Fuel mixer

Abstract

A mixer for mixing fuel and air in a combustor of a turbine engine. The mixer includes a central body having a central passage and a central axis. The mixer includes a plurality of tubes radially positioned around the central axis and circumferentially positioned around the periphery of the mixer. Each tube of the mixer includes an opposing opening and a tangential opening. Each tube of the mixer includes a cylindrical internal mixing passage configured to receive an air flow and a fuel flow from the opposing opening and the tangential opening. The opposing opening is configured to diffuse the fuel flow laterally, and the tangential opening is configured to diffuse the fuel flow tangentially.

Description

Technical Field

[0001] The preferred embodiments relate to fuel mixers. More particularly, the preferred embodiments relate to hydrogen fuel micro mixers having constrained tube clusters. Background Art

[0002] Currently, gas turbine engines cannot burn high hydrogen blended fuels. The mixers of gas turbine engines have low velocity pockets within the mixer, causing flashback (e.g., flames returning to the mixer) and flame holding issues (e.g., flames within the mixer), and in addition, the fuel-air needs to be fully mixed before leaving the mixer to ensure low NOx emissions. Summary of the invention

[0003] According to an embodiment, a mixer for mixing fuel and air in a combustor of a gas turbine engine, the mixer comprising: a central body having a central passage and a central axis; a plurality of tubes radially positioned about the central axis and circumferentially positioned about the periphery of the mixer, each tube comprising: a first opening, the first opening being angled relative to the central axis and being configured to introduce a first air flow; a second opening, the second opening being in an opposed relationship to the first opening, the second opening being angled relative to the central axis and being configured to introduce a second air flow; a tangential opening, the tangential opening being at a rearward position of the first opening and the second opening, the tangential opening being angled relative to the central axis and being configured to introduce a tangential air flow; and a cylindrical internal mixing passage, the cylindrical internal mixing passage being configured to receive a first air flow, a second air flow, a tangential air flow, and a fuel flow, wherein the first air flow and the second air flow are configured as transverse diffusion fuel flows, and the tangential air flow is configured as a tangential diffusion fuel flow, and wherein a fuel-air mixture is present at an outlet of each of the plurality of tubes.

[0004] According to an embodiment, a mixer array for a turbine engine includes: a plurality of mixers, each mixer having a central body and a plurality of microtubes positioned circumferentially around the central body, wherein each of the plurality of microtubes includes a cylindrical mixing channel, an opposed air flow generated by air flows through opposed openings in the cylindrical mixing channel, and a tangential air flow generated by air flows through tangential openings in the cylindrical mixing channel, wherein each of the plurality of microtubes is configured to mix a fuel flow with the opposed air flow and the tangential air flow, and wherein the opposed air flow is configured as a transverse diffusion fuel flow, and the tangential air flow is configured as a tangential diffusion fuel flow.

[0005] According to an embodiment, a method for mixing fuel in a gas turbine engine includes: injecting natural gas fuel into the gas turbine engine to start operation of the gas turbine engine; after the start-up operation, injecting a certain volume percentage of hydrogen fuel into a mixer together with the natural gas to provide a fuel mixture to the gas turbine engine; and increasing the volume percentage of the hydrogen fuel to a range of 70% to 100% of the fuel mixture, wherein the mixer provides opposing air flows and tangential air flows to mix the fuel mixture flow and reduce low-speed pockets in the mixer, thereby reducing emissions.

[0006] Additional features, advantages and embodiments of the preferred embodiments are set forth or apparent by considering the following detailed description, drawings and claims. In addition, it should be understood that the above summary and the following detailed description of the preferred embodiments are exemplary and intended to provide further explanation without limiting the scope of the claimed embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The foregoing and other features and advantages will become apparent from the following more particular description of various exemplary embodiments, as illustrated in the drawings, in which like reference numerals generally indicate identical, functionally similar, and / or structurally similar elements.

[0008] Figure 1 A schematic cross-sectional view of a conventional mixer according to an embodiment of the present disclosure is shown.

[0009] Figure 2A A schematic cross-sectional view of a conventional mixer according to an embodiment of the present disclosure is shown.

[0010] Figure 2B The embodiment according to the present disclosure is shown Figure 2A Schematic perspective cross-sectional view of a conventional mixer.

[0011] Figure 3 A schematic diagram of a mixer array according to an embodiment of the present disclosure is shown.

[0012] Figure 4A A schematic cross-sectional view of a mixer according to an embodiment of the present disclosure is shown.

[0013] Figure 4B The embodiment according to the present disclosure is shown Figure 4A Schematic diagram of an end view of the outlet of a mixer.

[0014] Figure 4C The embodiment according to the present disclosure is shown Figure 4A Schematic diagram of a mixer taken along section line AA.

[0015] Figure 4D The embodiment according to the present disclosure is shown Figure 4A Schematic diagram of the mixer tubes.

[0016] Figure 4E The embodiment according to the present disclosure is shown Figure 4D Schematic cross-sectional view of a tube.

[0017] Figure 4F FIG. 1 shows a cross-sectional view of an embodiment of the present disclosure having a tangential opening taken along section line BB. Figure 4D Schematic diagram of the tube.

[0018] Figure 4G shows a similar embodiment according to the present disclosure Figure 4D Schematic diagram of a tube having two tangential openings and cut along a section line equivalent to BB.

[0019] Figure 5 A schematic cross-sectional view of a mixer according to an embodiment of the present disclosure is shown.

[0020] Fig. 6A A schematic diagram of a mixer array according to an embodiment of the present disclosure is shown.

[0021] Figure 6B A schematic cross-sectional view of a mixer according to an embodiment of the present disclosure is shown.

[0022] Figure 6C A schematic cross-sectional view of a mixer according to an embodiment of the present disclosure is shown.

[0023] Fig. 7A A schematic diagram of a mixer array according to an embodiment of the present disclosure is shown.

[0024] Figure 7B A schematic cross-sectional view of a mixer according to an embodiment of the present disclosure is shown.

[0025] Figure 8 A schematic diagram of a mixer array according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0026] Various embodiments of the preferred embodiment are discussed in detail below. Although specific embodiments are discussed, this is for illustrative purposes only. Those skilled in the relevant art will recognize that other components and configurations may be used without departing from the spirit and scope of the present disclosure.

[0027] The mixer of the present disclosure is presented in the combustion section of a gas turbine engine. The mixer can mix or blend fuel and air before combustion. The mixer of the present disclosure may also be referred to as a premixer. The mixer can reduce carbon emissions by enhancing mixing to allow the combustion of pure hydrogen fuel (e.g., 100% hydrogen fuel) or a mixture of hydrogen fuel and natural gas (e.g., with a hydrogen percentage between 0% and 100%) with little or no low-speed areas and no flashback conditions. The mixer of the present disclosure provides a mixer that can mix fuel and air so as to achieve a uniform fuel-air distribution within the mixer and also eliminate areas of low-speed pockets within the mixer passage. This can allow the combustion of high H2 fuels while ensuring lower nitrogen oxide emissions.

[0028] The mixer of the present disclosure may include a round tube mixer. The mixer of the present disclosure may include a group of opposed jet channels, which may cause the axially injected fuel introduced between the group of opposed jet channels to increase lateral diffusion. The mixer of the present disclosure may include two tangential holes, which may cause the injected fuel to diffuse tangentially in the tube, thereby increasing the fuel-air mixing in the tube. Therefore, the mixer of the present disclosure may allow a cluster of microtubes in which fuel and air are mixed. Compared to the prior art, this may allow separation of the mixer and a more complex flow path, which may improve the fuel-air mixing in the tube, may reduce flame flashback into the microtube, and / or may reduce flame holding in the microtube.

[0029] refer to Figure 1 , a cross-sectional view of a conventional mixer 10 is shown. The mixer 10 may be included in a dry low emission (DLE) engine. The mixer 10 may include an outer vane 12 and an inner vane 14. The outer vane 12 may include one or more openings 16. Fuel may be injected or introduced through one or more openings 16. The inner vane 14 may include an opening 18. A swirling air flow may be injected or introduced through the opening 18. The swirling air flow from the inner vane 14 may be separated on the outer surface of the center body 20. As shown, the cross-section of the passage of the mixer 10 may be annular. The arrangement of the mixer 10 is not suitable for hydrogen (H2) fuel because the arrangement results in a recirculation area on the outer surface of the center body 20, which may increase the flame holding risk associated with the H2 fuel. The length of the mixer 10 may be such that the residence time of the fuel-air mixture in the mixer 10 may result in a high flame holding risk. The mixer 10 may result in a low speed zone close to the vanes. Arrangements such as the mixer 10 may allow a lower volume percentage of H2 fuel mixed in the fuel.

[0030] refer to Figure 2A and 2B, a cross-sectional view of a conventional mixer 50 is shown. The mixer 50 may be included in a DLE engine. The mixer 50 may include an annular mixer passage 52. The fuel may be injected from one or more openings 54 on a truncated cone 56. The mixer 50 may also include a central bluff body 58. The central bluff body 58 may form an annular mixing passage as shown. A separate air circuit may be provided for the air flow to be mixed with the fuel. Compared to the mixer 10, the mixer 50 may allow a higher volume percentage of H2 fuel to be mixed in the fuel. As in the mixer 10, there may be a low velocity zone within the mixer 50.

[0031] refer to Figure 3 , a schematic perspective view of a mixer array 100 is shown. The mixer array 100 may include one or more mixers 102. The mixer array 100 may be divided into one or more zones. For example, in FIG2 , the mixer array 100 may be divided into three zones: zone A, zone B, and zone C. The one or more mixers 102 provided in zone A, zone B, and zone C may all be of the same structure, or may all be of different structures, or may include some mixers of the same structure and some mixers of different structures.

[0032] Figures 4A-4E 2 shows a mixer 200 according to the present disclosure. The mixer 200 may be arranged at Figure 3 In the mixer array 100 (for example, the mixer 200 may replace Figure 3 One or more mixers 102 in the array 100). First, refer to Figure 4A , the mixer 200 may include one or more tubes 202 (e.g., miniature tubes) placed along the periphery of the mixer 200. That is, the one or more tubes 202 may be placed circumferentially around the central axis A of the mixer 200. The tubes 202 may represent generally cylindrical mixer channels arranged as small circular tubes. The placement may be evenly spaced or unevenly spaced around the periphery of the mixer 200. The mixer 200 may include a central body 204, also referred to as a central tube 204 having a central channel 206. A first annular channel 208 and a second annular channel 210 may be created between the central tube 204 and the one or more tubes 202. The central tube 204 may include one or more openings 212, the one or more openings 212 fluidly coupling the central channel 206 to the second annular channel 210. The one or more channels 214 may fluidly couple the first annular channel 208 to the one or more tubes 202, respectively. The one or more tubes 202 may include an internal channel 218 and opposing openings 222, 216. One or more openings 215 may fluidly couple the second annular passage 210 to the one or more tubes 202 . Figure 4B An end view of the outlet of the mixer 200 is shown. Figure 4BThe outlet 201 of each tube 202 can be seen. Figure 4C Shown along Figure 4A A view of the mixer 200 taken along section line AA. Figure 4C The fuel-air mixing passage 218, the central passage 206 and the second annular passage 210 can be seen in the view of FIG.

[0033] refer to Figure 4D-4G , showing one tube 202 of the mixer 200. As mentioned, multiple tubes 202 ( Figure 4A Each tube 202 may include a passage 214 having an opening 216, also referred to as an opposing opening 216, for connecting the first annular passage 208 ( Figure 4A ) is fluidly coupled to an internal passage 218, also referred to as a fuel-air mixing passage 218 of the tube 202. The internal passage 218 may be circular in cross-section (e.g., Figure 1 2). The inner passage 218 may be a fuel-air mixing passage. Each tube 202 may include a fuel passage 220 that may exit into the inner passage 218. Each tube 202 may include an opening 222, also referred to as an opposed opening 222, that leads to the inner passage 218. Each tube 202 may include an opening 224, also referred to as a tangential opening 224, that leads to the inner passage 218.

[0034] Return to reference Figure 4A , the fuel flow A can be introduced or injected axially into one or more fuel passages 220 from the front end of the mixer 200 in the direction of arrow A. The fuel flow A can flow from the fuel passage 220 into the internal passage 218 ( Figure 4D ). Air can be introduced into the mixer 200 at a variety of locations. For example, a central air stream B can be introduced into the central passage 206 in the direction of arrow B. The central air stream B can flow from the central passage 206 into the second annular passage 210 through one or more openings 212 and exit the interior passage 218 of the inlet tube 202 through opening 215. Air stream C can be introduced through the first annular passage 208 and exit the interior passage 218 of the inlet tube 202 through passage 214 in the direction of arrow C. Air stream D, also known as opposed air jet D and opposed air stream D, can be introduced into the interior passage 218 in the direction of arrow D through opposed openings 222. Air stream E, also known as tangential air jet E and tangential air stream E, can be introduced into the interior of the interior passage 218 in the direction of arrow E through tangential openings 224.

[0035] Figures 4A-4GThe mixer 200 can present an air flow that allows high-speed flow through the mixer 200. All of the streams A, B, C, D, and E can converge in the internal passage 218. The first set of opposing jets (e.g., streams C and D) can push the fuel stream A into the central region of the internal passage 218 (e.g., can increase the lateral diffusion of the fuel stream A) and can accelerate the velocity of the fuel stream A. The tangential air flow E can generate a tangential flow / velocity that generates a jet along the wall (e.g., such as Figure 4F and 4G ), and can cause the fuel flow A to diffuse tangentially in the internal passage 218, thereby increasing the fuel-air mixing within the tube 202. Figure 4E As shown, tangential opening 224 may be positioned behind opposing openings 216 and 222 to clean the wake created behind the jet.

[0036] like Figures 4A-4G The arrangement shown can prevent or inhibit flame holding. There can be a single tangential opening 224 ( Figure 4F ) or two tangential openings 224 ( Figure 4G ) to drive the fuel tangentially. More tangential openings (e.g., three or more) are contemplated. The tangential air flow can improve air-fuel mixing within the tube 202. The tangential holes can drive the fuel tangentially.

[0037] The tangential air flow E can be introduced at any angle relative to the opposed opening 222 (e.g., the angle of the tangential opening 224). The angle between the opposed openings 222 and 216 can be from about 20 degrees to about 170 degrees, or any value or range therebetween. The tangential holes can be positioned behind the opposed holes. In addition to facilitating the mixing of the fuel and air, this arrangement can allow for cleaning of the wake behind the jet from the opposed holes and can generate high speeds near the tube wall.

[0038] refer to Figure 5 , a mixer 300 is shown. The mixer 300 can be the same or similar to the mixer 200, with the following differences. In the mixer 300, the fuel stream A can be injected or introduced through the central passage 206, and then can be radially introduced into the internal passage 218. The opposing air streams C and D and the tangential air stream E can be presented in the same manner as Figure 4 and can be operated to increase mixing and accelerate flow, as described elsewhere herein. In addition, the fuel stream A introduced through the central passage 206 can enable the fuel to be discharged into different microtubes of a given mixer at different axial positions, which in turn can help to achieve different fuel-air distributions at the outlets of the microtubes of a given mixer. This arrangement can weaken combustion dynamics.

[0039] refer to Figures 6A-6C, a schematic diagram of an array of mixers 400 is shown. Although four mixers 400 are shown, more or less mixers can be provided. Mixer 400 can be the same or similar to other mixers described herein. In the array of mixers 400, one or more pilot tubes 401 and one or more main tubes 402 can be provided. Pilot tube 401 can introduce pilot fuel into the engine (e.g., fuel for starting the engine), and main tube 402 can introduce main fuel into the engine (e.g., fuel for operating the engine). Pilot fuel and main fuel can be different. Compared with the embodiment without one or more pilot tubes, pilot tube 401 can allow enhanced operability, lower carbon monoxide emissions and enhanced regulation (turn down) capabilities. Higher fuel-air ratio at the outlet of pilot tube 401 can be achieved by independently controlling the fuel flow through the pilot circuit, reducing the length of pilot tube 401, injecting fuel at the rear end of mixer 400 or any combination thereof. Each mixer can have a fuel injector in the center, which can be used as a pilot tube. Although two pilot tubes 401 are shown, more or fewer pilot tubes may be provided, including no pilot tubes 401. Pilot tubes 401 may be provided anywhere along the perimeter of the mixer 400. The location and number of pilot tubes 401 in a mixer 400 may be the same or different compared to other mixers 400 in the array.

[0040] refer to Figure 6B , the pilot tube 401a may be shorter relative to the main tube 402a. The reduced length of the pilot tube 401a compared to the main tube 402a may result in a different fuel distribution at the mixer outlet.

[0041] refer to Figure 6C , the axial position of fuel injection can be different for pilot tube 401b and main tube 402b. This can change the heat release radially and circumferentially in a way that affects the combustion dynamics. For example, the main fuel can be injected at A at a forward position relative to the pilot fuel, and the pilot fuel can be injected at B at a rearward position. Separate fuel supply lines can be provided to independently control the fuel injection in pilot tube 401a and main tube 402b. Main tube 402b can result in a more mixed fuel-air mixture than pilot tube 401b.

[0042] Figure 6B and 6C The pilot and main pipes can be combined and can be set separately Fig. 6A , or you can select only one and place it in Fig. 6A As previously described herein, the opposing air flows C and D and the tangential air flow E may also be present in Figure 6B and 6C Although Fig. 6A Two pilot tubes 401 are shown in FIG. 4 , but any number of pilot tubes may be provided at any location around the perimeter of the mixer 400. For the pilot tubes 401, the size of the openings and tube diameter may be smaller to control the pilot air flow to 2% to 20% of the total premixer flow. The size of each air and fuel opening for each tube may be different to vary the fuel-air ratio for different tubes, thereby varying the heat release and thereby improving the combustion dynamics.

[0043] refer to Fig. 7A and 7B , a schematic diagram of an array of mixers 500 is shown. Although four mixers 500 are shown, more or fewer mixers may be provided. The mixers 500 may be the same or similar to other mixers described herein. Each mixer 500, or one or more mixers 500, may include a fuel stream A (e.g., similar to Figure 5 ) to act as a pilot. Compared with a mixer not equipped with a pilot, an array of mixers 500 can allow for enhanced operability, lower carbon monoxide emissions, and enhanced regulation capabilities. Although mixers 500 are shown as having a pilot in the center, alternative positions such as, but not limited to, radial positions within a given mixer. For each mixer 500, the position of the pilot can be the same or different.

[0044] Figure 8 A schematic diagram of an array of mixers 600 is shown. The tubes 601 of the mixer 600 can be staggered relative to adjacent mixers. For example, tube 601a is not aligned or staggered relative to tubes 601b and 601c. A similar arrangement is shown for the remaining tubes 601. Alternatively, the tubes 601 can be directly in line (e.g., as Fig. 7A Staggered alignment can improve emissions.

[0045] Figure 1 The mixer 10 may include a central body 20 ( Figure 1 ) on the recirculation zone, a high percentage of hydrogen fuel may be trapped in the recirculation zone. This may cause flame holding. Therefore, due to the risk of flashback / flame holding, the mixer 10 may not be able to burn higher content H2 fuel.

[0046] As described above, the fuel may be injected axially near the center of the mixer. Downstream of the first set of jets, the opposed jets may improve the lateral diffusion of the fuel from the center of the mixer. Downstream of the tangential jets, the tangential jets may improve the tangential diffusion of the fuel from the center of the mixture. At the mixer outlet, there may be a uniform fuel distribution within the mixer, with a fuel-air mixture of about 97%.

[0047] The mixer of the present disclosure produces a shorter flame length in the burner (compared to other Figure 1 and the mixer depicted in Figure 2) and uniform temperature. Figure 1 The flame length is about 50% shorter than the flame length in the mixer of Figure 2. The increased mixing of fuel and air and the reduction or elimination of low velocity pockets may result in shorter flame length, more uniform temperatures in the burner, reduced flashback / flame holding risk, or any combination thereof.

[0048] The mixer of the present disclosure can be a micro mixer with a micro tube cluster (e.g., a tube cluster) having a central axis placed at a radial position greater than 0.8 times the outer diameter of the inner mixer relative to the center of the mixer. Each tube (e.g., a micro tube) can have a cylindrical restriction with a constant area cross section at the front end and a converging cross section at the rear end. This arrangement can maintain high speed in the tube. An array of such mixers can form different zones (e.g., as shown in Figure 2) in the burner.

[0049] The mixer of the present disclosure may allow fuel to be injected axially onto an inclined or angled surface, where the fuel may be blasted by air moving over the inclined or angled surface (e.g., from one or more tangential holes) and by opposing air (e.g., from opposing holes). The fuel may also be injected from a center body in a constant area cross section. The mixer of the present disclosure may include a mixer tip having a central region that may be cooled by air, fuel, or a combination thereof before the air, fuel, or a combination thereof is discharged into the mixer passage.

[0050] The mixer of the present disclosure may include multiple small tubes that may produce a small, compact flame, thereby increasing the residence time in the post-flame zone compared to prior art mixers, which may reduce carbon monoxide emissions.

[0051] The mixers of the present disclosure can be oriented so that the tubes on a particular mixer can be directly inline or staggered relative to the tubes of an adjacent mixer. Such an arrangement can improve drainage.

[0052] The mixers of the present disclosure have applications in aeroderivative engines, other gas turbine engines, and applications outside of gas turbine applications.The mixers of the present disclosure may reduce and / or eliminate carbon emissions by allowing the combustion of different mixtures of hydrogen fuels.

[0053] The hydrogen fuel percentage may vary from 0% to 100% by volume of the fuel mixture. The hydrogen fuel percentage may vary from 10% to 100% by volume of the fuel mixture. The hydrogen fuel percentage may vary from 20% to 100% by volume of the fuel mixture. The hydrogen fuel percentage may vary from 30% to 100% by volume of the fuel mixture. The hydrogen fuel percentage may vary from 40% to 100% by volume of the fuel mixture. The hydrogen fuel percentage may vary from 50% to 100% by volume of the fuel mixture. The hydrogen fuel percentage may vary from 60% to 100% by volume of the fuel mixture. The hydrogen fuel percentage may vary from 70% to 100% by volume of the fuel mixture. The hydrogen fuel percentage may vary from 80% to 100% by volume of the fuel mixture. The hydrogen fuel percentage may vary from 90% to 100% by volume of the fuel mixture. The hydrogen fuel percentage may vary from 55% to 95% by volume of the fuel mixture. The hydrogen fuel percentage may vary from 60% to 90% by volume of the fuel mixture. The hydrogen fuel percentage may vary from 65% to 85% by volume of the fuel mixture. The hydrogen fuel percentage may vary from 70% to 80% by volume of the fuel mixture. The hydrogen fuel percentage may vary from 85% to 100% by volume of the fuel mixture. The hydrogen fuel percentage may vary from 95% to 100% by volume of the fuel mixture. The hydrogen fuel percentage may vary from approximately 55%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100% by volume of the fuel mixture. The mixer of the present disclosure may allow 100% hydrogen fuel to be burned in the engine.

[0054] The mixer of the present disclosure may allow the combustion of natural gas, high hydrocarbon (C2+) fuels, hydrogen, or any combination thereof. The combustion of the above fuels or their combination may reduce NOx emissions compared to the mixers of the prior art. The ability to burn up to 100% hydrogen fuel may achieve a zero carbon footprint.

[0055] The fuel stream of the present disclosure can be represented as the fuel provided to the engine. The fuel stream can be a pure fuel stream (e.g., pure natural gas, pure hydrogen, etc.) or can be a mixed fuel stream (e.g., the volume percentage of two or more fuels, such as natural gas and hydrogen). The mixer of the present disclosure can be arranged in an engine, which can be started with a natural gas fuel without a hydrogen fuel mixed therein, and then the hydrogen fuel can be mixed into the natural gas fuel and rise to 70%-100% of the fuel mixture under lower power conditions to reduce carbon monoxide emissions. Then, the hydrogen fuel percentage can be reduced to about 50% of the fuel mixture under higher power conditions to achieve lower nitrogen oxide emissions. During the entire engine operation (e.g., under low power and high power conditions), the mixer can operate with 100% hydrogen fuel. A specific fuel mixture (e.g., including any percentage of hydrogen from 0% to 100%) can reduce NOx and CO emissions.

[0056] The mixer of the present disclosure may provide an air-fuel mixture / ratio that may eliminate the auto-ignition, flashback and flame holding risks typically associated with pure premixed burner / mixer designs with high hydrogen fuel mixtures.The mixer of the present disclosure may be presented in an arrangement that produces a compact and swirling flame.

[0057] The disclosed mixer may allow for aviation derived, 100% hydrogen fueled DLE engines. This could allow up to 100% hydrogen capability (zero carbon footprint) to be combined with renewable energy sources while requiring little or no water to meet lower NOx emissions requirements.

[0058] Further aspects of the disclosure are provided by the subject matter of the following clauses.

[0059] 1. A mixer for mixing fuel and air in a combustor of a gas turbine engine, the mixer comprising: a center body having a central passage and a central axis; a plurality of tubes positioned radially about the central axis and circumferentially about a periphery of the mixer, each of the tubes comprising: a first opening angled relative to the central axis and configured to introduce a first air flow; a second opening in opposed relation to the first opening, the second opening angled relative to the central axis and configured to introduce a second air flow; a tangential opening at a rearward position of the first opening and the second opening, the tangential opening angled relative to the central axis and configured to introduce a tangential air flow; and a cylindrical internal mixing passage configured to receive the first air flow, the second air flow, the tangential air flow, and a fuel flow, wherein the first air flow and the second air flow are configured to diffuse the fuel flow laterally, and the tangential air flow is configured to diffuse the fuel flow tangentially, and wherein a fuel-air mixture is present at an outlet of each of the plurality of tubes.

[0060] 2. A mixer according to any preceding clause, wherein the fuel flow is introduced axially from a front end of the mixer along each of the tubes into the cylindrical internal mixing passage.

[0061] 3. A mixer according to any preceding clause, wherein the fuel flow is introduced into the cylindrical internal mixing passage at a forward position relative to the first air flow, the second air flow and the tangential air flow.

[0062] 4. A mixer according to any preceding clause, further comprising a third air flow introduced through the central passage, through the annular passage between the central body and the plurality of tubes and into the cylindrical internal mixing passage.

[0063] 5. A mixer according to any preceding clause, wherein the tangential opening comprises two tangential openings.

[0064] 6. A mixer according to any preceding clause, wherein the fuel flow is introduced axially into the central passage of the central body from a front end of the mixer.

[0065] 7. A mixer according to any preceding clause, wherein the fuel flows from the central passage to an annular passage formed between the plurality of tubes and the center body and to the cylindrical internal mixing passage.

[0066] 8. A mixer according to any preceding clause, wherein the fuel flow is introduced into the cylindrical internal mixing passage at a rearward position of the first air flow, the second air flow and the tangential air flow.

[0067] 9. A mixer according to any preceding clause, wherein at least one tube of the plurality of tubes is a pilot tube and the remaining tubes of the plurality of tubes are main tubes.

[0068] 10. A mixer according to any preceding clause, wherein the pilot tube comprises a pilot cylindrical internal mixing passage having an axial length which is shorter than an axial length of a main cylindrical internal mixing passage of the main tube.

[0069] 11. A mixer according to any preceding clause, wherein the fuel flow is introduced into the pilot conduit at a forward position in the mixer relative to the fuel flow introduced into the main conduit.

[0070] 12. A mixer according to any preceding clause, wherein there is no low velocity region within each of said cylindrical internal mixing passages of said plurality of tubes.

[0071] 13. A mixer array for a turbine engine, the mixer array comprising: a plurality of mixers, each mixer having a central body and a plurality of microtubes positioned circumferentially around the central body, wherein each of the plurality of microtubes comprises a cylindrical mixing channel, an opposed air flow generated by air flows through opposed openings in the cylindrical mixing channel, and a tangential air flow generated by air flows through tangential openings in the cylindrical mixing channel, wherein each of the plurality of microtubes is configured to mix a fuel flow with the opposed air flow and the tangential air flow, and wherein the opposed air flow is configured to diffuse the fuel flow laterally, and the tangential air flow is configured to diffuse the fuel flow tangentially.

[0072] 14. A mixer array according to any preceding clause, characterized in that, in each of the plurality of mixers, the fuel flow is axially introduced from a front end of the mixer into the cylindrical mixing channel of each of the microtubes.

[0073] 15. A mixer array according to any preceding clause, wherein in each of the plurality of mixers, the fuel flow is introduced into the cylindrical mixing passage at a forward position relative to the opposing air flow and the tangential air flow.

[0074] 16. A mixer array according to any preceding clause, wherein in each mixer of the plurality of mixers, the fuel flow is introduced axially into the central body from a front end of the mixer.

[0075] 17. A mixer array according to any preceding clause, characterized in that in each of the plurality of mixers, at least one of the plurality of microtubes is a pilot tube and the remaining microtubes of the plurality of microtubes are main tubes.

[0076] 18. The mixer array of any preceding clause, wherein the microtubes of a first mixer of the plurality of mixers are directly aligned with the microtubes of a second mixer of the plurality of mixers.

[0077] 19. The mixer array of any preceding clause, wherein the microtubes of a first mixer of the plurality of mixers are staggered and misaligned with the microtubes of a second mixer of the plurality of mixers.

[0078] 20. A method for mixing fuel in a gas turbine engine, characterized in that the method includes: injecting natural gas fuel into the gas turbine engine to start the operation of the gas turbine engine; after the start-up operation, injecting a certain volume percentage of hydrogen fuel into a mixer together with the natural gas to provide a fuel mixture to the gas turbine engine; and increasing the volume percentage of hydrogen fuel to a range of 70% to 100% of the fuel mixture, wherein the mixer provides opposing air flows and tangential air flows to mix the fuel mixture flow and reduce low-speed pockets in the mixer, thereby reducing emissions.

[0079] 21. A method according to any preceding clause, wherein the opposed air flows are provided from a pair of opposed openings and the tangential air flow is provided from a tangential opening, the pair of opposed openings and the tangential opening each being angled relative to a central axis of the mixer.

[0080] 22. A method according to any preceding clause, wherein the opposing air flows and the tangential air flows are provided in clusters of micro-tubes provided around the periphery of the mixer.

[0081] 23. A method according to any preceding clause, wherein the tangential air flow is introduced behind the opposing air flow.

[0082] 24. A method according to any preceding clause, wherein the opposed air flows are configured to diffuse a fuel mixture flow laterally and the tangential air flows are configured to diffuse the fuel mixture flow tangentially.

[0083] Although the foregoing description is directed to preferred embodiments, it should be noted that other variations and modifications will be apparent to those skilled in the art and may be made without departing from the spirit or scope of the present disclosure. In addition, features described in conjunction with one embodiment may be used in conjunction with other embodiments, even if not explicitly stated above.

Claims

1. A mixer for mixing fuel and air in a combustor of a gas turbine engine, characterized in that The mixer comprises: a central body having a central passage and a central axis; a plurality of tubes positioned radially about the central axis and circumferentially about the periphery of the mixer, each of the tubes comprising: a first opening angled relative to the central axis and configured to introduce a first air flow; a second opening in opposed relation to the first opening, the second opening being angled relative to the central axis and configured to introduce a second air flow; a tangential opening at a rearward position of the first opening and the second opening, the tangential opening being angled relative to the central axis and configured to introduce a tangential air flow; and a cylindrical internal mixing passage configured to receive the first air flow, the second air flow, the tangential air flow, and a fuel flow, wherein the first air flow and the second air flow are configured to diffuse the fuel flow laterally, and the tangential air flow is configured to diffuse the fuel flow tangentially, and Wherein a fuel-air mixture is present at an outlet of each of the plurality of tubes.

2. The mixer according to claim 1, characterized in that The fuel flow is introduced axially from the front end of the mixer along each of the tubes into the cylindrical internal mixing passage.

3. The mixer according to claim 2, characterized in that wherein the fuel flow is introduced into the cylindrical internal mixing passage at a forward position relative to the first air flow, the second air flow, and the tangential air flow.

4. The mixer according to claim 1, characterized in that Further included is a third air flow introduced through the central passage, through an annular passage between the center body and the plurality of tubes and into the cylindrical inner mixing passage.

5. The mixer according to claim 1, characterized in that The tangential opening comprises two tangential openings.

6. The mixer according to claim 1, characterized in that The fuel flow is introduced axially into the central passage of the central body from the front end of the mixer.

7. The mixer according to claim 6, characterized in that The fuel flows from the central passage to an annular passage formed between the plurality of tubes and the center body, and flows to the cylindrical inner mixing passage.

8. The mixer according to claim 7, characterized in that The fuel flow is introduced into the cylindrical internal mixing passage at a rear position of the first air flow, the second air flow, and the tangential air flow.

9. The mixer according to claim 1, characterized in that At least one tube of the plurality of tubes is a pilot tube, and the remaining tubes of the plurality of tubes are main tubes.

10. The mixer according to claim 9, characterized in that The pilot tube comprises a pilot cylindrical internal mixing passage, the axial length of the pilot cylindrical internal mixing passage is shorter than the axial length of the main cylindrical internal mixing passage of the main tube.

11. The mixer according to claim 9, characterized in that The fuel flow is introduced into the pilot conduit at a front position in the mixer relative to the fuel flow introduced into the main conduit.

12. The mixer according to claim 1, characterized in that wherein no low velocity region exists within each of said cylindrical internal mixing passages of said plurality of tubes.

13. A mixer array for a turbine engine, characterized in that: The mixer array comprises: a plurality of mixers, each mixer having a central body and a plurality of microtubes positioned circumferentially around the central body, wherein each of the plurality of microtubes comprises a cylindrical mixing channel, an opposing air flow generated by air flow through opposing openings in the cylindrical mixing channel, and a tangential air flow generated by air flow through tangential openings in the cylindrical mixing channel, wherein each of the plurality of microtubes is configured to mix the fuel flow with the counter air flow and the tangential air flow, and Wherein, the opposing air flow is configured to diffuse the fuel flow laterally, and the tangential air flow is configured to diffuse the fuel flow tangentially.

14. The mixer array according to claim 13, characterized in that wherein in each of the plurality of mixers, the fuel flow is axially introduced from a front end of the mixer into the cylindrical mixing passage of each of the microtubes.

15. The mixer array according to claim 14, characterized in that wherein in each of the plurality of mixers, the fuel flow is introduced into the cylindrical mixing passage at a forward position relative to the opposed air flow and the tangential air flow.

16. The mixer array according to claim 13, characterized in that Wherein in each of the plurality of mixers, the fuel flow is introduced axially into the central body from a front end of the mixer.

17. The mixer array according to claim 13, characterized in that Wherein in each of the plurality of mixers, at least one of the plurality of microtubes is a pilot tube, and the remaining microtubes of the plurality of microtubes are main tubes.

18. The mixer array according to claim 13, characterized in that The microtubes of a first mixer among the plurality of mixers are directly aligned with the microtubes of a second mixer among the plurality of mixers.

19. The mixer array according to claim 13, characterized in that The microtubes of a first mixer among the plurality of mixers are staggered and not aligned with the microtubes of a second mixer among the plurality of mixers.

20. A method for mixing fuel in a gas turbine engine, characterized in that The method comprises: injecting natural gas fuel into the gas turbine engine to initiate operation of the gas turbine engine; After a start-up operation, injecting a certain volume percentage of hydrogen fuel into the mixer along with the natural gas to provide a fuel mixture to the gas turbine engine; and increasing the volume percentage of hydrogen fuel to a range of 70% to 100% of the fuel mixture, The mixer provides opposing air flows and tangential air flows to mix the fuel mixture flow and reduce low velocity pockets in the mixer, thereby reducing emissions, wherein the mixer is the mixer of any one of claims 1-12.

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