An air self-purging anti-flashback central nozzle structure

Abstract

The present invention provides an air self-purging anti-backfire center nozzle structure. The structure includes a straight section pipe and a tapered section pipe; the outer diameter of the straight section pipe is a first diameter; a purge hole is provided upstream of the straight section pipe; the tapered section pipe is located at the tail end of the straight section pipe; the tapered section pipe is provided with an oblique radial fuel injection hole and an axial fuel injection hole, wherein the oblique radial fuel injection hole is provided on the pipe wall of the tapered section pipe, and the axial fuel injection hole is provided on the end face of the tapered section pipe; the straight section pipe and the tapered section pipe corresponding to the duty class are coaxially nested with other premixing stages in the combustion chamber head as an integrated structure; the straight section pipe and the tapered section pipe are located in the center of the combustion chamber head and are provided with a fuel cavity therein. The air self-purging anti-backfire center nozzle structure of the present invention can achieve a smooth transition of working conditions and prevent head ablation.

Description

Technical Field

[0001] The invention belongs to the field of gas turbine combustion chambers, and in particular relates to an air self-purge backfire prevention central nozzle structure. Background Art

[0002] Modern low-pollution gas turbines widely use lean premixed combustion technology to control nitrogen oxide emissions, but lean premixed combustion faces problems such as unstable combustion and poor ignition performance. The coaxial staged combustor utilizes a central duty stage and multiple premixed stages coaxially nested together to achieve a smooth transition from low to high operating conditions through coordination between the stages. At low operating conditions, the duty stage primarily utilizes diffusion combustion to increase the likelihood of ignition. However, excessively high equivalence ratios can cause flashback and burn the head during intense combustion. At high operating conditions, completely closing the duty stage also allows the flame to approach the combustor head, causing head ablation.

[0003] In recent years, there have been numerous applications for coaxial staged combustors in China. Patent application number 202110664719.5 discloses a coaxial staged gas fuel combustor head for a low-emission gas turbine. This head utilizes a premixing stage hub with a Venturi tube structure to accelerate airflow, creating a propulsion flame near the combustor head outlet to prevent flashback. However, the sudden increase in airflow velocity can also lead to combustion instability and flame oscillation. Summary of the Invention

[0004] In view of the above problems, the present invention proposes an air self-purge anti-flashback central nozzle structure to solve at least one of the above problems existing in the prior art.

[0005] According to one aspect of the present invention, there is provided an air self-purging anti-backfire central nozzle structure, which is characterized in that it includes a straight section pipe and a tapered section pipe; the outer diameter of the straight section pipe is a first diameter; a purge hole is provided upstream of the straight section pipe; the tapered section pipe is located at the tail end of the straight section pipe; the tapered section pipe is provided with oblique radial fuel injection holes and axial fuel injection holes, wherein the oblique radial fuel injection holes are arranged on the pipe wall of the tapered section pipe, and the axial fuel injection holes are arranged on the end face of the tapered section pipe; the straight section pipe and the tapered section pipe corresponding to the duty class are coaxially nested integrated structures with other premixing stages in the combustion chamber head; the straight section pipe and the tapered section pipe are located in the center of the combustion chamber head and are provided with a fuel cavity inside.

[0006] Furthermore, in the combustion chamber head, the purge hole is arranged 5-10 mm upstream of the first-stage fuel injection hole.

[0007] Furthermore, the oblique radial fuel injection holes are provided on the tube wall of the tapered section pipe, and a plurality of oblique radial fuel injection holes are evenly arranged along the circumferential direction at a predetermined distance from the second end face, with the drilling direction being perpendicular to the conical surface of the tube wall.

[0008] Furthermore, the number of the oblique radial fuel injection holes is 4 to 8, and the hole diameter is 0.6 to 1 mm.

[0009] Furthermore, the axial fuel injection holes are arranged on the end face of the tapered section pipe, with the drilling direction perpendicular to the second end face. The number of the axial fuel injection holes is 4 to 8, and the hole diameter is 0.6 to 1 mm.

[0010] Furthermore, the length of the tapered section of the pipeline is 1 to 2.5 times the outer diameter of the straight section of the pipeline, and the angle γ between the tangent in the axial direction and the central axis is 15° to 35°.

[0011] Furthermore, a corresponding purge pipe is provided outside each purge hole of the straight section pipe.

[0012] Furthermore, the purge holes are arranged before the first stage swirl blades, with a hole diameter of 0.1D to 0.3D, and 3 to 6 purge holes are arranged along the circumferential direction.

[0013] Furthermore, the air self-purge anti-backfire center nozzle structure is also provided with a purge hole baffle; when the duty class is working, the duty class supplies fuel, the purge hole baffle pops out, blocking the purge hole to prevent the center-stage fuel from spraying out of the purge hole; when the duty class is not working, the duty class does not supply fuel, the purge hole baffle does not pop out, and air enters the center duty class pipeline from the purge hole to promote flame and prevent the center duty class from burning.

[0014] The air self-purge anti-backfire central nozzle structure of the present invention can achieve a smooth transition of working conditions and prevent head ablation.

[0015] The present invention adopts a coaxial nested form for each stage, with the duty stage located in the center, which can stabilize combustion and improve ignition performance. The premixing stage fully premixes the fuel, which can achieve graded and zoned combustion and effectively reduce emissions.

[0016] The duty class of the present invention has a purge hole. Under low working conditions, the intake volume of the purge air can be adjusted to prevent the duty class outlet fuel equivalence ratio from being too high and being burned; under high working conditions, the intake volume of the purge air can also be adjusted to achieve the promotion of the flame in the main combustion zone and prevent backfire. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a structural schematic diagram of an example of an air self-purge anti-flashback central nozzle structure according to an embodiment of the present invention;

[0018] Figure 2 yes Figure 1 sectional view of

[0019] Figure 3 yes Figure 1 A schematic diagram of an air self-purge anti-flashback central nozzle structure used in a combustion chamber head is shown;

[0020] Figure 4 This is a structural schematic diagram of another example of an air self-purge anti-flashback central nozzle structure according to an embodiment of the present invention;

[0021] Figure 5 yes Figure 4 The structure diagram of an air self-purge anti-flashback central nozzle structure applied to a sleeve-type fuel inlet pipe is shown;

[0022] Figure 6 yes Figure 4 The schematic diagram of an air self-purge anti-flashback central nozzle structure used in another combustion chamber head is shown;

[0023] Figure 7 This is a schematic diagram of the status of the purge hole baffle during shift work;

[0024] Figure 8 This is a schematic diagram of the status of the purge hole baffle when the shift is not working.

[0025] In the figure: 1a: straight section; 1b: tapered section; 2: purge hole; 2a: purge pipe; 3: oblique radial fuel hole; 4: axial fuel hole; 5: center axis; 6: first-stage swirl blade; 7a: mainstream air; 7b: purge air; 8: duty class fuel; 9: purge hole baffle; D: duty class outer diameter; γ: angle between the tangent line on the axial direction of the tapered section and the center axis. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the present invention, exemplary embodiments or examples of the present invention will be described below with reference to the accompanying drawings. Based on the embodiments of the present invention, all other embodiments or examples obtained by those skilled in the art without creative work should fall within the scope of protection of the present invention.

[0027] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed or detachable connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention.

[0028] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0029] According to an embodiment of the present invention, an air self-purging anti-backfire central nozzle structure is provided, which is characterized in that it includes a straight section pipe and a tapered section pipe; the outer diameter of the straight section pipe is a first diameter; a purge hole is provided upstream of the straight section pipe; the tapered section pipe is located at the tail end of the straight section pipe; the tapered section pipe is provided with oblique radial fuel injection holes and axial fuel injection holes, wherein the oblique radial fuel injection holes are arranged on the pipe wall of the tapered section pipe, and the axial fuel injection holes are arranged on the end face of the tapered section pipe; the straight section pipe and the tapered section pipe corresponding to the duty class are coaxially nested integrated structures with other premixing stages in the combustion chamber head; the straight section pipe and the tapered section pipe are located in the center of the combustion chamber head and are provided with a fuel cavity inside.

[0030] Figure 1 A structural schematic diagram of an example of the above-mentioned air self-purge anti-flashback central nozzle structure is shown. Figure 2 yes Figure 1 sectional view of .

[0031] like Figure 1 As shown, an air self-purging anti-flashback central nozzle structure includes a straight section pipe 1a and a tapered section pipe 1b.

[0032] The tapered section of the pipeline 1b is located at the tail end of the straight section of the pipeline 1a.

[0033] The outer diameter of the straight section pipeline 1a is a first diameter, as shown by D in the figure; the inner diameter of the straight section pipeline 1a is a second diameter.

[0034] The tapered section pipe 1b is a conical section, that is, the cone is cut into two sections by a plane parallel to the bottom surface of the cone, one section contains the vertex and the other does not contain the vertex, and the part without the vertex is the above-mentioned conical section.

[0035] Thus, the tapered pipe section 1b has two end surfaces: a first end surface and a second end surface. The first end surface is an annular end surface with an outer diameter of the third diameter and an inner diameter of the second diameter, which is the same as the inner diameter of the straight pipe section 1a. The outer diameter of the second end surface is the fourth diameter. The third diameter is greater than or equal to the first diameter. The fourth diameter is smaller than the third diameter.

[0036] In one example, if Figure 1 As shown, the third diameter is, for example, equal to the first diameter.

[0037] One end of the straight section pipeline 1a (i.e. the left end shown in the figure) is used to connect the outlet of the class fuel pipeline, such as Figure 2 As shown, the dotted circled portion shows the location of the aforementioned air self-purge anti-backfire central nozzle structure, and the left side is where it is connected to the duty class fuel pipeline.

[0038] The other end of the straight section pipe 1a (i.e. the right end shown in the figure) is connected to the tapered section pipe 1b, wherein the two are coaxially arranged, and the other end of the straight section pipe 1a is connected to the first end face of the tapered section pipe 1b.

[0039] A purge hole 2 is provided upstream of the straight section of pipe 1a. For example, in the combustion chamber head, the purge hole 2 can be placed 5-10 mm upstream of the first-stage fuel injection hole. This prevents the first-stage fuel from entering the center stage (i.e., the duty class) through the purge hole.

[0040] The tapered section pipe 1b is provided with oblique radial fuel injection holes 3 and axial fuel injection holes 4.

[0041] The oblique radial fuel injection holes 3 are provided on the wall of the tapered pipe section 1b. Multiple oblique radial fuel injection holes 3 are evenly spaced circumferentially at a predetermined distance from the second end face, with the holes drilled perpendicular to the conical surface of the pipe wall. The predetermined distance can be set empirically or determined through experimentation. The number of oblique radial fuel injection holes 3 is, for example, 4 to 8, and the hole diameter is, for example, 0.6 to 1 mm.

[0042] The axial fuel injection holes 4 are provided on the second end face of the tapered pipe 1 b , with the drilling direction perpendicular to the second end face. The number of the axial fuel injection holes 4 is, for example, 4 to 8, and the hole diameter is, for example, 0.6 to 1 mm.

[0043] As an example, the length of the tapered section pipe 1b is 1 to 2.5 times the outer diameter D of the straight section pipe 1a, and the angle γ between the tangent in the axial direction and the central axis 5 is 15° to 35°.

[0044] As an example, Figure 3 Shows the Figure 1 The air self-purging anti-flashback central nozzle structure shown is an example structure applied in a combustion chamber head.

[0045] The straight section duct 1a and the tapered section duct 1b correspond to the value class. In an embodiment of the present invention, the value class (i.e., the straight section duct 1a and the tapered section duct 1b) and the other premixing stages (i.e., the premixing stage swirlers) in the combustor head are, for example, coaxially nested, integrated structures located in the center of the combustor head and having a fuel chamber inside.

[0046] Most of the mainstream air 7a enters the premixing stages of each level from the head, and a small amount of purge air 7b enters the duty class through the purge hole 2; when the duty class is closed (the duty class is not working), the duty class does not supply fuel 8. After the purge air 7b enters the duty class through the purge hole 2, it is ejected from the oblique radial fuel injection hole 3 and the axial fuel injection hole 4, forming a push-up flame to avoid head ablation.

[0047] As an example, the duty class is mainly opened at low operating conditions. As the operating conditions gradually improve, each premixing stage is gradually put into operation. At high operating conditions, the duty class is closed and no fuel is supplied.

[0048] Figure 4 A structural schematic diagram showing another example of an air self-purge anti-flashback central nozzle structure.

[0049] like Figure 4 As shown, a corresponding purge pipe 2a is provided outside each purge hole 2 of the straight section pipeline 1a. When the fuel inlet pipe is a central sleeve, that is, the fuel conduit of the duty class is located at the center, multiple levels of fuel pipes (such as the first level, the second level, etc.) are coaxially nested outside the fuel conduit of the duty class. Figure 5 As shown, the fuel inlet pipeline is a three-layer casing, with the duty class, second stage, and first stage arranged from the inside out. Thus, the duty class's air self-purge and backfire-proof central nozzle structure connects to the duty class fuel pipeline and is located at the center of the casing. Without the purge pipe 2a, external purge air 7b would not be able to enter the duty class through the first- and second-stage fuel pipelines. In this embodiment, by providing a purge pipe outside each purge hole 2, the central duty class straight section pipe 1a is directly connected to the external purge air 7b through the purge holes 2 and 2a, preventing air or fuel from entering the second-stage fuel pipeline through the purge hole 2.

[0050] In one example, if Figure 4 As shown, the third diameter is, for example, larger than the first diameter.

[0051] Figure 6 Shows the Figure 4 The air self-purging anti-flashback center nozzle structure shown is an example structure applied in another combustion chamber head.

[0052] As an example, Figure 6As shown, the purge holes 2 are arranged before the first stage swirl blades 6, with a hole diameter of 0.1D to 0.3D, and 3 to 6 holes are arranged along the circumferential direction.

[0053] As an example, the air self-purge anti-backfire central nozzle structure can be provided with a purge hole baffle 9. Figure 7 and Figure 8 As shown, Figure 8 It is the state when the class is not working. Figure 7 It is the state when on duty.

[0054] The purge hole baffle 9 can be, for example, a pressure valve, an elastic switch baffle, or the like, which has a switch structure with two states of open and closed.

[0055] When on duty, Figure 7 As shown, the duty class supplies fuel 8, and the purge hole blocking piece 9 pops out to block the purge hole 2, preventing the center-level fuel (i.e., the duty class fuel) from being ejected from the purge hole 2 and affecting the ignition performance;

[0056] When not working on duty, Figure 8 As shown, the duty class does not supply fuel 8, the purge hole baffle 9 does not pop out, and air enters the central duty class pipeline from the purge hole 2. This air can push the flame (near the central blunt body) to prevent the central duty class from ablation.

[0057] The purge hole baffle 9 can also be set as follows Figure 1 The air self-purge anti-backfire center nozzle structure shown will not be described in detail here.

[0058] Although the present invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of the foregoing description, will appreciate that other embodiments are contemplated within the scope of the invention thus described. This disclosure is intended to be illustrative rather than restrictive of the scope of the invention, which is defined by the appended claims.

Claims

1. An air self-purge anti-flashback central nozzle structure, characterized in that: It includes a straight section pipeline (1a) and a tapered section pipeline (1b); The outer diameter of the straight section pipeline (1a) is a first diameter; a purge hole (2) is provided upstream of the straight section pipeline (1a); The tapered section pipe (1b) is located at the tail end of the straight section pipe (1a); the tapered section pipe (1b) is provided with an oblique radial fuel injection hole (3) and an axial fuel injection hole (4), wherein the oblique radial fuel injection hole (3) is provided on the pipe wall of the tapered section pipe (1b), and the axial fuel injection hole (4) is provided on the end face of the tapered section pipe (1b); The straight section pipe (1a) and the tapered section pipe (1b) corresponding to the duty class are coaxially nested with other premixing stages in the combustion chamber head to form an integrated structure; the straight section pipe (1a) and the tapered section pipe (1b) are located in the center of the combustion chamber head and are provided with a fuel cavity therein; The air self-purge anti-backfire central nozzle structure is further provided with a purge hole baffle (9); When the duty shift is working, the duty shift supplies fuel (8), and the purge hole blocking piece (9) pops out to block the purge hole (2) to prevent the center stage fuel from being ejected from the purge hole (2); When the duty class is not working, the duty class does not supply fuel (8), the purge hole baffle (9) does not pop out, and air enters the central duty class pipeline through the purge hole (2) to push the flame to prevent the central duty class from burning; The inner diameter of the straight section pipe (1a) is the second diameter; the tapered section pipe (1b) has two end faces, one being the first end face and the other being the second end face, the first end face being a circular end face, the outer diameter of which is the third diameter; the inner diameter is the second diameter, which is the same as the inner diameter of the straight section pipe (1a), the outer diameter of the second end face is the fourth diameter, the third diameter is greater than or equal to the first diameter, and the fourth diameter is smaller than the third diameter; When the third diameter is equal to the first diameter, one end of the straight section pipe (1a) is used to connect to the outlet of the duty class fuel pipe; the other end of the straight section pipe (1a) is connected to the tapered section pipe (1b), wherein the two are coaxially arranged, and the other end of the straight section pipe (1a) is connected to the first end face of the tapered section pipe (1b); the straight section pipe (1a) and the tapered section pipe (1b) correspond to the duty class, most of the mainstream air (7a) enters each premixing stage from the head, and a small amount of purge air (7b) enters the duty class from the purge hole (2); when the duty class is closed, the duty class does not supply fuel (8), and the purge air (7b) enters the duty class through the purge hole (2) and is then ejected from the oblique radial fuel injection hole (3) and the axial fuel injection hole (4), forming a push-up flame to avoid head ablation; When the third diameter is greater than the first diameter; When the duty shift is working, the duty shift supplies fuel (8), and the purge hole blocking piece (9) pops out to block the purge hole (2), thereby preventing the center-stage fuel from being ejected from the purge hole (2) and affecting the ignition performance; When the duty class is not working, the duty class does not supply fuel (8), the purge hole baffle (9) does not pop out, and air enters the central duty class pipeline from the purge hole (2). This air can play a role in pushing the flame to prevent the central duty class from burning.

2. The air self-purge anti-flashback central nozzle structure according to claim 1 is characterized in that: In the combustion chamber head, the purge hole (2) is arranged 5-10 mm upstream of the first-stage fuel injection hole.

3. The air self-purge anti-flashback central nozzle structure according to claim 1 or 2, characterized in that: The oblique radial fuel injection holes (3) are arranged on the tube wall of the tapered section pipe (1b), and a plurality of oblique radial fuel injection holes (3) are evenly arranged along the circumference at a predetermined distance from the second end face, with the punching direction being perpendicular to the conical surface of the tube wall.

4. The air self-purge anti-flashback central nozzle structure according to claim 1 or 2, characterized in that: The number of the oblique radial fuel injection holes (3) is 4 to 8, and the hole diameter is 0.6 to 1 mm.

5. The air self-purge anti-flashback central nozzle structure according to claim 1 or 2, characterized in that: The axial fuel injection holes (4) are arranged on the end face of the tapered section pipe (1b), with the punching direction perpendicular to the second end face. The number of the axial fuel injection holes (4) is 4 to 8, and the hole diameter is 0.6 to 1 mm.

6. The air self-purge anti-flashback central nozzle structure according to claim 1 or 2, characterized in that: The length of the tapered section pipe (1b) is 1 to 2.5 times the outer diameter of the straight section pipe (1a), and the angle γ between the tangent in the axial direction and the central axis (5) is 15° to 35°.

7. The air self-purge anti-flashback central nozzle structure according to claim 1 or 2, characterized in that: A corresponding purge pipe (2a) is provided outside each purge hole (2) of the straight section pipe (1a).

8. The air self-purge anti-flashback central nozzle structure according to claim 1 or 2, characterized in that: The purge holes (2) are arranged before the first-stage swirl blades (6), have an aperture of 0.1D to 0.3D, and are 3 to 6 in number arranged circumferentially.

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