Patent Application
20240392963
The disclosure relates to a burner for a turbine having a multiplicity of curved swirl channels, through which a fuel-air mixture flowing through the swirl channels is subjected to a swirl, and to a method for producing such a burner.
Burners, such as for example for gas turbines, utilise gas as fuel so that in burners a gas-air mixture or generally a fuel-air mixture is mostly combusted.
In principle, the use of liquid fuels in a burner is also possible.
Low-pollutant burners normally mix air and fuel prior to the combustion in order to avoid temperature peaks and thus pollutant emissions.
For this purpose, burners designed as swirling-flow burners are generally used in the prior art that use radial or axial swirl cascades to impart a swirl to the fuel-air mixture.
In the case of highly reactive fuels, such as hydrogen, a low-pollutant combustion is difficult since the fuel-air mixture combusts so rapidly that the flame flashes back. For this reason, such fuels or such mixtures are frequently combusted without pre-mixing.
Occasionally, burners also referred to as jet burners are employed for combusting highly reactive fuels. With such jet burners, a swirl cascade or generally subjecting the mixture to a swirl is omitted and the flame stabilised on free jets.
This has advantages in the flash-back strength but is at the expense of the flame stability and emissions. Here, the air flows through individual tubes that are arranged completely straight and parallel to one another and is mixed with fuel in the tubes. At the outlet of the burner, the fuel combusts in many small jets. The jet burner has a greater flash-back strength since the entire air or the mixture is conducted axially.
Apart from this, the dwell times compared with a swirling-flow burner are shorter and the NOx emissions at very high temperatures are lower.
By contrast, the swirling-flow burner offers a substantially better stability and better part load emissions. The mixing sections with swirling-flow burners are often longer which makes possible a good mixing of air and fuel.
One aspect of the invention is overcoming the aforementioned disadvantages and providing a burner that makes possible both a high flash-back strength and also a good mixing of air and fuel and at the same time has a stable combustion behaviour, so that in particular hydrogen or hydrogen gas can also be combusted as fuel with low emission.
According to one aspect of the invention, a burner with a combustion space, a multiplicity of swirl channels is proposed, wherein a swirl channel comprises at least one fuel nozzle for introducing fuel into the respective swirl channel. Here, the multiplicity of swirl channels forms, in particular jointly, a swirl generator. The swirl channels each extend from an inflow side, at which fuel from the respective fuel nozzle can be introduced into the respective swirl channel, to an outflow side leading into the combustion space. The combustion space, which can also be referred to as combustion zone, can be surrounded or delimited by a combustion chamber. Further, the combustion space substantially determines merely the volume in which the combustion of a fuel-air mixture or gas-air mixture takes place. The swirl channels can each be flowed through along a flow path extending from the respective inflow side to the respective outflow side by the fuel-air mixture of the fuel and air flowing into the swirl channel.
In such a burner, a swirl channel, multiple swirl channels or all swirl channels can comprise one or multiple fuel nozzles.
The fuel is liquid fuel or gas. The gas is preferentially hydrogen or hydrogen gas.
Further, the burner comprises a centre axis running through the combustion space. According to one aspect of the present invention it is substantial that the swirl channels, emanating from the outflow side, are helically wound about the centre axis at least in portions. Alternatively, the helical formation of the swirl channels at least in portions can be described such that the swirl channels and/or the flow paths defined by the swirl channels are each formed helically or as helix at least in portions. Thus, the swirl channels can also be referred to as curved swirl channels. Emanating from the inflow side, the flow channels or the flow paths defined by these lead, twisted on the outflow side or tilted relative to the centre axis, into the combustion space. This results in that the fuel-air mixture flowing from the inflow side along the flow path to the outflow side is in each case subjected to a swirl by the helically wound portions of the swirl channels and flows into the combustion space in a swirl-subjected manner. Thus, a fuel-air mixture subjected to a swirl flows preferentially through each individual one of the swirl channels.
In the process, a multiplicity of individual or free jets is generated by the swirl channels on the outflow side or in the combustion space, but which have already been subjected to swirl by the swirl or winding about the centre axis.
Thus, by way of their helical winding about the centre axis the swirl chambers already have a curvature which, when the air or the fuel-air mixture flows through the flow channels, imparts a rotation component to the same.
At the outlet of the burner or when the fuel-air mixture flows out of the swirl channels into the combustion space, a combustion pattern that is similar to the swirling-flow burner, in which a swirl materializing from the free jets bursts open and stabilises the flame in the combustion space in the shear layers of the swirl.
Because of the fact that the burner comprises a multiplicity of swirl channels, which in their entirety can also be referred to as swirl generators, the fuel-air mixture is not fed to the combustion space through an individual feedline but through the multiplicity of swirl channels formed for example as tubes, so that the burner according to the invention has a similarly good flash-back strength or a similarly good flash-back resistance as the jet burners known from the prior art, wherein through the swirl application, a low-emission combustion continues to take place.
Since on the inflow side the fuel and preferentially also the air is introduced into the swirl channels, fuel and air mix along the flow paths through the swirl channels to form the desired fuel-air mixture.
By providing a multiplicity of swirl channels forming the swirl generator, which are each formed helically at least in portions, the swirl generator is formed as multiple helix which has a number of turns corresponding to the number of swirl channels. The turns or the swirl channels can be additionally provided in layers or planes overlapping one another, so that for example an inner plane of swirl channels can be surrounded by an outer plane of swirl channels. Here, the swirl channels can either be of the left-hand or right-hand type.
An advantageous aspect provides that the flow paths and/or the centre lines of the swirl channels in the portion of the swirl channels running helically about the centre axis each have a turn angle greater than 0° and smaller than 90°, in particular greater than 600 and smaller than 90°, further in particular exactly 60°.
The turn angle of the swirl channels or of the flow paths and/or centre lines of the swirl channels is defined according to the turn angle of a helix.
Further, all flow paths and/or centre lines preferentially have an identical turn angle.
If the swirl channels are produced by an additive production method such as for example a selective laser melting (SLM), the maximum or minimum pitch or the turn angle can be restricted by the technical limitations of the production method. For example, at least at the time of application, it is not possible to produce swirl channels with a turn angle smaller than 40° by the SLM method or only with major expenditure so.
Further, an advantageous variant of the burner provides that the swirl channels each comprise on the outflow side the portion wound helically about the centre axis and on the inflow side a portion running parallel to the centre axis. Here, the swirl channels each have a transition between the helically wound or curved portion and the portion running parallel to the centre axis, i.e. the straight portion, which is smooth, so that a fuel-air mixture flowing through the swirl channels from the portion that is straight or parallel to the centre axis to the helically wound or curved portion is deflected continuously or steadily and not suddenly along or in the region of the transition.
Further it is preferentially provided that the swirl channels each comprise an annular cross-section and are formed as swirl tubes.
Also advantageous is a variant in which the fuel nozzles each extend into the respective swirl channel on the inflow side.
Here it is advantageously provided further in an embodiment that the swirl chambers on the inflow side each comprise an in particular funnel-shaped inflow portion, into which the respective fuel nozzles extends, wherein between an outer surface of the respective fuel nozzle and an inner surface of the respective swirl channel in its inflow portion an air passage that is preferentially annular in the cross-section is defined, through which air can flow into the respective swirl channel.
In addition, fluid guiding elements designed in particular as wings can be provided in the swirl channels and/or on the fuel nozzles for flow optimisation.
The fluid elements are designed to influence the flow of a fluid flowing passed them in a predefined manner. For example, fluid elements can be provided with an aerofoil profile on the fuel nozzles in the region of the air passage, which steer the air flowing through the air passage in a predefined manner into the fuel injected or introduced by the fuel nozzles, in order to thereby improve the mixing of the air with the fuel.
Preferentially, the swirl channels each extend in a predefined plane or within the inner and outer lateral surface of a hollow cylinder. Accordingly it can be provided that the swirl channels or their centre lines/flow paths are arranged on at least one annular course that is coaxial to the centre axis. Accordingly, multiple courses that are each annular and coaxial to the centre axis can also be provided, wherein multiple flow paths run on each of the courses.
In order to be able to provide as many swirl channels as possible, the swirl channels of the multiplicity of swirl channels lie against one another. Consequently, swirl channels that are directly adjacent to one another lie against one another for example with the outer surfaces of their walls.
In particular when the swirl channels or the swirl generators formed by these are produced by an additive production method it can be provided further that the swirl channels do not merely lie against one another but are partly formed integrally with one another. The swirl channels each have a wall delimiting the respective swirl channel in the radial direction. Here it is then provided that the walls of swirl channels lying against one another or adjacent to one another are formed integrally and/or in one piece.
To improve the mixing of fuel and air it can be provided further that the fuel nozzles are designed to introduce the fuel on the inflow side substantially transversely into the respective swirl channel.
As already mentioned it is preferentially provided that the swirl channels are produced from metal by a selective laser melting (SLM).
A further aspect of the invention relates to a method for producing a burner. Here, the swirl channels are produced by selective laser melting (SLM), i.e. by an additive production method, from a metal powder which for forming the swirl channels or the swirl generators formed by the swirl channels is melted in layers. Here, the swirl channels are produced individually and for providing the swirl generator arranged about the centre axis. Alternatively to this, the swirl channels can also be produced joined in groups integrally and/or in one piece and the groups of swirl channels joined to one another, be arranged about the centre axis for providing the swirl generator. Alternatively to the production of individual swirl channels and alternatively to the production of groups of joined swirl channels, the entire swirl generator, i.e. all swirl channels, can be produced joined integrally and/or in one piece and arranged about the centre axis.
The features disclosed above can be combined as desired insofar as this is technically possible and these do not contradict one another.
Other advantageous further developments of the invention are marked in the subclaims or are presented in more detail by way of the figures together with the description of the preferred embodiment. It shows:
The figures are exemplarily schematic. Same reference numbers in the figures point out same functionally and/or structural features.
In
There, the fuel-air mixture initially flows through a portion 24 (straight portion 24) initially running parallel to the centre axis of the respective swirl channel 2, which by a steady, smooth transition 25 merges into a portion 26 wound helically about the centre axis X, which can also refer to as curved portion 26.
In the process, the fuel-air mixture is imparted a swirl or rotation when flowing through the curved portion 26 so that each fuel-air mixture flow issuing out of a swirl channel 2 into the outflow side combustion space 1 is subjected to a swirl. Here, the fuel-air mixture flow through a single swirl channel 2 merely forms a part flow of the entire fuel-air mixture flow flowing through the swirl channels 2.
In the combustion space 1, the fuel-air mixture flowing in with the entire fuel-air mixture flow is combusted, wherein by subjecting the individual part flow to a swirl the entire flow is subjected to a swirl resulting in a low-emission combustion, wherein through the multiplicity of swirl channels 2 running along the centre axis X a high flash-back resistance is achieved at the same time so that a flame during the combustion does not substantially flash back out of the combustion space 1 into the swirl channels 2.
In
As described before, an air passage 26 each running annularly about the fuel nozzle 3 is formed between the outer surfaces of the fuel nozzles 27 and the inner surfaces of the swirl channels 2 in the region of the inflow portions 27, through which the air L flows into the respective swirl channel 2. There, at least one fluid guiding element 4 each formed in the manner of an aerofoil is provided on the fuel nozzles 3, which extends into the annular air passage 26 and steers the inflowing air L into the associated swirl channel 2 in a flow-optimised manner.
Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 123 513.8 | Sep 2021 | DE | national |
This is a U.S. national stage of Application No. PCT/EP2022/073684 filed Aug. 25, 2022. Priority is claimed on German Application No. DE 10 2021 123 513.8 filed Sep. 10, 2021, the content of which is incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/073684 | 8/25/2022 | WO |
