Injection assembly for aircraft turbomachine and combustion device including the injection assembly

Abstract

Injection assembly (70) for an aircraft turbomachine comprising: a fuel mixture channel (30) including a fuel mixture throat (37) and intended to communicate with a combustion chamber (90) in order to supply the combustion chamber (90) with a flow of fuel mixture (32), an external air channel (40) extending around the fuel mixture channel (30) and intended to communicate with the combustion chamber (90) in order to supply the combustion chamber (90) with an external air flow (42), a gaseous fuel injection device (8), the gaseous fuel injection device (8) comprising a fuel injection channel (10) communicating with the fuel mixture channel (30), a combustion air channel (20) extending coaxially with the fuel injection channel (10) and communicating with the fuel mixture channel (30). Figure for the abbreviation: Figure 2

Description

Title of the invention: Injection assembly for aircraft turbomachine and combustion device comprising the injection assembly. Scope of disclosure

[0001] This disclosure relates to the field of injection assemblies for gas turbines such as aircraft turbomachinery powered by hydrogen and air. This includes, in particular, civil and military aeronautical applications: helicopters, vertical takeoff and landing aircraft (VTOL), drones, auxiliary power units (APUs), turbogenerators, fixed-wing aircraft for recreational, business, or commercial aviation, turbojets, or turboprops. This disclosure further relates to a combustion device comprising the injection assembly and a combustion chamber. State of the art

[0002] The propulsion sector, and in particular the aeronautical sector, faces major environmental challenges. The interest in using hydrogen combustion rather than kerosene is growing stronger, because hydrogen combustion avoids carbon-based pollutant emissions such as carbon dioxide, carbon monoxide, unburned hydrocarbons, and fine particles and smoke.

[0003] A principle for micro-mixing air-dihydrogen burners is known. Burners based on this principle are complex to integrate and can present problems associated with the interaction between different flames, which have an adverse effect on flame propagation and / or thermo-acoustic stability. Such burners present a risk of high manufacturing and mass costs and are specific to a given combustion chamber architecture.

[0004] A direct hydrogen injection system has also been described in document WO2023 / 180318 Al.

[0005] At the level of injection and combustion, two main technological configurations for hydrogen-air injection systems applied to gas turbines exist, namely lean injection systems, and rich injection systems.

[0006] More generally, it is important to note that lean-burn fuel supply processes tend to generate significant thermoacoustic instabilities that can damage these systems and create risks of flashback, whereas stable combustion is necessary to avoid altering the engine performance. Rich combustion fuel processes, on the other hand, tend to emit more pollutants than lean combustion processes if they are not properly sized.

[0007] The use of hydrogen involves several issues to be taken into consideration at the combustion chamber level:

[0008] Under equivalent thermodynamic conditions of pressure, temperature, and air-fuel ratio, the adiabatic temperature of the flame in a hydrogen-air combustion is higher than that of the flame in a kerosene-air combustion, particularly in the case of a rich mixture, which can lead to an uncontrolled increase in nitrogen oxides. However, the flammability limits of hydrogen are wider than those of kerosene, allowing the mixture to ignite at lower or higher air-fuel ratios than kerosene.

[0009] Similarly, the flame speeds resulting from hydrogen-air combustion are higher than for kerosene-air flames. A high flame speed can lead to flashback problems in injection systems, particularly at the boundary layers, and cause serious damage to these systems.

[0010] Finally, the combustion of hydrogen with air tends to emit much more noise than an air-kerosene combustion and can therefore generate significant noise pollution at airports, in the case of aeronautical use.

[0011] It is therefore sought to reduce combustion temperatures, to reduce sound waves from combustion and to limit the formation of nitrogen oxides in order to reduce both noise pollution and air pollution during the operation of the turbines.

[0012] At the burner level, documents GB2502298A and US6267585B1 describe chamber geometries based on the principle of a micromix burner. This type of burner is designed to miniaturize the reaction zone by creating a multitude of diffusion micro-flames up to 4 centimeters long. The combustion process relies on the injection of hydrogen perpendicular to an airflow that carries the hydrogen (known as jet-in-crossflow). Once the hydrogen has been rapidly added to the air, the mixture is injected into the combustion chamber and burned downstream of a multitude of injection holes. This technology reduces the risk of flashback, as there is no premixing before injection.The operability of this type of injector can be limited, as can the thermal resistance of the wall containing the injection holes, which is subjected to high temperatures. Furthermore, and most importantly, this technology presents problems, previously mentioned in the relevant section. with other technologies, integration, flame propagation, thermo-acoustic instabilities and potentially complex development for micro-mixing systems, which is particularly penalizing in an aeronautical application where operability is very important.

[0013] In the context of burners using kerosene, the document “Advanced Combustor Systems for Stationary Gas Turbine Engines, Phase I. Review and Preliminary Evaluation, Volume I”, SA Mosier, RM Pierce, Contract 68-02-2136, FR-11405, Final Report, US Environmental Protection Agency, 1980 proposes a geometry of type RQL according to the acronym used in the field for “Rich Burn-Quick Mix-Lean Burn” in English, or rich combustion-quick mix-lean combustion in French.

[0014] This geometry aims to stagger the air-kerosene mixture in the combustion chamber across several zones: a first zone near the injector outlets has a mixture ratio of approximately 1.8, followed by a second mixing zone with very high air density, the purpose of which is to minimize the formation of stoichiometric regions and NOx emissions, and to complete the initial rich combustion. Finally, to complete combustion, additional air injections are provided in a third zone to perform a second lean combustion at a mixture ratio of 0.5. Due to the specific characteristics of hydrogen, the traditional RQL geometry for kerosene combustion is not optimal and must be redesigned. Statement of Disclosure

[0015] This disclosure aims to address the various problems mentioned above. To this end, this disclosure relates to an injection system configured to perform a staged combustion of a fuel mixture of dihydrogen and air in a combustion chamber of a turbomachine, in order to limit NOx generation and reduce combustion noise, as described in documents WO2023 / 214129 A1 and WO2024 / 052611 A1

[0016] More specifically, the present disclosure proposes an injection assembly for an aircraft turbomachine, the injection assembly having a longitudinal axis and extending between an upstream portion and a downstream portion, the injection assembly comprising:

[0017] a fuel mixing channel, the fuel mixing channel extending along the longitudinal axis, the fuel mixing channel having a fuel mixing inlet and a fuel mixing outlet, the fuel mixing channel is intended to communicate with a combustion chamber at the fuel mixing outlet in order to supply the combustion chamber with a flow of fuel mixture,

[0018] an external air channel, the external air channel having an external air inlet and an external air outlet, the external air channel (is preferably tubular and) extends around the fuel mixture channel and is intended to communicate with the combustion chamber at the external air outlet in order to supply the combustion chamber with an external airflow extending around the fuel mixture flow,

[0019] a gaseous fuel injection device, the gaseous fuel injection device includes a fuel injection channel having a fuel inlet and a fuel outlet, the fuel injection channel includes a settling cavity and the fuel injection channel communicates with the fuel mixture channel via the fuel outlet and the fuel mixture inlet (the gaseous fuel injection device is configured to guide a fuel flow extending along a fuel injection axis, exiting the injection device at the fuel outlet and entering the fuel mixture channel at the fuel mixture inlet), and

[0020] a combustion air channel, the combustion air channel has a combustion air inlet and a combustion air outlet, the combustion air channel extends coaxially to the fuel injection channel at the combustion air outlet and communicates with the fuel mixture channel via the combustion air outlet and the fuel mixture inlet (the combustion air channel is configured to guide a combustion air flow, the combustion air flow exiting the combustion air channel at the combustion air outlet, entering the fuel mixture channel at the fuel mixture inlet and mixing with the fuel flow),

[0021] wherein the fuel injection channel preferably includes a fuel throat near the fuel outlet.

[0022] Thus, the fuel flow velocity at the fuel outlet is increased. Consequently, the fuel flow velocity at the fuel mixture inlet is further increased. As a result, more combustion air is drawn in, and the combustion air velocity at the fuel mixture inlet is further increased. The risk of flashback is therefore further reduced, and more generally, the advantages mentioned above are further enhanced. In addition, high fuel mixture flow velocities can be achieved without negatively impacting the pressure drop of the combustion gas flow. It is therefore an alternative system to conventional systems for achieving premixing such as jet-in-crossflow, jet-in-coflow, or injection slots.

[0023] According to a first aspect, in addition the gaseous fuel injection channel is configured to create a fuel pressure drop between the fuel inlet and the fuel outlet, the combustion air channel is configured to create a combustion air pressure drop between the combustion air inlet and the combustion air outlet, the injection assembly has a pressure drop ratio equal to the ratio between the fuel pressure drop and the combustion air pressure drop and the pressure drop ratio is between 3 and 10.

[0024] Thus, a staged combustion can be achieved, with a first combustion (the combustion of the fuel stream) that is rich and a second combustion (the combustion of the portion of the fuel not burned by the first combustion and the external air stream) that is lean. The risk of flashback is limited with a rich combustion (of the fuel mixture stream), because the flame speed is not accelerated by instabilities. Furthermore, the staggered richness prevents the formation of a stoichiometric flame front, because the first combustion occurs with an excess of hydrogen and the second combustion is tainted by the combustion gases (from the first combustion). This has the effect of significantly reducing the flame front speed. The flame front speed, which depends on the composition of the gases to be burned, is thus reduced. The stability of the combustion flame is improved by the pressure drop ratio.The stability of the combustion flame is a particularly critical point in the case of gaseous hydrogen.

[0025] Staged combustion of hydrogen for aeronautical applications avoids the nitrogen oxide formation zone by burning the rich hydrogen-air fuel mixture stream in a first zone and burning the residual gases in a second, lean zone. Staged combustion also allows for a wider operating range for the injection system.

[0026] Stabilizing a first flame front attached to the fuel mixture outlet for rich combustion and a second flame front slightly removed from the external air outlet reduces the thermoacoustic loads associated with combustion. In other words, since combustion is distributed over (at least) two flame fronts, the flame surface area is increased, which reduces the noise generated by combustion.

[0027] The risk of flashback is limited with rich combustion because thermal diffusion instabilities are not present on the first flame front. The flame speed is therefore not accelerated by these instabilities. Furthermore, the staggered richness of the mixture prevents the formation of a stoichiometric flame front, because the hydrogen is either rich (in the fuel mixture stream) or contaminated by combustion gases. This has the effect of reducing the flame front speed, which is highly dependent on the composition of the gases to be burned.

[0028] The robustness of the injection assembly is further increased. Since combustion is carried out at both high and low air-fuel ratios, the flame temperatures are lower than under stoichiometric conditions. Potential flame fronts originating from stoichiometric zones that might occur in reality will not be attached to the fuel outlet, thus limiting damage to the injection assembly. In the event of flame arrest, the low-temperature fuel mixture flow will improve the cooling of the hot walls of the fuel mixture channel. If necessary, cold hydrogen can also be circulated through the walls of the fuel injection device (similar to the regenerative circuits of a rocket engine combustion chamber).

[0029] The velocity of the gaseous fuel (hydrogen) is sufficiently high at the fuel outlet to prevent the stabilization of a flame front (by combustion of the fuel flow and the combustion air flow).

[0030] The fuel throat which allows the use of the high dynamic pressure of hydrogen at low temperature (between 200K and 250K) to partially draw in combustion air by venturi effect and to generate a rich fuel mixture at a speed greater than the flashback speed, as well as cooling of the walls of the fuel mixture channel, as well as the staged combustion with a rich fuel mixture (in gaseous hydrogen) allow to have a combustion air pressure drop of between 4% and 5%.

[0031] According to a second aspect, the gaseous fuel injection channel includes a pressure drop element configured to create a fuel pressure drop between the fuel inlet and the fuel outlet, the combustion air channel is configured to create a combustion air pressure drop between the combustion air inlet and the combustion air outlet, the injection assembly has a pressure drop ratio equal to the ratio between the fuel pressure drop and the combustion air pressure drop and the pressure drop ratio is between 3 and 10.

[0032] According to a third aspect, the injection assembly may be devoid of the characteristics mentioned in relation to the first and second aspects.

[0033] According to another characteristic in accordance with the disclosure, the fuel pressure loss is between 30% and 50%, preferably between 35% and 45%.

[0034] Thus, the gaseous fuel (hydrogen) jet at the fuel outlet can reach a speed between 0.4 Mach and 1 Mach.

[0035] According to another feature in accordance with the disclosure, the combustion air pressure drop is between 4% and 20%, preferably between 4% and 10%.

[0036] Thus, the air pressure drop of the gaseous hydrogen injection assembly according to the present disclosure is increased compared to a kerosene injection assembly due to the significantly higher turbulent flame speed for hydrogen-air combustion.

[0037] According to another feature in accordance with the disclosure, the fuel mixture channel preferably includes a fuel mixture throat near the fuel mixture inlet.

[0038] Thus, the mixing throat increases the velocity of the fuel mixture flow and creates a pressure reduction at the mixing throat, which draws in the combustion air flow and consequently increases the combustion air flow velocity. The risk of flashback and the stabilization of a flame front in the fuel mixture channel is thus reduced, because the velocity of the fuel mixture flow can be higher than the flashback velocity.

[0039] In the event of a flashback or unwanted ignition in the fuel mixture channel, the creation of a combustion zone will increase the pressure drop in the fuel mixture channel. This will result in a significant reduction in the combustion air flow, and therefore an increase in the fuel mixture richness, which will tend to reduce or even extinguish the unwanted combustion in the fuel mixture channel.

[0040] Preferably, the fuel mixture channel further comprises a convergent portion of the fuel mixture and a divergent portion of the fuel mixture. The convergent portion of the fuel mixture is adjacent to the throat of the fuel mixture and upstream of the throat of the fuel mixture, and the divergent portion of the fuel mixture is adjacent to the throat of the fuel mixture and downstream of the throat of the fuel mixture. The convergent portion of the fuel mixture, the throat of the fuel mixture, and the divergent portion of the fuel mixture follow one another from upstream to downstream to form a fuel mixture venturi.

[0041] Preferably, the fuel injection channel further comprises a convergent fuel portion and a divergent fuel portion. The convergent fuel portion is adjacent to the fuel throat and upstream of the fuel throat, and the divergent fuel portion is adjacent to the fuel throat and downstream of the fuel throat. The convergent fuel portion, the fuel throat, and the divergent fuel portion follow one another from upstream to downstream to form a fuel venturi.

[0042] According to another feature in accordance with the disclosure, preferably the injection assembly includes a flap in the combustion air channel, the flap is movable between a first position and a second position in order to vary the cross-section of the combustion air channel between a first section and a second section.

[0043] Thus, the combustion air flow (flow rate) can be modulated. In particular, in the case of turbomachinery with high pressure ratios and / or a wide operating range and extended operability, the modulation of the combustion air flow using the damper makes it possible to maintain a mixture richness in the fuel mixture flow within a desired range (between 2 and 4 for example).

[0044] Preferably the flap has a tubular shape.

[0045] According to yet another feature in accordance with the disclosure, preferably the injection assembly includes an internal air channel, the internal air channel extends in the longitudinal direction, coaxially with the fuel mixture channel and has an internal air outlet, the fuel mixture channel extends around the internal air channel in order to supply the combustion chamber at the level of the internal air outlet with an internal air flow surrounded by the fuel mixture flow (which is preferably annular).

[0046] The internal airflow allows for a more compact flame by distributing the combustion of the part of the fuel that was not burned by the first combustion (the combustion of the fuel flow) between the external annular combustion (the combustion of the part of the fuel that was not burned by the first combustion with the external airflow) and an internal annular combustion (the combustion of the part of the fuel that was not burned by the first combustion with the internal airflow).

[0047] According to a supplementary feature in accordance with the disclosure, the injection assembly further has the following features:

[0048] the internal air channel has an internal air inlet,

[0049] the fuel mixture channel is externally delimited by a fuel mixture wall,

[0050] the internal air channel is externally delimited by an internal air wall, and

[0051] The injection assembly comprises a plurality of fins, the fins extend into the fuel mixture channel between the fuel mixture wall and the internal air wall, the fins each contain a through channel extending between a through air inlet and a through air outlet, the through air outlet communicating with the internal air inlet, in order to supply the internal air channel with an internal airflow passing through the through channels.

[0052] Thus, the internal air channel is readily supplied by the internal airflow. Furthermore, since dihydrogen is preferably at a low temperature (between 200K and 250K) in the dihydrogen source, the fuel mixture flow is heated by the internal airflow passing through the channels. The fins therefore form a heat exchanger between the fuel mixture flow and the internal airflow, which are separated from each other by the fins.

[0053] In various embodiments of the injection assembly as disclosed, one or both of the following additional provisions may optionally be used:

[0054] the fuel mixing channel comprises a first portion and a second portion, the first portion of the fuel mixing channel has a cylindrical shape of revolution (in other words the fuel mixing channel 30 extends at the longitudinal axis X), the internal air channel extends coaxially to the second portion of the fuel mixing channel and the internal air channel is surrounded by the second portion of the fuel mixing channel (which is preferably annular);

[0055] the through channel communicates with the external air channel at the level of the through air inlet;

[0056] the fins are rigidly fixed to the fuel mixture wall and to the internal air wall;

[0057] the fins are, at least three in number, regularly distributed around the longitudinal axis and are inclined with respect to the longitudinal axis, in order to form a spiral rotating the fuel mixture flow around the longitudinal axis; the homogeneity of the fuel mixture flow is further improved;

[0058] the internal air wall has a portion of substantially conical shape near the internal air inlet;

[0059] the external air channel is internally delimited by the combustible mixture wall;

[0060] The injection assembly further comprises an intermediate channel extending between an intermediate air inlet and an intermediate air outlet, the intermediate channel communicates with the external air channel via the intermediate air outlet and the external air inlet, the intermediate channel communicates with the external air channel via the intermediate air outlet and the external air inlet, and the intermediate channel communicates with the through channel via the intermediate air outlet and the through air inlet;

[0061] the intermediate channel is substantially tubular and extends coaxially to the longitudinal axis, and the intermediate channel extends around the fuel mixture channel (essentially around the first part of the fuel mixture channel) and is separated from the fuel mixture channel by the fuel mixture wall.

[0062] In addition, the injection assembly preferably also has one and / or the other of the following characteristics:

[0063] the fuel outlet extends along the longitudinal axis (it is central, forms a disk and not a ring);

[0064] the fuel injection channel extends along a fuel injection axis, and

[0065] the longitudinal axis is in line with the fuel injection axis.

[0066] According to an alternative feature of the invention, the injection assembly preferably has the following features:

[0067] the fuel injection axis forms an angle between 30 degrees and 90 degrees with respect to the longitudinal axis,

[0068] The fuel mixture channel is externally delimited by a fuel mixture wall,

[0069] the fuel mixture wall has a fuel mixture passage and the fuel mixture inlet is located at the fuel mixture passage.

[0070] Preferably, the fuel injection axis is perpendicular to the longitudinal axis.

[0071] In various embodiments of the injection assembly as disclosed, one and / or the other of the following provisions may also be used:

[0072] the combustion air channel extends around the fuel injection channel;

[0073] the gaseous fuel injection device further includes a pressurized dihydrogen source, and the fuel injection channel is connected to the pressurized dihydrogen source by the fuel inlet;

[0074] The combustion air channel has a combustion air inlet and the combustion air channel is (connected to) supplied by an air compressor.

[0075] This disclosure further relates to a combustion device comprising the injection assembly and a combustion chamber, the fuel mixture channel communicating with the combustion chamber at the fuel mixture outlet and the external air channel communicating with the combustion chamber at the external air outlet. Brief description of the figures

[0076] Other features and advantages of this disclosure will become apparent in the following detailed description, with reference to the accompanying drawings in which:

[0077] [Fig. 1] represents a part of an aircraft turbomachine comprising a combustion device, the combustion device comprising an injection assembly and a combustion chamber,

[0078] [Fig.2] schematically represents at an enlarged scale the area identified as II in [Fig.1] corresponding to the combustion device, according to a first embodiment,

[0079] [Fig.3] schematically represents the combustion device for a turbomachine according to a second embodiment,

[0080] [Fig.4] schematically represents the combustion device for a turbomachine according to a variant of the second embodiment,

[0081] [Fig.5] schematically represents the variant of the second embodiment, according to the arrow marked VV in [Fig.4]. Detailed description of the disclosure

[0082] Figure 1 partially and schematically illustrates a turbomachine 100, in particular for aircraft. The turbomachine 100 has a rotation axis 110 and comprises a compressor 102, combustion devices 1, a high-pressure turbine 104, a first shaft 105, a low-pressure turbine 106 and a second shaft 107.

[0083] The compressor 102 can have several stages; in [Fig. 1] two stages are shown. The first shaft 105 is rotatable about the axis of rotation 110 and connects the high-pressure turbine 104 to the compressor 102. The second shaft 107 is also rotatable about the axis of rotation 110 and connects the low-pressure turbine 106 to a blower (not shown). The second shaft 107 extends partially inside the first shaft 105.

[0084] The turbomachine 100 includes a primary air circuit 108 flowing from upstream to downstream between a primary air inlet 108a and a primary air outlet 108b. Ambient air, forming primary air, enters the primary air circuit 108 through the primary air inlet 108a, and the primary air is then compressed in the compressor 102. The primary air then enters the combustion devices 1, which are regularly arranged around the axis of rotation 110 and positioned between the compressor 102 and the high-pressure turbine 104 along the direction of the axis of rotation 110. In the combustion devices 1, the primary air serves as an oxidizer for the combustion of a fuel. Then, the primary air from each combustion device 1 passes successively through the high-pressure turbine 104 and the low-pressure turbine 106 which it drives in rotation around the axis of rotation 110, before exiting through the primary air outlet 108b.Since the combustion devices 1 are identical or similar, only one combustion device is detailed below.

[0085] As illustrated in [Fig.2], the combustion device 1 extends between an upstream part 2 and a downstream part 4. The combustion device 1 has a longitudinal axis X. In the illustrated embodiment, the longitudinal axis X is parallel to the axis of rotation 110.

[0086] The combustion device 1 comprises an injection assembly 70 and a combustion chamber 90. The injection assembly 70 particularly comprises a device gaseous fuel injection 8, a combustion air channel 20, a fuel mixing channel 30, an external air channel 40.

[0087] The fuel mixture channel 30 extends from the upstream portion 2 to the downstream portion 4 along the longitudinal axis X, between a fuel mixture inlet 31 and a fuel mixture outlet 39. The fuel mixture channel 30 is delimited by a fuel mixture wall 34. The fuel mixture channel 30 communicates with the combustion chamber 90 at the fuel mixture outlet 39 in order to supply the combustion chamber 90 with a fuel mixture flow 32. The fuel mixture flow 32 is burned in the combustion chamber 90, creating a primary combustion represented by the primary combustion flame 92.

[0088] Preferably, a portion of the fuel mixture channel 30 forming a diffuser along the direction of the fuel mixture flow 32 is present at the fuel mixture outlet 39. In a particular embodiment, the diffusion of the fuel mixture flow 32 can be achieved by a section diverging downstream of the fuel mixture channel 30 at the fuel mixture outlet 39. Other shapes of the external air channel 40 at the external air outlet 49 would also be possible, as illustrated in particular in document WO2023 / 057722A1.

[0089] The fuel channel wall 34 is preferably tapered at the fuel mixture outlet 39 to reduce the presence of recirculation vortices in the combustion chamber 90 near the fuel mixture wall 34 and thus prevent the flame from catching on it.

[0090] The gaseous fuel injection device 8 comprises a pressurized dihydrogen source 6 and a fuel injection channel 10. The fuel injection channel 10 is delimited by a fuel injection wall 14. The fuel injection channel 10 extends from the upstream part 2 to the downstream part 4 along a fuel injection axis Y between a fuel inlet 11 and a fuel outlet 19. The fuel injection channel 10 is supplied with fuel (dihydrogen) at the fuel inlet 11 by the pressurized dihydrogen source 6. The fuel injection channel 10 communicates with the fuel mixture channel 30 via the fuel outlet 19 and the fuel mixture inlet 31.

[0091] The fuel injection channel 10 includes a fuel venturi near the fuel outlet 19. The fuel venturi comprises, successively, from the upstream portion 2 to the downstream portion 4, a converging fuel portion 16, a fuel throat 17, and a diverging fuel portion 18. The converging fuel portion 16 is substantially conical and adjacent to the fuel throat 17, and the diverging fuel portion 18 is substantially conical. attached to the fuel neck 17. In the embodiment illustrated in [Fig.2], the fuel venturi is integrated in projection inside the fuel wall 14.

[0092] The fuel injection channel 10 further includes a settling cavity 15 between the fuel inlet 11 and the fuel throat 17. In particular, the settling cavity 15 directly feeds the fuel throat 17; in other words, the settling cavity 15 opens into the fuel throat 17. The settling cavity has a cross-section significantly larger (at least 5 times, preferably at least 10 times) than the cross-section at the fuel throat 17. The fuel injection channel 10 guides a fuel flow 12 extending along the fuel injection axis Y. The fuel flow 12 is substantially cylindrical, extends along the fuel injection axis Y and around the fuel injection axis; in other words, the fuel flow is central. The fuel flow 12 exits the fuel injection channel 10 at the fuel outlet 19.Before exiting the fuel injection channel 10, the fuel flow 12 is accelerated by the fuel venturi. The fuel flow 12 then enters the fuel mixture channel 30 at the fuel mixture inlet 31.

[0093] The combustion air channel 20 has a combustion air inlet 21 and a combustion air outlet 19. The combustion air inlet 21 is supplied with pressurized air by the compressor 102. The combustion air channel 20 is tubular and extends coaxially with the fuel injection channel 10 (around the fuel injection channel 10), particularly at the combustion air outlet 29. The combustion air channel 20 is internally delimited by the fuel injection wall 14, which separates the combustion air channel 20 from the fuel injection channel 10. The combustion air channel 20 is externally delimited by a combustion air wall 24. The combustion air channel 20 communicates with the fuel mixture channel 30 via the combustion air outlet 29 and the fuel mixture inlet. 31.

[0094] The combustion air channel 20 guides a combustion air flow 22 extending substantially along the direction of the fuel injection axis Y, coaxially with the fuel flow 12. The combustion air flow 22 exits the combustion air channel 20 at the combustion air outlet 29 and enters the fuel mixture channel 30 at the fuel mixture inlet 31. In the first embodiment, as illustrated in [Fig.2], the longitudinal axis X extends in line with the fuel injection axis Y.

[0095] The fuel flow 12 and the combustion air flow 22 mix in the fuel mixing channel 30. The fuel flow 12 at the fuel outlet 19 preferably reaches a speed between 0.4 Mach and 1 Mach, thanks to a fuel pressure drop of between 30% and 50%, preferably between 35% and 45%. The fuel pressure drop can be determined by measuring the pressure difference in the fuel injection channel 10 between the fuel inlet 11 and the fuel outlet 19, and dividing this pressure difference by the pressure measured at the fuel inlet 11.

[0096] Furthermore, the combustion air pressure drop between the combustion air inlet 21 and the combustion air outlet 29 is between 4% and 20%, preferably between 4% and 10%. The combustion air pressure drop can be determined by measuring the pressure difference in the combustion air duct 20 between the combustion air inlet 21 and the combustion air outlet 29, and dividing this pressure difference by the pressure at the combustion air inlet 21.

[0097] The injection assembly 70 has a pressure drop ratio equal to the combustion air pressure drop divided by the injection air pressure drop. The pressure drop ratio is preferably between 3 and 10.

[0098] Fuel pressure drop and combustion air pressure drop, in particular the ratio between fuel pressure drop and combustion air pressure drop (in other words the pressure drop ratio) are important to ensure optimal performance and minimum energy consumption.

[0099] Pressure losses correspond to energy losses caused by friction, changes in direction or cross-section, turbulence, and other obstacles to fluid movement. These various elements can be addressed during the design of the injection assembly 70 in order to obtain the desired pressure losses.

[0100] The change in cross-section due to the combustion throat 17 creates a pressure drop. Furthermore, when gaseous hydrogen flows through the fuel injection channel and when combustion air flows through the combustion air channel, friction with the walls creates pressure drops. In particular, the roughness of the walls can be adjusted to vary the frictional pressure drop. It is also possible, for example, to modify the pressure drop by the presence of obstacles or asperities in the combustion air channel 20, particularly on the walls of the combustion air channel.

[0101] Given the high velocity of the fuel flow 12 at the outlet of the fuel injection channel 10, the combustion air flow 22 is drawn in and then mixed with the fuel flow 12 in the fuel mixing channel 30. The fuel mixing channel 30 includes a fuel mixing venturi near the fuel mixing inlet 31. The fuel mixing venturi comprises, successively from the upstream portion 2 to the downstream portion 4, a converging mixing portion 36, a fuel mixing throat 37, and a diverging mixing portion 38. The converging mixing portion 36 is substantially conical and adjacent to the throat of fuel mixture 37 and the divergent portion of mixture 38 is substantially conical and attached to the neck of fuel mixture 37. In the embodiment illustrated in [Fig.2], the venturi of fuel mixture is integrated in projection inside the wall of fuel mixture 34.

[0102] A mixing auger 35 is preferably disposed in the mixing channel 30 between the fuel mixing venturi and the fuel mixing outlet 39, in order to rotate the fuel mixing flow 32 around the longitudinal axis X at the same time as the fuel mixing flow 32 moves from the upstream part 2 to the downstream part 4 along the direction of the longitudinal axis X.

[0103] The fuel (hydrogen) may have a temperature close to 300K at the fuel outlet 19 or a lower temperature (preferably between 200K and 250K), in order to cool the walls of the fuel mixing channel 30, the walls of the fuel mixing channel 30 being likely to be heated in particular by the combustion of the fuel mixing flow 32 in the combustion chamber 90.

[0104] Injecting hydrogen at a low temperature (preferably between 200K and 250K) reduces the production of nitrogen oxide during the combustion of the rich fuel mixture stream 32 in the combustion chamber 90.

[0105] The external air channel 40 extends from the upstream portion 2 to the downstream portion 4 along the longitudinal axis X, between an external air inlet 41 and an external air outlet 49. The external air inlet 41 is supplied with pressurized air by the compressor 102. The primary air circuit 108 splits between the combustion air channel 20 and the external air channel 40 at the combustion air inlet 21 and the external air inlet 41. The external air channel 40 is substantially tubular and extends coaxially with the longitudinal axis X. The external air channel 40 extends around the combustion air channel 20 and is separated from the combustion air channel 20 by the combustion air wall 24. The external air channel 40 extends around the fuel mixture channel 30 and is separated from the channel. fuel mixture 30 through the fuel mixture wall 34.The fuel mixture wall 34 extends in line with the combustion air wall 24, so that the combustion air wall 24 and the fuel mixture wall 34 form two successive portions of a single, substantially tubular wall. The external air channel 40 communicates with the combustion chamber 90 at the external air outlet 49 in order to supply the combustion chamber 90 with an external airflow 42 extending around the fuel mixture flow 32.

[0106] Preferably, a portion of the external air channel 40, forming a diffuser along the direction of the external airflow 42, is present at the external air outlet 49. In a particular embodiment, the diffusion of the external airflow 42 can be achieved by a section diverging downstream of the external air channel 40 at the outlet. external air 49. Other forms of the external air channel 40 at the external air outlet 49 would still be possible as illustrated in particular in document WO2023 / 057722A1.

[0107] An external air auger 45 is preferably disposed in the external channel 40, so as to rotate the external airflow 42 around the longitudinal axis X at the same time as the external airflow 42 moves from the upstream part 2 to the downstream part 4 along the direction of the longitudinal axis X. In other words, the external airflow 42 has a helical movement along the longitudinal axis X between the external air auger 45 and the combustion chamber 90.

[0108] The fuel mixture stream 32 is rich; preferably, the fuel mixture stream 32 has a ratio between the fuel stream 12 and the combustion air stream 22 that includes at least 10% excess fuel (dihydrogen) relative to the combustion air stream 22 so that all the dihydrogen is burned by the first combustion 92 (richness greater than or equal to 1.1). The portion of fuel (dihydrogen) not burned by the first combustion 92 is burned in the combustion chamber 90 with the external air stream 42, creating the second combustion 94. The flame of the first combustion 92 forms a first dome, and the flame of the second combustion 94 forms a second dome in the combustion chamber 90.

[0109] It will be noted that retaining tabs 25 extend in the combustion air channel 20 between the fuel injection wall 14 and the combustion air wall 24. The retaining tabs 25 are distributed around the fuel injection axis Y and are in the form of thin plates extending radially to the fuel injection axis Y, in order to minimize their effect on the combustion air flow 22.

[0110] The second embodiment illustrated in [Fig. 3] differs from the first embodiment illustrated in [Fig. 2] in one aspect in that the combustion device 1 comprises a flap 28 located at the combustion air channel 20. The flap 28 is movable between a first position (shown as a solid line) and a second position (shown as a dashed line) in order to vary the cross-section of the combustion air channel 20 between a first cross-section and a second cross-section smaller than the first, so that the combustion air flow 22 can be adjusted. Of course, the flap 28 can be arranged in many other positions between the first and second positions, in order to adjust the combustion air flow 22 more precisely. The flap 28 is preferably movable in translation along the direction of the fuel injection axis Y, as illustrated by the double arrow 27.In the illustrated embodiment, flap 28 has a tubular shape.

[0111] The second embodiment illustrated in [Fig. 3] differs from the first embodiment illustrated in [Fig. 2] according to a second aspect independent of the first aspect and which will now be detailed below. The combustion device 1 further comprises an internal air channel 50 and through channels 53.

[0112] The internal air channel 50 extends along the longitudinal axis X; in other words, the internal air channel 50 is central. The internal channel 50 is delimited (externally) by an internal air wall 54. The internal air wall 54 has a portion 54a of substantially conical shape at the internal air inlet 51. The internal air channel 50 extends along the longitudinal direction X between an internal air inlet 51 and an internal air outlet 59.

[0113] The fuel mixing channel 30 comprises successively a first portion 30a and a second portion 30b. The first portion 30a of the fuel mixing channel 30 extends from the fuel mixing inlet 31 to an upstream end of the internal air wall 54. The first portion 30a of the fuel mixing channel 30 has a cylindrical shape of revolution; therefore, the first portion 30a of the fuel mixing channel 30 extends along the longitudinal axis X, in other words, the first portion 30a of the fuel mixing channel 30 is central. The internal air channel 50 extends coaxially with the second portion 30b of the fuel mixing channel 30. The internal air channel 50 is surrounded by the second portion 30b of the fuel mixing channel 30 and separated from the fuel mixing channel 30 by the internal air wall 54.The second portion 30b of the fuel mixing channel 30 has a substantially tubular shape with an annular cross-section.

[0114] The through channels 53 each extend between a through air inlet 53a and a through air outlet 53b. The through air outlet 53b communicates with the internal air inlet 51, in order to supply the internal air channel 50 with an internal airflow 52 passing through the through channels 53. The internal air channel 50 communicates with the combustion chamber 90 at the internal air outlet 59, in order to supply the combustion chamber 90 with the internal airflow 52.

[0115] There is a heat exchange between the internal airflow 52 circulating in the through channels 53, inside the fins 55, and the fuel mixture flow 32 circulating in the fuel mixture channel 30, outside the fins 55. The fuel mixture flow 32 is heated by the internal airflow 52.

[0116] Preferably, a portion of the internal air channel 50 forming a diffuser along the direction of the internal airflow 52 is present at the internal air outlet 59. In a particular embodiment, the diffusion of the internal airflow 52 can be achieved by a section diverging downstream of the internal air channel 50 at the internal air outlet 59. Other shapes of the internal air channel 50 at the internal air outlet 59 would also be possible, as illustrated in particular in document WO2023 / 057722A1.

[0117] One, the other or both of the external air channel 40 at the external outlet 49 and the internal air channel 50 at the internal air outlet 59 may have a divergent section.

[0118] The internal air wall 54 is preferably tapered at the internal air outlet 59 to reduce the presence of recirculation vortices in the combustion chamber 90 near the internal air wall 54 and thus prevent the flame from catching on it.

[0119] The combustion device 1 includes an intermediate channel 60 extending along the longitudinal axis X between an intermediate air inlet 61 and an intermediate air outlet 69. The intermediate air inlet 61 is supplied with pressurized air by the compressor 102. The primary air circuit 108 splits between the combustion air channel 20 and the intermediate air channel 60 at the combustion air inlet 21 and the intermediate air inlet 61. Thus, an intermediate airflow 62 circulates in the intermediate air channel 60 between the intermediate air inlet 61 and the intermediate air outlet 69. The intermediate channel 60 is substantially tubular, circular in cross-section, and extends coaxially with the longitudinal axis X.The intermediate channel 60 extends around the fuel mixture channel 30 (essentially around the first portion 30a of the fuel mixture channel 30) and is separated from the fuel mixture channel 30 by the fuel mixture wall 34. The intermediate air channel 60 is delimited (externally) by a tubular intermediate air wall 64. The external air wall 44 extends in line with the intermediate air wall 64, such that the intermediate air wall 64 and the external air wall 44 form two successive portions of a single wall. The intermediate airflow 62 splits into the external airflow 42 and the internal airflow 52 at the external air inlet 41 and the through air inlets 53a. Alternatively, the intermediate air channel 60 could be replaced by a radial supply of pressurized air from the compressor 102 from the external air inlet 41 and the through air inlets 53a.

[0120] More specifically in the second embodiment, the combustion device 1 further comprises a plurality of fins 55. The fins 55 extend in the fuel mixture channel 30 between the fuel mixture wall 34 and the internal air wall 54. Each of the fins 55 contains one of the through channels 53.

[0121] The fins 55 are rigidly fixed to the fuel mixture wall 34 and to the internal air wall 54, in order to hold the internal wall 54.

[0122] The fins 55 are regularly distributed around the longitudinal axis X and are inclined with respect to the longitudinal axis X, in order to rotate the flow of fuel mixture 32 around the longitudinal axis X. Thus, the fins 55 fill the same function as the fuel mixture auger 35 in the first embodiment.

[0123] Thus, the fuel mixture channel 30 extends around the internal air channel 50 at the fuel mixture outlet 39 in order to supply the combustion chamber 90 with the tubular fuel mixture flow 32 surrounding the internal air flow 52. The fuel mixture flow 32 is burned in the combustion chamber 90 creating a first combustion represented by the substantially tubular first combustion flame 92.

[0124] The portion of fuel (dihydrogen) which is not burned by the first combustion 92 is burned in the combustion chamber 90, on the one hand with the external air flow 42 and on the other hand with the internal air flow 52, ​​creating the second combustion 94 represented by the second combustion flame 94 which is also substantially tubular in shape.

[0125] The variant embodiment of the second embodiment illustrated in Figures 4 and 5 differs essentially from the second embodiment illustrated in [Fig.3] in that the fuel injection axis Y has an angle α with respect to the longitudinal axis X, as illustrated in [Fig.4].

[0126] The angle a can be between 30 degrees and 90 degrees. In the embodiment illustrated in Figures 4 and 5, the angle a formed between the fuel injection axis Y and the longitudinal axis X is equal to 90 degrees.

[0127] The fuel mixture wall 34 has a fuel mixture passage 33. The fuel mixture venturi 30 comprising the convergent portion of mixture 36, the fuel mixture throat 37 and the divergent portion of mixture 38 is disposed substantially at the level of the fuel mixture passage 33, preferably the fuel mixture throat 37 and the divergent portion of mixture 38 are disposed substantially at the level of the fuel mixture passage 33.

[0128] As illustrated in [Fig. 5], the fuel injection axis Y and the longitudinal axis X are not concurrent. The fuel flow 12 and the fuel mixture flow 22 are directed towards the fuel mixture wall, so that the fuel mixture flow 32 tends to rotate around the longitudinal axis X. The fuel mixture flow 32 also tends to flow towards the combustion chamber 90 by pressure difference, so that the fuel mixture flow 30 has a helical motion around the elongation axis X.

[0129] The variant of the second embodiment illustrated in Figures 4 and 5 differs from the second embodiment illustrated in [Fig. 3] in another aspect, independent of the aforementioned aspect, in that the external air inlet 41 and the internal air inlet 51, supplied by the compressor 102, are separated from each other. Furthermore, the external air channel 40 is fed radially. Such a variant could, in particular, This can be applied to either the first or second embodiment, regardless of other differences between these embodiments and the variant of the second embodiment. Furthermore, an external air auger 45 is disposed at the external air inlet 41 to impart a helical motion to the external airflow 42 along the longitudinal axis. In the illustrated embodiment, upstream of the external air auger 45, the airflow is radial, and downstream of the external air auger 45, the external airflow 42 is axial. Alternatively, other configurations could be provided. In particular, downstream of the external air auger, the airflow could continue to extend radially along the longitudinal axis X for a (short) portion before extending along the longitudinal axis X.

[0130] Of course, disclosure is in no way limited to the embodiment described by way of illustration, which is not intended to be limiting. For example, the combustion air channel could be different and include one or more annular or axial spirals. Reference may be made, in particular, to document FR 2 208 857 A1 for further details on this subject.

Claims

1. Demands Injection assembly (70) for an aircraft turbomachine, the injection assembly (70) having a longitudinal axis (X) and extending between an upstream part (2) and a downstream part (4), the injection assembly (70) comprising: a fuel mixing channel (30), the fuel mixing channel (30) extending along the longitudinal axis (X), the fuel mixing channel (30) has a fuel mixing inlet (31) and a fuel mixing outlet (39), the fuel mixing channel (30) is intended to communicate with a combustion chamber (90) at the fuel mixing outlet (39) in order to supply the combustion chamber (90) with a fuel mixing flow (32), an external air channel (40), the external air channel (40) has an external air inlet (41) and an external air outlet (49), the external air channel (40) extends around the fuel mixture channel (30) and is intended to communicate with the combustion chamber (90) at the external air outlet (49) in order to supply the combustion chamber (90) with an external airflow (42) extending around the fuel mixture flow (32), a gaseous fuel injection device (8), the gaseous fuel injection device (8) includes a fuel injection channel (10) having a fuel inlet (11) and a fuel outlet (19), the fuel injection channel (10) includes a settling cavity (15) and the fuel injection channel (10) communicates with the fuel mixture channel (30) via the fuel outlet (19) and the fuel mixture inlet (31), and a combustion air channel (20), the combustion air channel (20) has a combustion air inlet (21) and a combustion air outlet (29), the combustion air channel (20) extends coaxially with the fuel injection channel (10) at the combustion air outlet (29) and communicates with the fuel mixture channel (30) via the combustion air outlet (29) and the fuel mixture inlet (31), in which: the fuel injection channel (10) includes a fuel throat (17) near the fuel outlet (19), the gaseous fuel injection channel (8) is configured to create a fuel pressure drop between the fuel inlet (11) and the fuel outlet (19), the combustion air channel (19) is configured to create a combustion air pressure drop between the combustion air inlet (21) and the combustion air outlet (29), the injection assembly (70) has a pressure drop ratio equal to the ratio between the fuel pressure drop and the combustion air pressure drop, the pressure drop ratio being between 3 and 10.

2. Injection assembly (70) according to claim 1 in which the fuel pressure drop is between 30% and 50%, preferably between 35% and 45%.

3. Injection assembly (70) according to any one of the preceding claims wherein the combustion air pressure drop is between 4% and 20%, preferably between 4% and 10%.

4. Injection assembly (70) according to any one of the preceding claims wherein the fuel mixture channel (30) comprises a fuel mixture throat (37) in close proximity to the fuel mixture inlet (31).

5. Injection assembly (70) according to any one of the preceding claims wherein the injection assembly (70) comprises a flap (28) in the combustion air channel (20), the flap (28) is movable between a first position and a second position in order to vary the cross-section of the combustion air channel (20) between a first section and a second section.

6. Injection assembly (70) according to any one of the preceding claims wherein the injection assembly (70) comprises an internal air channel (50), the internal air channel (50) extends along the longitudinal direction (X), coaxially with the fuel mixture channel (30) and has an internal air outlet (59), the fuel mixture channel (30) extends around the internal air channel (50) in order to supply the combustion chamber (90) at the level of the internal air outlet (59) with an internal air flow (52) surrounded by the fuel mixture flow (32).

7. Injection assembly (70) according to the preceding claim, wherein: The internal air channel (50) has an internal air inlet (51), the fuel mixture channel (30) is externally delimited by a fuel mixture wall (34), the internal air channel (50) is externally delimited by an internal air wall (54), and the injection assembly (70) comprises a plurality of fins (55), the fins (55) extending into the fuel mixture channel (30) between the fuel mixture wall (34) and the internal air wall (54), each fin (55) enclosing a through channel (53) extending between a through air inlet (53a) and a through air outlet (53b), the through air outlet (53b) communicating with the internal air inlet (51), in order to supply the internal air channel (50) with an internal airflow (52) passing through the crossing canals (53).

8. Injection assembly (70) according to the preceding claim in which the fins (55) are rigidly fixed to the fuel mixture wall (34) and to the internal air wall (54).

9. Injection assembly (70) according to any one of claims 7 or 8 wherein the fins (55) are regularly distributed around the longitudinal axis (X) and are inclined with respect to the longitudinal axis (X), in order to form a spiral rotating the flow of fuel mixture (32) around the longitudinal axis (X).

10. Injection assembly (70) according to any one of the preceding claims wherein the fuel injection channel (10) extends along a fuel injection axis (Y) and the longitudinal axis (X) is in the extension of the fuel injection axis (Y).

11. Injection assembly (70) according to any one of claims 1 to 6 wherein: the fuel injection channel (10) extends along a fuel injection axis (10) forming an angle (a) between 30 degrees and 90 degrees with respect to the longitudinal axis (X), the fuel mixture channel (30) is externally delimited by a fuel mixture wall (34), the fuel mixture wall (34) has a fuel mixture passage (33) and the fuel mixture inlet (31) is located at the fuel mixture passage (33).

12. Injection assembly (70) according to the preceding claim in which the fuel injection axis (Y) is perpendicular to the longitudinal axis (X).

13. Combustion device (1) comprising an injection assembly (70) according to any one of the preceding claims and a combustion chamber (90), the fuel mixture channel (30) communicating with the combustion chamber (90) at the fuel mixture outlet (39) and the external air channel (40) communicating with the combustion chamber (90) at the external air outlet (49).

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