Hydrogen and air injection device
The dihydrogen injection device with internal and external spirals stabilizes flames aerodynamically, addressing flashback and thermal issues, reducing emissions and manufacturing complexity in turbomachinery.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2021-10-08
- Publication Date
- 2026-03-20
AI Technical Summary
Existing hydrogen combustion systems in turbomachinery face issues such as flame flashback, high thermal loads, nitrogen oxide emissions, and complex geometry, leading to safety risks and high manufacturing costs, which are not addressed by current micro-mixing burners.
A longitudinal axis dihydrogen injection device with internal and external coaxial channels and spirals, creating a recirculation zone to stabilize the flame aerodynamically, reducing nitrogen oxide emissions and thermal stress, and simplifying manufacturing.
The device achieves low nitrogen oxide emissions, reduced thermal stress, and simplified manufacturing, while being adaptable to existing turbomachinery, with minimal pressure loss and risk of flameback.
Abstract
Description
Title of the invention: Device for injecting dihydrogen and air technical field
[0001] This document relates to turbomachinery whose combustion chamber is supplied by separate injections of dihydrogen and air. Previous technique
[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-based pollutant emissions 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 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. Summary
[0005] This document relates to a longitudinal axis dihydrogen injection device intended to be mounted on an annular bottom of an annular combustion chamber of a turbomachine comprising an internal dihydrogen circulation channel and an external annular circulation channel of a mixture comprising at least air, the internal channel and the external annular channel being coaxial, an internal spiral being housed in the internal channel and an external spiral being housed in the external annular channel, and in which a downstream end of the internal channel is arranged upstream, at a distance r, from a downstream end of the external annular channel.
[0006] This device produces a dihydrogen / air flame usable in turbomachinery, resulting in low nitrogen oxide emissions, low thermal stress on the combustion chamber and injector, and eliminating the risk of flameback. Furthermore, this injector is both simple to manufacture and easily adaptable to existing kerosene-powered turbomachinery.
[0007] Generally, a spiral allows a flow to be rotated. Integrating an internal spiral into the internal channel creates a recirculation zone for the hydrogen flow passing through said internal channel, preventing the combustion of the air-hydrogen mixture from stabilizing at the downstream end of the internal channel. A recirculation zone is defined as an area generating a centrifugal effect with a low pressure inside, capable of producing an axial velocity component of the flow that is negative on average with respect to a principal flow direction. This recirculation zone is similar to that generated inside a vortex into which air is drawn.The internal recirculation zone blocks a portion of the hydrogen flow along the longitudinal axis of the internal channel. This generates significant overvelocities in the outlet section of the internal channel, near the channel walls, compared to a flow with a uniform axial velocity. Rotating the hydrogen within the internal channel prevents the flame from catching on the downstream ends of the channel by aerodynamically stabilizing it above the channel. Since the downstream end of the internal channel is positioned upstream at a distance r, this further prevents the flame from catching on the channel lips. This rotation of the hydrogen within the internal channel eliminates the need for a complex cooling system for the hydrogen injection device. Consequently, the cost and mass of the hydrogen injection device are reduced.This hydrogen injection device produces limited pressure losses compared to other liquid injection devices using kerosene, as in the prior art. This hydrogen injection device features a simple geometry, low manufacturing cost, and can be adapted to existing combustion chamber architectures.
[0008] This remote flame stabilization facilitates partial mixing of the air with the dihydrogen exiting the internal channel, upstream of the flame, and prevents any risk of flame flashback into said internal and external channels. This results in a dihydrogen-depleted combustion in the combustion chamber. This device thus tends to significantly reduce combustion temperatures and nitrogen oxide emissions. This ensures the integrity of the combustion chamber.
[0009] The positioning of the downstream end of the internal channel upstream of the downstream end The external annular channel serves two functions. It optimizes the mixing of hydrogen and air. It also expands the operating range where the flame is detached by moving the central hydrogen introduction zone further back from the aerodynamic stabilization zone of the flame.
[0010] The internal channel may be a central tubular channel.
[0011] At least the internal spiral of the internal channel may have a helical shape.
[0012] This helical shape makes it possible to improve the aerodynamics of the dihydrogen flow passing through the internal twist.
[0013] The internal spiral can be arranged along the longitudinal axis downstream of the external spiral.
[0014] A rotation rate S generated by the internal twist of the internal channel, defined as a ratio between a tangential velocity and a flow velocity along the longitudinal axis of a dihydrogen flow at the outlet of the internal twist, can be equal to or greater than 0.6.
[0015] These values of the rotation rate S, which is a dimensionless number, make it possible to obtain flames having a rotational movement with respect to the longitudinal axis which are detached from the internal channel.
[0016] The internal spiral of the internal channel can be arranged upstream, at a distance l, from the downstream end of the internal channel.
[0017] The internal channel may have an internal diameter d and the external annular channel may have an internal diameter D such that a ratio D / d is between 2 and 5.
[0018] This optimized D / d ratio allows operation in a dihydrogen-poor regime.
[0019] An e / d ratio can be between 0.05d and 0.5d.
[0020] A 1 / d ratio can be between 1 and 3.
[0021] The minimum distance lmin is equal to Id so that a central recirculation zone penetrates the internal channel. The larger 1 / d is, the greater the insertion distance of the auger relative to the diameter, and the higher the rotation rate S can be. The range chosen for 1 / d provides a good compromise and a sufficient rotation rate S to properly rotate the flame.
[0022] The distance r can be between 0.05D and 0.5D.
[0023] There is an optimal value for the distance r that depends on the diameter D of the external channel. If this distance r is too large, the recirculation zone becomes unstable. The range of values chosen for r is optimized to obtain a stable recirculation zone.
[0024] This distance r relative to the downstream end of the external annular channel makes it possible to increase the operating range where the flame is detached by moving a dihydrogen introduction zone further back relative to the aero- stabilization zone flame dynamics.
[0025] The external spiral of the external annular canal can be arranged at an upstream end of said external annular canal, at a distance L from the downstream end of the external annular canal.
[0026] The distance L can be between 2d and 5D. The rotation rate S can be greater than 0.6, a flow velocity u of di-hydrogen in the internal channel being greater than a critical value ui>cet satisfying the following relationship: “the _ (SoVp ( T„ f»Where: »1. e0-\ s) Po 1 tm ,1 - P is a pressure in the annular combustion chamber; - Ta is the air temperature in Kelvin in the external channel; - / 5 between 1 and 1.5 is a factor dependent on the type of twist used; - S0=0.6, P0=l bar, Ta0=300 K and ubc0=18 m / s.
[0027] This critical value ui>c ensures that the flame formed at the outlet of the injection device is detached from the downstream ends of the internal channel for a wide engine operating range.
[0028] The mixture can be air.
[0029] The present document relates to an assembly comprising the device of the aforementioned type, in which the internal channel, fluidly connected to means for supplying di-hydrogen, includes the internal spiral configured to rotate said di-hydrogen, and the external annular channel, fluidly connected to means for supplying air, includes the external spiral configured to rotate said air. Brief description of the drawings
[0030] Other features, details and advantages will become apparent from reading the detailed description below and from analyzing the accompanying drawings, in which: Fig. 1
[0031] [Fig.1] shows a turbomachine comprising a di-hydrogen injection device arranged in an annular bottom of an annular combustion chamber in two configurations. Fig. 2
[0032] [Fig.2] shows the dihydrogen injection device, according to the invention. Fig. 3
[0033] [Fig.3] schematically shows the formation of a recirculation zone which penetrates the dihydrogen injection device and a flame at the outlet of the dihydrogen injection device. Fig. 4
[0034] [Fig.4] shows a plurality of possible configurations (figures A, B, C, D, E, F, G, H) of internal channel, according to the invention. Fig. 5
[0035] [Fig.5] shows a plurality of possible configurations (figures A, B, C, D, E) of the downstream end of the external annular channel, according to the invention. Detailed description
[0036] This document relates to a dihydrogen injection device 2 for mounting on an annular bottom of an annular combustion chamber 4 of a turbomachine. This dihydrogen injection device 2 is used in a dihydrogen-lean combustion configuration such that flame temperatures and nitrogen oxide formation are reduced. The injection device is said to be lean when there is excess dioxygen compared to stoichiometric combustion between dihydrogen and air, and the injection system is said to be rich when there is excess dihydrogen 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 in the combustion products.The present invention is situated within the context of hydrogen-poor combustion.
[0037] As illustrated in [Fig.1], two implantations of said 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 substantially along a longitudinal axis, or the combustion chamber is transverse to said longitudinal axis X. In all cases, the dihydrogen injection device 2 is implanted between the compressor and the high-pressure turbine, on the annular bottom of the annular combustion chamber 4 or on an external shell.
[0038] As illustrated in [Fig.2], said dihydrogen injection device comprises an internal channel 6 and an external annular channel 8. The internal channel 6 and the external annular channel 8 are coaxial.
[0039] A first gas is injected from an inlet 10 located at an upstream end of the internal channel 6. This first gas is dihydrogen 12. The internal channel 6 has an internal diameter d. The choice of the internal diameter d of the channel depends on a desired thermal power. A wall thickness e of the internal channel corresponds to half the difference between an external diameter of the internal channel and an internal diameter d of the internal channel. The ratio e / d is between 0.05d and 0.5d.
[0040] This internal channel 6 has an internal twist 14 configured to rotate A flow of dihydrogen 12 around a longitudinal axis X. The internal spiral 14 of the internal channel 6 is arranged at a distance Z from a downstream end 16 of the internal channel. The distance Z between the downstream end 16 of the internal channel 6 and a downstream end 18 of the internal spiral 14 is between Id and 5d. As illustrated in [Fig. 3], a space is thus left between the internal spiral 14 and the downstream end 18 of the internal channel 6 so that a central recirculation zone 20 can be established. The recirculation zone is a region around the longitudinal axis X of the injection device where an axial component of the flow is on average negative with respect to a principal flow direction. This recirculation zone 20 generates a centrifugal effect, and a pressure drop is created within it. This recirculation zone 20 is similar to that generated inside a vortex in which air is drawn in.In this document, the recirculation zone 20 is configured to penetrate the internal channel, blocking part of the downstream end section 16 of the internal channel 6 and producing an acceleration of the flow at the periphery. This pushes back a flame 22 formed at the outlet of the injection device and sets it into rotation.
[0041] The internal spiral 14 may, for example, comprise a helical part with a suitable helix pitch. This helix pitch is configured to define a positioning of the flame 22 at the outlet of the injection device 2, to minimize pollutant emissions and define a thermal conductivity of the injection device. This helical part rotates the dihydrogen flow with a rotation rate characterized by a dimensionless number S. This rotation rate S is defined as a ratio of an angular momentum to the product of a channel radius multiplied by an impulse of the rotating dihydrogen flow 12, according to the following formula: 5=2 G, DG where Ge is the angular momentum of the flow along an axial direction, G7 is the flow impulse along the axial direction, and R = D / 2 is the channel radius. Approximate expressions are generally used to estimate G^ and G7 based on the tangential and axial velocities of the rotating flow in the channel. In this case, T corresponds to the ratio of a tangential velocity to an axial velocity. The tangential velocity represents a rotational component of the velocity.
[0042] A blockage rate for the flow of dihydrogen 12 in the internal channel 6 is established so as to be sufficiently high to repel the flame 22 forming at a downstream end 24 of the external annular channel 8. The blockage rate represents a ratio between a cross-section occupied by the recirculation zone 20 extending up inside the dihydrogen injection device 12 at the downstream end 16 of the channel internal 6 relative to a passage section of the internal channel 6. This blocking ratio depends on the shape of the recirculation zone 20. More precisely, it is an aerodynamic element that depends on the dimensional parameters of the dihydrogen injection device 2. The higher the 1 / d ratio, the greater the penetration distance of the internal spiral 14 relative to the diameter, and the higher the value that can be chosen for the rotation ratio S by modifying the geometry of the internal spiral 14. The rotation ratio S must be at least equal to 0.6, and the 1 / D ratio is between 1 and 5. As illustrated in [Fig.4], the downstream end 16 of the internal channel 6 can have varying thicknesses as well as different shapes.
[0043] In a first embodiment illustrated in figure 4A, the downstream end 16 of the internal channel 6 has a straight and longitudinal wall.
[0044] In a second embodiment illustrated in Figure 4B, the downstream end 16 of the internal channel 6 has a flared shape. This downstream end 16 is configured to modify the flow of the internal channel 6 near the wall of the end 16.
[0045] In a third embodiment illustrated in Figure 4C, the downstream end 16 of the internal channel 6 has an outwardly directed buttress effect. This downstream end 16 is configured to modify the flow of the external channel 8 near the wall of the end 16.
[0046] In a fourth embodiment illustrated in Figure 4D, the downstream end 16 of the internal channel 6 has a section that increases downstream. This fourth type of downstream end is configured to promote an increase in the rotation rate S in the internal channel 6 containing the dihydrogen 12. Due to this configuration, the axial velocity is reduced and the tangential velocity is increased, hence the increase in the rotation rate S. This downstream end 16 is configured to modify the flow of the internal channel 6 near the wall of the end 16 as well as the flow of the external channel 8 near the wall of the end 16.
[0047] In a fifth embodiment illustrated in Figure 4E, a thickness corresponding to a transverse dimension of a wall of the internal channel 6 is less or greater than that in the first embodiment.
[0048] In a sixth embodiment illustrated in Figure 4F, the downstream end 16 of the internal channel 6 has a beveled effect. This downstream end 16 is configured to modify the flow of the external channel 8 near the wall of the end 16.
[0049] In a seventh embodiment illustrated in Figure 4G, the downstream end 16 of the internal channel 6 has an inwardly directed butthole effect. This downstream end 16 is configured to modify the flow of the internal channel 6 near the wall of the end 16.
[0050] In an eighth embodiment illustrated in Figure 4H, the downstream end 16 includes a section which narrows downstream. This downstream end 16 is configured to modify the flow of the internal channel 6 near the wall of the end 16 as well as the flow of the external channel 8 near the wall of the end 16.
[0051] As illustrated in [Fig. 1], the downstream end 16 of the internal canal 6 is arranged upstream with respect to the downstream end 24 of the external annular canal 8. The downstream end 24 of the external annular canal 8 is arranged at a distance r from the downstream end 16 of the internal canal 6. This external annular canal 8 has an internal diameter D, such that a ratio D / d with the diameter d of the internal canal 6 is between 3 and 10.
[0052] The external annular channel 8 is configured to receive a second gas comprising air or a mixture of air and dihydrogen. This gas enters the external annular channel through an inlet 26 arranged upstream of said external annular channel.
[0053] A cross-sectional ratio between the internal diameter d of the internal canal 6 and the internal diameter D of the external annular canal 8 depends on: i / of the desired air-dihydrogen mixing ratio, and ii / of the J ratio. In this document, operation in a low dihydrogen regime requires that this D / d ratio be between 2 and 5.
[0054] An external spiral 28 is housed at an upstream end 30 of the external annular channel 8. This external spiral 28 is annular. This external spiral 28 may be radial. This annular external spiral 28 is arranged at a distance L from the downstream end 36 of the external annular channel 8. This distance L is between 2d and 5D. The fuel is then set in rotation at the center by the internal spiral 14, while the air or the non-flammable air-dihydrogen mixture is set in rotation around it by the external spiral 28. This generates a vortex assembly.
[0055] As illustrated in [Fig.5], the external annular canal 8 can have different shapes.
[0056] In a particular embodiment illustrated in Figure 5A, the external annular channel 8 comprises a first annular channel 8 and a second annular channel 32. The first annular channel 8 corresponds to the external annular channel 8. This first annular channel 8 begins at a downstream end 36 of the external spiral 28 and opens upstream of the downstream end 30 of the external spiral 28. The second annular channel 32 has an internal diameter greater than the internal diameter of the first annular channel 8. This second annular channel 32 begins at the downstream end 36 of the external spiral 28 and opens upstream of the downstream end 16 of the internal channel 6.
[0057] In a particular embodiment illustrated in Figure 5B, the downstream end 24 of the external annular channel 8 has a section that increases downstream. This downstream end 24 is configured to modify the flow of the external annular channel 8 near the wall of the end 24.
[0058] In a particular embodiment illustrated in Figure 5C, the downstream end 24 of the external annular channel 8 has a section that narrows downstream. This downstream end 24 is configured to modify the flow of the external annular channel 8 near the wall of the end 24.
[0059] In a particular embodiment illustrated in figure 5D, the distance L can be modified.
[0060] In a particular embodiment illustrated in figure 5E, the external annular channel 8 comprises a single annular channel whose flow from the external channel 8 is rotated by the axial external screw 28.
[0061] In order to generate a rotational movement of the flames, several conditions are met.
[0062] The rotation rate S must be high in the external annular channel 8 and in the internal channel 6. This rotation rate S is equal to or greater than 0.6. Indeed, below 0.6, there is no formation of a recirculation zone with a sufficient depression at the center because the tangential velocity of the dihydrogen flow is not sufficient.
[0063] The external auger 28 also contributes to the maintenance of the recirculation zone. Sext denotes the dimensionless number associated with the rotation rate generated by the external auger 28. Sext must be greater than 0.6. Sext is defined analogously to S, that is, it is a ratio of a tangential velocity to an axial flow velocity of the airflow.
[0064] Stabilization of the flame, whether detached or attached to the downstream end 16 of the internal channel 6, depends on the stretching of a shear layer upstream of the downstream end of the internal channel, to which the flame can attach. To aerodynamically stabilize a flame at a distance from the downstream end of the internal channel, it is necessary to sufficiently stretch one base of the flame in order to extinguish it locally and cause it to stabilize at a distance from the downstream end of the internal channel. The main parameters controlling a local stretch value are the rotation rate of the dihydrogen flow, characterized by the dimensionless number S, the distance r, and a flow velocity ui of the dihydrogen in the internal channel. For a spiral characterized by a rotation rate S greater than 0.6, a flow velocity u of dihydrogen in the internal channel must be greater than a critical value ui>c satisfying the following relationship: P is a pressure in the annular combustion chamber; S is the rotation rate generated by the internal twist 14 of the internal channel 6; Ta is an air temperature in Kelvin in the external channel; P, between 1 and 1.5, is a factor dependent on the type of twist used; - S0=0.6, P0=l bar, Ta0=300 K and ui>c0=18 m / s This relationship is based on three observations. The first observation is that the stretching of the flame that causes it to extinguish increases with pressure (P) and temperature (T0). The second observation clarifies that the flame stretching increases as the rotation rate in the internal channel increases. More precisely, the more the flow is blocked, the higher the radial velocities, and the more the flames are stretched at the mouths. The third observation specifies that for a given rotation rate (S), the blocking rate will also depend on the twisting technology used, hence the power in the formula. The range of values for this, which is between 1 and 1.5, is a good range. Depending on the desired richness and to limit the velocities in the annular channel and therefore the pressure losses, this amounts to choosing D / d between 2 and 5.
[0065] There is an optimal value for the distance r which depends on the internal diameter D of the external annular channel. If the distance r is too large, the recirculation zone 20 becomes unstable. Under such conditions, the distance r should be between 0.05D and 0.5D.
[0066] Depending on the distance r, the mixing will occur sooner or later inside the hydrogen injection device 2 and air, and if this occurs too early, the flame 22 can rise inside the external annular channel 8 between the downstream end 16 of the internal channel and the downstream end 24 of the external annular channel, which is very damaging to the device and the bottom of the combustion chamber 4. The rotation of the flame 22 is therefore configured to prevent the flame 22 from rising into the hydrogen injection device 2. The parameters to be controlled are both the rotation rate S, the rotation rate Sex, and the distance r.
[0067] In the context of this document, the spirals 14, 28 enable the rotation of a first flow relative to a second flow. The integration of the internal spiral 14 into the internal channel 6 creates a recirculation zone 20 for a dihydrogen flow passing through said internal channel 6, preventing the flame from stabilizing at the downstream end of the internal channel. The internal spiral 14 of the internal channel 6 sufficiently rotates the dihydrogen flow 2 to create a recirculation zone penetrating the interior of the internal channel 6. This blocks a portion of the dihydrogen flow along the longitudinal axis x of said internal channel 6, generating significant overvelocities relative to the axial flow velocity near the walls of the internal channel 6.The rotation of the dihydrogen in the internal channel 6 prevents the flame 22 from catching on the downstream ends of the external annular channel 8 by stabilizing it aerodynamically above the internal channel 6. This rotation of the dihydrogen in the internal channel 6 prevents the establishment of a . complex cooling device of the dihydrogen injection device 2.
[0068] This remote flame stabilization 22 facilitates the partial mixing of air with dihydrogen inside the external channel 8 above the downstream end 16 of the internal channel, upstream of the flame 22, and prevents any risk of flame flashback 22 into said internal channel 6 and into the external annular channel 8 upstream of the downstream end 16 of the internal channel 6. This results in hydrogen-depleted combustion in the combustion chamber. This device thus tends to significantly reduce combustion temperatures and nitrogen oxide emissions. It also ensures the integrity of the combustion chamber.
[0069] Positioning the downstream end 16 of the internal channel 6 upstream of the downstream end 24 of the external annular channel 8 optimizes the mixing of dihydrogen and air. This increases the operating range where the flame 22 is detached by moving the dihydrogen introduction zone further back relative to the aerodynamic stabilization zone of the flame.
[0070] The optimization of this injector and its architecture is specifically geared towards the combustion of dihydrogen. Since dihydrogen burns much faster than any other fuel, and in particular kerosene, the rotational speeds between the fuel-supplying injection device 2 and the air-supplying device 2 are not of the same order of magnitude as those used for kerosene. Because kerosene is a liquid, the flow paths of such kerosene injection devices are very small. At the outlet of a kerosene injection device, an outlet channel is on the order of a millimeter or less. Whereas in the present document, the order of magnitude is several millimeters. The operation is therefore very different for a gaseous fuel such as dihydrogen.
Claims
Demands
1. A dihydrogen injection device (2) of longitudinal axis (X) intended to be mounted on an annular bottom of an annular combustion chamber (4) of a turbomachine (1) comprising an internal channel (6) for circulating dihydrogen and an external annular channel (8) for circulating a mixture comprising at least air, the internal channel (6) and the external annular channel (8) being coaxial, an internal spiral (14) being housed in the internal channel (6) and an external spiral (28) being housed in the external annular channel (8), and in which a downstream end (16) of the internal channel (6) is arranged upstream, at a distance r, from a downstream end (24) of the external annular channel (8).
2. Device according to claim 1, wherein the internal channel (6) is a central tubular channel.
3. Device according to any one of the preceding claims, wherein at least the internal twist (14) of the internal channel (6) has a helical shape.
4. Device according to any one of the preceding claims, wherein the internal helix (14) is arranged along the longitudinal axis downstream of the external helix (28).
5. Device according to any one of the preceding claims, wherein a rotation rate S generated by the internal twist (14) of the internal channel (6), defined as a ratio between a tangential velocity and a flow velocity along the longitudinal axis of a dihydrogen flow exiting the internal twist (14), is equal to or greater than 0.
6.
6. Device according to any one of the preceding claims, wherein the internal spiral (14) of the internal channel (6) is arranged upstream, at a distance l, from the downstream end (16) of the internal channel (6).
7. Device according to any one of the preceding claims, wherein an e / d ratio is between 0.05d and 0.5d where e is a thickness of a wall of the internal channel and d is an internal diameter of the internal channel (6).
8. Device according to any one of the preceding claims, wherein the internal channel (6) has an internal diameter d and the external annular channel (8) has an internal diameter D such that a ratio D / d is between 2 and 5.
9. Device according to claims 6 and 7, wherein a ratio / / d is between 1 and 3.
10. Device according to claim 8, wherein the distance r is between 0.05D and 0.5D.
11. Device according to any one of the preceding claims, wherein the external spiral (28) of the external annular channel (8) is arranged at an upstream end (30) of said external annular channel (8), at a distance L from the downstream end (24) of the external annular channel (8).
12. Device according to claims 8 and 11, wherein the distance L is between 2d and 5D.
13. Device according to any one of the preceding claims, wherein the rotation rate S is greater than 0.6, a flow velocity u of di-hydrogen in the internal channel being greater than a critical value ui>c which satisfies the following relationship: u<. <o - \ S ) P» \ Tm / Où : - P est une pression dans la chambre annulaire de combustion ; - S est un taux de rotation généré par la vrille interne (14) du canal interne (6) ; - Ta est une température de l’air en Kelvin dans le canal externe; - compris entre 1 et 1,5 est un facteur dépendant d’un type de vrille utilisée ; - So=O.6, P0=l bar, Ta0=300 K et ui> c0=18 m / s.
14. Device according to any one of the preceding claims, wherein the mixture is air.
15. Assembly comprising the device according to any one of the preceding claims, wherein the internal channel (6), fluidly connected to means for supplying dihydrogen, includes the internal auger (14) configured to rotate said dihydrogen, and the external annular channel (8), fluidly connected to means for supplying air, includes the external auger (28) configured to rotate said air.