Apparatus and method for injecting hydrogen-air mixture for turbine engine combustor

Abstract

A device for injecting a combustible mixture for a combustion chamber (100) of a turbine of an aircraft turbine engine, the device comprising, around a longitudinal axis (X), a tubular central channel (1), a first annular channel (2) surrounding the central channel and a second annular channel (3) surrounding the first annular channel (2), the channels (1, 2, 3) open into the combustion chamber at a first lip (9) of the central channel, at a second lip (10) of the first annular channel and at an end (11) of the second annular channel, the first annular channel comprises, upstream of the second lip (10), means for injecting hydrogen (5, 6, 7) into the first annular channel (2) in a gas flow (8) passing along the longitudinal axis of the first annular channel in order to produce a hydrogen-air mixture flowing to the combustion chamber.

Description

Technical Field

[0001] The present disclosure relates to the field of injection devices and methods for feeding gas turbines, such as aircraft turbine engines powered by hydrogen and air. This includes in particular civil and military aviation applications: helicopters, VTOL, drones, APUs, turbogenerators, fixed-wing aircraft for leisure, business or commercial aviation, turbojets or turboprops. Background Art

[0002] The field of propulsion, and in particular aviation, is facing major environmental challenges. There is an increasing interest in using hydrogen instead of kerosene for combustion, as hydrogen combustion will avoid pollutant carbon emissions such as carbon dioxide, carbon monoxide, unburned hydrocarbons or fine particles and smog.

[0003] The principle of burners based on the combustion of a micromix of air and hydrogen is known. Burners implemented according to this principle do not guarantee the absence of flashback in the hydrogen injection device and have complex geometries. Such burners have high production costs, high pressure drop and are specific to a given combustion chamber architecture.

[0004] In injection and combustion, there are two main technical configurations of hydrogen-air injection systems applied to gas turbines, namely lean injection systems and rich injection systems.

[0005] More generally, it is important to remember that lean burn feed processes tend to produce significant thermoacoustic instabilities that can damage these systems, and stable combustion is necessary to avoid altered engine performance. For rich burn feed processes, if not properly sized, these processes tend to emit more pollutants than lean burn processes.

[0006] The use of hydrogen implies several issues to be considered in the combustion chamber:

[0007] Under isothermal conditions of pressure, temperature, and jet richness, the adiabatic temperature of a hydrogen-air combustion flame is higher than that of a kerosene-air combustion flame. However, the flammability limits of hydrogen are wider than those of kerosene and allow the mixture to ignite at lower or higher richness than kerosene, which can ultimately allow lower flame temperatures than with kerosene.

[0008] Similarly, the flame speed of hydrogen-air combustion is higher than that of kerosene-air flames. High flame speeds can cause flashback problems in injection systems, especially at the boundary layer, and can cause severe damage to these systems.

[0009] However, the flammability limits of hydrogen are wider than those of kerosene and allow hydrogen-air mixtures to ignite at lower or higher richnesses than kerosene, which may ultimately allow lower flame temperatures than using kerosene.

[0010] Finally, the combustion of hydrogen with air tends to emit more noise than conventional kerosene combustion, and thus in the case of aviation use could generate significant noise pollution at airports.

[0011] More generally, it is important to remember that lean combustion systems tend to produce significant thermoacoustic instabilities that can damage these systems. Stable combustion is necessary to avoid altering engine performance.

[0012] It is therefore desirable to reduce combustion temperatures, reduce the acoustic waves generated by the combustion, and limit the formation of nitrogen oxides in order to reduce both noise pollution and air pollution during turbine operation.

[0013] For burners, documents GB2502298A and US62675851 describe chamber geometries based on the principle of micro-mixing burners. This type of burner is designed to miniaturize the reaction zone by producing multiple micro-diffusion flames up to 4 cm. The combustion process is based on injecting hydrogen perpendicular to the gas flow (called jet in cross flow) carrying hydrogen. Once the rapid addition of hydrogen to the air is achieved, the mixture is injected into the combustion chamber and burns downstream of multiple injection holes. This technology reduces the risk of flashback because there is no premixing before injection. The operability of this type of injector and the thermal resistance of the wall containing the injection hole subjected to high temperature conditions may be limited.

[0014] In the context of burners using kerosene, the document "Advanced Combustion Chamber Systems for Stationary Gas Turbine Engines, Phase I Review and Preliminary Evaluation, Volume I" (SAMosier, RM Pierce, Contract 68-02-2136, FR-11405, Final Report, U.S. Environmental Protection Agency, 1980) proposed the RQL geometry, which is an acronym used in this field for "Rich Burn-Quick Mixing-Lean Burn".

[0015] This geometry aims to grade the richness in the kerosene combustion chamber into several zones: a first zone close to the injector outlet, where the richness is about 1.8, followed by a second zone for very intensive mixing with air, where the goal is to minimize the formation of the stoichiometric zone and the formation of NOx and to complete the rich combustion upstream. Finally, in order to cool the combustion gases upstream of the "high pressure distributor" HPD, an additional injection of air is planned in the third zone for a second lean combustion at a richness of 0.5. Due to the specificity of hydrogen, the RQL geometry optimized for kerosene combustion is no longer valid and must be redesigned. Summary of the invention

[0016] To this end, the disclosure relates to a device for injecting a combustible hydrogen-air mixture into a combustion chamber of a turbine engine, intended for staged combustion in order to limit the production of NOx and to limit the noise emitted by the combustion. The disclosure further relates to an associated injection method.

[0017] More specifically, the present disclosure proposes a device for injecting a combustible mixture into a combustion chamber of a turbine of an aircraft turbine engine, the device comprising, around a longitudinal axis, a tubular central channel, a first annular channel surrounding the central channel, and a second annular channel surrounding the first annular channel, the channels being configured to open into the combustion chamber at a first lip of the central channel, at a second lip of the first annular channel, and at an end of the second annular channel, the first annular channel comprising, upstream of the second lip, a member for injecting hydrogen into the first annular channel in an airflow moving along the longitudinal axis of the first annular channel so as to produce a hydrogen-air mixture flowing between the first lip and the second lip.

[0018] The first lip may be arranged upstream of the end of the second annular channel, the central channel opening into the combustion chamber at the first lip upstream of the end of the second annular channel.

[0019] The second lip may be arranged upstream of the end of the second annular channel, the first annular channel opening into the combustion chamber at the second lip upstream of the end of the second annular channel.

[0020] The central passage may be provided with a first swirler for swirling the gas passing therethrough.

[0021] The second annular passage may be provided with a second swirler for swirling the gas passing therethrough.

[0022] Said means for injecting hydrogen advantageously comprise a plurality of first radial ducts between the outer wall of said first annular channel and an annular duct for supplying said duct, said annular duct being supplied by one or more second ducts for introducing hydrogen.

[0023] The present disclosure further relates to a method for feeding hydrogen-air combustion in a combustion chamber of a turbine of an aircraft turbine engine by means of an injection device as described above, the method comprising: injecting air into the combustion chamber via a tubular central channel; injecting hydrogen and air into the combustion chamber via a first annular channel to form a hydrogen-air premixture; and injecting air into the combustion chamber via a second annular channel.

[0024] The hydrogen-air premixture advantageously has a hydrogen richness greater than two.

[0025] The injection of air into the tubular central passage and the second annular passage is an injection of pure air, aiming for a total injection richness between 0.3 and 0.5.

[0026] In case the device comprises a first swirler in the tubular central channel, the air is swirled in the central channel by means of said first swirler.

[0027] In case the arrangement comprises a second swirler in the second annular channel, the air rotates in the second annular channel.

[0028] The method advantageously causes the injection of a rich hydrogen-air premixture to produce, after ignition, a first flame front produced by rich combustion of the hydrogen-air premixture, said first flame front being attached to the lips of the tubular central passage and the first annular passage, said rich combustion with a richness greater than 2 being carried out at a flame front temperature less than 1800K.

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

[0030] Advantageously, injecting air from the tubular central passage and from the second annular passage dilutes and confines the combustion gases resulting from the combustion of the rich hydrogen-oxygen premixture to form a lean mixture, thereby producing a second flame front from the lean combustion at a temperature of less than 1800K.

[0031] As a result, the noise generated by the second flame front is similarly reduced, and the formation of nitrogen oxides is also reduced.

[0032] The creation of these two flame fronts (a rich flame front and a lean flame front) makes it possible to distribute the thermoacoustic load generated by the combustion over a larger surface area and thus reduce the noise pollution generated by the combustion.

[0033] Preferably, the second flame front is turbulent and does not adhere to the lip. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Other features, details and advantages will become apparent upon reading the following detailed description and upon examining the accompanying drawings, in which:

[0035] [ Figure 1 ] shows a schematic longitudinal cross-sectional view of an injection device according to one embodiment;

[0036] [ Figure 2 ] shows a schematic cross-sectional view of a component for supplying an annular channel according to a first embodiment;

[0037] [ Figure 3 ] shows a flame front Figure 1 Devices;

[0038] [ Figure 4A ] shows a cross section of a variant of the member for supplying the annular channel according to the second embodiment;

[0039] [ Figure 4B ] shows Figure 4A Longitudinal section of a component.

[0040] [ Figure 5 ] shows a schematic longitudinal sectional view of an injection device according to another embodiment. DETAILED DESCRIPTION

[0041] Reference now Figure 1 , Figure 1 A cross-sectional view of a device for injecting a combustible mixture, implemented according to the principles of the present disclosure, is shown in a plane including the longitudinal axis X of the device.

[0042] The device comprises a tubular central channel 1 centered on an axis X, a first annular channel 2 surrounding the annular central channel and a second annular channel 3 surrounding the first annular channel 2 .

[0043] The channels 1, 2, 3 open into a combustion chamber 100. The tubular central channel comprises a first circular lip 9 surrounded by a first annular channel at the outlet plane 4 of the central channel, the first annular channel comprising a second circular lip 10 also at the outlet plane 4. The second circular lip is surrounded by a second annular channel, and the first and second lips are set back by a height h relative to the plane of the outlet 11 of the second annular channel. Thus, the outlets of the tubular central channel and of the first annular channel are upstream of the outlet of the second annular channel.

[0044] The first annular channel comprises, upstream of the second lip 10, means for injecting hydrogen into the gas flow 8 moving along the longitudinal axis in order to produce a hydrogen-air mixture flowing towards the combustion chamber. For injecting hydrogen, the components comprise Figure 2 The radial duct 5 shown in the cross-sectional view in FIG. 1 opens into the outer wall of the first annular channel 2. For clarity, the ratio of the distance to the outlet to the diameter of the first channel 2 may be between 1 and 10, more preferably between 1 and 5.

[0045] exist Figure 2 In the embodiment, the injection of hydrogen is a "jet in cross-flow" injection, i.e. the hydrogen is radially injected into the axial air jet so as to obtain a fast premixing of the hydrogen-air premix 15 leaving the first annular channel 2 over a minimum axial length.

[0046] According to the example, these radial ducts are supplied by an annular duct 6, which is itself supplied by one or more second ducts 7, which introduce hydrogen from a pressurized tank or a pump (not shown). The number of first ducts is, for example, 10 to 20, and for example about 16, in order to obtain a good hydrogen distribution.

[0047] As a variant, according to the cross-sections on one side of the axis X of the device and the longitudinal cross-sections respectively Figure 4A and Figure 4B , the means for hydrogen injection comprise a first duct 51 supplied via an annular tube 61 through a sub-duct 52, but the hydrogen is mixed with air in the hollow partition 21 which supplies the first annular channel from below at the other end of said channel relative to its outlet to the combustion chamber. In this example, the ducts 51 each supply two partitions.

[0048] According to this example, below the first annular channel 2 there are four hollow sectors, each supplied by four first ducts 51 in which the hydrogen-air mixing is carried out.

[0049] According to this embodiment, the injection process is improved by adding an air swirl device 8 (swirler) consisting of several hollow blades ( Figure 4A The hydrogen is injected into the cyclone blades by means of a jet injection 51 in cross flow to optimize the mixing process.

[0050] The apparatus of the present disclosure allows for staged combustion of hydrogen so as to bypass the nitrogen oxide formation zone via combustion of a rich hydrogen-air premix in a first zone and combustion of residual gas in a second lean zone. The concept of staged combustion allows for a wider range of injector operability than strategies for lean burn hydrogen injection where a lean premix is ​​burned directly in the combustion chamber and is intended to reduce NOx formation.

[0051] The risk of flashback is limited by rich combustion, since there are no diffusion thermal instabilities in the first flame front. Therefore, the flame speed is not accelerated by instabilities. In addition, the richness grading avoids the formation of a stoichiometric flame front, because hydrogen is a rich premix or is contaminated by the combustion gases. This has the effect of reducing the speed of the flame front, which is highly dependent on the composition of the gas to be burned.

[0052] The stabilization of the two flame fronts 17 and 18 makes it possible to divide the thermoacoustic loads associated with the combustion: the noise generated by the combustion is distributed over the two flame fronts, i.e. over a larger surface area than in the case of the generation of a single flame front, the front 17 being attached to the lips 9 and 10 of the injector for a rich flame and the front 18 being separated for a lean flame.

[0053] The integrity of the injector is also ensured because by burning at high and low richnesses, the flame temperature is lower than when burning at stoichiometric conditions. Potential flame fronts from the stoichiometric region that may exist will not attach to the lip of the injector, thereby reducing damage to the injector.

[0054] By significantly increasing the surface area of ​​the flame front by injecting a hydrogen-rich air premixture into the first annular channel 2, the length of the flame is reduced, which makes it possible to create a combustion chamber of reduced size compared to injection into the central tubular channel.

[0055] refer to Figure 3 and 4B In order to promote the interaction between the air in the channel 16 and the premixed flame 17, the lip 10 is moved back relative to the end of the second annular channel (hereafter moved to Figure 1 In the figure, denoted h), in order to improve the interaction between the jet 16 leaving the second annular channel and the jet 15 leaving the first annular channel.

[0056] In the case of operation under typical conditions of a turboprop engine, the richness of the rich zone may in particular be fixed at about 4, and the total richness fixed at between 0.17 and 0.31, depending on the operating point of the turboprop engine.

[0057] The dimensions of such a device for the combustion chamber of a turbine of an aircraft turbopropeller are approximately 30 to 40 mm.

[0058] Figure 5 A variant of the injection system is shown applied to an assembly comprising at the bottom of an aviation combustion chamber with a shaft in the center, wherein a tubular central channel 1a is composed of a third annular channel around the shaft 20, each channel being provided with a swirler 12, 13, 19, around which an annular flame front surrounds the shaft 20.

[0059] The present disclosure thus relates to a three-coaxial system for the injection of hydrogen premixed with air based on staged combustion for aviation or terrestrial gas turbines:

[0060] a. The combustion of the hydrogen-air premixture at high richness occurs in the first zone, which produces a first annular flame front, which is attached to the lips 9, 10 of the injector, i.e. the first inner lip 9 and the second outer lip 10 of the annular channel for injecting the hydrogen-air mixture;

[0061] b. The combustion products then mix rapidly via the central and peripheral injections of air to burn in the second zone, creating a second unattached flame front.

[0062] The system specifically makes it possible to:

[0063] a. Obtain an aerodynamically stable flame over a wide operating range,

[0064] b. Achieve combustion with extremely low nitrogen oxide emissions,

[0065] c. Avoid the risk of flashback of the second flame front,

[0066] d. To reduce noise pollution associated with hydrogen combustion,

[0067] e. Obtaining a short flame with a heat load distribution,

[0068] f. Improve the integrity and service life of the injector.

[0069] The device of the invention is therefore associated with a method for feeding hydrogen-air combustion in a combustion chamber of a turbine of an aircraft turbine engine, said method comprising: injecting air 14 into the chamber via a tubular central channel 1; injecting hydrogen 15a and air 8 into the chamber via a first annular channel 2 to form a hydrogen-air premixture 5; and injecting air 16 into the chamber via a second annular channel 3.

[0070] The hydrogen-air premix 15 may then have a hydrogen richness greater than 2, while the injection of air 14 into the tubular central passage 1 and the second annular passage 3 is an injection of pure air with a calibration target of a total injection richness between 0.3 and 0.5.

[0071] according to Figure 3 In the example of the device, the device comprises a first swirler 12 in a tubular central channel 1, through which the air 14 is swirled in the central channel 1, and a second swirler 13 in a second annular channel, in which the air 4 is swirled.

[0072] After ignition, the injection of the rich hydrogen-air premix 15 generates a first flame front 17 resulting from the rich combustion of the hydrogen-air premix adhering to the lips 9 and 10 of the tubular central passage 1 and the first annular passage 2 .

[0073] This rich combustion with a richness greater than 2 is carried out at a flame front temperature below 1800 K, thereby reducing NOx emissions. The injection of air from the tubular central passage 1 and from the second annular passage 3 dilutes and confines the combustion gases resulting from the combustion of the rich hydrogen-oxygen premixture to form a lean mixture, thereby producing a second lean combustion flame front 18 at a temperature less than 1800 K, thereby also reducing NOx emissions. The second flame front 18, which is also turbulent, does not adhere to the lips 9, 10 of the tubular central passage 1 and the first annular passage 2.

[0074] The apparatus and methods of the present disclosure are highly efficient while limiting NOx emissions.

[0075] The invention, which is the subject of the appended claims, is not limited to the preceding description and in particular the shape of the lip and the outlet of the second annular channel may have various shapes, for example straight, flared, inclined, narrowed and of various thicknesses.

Claims

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

2. The spraying device according to claim 1, characterized in that The first lip (9) is arranged upstream of the end of the second annular channel, and the central channel (1) opens into the combustion chamber (100) at the first lip (9) upstream of the end (11) of the second annular channel, and / or wherein the second lip (10) is arranged upstream of the end of the second annular channel, and the first annular channel opens into the combustion chamber at the second lip (10) upstream of the end (11) of the second annular channel.

3. The spraying device according to claim 1 or 2, characterized in that: The central passage (1) is provided with a first swirler (12) for swirling the gas passing therethrough.

4. Spraying device according to any one of the preceding claims, characterized in that The second annular passage (3) is provided with a second swirler (13) for swirling the gas passing therethrough.

5. Spraying device according to any one of the preceding claims, characterized in that The means for injecting hydrogen (5, 6, 7) comprise a plurality of first ducts (5, 51) between the outer wall of the first annular channel (2) and an annular duct (6, 61) for supplying said ducts, said annular duct being supplied by one or more second ducts (7) for introducing hydrogen.

6. A method for feeding hydrogen-air combustion in a combustion chamber of a turbine of an aircraft turbine engine, said method being implemented by means of an injection device according to any one of the preceding claims, characterized in that The method comprises: injecting air (14) into the combustion chamber via the tubular central passage (1); injecting hydrogen (15a) and air (8) into the combustion chamber via the first annular passage (2) to form a hydrogen-air premixture (15); and injecting air (16) into the combustion chamber via the second annular passage (3).

7. The method for feeding hydrogen-air combustion according to claim 6, characterized in that The hydrogen-air premixture (15) has a hydrogen richness greater than 2.

8. The method for feeding hydrogen-air combustion according to claim 7, characterized in that The injection of air (14) into the tubular central passage (1) and the second annular passage (3) is an injection of pure air, targeting a total injection richness between 0.3 and 0.

5.

9. A method for feeding hydrogen-air combustion according to any one of claims 6 to 8, characterized in that The device comprises a first swirler (12) in the tubular central channel, through which the air (14) is swirled in the central channel (1), and / or wherein the device comprises a second swirler (13) in the second annular channel, in which the air (4) is swirled.

10. A method for feeding hydrogen-air combustion according to any one of claims 6 to 9, characterized in that After ignition, the injection of the rich hydrogen-air premixture (15) produces a first flame front (17) produced by rich combustion of the hydrogen-air premixture, the first flame front (17) being attached to the lips (9, 10) of the tubular central passage (1) and the first annular passage (2), such rich combustion with a richness greater than 2 being carried out at a flame front temperature less than 1800K, and wherein the injection of air from the tubular central passage (1) and from the second annular passage (3) dilutes and restricts the combustion gases produced by the combustion of the rich hydrogen-oxygen premixture to form a lean mixture, thereby producing a second flame front (18) from the lean combustion at a temperature less than 1800K, the second flame front (18) being turbulent and not attached to the lips (9, 10).

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