Hydrogen and air injection system

Abstract

The present disclosure relates to a system (20) for injecting a mixture of hydrogen and air along a first axis (X1) into an annular combustion chamber (4) of a turbomachine (1), the injection system (20) comprising: - a radially internal hydrogen circulation channel, - a radially external annular air circulation channel, - an internal swirler being housed in the radially internal channel, - an external swirler being housed in the radially external annular channel, in which a downstream end of the radially internal channel is arranged upstream along the first axis of a downstream end of the radially external annular channel, the radially external annular channel having an air circulation section, the section being convergent along the first axis (X1) at least from a downstream end of the internal swirler or a downstream end of the external swirler, to the downstream end of the radially internal channel. Abstract figure: Figure 5

Description

Title of the invention: Hydrogen and air injection system Technical field

[0001] The present disclosure relates to the field of hydrogen combustion for a turbomachine, such as for example a gas turbine, a turbojet or an aircraft turboprop. More specifically, the present disclosure relates to a system for injecting hydrogen and air into a turbomachine combustion chamber. Prior art

[0002] An aircraft turbomachine conventionally comprises a combustion chamber fueled by kerosene. However, in order to reduce the environmental impact and polluting emissions and to contribute to the decarbonization of air transport, it has been considered to replace kerosene with a hydrogen-based fuel.

[0003] The combustion of hydrogen creates various problems.

[0004] On the one hand, hydrogen is injected in gaseous form, unlike kerosene which is injected in liquid form. The density ratio between these fuels being of the order of 1000, the injection sections of a hydrogen injector are necessarily greater than those of a kerosene injector.

[0005] In addition, flames from hydrogen combustion reach higher temperatures than flames from kerosene combustion under equivalent thermodynamic and richness conditions. “Richness” means the proportion of hydrogen to air for combustion. The mixture is said to be “rich” when hydrogen is in excess compared to air, and conversely, the mixture is said to be “lean” when air is in excess compared to hydrogen. The combustion chamber must then be able to withstand these high temperatures.

[0006] Furthermore, the flame speeds resulting from hydrogen combustion are higher, for example approximately five times, than those resulting from kerosene combustion. These high flame speeds can generate flashbacks, commonly referred to as "flashbacks" in English, in the fuel injection systems in the combustion chamber. These flashbacks can consequently damage the injection systems.

[0007] In addition, the temperatures produced by the combustion of hydrogen may emit nitrogen oxides (NOx).

[0008] In order to address these issues, document WO2023057722A1 proposes a dihydrogen injection device 2 intended to be mounted on an annular bottom of an annular combustion chamber 4 of a turbomachine 1, as illustrated in the [Fig.l]. The annular combustion chamber 4 is arranged between a compressor 3 and a high-pressure turbine 5. Two layouts of said di-hydrogen injection device 2 are possible depending on the orientation of the annular bottom of the annular combustion chamber 4: either the combustion chamber is oriented substantially along a longitudinal axis X2, or the combustion chamber is transverse to said longitudinal axis X2.

[0009] [Fig. 2] illustrates more precisely this dihydrogen injection device which ensures a swirling central flow of hydrogen and a swirling peripheral flow comprising air, designated air flow hereinafter for the sake of simplification. To this end, the injection device comprises an internal channel 6 for circulation of dihydrogen and an external annular channel 7 for circulation of the air flow. The internal channel 6 and the external annular channel 7 are coaxial. In addition, an internal swirler 8 is housed in the internal channel 6 and an external swirler 9 is housed in the external annular channel 7. The swirlers, commonly called "swirlers" in English, make it possible to drive the flows passing through them in rotation.

[0010] In addition, a downstream end 10 of the internal channel 6 is arranged upstream, at a distance r, from a downstream end 11 of the external annular channel 7. This makes it possible to have a hydrogen injection point set back from the outlet plane of the injector, and therefore to allow pre-mixing of the hydrogen coming from the internal channel and the air coming from the external annular channel before the outlet of the injector.

[0011] The injection device of document WO2023057722A1 makes it possible to obtain aerodynamically stabilized flames over a given operating range, to achieve combustion of a lean mixture, thus making it possible to reduce nitrogen oxide emissions and to limit the risks of flame rise.

[0012] In addition, the implementation of a flared shape of the downstream end of the 10 of the internal channel 6, as illustrated in [Fig. 3], makes it possible to extend the operating range with stabilized flames. However, this flared shape increases the pressure losses and can lead to aerodynamic instabilities.

[0013] Indeed, [Fig.4] illustrates results of numerical simulation of the flow speed of hydrogen and air in the injection device having a flared shape of the downstream end of the internal channel 6.

[0014] In [Fig.4], the darker the gray, the higher the flow speed. Thus, we observe that in a first zone Z1, the speeds are lower due to a separation of the air flow.

[0015] Furthermore, the white lines in [Fig. 4] correspond to the stoichiometric mixing lines, i.e. to the zones where the combustion of air and hydrogen takes place in stoichiometric proportions. One of the stoichiometric mixing lines comes in particular at the downstream end 10 of the internal channel 6 at level of a second zone Z2. However, these lines with stoichiometric mixture are zones of privileged stabilization of the flames.

[0016] Consequently, the low speeds in the first zone Z1 and the connection of the stoichiometric line to the second zone Z2 can induce a flame rise in the injection device.

[0017] There is therefore a need to reduce the risks of flame flare-up in a hydrogen injection system while limiting pressure losses.

[0018] This document aims to provide a simple, reliable and economical solution to this need. Résumé

[0019] A system is proposed for injecting a mixture of hydrogen and air along a first axis into an annular combustion chamber of a turbomachine. The injection system comprises a radially inner hydrogen circulation channel and a radially outer air circulation channel. The radially outer annular channel is arranged around the radially inner annular channel and is coaxial with the radially inner annular channel. The radially outer annular channel is delimited radially on the inside by a first wall surface and radially on the outside by a second wall surface. The injection system comprises an inner swirler being housed in the radially inner channel and an outer swirler being housed in the radially outer annular channel. A downstream end of the radially inner channel is arranged upstream along the first axis of a downstream end of the radially outer annular channel.The radially outer annular channel has an air circulation section. The section is convergent along the first axis at least from a downstream end of the inner swirler or a downstream end of the outer swirler to the downstream end of the radially inner channel.

[0020] By hydrogen circulation is meant that a central flow of fuel flowing in the radially internal channel comprises hydrogen. In particular, this central flow of fuel may comprise at least 90% hydrogen by mass, and in particular at least 95% hydrogen by mass, and advantageously at least 99% hydrogen by mass.

[0021] Hydrogen can in particular be in the form of dihydrogen.

[0022] The hydrogen is preferably in gaseous form.

[0023] By air circulation, it is meant that a peripheral flow of fuel flowing in the radially external annular channel comprises air. This peripheral flow may in particular comprise air enriched with dioxygen.

[0024] The term air circulation section means the passage section of an air flow in the radially external annular channel.

[0025] The air flow is in particular delimited radially inside by the first wall surface and radially outwardly by the second wall surface.

[0026] Convergent section means that said section decreases from upstream to downstream along the first axis in the direction of flow in the injection system. Similarly, divergent section means that said section increases from upstream to downstream along the first axis in the direction of flow in the injection system.

[0027] The injection system according to the present disclosure advantageously makes it possible to produce a flame which makes it possible to reduce both the level of nitrogen oxide emissions and the thermal stress on the combustion chamber.

[0028] In addition, the convergent air circulation section of the radially external annular channel makes it possible to further limit the risks of flame rise in the injection system, in particular in comparison with the injection device described in document WO2023057722A1. Indeed, this convergent section makes it possible to accelerate the air flow in the radially external annular channel and thus to limit or even avoid the separation of the flow near the downstream end of the radially internal channel which generates the appearance of a zone with low flow speed. This accelerated flow makes it possible to avoid the rise of flames along the stoichiometric lines in the injection system.

[0029] Furthermore, the injection system according to the present disclosure has the particularity of being both simple to produce and easily adaptable to existing turbomachines operating on kerosene.

[0030] The features set out in the following paragraphs may, optionally, be implemented independently of one another or in combination with one another.

[0031] The injection system according to the present disclosure may in particular be used in a hydrogen-lean combustion configuration. As expressed previously, the mixture is said to be “rich” when the hydrogen is in excess relative to the air, and conversely, the mixture is said to be “lean” when the air is in excess relative to the hydrogen. This makes it possible to reduce nitrogen oxide emissions and temperatures in the combustion chamber.

[0032] In order to form the converging airflow section, it should be noted that it is possible to adapt the first wall surface and / or the second wall surface.

[0033] The injection system comprises in particular a first wall and a second wall. The first wall delimits radially on the outside the radially internal channel and radially on the inside the radially external annular channel. The second wall delimits radially on the outside the radially external annular channel.

[0034] The first wall surface forms in particular a radially external surface of the first wall. The second wall surface forms in particular a ra- internally of the second wall. The air flow is then delimited radially on the outside by the second wall and radially on the inside by the first wall.

[0035] The air circulation section may be divergent downstream of the downstream end of the radially internal channel. This characteristic advantageously makes it possible to widen the internal recirculation zone and limit the vortices generated at the outlet of the injection system.

[0036] The radially internal channel advantageously has a tubular shape.

[0037] Advantageously, an angle [3, formed between a first straight line connecting a first point and a second point of the second wall surface and a second straight line connecting a third point and a fourth point of the first wall surface, is greater than or equal to 1°, preferably between 1° and 20°. The first point and the second point are at a distance from each other along the first axis. Similarly, the third point and the fourth point are at a distance from each other along the first axis. The implementation of this angle [3 makes it possible to obtain a section whose convergence is sufficient to ensure a flow velocity high enough to avoid a flow deflection, in particular near the downstream end of the radially internal channel.

[0038] Advantageously, the first point can be positioned at a height along the first axis of the downstream end of the internal spiral or the first point can be positioned at a height along the first axis of the downstream end of the external spiral. In addition, the second point can be positioned at a height along the first axis of the downstream end of the radially internal channel. This choice of points makes it possible to take into account the convergence of said section over a length adapted along the first axis.

[0039] Advantageously, the third point can be positioned at a height along the first axis of the downstream end of the internal spiral or the third point can be positioned at a height along the first axis of the downstream end of the external spiral. In addition, the fourth point can be positioned at a height along the first axis of the downstream end of the radially internal channel. This choice of points makes it possible to take into account the convergence of said section over a length adapted along the first axis.

[0040] Advantageously, an angle [3e, formed between the first axis and the first straight line, is between 0° and 50°. This characteristic makes it possible to obtain a section whose convergence is sufficient to ensure a flow speed high enough to avoid separation of the flow, in particular near the downstream end of the radially internal channel.

[0041] At least a portion of the second wall surface may advantageously have a rectilinear shape along the first axis. This channel geometry makes it possible to easily implement the convergence of the air circulation section in the radially external annular canal.

[0042] For example, said at least one portion of the second rectilinear wall surface may extend along the first axis between a position at the height of the downstream end of the external spiral and a position at the height of the downstream end of the internal spiral, or even of the downstream end of the radially internal channel, and even of the downstream end of the radially external annular channel.

[0043] At least a portion of the second wall surface may advantageously have a curved shape along the first axis.

[0044] At least a portion of the first wall surface may advantageously have a rectilinear shape along the first axis. This channel geometry makes it easy to implement the convergence of the air circulation section in the radially external annular channel.

[0045] For example, said at least one portion of the first rectilinear wall surface may extend along the first axis between a position at the height of the downstream end of the internal spiral and a position at the height of the downstream end of the radially internal channel.

[0046] At least a portion of the first wall surface may advantageously have a curved shape along the first axis.

[0047] A thickness of the first wall may advantageously decrease from upstream to downstream along the first axis. The thickness may in particular decrease to a minimum thickness at the downstream end of the radially internal channel. The minimum thickness may in particular be imposed by the manufacturing means.

[0048] Advantageously, a length along the first axis, between the downstream end of the external swirler and the downstream end of the radially internal channel, is greater than or equal to 4 mm. Said length is in particular sufficiently reduced to limit the formation of low-speed zones near the downstream end of the radially internal channel and therefore to limit the risks of flames rising, and sufficiently high to dissipate the wake effects of the swirlers.

[0049] According to another aspect, there is provided an assembly comprising said injection system, hydrogen supply means and air supply means. The radially inner channel is fluidly connected to the hydrogen supply means, the inner swirler being configured to rotate the hydrogen. The radially outer annular channel is fluidly connected to the air supply means, the outer swirler being configured to rotate the air.

[0050] The hydrogen supply means are in particular adapted to deliver a flow of hydrogen in gaseous form without diluting gas, that is to say a flow comprising at least 90% hydrogen by mass, and in particular at least 95% hydrogen by mass, and advantageously at least 99% hydrogen by mass. The hydrogen can in particular be in the form of dihydrogen. The hydrogen supply means comprise, for example, at least one pressurized tank equipped with at least one valve, and / or at least one device for chemically generating gaseous hydrogen.

[0051] The air supply means are in particular adapted to deliver an air flow without adding diluent gas. The air supply means comprise, for example, an atmospheric air inlet upstream of the turbomachine. This air is compressed before entering the annular combustion chamber. The air supply means may also comprise a source of oxygen for enriching the air flow with oxygen. The source of oxygen may comprise a pressurized oxygen tank provided with a valve and / or means for chemically generating gaseous oxygen.

[0052] According to another aspect, there is provided a hydrogen combustion device comprising an annular combustion chamber and at least one injection system as previously described which opens into the annular combustion chamber along the first axis.

[0053] The combustion device may comprise a plurality of injection systems distributed annularly around an axis of the annular combustion chamber.

[0054] According to another aspect, a turbomachine is provided comprising the combustion device as previously described. Brief description of the drawings

[0055] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawings, in which:

[0056] [Fig-1] schematically illustrates a partial sectional view of an example of a tur machine comprising an injection device according to a prior embodiment in two configurations.

[0057] [Fig.2] schematically illustrates a partial sectional view of a device injection according to a previous embodiment.

[0058] [Fig.3] schematically illustrates a partial sectional view of a device injection according to another prior embodiment.

[0059] [Fig.4] shows flow simulation results within the device injection according to a previous embodiment.

[0060] [Fig.5] schematically illustrates a partial sectional view of an example of a tur bomachine comprising an injection system according to the present disclosure in two configurations.

[0061] [Fig.6] schematically illustrates two partial sectional views (Figures 6A and 6B) of the injection system according to the present disclosure.

[0062] [Fig.7] schematically illustrates a partial sectional view of the injection system according to this disclosure.

[0063] [Fig.8] schematically illustrates a plurality of possible configurations (figures 8A, 8B, 8C, 8D, 8E, 8F and 8G) of the injection system according to the present disclosure.

[0064] [Fig.9] schematically illustrates a plurality of possible configurations (figures 9A, 9B, 9C and 9D) of the injection system according to the present disclosure. Description of the embodiments

[0065] Reference is now made to [Fig. 5] schematically representing a system 20 for injecting a mixture of hydrogen and air along a first axis XI into an annular combustion chamber 4 of a turbomachine 1 with an axis hereinafter designated second axis X2. The turbomachine may for example be a gas turbine, a turboprop, or an aircraft turbojet.

[0066] The present disclosure also relates to a hydrogen combustion device 30 comprising the annular combustion chamber 4 and at least one injection system which opens into the annular combustion chamber along the first axis. The combustion device may comprise a plurality of injection systems distributed annularly around an axis of the annular combustion chamber.

[0067] As illustrated in [Fig.5], the annular combustion chamber 4 is in particular arranged so as to open onto a high-pressure turbine, the annular combustion chamber being in particular positioned between a compressor 3 and the high-pressure turbine 5. In addition, the annular combustion chamber 4 can be oriented substantially along the second X2. Alternatively, the annular combustion chamber 4 can be transverse to said second axis X2.

[0068] In addition, the combustion chamber 4 may comprise a radially inner annular wall and a radially outer annular wall coaxial with the axis of the combustion chamber. The radially inner and outer annular walls are connected at their upstream end by an annular chamber bottom wall. The injection system 20 is in particular mounted on this annular chamber bottom wall.

[0069] Figures 6A, 6B and 7 schematically represent sectional views of the injection system 20 according to the present disclosure. The injection system 20 comprises a radially internal channel 21 for circulating hydrogen and a radially external annular channel 22 for circulating air. The radially internal channel 21 has in particular a tubular shape. The radially external annular channel 22 is arranged around the radially internal annular channel 21 and is coaxial with the radially internal annular channel 21. The radially external annular channel 22 is delimited radially on the inside by a first wall surface S1 and radially on the outside by a second wall surface S2.

[0070] The injection system 20 comprises in particular a first wall 201 and a second wall 202. The first wall 201 delimits radially on the outside the radially internal channel 21 and radially on the inside the radially external annular channel 22. The second wall 202 delimits radially on the outside the radially external annular channel 22.

[0071] The first wall 201 has in particular a thickness e.

[0072] The radially internal channel 21 has in particular a diameter D1, called the internal diameter, at its downstream end 25. The choice of the internal diameter D1 depends in particular on a desired thermal power.

[0073] The radially external annular channel 22 has in particular a diameter D2, called the external diameter at its downstream end 26.

[0074] The downstream end 25 of the radially internal channel 27 can advantageously be arranged at a distance L2 along the first axis XI upstream of the downstream end 26 of the radially external annular channel 22.

[0075] By hydrogen circulation, it is meant that a central flow of fuel flowing in the radially internal channel 21 comprises hydrogen. In particular, this central flow of fuel may comprise at least 90% hydrogen by mass, and in particular at least 95% hydrogen by mass, and advantageously at least 99% hydrogen by mass.

[0076] Hydrogen can in particular be in the form of dihydrogen.

[0077] The hydrogen is preferably in gaseous form.

[0078] Air circulation means that a peripheral flow of fuel flowing in the radially external annular channel comprises air. This peripheral flow may in particular comprise air enriched with dioxygen.

[0079] Convergent section means that said section decreases from upstream to downstream along the first axis in the direction of flow in the injection system. Similarly, divergent section means that said section increases from upstream to downstream along the first axis in the direction of flow in the injection system.

[0080] The injection system 20 according to the present disclosure may preferably be used in a hydrogen-lean combustion configuration. As expressed previously, the mixture is said to be “rich” when the hydrogen is in excess relative to the air, and conversely, the mixture is said to be “lean” when the air is in excess relative to the hydrogen. This makes it possible to reduce nitrogen oxide emissions and temperatures in the combustion chamber.

[0081] In addition, the injection system comprises an internal swirler 23 housed in the radially internal channel 21 and an external swirler 24 housed in the radially external annular channel 22. The swirlers, commonly referred to as "swirlers" in the English, allow the flows passing through them to rotate. The internal swirler 23 is thus configured to rotate the hydrogen and the external swirler 24 to rotate the air.

[0082] The external spiral 24 can in particular be arranged upstream along the first axis XI of the internal spiral 23.

[0083] The internal spiral 23 may in particular be arranged at a given distance from the downstream end 25 of the radially internal channel 21. This distance allows a central recirculation zone to be established. Indeed, the rotational movement of the air creates a centrifugal effect, which in turn generates a depression in the center of the flow which is the origin of the central recirculation zone. This further contributes to avoiding possible flame flare-ups.

[0084] In addition, hydrogen supply means and air supply means may be implemented. Said injection system, the hydrogen supply means and the air supply means form an assembly.

[0085] The radially inner channel is then fluidly connected to the hydrogen supply means and the radially outer annular channel is fluidly connected to the air supply means.

[0086] The hydrogen supply means are in particular adapted to deliver a flow of hydrogen in gaseous form without diluting gas, that is to say a flow comprising at least 90% hydrogen by mass, and in particular at least 95% hydrogen by mass, and advantageously at least 99% hydrogen by mass. The hydrogen may in particular be in the form of dihydrogen. The hydrogen supply means comprise for example at least one pressurized tank provided with at least one valve, and / or at least one device for chemical generation of gaseous hydrogen.

[0087] The air supply means are in particular adapted to deliver an air flow without adding diluent gas. The air supply means comprise, for example, an atmospheric air inlet upstream of the turbomachine. This air is compressed before entering the annular combustion chamber. The air supply means may also comprise a source of oxygen for enriching the air flow with oxygen. The source of oxygen may comprise a pressurized oxygen tank provided with a valve and / or means for chemically generating gaseous oxygen.

[0088] Furthermore, the downstream end 25 of the radially internal channel 21 is arranged upstream along the first axis XI of a downstream end 26 of the radially external annular channel 22.

[0089] This configuration of the injection system 20 advantageously makes it possible to produce a flame which makes it possible both to reduce the level of nitrogen oxide emissions and the thermal stress on the combustion chamber.

[0090] The radially external annular channel 22 has an air circulation section Al. By air circulation section Al is meant the passage section of an air flow in the radially external annular channel. The section Al is hatched in FIG. 6B.

[0091] This air flow is in particular delimited radially on the outside by the second wall surface S2 and radially on the inside by the first wall surface SL.

[0092] The section Al is convergent along the first axis XI at least from a downstream end 27 of the internal swirler 23 or a downstream end 28 of the external swirler 24, to the downstream end 25 of the radially internal channel 21. By the section Al is convergent it is understood that its area decreases from upstream to downstream along the first axis XI in the direction of flow within the injection system.

[0093] The convergent air circulation section Al of the radially external annular channel 22 makes it possible to further limit the risks of flames rising in the injection system, in particular in comparison with the injection device described in document WO2023057722A1.

[0094] Indeed, this convergent section Al makes it possible to accelerate the flow of air in the radially external annular channel 22 and thus to limit or even avoid the separation of the flow near the downstream end 25 of the radially internal channel 21 which generates the appearance of a zone with low flow speed. This accelerated flow makes it possible to avoid the rise of flames along the stoichiometric lines in the injection system 20.

[0095] Furthermore, the injection system according to the present disclosure has the particularity of being both simple to produce and easily adaptable to existing turbomachines operating on kerosene.

[0096] In order to form the convergent air circulation section A1, it should be noted that it is possible to adapt the first wall surface S1 radially delimiting on the inside the radially external annular channel 22 and / or the second wall surface S2 radially delimiting on the outside the radially external annular channel 22. The first wall surface S1 forms in particular a radially external surface of the first wall 201. The second wall surface S2 forms in particular a radially internal surface of the second wall 202. In other words, the air circulation is delimited on the outside by the second wall 202 and delimited on the inside by the first wall 201.

[0097] Furthermore, the thickness e of the first wall 201 can decrease from upstream to downstream along the first axis XL. The thickness e can in particular decrease to a minimum thickness at the downstream end 25 of the radially internal channel 21. The thickness minimum may in particular be imposed by the means of manufacture.

[0098] Furthermore, a length L1 along the first axis XI, between the downstream end 28 of the external swirler 24 and the downstream end 25 of the radially internal channel 21, is advantageously greater than or equal to 4 mm, preferably between 4 mm and 30 mm. The length L1 is in particular sufficiently reduced to limit the formation of low-speed zones near the downstream end of the radially internal channel and therefore to limit the risks of flames rising, and sufficiently high to dissipate the wake effects of the swirlers.

[0099] Reference is now made to [Fig.7]. In order to better define the convergence of the airflow section, points respectively of the radially inner channel and the radially outer annular channel are defined below.

[0100] In particular, a first straight line dl connects a first point P1,P1' and a second point P2 of the second wall surface S2 and a second straight line d2 connects a third point P3 and a fourth point P4 of the first wall surface SI. The first point PI,PI' and the second point P2 are at a distance from each other along the first axis XL. The third point P3,P3' and the fourth point P4 are at a distance from each other along the first axis XL.

[0101] An angle [3, formed between the first straight line d1 and the second straight line d2, is greater than or equal to 1°, preferably between 1° and 20°. The implementation of this angle [3 makes it possible to obtain a section whose convergence is sufficient to ensure a flow speed high enough to avoid a flow deflection, in particular near the downstream end of the radially internal channel.

[0102] More precisely, the first point PI is positioned at a height along the first axis XI of the downstream end 27 of the internal spiral 23 or the first point PI' is positioned at a height along the first axis XI of the downstream end 28 of the external spiral 24. The second point P2 is in particular positioned at a height along the first axis XI of the downstream end 25 of the radially internal channel 21. This choice of points makes it possible to take into account the convergence of said section over a length adapted along the first axis.

[0103] More precisely, the third point P3 is positioned at a height along the first axis XI of the downstream end 27 of the internal spiral 23 or the third point P3' is positioned at a height along the first axis XI of the downstream end 28 of the external spiral 24. The fourth point P4 is notably positioned at a height along the first axis XI of the downstream end 25 of the radially internal channel 21. This choice of points makes it possible to take into account the convergence of said section over a length adapted along the first axis.

[0104] Let an angle [3e, formed between the first axis XI and the first straight line dl. The angle [3e is preferably between 0° and 50°. This characteristic makes it possible to obtain a section whose convergence is sufficient to ensure a flow velocity high enough to avoid flow separation, particularly near the downstream end of the radially internal channel.

[0105] Let an angle [3;, formed between the first axis XI and the second line d2.

[0106] The angle [3 can be defined according to the following equation:

[0107] Furthermore, when the thickness e of the first wall 201 decreases from upstream to downstream along the first axis XI, with, as limit thicknesses, a thickness e0 at the height of the downstream end 28 of the external spiral 24 and a thickness ecc at the height of the downstream end 25 of the radially internal channel 21, the angle [3; can be defined according to the following equation:

[0108] )

[0109] Figures 8 and 9 represent several possible configurations (figures 8A, 8B, 8C, 8D, 8E, 8F, 8G, 9A, 9B, 9C and 9D) of the injection system, the essential thing being to have a convergent section of air circulation in the radially external annular channel at least between the downstream end of the internal swirler, or even the downstream end of the external swirler, and the downstream end of the radially internal channel.

[0110] The air circulation section Al may be divergent downstream of the downstream end 25 of the radially internal channel 21. This characteristic advantageously makes it possible to widen the internal recirculation zone and limit the vortices generated at the outlet of the injection system.

[0111] At least a portion of the second wall surface S2 may advantageously have a rectilinear shape along the first axis XL. This channel geometry makes it easy to implement the convergence of the air circulation section in the radially external annular channel.

[0112] For example, said at least one portion of the second wall surface S2 of rectilinear shape may extend along the first axis XI between a position at the height of the downstream end 28 of the external spiral 24 and a position at the height of the downstream end 27 of the internal spiral 23, or even of the downstream end 25 of the radially internal channel 21, and even of the downstream end 26 of the radially external annular channel 22.

[0113] At least a portion of the second wall surface S2 may advantageously have a curved shape along the first axis XL.

[0114] At least a portion of the first wall surface SI may advantageously have a rectilinear shape along the first axis XL. This channel geometry makes it easy to implement the convergence of the air circulation section in the radially external annular channel.

[0115] For example, said at least one portion of the first wall surface SI of shape rectilinear can extend along the first axis between a position at the height of the downstream end of the internal spiral and a position at the height of the downstream end of the radially internal channel.

[0116] At least a portion of the first wall surface SI may advantageously have a curved shape along the first axis XI.

[0117] In the example of Figure 8A, the second wall surface S2 is of rectilinear and convergent shape and extends along the first axis XI between a position at the height of the downstream end 28 of the external spiral 24 and a position at the height of the downstream end 26 of the radially external annular channel 22. The first wall surface SI is of rectilinear shape and extends along the first axis between a position at the height of the downstream end of the internal spiral and a position at the height of the downstream end 25 of the radially internal channel 21.

[0118] Furthermore, in the example of FIG. 8A, only the second wall surface S2 is inclined relative to the first axis XI, the first wall surface SI extending substantially along the first axis XL.

[0119] In the example of Figure 8B, the second wall surface S2 comprises a first portion S21 of rectilinear and convergent shape and a second portion S22 of rectilinear and divergent shape, the second portion S22 extending after the first portion S21 along the first axis XL.

[0120] The first portion S21 extends along the first axis XI between a position at the height of the downstream end 28 of the external spiral 24 and a position at the height of the downstream end 25 of the radially internal channel 21. The second portion S22 extends along the first axis XI between a position at the height of the downstream end 25 of the radially internal channel 21 and a position at the height of the downstream end 26 of the radially external annular channel 22.

[0121] The first wall surface SI is of rectilinear and divergent shape and extends along the first axis XI between a position at the height of the downstream end of the internal spiral and a position at the height of the downstream end 25 of the radially internal channel 21.

[0122] In the example of Figure 8C, the second wall surface S2 comprises a first portion S21 of curved and convergent shape and a second portion S22 of curved and divergent shape, the second portion S22 extending after the first portion S21 along the first axis XL.

[0123] The first portion S21 extends along the first axis XI between a position at the height of the downstream end 28 of the external spiral 24 and a position at the height of the downstream end 25 of the radially internal channel 21. The second portion S22 extends along the first axis XI between a position at the height of the downstream end 25 of the radially internal channel 21 and a position at the height of the downstream end 26 of the radially external annular channel 22.

[0124] Furthermore, in the example of FIG. 8C, the first wall surface SI is of rectilinear shape and extends along the first axis XI between a position at the height of the downstream end of the internal spiral and a position at the height of the downstream end 25 of the radially internal channel 21. Furthermore, the first wall surface SI of the radially internal channel 21 extends substantially along the first axis XI.

[0125] In the examples of figures 8D and 8E, the first wall surface SI is of rectilinear and convergent shape and extends along the first axis XI between a position at the height of the downstream end of the internal spiral and a position at the height of the downstream end 25 of the radially internal channel 21.

[0126] In particular, in the example of FIG. 8D, the second wall surface S2 is of rectilinear and convergent shape and extends along the first axis XI between a position at the height of the downstream end 28 of the external spiral 24 and a position at the height of the downstream end 26 of the radially external annular channel 22.

[0127] In the example of Figure 8E, the second wall surface S2 comprises a first portion S21 of curved and convergent shape and a second portion S22 of curved and divergent shape, the second portion S22 extending after the first portion S21 along the first axis XI.

[0128] The first portion S21 extends along the first axis XI between a position at the height of the downstream end 28 of the external spiral 24 and a position at the height of the downstream end 25 of the radially internal channel 21. The second portion S22 extends along the first axis XI between a position at the height of the downstream end 25 of the radially internal channel 21 and a position at the height of the downstream end 26 of the radially external annular channel 22.

[0129] In the example of Figure 8F, the first wall surface S1 is rectilinear in shape and diverges along the first axis X and the second wall surface S2 is rectilinear in shape and extends substantially along the first axis XL.

[0130] Thus, in the example of FIG. 8F, only the first wall surface SI is inclined relative to the first axis XI, the second wall surface S2 extending substantially along the first axis XL.

[0131] It should be noted, however, that the divergent configuration of the first wall surface S1 can also be implemented with other configurations of the second wall surface S2, as illustrated in Figures 8A, 8B, 8C and Figures 9A to 9D.

[0132] In the example of Figure 8G, the first wall surface S1 is curved and divergent along the first axis X and the second wall surface S2 is rectilinear and extends substantially along the first axis XL.

[0133] Thus, in the example of Figure 8G, only the first wall surface SI is curved relative to the first axis XI, the second wall surface S2 extending substantially along the first axis XI.

[0134] It should be noted, however, that the divergent configuration of the first wall surface S1 can also be implemented with other configurations of the second wall surface S2, as illustrated in Figures 8A, 8B, 8C and Figures 9A to 9D.

[0135] With reference to Figures 9A, 9B, 9C and 9D, the geometry of the internal or external swirlers can also be adapted in order to obtain higher flow velocities.

[0136] In the examples of Figures 9A and 9B, the geometry of the external swirler is notably adapted so as to implement a convergent section of air circulation in the radially external annular channel at least from an upstream end of the external swirler.

[0137] The first wall surface SI is of rectilinear shape and extends along the first axis XI between a position at the height of the downstream end of the internal spiral and a position at the height of the downstream end 25 of the radially internal channel 21.

[0138] In the example of Figure 9A, the second wall surface S2 is of rectilinear and convergent shape and extends along the first axis XI between a position upstream of the upstream end of the external spiral 24 and a position at the height of the downstream end 26 of the radially external annular channel 22.

[0139] In the example of Figure 9B, the second wall surface S2 comprises a first portion S21 of curved and convergent shape and a second portion S22 of curved and divergent shape, the second portion S22 extending after the first portion S21 along the first axis XL.

[0140] The first portion S21 extends along the first axis XI between a position at the height of the downstream end 28 of the external spiral 24 and a position at the height of the downstream end 25 of the radially internal channel 21. The second portion S22 extends along the first axis XI between a position at the height of the downstream end 25 of the radially internal channel 21 and a position at the height of the downstream end 26 of the radially external annular channel 22.

[0141] In the examples of Figures 9C and 9D, the geometry of the internal swirler is notably adapted so as to implement a convergent section of hydrogen circulation in the radially internal channel at least from an upstream end of the internal swirler.

[0142] The first wall surface SI is of rectilinear shape and extends along the first axis XI between a position at the height of the upstream end of the internal spiral and a position at the height of the downstream end 25 of the radially internal channel 21.

[0143] In the example of Figure 9C, the second wall surface S2 is of rectilinear and convergent shape and extends along the first axis XI between a position at height of the downstream end of the external spiral 24 and a position at the height of the downstream end 26 of the radially external annular channel 22.

[0144] In the example of Figure 9D, the second wall surface S2 comprises a first portion S21 of curved and convergent shape and a second portion S22 of curved and divergent shape, the second portion S22 extending after the first portion S21 along the first axis XI.

[0145] The first portion S21 extends along the first axis XI between a position at the height of the downstream end 28 of the external spiral 24 and a position at the height of the downstream end 25 of the radially internal channel 21. The second portion S22 extends along the first axis XI between a position at the height of the downstream end 25 of the radially internal channel 21 and a position at the height of the downstream end 26 of the radially external annular channel 22.

[0146] Furthermore, it should be noted that the internal swirler 23 may have a central opening capable of allowing a portion of the hydrogen to circulate in a non-swirling flow. This non-swirling portion of the hydrogen makes it possible to push back the central recirculation zone, so that the burnt gases cannot come into contact with the swirlers.

Claims

Claims

1. System (20) for injecting a mixture of hydrogen and air along a first axis (XI) into an annular combustion chamber (4) of a turbomachine (1), the injection system (20) comprising: - a radially internal channel (21) for circulating hydrogen, - a radially external annular channel (22) for circulating air, the radially external annular channel (22) being arranged around the radially internal annular channel (21) and being coaxial with the radially internal annular channel (21), the radially external annular channel (22) being delimited radially on the inside by a first wall surface (SI) and radially on the outside by a second wall surface (S2), - an internal swirler (23) being housed in the radially internal channel (21), - an external swirler (24) being housed in the radially external annular channel (22),wherein a downstream end (25) of the radially internal channel (21) is arranged upstream along the first axis (XI) of a downstream end (26) of the radially external annular channel (22), the radially external annular channel (22) having an air circulation section (Al), the section (Al) being convergent along the first axis (XI) at least from a downstream end (27) of the internal swirler (23) or a downstream end (28) of the external swirler (24), to the downstream end (25) of the radially internal channel (21).,

2. Injection system (20) according to claim 1, wherein an angle [3, formed between a first straight line (dl) connecting a first point (PI, PI') and a second point (P2) of the second wall surface (S2) and a second straight line (d2) connecting a third point (P3) and a fourth point (P4) of the first wall surface (SI), is greater than or equal to 1°, preferably between 1° and 20°, the first point (P1, P1') and the second point (P2) being at a distance from each other along the first axis (XI), the third point (P3, P3') and the fourth point (P4) being at a distance from each other along the first axis (XI).

3. Injection system (20) according to the preceding claim, in which the first point (P1, P1') is positioned at a height along the first axis (XI) of the downstream end (27) of the internal spiral (23) or the first point (PT) is positioned at a height along the first axis (XI) of the downstream end downstream (28) of the external spiral (24), the second point (P2) being positioned at the height along the first axis (XI) of the downstream end (25) of the radially internal channel (21).

4. Injection system (20) according to one of claims 2 or 3, in which the third point (P3) is positioned at a height along the first axis (XI) of the downstream end (27) of the internal spiral (23) or the third point (P3') is positioned at a height along the first axis (XI) of the downstream end (28) of the external spiral (24), the fourth point (P4) being positioned at a height along the first axis (XI) of the downstream end (25) of the radially internal channel (21).

5. Injection system (20) according to one of claims 2 to 4, in which an angle [3e, formed between the first axis (XI) and the first straight line (dl), is between 0° and 50°.

6. Injection system (20) according to one of the preceding claims, in which the air circulation section (Al) is divergent downstream of the downstream end (25) of the radially internal channel (21).

7. Injection system (20) according to one of the preceding claims, in which the radially internal channel (21) has a tubular shape.

8. Injection system (20) according to one of the preceding claims, in which at least a portion of the second wall surface (S2) has a rectilinear shape along the first axis (XI).

9. Injection system (20) according to one of the preceding claims, in which a length (L1) along the first axis (XI), between the downstream end (28) of the external spiral (24) and the downstream end (25) of the radially internal channel (21), is greater than or equal to 4 mm.

10. Hydrogen combustion device (30) comprising an annular combustion chamber (4) and at least one injection system (20) according to one of the preceding claims which opens into the annular combustion chamber (4) along the first axis (XI).

11. Turbomachine (1) comprising the combustion device (30) according to the preceding claim.

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