins of the fastening elements are inserted and fixed loosely in the corresponding insertion holes of the outer casing and in the corresponding receiving holes of the wall flame tube,

a fusible film is applied between the fixing pins and an internal wall of the insertion orifice and / or an internal wall of the receiving orifice prior to the insertion of the fixing pin into the holes of insertion and receiving holes, and

the fusible film is applied to a thickness of between 0.02 and 0.03 millimeters.

Other features, objects and advantages of the present invention will appear better on reading the detailed description which follows, with reference to the appended figures given in a non-limiting manner and in which:

FIG. 1 is a longitudinal sectional view of an exemplary embodiment of an inverted flow combustion chamber according to the invention,

FIG. 2a is a cross-sectional view of the combustion chamber of FIG. 1, along the plane P,

FIG. 2b is a partial side view of an exemplary embodiment of the external casing of the combustion chamber of FIG. 2a,

FIG. 3 is a sectional view of an exemplary embodiment of a centering element of FIG. 2a,

FIG. 4a is a sectional view of a first variant embodiment of an exemplary embodiment of a fastener element of FIG. 2b, FIG. 4b is a sectional view of a second variant embodiment of an exemplary embodiment of a fastener element,

FIG. 5 is a sectional view of a manufacturing step of the fastening element of FIG. 4b, and

FIG. 6 is a flowchart representing various steps of an exemplary embodiment of the method of manufacturing a combustion chamber according to the invention.

In what follows, the invention will be described with reference to the accompanying figures illustrating an exemplary embodiment of a combustion chamber of a turbomachine comprising an inverted flow flame tube. This is however not limiting, the invention can be applied directly to a direct flow combustion chamber. A turbomachine typically comprises a nacelle which forms an opening for the admission of a given flow of air. Typically, the turbomachine includes an air compression section and a combustion chamber, wherein the compressed air is mixed with fuel prior to being burned. The gases resulting from this combustion are then directed to a high-pressure turbine before being evacuated.

The high-pressure turbine conventionally comprises one or more rows of turbine blades circumferentially spaced around the rotor of the turbine. It also includes a high-pressure distributor for directing the flow of gas from the combustion chamber to the turbine blades at a suitable angle and speed to rotate the vanes and rotor of the turbine.

Thus, the combustion chamber 1 is connected upstream to a compressor (not shown) which supplies the combustion chamber 1 with pressurized air via a diffuser 2 and downstream to a distributor 3. It is delimited by cases of external revolution 10 and internal 12 which extend one inside the other and are connected together at a downstream end, as well as a bottom cover 14. The outer casing 10 of the chamber 1 is fixed on an outer casing of the turbomachine, the inner casing 12 of the chamber 1 is fixed on an outer wall 3a of the distributor 3, while the bottom casing 14 is fixed on the outer casing the turbomachine, near the outer casing 10 and an inner wall 3b of the distributor 3.

The combustion chamber 1 comprises an annular flame tube surrounded by an annular air supply duct which is separated from the flame tube 20 by a wall 22 of generally toroidal shape. The flame tube 20 comprises an annular air intake orifice 24 connected to the diffuser 2, serving to supply gas to the supply duct 21, an annular exhaust orifice 26 connected to the distributor 3, and a series of ducts. fuel injectors 4 adapted to inject fuel with air from the annular conduit 21 into the flame tube 20.

The wall 22 of the flame tube 20 has a bent annular shape for returning the gas flow downstream of the turbomachine (towards the distributor 3), and comprises a main direction extending along a longitudinal axis X. Thus the flame tube 20 comprises for example an outer annular wall portion 22a and an inner annular wall portion 22b joined at a downstream end by a head 22c. The outer annular wall 22a and inner 22b and the head 22c portions may in particular be made in one piece, or comprise several wall elements assembled together so as to form the annular wall 22 of the flame tube 20.

The flame tube 20 is fixed to the combustion chamber 1 by fastening means 30, connected on the one hand to the outer casing 10 of the combustion chamber 1, and on the other hand to the wall 22 opposite the tube. flame 20, and distributed around the flame tube 20 in a normal plane P to the longitudinal axis X of the flame tube 20, said plane of attachment.

The fastening means 30 comprise exactly three centering elements 30a, and optionally one or more fastening elements 30b.

The three centering elements 30a are preferably distributed equidistantly in the fastening plane P around the flame tube 20, and their function is to center the flame tube 20 accurately in the combustion chamber 1 and to fix it in this position. The dimensional tolerances are of the order of two hundredths of a millimeter (0.02 mm) and the geometric tolerances (that is to say of localization) are of the order of three tenths of a millimeter (0.3 mm) . They are very tight for these parts.

The fastening elements 30b are also distributed in the fastening plane P around the flame tube 20, preferably equidistantly. However, unlike the centering elements 30a, they do not have the function of centering the flame tube 20, but to strengthen its attachment to the combustion chamber 1 and to distribute the stresses in order to limit the wear of the various parts. The flame tube 20 is in fact subjected to high mechanical and thermal stresses, so that it is possible that, under certain conditions, the centering elements 30a alone are not sufficient to maintain the flame tube 20. Their geometric tolerances are therefore less important than those of the centering elements 30a, for example of the order of six tenths of a millimeter (0.6 m), only the dimensional tolerances between the flame tube and the penetrating part of the fixing element remaining relatively tight of the order of one tenth of a millimeter (0.1 mm) to ensure the fixing of the flame tube 20.

Each fastening means 30, whether it be a centering element 30a or a fastening element 30b, may comprise an attachment pin 32 inserted in the outer casing 10 of the combustion chamber 1 and in the wall 22 facing the flame tube 20.

For this, the outer casing 10 of the combustion chamber 1 comprises insertion through orifices 34, and the wall 22 of the flame tube 20 comprises through receiving orifices 36 facing each pair of insertion orifice 36 and receiving 36 being adapted to receive an attachment pin 32.

Each attachment pin 32 comprises a rod 32a adapted to extend through the insertion and receiving openings 36, provided at one end with a head 32b adapted to abut against an outer surface of the outer wall 22a, facing the outer casing 10 of the turbomachine. The rod 32a of the fixing pin 32 is preferably smooth, so as not to prevent the radial displacement of the flame tube 20 when it is expanded due to the thermal stresses it undergoes. Moreover, the length of the head 32b and the rod 32a of the fixing pin 32 is determined so as to be flush with an internal surface of the wall 22 of the flame tube 20, when it is at rest (not dilated).

In the case of the centering elements 30a, the fixing pin 32 is inserted without play in the insertion and receiving orifices 36. The centering elements being three in number, it is therefore possible to guarantee the precise position. flame tube 20 in the combustion chamber 1, and maintain it in this position. The flame tube 20 is therefore self-centered thanks to these three centering elements having a very tight fit. For this, the diameter of the rod 32a is substantially equal to the internal diameter of each insertion hole 36 and receiving 34 corresponding, for example of the order of 10 mm (to 0.1 mm), to limit any play , while allowing the flame tube 20 to expand under the effect of large temperature variations (allowing radial movements of its wall 22) and remaining coaxial with the longitudinal axis X. Moreover, the number of centering elements 30a without clearance being reduced to three, the fixing of the flame tube 20 to the chamber of Combustion 1 is isostatic, in comparison with conventional fastening systems which, to center the flame tube 20, provided a large number of fasteners with tight tolerances which gave the assembly a high degree of hyperstation.

In the case of fastening elements 30b, on the other hand, a clearance is provided either between the fixing pin 32 and the insertion orifice 36 of the outer casing 10 of the combustion chamber 1, or between the insertion orifice 36 and the receiving orifice 34 of the wall 22 of the flame tube 20. This game aims to avoid making the fixing of the flame tube 20 on the combustion chamber 1 hyperstatic and compensate for a possible defect of alignment between the insertion port 36 and the corresponding receiving port 34. For example, for a rod 32a for fixing a fastening element 30b having a diameter of the order of 10 mm, the insertion orifice 36 may have an internal diameter of 13 mm and the receiving orifice 34 may have an internal diameter of 12 mm. Alternatively, the insertion orifice 36 may have an internal diameter of 12 mm, while the receiving orifice 34 may have an internal diameter substantially equal to that of the axis, of the order of 10 mm. In order to reinforce the area of contact between the fastening means 30 and the outer casing 10 of the combustion chamber 1, the latter may comprise bosses 37 at the level of each insertion orifice 36, extending radially, for example towards the outer casing of the turbomachine. The bosses 37 may be machined and tapped, so that they have at least one threaded orifice 38, preferably at least two, adapted to receive screws for holding the head 32b fixed in position by screwing.

The interface between the fixing pins 32b and the flame tube 20 can also be reinforced by bosses 35 extending from the outer surface of the wall 22 of the flame tube 20, in the direction of the outer casing 10 of the flame chamber 20. combustion 1. The centering elements 30a and / or the fastening elements 30b may, in addition to fixing and where appropriate center the flame tube 20, constitute a part of an injector 4 or a spark plug (incandescent or with classical spark). In the case of an injector 4 for example, the attachment pin 32 is then traversed by a channel adapted to receive the oxidant and the air to be injected into the flame tube 20. The fastening plane P is then disposed to near the head 22c of the flame tube 20, and passes through the injectors 4 and spark plugs which form all or part of the fastening means 30, the other fastening means 30 not necessarily having a function other than centering or fixation.

The implementation of exactly three centering elements 30a without clearance in order to fix and center the flame tube 20 in the combustion chamber 1 makes it possible to eliminate the hyperstatism of the assembly, while respecting the very severe geometric and dimensional tolerances. to guarantee the position of the flame tube 20 relative to the other parts of the turbomachine (including the diffuser 2 and the distributor 3).

This attachment can be reinforced by the use of the fastening elements 30b, of generally identical shape, but whose attachment axis 32 has a clearance allowing both to ensure the fixing and the mechanical strength of the flame tube 20 on the outer casing 10, to distribute the mechanical stresses and therefore the wear on a larger number of fastening means than if the three centering elements 30a alone ensured the attachment of the flame tube 20, while reducing the geometric tolerances required, which makes it possible to reduce the manufacturing costs of the combustion chamber 1 and to extend its service life. Indeed, the use of fastening means 30 comprising exactly three centering elements 30a and six fastening elements 30b distributed equidistantly in the fastening plane P, the geometric and dimensional manufacturing tolerances of the combustion chamber 1 are increased by over 80% on the quotation, which significantly reduces the cost of production of the combustion chamber 1. Furthermore, it is now simpler to replace the fastening elements 30b, which are easier to disengage from the flame tube 20 thanks to their play, and despite the deformations due to thermal and mechanical stresses experienced during the operation of the combustion chamber 1. The maintenance cost of the combustion chambers 1 is therefore all the more reduced. The fixing 100 of the flame tube 20 in the combustion chamber 1 can be carried out according to the following steps.

The flame tube 20 is first fixed to the outer casing 10 of the combustion chamber 1 by means of the three centering elements 30a.

For this, during a first step 1 10, the flame tube 20 is positioned in the combustion chamber 1, so as to place each receiving orifice 34 opposite the corresponding insertion orifice 36 of the outer casing 10, then the fixing pins 32 of the centering elements 30a are inserted and fixed one after the other in the orifices 36, 36 facing each other.

(Step 120), for example by screwing the heads 32b of the fixing pins 32 in the threaded holes 36 of the bosses 37 of the outer casing 10. Alternatively, the centering elements 30a can be fixed simultaneously.

The flame tube 20 is now self-centered and fixed in position, thanks to the three centering elements 30a.

In the case where the chamber 1 further comprises fastening elements 30b, they are assembled with the combustion chamber 1 after having fixed the centering elements 30a.

For this, it is possible in particular to apply a fusible film 40 between the rod 32a of the fixing pin 32 and the or holes 34, 36 corresponding (s) with which it is desired to create a game (step 130), then inserting and fixing one after the other the attachment pins 32 of the fastening elements 30b in the corresponding orifices 34 and 36 (step 140). By For example, the free end of the rod 32a can be coated with the fixing pin 32, which is opposite to the head 32b, with the fusible film 40 on a height substantially equal to that of the corresponding boss 35, 37 of the tube. flame 20 (in the case of the receiving port 34) and / or the outer casing 10 (in the case of the insertion port 36).

The objective of the fusible film 40 is to center the fixing pins 32 in their corresponding orifices 34, 36 when they are mounted in the combustion chamber 1, then to rapidly melt during the operation of the combustion chamber 1, under the the effect of the temperature experienced by the chamber, in order to create the desired clearance at the orifices 34, 36. This indeed makes it possible to obtain a uniformly distributed clearance on the circumference of the flame tube 20. use of the fusible film 40 also makes it possible to provide a clearance between the insertion orifice 36 of the wall of the housing 10 and the receiving orifice 34 of the wall 22 of the flame tube 20 of the fastening elements 30b.

Thus, in the case of a desired clearance between the fixing pin 32 and the wall 22 of the flame tube 20, the fixing pin 32 is centered both in the insertion orifice 36, which is configured so that its internal diameter is substantially equal to the diameter of the rod 32a of the insertion axis 32, and in the receiving orifice 34, whose inner diameter is slightly larger than the diameter of the rod 32a of the insertion axis 32, thanks to the presence of the fusible film 40 which fills the space between the rod 32a of the axis 32 and the walls of the insertion orifice 36 configured to create the game. The thickness of the fuse 40 is for example of the order of 0.02 to 0.03 millimeters in order to ensure sufficient clearance, while ensuring the fixing of the flame tube 20 on the combustion chamber 1 and the distribution of stresses and wear of the different parts (fastening means, flame tube 20 and outer casing 10 of the combustion chamber 1).

Advantageously, the fusible film 40 is thus chosen so as to be able to melt during the first start of the turbomachine. By moreover, it is preferably capable of being eliminated in the combustion gases.

For example, the fusible film 40 may comprise beeswax.

Claims

1. Combustion chamber (1) of a turbomachine, comprising - an outer annular casing (10),

- the flame tube (20), comprising an annular wall (22) having a main direction extending along a longitudinal axis (X), the flame tube (20) being arranged inside the outer casing (10) the combustion chamber (1), and

- Fixing means (30) of the wall (22) of the flame tube (20) on the outer casing (10) of the combustion chamber (1), comprising exactly three centering elements (30a) distributed in a plane fastening (P) normal to the longitudinal axis (X) of the flame tube (20),

the combustion chamber being characterized in that at least one of the fixing means (30) is an injector or a spark plug.

The combustion chamber (1) according to claim 1, wherein

the fastening means (30) each comprise a fixing pin (32),

the outer casing (10) comprises insertion orifices (36), and

the wall (22) of the flame tube (20) comprises receiving orifices (34) facing the insertion orifices (36) of the outer casing (10),

the fixing pins (32) being each inserted and fixed in an insertion orifice (36) of the outer casing (10) and in the receiving orifice (34) facing the wall (22) of the flame tube ( 20).

Combustion chamber (1) according to Claim 2, in which the wall (22) of the flame tube (20) and / or the outer casing (10) comprise, at their receiving orifices (34) and / or their insertion orifices (36) respectively, a boss (35, 37) extending radially with respect to the longitudinal axis (X).

4. Combustion chamber (1) according to one of claims 2 or 3, wherein the fixing pins (32) of the centering elements (30a) are inserted and fixed without play in the insertion hole (36). the outer casing (10) and in the receiving orifice (34) of the wall (22) of the flame tube (20).

5. Combustion chamber (1) according to one of claims 2 to 4, wherein the fastening means (30) further comprises at least one fastening element (30b) extending radially in the plane of attachment (P ), the fixing pins (32) of the fastening elements (30b) being inserted and loosely fitted into the corresponding insertion holes (36) of the outer casing (10) and into the corresponding receiving apertures (34) of the wall (22) of the flame tube (20).

6. Combustion chamber (1) according to claim 5, comprising at least three fastening elements (30b) distributed in the fastening plane (P), preferably six fastening elements (30b).

7. Combustion chamber (1) according to one of claims 1 to 6, wherein the fastening means (30) are distributed equidistantly in the attachment plane (P).

8. Turbomachine comprising a combustion chamber (1) according to one of claims 1 to 7.

9. A method of manufacturing (100) a combustion chamber (1) according to one of claims 1 to 8, wherein the annular wall (22) of the flame tube (20) is fixed without play to the annular housing (10) of the combustion chamber (1) using the three centering elements (30a).

The manufacturing method (100) of claim 9, wherein:

the fastening means (30) further comprise at least one fastening element (30b) each comprising a fixing pin (32),

the outer casing (10) comprises insertion orifices (6), and

and the manufacturing method (100) comprises a step (140) during which the attachment pins (32) of the fastening elements (30b) are inserted and loosely fitted into the corresponding housing insertion holes (36). external (10) and in the corresponding receiving holes (34) of the wall (22) of the flame tube (20).

1 1. A manufacturing method (100) according to claim 10, wherein a fusible film (40) is applied (130) between the fastening pins (32) and an inner wall (22) of the insertion hole (36) and or an inner wall of the receiving orifice (36) prior to the insertion (140) of the attachment pin (32) into the insertion orifices (36) and the receiving orifices (34).

12. Manufacturing method (100) according to claim 1 1, wherein the fusible film (40) is applied to a thickness between 0.02 and 0.03 millimeters.