Patent Application
20250237381
This application claims priority to German Patent Application 102024200444.8 filed Jan. 18, 2024, the entirety of which is incorporated by reference herein.
The invention relates to a nozzle assembly for a combustion chamber of an engine, having at least one nozzle for injecting fuel into a combustion space of the combustion chamber, wherein the nozzle comprises a nozzle main body, which extends along a nozzle longitudinal axis and has a nozzle head, and a nozzle bracket, which is connected to the nozzle main body and has at least one fuel feed line, wherein the nozzle main body comprises a central fuel pipe, which extends along the nozzle longitudinal axis and has a fuel outlet opening, and at the nozzle head there is at least one air-guiding duct, spaced apart radially from the fuel pipe, with an air outlet opening.
A nozzle assembly of this kind, which is optimized in particular for use with hydrogen or a hydrogen-containing combustion gas as fuel, is specified in WO 2023/180315 A2. As a result of the configuration as proposed in WO 2023/180315 A2, a favourable flow field is generated in the combustion chamber during operation, for safe and low-emission combustion of the fuel, in particular hydrogen.
Other known burners, in which at least one air-guiding duct is arranged around at least one central fuel pipe, are specified in CN 103672969 B, EP 2 515 042 A2 and EP 28 703 45 A1.
WO 01/55646 A1 discloses a natural gas burner having a central igniter, which is designed to premix air and fuel upstream of an outlet opening into the combustion space.
During operation with hydrogen, in the case of a nozzle assembly known, for example, from WO 2023/180315 A2, a considerable cooling action occurs on the fuel-conducting part and component structures, surrounding the latter, of the nozzle on account of the high volumetric flow with, at the same time, a relatively low fuel temperature. At the same time, on account of its proximity to the combustion chamber, the air-conducting part of the nozzle head, with swirl elements preferably arranged therein, experiences a high level of heat input from the combustion space. The resulting high temperature differences between the metal components associated with high thermal stresses can lead to cracks in particular at the joints at the nozzle main body, in particular the surrounding air-guiding ducts and swirl elements integrated therein, with the result that the component can fail during operation.
Therefore, the invention addresses the problem of providing a durable and safe nozzle assembly in particular for operation with hydrogen or a hydrogen-containing combustion gas as fuel.
The problem is solved for the nozzle assembly by the features of Claim 1. Provision is made therein for the nozzle assembly to have a burner seal for providing sealing with respect to a combustion chamber head, said burner seal being formed and arranged spatially separately from the nozzle main body, wherein the at least one air-guiding duct is formed and arranged, preferably only, in the burner seal. In this way, the air-guiding function, for guiding combustion air into the combustion space, is at least substantially decoupled from the nozzle main body and integrated into the burner seal of the nozzle assembly. The nozzle main body serves at least substantially only for feeding fuel into the combustion chamber. In this way, critical structures at which thermal stresses can lead to cracks, such as joints of the guide vanes and/or of the at least one swirl element at the at least one air-guiding duct, are thermally decoupled from the nozzle main body and thus the cooling action of the fuel is reduced to same.
The burner seal comprises in particular a softer material than the nozzle main body, and has in particular a nickel-based alloy, or is formed therefrom, for example Hastelloy x.
Favourable flow conditions in the fuel chamber for optimized combustion can be achieved in that there are at least two air-guiding ducts that are spaced apart radially from one another, wherein at least a radially outer air-guiding duct is formed and arranged entirely and/or at least a radially inner air-guiding duct is formed and arranged at least partially in the burner seal. Preferably, the axial length of the air-guiding ducts corresponds to the axial length of the burner seal, and/or the air-guiding ducts are in the form of annular ducts arranged (preferably only) coaxially with the fuel pipe. Upstream of the burner seal or of the air-guiding ducts, the air flows up to the nozzle assembly in a total flow.
Favourable flow conditions are also or alternatively achievable in that a (at least one) swirl element for swirl generation is arranged in the burner seal, in the at least one air-guiding duct, preferably in the radially outer air-guiding duct, and/or at least one guide vane for targeted flow guidance and/or swirl generation in an air flow flowing through it is arranged preferably in the radially inner air-guiding duct. Particularly preferably, the air-guiding ducts are designed such that an air flow with a high axial impulse and/or without or at least with less swirl is conditioned in the radially inner air-guiding duct than in the outer air-guiding duct.
In a particularly preferred design variant, the narrowest flow cross section of the radially outer air-guiding duct is designed to be larger, preferably by at least a factor of 2, 4 or 6, than the narrowest flow cross section of the radially inner air-guiding duct. In this way, a much greater air fraction flows through the radially outer air-guiding duct than through the radially inner air-guiding duct.
In one design variant, provision may be made for the at least one or at least one of the air outlet opening(s), in particular the radially outer air outlet opening, to be arranged in an axially set-back manner with respect to the fuel outlet opening, and/or, when there are a plurality of air-guiding ducts, for the air outlet opening of the radially inner air-guiding duct and/or of the radially outer air-guiding duct to be arranged axially at the level of the fuel outlet opening.
Provision is particularly preferably made for the nozzle main body and the burner seal to be in contact in an axially, possibly also peripherally or tangentially, movable manner with respect to one another by means of at least one contact element, wherein they are not fastened (for example joined) together. In this case, the separation is arranged on the radially inner side or radially outer side of the at least one contact element, wherein the contact element is fastened only to one of the components (burner seal or nozzle main body). The at least one contact element is preferably formed in a corresponding manner, in order to permit such a movement between the components in a simplified manner, for example by means of at least one bulge, rounded portion and/or bevel.
In this case, the at least one contact element may be in the form of a, preferably entirely circumferential, contact ring and be fastened to the nozzle main body and/or to the burner seal and/or be integrated integrally in same. The contact ring is in this case assigned to the burner seal and/or the nozzle main body.
In particular alternatively, provision may be made for the at least one contact element to be formed from the at least one guide vane or to comprise same, which is formed at the same time as a spacer element (and/or has the function thereof). The guide vane(s) is/are fastened in particular to the burner seal and are in contact with the fuel-pipe wall, which then at least partially forms a radially inner wall of the (inner) air-guiding duct.
For improved movability and/or installation options, the at least one contact element has a bevel and/or a rounded portion at least at one, for example its upstream, axial end.
Axial sliding can in particular be simplified when the at least one contact element, in particular the contact ring, is formed, on the radial side in contact with the other component (nozzle main body or burner seal), so as to have a curved axial profile, in particular to form a bulging sealing surface. On account of the bulge, in particular the contact surface with the respectively other component is reduced in size, and in limiting cases becomes an (in particular circumferential) contact line.
In order for it to be easier to insert the nozzle main body into the installed burner seal, the at least one contact element, preferably the contact ring, for example, comprises, at its upstream end, a collar which is open radially towards the outside at an angle α. The angle α is, for example, between 3° and 30°, in particular between 5° and 15°. In this way, the angle α is as small as possible in order to influence the incident air flow as little as possible. For streamlined shaping and/or shaping that makes nozzle installation easier, the collar has, at its upstream end, preferably a bevel of between 30° and 60° (with regard to the collar), for example 45°. The axial extent of the collar is, for example, at most the axial length or at most half the length of the nozzle head DK, and at least the length of the bevel in the portion of the contact element that is arranged upstream of the inlet opening. When the nozzle is inserted during installation, the nozzle head can be captured easily by the collar and guided into the correct installation position. The collar forms preferably the axial end portion, arranged upstream, of the contact element or contact ring. The collar can also serve as an axial stop during installation of the nozzle, wherein the nozzle head is introduced into the burner seal until the nozzle main body comes into contact with the collar.
Provision is preferably made for the collar to be arranged axially upstream of an inlet opening of the at least one air-guiding duct, in particular of the radially inner air-guiding duct (or of the air-guiding duct on the wall of which it is arranged), for example at least far enough upstream for the flow cross section between the radial collar outer side and the outer wall of the inner air-guiding duct not to be narrower at the inlet opening into the inner air-guiding duct than the flow cross section through the inner air-guiding duct itself. Preferably, the collar also does not project radially into the incident-flow region of the at least one other air-guiding duct, in particular of the outer air-guiding duct, i.e. into the radial region of the inlet opening thereof or into the upstream axial continuation of the inner wall of the outer air-guiding duct. In this way, constriction of the flow cross section of the inner air-guiding duct by the collar is avoided and/or influencing of the flow upon flowing into the air-guiding ducts is reduced.
In a preferred design variant, the contact ring and/or a radially inner ring of the burner seal is arranged in an axially set-back manner with respect to the air outlet opening of the at least one, preferably of the inner, air-guiding duct (upstream of the air outlet opening), wherein the radially inner side of the air-guiding duct is formed in an upstream portion by the contact ring and/or the inner ring (wherein the contact ring may form the radially inner ring of the burner seal and/or may be arranged thereon) and in a downstream portion by the fuel pipe, in particular a fuel-pipe wall (the wall of the fuel pipe), of the nozzle main body. Preferably, the downstream portion is shorter than the upstream portion. The transition from the upstream portion into the downstream portion is preferably formed in a streamlined manner, for example by means of a slope and/or curved shaping arranged in between, resulting in a “serpentine” course of the inner air-guiding duct. The outer air-guiding duct is preferably guided at least substantially parallel thereto, such that the radial spacing between the inner and the outer air-guiding duct is substantially constant within the two portions, and/or preferably in such a way that the flow cross section is substantially constant. In this way, the air outlet opening of the inner air-guiding duct is advantageously located radially closer to the fuel outlet opening, such that unfavourable flow conditions on entry into the combustion chamber, in particular stagnation zones, are avoided.
Favourable flow conditions for promoting mixing of fuel and air while avoiding stagnation zones on entry into the combustion chamber are achievable in that the fuel pipe has a bevel at its downstream end (at the fuel outlet opening). The bevel opens radially towards the outside and is preferably formed with an angle of between 30° and 60°, for example 45°.
Particularly preferably, the at least one guide vane is arranged in the upstream portion. In this way, the guide vane(s) is/are thermally decoupled from the fuel pipe in support of the reduction in thermal stresses.
It is conducive to the durability of the burner seal when at least one cooling duct, extending for example at least partially parallel to or coaxially with the nozzle longitudinal axis, is arranged in the burner seal, preferably in a radially outer ring, said cooling channel radially surrounding in particular the, possibly outer, air-guiding duct.
In order to have as little influence on the flow conditions in the combustion chamber as possible, preferably a downstream (end) portion of the at least one cooling channel, leading into the combustion chamber, is oriented towards the outside with, preferably only, a radial directional component. Preferably, the downstream portion of the cooling duct is arranged so as to extend at right angles towards the outside with respect to the upstream portion of the cooling duct.
To avoid excessive movement, in particular rotation, of the burner seal, preferably at least a part of a securing arrangement for securing the burner seal is present in a tangential and/or axial direction, for example on a structure surrounding the burner seal. The secured burner seal preferably continues to exhibit play in particular in the circumferential direction.
In one possible design variant, the securing arrangement comprises an (axial) thickened portion on a radially externally circumferential fastening collar of the burner seal, for projecting (axially) into a corresponding recess, for example a slot, in a structure radially externally surrounding the burner seal, for example the fuel chamber head and/or a heat shield, into which the fastening collar has been inserted. By means of such a design, the burner seal is secured to the surrounding structure.
In an alternative or additional possible design variant, the securing arrangement is formed between the nozzle main body and the burner seal, wherein a partially circumferential clearance, extending for example over an angular range of between 15° and 120°, preferably 45° and 110°, in particular 100°, is arranged at the upstream end of the contact ring and/or inner ring, and the nozzle main body has, on the outer side of the fuel pipe (in particular of the fuel-pipe wall), a radial thickened portion which projects into the partially circumferential clearance, wherein in particular the radial thickened portion exhibits at most half, preferably at most a quarter, of the circumferential extent of the partially circumferential clearance. On account of the clearance in the burner seal being formed extensively in the circumferential direction (tangential direction), the radial thickened portion can be inserted relatively easily into the clearance during installation of the nozzle. Following installation, the burner seal rotates in the circumferential direction during operation until it butts against the radial thickened portion and is thus radially secured. The thickened portion also serves as a stop in the axial direction during installation.
In one possible design variant, at least one central flow body may be arranged in the fuel pipe, and at the outer lateral surface of said flow body, fuel fed by means of the fuel pipe can flow in the direction of the fuel outlet opening, via which fuel is able to be introduced into the combustion space. A design without a central flow body in the fuel pipe is also possible.
The invention will be explained in more detail in the following text by way of exemplary embodiments with reference to the drawings, in which:
Such a configuration of a nozzle D is disadvantageous under certain circumstances, in particular for fuel, in particular hydrogen, that is to be injected into the combustion space 1030 in gaseous form.
Accordingly, a nozzle assembly developed for the optimized injection of gaseous fuel, in particular hydrogen, is presented in WO 2023/180315 A2. A nozzle assembly of this kind is illustrated schematically in longitudinal section in
In this known nozzle assembly, on a nozzle main body DR of the nozzle D, a central fuel pipe 3 is present which extends along the nozzle longitudinal axis L and is sealed off to prevent an inflow of air, and through which fuel is able to be conducted within the nozzle main body DR as far as a fuel outlet opening 33, present at a nozzle end of the nozzle D, of the fuel pipe 3. From the fuel outlet opening 33, the fuel is then able to be introduced into the combustion space 1030 in order to be mixed with air for the first time.
Arranged centrally on the nozzle longitudinal axis L, there is preferably at least one, in this case for example two flow bodies 30A, 30B that are spaced apart axially from one another. Via the flow bodies 30A, 30B, the fuel flow can be influenced, for example homogenized and/or deflected into a desired direction of flow. Furthermore, at least one fuel swirl element 31 is located preferably within the fuel pipe 3. In the present case, by way of example, the flow body 30B that is arranged downstream is fastened to the inner side of the fuel pipe 3 by means of supporting struts 303.
In the case of the nozzle assembly shown in
Preferably a plurality of guide vanes 52, for example for imparting a tangential directional component on the air flow in the manner of a swirl element during operation, are arranged in the inner air-guiding duct 4. At least one swirl element 51 is arranged in the second air-guiding duct 5.
The central, sealed-off guidance of the fuel in the fuel pipe 3 is advantageous in particular for highly flammable hydrogen, in order to avoid flashback and premature autoignition in the vicinity of the nozzle D or within the nozzle D. The air flow provided via the at least one air-guiding duct, preferably the air-guiding ducts 4 and 5, furthermore creates an advantageous recirculation zone downstream of the nozzle D in the combustion space 1030.
As is apparent from
From the radially inner air-guiding duct 4, which is preferably in the form of a narrow annular gap, air passes from the air outlet opening thereof into the combustion space 1030 preferably with a relatively large axial impulse and without or with little swirl. The air flow passing out of the radially outer air-guiding duct 5, which is preferably in the form of an annular duct, in turn exhibits an intense swirl. In this way, an air-rich zone enveloping the central fuel flow is created, which is denoted as an outer recirculation zone ORZ in
In particular when hydrogen is used as gaseous fuel, the fuel pipe 3 is cooled during operation by the high volumetric flow of relatively cool gas. The air-conducting part of the nozzle head DK, with the at least one swirl element 51, is arranged close to the combustion chamber 103 and thus experiences a high level of heat input from the combustion space 1030. As a result of the high density-based cooling action of the gaseous fuel, in particular hydrogen, on the material of the fuel pipe 3 (metal), large temperature differences arise between the metal components. The resultant high thermal stresses can result in cracks in particular at the joints at the nozzle main body DR, in particular the surrounding air-guiding ducts 4, 5, the guide vanes 52 and/or the at least one swirl element 51, with the result that the component can fail during operation.
To solve this problem, the nozzle assembly according to the invention is proposed, wherein at least the outer air-guiding duct 5, with the swirl element 51, is formed separately from the nozzle main body DR and is integrated in the burner seal 13, i.e. formed and arranged in same.
In
The fuel assembly has, for example, the two air ducts 4, 5, which, in the conventional nozzle assembly according to
The burner seal 13 is arranged, structurally separately from the nozzle main body DR, radially circumferentially around the outer air-guiding duct wall 55. The burner seal 13 is in sealing contact with the nozzle main body DR by means of an axially extending, circumferential contact ring 131. In addition, the burner seal 13 has a radially extending, circumferential fastening collar 130. By way of the fastening collar 130, the burner seal 13 and/or the nozzle assembly can be secured to a structure surrounding the burner seal 13, in particular to the combustion chamber head 14 (cf.
As
Thus, in the present case, the nozzle main body DR and the burner seal 13 are not in contact by means of the sealing contact ring 131, but with the inner air-guiding duct 4 arranged in between. In this case, the guide vanes 52 are preferably at the same time in the form of spacer elements by means of which the burner seal 13 can slide axially on the nozzle main body DR. As
The central air-guiding duct wall 46 is formed by an inner ring 132, encircling the fuel-pipe wall 34, of the burner seal 13. The outer air-guiding duct wall 55 is formed by a circumferential outer ring 134 of the burner seal 13. In the present case, the outer ring 134 has, for example, different axial lengths over its radial thickness, wherein the radially inner part corresponds substantially to the axial length of the swirl element 51. The outer ring 134 is adjoined by the circumferential fastening collar 130.
The air ducts 4, 5 are preferably integrated along their entire axial length in or on the burner seal 13, as is the swirl element 51.
The contact ring 131 has a curved sealing surface 15 on its radially inner side, along its axial course. The curvature of the curved sealing surface 15 serves as an installation aid, wherein the insertion of the nozzle main body DR and the axial sliding between the burner seal 13 and the nozzle main body DR are made easier.
As an additional installation aid, the contact ring 131 has, at its upstream end, an in particular circumferential collar 135, which opens radially towards the outside at an angle α. A bevel is preferably arranged at the upstream end of the collar 135. The angle α is, for example, between 3° and 30°, in particular between 5° and 15°. When the nozzle D is inserted during installation, the nozzle head DK can be captured easily by the collar 135 and guided into the correct installation position.
Preferably, the collar 135 is arranged only at or upstream of an air inlet opening of the inner air-guiding duct 4, in order not to effect any constriction of the flow cross section at or within the air-guiding duct 4. Radially, the collar 135 does not project into the region of the outer air-guiding duct 5.
For conducting air, the burner seal 13 additionally has a radially central ring 133 which forms the central air-guiding duct wall 46 between the radially inner air-guiding duct 4 and the radially outer air-guiding duct 5.
In the present case, by way of example, the contact ring 131 of the burner seal 13 is arranged in an axially set-back manner with respect to the air outlet opening of the radially inner air-guiding duct 4. As a result, in a downstream portion 4A that leads into the air outlet opening, the radially inner air-guiding duct wall 45 is formed by the fuel-pipe wall 34. In an upstream portion 4B that extends away from the air inlet opening, the radially inner air-guiding duct wall 45 is formed by the burner seal 13, in particular by the contact ring 131. The downstream portion 4A is preferably shorter than the upstream portion 4B. The guide vanes 52 are preferably arranged in the upstream portion 4B. As a result of this design, the cooling effect of the fuel on the guide vanes 52 and/or the joints for the securing thereof is reduced. At the same time, at the air outlet opening, the air flow is guided, during operation, radially as close as possible up to the fuel, passing out of the fuel outlet opening 33, of the nozzle main body DR, in order to avoid an unfavourable flow field, in particular stagnation zones at the outlet openings for air and fuel.
To avoid unfavourable flow conditions, use is also made of an outwardly opening bevel of between 30° and 60°, in particular 45°, which is arranged at the downstream end of the fuel-pipe wall 34.
The transition between the upstream portion 4B and the downstream portion 4A is preferably formed in a streamlined manner by means of a slope, wherein any edges are preferably rounded off (apparent in particular in
As
As
In the exemplary embodiment shown in
In
In
In one of the design variants, in this case the left-hand view, the burner seal 13 has, in the portion arranged upstream, an additional element which forms the contact ring 131, which is present here in addition to the inner ring 132 of the burner seal 13 only in the portion of the burner seal 13 that is arranged upstream. The inlet opening of the air-guiding duct 4 is formed between the contact ring 131 and the inner ring 132.
In the other design variant, in this case the right-hand view, the inner ring 132 has been extended parallel to the nozzle longitudinal axis L into the portion arranged upstream. At the upstream end, the inner ring 132 may have a collar 135. In the portion arranged upstream, the inner ring 132 bears on the fuel pipe 3 and thus, at the same time, forms the contact ring 131. The inlet opening of the air-guiding duct 4 is formed as a radial, for example aperture-like, opening 41 in the inner ring 132 in the portion arranged downstream, but upstream of the air-guiding duct 5, wherein a plurality of openings 41 are preferably present circumferentially.
In both design variants, the cooling duct 17 is present, wherein
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2024 200 444.8 | Jan 2024 | DE | national |
