TURBOMACHINE FOR AN AIRCRAFT

Abstract

A dihydrogen injection device (2) for a combustion chamber (4) of a turbomachine (1), particularly an aircraft turbomachine, said 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) housed within the internal channel (10), and - an external annular spiral (16) housed within the external channel (12). Figure for the abbreviation: Figure 2

Description

Title of the invention: TURBOMACHINE FOR AN AIRCRAFT

[0001] The present invention relates to turbomachines whose combustion chamber is supplied by separate injections of dihydrogen and air. Technical background

[0002] The aeronautical sector faces major environmental challenges. The interest in using hydrogen combustion rather than kerosene is growing stronger because hydrogen combustion would avoid carbon dioxide (CO2) emissions and carbon pollutants such as carbon monoxide, unburned hydrocarbons, and fine particles and smoke.

[0003] A principle of micro-mixing burners of air and dihydrogen is known. However, such burners do not guarantee the thermal resistance of a perforated wall or the absence of flashback in the dihydrogen injection device. These burners also have a complex geometry. Such burners have a high manufacturing cost, a high pressure drop, and are specific to a given combustion chamber architecture.

[0004] Indeed, the combustion of dihydrogen raises several issues. For example, there is a risk of flame rebound in the injection device for systems operating with mixtures of dihydrogen and air. This can damage the combustion chamber and / or the injection device and pose serious safety problems. Finally, 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 emission levels 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.

[0005] The Applicant proposed a solution to this problem in document FR-Al-3 127 987. It proposed a dihydrogen injection device for mounting on an annular bottom of an annular combustion chamber of a turbomachine, comprising an internal dihydrogen circulation channel and an external annular channel for circulating a mixture comprising at least air. The internal channel and the external annular channel are coaxial, with an internal spiral being housed in the internal channel and an external spiral being housed in the external annular channel. A downstream end of the internal channel is arranged upstream, at a predetermined distance, from a downstream end of the external annular channel.

[0006] This device optimizes the mixing of dihydrogen and air. It also expands the operating range where the flame is detached.

[0007] The detached flame topology makes it possible to limit the thermal stresses on the injector, and therefore to increase its lifespan.

[0008] However, significant pressure drops (-10 to 15% of the generating pressure) are necessary to prevent flame rebound, allow for efficient mixing, and operate within a richness range that emits little NOx (nitrogen oxides). This level of pressure drop is considerably higher than that typically used in aircraft engines (-3-6%) and leads to an increase in their specific fuel consumption. These losses therefore represent a major area for improvement in the development of H2 / Air injection systems for aircraft propulsion.

[0009] These injection devices use a late fuel injection to avoid any risk of backfire, and a large quantity of injected air to create a rapid air-fuel mixture and burn under lean conditions.

[0010] 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) that draws hot gases back to the center of the injector, creating an aerodynamic blockage within it. This blockage reduces the effective cross-section of the H2 injection and deflects it radially outwards, which has the effect of accelerating it and promoting mixing with the air.

[0011] 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.

[0012] It is therefore necessary to accelerate the flow to a level that allows this flame speed to be countered, which entails the need for a high level of pressure loss.

[0013] Furthermore, aerodynamically stabilized flames from high-speed injection devices are likely to trigger combustion instabilities at certain operating points or during transient regimes, thus 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 the 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 / H2 combustion. It is therefore necessary to design An injection device that ensures combustion in a low NOx regime and does not exhibit combustion instability. In this regard, the Air / H2 combustion tests conducted to date have shown significantly lower acoustic activity and improved flame stability when operating with the flame attached to the injection device.

[0014] Finally, along the operating range of a turbomachine, it is possible to achieve a wide range of air-fuel mixtures. There is therefore a risk of operating with stoichiometric air-fuel mixtures, which can lead to rapid flame flares and high NOx emissions.

[0015] The present invention provides a solution to at least some of the problems of the prior art, which is simple, efficient, and economical. Summary of the invention

[0016] According to a first aspect, the invention relates to a dihydrogen injection device for a turbomachine combustion chamber, in particular for aircraft, this device comprising a main shaft and comprising:

[0017] - an internal fluid circulation channel, the internal channel being centered on the axis main,

[0018] - an external annular fluid circulation channel, the external channel being centered on the main axis extending around the internal canal,

[0019] - an internal spiral lodged in the internal channel, and / or an external annular spiral housed in the external canal,

[0020] characterized in that the device further comprises:

[0021] - 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,

[0022] and in that the internal and external channels are suitable for being supplied with a mixture comprising at least air.

[0023] 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 the mixing by increasing the Air / H2 exchange surface area and to increase the air passage cross-section in order to reduce the pressure drop at a constant air flow rate, and therefore at a constant air-fuel ratio.

[0024] 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.

[0025] 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.

[0026] According to a second aspect, the invention relates to an injection device as described above and further comprising a flame holder at an axial downstream end of the intermediate channel (relative to the direction of fluid flow in the channels).

[0027] 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 attachment device. Thermal issues at the wall at the point of flame attachment can be addressed with dihydrogen impact cooling.

[0028] 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.

[0029] The invention consists of significantly increasing the H2 / Air mixing surface area by injecting a portion of the dihydrogen upstream of the injector outlet to allow the mixture to establish itself. Thus, part of the H2 is injected using a premixed injection type, and the remainder is injected with a LDI (Linear Direct Injection) type injection. Furthermore, the concentration of the H2 / Air premix present in the external air stream is kept below the flammability limits to prevent any risk of flame rebound.

[0030] Generally, a spiral allows a flow to be rotated. A spiral may include a helical part with a suitable helix pitch. This helix pitch is configured to define the positioning of the flame 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.

[0031] The device according to the invention may comprise one or more of the following features, taken individually or in combination with each other: - 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; - 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; - the external separator is located further downstream than the internal separator with respect to the direction of fluid flow in the channels; - 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 downstream annular edge which is free; - 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; - 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 lint / 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

[0032] eint the radial thickness of the inner wall,

[0033] eextl radial thickness of the external wall,

[0034] Dint the internal diameter of the internal channel,

[0035] Dext the internal diameter of the external channel,

[0036] lint the length of the inner wall at the exit of the internal spiral,

[0037] lext the length of the intermediate wall at the exit of the internal spiral,

[0038] Rint the axial distance between the downstream edge of the inner wall and the downstream edge of the intermediate wall,

[0039] Rext the axial distance between the downstream edge of the intermediate wall and the downstream edge of the external wall; - 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; - 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 at a radial distance from each other; - the downstream edges of the internal and intermediate walls are connected together by an annular bottom wall which includes fluid injection orifices; - 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; - the intermediate channel is devoid of twists; - the intermediate canal includes an annular spiral; - the device includes an internal annular wall that separates the internal channel of the intermediate canal, and which includes a downstream annular border; - the device includes an intermediate annular wall which separates the intermediate canal from the external canal, and which includes a downstream annular edge. - the downstream edges of the internal and intermediate walls together form the said flame catch; - the downstream edges of the internal and intermediate walls are connected together by an annular bottom wall; - the bottom annular wall includes at least one annular row of fluid injection orifices, and / or at least one annular fluid injection slot; - 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; - 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 lint / Dint ratio is between 0.25 and 3, and / or the lext / Dext ratio is between 0.25 and 3, with:

[0040] e the thickness or transverse dimension of the flame holder 40,

[0041] The internal diameter of the internal channel is 10,

[0042] Dext the internal diameter of the external channel 12,

[0043] lint the length of the internal wall 20 at the exit of the internal screw 14;

[0044] lext the length of the intermediate wall 26 at the exit of the internal spiral 14; - at least one of the downstream edges of the internal and intermediate walls includes a projecting annular beak; at least one of the downstream edges of the internal and intermediate walls includes a bevel formed by a frustoconical surface; the device includes an external annular wall which externally delimits the external channel, and which includes a downstream annular edge which is free; the free edge of the outer wall is located further downstream than the downstream edges of the inner and intermediate walls; at least one of the annular walls is convergent, or convergent then divergent, or divergent; 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; the device includes an internal annular wall which separates the internal canal from the intermediate canal, and which includes a downstream annular edge; the device includes an intermediate annular wall which separates the intermediate canal from the external canal, and which includes a downstream annular edge. 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; at least part of said injection holes are formed in the intermediate wall; the device includes an external annular wall which externally delimits the external channel, and which includes a downstream annular edge which is free; 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 part of said injection holes are formed in the outer wall; at least some of said injection holes open into the inside of the external spiral, or downstream of the external spiral; the device further includes at least one obstacle which extends transversely inside the intermediate channel, said injection holes being located upstream of this obstacle; 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 lint / 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

[0045] determines the radial thickness of the inner wall,

[0046] eextl'thickness radial de la mur external,

[0047] Dint the internal diameter of the internal channel,

[0048] Dext the internal diameter of the external channel,

[0049] lint the length of the inner wall at the exit of the internal spiral,

[0050] lext the length of the intermediate wall at the exit of the internal spiral,

[0051] Rint the axial distance between the downstream edge of the inner wall and the downstream edge of the intermediate wall, and

[0052] Rext the axial distance between the downstream edge of the intermediate wall and the downstream edge of the external wall; - 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; - the intermediate channel is devoid of twists; - the intermediate canal includes an annular spiral.

[0053] The characteristics of the different aspects of the invention can be combined with each other.

[0054] The present invention also relates to a combustion chamber for a turbomachine, in particular for aircraft, comprising devices such as those described above.

[0055] The present invention also relates to a turbomachine, in particular for aircraft, comprising a combustion chamber as described above. Brief description of the figures

[0056] 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:

[0057] [Fig-1] shows a turbomachine comprising a dihydrogen injection device arranged in an annular bottom of an annular combustion chamber in three configurations;

[0058] [Fig.2] [Fig.2] is a very schematic view of an injection device according to the invention;

[0059] [Fig.3] [Fig.3] is another very schematic view of an injection device according to the invention, and shows dimensional parameters of this device;

[0060] [Fig.4] [Fig.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;

[0061] [Fig.5] [Fig.5] represents in a very schematic way several variants of fabrication 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;

[0062] [Fig.6] [Fig.6] represents in a very schematic way several variants of fabrication of injection devices according to the invention, the devices differing from each other by the end of the intermediate H2 injection channel;

[0063] [Fig.7] [Fig.7] represents in a very schematic way other variants of fabrication of injection devices according to the invention, the devices differing from each other by the end of the intermediate H2 injection channel;

[0064] [Fig.8] [Fig.8] is a very schematic view of another injection device according to the invention;

[0065] [Fig.9] [Fig.9] is a very schematic view of an injection device according to the invention, and shows dimensional parameters of this device;

[0066] [Fig. 10] [Fig. 10] 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 shape of the channels or assemblies of channels / air spirals;

[0067] [Fig. 11] [Fig. 11] represents in a very schematic way several variants of the embodiment of flame holders for injection devices according to the invention;

[0068] [Fig. 12] [Fig. 12] is a very schematic view of another injection device according to the invention;

[0069] [Fig. 13] [Fig. 13] is a very schematic view of an injection device according to the invention, and shows dimensional parameters of this device;

[0070] [Fig. 14] [Fig. 14] 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 shape of the channels or assemblies of channels / air spirals;

[0071] [Fig. 15] [Fig. 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;

[0072] [Fig. 16] [Fig. 16] represents in a very schematic way other 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;

[0073] [Fig. 17] [Fig. 17] represents in a very schematic way other variants of embodiment of injection devices according to the invention;

[0074] [Fig. 18] [Fig. 18] represents in a very schematic way several variants of embodiment of injection devices according to the invention;

[0075] [Fig. 19] [Fig. 19] represents in a very schematic way another variant of an embodiment of an injection device according to the invention;

[0076] [Fig.20] [Fig.20] represents in a very schematic way another embodiment of an injection device according to the invention; and

[0077] [Fig.21] [Fig.21] represents in a very schematic way other variants of fabrication of an injection device according to the invention. Detailed description of the invention

[0078] 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.

[0079] This dihydrogen injection device 2 is used in a dihydrogen-lean combustion configuration such that flame temperatures and nitrogen oxide formation are reduced.

[0080] The injection device is said to be lean when there is excess dioxygen compared to a combustion taking place at stoichiometry between dihydrogen and air, and the injection device is said to be rich when there is excess dihydrogen compared to this combustion at stoichiometry.

[0081] 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 in the combustion products. The present invention falls within the context of low-hydrogen combustion.

[0082] As illustrated in [Fig.1], three implantations of the dihydrogen injection device 2 are possible depending on the orientation of the annular bottom of the annular combustion chamber 4:

[0083] - either the combustion chamber is oriented substantially along a longitudinal axis, with the chamber bottom located towards the front or upstream of the engine, called the direct chamber,

[0084] - either the combustion chamber is oriented substantially along a longitudinal axis, with the chamber bottom located towards the rear or downstream of the engine called a reverse flow chamber as illustrated in [Fig.1],

[0085] - either the combustion chamber is transverse to said longitudinal axis X.

[0086] In all cases, the dihydrogen 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.

[0087] As illustrated in [Fig.2], a dihydrogen injection device 2 according to the invention comprises a principal axis Y and includes:

[0088] - an internal fluid circulation channel 10, the internal channel 10 being centered on the axis principal Y,

[0089] - an external annular fluid circulation channel 12, the external channel 12 being centered on the main Y axis and extending around the internal channel 10,

[0090] - an internal spiral 14 housed in the internal channel 10 and / or an external annular spiral 16 housed in the external canal 12, and

[0091] - an intermediate annular fluid circulation channel 18, the intermediate channel 18 being centered on the main Y axis and extending between the internal and external channels 10, 12.

[0092] 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).

[0093] Advantageously, the twist 14 of the internal channel 10 imposes on the fluid a rotation rate S between 0.4 and 2.

[0094] Advantageously, the twist 16 of the external channel 12 imposes on the fluid a rotation rate S between 0.2 and 1.2.

[0095] The intermediate channel 18 is devoid of a twist in the example of [Fig.2].

[0096] The device 2 comprises an internal annular wall 20 which separates the internal channel 10 of the intermediate canal 18, and which includes a downstream annular border 22 which forms an internal annular separator 24. This border 22 can be free as is the case in [Fig.2],

[0097] The device 2 comprises an intermediate annular wall 26 which separates the intermediate channel 18 from the external channel 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 [Fig. 2]. It can thus be seen in the figure that the free edges 22, 27 are at a radial distance from each other.

[0098] The external separator 28 is preferably located further downstream than the internal separator 24 with respect to the direction of flow of the fluids in the channels (see arrows).

[0099] The 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.

[0100] 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.

[0101] The dimensional parameters of the device 2 according to the invention can be optimized to limit any air detachment and any harmful recirculation during operation.

[0102] As can be seen in [Fig.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 to say from upstream to downstream along the Y axis.

[0103] The radial thickness of the downstream end of the inner wall 20 can be refined up to a limit imposed by the manufacturing means.

[0104] The distance Dext- (Dmid+2.eext) can decrease as a function of L. This decrease ensures that the air does not detach from the intermediate wall 26.

[0105] 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.

[0106] 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 / hydrogen 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 is to prevent the formation of a stoichiometric air-fuel line between the fuel and the air in the external channel 12 at the separator 28.

[0107] 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.

[0108] [Math.l] r2n r* mux J(| ï^pUgU^drdO r»^o drdd

[0109] with: • S the turnover rate, • p the density of the fluid, • Uqla tangential velocity of the fluid, • Ux, the axial velocity of the fluid, • rmin the minimum radius of the channel, rmin = 0 for the central channel, and • rmax the maximum radius of the channel.

[0110] The ratios eint / Dint and eext / Dext can be between 0.02 and 0.5.

[0111] The Dext / Dint ratio can be between 1.25 and 6.

[0112] The lint / Dint and lext / Dext ratios can be between 0.25 and 3.

[0113] The Rint / Dint and Rext / Dext ratios can be between 0.05 and 0.5

[0114] With:

[0115] eint the radial thickness of the inner wall 20,

[0116] eextl'thickness radial de la mur external 30,

[0117] The internal diameter of the internal channel is 10,

[0118] Dext the internal diameter of the external channel 12,

[0119] lint the length of the internal wall 20 at the exit of the internal spiral 14,

[0120] lext the length of the intermediate wall 26 at the exit of the internal spiral 14,

[0121] Rint the axial distance between the downstream edge 22 of the internal wall 20 and the downstream edge 27 of the intermediate wall 26,

[0122] Rext the axial distance between the downstream edge 27 of the intermediate wall 26 and the downstream edge 32 of the external wall 30.

[0123] Figure 4 shows an example of refining the internal wall 20 from an eccentricity e0 to a thickness ecc. The angle pe represents the inclination of the intermediate wall 26, and in particular of an internal annular surface of this intermediate wall, and [3; represents the inclination of the internal wall 20 and in particular of an external annular surface of this internal wall 20.

[0124] The external surface of the internal wall 20 converges downstream with the first angle of inclination [>,, and the internal surface of the intermediate wall 26 converges downstream with the second angle of inclination pe

[0125] The second angle of inclination pe is preferably greater than the first angle of inclination p; 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.

[0126] The refinement can be made 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 [3; is high and is not conducive to creating air separation.

[0127] This angle p; is defined such that:

[0128] [MATH2] = tan 1 ((e0-ecc) / Lint)

[0129] Depending on the orientation and width of the tendrils 14, 16, of the angle p; and of Lint, the angle pe can vary from 0 to 50°.

[0130] The difference [3e - pi can be in a range of 1 to 20°, in order to ensure a tightening of the external channel allowing to compensate for the detachment.

[0131] The Lint length is minimized in order to limit the centrifugal effect of the air in the external channel 12, while being long enough to dissipate the wake effects of the spirals, in order to avoid low speeds above the separator.

[0132] In a particular embodiment of the invention, the following dimensioning rules are applied: • Lint > 4 mm • 50° > pe > 0° • 20o>pe-pi>l°

[0133] The variants illustrated in [Fig. 5] offer a double advantage: a limitation recirculation zones above the separators, and maximization of air speeds at the mixing zones to deplete the Air / H2 mixture as quickly as possible.

[0134] The external channel variants 12,1, ILa, Il.b, IILa, Ill.b, IV.a, IV.b, Va, can be implemented with a right internal channel 10, or not as in the variants Vb, Vl.a, Vl.b, VILa, Vll.b.

[0135] A first variant I) can use a convergent / divergent outer 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 outer wall 30 can also facilitate the anchoring of the internal recirculation zone in the injection device.

[0136] 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.

[0137] A third variant III) may use an internal surface of the intermediate wall 26 which 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.

[0138] 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 reopening the flow at the outlet of the injection device to promote penetration of the internal recirculation zone into the injection device and increase the aerodynamic blockage that accelerates the central airflow. Sub-variant IV.b) uses an inclined channel and rotating spiral assembly.

[0139] 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 blocking which accelerates the internal airflow.

[0140] A sixth variant VI) may use a divergent internal air channel, either straight according to variant Vl.a), or concave according to variant Vl.b) to limit the drop in the rotation rate given by equation [MATH1] in the internal channel 10.

[0141] A seventh variant VII) may use a converging internal channel 10, either straight according to variant VILa) or convex according to variant Vll.b), in order to accelerate the airflow of the channel 10 before the Air / H2 mixing zone.

[0142] The variants illustrated in [Fig.6].a) also allow a late injection of H2 to avoid the risk of backfire, while allowing a rapid Air / H2 mixing for LDI (Lean Direct Injection) type operation.

[0143] Variants 1 to 4 of [Fig.6].a) may add an additional inclination to the walls 20, 26 constituting the channel 18 for H2, and / or modify the position of the internal and external separators 24, 28.

[0144] Variants 5 to 11 of [Fig.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.

[0145] 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.

[0146] 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 / 1 is between 0 and 0.5, with 1 being the minimum between lint and lext. 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 [Fig. 6].b).

[0147] All variants 1 to 12 shown in [Fig.6].a) can be implemented with all air channel variants shown previously.

[0148] Examples are given in [Fig.7].a) which proposes the combination of variants 10 and 11 with a three-directional injection of H2.

[0149] 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.

[0150] The first variant 1) of [Fig.6].a) can operate without axial withdrawal of the separators 24, 28, i.e. Rint=Rext.

[0151] 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.

[0152] The second variant 2) can use an internal channel end 10 inclined towards the H2 injection to promote Air / H2 mixing.

[0153] The third variant 3) can use an external channel end 12 inclined towards the H2 injection for the same reasons.

[0154] 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.

[0155] 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, in order to maximize shear with air and promote mixing. These injection modes can be coupled with straight injection to eliminate the recirculation zone downstream of the bottom wall 36 and prevent flame snagging.

[0156] The sixth variant 6) can use a beveled bottom wall 36 to minimize the recirculation zone downstream of the bottom wall 36. The 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.

[0157] 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.

[0158] A seventh variant 7) may use a doubly beveled bottom wall 36 to minimize the recirculation zone downstream of the bottom wall 36 and generate a local acceleration of the flow to prevent flame snagging. The directed injection of H2 may be made in one or both of the two air channels to maximize shear with the air and promote mixing. The H2 injection may be located directly below the bevel or further upstream.

[0159] The eighth variant 8) can use a doubly 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 allows for the use of an injection method towards the chamber. Directed H2 injections towards the air channels can also be added (Figures 7.b and 7.c).

[0160] 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.

[0161] 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.

[0162] 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.

[0163] Finally, the twelfth variant 12) can use a corrugated bottom wall 36 to maximize the Air / H2 mixing surface.

[0164] Figure 8 shows a variant in which the intermediate channel 18 comprises an annular screw 38. The H2 flow is thus set in rotation upstream of the injection by the screw 38. This rotation can promote shearing with the air and / or covering the separator 28 by centrifugal effect in order to eliminate its recirculation zone induced by the separator 28.

[0165] Fig. 9 illustrates a variant embodiment of a dihydrogen injection device 2 in which the elements already described above are designated by the same references.

[0166] The device of [Fig.9] differs from that of [Fig.2] in particular in that it also includes a flame holder 40 at the downstream end of the intermediate channel 18.

[0167] The intermediate channel 18 is thus designed to perform the flame-attachment function.

[0168] Preferably, the downstream edges of the internal wall 20 and intermediate wall 26 are connected together by a bottom annular wall 36.

[0169] 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.

[0170] The bottom wall 36, added at the end of the intermediate channel 18, makes it possible to create a small recirculation zone allowing the flame to be attached.

[0171] 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.

[0172] 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).

[0173] 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.

[0174] The dimensional parameters of device 2 according to the invention can be:

[0175] The e / Dext ratio can be between 0.04 and 0.5.

[0176] The Dext / Dint ratio can be between 1.25 and 6.

[0177] The lint / Dint and lext / Dext ratios can be between 0.25 and 3.

[0178] With:

[0179] e the thickness or transverse dimension of the flame holder 40,

[0180] The internal diameter of the internal channel is 10,

[0181] Dext the internal diameter of the external channel 12,

[0182] lint the length of the internal wall 20 at the exit of the internal spiral 14,

[0183] lext the length of the intermediate wall 26 at the exit of the external spiral 16.

[0184] The variants illustrated in [Fig. 10] allow for maximization of air velocities at the mixing zones to deplete the Air / H2 mixture as quickly as possible.

[0185] The external channel variants 12 I, ILa, Il.b, Ill.a, Ill.b can be implemented with the right internal channel 10.

[0186] The first variant I) of [Fig. 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 in the injection device.

[0187] 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.

[0188] The third variant III) can use an outer 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 blocking which accelerates the central airflow.

[0189] Sub-variant Ill.b) uses an inclined channel and rotational screw assembly.

[0190] [Fig. 11] shows other embodiments, in particular of the flame attachment 40.

[0191] The first variant 1) of [Fig.1 1] features a type of flame attachment 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.

[0192] 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 maintain the recirculation zone downstream of the plate thus allowing the flame to catch.

[0193] 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.

[0194] 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 carried out using one or more rows of circular or other shaped orifices 34. Injection through the wall 36 or the plate can be carried out using injection orifices 34 circular ([Fig.ll].ba), of orifices of any shape, or even by means of an annular slit 45 ([Fig. 1 l].bb).

[0195] Another variant of hydrogen injection is shown in [Fig. 12]. This variant is based on a convergent bevel and is compatible with the different variants of the air channels and the different variants of the injection points presented previously.

[0196] This variant allows the flame to attach 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's attachment.

[0197] Fig. 13 illustrates a variant embodiment of a dihydrogen injection device 2 in which the elements already described above are designated by the same references.

[0198] The device of [Fig. 13] differs from that of [Fig.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.

[0199] At least part of said injection holes 46 can be formed in the intermediate wall 26 ([Fig. 13] for example).

[0200] At least part of said injection holes 46 are formed in the outer wall 30 ([Fig. 17].a for example).

[0201] 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 ([Fig. 13] for example).

[0202] Advantageously, the injection device 2 further comprises 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 [Fig.13].

[0203] The injection holes 46 are preferably located upstream of this obstacle 48.

[0204] The intermediate channel 18 is preferably designed to inject the fuel by two different paths: - 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 - an injection near the injector outlet ensuring LDL injection

[0205] This type of fuel distribution maximizes the air / H2 mixture. Indeed, 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 to facilitate mixing. The fuel distribution developed in this injection device thus makes it possible to achieve a lean premixed combustion with very low temperatures and therefore low NOx emissions.

[0206] The distribution of dihydrogen can be active (two independent injection lines) or passive (distribution determined by the blockage in the H2 injection channel).

[0207] Regardless of the type of distribution, the ratio between the flow rate of H2 injected downstream for premixing and that injected in LDI can be limited by the following constraint: the richness of the H2 / Air premix present in the external air stream is located below the flammability limits, to avoid any risk of flame rising.

[0208] The proposed variants are based on the same principle as the aforementioned proposal: a limitation of the 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.

[0209] The variants of the external channel 12 of [Fig. 14] are similar to that of [Fig. 5].

[0210] The comments concerning [Fig. 5] therefore apply to variants of the [Fig.14]

[0211] Similarly, the embodiment variants of Figures 15 and 16 apply to the case of [Fig.13], and the comments concerning Figures 5 and 6 apply to these variants.

[0212] The injection of H2 to create an air-fuel premix can be carried out via the air channel or the air augers. In the cases described above, the injection is made in the external vein. It is also possible to make this injection in the internal vein or both combined, provided that the premix preferably remains below the flammability limit.

[0213] The different variants associated with injection through the external air channel are presented in [Fig. 17].

[0214] The first two variants shown in [Fig. 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 ([Fig. 17].a), or along and through the intermediate wall 26 ([Fig. 17].b). Finally, [Fig. 17].c. 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.

[0215] On the other hand, the variants associated with injection via the external air auger are presented in [Fig. 18]. Injection via the auger blades avoids injection close to the walls. This method thus allows injection perpendicular to the airflow with multiple injection points, thereby accelerating mixing.

[0216] The first two versions shown in [Fig. 18] concern 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 version [Fig. 18].a, or through the intermediate wall as schematically shown in [Fig. 18].b. Finally, [Fig. 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.

[0217] The H2 injected in LDI can be rotated either by adding the spiral 38 ([Fig.19].a) or by means of the obstacle 48 ([Fig.19].b), which can have a geometry capable of rotating the H2 in the LDL injection

[0218] The variant of [Fig.20] is based on the combination of aspects of the invention illustrated in Figures 9 and 13, and proposes to inject a part of the H2 upstream of the injection orifices 34 described previously to create an Air / H2 premix upstream of the combustion zone.

[0219] 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 less than the flammability limit.

[0220] The distribution of dihydrogen can be active (two independent injection lines, [Fig. 21].b) or passive (distribution determined by the blockage in the H2 injection channel, Figures 20, 21.a and 21.c). 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 ([Fig. 20]) or through the augers 12, 16 ([Fig. 21]).

[0221] 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.

[0222] The device according to the invention allows, in particular: - to obtain aerodynamically stabilized flames (or detached flames, i.e., without contact with the injector) over a wide operating range, - to achieve a lean, partially premixed, low NOx combustion, - to avoid any risk of flame flashback in the injection device, - etc.

Claims

Demands

1. A dihydrogen injection device (2) for a combustion chamber (4) of a turbomachine (1), particularly an aircraft turbomachine, said device (2) comprising a principal axis (Y) and comprising: - an internal fluid circulation channel (10), the internal channel (10) being centered on the principal axis (Y), - 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), - an internal spiral (14) housed in the internal channel (10), and / or an external annular spiral (16) housed in the external channel (12), characterized in that the device (2) further comprises: - an intermediate annular fluid circulation channel (18), the intermediate channel (18) being centered on the principal axis (Y) and extending between the internal and external channels (10, 12), the intermediate channel (18) being suitable for being powered by dihydrogen,- a flame holder (40) at a downstream axial end of the intermediate channel (18), and in that the internal and external channels (10, 12) are suitable for being supplied with a mixture comprising at least air.

2. Device (2) according to claim 1, wherein it comprises an internal annular wall which separates the internal channel from the intermediate channel, 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 edges of the internal and intermediate walls together form said flame hook.

5. Device (2) according to claim 4, wherein the downstream edges of the internal and intermediate walls are connected together by a bottom annular wall.

6. Device (2) according to claim 5, wherein the bottom annular wall comprises at least one annular row of fluid injection orifices, and / or at least one annular fluid injection slot.

7. Device (2) according to claim 5 or 6, wherein 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.

8. Device (2) according to claim 7, wherein: The ratio e / Dext is between 0.04 and 0.5, and / or The ratio Dext / Dint is between 1.25 and 6, and / or The ratio lint / Dint is between 0.25 and 3, and / or The ratio lext / Dext is between 0.25 and 3, with: e the thickness or transverse dimension of the flame holder 40, Dint the inner diameter of the inner channel 10, Dext the inner diameter of the outer channel 12, lint the length of the inner wall 20 at the exit of the inner spiral 14, lext the length of the intermediate wall 26 at the exit of the inner spiral 14.

9. Device (2) according to any one of claims 4 to 8, wherein at least one of the downstream edges of the inner and intermediate walls comprises a projecting annular spoiler.

10. Device (2) according to any one of claims 4 to 9 in which at least one of the downstream edges of the internal and intermediate walls comprises a bevel formed by a frustoconical surface.

11. Device (2) 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.

12. Device (2) according to claim 11, depending on any one of claims 4 to 10, wherein the free edge of the outer wall is located further downstream than the downstream edges of the inner and intermediate walls.

13. Device (2) according to any one of claims 4 to 10 and 12, wherein at least one of the annular walls is convergent, or convergent then divergent, or divergent.

14. Device (2) according to any one of the preceding claims, wherein 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.

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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