Supply device, burner system, and method

Abstract

The invention relates to a supply device (1), in particular for use in a gas turbine, for supplying oxidizer (38) and fuel (38) into a combustion chamber (3), comprising a supply nozzle (10) having an in particular cylindrical nozzle channel (14), which is delimited by a nozzle wall (16) and is oriented along a longitudinal axis (L) and opens into a combustion-chamber-side outlet opening (12) adjacent to the combustion chamber (3), and an in particular cylindrical injector element (17) for introducing fuel, within which an inner channel (34) for conducting an inner flow (36) of oxidizer (38) is formed, wherein an atomising edge (20) is formed at a downstream end (21) of the injector element (17), wherein an outer channel (30) for the swirl-free conducting of an outer flow (32) of oxidizer (38) is formed between the nozzle wall (16) and the radial outer side of the injector element (17). In this way, an advantageous use of liquid fuels with a simplified structure is provided, in that the injector element (17) has an outer wall (24) and an inner wall (26), which are arranged coaxially with respect to one another and between which an annular channel (28) is formed for guiding fuel to a fuel supply opening (25) for introducing the fuel (40) into the inner channel (34), said inner channel being delimited by an inner surface (23) of the outer wall (24) and by an outer surface (29) of the inner wall (26).

Description

[0001] JECK, FLECK & PARTNER mbB P.O. Box 14 69 • D-71657 Vaihingen / Enz

[0002] PAT EN TA N WÄ LT E Telephone (07042) 9728 - 0

[0003] Fax (07042) 9728 - 11

[0004] A 25823-PCT - JF / bau 11 December 2025

[0005] German Aerospace Center (DLR) - University of Stuttgart e. V. Keplerstr. 7

[0006] Königswinterer Str. 522 - 524 70174 Stuttgart 53227 Bonn

[0007] - 1 -

[0008] Feeding device, burner system and process

[0009] The invention relates to a supply device, in particular for use in a gas turbine, for supplying oxidizer and fuel into a combustion chamber, comprising

[0010] - a feed nozzle with a nozzle channel, in particular cylindrical, enclosed by a nozzle wall and aligned along a longitudinal axis, which opens into a combustion chamber-side outlet opening adjacent to the combustion chamber, and

[0011] - a particularly cylindrical injector element for fuel injection, within which an inner channel is formed for directing an internal flow to the oxidizer, wherein an atomizing edge is formed at a downstream end of the film laying device, and wherein an outer channel is formed between the nozzle wall and the radial outer surface of the injector element for directing an external flow to the oxidizer without swirl. The invention further relates to a burner system with a feed device and a method for supplying oxidizer and fuel into a combustion chamber.

[0012] Burner systems with at least one such feed device are also known as recirculation-stabilized jet flame burners for non-swirling high-speed combustion. The combustion zone in the combustion chamber is described in A 25823-PCT - JF / bau - 2 - 11 December 2025.

[0013] Operation is stabilized by a large-scale, combustion chamber-internal recirculation of exhaust gas, which forms due to the introduction of oxidizer fuel jets with a sufficiently high axial impulse into the combustion chamber. The recirculation brings the combusted, hot exhaust gas back to the jet root near the feed nozzles and mixes it with the incoming fresh gases. In a known annular arrangement of the feed nozzles, the recirculation zone typically forms essentially radially within the nozzle ring, with a backflow running along the combustion chamber's central axis.

[0014] When using liquid fuels, such burner systems can experience fuel interaction with the nozzle inner wall, resulting in enriched fuel reaching the combustion chamber as a ligate or in the form of poorly atomized, large droplets. This has a direct negative impact on the stability, operating range, and emissions of the burner system.

[0015] A feed device of the type mentioned above, for the advantageous operation of a recirculation-stabilized jet flame burner with liquid fuels, is described in DE 10 2022 105 076 A1. In this device, the fuel is added to the oxidizer flow within the nozzle channel by means of a pressure-drill injector with a complex design.

[0016] Another burner system with a recirculation-stabilized jet flame burner, for operation with gaseous fuels, is described, for example, in EP 1 918 641 A2.

[0017] The invention is based on the objective of providing a feeding device of the type mentioned above with a simplified design, as well as a corresponding burner system and feeding method. A 25823-PCT - JF / bau - 3 - 11 December 2025

[0018] The problem is solved for the feed device with the features of claim 1, for the burner system with the features of claim 18 and for the method with the features of claim 19.

[0019] According to the invention, the supply device is provided in that the injector element has an outer wall and an inner wall which are arranged coaxially to each other (with respect to the longitudinal axis) and between which (in particular exclusively) an annular channel for supplying fuel to a fuel supply opening for introducing the fuel into the inner channel is formed, which is bounded by an inner surface of the outer wall and by an outer surface of the inner wall.

[0020] The injector element is designed in particular with open axial ends for flow through with oxidizer.

[0021] The outer wall and / or the inner wall are, in particular, at least substantially cylindrical and / or slightly conical (e.g., with an angle of at most ± 3°, at most ± 5°, or at most ± 10°). The outer channel, the inner channel, and / or the annular channel can, along its axial course, especially upstream of the downstream section, exhibit a flow cross-section that is substantially (e.g., apart from inlet and / or outlet geometries) constantly shaped and / or continuously changing.

[0022] The design is such that the inner channel in the area of ​​the injector element is directly surrounded (without the intermediate arrangement of another channel) by the annular channel and the annular channel is directly surrounded (without the intermediate arrangement of another channel) by the outer channel.

[0023] The fuel can be, for example, a mixture of liquid hydrocarbons, e.g., kerosene and / or (heating) oil, and / or a liquid hydrocarbon in its pure form. Also particularly suitable are A 25823-PCT - JF / bau - 4 - 11. December 2025

[0024] Alcohols and / or fuels from biogenic sources, for example OME (oxymethylene ether). Alternatively or additionally, the fuel can be a high-, medium- and / or low-calorific fuel gas, for example natural gas, hydrogen and / or synthesis gas.

[0025] The injector element enables advantageous fuel atomization by utilizing the high axial momentum of the oxidizer flow within the feed nozzle, inherent in the combustion concept of this type, using a comparatively simple design. Furthermore, the same configuration can be advantageously operated with both liquid and gaseous fuels, thus achieving high fuel flexibility.

[0026] It is particularly preferred that the narrowest flow cross-section of the annular channel is arranged at and / or immediately upstream of the fuel supply opening, wherein the radial height of the annular channel at the fuel supply opening is a maximum of 200 pm, preferably a maximum of 100 pm, e.g., between 35 pm and 80 pm. For this purpose, the radial height of the annular channel preferably decreases continuously within a downstream section. Upstream of the downstream section, the gap height of the annular channel is preferably constant. The reduction or the narrowest flow cross-section is such that, by means of a liquid fuel, e.g., within a design operating point, a certain minimum pressure drop (preferably of more than 200 mbar) occurs on the fuel side at the narrowest flow cross-section.This formation results in a homogenization of the liquid fuel across the circumference of the annular channel before it enters the oxidizer at the fuel supply opening.

[0027] In particular, the injector element is designed as a film-laying device, wherein a film-laying surface is provided between the fuel supply opening and the atomizing edge, at the downstream end of which the atomizing edge is arranged. In particular, the annular channel with the fuel supply opening opens onto the film-laying surface. The axial length of the film-laying surface can be, for example, up to twice, e.g., between two and one-fifth, the diameter of the injector element at its downstream end. The combination of film-laying device and injector element makes it possible to utilize the high axial flow impulse of the oxidizer flow in the supply nozzle, available in a burner system of this type, for atomization by means of the film-laying device (in particular at the atomizing edge).At the same time, unwanted liquid interaction on the inner wall of the feed nozzle, which would be detrimental to the burner system, is avoided. The feed device is particularly suitable for very short installation lengths and feed nozzles and is also suitable for direct injection into the combustion chamber (atomizer edge at the outlet opening).

[0028] In a favorable design variant, the inner wall terminates upstream of the outer wall, with the film-laying surface being formed on the inner surface of the outer wall. In this way, the film-laying surface is positioned so that the internal flow can pass over it, and this flow is designed to propel the forming fuel film of liquid fuel to the atomizer edge.

[0029] To obtain a thin fuel film, the film-laying surface is advantageously cylindrical and / or extending axially-radially outwards in the flow direction (with respect to the longitudinal axis), preferably at an angle to the longitudinal axis of a maximum of 10°, more preferably a maximum of 7°, and particularly preferably a maximum of 5° or a maximum of 3°. This results in a cylindrical or slightly outwardly opening conical shape of the inner channel in the axial region of the film-laying surface. Even with the slightly outwardly opening shape, the axial directional component is significantly larger than the radial directional component.In this way, when the inner and outer flows come into contact, an advantageous interaction between the outer flow, which also flows at least substantially axially, and the inner flow can be achieved at the oxidizer downstream of the film-laying surface, forming an initially at least substantially axially oriented shear layer. A 25823-PCT - JF / bau - 6 - 11 December 2025.

[0030] In addition, the formation of local recirculation zones at the atomizer edge is minimized.

[0031] Further improvement in atomization can be achieved if at least one microstructure, for example two or three microstructures, is arranged on the film laying surface, wherein the microstructure (or its individual elements, if applicable) is convex or concave relative to the film laying surface, i.e., forms a radial elevation or depression relative to the rest of the film laying surface. The microstructure has a radial height of at most the radial height of the fuel feed opening, e.g., at most half the radial height of the fuel feed opening, and / or at least one-fifth or one-quarter of the radial height of the fuel feed opening. The microstructure causes, for example, a build-up of the fuel film accompanied by a more uniform distribution, thereby enabling the targeted compensation of unevenness on the film laying surface, e.g., due to the (additive) manufacturing process.

[0032] In an advantageous embodiment, the at least one microstructure is formed at a constant axial position and / or rotates completely around the longitudinal axis, in the form of a ring rotating around the longitudinal axis. The axial extent of the ring is preferably as small as possible, for example, a maximum of twice, preferably a maximum of once, the radial height of the microstructure. Advantageous effects result, for example, with three such microstructures arranged axially one behind the other at equidistant distances, whereby the axial distances between them can also be different.

[0033] Preferably, the inner wall and / or the outer wall tapers (with respect to their wall thickness) towards their downstream ends within a downstream section of the injector element, particularly with an angle (of the wall profile) of a maximum of 7°, preferably a maximum of 5°, and most preferably a maximum of 3° with respect to the longitudinal axis, in order to prevent flow separation. The taper is preferably to the smallest possible wall thickness at the downstream ends, such that mechanical stability is ensured. For example, this can be the case with a wall thickness of a maximum of 0.5 mm, e.g., between 50 pm and 150 pm. The taper is particularly continuous within the downstream section to prevent flow separation.The length of the downstream section, particularly starting at the upstream end of the taper in the inner and / or outer wall (depending on where the taper begins further upstream), is, for example, a maximum of 3 times the inner diameter, e.g., a maximum of 2 times, 1.5 times, or once the outer diameter of the downstream end of the injector element. This advantageously avoids dead-stream areas with unfavorable fuel accumulation at the downstream ends. Furthermore, it achieves the sharpest possible edge for the atomizer located at the downstream end of the outer wall.

[0034] Preferably, the inner surface (of the outer wall) and / or the outer surface (of the inner wall), e.g., over a certain length directly upstream of the fuel supply opening, or over the entire axial length of the annular channel up to the fuel supply opening and optionally including the film laying surface, up to the atomizer edge, is cylindrical and / or conical (radially inwards or outwards), with a directional component of a maximum of 10°, preferably a maximum of 7°, particularly preferably a maximum of 5° or a maximum of 3°, with respect to the longitudinal axis. The orientation is particularly similar to or corresponding to the orientation of the film laying surface, e.g., with a deviation of a maximum of 10°, preferably a maximum of 7°, particularly preferably a maximum of 5° or a maximum of 3°.In this way, the fuel is given at least a substantially axial directional component as it flows out of the fuel feed opening, which, for the sake of uniform flow guidance, preferably corresponds at least substantially to the flow direction on the film laying surface. A 25823-PCT - JF / bau - 8 - 11 December 2025.

[0035] Alternatively or additionally, the other surface can be oriented to narrow the flow cross-section within a downstream section, i.e., the outer surface (of the inner wall) extends axially-radially outwards in the flow direction, towards the inner surface, and / or the inner surface (of the outer wall) extends axially-radially inwards in the flow direction, towards the outer surface. The angle with respect to the respective opposite wall is, for example, a maximum of 10°, preferably a maximum of 7°, and particularly preferably a maximum of 5° or a maximum of 3°. Thus, the wall surfaces converge to narrow the flow cross-section. The narrowing, with a reduction in the radial height of the annular channel and / or the flow cross-section, is preferably continuous within the downstream section and of the same length or axially shorter than the length of the downstream section.For example, the axial length of the constriction can correspond at most to the radius or half the radius of the inner channel at its downstream end.

[0036] Particularly in this context, it can be advantageous to provide that the flow cross-section of the inner channel increases towards the downstream end of the injector element. For example, the diameter of the inner channel can increase by more than 20%, preferably by more than 30% (relative to the smaller diameter upstream). This further reduces the flow velocity of the inner stream before it meets the outer stream, thus strengthening the shear layer between the two air streams. Furthermore, a directional component of the inner stream is generated slightly radially outwards (less than the axial component), which is advantageous for the interaction with the liquid film on the film-laying surface and / or for the radial dispersion of the droplets.

[0037] An advantageous air split between the inner and outer oxidizer flows is possible if an upstream end of the injector element is located downstream of an inlet opening in the nozzle channel. During operation, a total oxidizer flow enters the nozzle channel and is split at the upstream end of the injector element into (exclusively) the outer and inner flows.

[0038] Favorable adaptation options for different operating scenarios arise when the downstream end of the injector element is arranged axially upstream or at the level of the outlet opening.

[0039] For symmetrical combustion and the associated advantages, the nozzle channel is preferably cylindrical and / or has a constant (inner) diameter (over its entire length).

[0040] For advantageous fuel atomization, the inner and outer channels are designed such that at the downstream end of the injector element, the flow velocity through the outer channel is greater than the flow velocity through the inner channel, e.g., by at least 25%, preferably by a factor of at least 2, e.g., by a factor of 3 to 5. The outer and inner flows preferably flow in parallel. The outer flow serves for atomization at the downstream end of the film laying device and protects the nozzle wall from fuel wetting. Atomization into fuel droplets at the atomization edge is achieved in particular by high shear velocities of the outer flow. The inner flow interacts with the fuel film on the film laying surface. Downstream of the atomization edge, the fuel droplets follow the oxidizer flow. The design is carried out in particular by means of rough calculations and / or computer-aided flow simulation.This involves, for example, designing the flow cross-sectional areas of the inner channel and / or the outer channel accordingly and / or generating pressure losses within the inner channel and / or the outer channel in other ways, such as surface modulation, the installation of flow obstructions, and / or the appropriate design of the upstream end of the injector element. A 25823-PCT - JF / bau - 10 - 11 December 2025.

[0041] Advantageous effects on atomization can result from the arrangement of a swirl device within the inner channel to impart a slight circumferential swirl to the internal flow, with a swirl number (ratio of tangential velocity component to axial velocity component) of less than 1, preferably less than 0.5, and particularly less than 0.3, e.g., 0.2 or less. The swirl number is determined, in particular, at the axial end of the primary breakup, i.e., at the position where the continuous, liquid fuel flow splits. With the present geometry, this position is located, in particular, at an axial distance from the atomizer edge of between 0.5 and 1 times the diameter of the inner channel at the level of the atomizer edge, and / or between 6 mm and 12 mm downstream of the atomizer edge.The swirl number is such that combustion stabilization within the combustion chamber continues to occur due to the high axial impulse via the large-scale recirculation zone. This results in no small-scale flame-stabilizing backflow regions within the combustion chamber, specifically within the radial area of ​​the feed nozzle (relative to the central longitudinal axis of the combustion chamber).

[0042] Preferably, one fuel channel, or preferably three fuel channels, is provided for introducing fuel into the annular channel. These fuel channels run through the outer channel and open into the annular channel. The walls of the fuel channels can simultaneously serve as support elements and / or for securing the injector element within the nozzle channel.

[0043] Cost-effective manufacturing options for a precise and small-scale design arise when at least the injector element, for example the entire feed nozzle and / or feed device, is additively manufactured.

[0044] Preferably, the feed nozzle for adding oxidizer and liquid and / or gaseous fuel to the combustion chamber is designed with a high axial impulse, wherein the mean flow velocity at the outlet opening is between 40 m / s and 160 m / s, particularly between 80 m / s and 140 m / s. A 25823-PCT - JF / bau - 11 - 11 December 2025

[0045] The main flow direction is primarily axial, at least for the most part, or exclusively. This induces a large-scale, internal recirculation flow within the combustion chamber during operation, stabilizing the combustion process. The design refers, for example, to one or more design points.

[0046] A compact burner system design is achievable if the feed device is designed for operation at a thermal output of at least 1 kW, for example, between 5 kW and 30 kW (with respect to atmospheric pressure and / or air-fuel ratios between, for example, 0.3 and 5) per feed nozzle. The thermal output can be advantageously scaled up by increasing the size of the unit and / or the operating pressure. The injector element is suitable for operation with a large dynamic range (i.e., maximum to minimum fuel mass flow rate) of more than a factor of 20, whereby, for example, advantageous operation with extremely low fuel mass flows is also possible (e.g., from 0.03 g / s to 2 g / s). The diameter of the nozzle channel can be, for example, a minimum of 4 mm. The outer diameter of the injector element can be, for example, between 20% and 80% of the diameter of the nozzle channel.

[0047] The design features described above (individually or in combination) result in highly advantageous applicability, even with a compact feed system, offering a comparatively short flame length and very good axial symmetry of the flame, thus enabling the use of a relatively short combustion chamber. For required high power outputs, several feed systems are preferably used in a burner system, for example, in a matrix and / or ring arrangement. This allows the feed system to be used advantageously even in applications with high power requirements where the compact design of a burner system is paramount, for example, in aviation. A 25823-PCT - JF / bau - 12 - 11 December 2025

[0048] Advantageous process variants are indicated analogously in connection with the above-described design variants of the feed device and / or the burner system.

[0049] The invention will now be explained in more detail using exemplary embodiments and with reference to the drawings. The drawings show:

[0050] Fig. 1 shows a burner system according to the invention with several feed devices and a combustion chamber in a simplified schematic representation,

[0051] Fig. 2 A, B, C shows a supply device according to the invention for adding liquid fuel to the combustion chamber in a longitudinal section (Fig. 2A), in a cross-section AA (Fig. 2B) and in a cross-section BB (Fig. 2C) and

[0052] Fig. 3 shows a further embodiment of a supply device according to the invention for adding liquid fuel to the combustion chamber in a longitudinal section.

[0053] Fig. 1 shows an exemplary installation situation of (not shown in detail) feed devices 1 according to the invention in a burner system 4, which is particularly suitable for use in gas turbines in aviation or in power generation applications. The burner system 4 has a combustion chamber 3 and an end plate 6 arranged on the upstream side of the combustion chamber 3, through which the feed devices 1 open into the combustion chamber 3. In particular, a plurality of feed devices 1 can be present, which are arranged, for example, in a matrix-like and / or ring-like configuration on the end plate 6. A 25823-PCT - JF / bau - 13 - 11 December 2025

[0054] The feed devices 1 serve to introduce liquid and / or gaseous fuel 40 and oxidizer 38 from a distributor side 2 (not shown in detail here) into the combustion chamber 3 via the end plate 6. The combustion chamber 3 extends axially along a central longitudinal axis M of the burner system 4 and, for example, radially rotationally symmetric about the same. The end plate 6 is oriented, in particular (e.g., exclusively), orthogonally to the central longitudinal axis M. The feed devices 1 extend along longitudinal axes L that are aligned parallel to the central longitudinal axis M of the burner system 4.

[0055] Fuel 40 can be, for example, a mixture of liquid hydrocarbons, such as kerosene, (heating) oil, and / or an alcohol (mixture), and / or a liquid hydrocarbon present as a pure substance. Alternatively or additionally, the feed devices 1 can advantageously be operated with gaseous fuels of different calorific values, such as natural gas, synthesis gas, and / or hydrogen, or fuels containing these components. The burner system 4 is designed, for example, for operation with air-fuel ratios between 0.3 and 5.

[0056] The burner system 4 is designed as a recirculation-stabilized jet flame burner for non-swirl-free, high-velocity combustion. In this type of burner system, unburned fuel 40 and oxidizer 38 are introduced into the combustion chamber 3 with such a high axial impulse that a large-scale recirculation zone 5 forms within the combustion chamber 3 to stabilize the combustion zone. "At least essentially swirl-free" means that, despite any slight circumferential swirl that may be present, combustion is stabilized by means of the large-scale recirculation zone, not by local radial recirculation in the region of the nozzle cross-section. The average flow velocity at each outlet opening 12 is, for example, between a minimum of 40 m / s, preferably a minimum of 80 m / s, and a maximum of 160 m / s or higher. A 25823-PCT - JF / bau - 14 - 11 .December 2025.

[0057] Figures 2A, 2B, and 2C show the internal structure of the feed device 1 in sectional views (Figure 2A: longitudinal section, Figure 2B: cross-section AA, Figure 2C: cross-section BB). As shown in Figure 2A, the feed device 1 has a feed nozzle 10 with a nozzle channel 14, enclosed by a nozzle wall 16 and oriented along the longitudinal axis L. The nozzle channel 14 is cylindrical on the inside (over its entire length) and has an exemplary constant cross-section or diameter. The nozzle channel 14 opens into the combustion chamber-side outlet opening 12, which is circular and, in the assembled state, adjoins the combustion chamber 3.

[0058] For the addition of the fuel 40 into the nozzle channel 14, the supply device 1 comprises an injector element 17, which is manufactured in particular additively, by means of a 3D printing process.

[0059] The injector element 17 is in particular arranged completely within the nozzle channel 14 and / or coaxially to the supply nozzle 10 on the longitudinal axis L, i.e. an upstream end 22 of the injector element 17 is arranged downstream of an inlet opening 15 of the oxidizer 38 in the nozzle channel 14.

[0060] An external channel 30 is formed between the nozzle wall 16 and the radial outer surface of the injector element 17 for directing an external flow 32 to oxidizer 38.

[0061] The injector element 17 has an internal channel 34 for directing an internal current 36 to oxidizer 38.

[0062] At a downstream end 21 of the injector element 17, the internal flow 36 opens, for example, into the external flow 32 within the nozzle channel 14. It is also possible that the internal flow 36 opens directly into the combustion chamber 3. In this case, a downstream end 22 of the injector element 17 is arranged axially upstream or at the level of the outlet opening 12. A 25823-PCT - JF / bau - 15 - 11 December 2025

[0063] The injector element 17 has an outer wall 24, which is at least partially and / or substantially cylindrical, and an inner wall 26, which is at least partially and / or substantially cylindrical, arranged coaxially to each other along the longitudinal axis L. A ring channel 28 is formed, in particular completely circumferentially, between the outer wall 24 and the inner wall 26, opening into the inner channel 34 at a fuel supply opening 25 for introducing the fuel 40. The ring channel 28 is bounded radially on the outside by an inner surface 23 of the outer wall 24 and radially on the inside by an outer surface 29 of the inner wall 26.

[0064] To introduce the fuel 40 into the annular channel 28, at least one fuel channel (e.g., three fuel channels evenly distributed in the direction of rotation) is provided, which runs through the outer channel 30 and opens into the annular channel 28 (not shown in Fig. 2A). The fuel channel(s) can, in particular, also serve as a fastening element(s) for securing the injector element 17 within the nozzle channel 14.

[0065] The injector element 17 is designed as a film laying device 18, with the fuel supply opening 25 opening onto a downstream film laying surface 19. At the downstream end of the film laying surface 19, which simultaneously forms the downstream end 21 of the injector element 17, an atomizing edge 20 for atomizing liquid fuel is arranged. The film laying surface 19 is formed, in particular, on the inner surface 23 of the outer wall 24, with the inner wall 26 terminating upstream of the outer wall 24. In this way, the film laying surface 19 is advantageously oriented towards the inner channel 34, whereby the inner flow 36 can, during operation, propel the fuel film formed on the film laying surface 19 up to the atomizing edge 20.

[0066] The annular channel 28 is designed such that a narrowest flow cross-section is located at and / or immediately upstream of the fuel supply opening 25. Preferably, the fuel supply opening 25 has an extremely low radial height, e.g., a maximum of 200 pm, preferably a maximum of 100 pm. Preferably, the design is such that a certain minimum pressure drop, in particular more than 100 mbar, occurs across the annular channel 28 during operation with a liquid fuel (for example, at least within a design operating point), wherein the pressure drop decreases substantially at or near the fuel supply opening 25 with the liquid fuel.The resulting uniform film formation on the film laying surface 19 in the circumferential direction, as well as the extremely thin fuel film due to the low radial height of the fuel supply opening 25, contribute to advantageous fuel atomization.

[0067] The outer wall 24 is formed, in particular, as a completely cylindrical surface 23 with a constant inner diameter over its entire length. The film-laying surface 19 is also cylindrical in order to maintain the advantageously extremely thin fuel film during operation up to the atomizer edge 20. Alternatively, the film-laying surface 19 could be oriented axially and radially outwards, which would further reduce the film thickness.

[0068] To form the atomizer edge 20 and / or to reduce dead-stream regions at its downstream ends, the outer wall 24 and the inner wall 26 taper continuously towards their downstream ends 21, 27 within a downstream section 31 of the injector element 17. The downstream ends 21, 27 have the smallest possible radial thickness, preferably such that their mechanical stability is ensured.

[0069] Fig. 2B shows a cross-section AA, as designated in Fig. 2A, orthogonal to the longitudinal axis L, with the injector element 17 within the axial region with the cylindrical wall guide and the constant flow cross-sections, upstream of the downstream section 31. A 25823-PCT - JF / bau - 17 - 11 December 2025

[0070] Fig. 2C shows a cross-section BB, as designated in Fig. 2A, orthogonal to the longitudinal axis L, with the injector element 17 within the axial region of the downstream section 31, almost at the fuel supply opening 25. As can be seen in Fig. 2C, in this region the outer wall 24 and the inner wall 26 are radially much thinner, and the annular channel 28 has a significantly lower radial height than in the cross-section AA according to Fig. 2B.

[0071] Preferably, the wall thickness of the outer wall 24 is reduced on its radially outer side, i.e. by an outer surface of the outer wall 24 running slightly conically inwards in the flow direction within the downstream section 31 of the injector element 17.

[0072] The wall thickness of the inner wall 26 is preferably reduced by having an inner surface of the inner wall 26 taper slightly outwards in the direction of flow. With respect to the inner wall 26, its outer surface 29 also tapers slightly outwards in the direction of flow to reduce the radial height of the annular channel 28, in this case to a lesser extent than its inner surface, in order to create the narrowing towards the downstream end 27.

[0073] This design of the inner wall 26 also advantageously results in an increase in the flow cross-section of the inner channel 34. In this way, the velocity of the inner flow 36 is advantageously further reduced, thereby forcing a shear layer between the inner flow 36 and in the outer flow 32 and thus improving atomization.

[0074] The inner channel 34 and the outer channel 30 are designed such that, at the downstream end 21 of the injector element 17, the flow velocity of the oxidizer 38 through the inner channel 34 is at least 25%, preferably at least a factor of 2, e.g., a factor of 3 to 5, lower than the flow velocity of the oxidizer 38 through the outer channel 30. A 25823-PCT - JF / bau - 18 - 11 December 2025

[0075] The design is carried out in particular by means of approximate design calculations, using computer-aided flow simulation (CFD) and / or experimentally.

[0076] As shown in Fig. 2A, optional microstructures 42 (three by way of example) can be provided on the film laying surface 19 to improve atomization. In this example, the microstructures 42 are convex, i.e., they form a radially inwardly directed elevation relative to the rest of the film laying surface 19. The microstructures 42 have, for example, a height of at most the radial height of the fuel supply opening 25, e.g., at most half its radial height, and / or at least one-fifth or one-quarter of the radial height of the fuel supply opening 25, as well as an axial length of, for example, at most twice, preferably at most once, the radial height of the fuel supply opening 25.

[0077] In the embodiment shown in Fig. 2A, the microstructures 42 are, by way of example, each formed at a constant axial position completely circumferentially around the longitudinal axis L and, for example, equidistant from each other axially one behind the other.

[0078] A swirl arrangement 41 (indicated by dashed lines in Fig. 2A) can advantageously be arranged in the inner channel 34 to impart a slight circumferential swirl to the inner flow 36. The swirl number is preferably less than 0.5, particularly less than 0.3, e.g., 0.2 or less, at an axial distance from the atomizer edge between 0.5 and 1 times the diameter of the inner channel at the level of the atomizer edge 20. This allows for a fuel distribution advantageous for atomization in the area downstream of the atomizer edge 20. The swirl number is such that no recirculation zone is initiated, as is the case with swirl-stabilized burner concepts. In this way, the stabilization of combustion within the combustion chamber 3 (see Fig. 1) continues to be achieved by means of the large-scale recirculation zone due to the high axial impulse. A 25823-PCT - JF / bau - 19 - 11 December 2025

[0079] During operation, oxidizer 38 flows from the distributor side 2 through the inlet opening 15 into the feed nozzle 10. At the film laying device 18, the entire oxidizer flow through the feed nozzle 10 is split into the outer flow 32, which flows through the outer channel 30, and the inner flow 36, which flows at a lower velocity through the inner channel 34.

[0080] The liquid fuel 40, shown here as an example, is added to the annular channel 28 and flows through it to the fuel supply opening 25. Through the fuel supply opening 25, the fuel 40 flows onto the film laying surface 19, whereby, due to the small radial height of the annular channel 28 or the fuel supply opening 25, an extremely thin, continuously uniform fuel film is formed.

[0081] Due to the essentially axial orientation of the inner wall 26, the outer wall 24 with the film-laying surface 19, and the annular channel 28, the material flows—the inner flow 36, the outer flow 32, and the fuel 40—also exist at and immediately downstream of the atomizer edge 20 with a substantially axial directional component and are coaxial to each other. This flow pattern, as well as the thin-walled design of the inner wall 26 and the outer wall 24 with their continuous tapering, contributes to a flow that is at least virtually free of material separation at and downstream of the atomizer edge 20, thus avoiding local recirculation zones.

[0082] The inner flow 36 propels the fuel film to the atomizer edge 20, possibly accelerated by the slight circumferential swirl of the inner flow 36. At the atomizer edge 20, the inner flow 36 and the outer flow 32 meet, forming a shear layer due to the velocity difference. At the sharp atomizer edge 20, the high axial momentum of the oxidizer flow and the shear layer atomize the fuel film into fine droplets. Due to the flow path being essentially free of local recirculation zones, the high axial momentum and the pronounced shear layer form the dominant flow structure for atomization. The fuel droplets are carried further downstream by the oxidizer flow towards the outlet opening 12.

[0083] The comparatively high axial momentum of the external flow 32 ensures that the fuel droplets do not wet the nozzle wall 16, but are instead carried as completely as possible into the combustion chamber 3 by the oxidizer flow. Combustion of the oxidizer-fuel mixture takes place in the combustion chamber 3, with the flame zone being stabilized by the large-scale recirculation zone induced by the high axial momentum of the oxidizer.

[0084] Investigations by the inventors have, for example, revealed a very small droplet diameter of less than 20 pm across the entire feed nozzle 10. This results in advantageous vaporization and emission characteristics for the burner system 4.

[0085] The investigations have shown that advantageous operation using the feed device 1 described above is possible with a comparatively very compact design. In addition to liquid fuels, gaseous fuels can also be advantageously used with the same feed device 1, thus ensuring high fuel flexibility.

[0086] For example, a single feed unit can be designed for operation at a thermal output of, for example, between 1 kW and 100 kW (e.g., 0.1 to 10 kW per mm diameter of the feed nozzle) (scaling up or down is possible). In this way, both applications with comparatively moderate power density and / or moderate energy requirements (e.g., in decentralized energy conversion) and, for example, by using a large number of feed units 1 in a burner system 4, applications with high power requirements and / or power density (e.g., aerospace applications) can be served. A 25823-PCT - JF / bau - 21 - 11 December 2025

[0087] Fig. 3 shows a further embodiment of the feed device 1 according to the invention in a longitudinal section. The nozzle wall 16 of the feed nozzle 10 is indicated schematically.

[0088] The injector element 17 shown in Fig. 3 has an inlet geometry for the fuel 40 and the oxidizer 38 in an inlet area 13 on the upstream side. The inlet area 13 comprises, for example, three discrete fuel channels 44, which open into the annular channel 28 from a central supply opening 43 for the fuel 40 arranged on the longitudinal axis L. Circumferentially, alternating with these, air channels 45 are provided for supplying the oxidizer 38 into the inner channel 34. The inlet geometry serves to integrate the injector element 17 into the burner system 4 and is designed accordingly for the specific burner.

[0089] For positioning within the nozzle channel 14, the injector element 17 can have several support elements 46 on its radial outer surface. The support elements 46 can also be designed to adjust a specific pressure drop in the outer channel 30 during operation (e.g., at a design operating point) in order to selectively adjust the mass flow rate of the outer flow 32 and / or the ratio of the outer flow 32 to the inner flow 36. In this way, the defined velocity difference between the outer flow 32 and the inner flow 36 can be achieved.

[0090] In the embodiment shown in Fig. 3, the annular channel 28 does not have a purely cylindrical section. Rather, the downstream section 31, beginning here by way of example with the tapering of the inner wall 26, connects directly to the inlet area 13. The inner surface 23 of the outer wall 24 is, by way of example, formed at least substantially cylindrically over the entire length of the annular channel 28, corresponding to the length of the downstream section 31. A 25823-PCT - JF / bau - 22 - 11 December 2025

[0091] By means of advantageous design parameters, comprising the essentially axial orientations with at most very small angles with respect to the longitudinal axis L in the wall profiles and / or surface guides of the inner wall 26 and the outer wall 24, and / or the low height of the fuel supply opening 25 and the downstream ends, the advantageous flow guidance accompanied by positive atomization is also achieved in the embodiment shown in Fig. 3.

[0092] In summary, by means of the advantageous measures described above (individually or in combination), a feed device 1 is provided by means of which a burner system 1, designed according to the concept of a recirculation-stabilized jet flame burner for at least substantially non-swirling high-speed combustion, can be operated stably, reliably and with extremely low emissions using both liquid and gaseous fuels with a comparatively short flame length. In this way, a compact and advantageous burner system 4 is obtained.

Claims

Claims 1. Feed device (1), in particular for use in a gas turbine, for supplying oxidizer (38) and fuel (38) into a combustion chamber (3), comprising - a feed nozzle (10) with a nozzle channel (14) enclosed by a nozzle wall (16) and aligned along a longitudinal axis (L), in particular cylindrical, which opens into a combustion chamber-side outlet opening (12) adjacent to the combustion chamber (3), and - a particularly cylindrical injector element (17) for fuel injection, within which an inner channel (34) is formed for directing an internal flow (36) to the oxidizer (38), wherein an atomizing edge (20) is formed at a downstream end (21) of the injector element (17), wherein an outer channel (30) is formed between the nozzle wall (16) and the radial outer surface of the injector element (17) for the swirl-free directing of an external flow (32) to the oxidizer (38), characterized in that the injector element (17) has an outer wall (24) and an inner wall (26) which are arranged coaxially to each other and between which an annular channel (28) is formed for fuel guidance to a fuel supply opening (25) for introducing the fuel (40) into the inner channel (34), which is formed by an inner surface (23) of the outer wall (24) and by an outer surface (29) is limited by the inner wall (26).

2. Feed device (1 ) according to claim 1 , characterized in that a narrowest flow cross-section of the annular channel (28) is arranged at and / or directly upstream of the fuel feed opening (25), wherein in particular the radial height of the annular channel (28) at the fuel feed opening (25) is a maximum of 200 pm, preferably a maximum of 100 pm.

3. Feed device (1) according to claim 1 or 2, characterized in that the injector element (17) is designed as a film laying device (18), wherein a film laying surface (19) is provided between the fuel supply opening (25) and the atomizing edge (20), at the downstream end of which the atomizing edge (20) is arranged.

4. Feed device (1) according to claim 3, characterized in that the inner wall (26) terminates upstream of the outer wall (24), wherein the film laying surface (19) is formed on the inner surface (23) of the outer wall (24).

5. Feed device (1 ) according to claim 3 or 4, characterized in that the film laying surface (19) is cylindrical and / or extending axially radially outwards in the flow direction, preferably at an angle to the longitudinal axis (L) of a maximum of 10°, preferably of a maximum of 7°, particularly preferably of a maximum of 5°.

6. Feed device (1) according to one of claims 3 to 5, characterized in that at least one microstructure (42) is arranged on the film laying surface (19), with a radial height of at most the radial height of the fuel supply opening (25), e.g. at most half the radial height of the fuel supply opening (25), and / or at least one fifth or one quarter of the radial height of the fuel supply opening (25), wherein the microstructure (42) is convex or concave relative to the film laying surface (19).

7. Feed device (1) according to claim 6, characterized in that, that at least one microstructure (42) is formed at a constant axial position and / or completely circumferentially around the longitudinal axis (L).

8. Feed device (1) according to one of the preceding claims, characterized in that the inner wall (26) and / or the outer wall (24) tapers towards its downstream ends (21, 27) within a downstream section (31) of the injector element (17), in particular with an angle of at most 7°, preferably at most 5°, particularly preferably at most 3° with respect to the longitudinal axis (L).

9. Feed device (1) according to one of the preceding claims, characterized in that the inner surface (23) and / or the outer surface (29) is cylindrical and / or conical, with a directional component of a maximum of 10°, preferably a maximum of 7°, particularly preferably a maximum of 5° or a maximum of 3°, with respect to the longitudinal axis, and / or that, in order to narrow the flow cross-section, in particular within the downstream section (31), the outer surface (29) extends axially-radially outwards in the flow direction, in the direction of the inner surface (23), and / or the inner surface (23) extends axially-radially inwards in the flow direction, in the direction of the outer surface (29).

10. Supply device (1) according to one of the preceding claims, characterized in that the flow cross-section of the inner channel (34) increases towards the downstream end (21) of the injector element (17).

11. Feed device (1) according to one of the preceding claims, characterized in that that an upstream end (22) of the injector element (17) is arranged downstream of an inlet opening (15) into the nozzle channel (14).

12. Supply device (1) according to one of the preceding claims, characterized in that the downstream end (21 ) of the injector element (17) is arranged axially upstream or at the level of the outlet opening (12).

13. Feed device (1) according to one of the preceding claims, characterized in that the nozzle channel (14) is cylindrical and / or has a constant diameter.

14. Feed device (1) according to one of the preceding claims, characterized in that the inner channel (34) and the outer channel (30) are designed such that at the downstream end of the injector element (21) the flow velocity through the outer channel (30) is greater than the flow velocity through the inner channel (34), e.g. by at least 25%, e.g. by a factor of 2 to 5.

15. Feed device (1) according to one of the preceding claims, characterized in that a swirl arrangement (41) for imprinting a slight circumferential swirl onto the internal flow (36), with a swirl number of less than 1, preferably less than 0.5, in particular less than 0.3, e.g. 0.2 or less, is arranged within the inner channel (34).

16. Feed device (1) according to one of the preceding claims, characterized in that that at least one fuel channel, preferably three fuel channels, are present, which runs through the outer channel (30) and leads into the ring channel (28).

17. Feed device (1 ) according to one of the preceding claims, characterized in that at least the injector element (17) is additively manufactured.

18. Burner system (4) with a burner head (7) comprising at least one feed device (1 ) according to one of the preceding claims and an end plate (6) via which the at least one feed device (1 ) opens into a combustion chamber (3) of the burner system (4), wherein the burner system (4) is designed for operation with a large-scale combustion chamber internal recirculation induced by the axial impulse of the incoming oxidizer fuel jets to stabilize a combustion zone in the combustion chamber (3).

19. Method for supplying oxidizer (38) and fuel (38) into a combustion chamber (3) by means of a supply device (1 ) according to one of claims 1 to 17, wherein liquid and / or gaseous fuel (38) is added to an oxidizer (38) by means of an injector element (17) arranged in a supply nozzle (10).

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