The proposed solution relates to a fuel nozzle for an engine, especially for an engine operated with hydrogen.
In engines that have been in customary practical use to date, for example those operated with kerosene as fuel, in a combustion chamber, the air and fuel are injected into a combustion space of the combustion chamber via at least one fuel nozzle, in order to provide an ignitable air-fuel mixture. The fuel nozzle for provision of the air-fuel mixture comprises a nozzle head having outflow openings at an end face of the nozzle head. This end face, in the intended installation state of the fuel nozzle, faces a combustion space of the combustion chamber. Typically, the fuel here is injected via a first outflow opening that appears to be circular at the end face. The first outflow opening for the fuel is thus configured in the manner of an annular gap. A second outflow opening for air to be injected, which is on the radial inside based on a main flow direction of the fuel to be injected, also typically has a circular progression at the end face. The same applies to at least one additional third passage opening at the end face of the nozzle head or at a passage opening that accommodates the nozzle head in a heat shield of the combustion chamber. The multiple different outflow openings for air and fuel thus typically each take the form of circular rings in the manner of annular gaps in terms of their cross section. This is then also regularly associated with a circular cylindrical design of the nozzle head of the fuel nozzle.
While the above-described configuration of a nozzle head of a fuel nozzle has proven itself for liquid fuel to be injected, for example kerosene, there is further need for improvement in respect of fuel nozzles for utilization in an engine with regard to engines operated with a gaseous fuel, e.g. hydrogen, and hence fuel to be injected in gaseous form.
In this respect, the proposed fuel nozzle provides a remedy.
Thus, a proposed fuel nozzle has, at an end face of its nozzle head, multiple first outflow openings for hydrogen to be injected and at least one second outflow opening for air to be injected for the provision of a hydrogen-air mixture. The at least one second outflow opening here has a polygonal cross section, and the multiple first outflow openings for the hydrogen are distributed at the end face around the at least one second outflow opening.
The solution proposed can achieve the effect that, at the end face of the nozzle head, a multitude of hydrogen injection streams in the direction of the combustion space can be provided, which exit in a distribution at the end face of the nozzle head. This especially includes the first outflow openings for the hydrogen to be introduced each having a first cross-sectional area and a first flow cross section which is merely a fraction of a second cross-sectional area or a second flow cross section possessed by the at least one second outflow opening for the air to be injected. In this way, in that case, for example in relation to the at least one second outflow opening, the first outflow openings for the hydrogen to be injected are virtually point openings, and consequently, in a front view of the end face, are a plurality or multitude of discrete exit holes that appear like dots and hence provide sources for a plurality or multitude of hydrogen inflows into the combustion space. The arrangement of the first outflow openings around the at least one second outflow opening permits, for a gaseous fuel to be injected (and hence more particularly for the provision of an ignitable hydrogen-air mixture), more advantageous mixture formation than in the case of fuel nozzles customary to date with a comparatively large-area first outflow opening in the form of a surrounding circular ring for the fuel to be injected.
Advantageous mixture formation, for example for an ignitable hydrogen-air mixture, is also assisted here by the polygonal cross section of the at least one second outflow opening intended for air to be injected. It is thus possible thereby to provide a geometrically comparatively sharply delimited air flow exiting at the end face of the nozzle head, around which a multitude of distinct hydrogen flows from the first outflow openings is generated.
For the configuration of the at least one second outflow opening for the air to be injected, a polygonal cross section in particular has been found to be advantageous. More particularly, the second outflow opening at the end face of the nozzle head may have a rectangle-shaped, especially rectangular, or trapezoidal cross section.
Alternatively or additionally, it may be the case that the at least one second outflow opening and/or at least one flow duct of the nozzle head that opens into the at least one second outflow opening has at least one air guide element for swirling of exiting air. The air to be injected is thus provided with a swirl via at least one air guide element at the at least one second outflow opening and/or upstream of the at least one second outflow opening in a flow duct of the nozzle head. The air flow exiting at the at least one second outflow opening thus has a rotational movement component which is beneficial for maximum homogeneity of mixture formation downstream of the nozzle head.
In one design variant, two or more second outflow openings at the end face are provided, around which the respective multiple first outflow openings for hydrogen to be injected are distributed. In such a design variant, for example, not just one single (central) second outflow opening for air to be injected is thus provided at the end face of the nozzle head. Instead, multiple (at least two) second outflow openings are present at the end face. In that case, multiple first outflow openings for hydrogen to be injected are arranged around each of these second outflow openings. In this way, it is possible to achieve the effect that each air flow from a second outflow opening is surrounded by multiple hydrogen flows from first outflow openings.
In one design variant, the two or more second outflow openings at the end face are arranged successively in a circumferential direction. The second outflow openings for air to be injected are thus alongside one another at the end face. In this case, the second outflow openings are alongside one another, for example, along a curved or linear profile line, such that, for example, a series of second outflow openings is provided at the end face, with each individual second outflow opening itself surrounded at the end face by a multitude of first outflow openings for hydrogen to be injected.
In one design variant, the multiple first outflow openings, for example, each have a circular, rhombus-shaped or hexagonal cross section. As already elucidated above, in particular, such a circular, rhombus-shaped or hexagonal cross section or a cross-sectional area of a first outflow opening thus defined at the first end face may be much smaller than a cross section or cross-sectional area of a second outflow opening for air to be injected. A cross-sectional area of a second outflow opening is, for example, many times larger than a cross-sectional area of a first outflow opening. In particular, in this connection, it may be the case that the cross-sectional area of a second outflow opening is at least five times greater than a cross-sectional area of each first outflow opening.
In one design variant of the solution proposed, the end face, in a rejection of configurations in customary practical use to date, is not circular, and hence the nozzle head is not necessarily in circular cylindrical form. Instead, the end face of the nozzle head, in one design variant, is quadrangular, especially rectangular. Accordingly, the cross section of the nozzle head at the end face is then also quadrangular, especially rectangular.
Alternatively or additionally, the end face of the nozzle head may have two main edges running essentially parallel to one another, which each extend along a circular arc, and two lateral edges that connect the main edges to one another. An outline of the end face here is consequently defined by the two main edges and the two lateral edges, with the two main edges each following a circular arc section and running essentially parallel to one another. More particularly, the end face of such a design variant may also be tetragonal and/or elongated based on a circumferential direction. In the installed state of the fuel nozzle, for example, such a circumferential direction may point circumferentially about a center axis of the engine along which different components of the engine, for example compressor, combustion chamber and turbine of the core engine, are arranged in axial succession, and which runs parallel to a main flow direction along which air flows through the engine.
The proposed solution also includes a combustion chamber assembly having a combustion chamber for an engine, in which at least one design variant of a proposed fuel nozzle for injection of a hydrogen-air mixture is provided.
A combustion chamber of such a combustion chamber assembly may have, for example, in the region of a combustion chamber head, a heat shield having a passage opening in which the nozzle head of the fuel nozzle is accommodated. The heat shield here typically faces the combustion space of the combustion chamber by an inner face. In order to additionally provide air in the combustion space beyond the nozzle head, it is possible to form at least one additional outflow opening between the nozzle head and an edge of the passage opening on the heat shield side. By means of this at least one additional outflow opening, air flowing past outside the nozzle head likewise gets into the combustion space in operation of the engine.
Especially for improvement of mixture formation and mixture guiding in the case of injection of gaseous fuels such as hydrogen and hence the operation of an engine with such a fuel, in one design variant, the at least one additional outflow opening is formed by a gap which is longitudinally extended with regard to the end face of the nozzle head and runs along a section of the outer circumference of the nozzle head.
In a first possible development, in that case, for example, at least two spatially separated additional outflow openings are formed between the nozzle head and the edge of the passage opening. There are thus local, mutually spatially separated additional (third) outflow openings for additional air flows by virtue of the passage opening on the heat shield side. Corresponding gaps can thus be provided, for example, at the outer circumference of the nozzle head in the case of an annular combustion chamber that extends around a center axis of the engine, firstly on the radial inside and secondly on the radial outside.
In an alternative configuration, an additional (third) outflow opening between the nozzle head and the edge of the passage opening is formed around the full circumference of the nozzle head. In such a configuration, in that case, for example, no individual additional outflow openings that are locally separated from one another are provided. Instead, in a front view of the end face of the nozzle head, for example, a gap running around the circumference of the nozzle head is apparent. Such a gap is, moreover, not in the form of a circular ring in one development. Instead, the additional outflow opening running around the full circumference of the nozzle head may have a rectangular outline.
Part of the proposed solution is also an engine having a design variant of a proposed combustion chamber assembly. For example, a hydrogen-driven engine is provided, which thus envisages, at a combustion chamber head of a combustion chamber of the combustion chamber assembly, at least one design variant of a proposed fuel nozzle for the effective provision of a hydrogen-air mixture.
The appended figures illustrate, by way of example, possible design variants of the proposed solution.
These show:
The block diagram of
In the operation of the engine 103, the low-pressure turbine 209 drives a fan 213 of the engine 103 via a (step-down) transmission unit 214. The transmission unit 214 is connected to the second shaft 212 on the drive side, and is coupled to the fan 213 via a fan shaft 215 on the output side. For example, the transmission unit 214 has an epicyclic step-down transmission. Alternatively or additionally, a planetary transmission may be part of the drive unit 214, although alternative drive designs are of course also possible. In principle, it is also possible to recess a transmission unit 214, such that the second shaft 212 driven by the low-pressure turbine is coupled directly to the fan 213.
From the high-pressure compressor 205, an air flow is guided through the diffuser 205 and lastly through pre-diffuser 6 into a housing space accommodating the combustion chamber 207. The air flow coming from the pre-diffuser 6 is divided here. A portion of the air flow is routed into the combustion space via the combustion chamber head 11, cooling air bores 10 in the heat shield 12, and the nozzle head of the fuel nozzle 7, in order to provide an ignitable air-fuel mixture therein. A further portion of the air from the pre-diffuser 6 flows in two (outer and inner) flow spaces 4 and 5 formed between an outer shell surface of the combustion chamber wall 1 and housings 2 and 3. A portion of the air flow flows here into the (outer) flow space 4 between the combustion chamber wall 1 and the outer housing 2 in which the combustion chamber 207 is fully accommodated. A further portion of air flow flows into the (inner) flow space 5 between the combustion chamber wall 1 and the radially inner housing 3. The air that passes into the inner and outer flow spaces 4 and 5 serves to cool the combustion chamber wall 1. For example, it is especially possible to guide (cooling) air from outside into the combustion chamber through cooling air bores 10 for more efficient cooling of the combustion chamber wall 1 and especially combustion chamber shingles provided thereon on the combustion space side. Furthermore, the combustion chamber wall 1 has additional air-mixing holes 9 in order to route a portion of the air from the flow spaces 4 and 5 into the combustion space as mixing air. Furthermore, air from the flow spaces 4 and 5 downstream of the combustion chamber 207 can also be utilized for cooling of the turbine stator 8.
For the provision of the ignitable air-fuel mixture, the fuel provided by the fuel injection system 206 is mixed with air in the fuel nozzle 7 in the region of the heat shield 12. For this purpose, a nozzle head of the fuel nozzle 7 is accordingly disposed at the combustion chamber head 11 of the combustion chamber 207. The nozzle head of the fuel nozzle 7 is provided here at an end of a nozzle stem 70 of the fuel nozzle 7 that projects radially inward, fixed on the outer housing 2 or a housing wall of this outer housing 2. In this case, the nozzle stem 70 projects through a passage hole 13 in the housing wall of the (outer) housing 2, and is secured with sealing via a securing flange 14 on the housing wall of the housing 2. In
A fuel nozzle 7 known from the prior art is illustrated in detail in
The fuel nozzle 7 has, within the nozzle stem 70, an internal fuel feed 17 via which fuel is supplied to a nozzle head 71 of the fuel nozzle 7. The nozzle head 71 is accommodated in a passage opening of the heat shield 12, in order to provide an ignitable fuel-air mixture via outflow openings 19′ and 21′ for air and fuel that are provided at an end face 710 of the nozzle head 71, downstream of the nozzle head 71 in the combustion space of the combustion chamber 207. In the nozzle head 71, the fuel passes from the fuel feed 17 into a distributor 20 via which the fuel can flow out downstream via a first outflow opening 21′ having a cross section in the form of a circular ring. The first outflow opening 21′ for the fuel is formed here at the nozzle head 71 in a cross section akin to an annular gap. This is also apparent in the cross-sectional view of
At the end face 710 of the nozzle head 71, a (first) air flow is generated via a central second outflow opening 19′, which is radially further inward, based on the first outflow opening 21′ for the fuel in the form of a circular ring. Additional air flows are provided via additional outflow openings 23′ that are radially further outward. These additional third outflow openings 23′ may be provided in the nozzle head 71 itself, but are radially further outward and are not formed on a core of the nozzle head 71 in which the distributor 20 for the fuel is formed.
In a flow duct that opens within the central second outflow opening 19′, and in flow ducts that each open within one of the additional third outflow openings 23′, air guide elements 22 may be provided for swirling the respective air flow. Such air guide elements 22 (also called swirl elements) thus cause the air to flow out with an additional momentum, which improves mixture formation.
With reference to the view of the end face 710 of the nozzle head 71 which is shown in
While the design of a fuel nozzle according to
In this case, each of the design variants at the end face 710 of the nozzle head 71 of the fuel nozzle 7 envisages multiple first outflow openings 21 for hydrogen to be injected and at least one second outflow opening 19 for air to be injected. The at least one second outflow opening 19 is designed here with a polygonal cross section, or a polygonal cross-sectional area for flow, and multiple first outflow openings 21 for the hydrogen are distributed at the end face around the at least one second outflow opening 19 in each case.
In each case here, for example, in accordance with the lateral section view of
In the design variant of
The cross sections of the first inflow openings 21 may, for example, in accordance with
The nozzle head 71 of the fuel nozzle 7 of
In the design variant of
A central second outlet opening 19 for air to be injected, in the design variant of
At a radially outer edge of the nozzle head 71 and a radially outer edge of the passage opening in the heat shield 12 is provided a narrow gap that extends in circumferential direction u as one of two additional third outflow openings 23.1 and 23.2 for an additional air flow. Spaced apart radially therefrom, at a radially inner edge of the nozzle head 71, a second gap is accordingly formed for an additional outflow opening 23.2, in interplay with the passage opening on the heat shield side.
In the design variant of
In the installed state of the fuel nozzle 7 of
In a possible development according to
In the alternative design variant of
Although a proposed fuel nozzle is described above as being especially suitable for the injection of hydrogen, a proposed fuel nozzle will of course also be suitable for the injecting of other liquid or gaseous fuels, for example for the injecting of methane. The multiple first outflow openings 21 may thus also be provided for another fuel to be injected, and in this case may each be arranged distributed around at least one second outflow opening 19 for air to be injected.
Number | Date | Country | Kind |
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10 2021 110 616.8 | Apr 2021 | DE | national |