TURBOMACHINE COMBUSTION CHAMBER

Abstract

A turbine engine includes a combustion chamber, comprising two coaxial axisymmetric walls extending one inside the other and delimiting between one another an annular air-circulation, an exterior wall, and at least one injector passing through the walls via ports, wherein the injector comprises a peripheral tube connected to the walls by three connections, at least two connections being of the slideway and/or ball-joint or bellows type.

Description

TECHNICAL FIELD

The present disclosure relates to the field of regenerative-cycle turbines intended, in particular, for the on-board production of electrical or mechanical energy from fuels for aeronautical, terrestrial, and maritime vehicles, and lightweight mobile units.

A turbine is made up of three elements:

• • a compressor, the role of which is to compress the ambient air to a pressure of between approximately 2 and 30 bar;
  • a combustion chamber, into which a fuel is injected under pressure, then burned with the compressed air, having significant air excess in order to limit the temperature of the exhaust gases; and
  • an axial turbine in which the gases emerging from the combustion chamber are expanded.

In a regenerative-cycle turbine, the exhaust gases emerge from the turbine at high temperatures (greater than 500° C.), while the temperature of the air emerging from the compressor is lower (typically between 200° C. and 400° C.), having a circulation through a heat exchanger inserted between the exhaust gases and the compressed air, which makes it possible to partially reheat the air before it enters the combustion chamber, making it possible to reduce the fuel consumption.

The present disclosure relates more particularly to the combustion chamber and the injection of fuel into the combustion chamber.

BACKGROUND

U.S. patent U.S. Pat. No. 4,453,384 describes an embodiment of a gas turbine comprising:

• • an annular housing having a plurality of equidistant holes that are arranged circumferentially; an annular flame tube that is positioned coaxially in the interior and is spaced apart from the annular housing,
  • the annular flame tube having a corresponding number of circumferentially equidistant holes that are aligned coaxially with the holes of the housing, and
  • a plurality of tubes extending radially through the annular flame tube, each tube being coaxial with the corresponding hole in the annular flame tube and the corresponding hole in the annular housing, each tube extending perpendicularly with respect to an axis of the annular flame tube, each tube having a channel extending therethrough and having an axis that is normal to the axis of the tube and in parallel with the axis of the annular flame tube.

German patent DE1254911 proposes injection nozzles in the form of hooks, mounted in the body of the injection nozzle, which is fixed in the flame holder by the nozzle tip thereof, so as to be displaceable with respect to the walls of the combustion chamber.

In an embodiment, the external part of the body of the injection nozzle, in the form of a hook, is slidably mounted in a guide, optionally associated with the exterior wall of the combustion chamber, and a clamping device, directed in parallel with the mouthpiece of the nozzle is provided for keeping the front end of the mouthpiece against a stop fixed to a hub of the flame holder.

Finally, British patent GB2097112 describes a fuel burner for a gas turbine engine, comprising a fuel feed arm and a fuel injector, the fuel feed arm and the fuel injector being joined together, the fuel feed arm having at least one fuel passage, the fuel injector 65 comprising a body having a passage in communication with the at least one fuel passage in the fuel feed arm, the body having an air duct, the axis of the air duct being coaxial with the axis of the fuel injector, the fuel injector having one or more 70 fuel passages to inject fuel into the air duct, the fuel burner having locating means at the end adjacent to the fuel injector, the locating means being arranged to engage with corresponding locating means on an engine component.

The problem posed by the solutions of the prior art relates to the turbines having a combustion chamber that is insulated from the outside by a double wall, two walls defining an annular channel for the circulation of a flow of compressed air originating from the compressor, and the third wall being the exterior wall of the combustion chamber, allowing for the circulation of the same air flow, previously reheated upon crossing a heat exchanger. The injector or injectors must cross the three walls in a sealed manner, or at least in a manner having controlled leakage. This results in hyperstatic mounting, which does not allow for absorption of the longitudinal thermal expansions of the injector, or the radial and longitudinal thermal expansions of the metal walls exposed to extremely different temperatures.

Furthermore, in the solution described in the U.S. patent U.S. Pat. No. 4,453,384, the injector passes through the walls of the combustion chamber via simple holes, references 38, 48 and 52. This document proposes positioning the injector coaxially inside each of the coaxial holes 52, 48 and 38 provided in the housing 50. This solution thus results in several disadvantages: the radial expansion of the injector is different from the surface expansion of the walls, resulting either in leaks between the periphery of the injector and the edge of the through-holes in the wall, or in clamping of the edges of the holes around the wall of the injector, which limits the radial displacement possibilities and may lead to deformations and to fatigue of the walls.

BRIEF SUMMARY

In order to overcome this problem, the present disclosure relates to a combustion chamber of a turbine engine, surrounded by two coaxial axisymmetric walls, extending one inside the other and delimiting therebetween an annular air-circulation space, and a second air-circulation space delimited by the axisymmetric wall of smaller diameter and the exterior wall of the combustion chamber, and at least one injector that crosses the walls via ports, wherein the injector comprises a peripheral tube that is connected to the walls by three connections, at least two connections being flexible sealed connections allowing for multidirectional clearance, for example, of the slide type and/or of the ball joint type, or of the bellows type.

Within the meaning of the present disclosure, “bellows” means a sealed casing that can be deformed at least axially and radially, and optionally in a torsional or tilting manner.

According to variants:

• • just one of the three connections is formed;
  • the connection between the peripheral tube and the interior wall is formed by an annular linear connection having controlled leakage by way of a calibrated annular cross section;
  • the connection between the peripheral tube and the intermediate wall is formed by a bellows;
  • the connection between the peripheral tube and the exterior wall of the liner is formed by a bellows;
  • the connection between the peripheral tube and the intermediate wall of the liner is formed by a ball joint connection, and the connection between the peripheral tube and the exterior wall of the liner is formed by a sliding ball joint connection;
  • the connection between the peripheral tube and the exterior wall of the liner is formed by a sliding ball-joint connection, and the connection between the peripheral tube and the intermediate wall of the liner is formed by a ball joint connection; and
  • the connection between the peripheral tube and the intermediate wall of the liner is formed by a connection having several degrees of freedom to allow for axial displacement and tangential displacement of the tube, and a tolerance for a ball joint, and in that the connection between the peripheral tube and the exterior wall of the liner is formed by a sealed rigid assembly.

The present disclosure also relates to a turbine comprising a combustion chamber of this kind.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will be more clearly understood on reading the following description of a non-limiting embodiment shown in the accompanying figures, in which:

FIG. 1 is a cross section of a turbine engine according to the present disclosure; and

FIGS. 2 to 8 are schematic views of different variants.

DETAILED DESCRIPTION

FIG. 1 is a perspective view of the turbine engine, comprising a heat exchanger (1), a compressor (2), a combustion chamber (3), and a turbine (4). A conical deflector (11), which is coaxial with the heat exchanger (1), causes the hot gases, originating from the turbine (4), to circulate towards a discharge outlet (12) after having passed through the heat exchanger (1), passing through two cassettes (5, 6) between the tubes.

The parts formed by the compressor (2), the combustion chamber (3) and the turbine (4) are known to a person skilled in the art, and are in accordance with the state of knowledge in the field of turbine engines.

The heat exchanger (1) is formed by a tube heat exchanger, comprising two coaxial annular cassettes (5, 6).

The external cassette (5) is formed by an assembly of parallel tubes, made of a metal alloy that is resistant to high temperatures, for example, refractory stainless steel 347.

By way of example, the external cassette (5) is formed of 2000 tubes having a length of 300 millimeters, an internal cross-section of 2.8 millimeters, and an external cross-section of 3 millimeters. The tubes are held in a known manner by means of inserts for defining the passages of hot gases originating from the turbine.

The tubes form a sleeve having an external radius of 158 millimeters and an internal radius of 128 millimeters.

The internal cassette (6) is formed of 2000 tubes having a length of 300 millimeters, an internal cross-section of 2.8 millimeters, and an external cross-section of 3 millimeters.

The tubes form a sleeve having an external radius of 123 millimeters and an internal radius of 67 millimeters.

The two cassettes (5, 6) are coaxial and are fitted into one another.

The two cassettes (5, 6) are united, at the end opposite the compressor (2), by an annular closure structure (8).

Each of the cassettes (5, 6) comprises, at each end, a front sealing plate that is pierced for the tubes to pass through, and ensures the constant center distance of the tubes. The tubes are brazed or soldered in order to ensure sealing in the region of the connection thereof to the front plates.

The closure structure (8) is formed of two coaxial parts that are fitted together and have the general shape of a rum baba mold, which parts are made of refractory stainless steel 347 of a thickness of 2 millimeters.

The outer part (9) has an external cross section that corresponds to the external cross section of the external cassette (5), and an internal cross section that corresponds to the internal cross section of the internal cassette (6).

The inner part (10) has an external cross section that corresponds to the internal cross section of the external cassette (5), and an internal cross section that corresponds to the external cross section of the internal cassette (6).

Each of the parts (9, 10) is rotationally symmetric according to the axis of the turbine engine, having a constant longitudinal cross section.

The closure structure (8) ensures the deflection of the gases, originating from the external cassette (5), towards the tubes that make up the internal cassette (6).

This solution ensures a double passage of the gases in the heat exchanger (1), which significantly increases the thermal efficiency thereof for a given bulk, and, in particular, length.

The combustion chamber (3) of the annular type has a double interior casing formed by a sheath (30) (“liner”) and an intermediate wall (31). The liner (30) and the intermediate wall (31) define a tubular volume for circulation of the air flow originating from the heat exchanger (1). An exterior wall (32) and the intermediate wall (31) define a tubular volume for circulation of the air flow originating from the compressor (2) and travelling towards the heat exchanger (1).

The tube (35) of the injector passes through the three walls (30 to 32) via three ports. The walls (30 to 32) as well as the tube (35) of the injector are subjected to longitudinal and radial expansions. The fixing is ensured by a combination of connections, avoiding the hyperstatic situations.

The connection between the tube (35) of the injector and the exterior wall (32) is ensured by a cylindrical bellows (36).

The connection between the tube (35) of the injector and the interior wall (30) is ensured by a sliding connection formed by a calibrated port defining, together with the outside surface of the tube (35), a calibrated annular clearance.

The connection between the tube (35) of the injector and the intermediate wall (31) is ensured by a fixed connection.

First Variant

The first variant is illustrated schematically by FIG. 2.

The tube (35) of the injector passes through the three walls (30 to 32) having the respective connections:

• • a ball-joint connection (42) for passage through the exterior wall (32);
  • a ball-joint sliding connection (41) for passage through the intermediate wall (31); and
  • a free connection having calibrated peripheral clearance (40) for passage through the interior wall (30).

Second Variant

The second variant is illustrated schematically by FIG. 3.

The tube (35) of the injector passes through the three walls (30 to 32) having the respective connections:

• • a ball-joint sliding connection (52) for passage through the exterior wall (32);
  • a ball-joint connection (51) for passage through the intermediate wall (31); and
  • a free connection having calibrated peripheral clearance (50) for passage through the interior wall (30).

Third Variant

The third variant is illustrated schematically by FIG. 4.

The tube (35) of the injector passes through the three walls (30 to 32) having the respective connections:

• • a bellows (62) for passage through the exterior wall (32);
  • a soldered connection (61) for passage through the intermediate wall (31); and
  • a free connection having calibrated peripheral clearance (60) for passage through the interior wall (30).

Fourth Variant

The fourth variant is illustrated schematically by FIG. 5.

The tube (35) of the injector passes through the three walls (30 to 32) having the respective connections:

• • a soldered connection (72) for passage through the exterior wall (32);
  • a metal frustoconical bellows (71) for passage through the intermediate wall (31); and
  • a free connection having calibrated peripheral clearance (70) for passage through the interior wall (30).

Fifth Variant

The fifth variant is illustrated schematically by FIGS. 6 to 8.

The tube (35) of the injector passes through the three walls (30 to 32) having the respective connections:

• • a soldered connection (72) for passage through the exterior wall (32);
  • a multidirectional connection (80) for passage through the intermediate wall (31); and
  • a free connection having calibrated peripheral clearance (70) for passage through the interior wall (30).

The connection between the peripheral tube (35) and the intermediate wall (31) of the liner is formed by a connection (80) having several degrees of freedom for allowing axial displacement and tangential displacement of the tube, and a tolerance for a ball joint.

The connection between the peripheral tube (35) and the exterior wall (32) of the liner is formed by a sealed rigid assembly.

Referring to FIG. 8, a gland (37), in which the head (38) of the nozzle (35) is inserted, passes through the exterior wall (32). The head (38) comprises a discal flange (38) that is engaged between the two parts of the gland (37), which ensures clamping and sealing of the discal flange (38).

The inside end (40) passes through the interior wall (30), via passage in a simple hole formed in the interior wall (30). The hole is oblong in this case, in order to take into account the inclination of the axis of the nozzle (35) with respect to the radial axis.

The connection between the nozzle (35) and the intermediate wall (31) is achieved by a part having a conical upper portion (41) that is flared towards the outside and is extended at the base thereof by a discal flange (42) that is movable in radial translation in a slit (42) formed in the head (44) of a tubular extension (43) soldered to the surface of the interior wall (30).

The discal flange (42) is flexible, which furthermore allows for a lightweight ball joint with respect to the tubular extension (43).

Claims

1. A turbine engine having a combustion chamber, the combustion chamber comprising two coaxial axisymmetric walls extending one inside the other and delimiting therebetween an annular air-circulation space, and an exterior wall, and at least one injector crossing the walls via ports, wherein the injector comprises a peripheral tube that is connected to the walls by three connections, at least two connections being flexible sealed connections allowing for multidirectional clearance.

2. The turbine engine of claim 1, wherein just one of the three connections is formed by a sealed rigid assembly.

3. The turbine engine of claim 1, wherein the connection between the peripheral tube and an interior wall is formed by a linear annular connection having controlled leakage by way of a calibrated annular cross section.

4. The turbine engine of claim 1, wherein the connection between the peripheral tube and an intermediate wall is formed by a bellows.

5. The turbine engine of claim 1, wherein the connection between the peripheral tube and the exterior wall is formed by a bellows.

6. The turbine engine of claim 1, wherein the connection between the peripheral tube and an intermediate wall of a liner is formed by a ball-joint connection, and the connection between the peripheral tube and the exterior wall of the liner is formed by a sliding ball-joint connection.

7. The turbine engine of claim 1, wherein the connection between the peripheral tube and the exterior wall of a liner of the chamber is formed by a sliding ball-joint connection, and the connection between the peripheral tube and an intermediate wall of the liner is formed by a ball-joint connection.

8. The turbine engine of claim 1, wherein the connection between the peripheral tube and an intermediate wall of a liner is formed by a connection having several degrees of freedom to allow for axial displacement and tangential displacement of the tube, and a tolerance for a ball joint, and the connection between the peripheral tube and the exterior wall of the liner is formed by a sealed rigid assembly.

9. The turbine engine of claim 1, further comprising a gland, in which a head of the peripheral tube is inserted, passes through the exterior wall, the head having a discal flange engaged between the two parts of the gland.

10. The turbine engine of claim 1, wherein an inside end of the peripheral tube passes through a hole formed in the interior wall with clearance between the peripheral tube and the interior wall.

11. The turbine engine of claim 1, wherein the connection between the peripheral tube and the intermediate wall is achieved by a part having a conical upper portion that is flared towards the outside and is extended at the base thereof by a discal flange that is movable in radial translation in a slit formed in the head of a tubular extension soldered to a surface of the intermediate wall.