Injection system for a combustion chamber of a turbine engine, comprising an annular wall having a convergent inner cross-section

Abstract

An air and fuel injection system for a turbine engine combustion chamber dome, including at least two fuel injection devices including a central injector and a peripheral annular injector arranged around the central injector, and an inner annular air inlet channel into which the central injector opens up to enable mixing between the fuel from the central injector and the air inlet into the inner annular channel, and at least one outer annular air inlet channel to enable enrichment of this mix with air and to stabilize the pilot combustion zone, wherein the inner annular channel and at least one outer annular channel are separated by an intermediate annular wall extending around the central injector and having a convergent inner profile.

Claims

1. An air and fuel injection system for an annular turbine engine combustion chamber dome comprising: a central fuel injector including a nose which sprays a flow of fuel; a peripheral annular fuel injector arranged around said central fuel injector; an inner annular air inlet channel in which the central fuel injector is disposed, air which is inlet into the inner annular air inlet channel forming a mix with fuel originating from the nose of the central fuel injector; an outer annular air inlet channel which generates a swirl movement of air which is inlet into the outer annular air inlet channel to enable enrichment of the mix with air and stabilization of a pilot combustion zone by generating an upstream recirculation zone close to the nose of the central fuel injector and a downstream recirculation zone downstream from the pilot combustion zone, the outer annular air inlet channel being disposed radially outward of the inner annular air inlet channel relative to a central axis of the injection system; and an intermediate annular wall extending around the central fuel injector and having a convergent inner profile that is convergent towards the central axis of the injection system such that the fuel flow sprayed by the nose of the central fuel injector and the air flow output from the inner annular air inlet channel are approximately perpendicular, the intermediate annular wall separating the inner annular air inlet channel and the outer annular air inlet channel, wherein the inner annular air inlet channel is free of a swirler to generate a swirl movement, wherein the intermediate annular wall includes a first upstream portion extending approximately along the central axis of the injection system and a second downstream portion convergent towards the central axis of the injection system, the nose of the central fuel injector being disposed downstream of the first upstream portion of the intermediate annular wall, and wherein the outer annular air inlet channel is delimited by the intermediate annular wall and an outer annular wall, the outer annular wall including an inner convergent divergent profile, and a downstream end of the outer annular wall being downstream of the second downstream portion of the intermediate annular wall and downstream of the nose of the central fuel injector.

2. The injection system according to claim 1, wherein the intermediate annular wall extends along the central axis of the injection system around the central fuel injector and is interrupted approximately superposed over the nose of the central fuel injector.

3. The injection system according to claim 1, comprising a plurality of outer annular air inlet channels.

4. The injection system according to claim 1, wherein fins pass through said outer annular air inlet channel.

5. An annular combustion chamber for a turbine engine, comprising at least one injection system according to claim 1.

6. A turbine engine, comprising an annular combustion chamber according to claim 5.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be better understood after reading the following detailed description of non-limitative example embodiments of the invention and an examination of the partial diagrammatic figures in the appended drawing in which:

(2) FIG. 1 is a half-axial sectional view of an annular combustion chamber of a turbine engine comprising injection systems according to prior art,

(3) FIG. 2 is an axial sectional view at a larger scale, illustrating the injection system in the combustion chamber in FIG. 1,

(4) FIG. 3 is an axial sectional view of an example injection system according to the invention,

(5) FIG. 4 is a perspective view of the pilot zone of the injection system in FIG. 3,

(6) FIG. 5 is an axial sectional view, illustrating the formation of the recirculation zones, particularly between the pilot combustion zone and the multipoint combustion zone, obtained by the injection system in FIG. 3, and

(7) FIG. 6 is an axial sectional view, of another example injection system according to the invention.

(8) Identical references in all these figures may denote identical or similar elements.

(9) Moreover, the different parts shown in the different figures are not necessarily at the same scale to make the figures more easily readable.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

(10) FIGS. 1 and 2 that show an annular combustion chamber 10 of a turbine engine comprising injection systems 24 according to prior art have already been described above.

(11) With reference to FIGS. 3 to 5, the figures show a first example of an injection system 24 according to the invention. FIGS. 3 and 4 show axial and perspective cross-sectional views of the injection system 24, and FIG. 5 shows the formation of recirculation zones between the pilot combustion zone and the multipoint combustion zone obtained as a result of the injection system 24.

(12) Such an injection system 24 may be designed to be installed in an annular combustion chamber 10 of a turbine engine, particularly like that described above with reference to FIGS. 1 and 2, and it may be of a type similar to the injection system 24 in FIGS. 1 and 2. Also, only elements specific to the injection system 24 according to the invention are described below and reference may be made to the previous description concerning elements similar to those in FIGS. 1 and 2.

(13) As can be seen particularly in FIGS. 3 and 4, the air and fuel injection system 24 comprises a central injector 26 provided with a nose 26a that can spray a flow of fuel C and a peripheral annular injector 43 arranged around the central injector 26. The peripheral annular injector 43 is in particular a multipoint type injector.

(14) The injection system 24 also comprises an inner annular air inlet channel 71 in which the central injector 26 opens up to enable mixing between the fuel C from the central injector 26 and the air flow A1 inlet into the inner annular channel 71 to prevent excessive centrifuging of fuel droplets, and also an outer annular air inlet channel 30 generating a swirl movement, unlike the inner annular channel 71, to enable subsequent enrichment of this mix with air and to stabilise the pilot combustion zone P and to control aerodynamic structures of the pilot combustion zone P including the recirculation zones ZR.sub.upstream and ZR.sub.downstream described later with reference to FIG. 5.

(15) According to the invention, the inner annular channel 71 and the outer annular channel 30 are separated by an intermediate annular wall 70 that extends around the central injector 26 and that has a convergent inner profile 70a.

(16) More specifically, the intermediate annular wall 70 comprises a first upstream portion I.sub.1 that extends approximately in a straight line along the central axis 28 of the injection system 24 around the central injector 26, and a second downstream portion I.sub.2 that is convergent towards the central axis 28 of the injection system 24.

(17) The intermediate annular wall 70 also extends along the central axis 28 around the central injector 26 and is then interrupted approximately where it is superposed over the nose 26a of the central injector 26, such that the air flow A1 from the inner annular channel 71 and the flow of fuel C from the nose 26a of the central injector 26 are mixed with each other in a zone with steep gradients to improve spraying.

(18) The intermediate annular wall 70 also has a convergent outer profile 70b, facing a divergent portion of the annular wall 38.

(19) The inner annular channel 71 and the intermediate annular wall 70 together define a convergent air film that enables more uniform carbonation of the core of the pilot combustion zone P.

(20) The orientation of the intermediate annular wall 70 with a convergent inner profile 70a towards the central axis 28 of the injection system 24 can give a fuel C injection approximately perpendicular to the air flow A1 from the inner annular channel 71.

(21) The injection of fuel C approximately perpendicular to the air flow A1 can impose the direction of transport of droplets of fuel C along the central axis 28 towards the pilot combustion zone P.

(22) Advantageously, the flow of fuel C is thus at a distance from the multipoint combustion zone M to better supply the pilot combustion zone P.

(23) FIG. 5 shows the distinction obtained between the pilot combustion zone P and the multipoint combustion zone M. Furthermore, as can be seen in FIG. 3, the fuel C flow is then at a distance from the air flow A2 originating from the peripheral annular channel 52 (also called the main swirler).

(24) Moreover, as can be seen in FIG. 5, stabilisation of the flame at the pilot combustion zone P may require the presence of a recirculation zone ZR.sub.upstream, close to the nose 26a of the central injector 26, and a recirculation zone ZR.sub.downstream, downstream from the pilot combustion zone P.

(25) The recirculation zone ZR.sub.upstream or ZR.sub.downstream may for example be generated by the swirl movement obtained as a result of the intermediate swirler (outer channel 30) and the main swirler (peripheral channel 52), which may be provided with oblique fins 34 and 54 as described above.

(26) The aerodynamic structure and the recirculation zones ZR.sub.upstream and ZR.sub.downstream around the pilot combustion zone P can be controlled by the presence of an outer air inlet channel 30.

(27) The formation of a convergent air film in the pilot zone of the injection system 24, obtained by the presence of the intermediate annular wall 70 provided with a convergent inner profile 70a, can give a flame in the pilot combustion zone P sufficiently distinct from the main flow of the multipoint combustion zone M to prevent freezing of combustion reactions of the pilot flame, and fast fuel supply from the central injector 26 with optimised atomisation and evaporation. In this way, it may be possible to strongly improve combustion of fuel and thus further reduce the level of emission of substances noxious for the environment.

(28) With reference to FIG. 6, the figure shows a second example injection system 24 according to the invention.

(29) Unlike the first example injection system 24 shown in FIGS. 3 to 5, the injection system 24 in FIG. 6 comprises two outer annular air inlet channels 30a and 30b, superposed radially on each other.

(30) Oblique fins 34a, 34b pass through each outer annular channel 30a, 30b that will apply a swirl movement on the air flow passing between them about the central axis 28 of the injection system 24. This swirl movement can facilitate the appearance of recirculation zones ZR.sub.upstream and ZR.sub.downstream, as described above.

(31) Advantageously, the inner annular channel 71 will not generate such a swirl movement.

(32) The intermediate annular wall 70 also comprises a first upstream portion I.sub.1 that extends approximately in a straight line along the central axis 28 of the injection system 24, around the central injector 26, and a second downstream portion I.sub.2 that converges towards the central axis 28 of the injection system 24.

(33) Furthermore, the intermediate annular wall 70 extends along the central axis 28 around the central injector 26 and is then interrupted approximately where it is superposed over the nose 26a of the central injector 26, as described above.

(34) The additional presence of an annular wall 36 with a convergent-divergent inner profile, or venturi 36, can also further improve the effect obtained by the intermediate annular wall 70 to prevent flame returns into the injection system 24.

(35) Obviously, the invention is not limited to the example embodiments that have just been described. Those skilled in the art could make various modifications to them.

(36) The expression comprising one should be understood as being synonymous with comprising at least one, unless mentioned otherwise.