DEVICE AND METHOD FOR INJECTING HYDROGEN-AIR MIXTURE FOR TURBOMACHINE BURNER

Abstract

A fuel mixture injection device for the combustion chamber (100) of an aircraft turbomachine turbine, comprising, around a longitudinal axis (X), a central tubular channel (1), a first annular channel (2) around said central channel, and a second annular channel (3) around the first annular channel (2), said channels (1, 2, 3) opening into said combustion chamber at a first lip (9) of said central channel, a second lip (10) of said first annular channel, and an end (11) of the second annular channel, said first annular channel comprising, upstream of said second lip (10), a device for injecting dihydrogen (5, 6, 7) into said first annular channel (2) in an airflow (8) moving along said longitudinal axis of said first annular channel so as to produce a dihydrogen-air mixture flowing towards said combustion chamber. Figure 1

Description

Title of the invention: DEVICE AND METHOD FOR INJECTING A HYDROGEN-AIR MIXTURE FOR A TURBOMACHINE BURNER technical field

[0001] This disclosure relates to the field of injection devices and methods for supplying gas turbines such as aircraft turbomachinery powered by dihydrogen and air. This includes, in particular, civil and military aeronautical applications: helicopters, VTOLs, drones, APUs, turbogenerators, fixed-wing aircraft for recreational, business or commercial aviation, turbojets or turboprops. Previous technique

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

[0003] A principle for micro-mixing air-dihydrogen burners is known. Burners manufactured according to this principle do not guarantee the absence of flashback in the dihydrogen injection device and 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] At the level of injection and combustion, two main technological configurations for hydrogen-air injection systems applied to gas turbines exist, namely lean injection systems, and rich injection systems.

[0005] More generally, it is important to bear in mind that lean-burn fuel systems tend to generate significant thermoacoustic instabilities that can damage these systems, whereas stable combustion is necessary to avoid impairing engine performance. Rich-burn fuel systems, on the other hand, tend to emit more pollutants than lean-burn systems if they are not properly designed.

[0006] The use of hydrogen involves several issues to be taken into consideration at the combustion chamber level:

[0007] Under equivalent thermodynamic conditions in terms of pressure, temperature, and air-fuel ratio, the The adiabatic temperature of the flame from a hydrogen-air combustion is higher than that of the flame from a kerosene-air combustion.

[0008] Similarly, the flame speeds resulting from hydrogen-air combustion are higher than for kerosene-air flames. A high flame speed can lead to flashback problems in injection systems, particularly at the boundary layer level, and cause serious damage to these systems, or even cause safety problems.

[0009] However, the flammability limits of hydrogen are more extensive than those of kerosene and allow a hydrogen-air mixture to be ignited at lower or higher enrichments than for kerosene, which can ultimately allow lower flame temperatures to be achieved than with the use of kerosene.

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

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

[0012] At the burner level, documents GB2502298A and US62675851 describe Chamber geometries are based on the principle of a micromix burner. This type of burner is designed to miniaturize the reaction zone by creating a multitude of diffusion micro-flames up to 4 cm long. The combustion process relies on the injection of hydrogen perpendicular to an airflow that carries the hydrogen (known as jet-in-crossflow). Once the hydrogen is rapidly added to the air, the mixture is injected into the combustion chamber and burned downstream of numerous injection holes. This technology reduces the risk of flashback because there is no premixing before injection. The operability of this type of injector can be limited, as can the thermal resistance of the wall containing the injection holes, which is subjected to high temperatures.

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

[0014] This geometry aims to stagger the air-fuel ratio in the kerosene combustion chamber across several zones: a first zone near the injector outlets with an air-fuel ratio of approximately 1.8, followed by a second mixing zone with very high air content. The purpose of this second zone is to minimize the formation of stoichiometric regions and NOx emissions, and to complete the initial rich combustion. Finally, to cool the combustion gases upstream of the High Pressure Distributor (HPD), additional air injections are provided in a third zone to perform a second lean combustion with an air-fuel ratio of 0.5. Due to the specific characteristics of hydrogen, the RQL geometry optimized for kerosene combustion is no longer suitable and must be redesigned. Summary

[0015] This disclosure relates to a device for injecting a hydrogen-air fuel mixture into the combustion chamber of a turbomachine, designed to stage combustion in order to limit NOx generation and reduce combustion noise. This disclosure also relates to an associated injection method.More specifically, the present disclosure proposes a fuel mixture injection device for the combustion chamber of an aircraft turbomachine turbine, which comprises, around a longitudinal axis, a central tubular channel, a first annular channel around said central channel and a second annular channel around the first annular channel, said channels opening into said combustion chamber at the level of a first lip of said central channel, a second lip of said first annular channel and an end of the second annular channel, said first annular channel comprising, upstream of said second lip, means for injecting dihydrogen into said first annular channel in an airflow moving along said longitudinal axis of said first annular channel so as to produce a dihydrogen-air mixture flowing towards said combustion chamber.

[0016] The first lip can be arranged upstream of the end of the second annular channel, the central channel opening into the combustion chamber at the level of the first lip upstream of the end of the second annular channel.

[0017] The second lip can be arranged upstream of the end of the second annular channel, the first annular channel opening into the combustion chamber at the level of the second lip upstream of said end of the second annular channel.

[0018] The central channel can be provided with a first spiral for rotating a gas passing through it.

[0019] The second annular channel can be provided with a second spiral for rotating a gas passing through it.

[0020] Said means for injecting dihydrogen advantageously comprise a plurality of first radial conduits between an external wall of said first annular channel and an annular feeding tube of said conduits, said annular tube being supplied by one or more second supply conduits of di-hydrogen.

[0021] This disclosure further relates to a method of supplying hydrogen-air combustion in a combustion chamber of an aircraft turbomachine turbine by means of an injection device as described above which comprises an injection of air into said chamber through said tubular central channel, an injection of dihydrogen and air into said chamber through the first annular channel to form a dihydrogen-air premix and an injection of air into said chamber through the second annular channel.

[0022] The dihydrogen-air premix advantageously has a dihydrogen content greater than two.

[0023] The injection of air into the central tubular channel and into the second annular channel is an injection of pure air so as to target an overall injection richness of between 0.3 and 0.5.

[0024] In the case where the device includes a first twist in the central tubular channel, the air is set into rotation in the central channel by said first twist.

[0025] In the case where the device has a second twist in the second annular channel, the air is set into rotation in the second annular channel.

[0026] The process is advantageously such that, after ignition, the injection of the rich hydrogen-air premix creates a first flame front resulting from the rich combustion of the hydrogen-air premix which comes to adhere to the lips of the central tubular channel and the first annular channel, this rich combustion of richness greater than two taking place with a flame front temperature less than 1800 K.

[0027] As a result, the noise generated by the first flame front is reduced and the formation of nitrogen oxides is reduced.

[0028] Advantageously, the injection of air from the central tubular channel and the second annular channel dilutes and confines the burnt gases from the combustion of the rich hydrogen-oxygen premix to form a lean mixture creating a second flame front of lean combustion at a temperature below 1800K.

[0029] As a result, the noise generated by the second flame front is likewise reduced and the formation of nitrogen oxides is also reduced.

[0030] The creation of these two rich and lean flame fronts makes it possible to distribute the thermo-acoustic load from combustion over a larger surface, and therefore to reduce noise pollution from combustion.

[0031] Preferably, said second flame front is turbulent and is not attached to said lips. Brief description of the drawings

[0032] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analysis of the accompanying drawings, on which:

[0033] [Fig-1] represents a schematic longitudinal sectional view of a device injection according to an embodiment;

[0034] [Fig.2] represents a schematic cross-sectional view of means for supplying an annular channel according to a first embodiment;

[0035] [Fig.3] represents the device of [Fig.1] with flame fronts;

[0036] [Fig.4A] represents a cross-section of a variant of means for supplying an annular channel according to a second embodiment;

[0037] [Fig.4B] represents a longitudinal section of the means of the [Fig.4A].

[0038] [Fig.5] represents a schematic longitudinal section view of an injection device according to another embodiment. Description of implementation methods

[0039] Reference is now made to [Fig.1] which represents a cross-section of a fuel mixture injection device made according to the principle of the present disclosure by a plane comprising a longitudinal axis X of the device.

[0040] The device comprises a central tubular channel 1 centered on the X axis, a first annular channel 2 around said central annular channel and a second annular channel 3 around the first annular channel 2.

[0041] Said channels 1, 2, 3 open into a combustion chamber 100. The central tubular channel has a first circular lip 9 surrounded by the first annular channel at the level of an outlet plane 4 of said central channel. The first annular channel has a second circular lip 10, also at the level of the outlet plane 4. The second circular lip is surrounded by the second annular channel, and the first and second lips are recessed by a height h relative to the outlet plane 11 of the second annular channel. Thus, the outlets of the central tubular channel and the first annular channel are upstream of the outlet of the second annular channel.

[0042] The first annular channel includes, upstream of said second lip 10, a device for injecting dihydrogen into an airflow 8 moving along the longitudinal axis so as to create a dihydrogen-air mixture flowing towards said combustion chamber. To inject the dihydrogen, the means include radial conduits 5 shown in cross-section in [Fig. 2] which open into the outer wall of the first annular channel 2. For illustrative purposes, the ratio of the distance from the outlet to the diameter of the first channel 2 can be between 1 and 10, more preferably between 1 and 5.

[0043] In [Fig.2], the dihydrogen injections are of the "jet-in-cross-flow" type, that is to say to say in French radial injections of dihydrogen into an axial jet of air, in order to obtain a rapid premixing, over a minimized axial length, of the dihydrogen-air premix 15 exiting the first annular channel 2.

[0044] These radial conduits are supplied, as shown in the example, by an annular tube 6, itself supplied by one or more secondary conduits 7 for the delivery of dihydrogen from a pump or a pressure vessel (not shown). The number of these primary conduits is, for example, from 10 to 20, and for example, on the order of 16 for good distribution of the dihydrogen.

[0045] Alternatively, according to [Fig. 4A] and [Fig. 4B], respectively cross-section and longitudinal section on one side of the X-axis of the device, the hydrogen injection means comprise first conduits 51 supplied by an annular tube 61 through sub-conduits 52, but the hydrogen is mixed with air in hollow sectors 21 supplying the first annular channel from below, opposite the outlet of said channel into the combustion chamber. In this example, the conduits 51 each supply two sectors.

[0046] According to this example, four hollow sectors, each supplied by four first conduits 51 in which the dihydrogen-air mixture takes place, are present under the first annular channel 2.

[0047] According to this embodiment, the injection process is improved by the addition of an air-swirling device 8, consisting of several hollow blades, four blades in [Fig. 4A], through which the dihydrogen circulates. The latter is injected by jet-in-cross-flow injections 51 into the blades of the swirling device to optimize the mixing process.

[0048] The device of this disclosure enables staged hydrogen combustion to bypass the nitrogen oxide formation zone by burning a rich hydrogen-air premix in a first zone and burning the residual gases in a second, lean zone. The staged combustion concept allows for a wider injector operating range than a lean-burn hydrogen injection strategy, where a lean premix is ​​burned directly in the chamber and aims to reduce NOx formation.

[0049] The risk of flashback is limited with rich combustion because thermal-diffusive instabilities are not present on the first flame front. The flame speed is therefore not accelerated by these instabilities. Furthermore, the layering of richness levels prevents the formation of a stoichiometric flame front because the hydrogen is either premixed rich or contaminated by combustion gases. This has the effect of reducing the flame front speed, which is highly dependent on the composition of the gases to be burned.

[0050] Stabilization of two flame fronts 17 and 18, front 17 attached to lips 9 and 10 of the injector for the rich flame and 18 detached front for the lean flame, allows to divide the thermo-acoustic loads related to the combustion: the noise generated by the combustion is distributed over two flame fronts, that is to say over a larger surface than in the case where a single flame front is generated.

[0051] The integrity of the combustion chamber is also ensured because, by carrying out combustion at high and low air-fuel ratios, the flame temperatures are lower than when combustion is carried out under stoichiometric conditions. Potential flame fronts originating from stoichiometric zones that might be present in reality will not adhere to the injector lips, thus limiting injector damage.

[0052] By significantly increasing the surface area of ​​the flame front via the injection of the hydrogen-rich air premix into the first annular channel 2, the length of the flame is reduced, which makes it possible to create combustion chambers with a reduced footprint compared to injection into a central tubular channel.

[0053] With reference to Figures 3 and 4B, in order to promote the interaction between the air of the channel 16 and the premix flame 17, a retraction of the lip 10 is provided relative to the end of the second annular channel, a retraction noted h on the [Fig.1] to improve the interaction between the jet 16 exiting the second annular channel and the jet 15 exiting the first annular channel.

[0054] In the context of operation under typical conditions of a turboprop, the rich zone richness can in particular be fixed around 4 and the overall richness fixed between 0.17 and 0.31 depending on the operating points of the turboprop.

[0055] The size of such a device for a combustion chamber of an aircraft turboprop turbine is on the order of 30 mm to 40 mm.

[0056] Fig. 5 represents a variant of the injection system applied to the entire bottom of the aeronautical combustion chamber with the shaft in the center where the central tubular channel is made up of a third annular channel around the shaft 20, each of the channels being provided with a spiral 12, 13, 19, the annular flame fronts surrounding the shaft 20.

[0057] This disclosure therefore relates to a pre-mixed tri-coaxial hydrogen injection system with air for an aeronautical or land-based gas turbine, based on staged combustion: a. Combustion of the high-rich hydrogen-air premix takes place in a first region which generates a first annular flame front attached to the lips 9, 10 of the injector, first inner lip 9 and second outer lip 10 of the annular injection channel of the dihydrogen-air mixture; b. The combustion products are then rapidly mixed via central and peripheral air injection to be burned in a second region in generating a second detached flame front.

[0058] This system allows, in particular: a. To obtain aerodynamically stabilized flames over a wide operating range, b. To achieve combustion with very low nitrogen oxide emissions, c. To avoid the risk of a flashback from the second flame front, d. To reduce noise pollution associated with hydrogen combustion, e. To obtain short flames with a distribution of thermal loads, f. To improve the integrity and lifespan of the injector.

[0059] The device of the invention is thus associated with a method of supplying a hydrogen-air combustion in a combustion chamber of an aircraft turbomachine turbine which includes an injection of air 14 into said chamber through said tubular central channel 1, an injection of dihydrogen 15a and air 8 into said chamber through the first annular channel 2 to form a dihydrogen-air premix 5 and an injection of air 16 into said chamber through the second annular channel 3.

[0060] The dihydrogen-air premix 15 can then have a dihydrogen richness greater than two, while the air injection 14 into the central tubular channel 1 and into the second annular channel 3 is a pure air injection calibrated so as to target an overall injection richness between 0.3 and 0.5.

[0061] According to the example of [Fig.3], the device having a first twist 12 in the central tubular channel 1, the air 14 is set in rotation in this central channel 1 by this first twist, whereas the device having a second twist 13 in the second annular channel, the air 4 is set in rotation in the second annular channel.

[0062] After ignition, the injection of the rich hydrogen-air premix 15 creates a first flame front 17, this flame being from the rich combustion of the hydrogen-air premix which comes to stick to the lips 9 and 10 of the central tubular channel 1 and of the first annular channel 2.

[0063] This rich combustion, with a richness greater than two, takes place with a flame front temperature below 1800 K, thus limiting NOx emissions. Air injection from the central tubular channel 1 and the second annular channel 3 dilutes and confines the burnt gases from the combustion of the rich hydrogen-oxygen premix to form a lean mixture, creating a second flame front 18 of lean combustion at a temperature below 1800 K, again limiting NOx emissions. This second flame front 18, which is also turbulent, is not attached to the lips 9, 10 of the central tubular channel 1 and the first annular channel 2.

[0064] The device and method of this disclosure are efficient while limiting NOx emissions.

[0065] The invention which is the subject of the following claims is not limited to the description which preceding and in particular the shape of the lips and the exit of the second annular canal can be of various shapes such as straight, flared, beveled, narrow and of various thicknesses.

Claims

Demands

1. A fuel-air-hydrogen mixture injection device for the combustion chamber (100) of an aircraft turbomachine turbine, characterized in that it comprises, around a longitudinal axis (X), a central tubular channel (1), a first annular channel (2) around said central channel and a second annular channel (3) around the first annular channel (2), said channels (1, 2, 3) being configured so as to open into said combustion chamber at a first lip (9) of said central channel, a second lip (10) of said first annular channel and an end (11) of the second annular channel, said first annular channel comprising, upstream of said second lip (10), a hydrogen injection device (5, 6,7) in said first annular channel (2) in an air flow (8) moving along said longitudinal axis of said first annular channel so as to produce a dihydrogen-air mixture flowing between said first lip and said second lip.

2. Injection device according to claim 1, wherein the first lip (9) is disposed upstream of the end of the second annular channel, the central channel (1) opening into the combustion chamber (100) at the level of the first lip (9) upstream of the end (11) of the second annular channel and / or wherein the second lip (10) is disposed upstream of the end of the second annular channel, the first annular channel opening into the combustion chamber at the level of the second lip (10) upstream of said end (11) of the second annular channel.

3. Injection device according to claim 1 or 2, wherein the central channel (1) is provided with a first spiral (12) for rotating a gas passing through it.

4. Injection device according to any one of the preceding claims, wherein the second annular channel (3) is provided with a second spiral (13) for rotating the gas passing through it.

5. Injection device according to any one of the preceding claims, wherein said dihydrogen injection means (5, 6, 7) comprise a plurality of first conduits (5, 5) between an outer wall of said first annular channel (2) and an annular tube (6, 6) for supplying said conduits, said annular tube being supplied by one or more second di- hydrogen.

6. Method of supplying hydrogen-air combustion in a combustion chamber of an aircraft turbomachine turbine by means of an injection device according to any one of the preceding claims characterized in that it comprises an injection of air (14) into said combustion chamber through said tubular central channel (1), an injection of dihydrogen (15a) and air (8) into said combustion chamber through the first annular channel (2) to form a dihydrogen-air premix (15) and an injection of air (16) into said combustion chamber through the second annular channel (3).

7. Method of feeding a hydrogen-air combustion according to claim 6 wherein the dihydrogen-air premix (15) has a dihydrogen content greater than two.

8. Method of feeding a hydrogen-air combustion according to claim 7 wherein the injection of air (14) into the central tubular channel (1) and into the second annular channel (3) is an injection of pure air so as to target an overall injection richness between 0.3 and 0.

5.

9. Method of feeding a hydrogen-air combustion according to any one of claims 6 to 8 wherein the device comprising a first helix (12) in the tubular central channel, the air (14) is set in rotation in the central channel (1) by said first helix and / or wherein the device comprising a second helix (13) in the second annular channel, the air (4) is set in rotation in the second annular channel.

10. A method for feeding a hydrogen-air combustion according to any one of claims 6 to 9, wherein after ignition, the injection of the rich hydrogen-air premix (15) creates a first flame front (17) from the rich combustion of the hydrogen-air premix, which adheres to the lips (9, 10) of the central tubular channel (1) and the first annular channel (2), this rich combustion, with an enrichment ratio greater than two, occurring at a flame front temperature below 1800 K, and wherein the injection of air from the central tubular channel (1) and the second annular channel (3) dilutes and confines the burnt gases from the combustion of the rich hydrogen-oxygen premix to form a lean mixture, creating a second flame front (18) of lean combustion at a temperature below 1800 K, said second flame front (18) being turbulent and not attached to the said lips (9, 10).

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