Dihydrogen injection device for a combustion chamber of a turbine engine

Abstract

The invention relates to a dihydrogen injection device (2) for a combustion chamber (4) of a turbine engine (1), said device (2) having a main axis (Y) and comprising: • -an internal fluid circulation channel (10) centred on the main axis (Y), • -an external annular fluid circulation channel (12) centred on the main axis (Y) and extending around the internal channel (10), • -an internal swirler (14) housed in the internal channel (10), and • -an external annular swirler (16) housed in the external channel (12), • -an intermediate annular fluid circulation channel (18) centered on the main axis (Y) and extending between the internal and external channels (10, 12).

Description

[0001] DESCRIPTION

[0002] TITLE: TURBOMACHINE FOR AN AIRCRAFT

[0003] The present invention relates to turbomachines whose combustion chamber is supplied by separate injections of dihydrogen and air.

[0004] Technical background

[0005] The technical background includes, among other things, documents US-A1-2016 / 033132, US-A1-2010 / 212322, US-A1-2024 / 288168, US-A1-2008 / 163627, US-A1-2024 / 328617 and W0-A1-2020 / 259918.

[0006] The aeronautical sector faces major environmental challenges. The interest in using hydrogen combustion rather than kerosene is growing stronger because this hydrogen combustion would avoid carbon dioxide (CO2) emissions and carbon pollutants such as carbon monoxide, unburned hydrocarbons, and fine particles and smoke.

[0007] A principle of micro-mixing air-hydrogen burners is known. However, such burners do not guarantee the thermal resistance of a perforated wall or the absence of flashback in the hydrogen injection device. These burners also have a complex geometry. They are expensive to manufacture, have a high pressure drop, and are specific to a given combustion chamber design.

[0008] Indeed, the combustion of dihydrogen raises several issues. For example, there is a risk of flame rebound in the injection system for systems operating with mixtures of dihydrogen and air. This can damage the combustion chamber and / or the injection system and pose serious safety problems. Furthermore, the combustion of dihydrogen generates high thermal loads on the walls of this combustion chamber, which tends to reduce its lifespan. High gas temperatures and nitrogen oxide emissions are produced. These gas and nitrogen oxide emission temperatures are higher than those produced by kerosene flames of equivalent fuel-air ratio. This is, moreover, difficult to reconcile with current standards.

[0009] The Applicant proposed a solution to this problem in document FR-A1-3 127 987. Specifically, it proposed a hydrogen injection device for mounting on an annular bottom of an annular combustion chamber of a turbomachine. This device comprises an internal hydrogen circulation channel and an external annular channel for circulating a mixture containing at least air. The internal and external annular channels are coaxial, with an internal spiral housed within the internal channel and an external spiral housed within the external annular channel. A downstream end of the internal channel is positioned upstream, at a predetermined distance, from a downstream end of the external annular channel.

[0010] This device optimizes the mixing of dihydrogen and air. It also expands the operating range where the flame is detached.

[0011] The detached flame topology helps to limit thermal stresses on the injector, and therefore to increase its lifespan.

[0012] However, significant pressure drops (~10 to 15% of the generating pressure) are necessary to prevent backfires, ensure efficient mixing, and operate within a lean-fuel ratio range that emits little NOx (nitrogen oxides). This pressure drop level is considerably higher than that typically used in aircraft engines (~3-6%) and leads to increased specific fuel consumption. These losses therefore represent a major area for improvement in the development of H2 / Air injection systems for aircraft propulsion. These injection systems utilize late fuel injection to avoid any risk of backfires and inject a large quantity of air to create a rapid air-fuel mixture and burn under lean conditions.

[0013] Hydrogen (H2) is injected through the internal channel and set in rotation by the internal auger. Air is injected through the external channel and set in rotation by the external auger. This rotation of the two flows creates a central recirculation zone (IRZ), drawing hot gases back to the center of the injector and creating an aerodynamic blockage. This blockage reduces the effective cross-section of the H2 injection and deflects it radially outwards, which accelerates it and promotes mixing with the air.

[0014] One of the limitations highlighted during high-pressure bench tests is the high level of air velocity and therefore pressure loss required to obtain a detached flame due to the fact that this air velocity competes with the flame's upward velocity towards the H2 injection points, this flame propagating rapidly along the stoichiometric line.

[0015] It is therefore necessary to accelerate the flow to a level that allows it to counteract this flame speed, which entails the need for a high level of pressure drop.

[0016] Furthermore, aerodynamically stabilized flames from high-speed injection devices can trigger combustion instabilities at certain operating points or during transient regimes, making this type of injection device difficult to operate. This is a problem present in all aeronautical injection devices, but exacerbated by the use of hydrogen due to its compressibility at injection points and its very high reactivity. Moreover, current numerical simulation tools are not sufficiently mature to avoid the risk of these instabilities during the design phase in the case of air / hydrogen combustion. It is therefore necessary to design an injection device that ensures combustion in a low-NOx regime and does not exhibit combustion instabilities.In this sense, the Air / H2 combustion tests carried out so far have shown much lower acoustic activity, and better flame stability when operating with the flame attached to the injection device.

[0017] Finally, along the operating range of a turbomachine, a wide range of air-fuel mixtures can be achieved. This presents a risk of operating with stoichiometric air-fuel mixtures, which can lead to rapid flame flares and high NOx emissions. The present invention provides a solution to at least some of the problems of the prior art, in a simple, effective, and economical way.

[0018] Summary of the invention

[0019] According to a first aspect, the invention relates to a dihydrogen injection device for a turbomachine combustion chamber, particularly for aircraft, this device comprising a main shaft and comprising:

[0020] - an internal fluid circulation channel, the internal channel being centered on the main axis,

[0021] - an external annular fluid circulation channel, the external channel being centered on the main axis and extending around the internal channel,

[0022] - an internal spiral housed in the internal channel, and / or an external annular spiral housed in the external channel, characterized in that the device further comprises:

[0023] - an intermediate annular fluid circulation channel, the intermediate channel being centered on the main axis and extending between the internal and external channels, the intermediate channel being suitable for being supplied with dihydrogen, and in that the internal and external channels are suitable for being supplied with a mixture comprising at least air.

[0024] The present invention consists of significantly increasing the H2 / Air mixing surface area by adding a central air injection and injecting the H2 through a film located between the two air injections. The objective is both to accelerate mixing by increasing the Air / H2 exchange surface area and to increase the air passage cross-section to reduce the pressure drop at a constant air flow rate, thus maintaining a constant air-fuel ratio.

[0025] The invention thus proposes an injection device operating in lean direct injection (LDI). This operation involves a late injection of H2 to avoid any risk of backfire in the device and a rapid mixing for lean combustion.

[0026] As will be described in more detail below, the present invention further proposes a geometric optimization of the air and H2 channels, and of the air / H2 separator to eliminate areas of low air velocity at the level of the air / H2 separator, and to maximize the air velocity at the mixing zone.

[0027] According to a second aspect, the invention relates to an injection device as described above and further comprising a flame holder at an axial end downstream of the intermediate channel (relative to the direction of fluid flow in the channels).

[0028] The invention thus consists of obtaining an attached flame while maintaining a rapid air-fuel mixture in order to burn in a low-NOx combustion regime. This injection device is therefore designed to maintain LDI-type injection while exhibiting an attached flame. The objective is both to accelerate the mixture by injecting dihydrogen directly into the air channels and to attach the flame using a flame stabilizer. Thermal issues at the wall at the point of flame attachment can be addressed with dihydrogen impact cooling.

[0029] According to a third aspect, the invention relates to an injection device as described above, wherein the intermediate channel is adapted to be supplied with dihydrogen to inject dihydrogen at a downstream axial end of the intermediate channel. The injection device further comprises dihydrogen injection holes in the external channel, upstream of this downstream axial end.

[0030] The invention consists of significantly increasing the H2 / Air mixing surface area by injecting a portion of the hydrogen upstream of the injector outlet to allow the mixture to establish itself. Thus, part of the H2 is injected using a premixed injection method, and the remainder is injected using a liquid direct injection (LDI) method. Furthermore, the H2 / Air premix concentration in the external air stream is kept below the flammability limits to prevent any risk of flame flare-up.

[0031] In general, a helix allows a flow to be rotated. A helix may include a helical part with a suitable helix pitch. This helix pitch is configured to define the flame position at the outlet of the injection device 2, to minimize pollutant emissions and define the thermal conductivity of the injection device. This helical part rotates the fluid flow with a rotation rate characterized by a dimensionless number S.

[0032] The device according to the invention may comprise one or more of the following features, taken individually or in combination with each other:

[0033] - the device includes an internal annular wall which separates the internal canal from the intermediate canal, and which includes a downstream annular edge which forms an internal annular separator;

[0034] - the device includes an intermediate annular wall which separates the intermediate canal from the external canal, and which includes a downstream annular edge which forms an external annular separator;

[0035] - the external separator is located further downstream than the internal separator with respect to the direction of fluid flow in the channels;

[0036] - the intermediate wall has a radial thickness which decreases from upstream to downstream with respect to the direction of fluid flow in the external channel; - the device includes an external annular wall which externally delimits the external channel, and which includes a free downstream annular edge;

[0037] - the free edge of the outer wall is located further downstream than the outer separator with respect to the direction of fluid flow in the channels;

[0038] - the eint / Dint ratio is between 0.02 and 0.5, and / or the eext / Dext ratio is between 0.02 and 0.5, and / or the Dext / Dint ratio is between

[0039] 1.25 and 6, and / or the hnt / Dint ratio is between 0.25 and 3, and / or the lext / Dext ratio is between 0.25 and 3, and / or the Rint / Dint ratio is between 0.05 and 0.5, and / or the Rext / Dext ratio is between 0.05 and 0.5, with: eint the radial thickness of the inner wall, eext the radial thickness of the outer wall,

[0040] Dint is the internal diameter of the internal canal,

[0041] Dext is the internal diameter of the external canal, lint is the length of the internal wall at the exit of the internal spiral, lext is the length of the intermediate wall at the exit of the internal spiral, Rint is the axial distance between the downstream edge of the internal wall and the downstream edge of the intermediate wall.

[0042] Rext is the axial distance between the downstream edge of the intermediate wall and the downstream edge of the external wall;

[0043] - the inner wall comprises an outer surface which converges downstream with a first angle of inclination, and the intermediate wall comprises an inner surface which converges downstream with a second angle of inclination, the second angle of inclination being greater than the first angle of inclination so that the intermediate channel has a passage cross-section which decreases from upstream to downstream with respect to the direction of flow of the fluids in the channels;

[0044] - at least one of the annular walls is convergent, or convergent then divergent, or divergent; - the downstream edges of the internal and intermediate walls are free and radially apart from each other;

[0045] - the downstream edges of the internal and intermediate walls are connected together by an annular bottom wall which includes fluid injection orifices;

[0046] - the twist of the internal channel imposes on the fluid a rotation rate between 0.4 and 2, and / or the twist of the external channel imposes on the fluid a rotation rate between 0.2 and 1.2;

[0047] - the intermediate channel is devoid of twists;

[0048] - the intermediate canal includes an annular spiral;

[0049] - the device includes an internal annular wall which separates the internal canal from the intermediate canal, and which includes a downstream annular edge;

[0050] - the device includes an intermediate annular wall which separates the intermediate canal from the external canal, and which includes a downstream annular edge.

[0051] - the downstream edges of the internal and intermediate walls together form the said flame catch;

[0052] - the downstream edges of the internal and intermediate walls are connected together by an annular bottom wall;

[0053] - the bottom annular wall includes at least one annular row of fluid injection orifices, and / or at least one annular fluid injection slot;

[0054] - the bottom annular wall has a thickness or transverse dimension measured in a plane perpendicular to the Y axis, which is greater than a maximum thickness or transverse dimension of the intermediate channel measured in a plane perpendicular to the Y axis;

[0055] - the e / Dext ratio is between 0.04 and 0.5, and / or the Dext / Dint ratio is between 1.25 and 6, and / or the hnt / Dint ratio is between 0.25 and 3, and / or the lext / Dext ratio is between 0.25 and 3, with: e the thickness or the transverse dimension of the flame holder 40,

[0056] The internal diameter of the internal channel is 10.

[0057] Dext the internal diameter of the external channel 12, lint the length of the internal wall 20 at the exit of the internal spiral 14; lext the length of the intermediate wall 26 at the exit of the internal spiral 14;

[0058] - at least one of the downstream edges of the internal and intermediate walls includes a projecting annular beak;

[0059] - at least one of the downstream edges of the internal and intermediate walls includes a bevel formed by a frustoconical surface;

[0060] - the device includes an external annular wall which externally delimits the external channel, and which includes a downstream annular edge which is free;

[0061] - the free edge of the external wall is located further downstream than the downstream edges of the internal and intermediate walls;

[0062] - at least one of the annular walls is convergent, or convergent then divergent, or divergent;

[0063] - the twist of the internal channel imposes on the fluid a rotation rate between 0.4 and 2, and / or the twist of the external channel imposes on the fluid a rotation rate between 0.2 and 1.2;

[0064] - the device includes an internal annular wall which separates the internal canal from the intermediate canal, and which includes a downstream annular edge;

[0065] - the device includes an intermediate annular wall which separates the intermediate canal from the external canal, and which includes a downstream annular edge.

[0066] - the downstream edge of the intermediate wall is located further downstream than the downstream edge of the internal wall with respect to the direction of fluid flow in the channels;

[0067] - at least part of said injection holes are formed in the intermediate wall;

[0068] - the device includes an external annular wall which externally delimits the external channel, and which includes a downstream annular edge which is free;

[0069] - the free edge of the outer wall is located further downstream than the downstream edge of the intermediate wall with respect to the direction of fluid flow in the channels; - at least a portion of said injection holes are formed in the outer wall;

[0070] - at least part of said injection holes open into the external spiral, or downstream of the external spiral;

[0071] - the device further includes at least one obstacle which extends transversely inside the intermediate channel, said injection holes being located upstream of this obstacle;

[0072] - the eint / Dint ratio is between 0.02 and 0.5, and / or the eext / Dext ratio is between 0.02 and 0.5, and / or the Dext / Dint ratio is between

[0073] 1.25 and 6, and / or the hnt / Dint ratio is between 0.25 and 3, and / or the lext / Dext ratio is between 0.25 and 3, and / or the Rint / dint ratio is between 0.05 and 0.5, and / or the Rext / dext ratio is between 0.05 and 0.5, with: eint the radial thickness of the inner wall, eext the radial thickness of the outer wall,

[0074] Dint is the internal diameter of the internal canal,

[0075] Dext is the internal diameter of the external canal, lint is the length of the internal wall at the exit of the internal spiral, lext is the length of the intermediate wall at the exit of the internal spiral, Rint is the axial distance between the downstream edge of the internal wall and the downstream edge of the intermediate wall, and

[0076] Rext is the axial distance between the downstream edge of the intermediate wall and the downstream edge of the external wall;

[0077] - the twist of the internal channel imposes on the fluid a rotation rate between 0.4 and 2, and / or the twist of the external channel imposes on the fluid a rotation rate between 0.2 and 1.2;

[0078] - the intermediate channel is devoid of twists;

[0079] - the intermediate canal includes an annular spiral.

[0080] The features of the various aspects of the invention can be combined. The present invention also relates to a combustion chamber for a turbomachine, particularly for aircraft, comprising devices as described above.

[0081] The present invention also relates to a turbomachine, in particular for aircraft, comprising a combustion chamber as described above.

[0082] Brief description of the figures

[0083] Other features and advantages will become apparent from the following description of a non-limiting embodiment of the invention with reference to the accompanying drawings in which:

[0084] [Fig. 1] shows a turbomachine comprising a dihydrogen injection device arranged in an annular bottom of an annular combustion chamber in three configurations;

[0085] [Fig.2] Figure 2 is a very schematic view of an injection device according to the invention;

[0086] [Fig.3] Figure 3 is another very schematic view of an injection device according to the invention, and shows dimensional parameters of this device;

[0087] [Fig.4] Figure 4 is a very schematic view of part of an injection device according to the invention, and more particularly of an intermediate or external channel;

[0088] [Fig.5] Figure 5 represents in a very schematic way several variants of the embodiment of injection devices according to the invention, the devices differing from each other by the shape of the channels or assemblies of channels / air spirals;

[0089] [Fig.6] Figure 6 schematically represents several variants of the injection devices according to the invention, the devices differing from each other by the end of the intermediate H2 injection channel; [Fig.7] Figure 7 schematically represents other variants of the injection devices according to the invention, the devices differing from each other by the end of the intermediate H2 injection channel;

[0090] [Fig.8] Figure 8 is a very schematic view of another injection device according to the invention;

[0091] [Fig.9] Figure 9 is a very schematic view of an injection device according to the invention, and shows dimensional parameters of this device;

[0092] [Fig.10] Figure 10 represents in a very schematic way several variants of the embodiment of injection devices according to the invention, the devices differing from each other by the shape of the channels or assemblies of channels / air spirals;

[0093] [Fig.11] Figure 11 represents in a very schematic way several variants of the realization of flame holders for injection devices according to the invention;

[0094] [Fig.12] Figure 12 is a very schematic view of another injection device according to the invention;

[0095] [Fig.13] Figure 13 is a very schematic view of an injection device according to the invention, and shows dimensional parameters of this device;

[0096] [Fig.14] Figure 14 represents in a very schematic way several variants of the embodiment of injection devices according to the invention, the devices differing from each other by the shape of the channels or assemblies of channels / air spirals;

[0097] [Fig.15] Figure 15 represents in a very schematic way several variants of embodiment of injection devices according to the invention, the devices differing from each other by the end of the intermediate H2 injection channel;

[0098] [Fig.16] Figure 16 represents in a very schematic way other variants of embodiments of injection devices according to the invention, the devices differing from each other by the end of the intermediate H2 injection channel; [Fig.17] Figure 17 represents in a very schematic way other variants of embodiments of injection devices according to the invention;

[0099] [Fig.18] Figure 18 represents in a very schematic way several variants of the embodiment of injection devices according to the invention;

[0100] [Fig.19] Figure 19 represents in a very schematic way another variant of the embodiment of an injection device according to the invention;

[0101] [Fig. 20] Figure 20 schematically represents another embodiment of an injection device according to the invention; and

[0102] [Fig.21] Figure 21 represents in a very schematic way other variants of embodiment of an injection device according to the invention.

[0103] Detailed description of the invention

[0104] The present invention relates to a dihydrogen injection device 2 intended to be mounted on an annular bottom of an annular combustion chamber 4 of a turbomachine.

[0105] This hydrogen injection device 2 is used in a hydrogen-lean combustion configuration such that flame temperatures and nitrogen oxide formation are reduced.

[0106] An injection system is said to be lean when there is excess oxygen compared to a stoichiometric combustion of hydrogen and air, and rich when there is excess hydrogen compared to this stoichiometric combustion. Stoichiometric combustion is defined as combustion in which the correct number of hydrogen and oxygen atoms are present to consume all the fuel, leaving only water as a byproduct. The present invention falls within the context of lean hydrogen combustion.

[0107] As illustrated in Figure 1, three possible configurations of the dihydrogen 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 approximately along a longitudinal axis, with the bottom of the chamber located towards the front or upstream of the engine, called the direct chamber,

[0108] - either the combustion chamber is oriented substantially along a longitudinal axis, with the bottom of the chamber located towards the rear or downstream of the engine, called a reverse flow chamber as illustrated in figure 1,

[0109] - either the combustion chamber is transverse to the longitudinal axis X. In all cases, the hydrogen injection device 2 is located between the compressor and the high-pressure turbine, on the annular bottom of the annular combustion chamber 4 or on an external shell.

[0110] As illustrated in Figure 2, a dihydrogen injection device 2 according to the invention comprises a principal axis Y and includes:

[0111] - an internal fluid circulation channel 10, the internal channel 10 being centered on the principal axis Y,

[0112] - an external annular fluid circulation channel 12, the external channel 12 being centered on the principal axis Y and extending around the internal channel 10,

[0113] - an internal spiral 14 lodged in the internal canal 10 and / or an external annular spiral 16 lodged in the external canal 12, and

[0114] - an intermediate annular channel 18 for fluid circulation, the intermediate channel 18 being centered on the main axis Y and extending between the internal and external channels 10, 12.

[0115] The intermediate channel 18 is suitable for being supplied with dihydrogen (H2) and the internal and external channels 10, 12 are suitable for being supplied with a mixture comprising at least air (Air).

[0116] Advantageously, the twist 14 of the internal channel 10 imposes on the fluid a rotation rate S between 0.4 and 2.

[0117] Advantageously, the twist 16 of the external channel 12 imposes on the fluid a rotation rate S between 0.2 and 1.2.

[0118] The intermediate channel 18 is without a twist in the example of Figure 2. The device 2 includes an internal annular wall 20 which separates the internal channel 10 from the intermediate channel 18, and which includes a downstream annular edge 22 which forms an internal annular separator 24. This edge 22 can be free as is the case in Figure 2.

[0119] The device 2 includes an intermediate annular wall 26 which separates the intermediate canal 18 from the external canal 12, and which includes a downstream annular edge 27 which forms an external annular separator 28. This edge 27 can be free as is the case in figure 2. It can thus be seen in the figure that the free edges 22, 27 are at a radial distance from each other.

[0120] The external separator 28 is preferably located further downstream than the internal separator 24 with respect to the direction of fluid flow in the channels (see arrows).

[0121] Device 2 includes an external annular wall 30 which externally delimits the external channel 12, and which includes a downstream annular edge 32 which is free.

[0122] This free edge 32 of the external wall 30 is preferably located further downstream than the external separator 28 with respect to the direction of fluid flow in the channels.

[0123] The dimensional parameters of device 2 according to the invention can be optimized to limit any air separation and any harmful recirculation during operation.

[0124] As can be seen in Figure 3, the external diameter Dext of the external channel 12, and the radial thickness eext of the intermediate wall 26 decrease preferably with L, that is, from upstream to downstream along the Y axis.

[0125] The radial thickness of the downstream end of the inner wall 20 can be refined up to a limit imposed by the manufacturing means.

[0126] The distance Dext - (Dmid+2.e e xt) can decrease as a function of L. This decrease ensures that the air does not detach from the intermediate wall 26. The total length L of the injection device 2 is preferably chosen to limit the centrifugal effect of the air in the external channel 12 and the pressure losses.

[0127] The twist 14 of the internal channel 10 creates an internal recirculation zone and an aerodynamic blockage that accelerates the flow. This rotation takes advantage of the centrifugal force of the air to improve the air / fuel mixture. The position of the separator 24, set back from the separator 28, allows the first stage of air-fuel mixing to begin upstream of the second stage. This prevents the formation of a stoichiometric air-fuel line between the fuel and the air in the external channel 12 at the separator 28.

[0128] The rotation rates Sint and Sext of the internal and external channels 10, 12, are preferably defined by the equation below. These rotation rates correspond to a ratio of a tangential angular momentum and an axial angular momentum multiplied by the diameter of the channel in which the flow takes place.

[0129] [MATH1] with :

[0130] • S the turnover rate,

[0131] • p the density of the fluid,

[0132] • The tangential velocity of the fluid,

[0133] • Ux, the axial velocity of the fluid,

[0134] • rmin the minimum radius of the channel, n™ = 0 for the central channel, and

[0135] • Tmax is the maximum radius of the channel.

[0136] The ratios eint / Dint and eext / Dext can be between 0.02 and 0.5.

[0137] The Dext / Dint ratio can be between 1.25 and 6.

[0138] The hnt / Dint and lext / Dext ratios can be between 0.25 and 3.

[0139] The ratios Rint / Dint and Rext / Dext can be between 0.05 and 0.5, where: eint is the radial thickness of the inner wall (20), eext is the radial thickness of the outer wall (30).

[0140] The internal diameter of the internal channel is 10.

[0141] Dext the internal diameter of the external channel 12, lint the length of the internal wall 20 at the exit of the internal spiral 14, lext the length of the intermediate wall 26 at the exit of the internal spiral 14,

[0142] Rint the axial distance between the downstream edge 22 of the internal wall 20 and the downstream edge 27 of the intermediate wall 26,

[0143] Rext the axial distance between the downstream edge 27 of the intermediate wall 26 and the downstream edge 32 of the external wall 30.

[0144] Figure 4 shows an example of thinning the internal wall 20 from an eccentricity eo to a thickness e cc . The angle 0e represents the inclination of the intermediate wall 26, and in particular of an internal annular surface of this intermediate wall, and Pi represents the inclination of the internal wall 20 and in particular of an external annular surface of this internal wall 20.

[0145] The external surface of the internal wall 20 converges downstream with the first angle of inclination Pi, and the internal surface of the intermediate wall 26 converges downstream with the second angle of inclination p e .

[0146] The second angle of inclination p e is preferably greater than the first angle of inclination Pi so that the intermediate channel 18 has a passage cross-section which decreases from upstream to downstream with respect to the direction of fluid flow.

[0147] The refinement can be done on the side of the internal channel 10 as shown here, or on the contrary on the side of the external channel 12. The example proposed here constitutes the case where the angle Pi is high and is not conducive to creating an air separation.

[0148] This angle Pi is defined such that:

[0149] [MATH2] pi = tan- 1 ((eo-ecc) / Lint) Depending on the orientation and width of tendrils 14, 16, angle Pi and Lint, angle p ecan vary from 0 to 50°.

[0150] The difference between pe and pi can be in a range of 1 to 20°, in order to ensure a narrowing of the external channel to compensate for separation. The Lint length is minimized to limit the centrifugal effect of air in the external channel 12, while being long enough to dissipate the wake effects of the twists, thus avoiding low velocities above the separator.

[0151] In a particular embodiment of the invention, the following dimensioning rules are applied:

[0152] • Lint > 4 mm

[0153] • 50° > pe > 0°

[0154] • 20° > pe - pi > 1°

[0155] The variants illustrated in Figure 5 offer a dual advantage: limiting recirculation zones above the separators and maximizing air velocities in the mixing zones to lean the air / humidity mixture as quickly as possible.

[0156] The external channel variants 12, I, II. a, II. b, III. a, III. b, IV.a, IV. b, Va, can be implemented with a right internal channel 10, or not as in the variants Vb, VI. a, VI. b, VII. a, VII. b.

[0157] A first variant (I) can use a convergent / divergent external wall 30 to accelerate the airflow over the external separator 28 and then reopen the flow to improve the interaction between injectors in a combustion chamber. This divergent component of the external wall 30 can also facilitate the anchoring of the internal recirculation zone in the injection device.

[0158] Another variant II) can use diverging walls 26, 30, either straight according to sub-variant a), or convex according to sub-variant b). This variant aims to promote the anchoring of the internal recirculation zone in the injection device in order to maximize the anchoring of the internal recirculation zone in the injection device and the aerodynamic blocking accelerating the airflow.

[0159] A third variant (III) may use an internal surface of the intermediate wall 26 that is inclined towards the center of the injection device. Sub-variant III.b) may use a set of air-rotating spirals also inclined towards the center of the injection device to ensure that the air does not detach from the wall.

[0160] A fourth variant (IV) may use concave walls 26, 30 to prevent air from separating from the inner surface of the intermediate wall 26, while simultaneously reopening the flow outlet of the injection device to promote penetration of the internal recirculation zone into the injection device and increase aerodynamic blockage, thereby accelerating the central airflow. Sub-variant IV.b) uses an inclined channel and rotating spiral assembly.

[0161] A fifth variant V).b) can use a convex internal channel 10 to promote the sinking of the internal recirculation zone into the injection device and increase the aerodynamic blockage which accelerates the internal airflow.

[0162] A sixth variant VI) can use a diverging internal air channel, either straight according to variant VI. a), or concave according to variant VI. b) to limit the drop in the rotation rate given by equation [MATH1] in the internal channel 10.

[0163] A seventh variant (VII) may use a converging internal channel 10, either straight according to variant VII.a) or convex according to variant VII.b), to accelerate the airflow of the channel 10 before the Air / FL mixing zone. The variants illustrated in Figure 6.a) also allow for late H2 injection to avoid the risk of backfire, while still permitting rapid Air / H2 mixing for LDI (Lean Direct Injection) operation. Variants 1 to 4 in Figure 6.a) may add an additional slope to the walls 20, 26 forming the channel 18 for the H2, and / or modify the position of the internal and external separators 24, 28.

[0164] Variants 5 to 11 of Figure 6. a) propose several injection modes where the walls 20, 26 of the channel 18 for H2 are joined to form a separator through which the injection of H2 can be directed through injection orifices 34 which can take the form of holes, slits or diamonds.

[0165] The downstream edges 22 of the internal and intermediate walls 20, 26 are then connected together by a bottom annular wall 36 which includes fluid injection ports 34.

[0166] These orifices 34 can be distributed in one or more rows, and located at a distance from the end of the separator Hinj such that the ratio Hinj / I is between 0 and 0.5, with I being the minimum between hnt and leext. The orifices 34 can be directed towards the internal channel 10, the external channel 12 or parallel to the Y axis directly into the combustion chamber (see Figure 6.b).

[0167] All variants 1 to 12 shown in Figure 6. a) can be implemented with all air channel variants shown previously.

[0168] Examples are shown in Figure 7. a) which proposes the combination of variants 10 and 11 with a three-directional injection of H2.

[0169] Figures 7a, b) and c) present variants 8 with separator directed respectively towards the internal channel 10 and the external channel 12, and bidirectional injections of H2.

[0170] The first variant 1) of figure 6. a) can operate without axial withdrawal of the separators 24, 28, i.e. Rint=Rext.

[0171] In this variant, the rotation rate, given by equation [MATH1] of the internal airflow can be increased and can be between 0.6 and 2.0. The second variant 2) can use an end of internal channel 10 inclined towards the H2 injection to promote Air / FL mixing.

[0172] The third variant 3) can use an external channel end 12 inclined towards the H2 injection for the same reasons.

[0173] The fourth variant 4) can use an axial withdrawal of the external separator 28 greater than the axial withdrawal of the internal separator 24 in order to initiate the Air / H2 mixing upstream of the mixing stage between the H2 and the air of the internal channel 10.

[0174] The fifth variant (5) can use a straight bottom wall 36 with directed H2 injection towards the internal or external channel 10, 12, or both, to maximize shear with air and promote mixing. These injection methods can be coupled with straight injection to eliminate the recirculation zone downstream of the bottom wall 36 and prevent flame snagging.

[0175] The sixth variant (6) can use a beveled bottom wall 36 to minimize the recirculation zone downstream of the bottom wall 36. H2 injection can be directed towards the internal and / or external channel 10, 12 to maximize shear with air and promote mixing. The injection ports can be located on the bevel or upstream.

[0176] Within the framework of the present invention, a bevel can be considered as a frustoconical surface or an inclined annular surface, in particular centered on the Y axis.

[0177] A seventh variant 7) can use a doubly beveled bottom wall 36 to minimize the recirculation zone downstream of the bottom wall 36 and generate a local flow acceleration to prevent flame snagging. Directed H2 injection can be performed in one or both of the two air channels to maximize shear with the air and promote mixing. The H2 injection can be located directly below the bevel or further upstream.

[0178] The eighth variant (8) can use a double-beveled bottom wall (36) with a straight end plate. The double bevel allows for local acceleration of the airflow, as in variant (7), and also enables the use of an injection method towards the chamber. Directed H2 injections towards the air channels can also be added (Figures 7b and 7c).

[0179] The ninth variant (9) can use a straight bottom wall 36 with a bevel. H2 injection can be made towards the chamber or towards the air channels.

[0180] The tenth variant 10) can use a bottom wall 36 with a double bevel and straight plate in order to minimize the recirculation area downstream of the bottom wall 36. Injection ports can be placed towards one or both of the two air channels and / or towards the chamber.

[0181] The eleventh variant 11) can use a bottom wall 36 with a point, therefore with a double bevel, in order to minimize the recirculation area downstream of the bottom wall 36. Injection ports can be placed towards one or both of the two air channels.

[0182] Finally, the twelfth variant 12) can use a corrugated bottom wall 36 to maximize the Air / H2 mixing surface.

[0183] Figure 8 shows a variant in which the intermediate channel 18 includes an annular spiral 38. The H2 flow is thus set in rotation upstream of the injection by the spiral 38. This rotation can promote shearing with the air and / or the covering of the separator 28 by centrifugal effect in order to eliminate its recirculation zone induced by the separator 28.

[0184] Figure 9 illustrates a variant embodiment of a dihydrogen injection device 2 in which the elements already described above are designated by the same references.

[0185] The device in Figure 9 differs from that in Figure 2 in particular in that it also includes a flame catcher 40 at the downstream end of the intermediate channel 18. The intermediate channel 18 is thus designed to perform the flame catcher function.

[0186] Preferably, the downstream edges of the internal wall 20 and intermediate wall 26 are connected together by a bottom annular wall 36.

[0187] The bottom wall 36 preferably has a thickness e or transverse dimension measured in a plane perpendicular to the Y axis, which is greater than a thickness e' or maximum transverse dimension of the intermediate channel 18 measured in a plane perpendicular to the Y axis.

[0188] The bottom wall 36, added at the end of the intermediate channel 18, allows the creation of a small recirculation zone to attach the flame.

[0189] The thermal constraints imposed by the presence of the flame near the intermediate wall 16 are managed by the presence of cold dihydrogen on the other side of this wall 16.

[0190] This cooling can initially be achieved by impacting jet in the injection device, but can also be achieved by multi-perforations in variants where dihydrogen is also injected through the bottom wall 36 (see variants proposed below).

[0191] The bottom wall 36 can thus include at least one annular row of fluid injection orifices 34, and / or at least one annular fluid injection slot 35.

[0192] The dimensional parameters of device 2 according to the invention can be: The e / Dext ratio can be between 0.04 and 0.5.

[0193] The Dext / Dint ratio can be between 1.25 and 6.

[0194] The hnt / Dint and lext / Dext ratios can be between 0.25 and 3.

[0195] With: e the thickness or transverse dimension of the flame holder 40,

[0196] The internal diameter of the internal channel is 10.

[0197] Dext the internal diameter of the external channel 12, lint the length of the internal wall 20 at the exit of the internal spiral 14, lext the length of the intermediate wall 26 at the exit of the external spiral 16.

[0198] The variants illustrated in Figure 10 allow for maximizing air velocities in the mixing zones to lean out the air / h mixture as quickly as possible.

[0199] The external channel variants 12 I, II. a, II. b, III. a, III. b can be implemented with the right internal channel 10.

[0200] The first variant I) of Figure 10 can use a convergent / divergent outer wall 30 to accelerate the airflow over the intermediate wall 26, thereby improving the air-fuel mixture, and then open the flow to improve the interaction between injection devices in a combustion chamber. This divergent component of the outer wall can also facilitate the anchoring of the internal recirculation zone within the injection device.

[0201] The second variant II) can use an intermediate wall 26 that is convergent and therefore inclined towards the Y axis. The sub-variant II. b) can use a set of air rotation spirals also inclined towards the Y axis of the injection device to ensure that the air does not detach from the wall 26.

[0202] The third variant III) can use an external wall 12 with a convexly curved internal annular surface, and an intermediate wall 26 with a concavely curved external annular surface, in order to avoid the separation of air on the intermediate wall 26, while reopening the flow at the outlet of the injection device in order to promote the penetration of the internal recirculation zone into the injection device and increase the aerodynamic blockage which accelerates the central airflow.

[0203] Sub-variant III. b) uses an inclined channel and rotation screw assembly.

[0204] Figure 11 shows other embodiment variants in particular of the flame holder 40. The first variant 1) of Figure 11 presents a type of flame holder with an annular beak 44 projecting on the side of the internal channel 10 and an annular beak 42 on the side of the external channel 12.

[0205] The second variant 2) can use a straight edge for the internal channel 10 and a beak 42 for the external channel 12 in order to keep the recirculation zone downstream of the plate thus allowing the flame to catch.

[0206] The third variant (3) can use a diverging edge for the inner channel 10, a spoiler 42 for the outer channel 12, and a straight end plate. This configuration allows for local acceleration of the airflow and thus increases the air-fuel mixture.

[0207] In these three configurations, H2 can be injected into the air channels or into the chamber through the flame-holding plate. Lateral injections (towards the air channels) can be achieved using one or more rows of circular or other shaped orifices 34. Injection through the wall 36 or the plate can be achieved using circular injection orifices 34 (Figure 11b.a), orifices of any shape, or an annular slot 45 (Figure 11bb).

[0208] Another hydrogen injection variant is shown in Figure 12. This variant is based on a convergent bevel and is compatible with the different air channel variants and the different injection point variants shown previously.

[0209] This variant allows the flame to be attached without a deflector by relying on the separation of the flow from the external channel at the bevel, thus creating a recirculation zone. This recirculation, located downstream of the separator, ensures the flame is securely attached.

[0210] Figure 13 illustrates a variant embodiment of a dihydrogen injection device 2 in which the elements already described above are designated by the same references.

[0211] The device in Figure 13 differs from that in Figure 2 in particular in that it also includes hydrogen injection holes 46 in the external channel 12, which are located upstream of the downstream axial end of the intermediate channel 18.

[0212] At least part of said injection holes 46 can be formed in the intermediate wall 26 (figure 13 for example).

[0213] At least part of said injection holes 46 are formed in the outer wall 30 (figure 17. a for example).

[0214] Furthermore, at least part of said injection holes 46 may open into the inside of the external spiral 16 (figures 18, 19 and 21 for example), or downstream of the external spiral 16 (figure 13 for example).

[0215] Advantageously, the injection device 2 further includes at least one obstacle 48 which extends transversely inside the intermediate channel 18. The axial distance between an obstacle 48 and the outlet of the spiral 14 is denoted B in Figure 13.

[0216] The injection holes 46 are preferably located upstream of this obstacle 48.

[0217] The intermediate channel 18 is preferably designed to inject fuel via two different routes:

[0218] - a downstream injection (in the air swirl zone, see the following section for the different variants), which allows for a premix at the injector outlet, and

[0219] - an injection close to the injector outlet ensuring LDI injection.

[0220] This type of fuel distribution maximizes the air / hydrogen (H2) mixture. In addition to the spatial distribution of the fuel, the two-stage injection reduces the H2 injection rate and therefore the amount of H2 injected. This increases the air / H2 momentum ratio and can facilitate mixing. The fuel distribution developed in this injection system thus enables lean premixed combustion at very low temperatures and therefore low NOx emissions.

[0221] The distribution of dihydrogen can be active (two independent injection lines) or passive (distribution determined by the blockage in the H2 injection channel).

[0222] Regardless of the type of distribution, the ratio between the flow rate of H2 injected downstream for the premix and that injected in LDI can be limited by the following constraint: the richness of the hh / Air premix present in the external air stream is located below the flammability limits, to avoid any risk of flame rising.

[0223] The proposed variants are based on the same principle as the aforementioned proposal: a limitation of recirculation zones above the separators, and a maximization of air speeds at the mixing zones to deplete the Air / H2 mixture as quickly as possible.

[0224] The variants of the external channel 12 in Figure 14 are similar to that in Figure 5.

[0225] The comments concerning figure 5 therefore apply to the variants of figure 14.

[0226] Similarly, the embodiment variants of Figures 15 and 16 apply to the case of Figure 13, and the comments concerning Figures 5 and 6 apply to these variants.

[0227] The injection of hydrogen (H2) to create an air-fuel premix can be carried out via the air channel or the air vents. In the cases described above, the injection is made into the external vent. It is also possible to make this injection into the internal vent or both, as long as the premix preferably remains below the flammability limit.

[0228] The different variants associated with injection via the external air channel are presented in Figure 17.

[0229] The first two variants shown in Figure 17 involve active control of the H2 flow rate with two independent fuel lines. In this case, injection can be carried out through the outer wall 30 (Figure 17a), or along and through the intermediate wall 26 (Figure 17b). Finally, Figure 17c represents the variant in which the H2 distribution is dictated by the blockage located in the single injection channel. In this case, injection is carried out through the intermediate wall 26.

[0230] On the other hand, the variants associated with injection via the external air auger are presented in Figure 18. Injection via the auger blades avoids injection close to the walls. This method thus allows for injection perpendicular to the airflow with multiple injection points, thereby accelerating mixing.

[0231] The first two versions shown in Figure 18 involve active control of the H2 flow rate with two independent fuel lines. In this case, injection can be carried out in the spiral 16 through the outer wall 30, as in the version shown in Figure 18.a, or through the intermediate wall, as schematically shown in Figure 18.b. Finally, Figure 18.c presents the version in which the H2 distribution is dictated by the blockage located in the single injection channel. In this case, injection is carried out through the intermediate wall 26.

[0232] The H2 injected in LDI can be rotated either by adding the twist 38 (figure 19. a) or with the help of the obstacle 48 (figure 19. b), which can have a geometry that can rotate the H2 in the LDI injection.

[0233] The variant in Figure 20 is based on the combination of aspects of the invention illustrated in Figures 9 and 13, and proposes to inject part of the H2 upstream of the injection orifices 34 described previously to create an Air / H2 premix upstream of the combustion zone.

[0234] The objective is to reduce the combustion richness of the LDI zone, while avoiding any risk of flame rising into the air channels by requiring that the premix richness be below the flammability limit.

[0235] The distribution of dihydrogen can be active (two independent injection lines, Figure 21b) or passive (distribution determined by the blockage in the H2 injection channel, Figures 20, 21a and 21c). As long as the flammability limit criterion for the Air / H2 mixture is met, the Air / H2 premixing can be carried out in the external channel 12 and / or the internal channel 10. This injection can be made directly into the channel (Figure 20) or through the augers 12, 16 (Figure 21).

[0236] The invention thus proposes an improved device for injecting dihydrogen into a turbomachine combustion chamber, particularly in aircraft. The invention is based on the injection of dihydrogen located between two concentric air channels equipped with air-rotating augers. The air channels are advantageously designed to prevent airflow separation from the channel walls, minimize recirculation zones, and maximize the air / H2 mixing ratio.

[0237] The device according to the invention allows, in particular:

[0238] - to obtain aerodynamically stabilized flames (or detached flames, i.e., without contact with the injector) over a wide operating range,

[0239] - to achieve lean, partially premixed, low-NOx combustion, - to avoid any risk of flame rebound in the injection device

[0240] (flashback)

[0241] - etc.

Claims

1. DEMANDS 1. A dihydrogen injection device (2) for a combustion chamber (4) of a turbomachine (1), in particular an aircraft turbomachine, this device (2) comprising a main axis (Y) and comprising: - an internal fluid circulation channel (10), the internal channel (10) being centered on the main axis (Y), - an external annular fluid circulation channel (12), the external channel (12) being centered on the main axis (Y) and extending around the internal channel (10), - an internal spiral (14) lodged in the internal canal (10), and / or an external annular spiral (16) lodged in the external canal (12), - an intermediate annular fluid circulation channel (18), the intermediate channel (18) being centered on the main axis (Y) and extending between the internal and external channels (10, 12), the intermediate channel (18) being capable of being supplied with dihydrogen to inject dihydrogen at a downstream axial end of the intermediate channel (18), and the internal and external channels (10, 12) being capable of being supplied with a mixture comprising at least air, characterized in that the device (2) further comprises: - at least one obstacle (48) which extends transversely within the intermediate channel (18) and at an axial distance from the downstream axial end of the intermediate channel (18), and - hydrogen injection holes (46) in the external channel (12), upstream of this downstream axial end, and upstream of said at least one obstacle (48).

2. Device (2) according to claim 1, wherein it comprises an internal annular wall which separates the internal canal from the intermediate canal, and which comprises a downstream annular edge.

3. Device (2) according to any one of the preceding claims, wherein it comprises an intermediate annular wall which separates the intermediate canal from the external canal, and which comprises a downstream annular edge.

4. Device (2) according to all claims 2 and 3, wherein the downstream edge of the intermediate wall is located further downstream than the downstream edge of the inner wall with respect to the direction of fluid flow in the channels.

5. Device (2) according to claim 3 or 4, wherein at least a part of said injection holes are formed in the intermediate wall.

6. Device according to any one of the preceding claims, wherein it comprises an external annular wall which externally delimits the external channel, and which comprises a downstream annular edge which is free.

7. Device (2) according to claim 6, depending on claim 5, wherein the free edge of the outer wall is located further downstream than the downstream edge of the intermediate wall with respect to the direction of flow of the fluids in the channels.

8. Device (2) according to claim 6 or 7, wherein at least a portion of said injection holes are formed in the outer wall.

9. Device (2) according to any one of the preceding claims, wherein at least a part of said injection holes open into the inside of the external spiral, or downstream of the external spiral.

10. Device (2) according to claim 7, wherein: - the eint / Dint ratio is between 0.02 and 0.5, and / or - the eext / Dext ratio is between 0.02 and 0.5, and / or - the Dext / Dint ratio is between 1.25 and 6, and / or - the hnt / Dint ratio is between 0.25 and 3, and / or - the ext / Dext ratio is between 0.25 and 3, and / or - the Rint / dint ratio is between 0.05 and 0.5, and / or - the Rext / dext ratio is between 0.05 and 0.5, where: eint is the radial thickness of the inner wall, ext the radial thickness of the outer wall, Dint is the internal diameter of the internal canal, Dext is the internal diameter of the external canal, lint is the length of the internal wall at the exit of the internal spiral, lext is the length of the intermediate wall at the exit of the internal spiral, Rint is the axial distance between the downstream edge of the internal wall and the downstream edge of the intermediate wall, and Rext is the axial distance between the downstream edge of the intermediate wall and the downstream edge of the external wall.

11. Device (2) according to any one of the preceding claims, wherein the twist of the internal channel imposes on the fluid a rotation rate of between 0.4 and 2, and / or the twist of the external channel imposes on the fluid a rotation rate of between 0.2 and 1.

2.

12. Device (2) according to any one of claims 1 to 11, wherein the intermediate channel is devoid of a twist.

13. Device (2) according to any one of claims 1 to 11, wherein the intermediate channel comprises an annular spiral.

14. Device (2) according to any one of the preceding claims, wherein it further comprises a flame holder (40) at a downstream axial end of the intermediate channel (18).

15. Combustion chamber for a turbomachine, in particular for aircraft, comprising devices (2) according to any one of the preceding claims.

16. Turbomachine, in particular for aircraft, comprising a combustion chamber according to the preceding claim.

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