Fuel nozzle and combustion device

Abstract

The invention relates to a fuel nozzle (11) for use in a combustion device (01) of a gas turbine. The fuel nozzle (11) comprises a main body (12) extending from a cold side (08) to an opposite hot side (09) and at least five air passages (14) arranged next to each other extending from the cold side (08) towards the hot side (09). A fuel distribution chamber (15) is arranged within the main body (12) close to the cold side (08), wherein the air passages (14) pass through the fuel distribution chamber (15) separated by passage walls (17). For injecting fuel into the air passages (14), fuel holes (18) are arranged within the passage walls (17).

Description

TECHNICAL FIELD

[0001] The present invention generally relates to a fuel nozzle intended for use at a combustion device of a gas turbine as a second (or more downstream) stage fuel injector downstream of a primary burner. Thereby, the fuel nozzle is able to introduce fuel and air into a secondary combustion zone. BACKGROUND

[0002] A combustion device of a gas turbine comprises a combustion chamber, wherein at a head end of the combustion chamber at least one primary burner is arranged. This defines a primary combustion zone within the combustion chamber adjacent to the burner. In customary implementations, a transition is arranged downstream of the combustion chamber, which guides the combustion gases from the combustion chamber to an expansion turbine.

[0003] To minimize the overall generation of NOx emissions, common implementations of combustion devices comprise a further secondary combustion zone downstream of the primary combustion zone. This is achieved by arranging a second stage fuel nozzle within the transition. Examples of such fuel nozzles are presented in EP 3479025 B1, EP 3472518 B1 and EP 3436746 B1. All these types of fuel nozzles have one central air passage. Air is guided from the outside of the transition through the fuel nozzle into the transition. A fuel distributor is usually attached at the cold side of the fuel nozzle, which injects fuel into the air passage.

[0004] To optimize the function of the fuel nozzle, different shapes are known for introducing a mixture of air and fuel into the transition. To increase the depth of the air and fuel flow into the transition and to cool the fuel nozzle, solutions with a double wall arrangement are also used.

[0005] It is further known from the prior art, for example from US 2020 / 0378604 A1, to use a fuel nozzle with a closure plate at the side facing away from the combustion chamber, which has a plurality of mixing passages. With this solution, the mixing of the fuel within the air can be improved.

[0006] Even though it seems that there is hardly any possibility for improvement, there is still a need to further reduce the formation of NOx emissions. SUMMARY

[0007] This task is solved by the inventive implementation of a fuel nozzle and a combustion device according to the invention.

[0008] It is intended to use the universal fuel nozzle in a combustion device. First of all, it does not matter which combustion device and for which purpose the combustion device is used.

[0009] However, the implementation of the fuel nozzle is particularly useful in a combustion device of a gas turbine. Here, the gas turbine usually comprises a compressor, a combustion device and an expansion turbine.

[0010] The generic combustion device comprises at least one combustion chamber, wherein at least one main burner is arranged at a head end of the combustion chamber. This defines a main combustion zone within the combustion chamber adjacent to the main burner. An advantageous embodiment of the combustion device utilizes at least one fuel nozzle as a second stage fuel injector arranged downstream of the main combustion zone. Thereby, the fuel nozzle enables a second stage combustion with a secondary combustion zone.

[0011] It is further advantageous in the device that the combustion device further comprises a transition arranged downstream of the combustion chamber. Herein, at least one fuel nozzle is arranged within the transition. Preferably, several fuel nozzles are arranged in a circumferential distribution.

[0012] The fuel nozzle comprises a main body extending from a cold side to an opposite hot side. The hot side is located at the combustion device towards the combustion zone inside the combustion device. The opposite cold side is facing away from the combustion zone and is located outside the combustion device.

[0013] In order to enable a flow of air and fuel through the fuel nozzle, the generic fuel nozzle comprises air passages. Instead of a single air passage, this solution utilizes a bundle of air passages arranged next to each other and enabling a flow of air from the cold side to the hot side. Herein, at least five air passages need to be realized. It is advantageous that the fuel nozzle comprises at least ten air passages arranged next to each other.

[0014] In order to be able to introduce fuel into the air passages, at least one fuel distribution chamber is required. Therefore, the air passages pass through the fuel distribution chamber, thereby defining a passage wall separating the air passages from the fuel distribution chamber. Preferably, each of the air passages has a passage wall surrounding it. But it is also possible that the air passages pass through the fuel distribution chamber only partially, in particular at the outside, and that the passage wall (with respect to the respective air passage) extends only partially in the circumferential direction. By arranging fuel holes into the passage wall, it is possible to inject fuel into the air passages.

[0015] First, it is not required to arrange fuel holes into every passage wall. But at least half of the existing air passages need to comprise at least one fuel hole inside the passage wall. Advantageously, a fuel hole is arranged inside every passage wall.

[0016] With a bundle of air passages, the mixing of fuel within the air is improved. This leads further to an improved combustion within the combustion device. Therefore, a reduced NOx emission can be further realized compared to a combustion device using the generic fuel nozzle.

[0017] At the cold-side facing end of the air passages some distance between the air passages is required, at least to enable the fuel to flow in the fuel distribution chamber. At the opposite hot-side of the respective air passages it is advantageous that the distance between the separated air passages is reduced to enable a combined flow of air through the air passages without adverse recirculation between the air passages at the hot-side. To adapt the arrangement of the ends of the air passages at the cold-side to the arrangement of the hot-side facing ends of the air passages it is advantageous that the individual air passages travel along a curved or inclined curve towards the central axis of the fuel nozzle on their way from the cold-side towards the hot-side.

[0018] Here it can be sufficient if the curved / inclined route is only given over a part of the length of the respective air passage, in particular at the hot-side.

[0019] Next it is obvious that the central axis is already within the air passages in the centre of the fuel nozzle and thus preferably a straight route. The air passages at a greater distance from the central axis at the cold-side need to be curved / inclined more than those air passages closer to the central axis.

[0020] The central axis extends from the cold-side to the hot-side in the middle of the fuel nozzle and / or in the middle of the bundle of air passages.

[0021] To enable a combined flow of air and fuel without any swirl between the individual flows from the individual air passages and to reduce the size of the fuel nozzle it is advantageous that the air passages are shaped and arranged such that the ends of the air passages face the hot-side according to a honeycomb-like pattern. It is not required that the hot-side facing ends of each individual air passage are exactly shaped as a regular hexagon. Relevant is the following arrangement of air passages: Where the ends of the air passages are in a pattern close to each other and the remaining space between adjacent air passages is minimal.

[0022] A further improvement of the mixing of air and fuel can be achieved by an advantageous arrangement of turbulators within the air passages.

[0023] Firstly, where the turbulators are positioned and how the turbulators are shaped is irrelevant. The aim is to create micro-turbulence inside the air passages. A preferred design has a triangular shape with a tip at the hot-side facing end of the turbulator extending into the air passage.

[0024] Next it is not required to have at least one turbulator in each of the air passages in the air passage. However, it is advantageously that those air passages which comprise a fuel hole inside the respective passage wall should be equipped with a turbulator. Preferably, each of the air passages comprises one turbulator.

[0025] The end of the air passage facing the hot side is advantageously shaped as a honeycomb pattern and the air passage is arranged with some more space at the cold side, for example by a circular shape, due to the fact that it is more advantageous to arrange the turbulator close to the cold side. Here, it is more preferred to arrange the turbulator on the passage wall.

[0026] In order to benefit in the best way from the function of the turbulator, it is also advantageous to arrange the fuel hole at the side facing the hot side with respect to the respective turbulator.

[0027] Next, it is preferred that the turbulator and the fuel hole are positioned at the same circumferential position within / at the respective air passage.

[0028] It is more advantageous to arrange the fuel hole close to the respective turbulator. Here, the distance from the turbulator to the fuel hole should not extend to the height of the respective turbulator. This height is defined as the dimension of the turbulator extending from the passage wall into the air passage. It is particularly advantageous that the distance between the turbulator and the respective fuel hole is less than 0.5 times the height of the turbulator.

[0029] In order to enable the combined flow of mixed air and fuel from a bundle of air passages to enter the combustion zone without vortices between the individual flows, it is preferred that the fuel nozzle further comprises an air chamber arranged within the main body. The flow from the individual air passages should pass through the air chamber into the combustion zone. Thus, the air chamber is arranged behind the end of the air passage facing the hot side. Next, the air chamber opens to the hot side. This solution is more beneficial due to the fact that the cross section of the air chamber can be chosen to be equal to the sum of the cross sections of the individual air passages. Without the separating wall as given at the individual air passages, the total dimension crossing the central axis can be reduced to a minimum need.

[0030] Due to the high level of curved routing of the air passages, and the preferred arrangement of the air chamber between the air passages and the hot side, all air passages can terminate at one common plane. But it is preferred that the surrounding walls of the individual air passages each terminate almost at the plane crossing the routing of the respective air passage.

[0031] In order to be able to cool the fuel nozzle at the hot side, it is advantageous to arrange an annular air channel within the main body surrounding the air chamber. Here, a gap from the air channel into the air chamber is necessary, which should be arranged close to the hot side. The flow of cooling air through the air channel is able to cool the boundary wall surrounding the air chamber at the hot side.

[0032] To increase the penetration of the stream of mixed air and fuel into the combustion zone, advantageously the air passage has in cross section a shape which is inclined relative to the central axis of the fuel nozzle as a bundle of air passages respectively points towards the hot side. This leads to a speed of the annular stream of cooling air which is similar to the speed of the stream of mixed air and fuel from the air passages through the air chamber.

[0033] To enable air to flow through the air passage, advantageously at least one air inlet is arranged at the outer side of the body which is connected with the air passage. Preferably several air inlets are arranged at the outer side of the body which are connected with the air passage.

[0034] To be able to supply fuel to the fuel distribution chamber, advantageously the fuel nozzle comprises a fuel connection arranged at the side of the body facing the cold side.

[0035] The inventive fuel nozzle enables an inventive combustion device. The generic combustion device comprises a combustion chamber, wherein at least one burner is arranged at the upstream end of the combustion chamber. This defines a main combustion zone within the combustion chamber at the outlet of the burner. To enable an efficient combustion, and thereby limit the production of NOx, at least one fuel nozzle is arranged downstream of the main combustion zone. The fuel nozzle enables a secondary combustion zone. This inventive solution makes use of the inventive fuel nozzle.

[0036] Depending on the size and the use of the combustion device, in particular at a gas turbine, advantageously a transition is arranged downstream of the combustion chamber to further guide the hot combustion gases downstream of the combustion chamber. Here, the fuel nozzle is preferably positioned at the transition.

[0037] To enable a homogeneous combustion, the combustion device preferably comprises at least four fuel nozzles which are distributed in a circumferential direction at the combustion chamber or at the transition. BRIEF DESCRIPTION OF DRAWINGS

[0038] The following drawings show an exemplary combustion device and an example for the inventive fuel nozzle.

[0039] Figure 1 An example of a combustion device comprising the inventive fuel nozzle is schematically represented.

[0040] Figure 2 A longitudinal cross section through the exemplary fuel nozzle is shown.

[0041] Figure 3 An isometric view at the fuel nozzle is shown.

[0042] Figure 4 A transversal cross section through the fuel nozzle is shown. DETAILED DESCRIPTION

[0043] An exemplary embodiment of the inventive combustion device 01 is shown in Figure 1 The combustion device comprises a combustion chamber 03, wherein at the upstream end of the combustion chamber 03 a burner 02 is arranged. In operation, this creates a primary combustion zone within the combustion chamber 03 next to the burner 02. Downstream of the combustion chamber 03 a transition 04 is arranged to guide the hot combustion gases.

[0044] Within the transition 04 a plurality of fuel nozzles 11 is arranged, which enable a further combustion of fuel in a secondary combustion zone within the transition.

[0045] An exemplary embodiment of the inventive fuel nozzle 11 is shown in Figure 2 The upper side in use at the combustion device is the cold side 08, which faces away from the secondary combustion zone at the fuel nozzle 11. The lower side in the figure is oriented towards the secondary combustion zone and is therefore the hot side 09.

[0046] The fuel nozzle 11 comprises a main body 12, which has a bundle of air passages 14 extending from the cold side 08 towards the hot side 09. In this embodiment, it is intended that the air passages 14 open into an air chamber 13, which is arranged in the main body 12 between the air passages 14 and the hot side 09. In order to achieve one joint flow from the fuel nozzle 11 into the transition 04, the individual air passages 14 have a curved course from the cold side 08 up to the air chamber 13, wherein the central air passages 14 travel straight along the centre line of the fuel nozzle 11, wherein those air passages which are further away from the centre line are curved more towards the centre.

[0047] In order to be able to minimize the distance between the air passages 14, the shape of the cross section of each of the air passages 14 changes from the cold side 08 towards the hot side 09. At the cold side, the air passages 14 have a circular cross section. This can be seen best in Figure 3 However, at the end of the air chamber 13, the air passages 14 have a hexagonal cross section and are therefore arranged similar to a honeycomb (not shown here).

[0048] The arrangement of a fuel distribution chamber 15 within the main body 12 close to the cold side 08 is also shown in Figure 2 The air passages 14 pass through the fuel distribution chamber 15 and are therefore each separated from the fuel distribution chamber 15 by a respective passage wall 17. This can also be seen best in Figure 4

[0049] In order to be able to supply fuel to the fuel distribution chamber 15, a fuel pipe 21 is attached to the main body 12.

[0050] ​To inject fuel into the air flow in the air passages 14, a fuel hole 18 is arranged in each passage wall 17. Between the different air passages 14, the position of these fuel holes 18 in the circumferential direction relative to the respective air passage 14 is different, in order to avoid the same flow to pass through all air passages 14.

[0051] Next, in this embodiment, upstream of each fuel hole 18, a turbulence generator 19 is arranged at the passage wall 17 extending into the respective air passage 14. Thereby the mixing of the fuel in the air is enhanced.

[0052] To increase the penetration depth of the air-fuel flow from the fuel nozzle 11 into the transition 04, and also to achieve some cooling effect at the hot side 09 of the fuel nozzle 11, in this embodiment an annular air channel 16 is arranged around the air chamber 13. This air channel 16 opens into the air chamber 13 through a gap close to the hot side 09. By the cross shape of the air channel 16, an air flow is achieved that shields the air-fuel flow from the air passages 14. To supply cooling / shielding air to the air channel 16, several air inlets 22 are arranged at the outer side of the body 12.

Claims

1. A fuel nozzle (11) for use in a combustion device (01), the fuel nozzle (11) comprising: The main body (12) extends from the cold side (08) to the opposite hot side (09). At least five air passages (14) are arranged adjacent to each other and extend from the cold side (08) toward the hot side (09). Fuel distribution chamber (15), the fuel distribution chamber (15) being adjacent to the cold side (08), and An air chamber (13) is arranged within the main body (12) to lead to the hot side (09); The air passage (14) passes through the fuel distribution chamber (15) separated by the passage wall (17). Fuel holes (18) are arranged inside the passage wall (17). Its features are, From the cold side (08) toward the hot side (09), the air passage (14) is bent and / or tilted toward the central axis of the fuel nozzle (11) at least in a portion. An annular air passage (16) surrounds the air chamber (13), and the air passage (16) has a gap that is arranged close to the hot side (09) to enter the air chamber (13).

2. The fuel nozzle (11) according to claim 1. in, The fuel nozzle (11) is used in the combustion device (01) of the gas turbine.

3. The fuel nozzle (11) according to claim 1. in, The fuel nozzle (11) includes at least ten of the air passages (14).

4. The fuel nozzle (11) according to any one of claims 1 to 3. in, The end of the air passage (14) facing the hot side (09) is shaped and arranged in a honeycomb pattern (20).

5. The fuel nozzle (11) according to any one of claims 1 to 3. in, A turbulence generator (19) is arranged in the air passage (14).

6. The fuel nozzle (11) according to claim 5. in, The turbulence generator (19) is arranged on the passage wall (17); and / or Wherein, the fuel orifice (18) is arranged on the side facing the hot side relative to the turbulence generator (19); and / or The fuel orifice (18) and the corresponding turbulence generator (19) in the corresponding air passage (14) are arranged at the same circumferential position.

7. The fuel nozzle (11) according to claim 5. in, The distance from the turbulence generator (19) to the corresponding fuel orifice (18) is less than the height of the turbulence generator (19) extending into the air passage (14).

8. The fuel nozzle (11) according to claim 7. in, The distance from the turbulence generator (19) to the corresponding fuel orifice (18) is less than 0.5 times the height of the turbulence generator (19) extending into the air passage (14).

9. The fuel nozzle (11) according to any one of claims 1 to 3, 6 to 8. in, Each passage wall (17) has a fuel port (18) and / or a turbulence generator (19) is arranged in each air passage (14).

10. The fuel nozzle (11) according to any one of claims 1 to 3, 6 to 8. in, The air passage (16) is inclined relative to the central axis of the fuel nozzle (11) and points towards the hot side (09).

11. The fuel nozzle (11) according to any one of claims 1 to 3, 6 to 8. in, At least one air inlet (22) is arranged on the outer side of the main body (12), and the at least one air inlet (22) is connected to the air passage (16).

12. The fuel nozzle (11) according to any one of claims 1 to 3, 6 to 8. in, At least one fuel connection (21) is arranged at the main body (12), and the at least one fuel connection (21) is connected to the fuel distribution chamber (15).

13. A combustion device (01), the combustion device (01) comprising: A burner (02) and a combustion chamber (03), wherein a main combustion zone is located in the combustion chamber (03) adjacent to the burner (02); and at least one fuel nozzle (11) according to any one of claims 1 to 9, the fuel nozzle (11) being arranged downstream of the main combustion zone.

14. The combustion device (01) according to claim 13. in, The combustion device (01) is the combustion device of a gas turbine.

15. The combustion device (01) according to claim 13 or 14. It also includes a transition section (04) arranged downstream of the combustion chamber (03), wherein, The fuel nozzle (11) is arranged inside the transition section (04).

16. The combustion device (01) according to claim 13 or 14. in, There are at least four fuel nozzles distributed circumferentially (11).

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