Axial composite nozzle structure

Abstract

An axial composite nozzle structure belongs to the field of nozzle technology. It includes a nozzle body, which is provided with a fuel inlet cavity, an air inlet cavity, and a first fuel channel, a first air channel, a second fuel channel, and a second air channel coaxially arranged from the inside out. Fuel flows into the first fuel channel and the second fuel channel respectively through the fuel inlet cavity; air flows into the first air channel and the second air channel respectively through the air inlet cavity. The present invention realizes different combustion modes by redistributing the fuel and air entering the nozzle, which can achieve better overall performance under different combustion conditions. Compared with existing structural solutions, it can simultaneously take into account ignition performance in small states and pollution emission performance in large states, improving the integrated design of the nozzle and reducing the difficulty of nozzle layout.

Description

Technical Field

[0001] The invention belongs to the technical field of nozzles, and in particular relates to an axial composite nozzle structure. Background Art

[0002] During the startup process of an aircraft engine or ground-based gas turbine, the engine is typically driven by a starter motor. Once it reaches a certain speed, fuel is introduced into the burner for ignition and combustion. The fuel flow is then continuously increased to achieve higher speeds and higher loads. After reaching 50% load, emissions performance (NOx and CO) and combustion stability become key performance targets. Therefore, burner or nozzle design prioritizes ignition performance at low speeds, emissions performance at high speeds, and combustion stability under all operating conditions. However, current burner or nozzle designs typically employ a radially staged design, with diffuser nozzles positioned at the center of the burner axis to improve ignition performance at low speeds and premixed nozzles positioned outboard to reduce emissions at high speeds. In principle, this approach achieves both excellent ignition performance at low speeds and excellent emissions performance at high speeds. However, in practice, the central diffuser nozzle must maintain combustion from ignition until full load, which impacts high-speed emissions. Furthermore, the premixed design of the outer nozzles increases the risk of flashback and thermoacoustic oscillation. Furthermore, for smaller gas turbines or burners, radial nozzle grading increases system complexity and burner diameter, restricting lightweight burner development. Therefore, a more rational nozzle design is needed to simultaneously meet both low-power ignition performance and high-power emission performance. Summary of the Invention

[0003] In view of the above problems existing in the prior art, the object of the present invention is to provide an axial composite nozzle structure.

[0004] The present invention provides the following technical solution: an axial composite nozzle structure, comprising a nozzle body; the nozzle body is provided with a fuel inlet cavity, an air inlet cavity, and a first fuel channel, a first air channel, a second fuel channel, and a second air channel coaxially arranged from the inside to the outside along the central axis of the nozzle body; fuel flows into the first fuel channel and the second fuel channel respectively through the fuel inlet cavity; air flows into the first air channel and the second air channel respectively through the air inlet cavity;

[0005] A set of axial swirl blades is provided in the first air channel, and a premixing section is provided downstream of the axial swirl blades. The first fuel channel is a channel of uniform cross-section, which is connected to the first air channel. The fuel flowing into the first air channel through the first fuel channel is mixed with the swirl air flowing through the axial swirl blades in the first air channel. After passing through the premixing section, a swirl premixed gas is formed, and a recirculation zone is formed downstream of the nozzle. After the swirl premixed gas is ignited, a premixed swirl combustion mode is formed, which not only improves the ignition success rate but also effectively reduces NOx emissions.

[0006] The second air passage is communicated with the second fuel passage. Air flowing through the second air passage is mixed with fuel flowing into the second air passage through the second fuel passage and then flows out.

[0007] Furthermore, a fuel distribution cavity is provided in the nozzle body, and the fuel passes through the fuel inlet cavity and is distributed to the first fuel channel and the second fuel channel via the fuel distribution cavity; the cross-sectional area of ​​the fuel distribution cavity is larger than the cross-sectional area of ​​the fuel inlet cavity.

[0008] Furthermore, the air inlet cavity is connected to the first air channel through a group of circumferentially arranged air distribution holes.

[0009] Furthermore, a group of axial swirl blades in the first air channel are arranged at even intervals in the circumferential direction, and the blades are tilted, with an inclination angle of 30 to 60 degrees.

[0010] Furthermore, a group of first fuel injection channels are opened on the first fuel channel, and the first fuel injection channels are arranged corresponding to the axial swirl blades and extend to the interior of the axial swirl blades. A group of first fuel injection holes connected to the first fuel injection channels are opened on the axial swirl blades at the first fuel injection channels.

[0011] Furthermore, a group of second fuel channels are arranged away from the central axis of the fuel distribution cavity and are evenly spaced circumferentially along the central axis of the first fuel channel, so that the fuel is evenly distributed among the group of second fuel channels.

[0012] Furthermore, a second fuel injection hole is provided at the end of the second fuel channel, and the second fuel channel is connected to the second air channel through the second fuel injection hole; the air flowing in the second air channel is mixed with the fuel injected through the second fuel injection hole and then flows out; and at the mixing point, the flow direction of the air is perpendicular to the flow direction of the fuel.

[0013] Furthermore, an air plate is provided at the bottom of the second air channel, and an air door hole is provided on the air plate; the number of the air distribution holes is the same as the number of the air door holes, and the air distribution hole is located between the two air door holes; the second fuel injection holes are arranged in a one-to-one correspondence with the air door holes.

[0014] By adopting the above technology, compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] 1) The present invention achieves different combustion modes by redistributing the fuel and air entering the nozzle, achieving better overall performance under different combustion conditions. Compared with existing structural solutions, it can simultaneously take into account both ignition performance under low-pressure conditions and pollution emission performance under high-pressure conditions, thereby improving the integrated design of the nozzle and reducing the difficulty of nozzle layout.

[0016] 2) In the present invention, the second fuel channel is disposed away from the central axis of the fuel distribution chamber, so that the flow velocity there is further reduced compared to the central axis of the fuel distribution chamber, which is conducive to uniform distribution of fuel among the multiple second fuel channels;

[0017] 3) In the present invention, the fuel sprayed from the first fuel injection hole is directly mixed with the swirling air flowing through the axial swirl blades, and a premixed swirl premixed gas is formed after passing through the premixing section, which can form a larger recirculation zone downstream of the nozzle, effectively reducing the premixed gas speed and improving the ignition success rate; and combined with the control of the total equivalent ratio of fuel and air, the ignition success rate can be further improved; by setting the premixed swirl combustion mode, NOx emissions can be effectively reduced.

[0018] 4) In the present invention, the fuel passing through the second fuel channel and the air flowing from the second air channel through the space doorway are mixed with each other, and the flow directions of the two are perpendicular to each other, which enhances the mixing between the fuel and the air and forms a micro-mixing effect; after ignition, multiple independently dispersed small flames can be formed, forming a micro-mixing combustion mode, with a single flame length shorter and a weaker flame intensity, which can greatly reduce NOx emissions, and because the fuel and air are located in different channels, the occurrence of backfire can be avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the internal structure of the present invention;

[0020] Figure 2 This is a schematic structural diagram of the second fuel injection hole of the second fuel channel machine of the present invention;

[0021] Figure 3 for Figure 1 AA cross-sectional structural diagram;

[0022] Figure 4 for Figure 1 Schematic diagram of the cross-sectional structure of the middle BB;

[0023] Figure 5 This is a schematic diagram of the internal structure of the present invention in the swirl combustion mode;

[0024] Figure 6 Schematic diagram of the internal structure of the present invention in the mild mixing combustion mode.

[0025] In the figure: 10-fuel inlet chamber; 11-nozzle assembly hole; 20-fuel distribution chamber; 30-first fuel channel; 31-first fuel inlet hole; 32-first fuel injection channel; 33-first fuel injection hole; 34-first fuel base plate; 40-second fuel channel; 41-second fuel injection hole; 50-air inlet chamber; 51-nozzle mounting surface; 52-air distribution chamber; 60-first air channel; 61-axial swirl blade; 70-second air channel; 71-air door hole; 72-air plate. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0027] On the contrary, the present invention covers any alternatives, modifications, equivalents, and solutions that fall within the spirit and scope of the present invention as defined by the claims. Furthermore, to facilitate a better understanding of the present invention, certain specific details are described in detail below in the detailed description of the present invention. Those skilled in the art will be able to fully understand the present invention without these details.

[0028] See also Figure 1-6 An axial composite nozzle structure includes a nozzle body and a four-layer channel structure coaxially arranged from the inside out along the central axis of the nozzle body. The four-layer channel structure includes a first fuel channel 30, a first air channel 60, a second fuel channel 40, and a second air channel 70, arranged sequentially from the inside out. The first fuel channel 30 and the second fuel channel 40 are formed by entering the same fuel inlet cavity 10 and passing through the fuel distribution cavity 20. The first air channel 60 and the second air channel 70 are formed by entering the same air inlet cavity and being directly distributed.

[0029] The fuel (which can be natural gas, hydrogen, ammonia or synthesis gas, etc.) enters the fuel distribution chamber 20 from the fuel inlet chamber 10. The diameter (area) of the fuel distribution chamber is larger than the diameter (area) of the fuel inlet chamber, so the fuel flow rate is reduced, which is more conducive to reducing pressure loss and distributing fuel. A portion of the fuel (about 10%) enters the first fuel channel 30 through the first fuel inlet hole 31 located at the central axis of the nozzle body, and the remaining 90% of the fuel enters a plurality of circumferentially evenly arranged second fuel channels 40 through the outer side away from the center line. The number of second fuel channels corresponds one-to-one to the number of air port holes 71 in the second air channel, and the number is usually 6 to 20. The second fuel channel 40 is set at a position away from the center line because the flow rate here is further reduced compared to the center line position, which is conducive to the uniform distribution of fuel among the multiple second fuel channels 40.

[0030] Air enters from the air inlet chamber 50, and a portion (about 5%) turns from the air distribution chamber 52 to flow into the first air channel 60. Multiple air distribution chambers 52 are evenly distributed along the circumference of the first air channel 60, and the number is consistent with the air door holes 71. The position of the air distribution chamber 52 is between two adjacent air door holes 71, and it will hardly affect the flow field distribution in the air door hole 71.

[0031] Axial swirl blades 61 are installed within the first air passage 60. The blade angle is 30 to 60 degrees, and the number of blades ranges from 4 to 10, depending on the size of the first air passage. The vast majority of the air (approximately 95%) flows along the main flow to the second air passage 70 and out through air ports 71 evenly distributed around the circumference.

[0032] The first fuel channel 30 is equipped with multiple first fuel injection channels 32, the same number as the axial swirl vanes 61. These channels extend through the interior of the axial swirl vanes 61, with the angles and directions of the channels aligned with those of the axial swirl vanes. Multiple first fuel injection holes 33 are located on one side of the first fuel injection channels 32. Fuel ejected from the first fuel injection holes 33 directly mixes with the swirling air flowing through the axial swirl vanes 61, forming a swirling premixed gas. The distance L between the first fuel injection holes 33 and the first fuel base plate 34 allows for premixing of the fuel premixed gas within this distance. The premixing distance L ranges from 4 to 10 mm and can be designed based on the actual axial length of the nozzle and the desired premixing effect. The swirling premixed gas forms a large recirculation zone downstream of the nozzle, effectively reducing flame speed and improving ignition success rate. Furthermore, since the fuel passing through the first fuel injection channels 32 accounts for approximately 10% of the total fuel volume, and the air passing through the first air channel 60 accounts for 5% of the total air volume, the local equivalence ratio of the swirling premixed gas is twice the nozzle's overall equivalence ratio, significantly improving ignition success rate. In addition, due to the setting of the premixing section L, the fuel and air can be mixed as evenly as possible, avoiding excessive local fuel concentration distribution and effectively reducing the NOx level.

[0033] A second fuel injection hole 41 is provided at the end of the second fuel passage 40. The second portion of fuel flowing from the second fuel injection hole 41 mixes with the second portion of air flowing from the second air passage 70 and through the spatial doorway 71. Because the fuel velocity and the air velocity are perpendicular to each other, the mixing between the fuel and air is enhanced, creating a micro-mixing effect. After the internally measured swirl flame ignites, multiple independently dispersed small flames form downstream of the second fuel injection hole 41, forming a micro-mixing combustion mode. Individual flames are shorter and weaker, significantly reducing NOx emissions. Furthermore, because the fuel and air are located in separate passages, flashback is avoided.

[0034] Specifically, the distribution design of fuel and air flow is as follows:

[0035] The ratio of the flow rates flowing into the first fuel passage 30 and the second fuel passage 40 through the fuel inlet cavity is calculated based on the effective areas of the first fuel injection hole 33 and the second fuel injection hole 41 .

[0036] m1=m t *(A1*Cd1) / (A1*Cd1+A2*Cd2)

[0037] m1 is the flow rate flowing into the first fuel channel 30, m t is the total flow rate from the fuel inlet; A1 is the total area of ​​the first fuel injection hole 33, A2 is the total area of ​​the second fuel injection hole 41; Cd1 is the flow coefficient of the first fuel injection hole 33; Cd2 is the flow coefficient of the second fuel injection hole 41. The ratio of the fuel passing through the first fuel channel 30 and the second fuel channel 40 is:

[0038] m1 / m2=A1Cd1 / A2Cd2

[0039] During the design process, the ratio of fuel flowing into the first fuel channel 30 and the second fuel channel 40 is usually designed first, and then the areas of the first fuel injection hole 33 and the second fuel injection hole 41 are designed based on this ratio.

[0040] Specifically, the ratio of air flowing through the air inlet cavity 50 into the first air channel 60 and the second air channel 70 is also determined according to the effective areas of the air distribution cavity 52 and the air door hole 71 .

[0041] The entire nozzle structure can be installed in multiple locations within the burner, such as the centerline of the burner head, near the outer wall of the burner head, or axially arranged on the burner's flame tube, primarily relying on the nozzle mounting surface 51 for positioning. A fuel pipeline is connected upstream of the nozzle and is screwed into the nozzle assembly hole 11 provided on the nozzle body.

[0042] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An axial composite nozzle structure, comprising a nozzle body; characterized in that: The nozzle body is provided with a fuel inlet cavity (10), an air inlet cavity (50), and a first fuel channel (30), a first air channel (60), a second fuel channel (40), and a second air channel (70) coaxially arranged in sequence along the central axis of the nozzle body from the inside to the outside; the fuel flows into the first fuel channel (30) and the second fuel channel (40) respectively through the fuel inlet cavity (10); Air flows into the first air channel (60) and the second air channel (70) respectively through the air inlet cavity (50); A group of axial swirl blades (61) are provided in the first air channel (60), a premixing section is provided downstream of the axial swirl blades, the first fuel channel (30) is a channel of equal cross-section, and is communicated with the first air channel (60). The fuel flowing into the first air channel (60) through the first fuel channel (30) is mixed with the swirl air flowing through the axial swirl blades (61) in the first air channel (60), and a swirl premixed gas is formed after passing through the premixing section, and a recirculation zone is formed downstream of the nozzle. After the swirl premixed gas is ignited, a premixed swirl combustion mode is formed. The second air channel (70) is in communication with the second fuel channel (40), and the air flowing through the second air channel (70) is mixed with the fuel flowing into the second air channel (70) through the second fuel channel (40) and then flows out; A fuel distribution cavity (20) is provided in the nozzle body, and fuel passes through the fuel inlet cavity (10) and is distributed to the first fuel channel (30) and the second fuel channel (40) via the fuel distribution cavity (20); the cross-sectional area of ​​the fuel distribution cavity (20) is larger than the cross-sectional area of ​​the fuel inlet cavity (10); The air inlet cavity (50) is connected to the first air channel (60) through a group of circumferentially arranged air distribution holes (52); A second fuel injection hole (41) is provided at the end of the second fuel channel (40), and the second fuel channel (40) is connected to the second air channel (70) through the second fuel injection hole (41); the air flowing in the second air channel (70) is mixed with the fuel injected through the second fuel injection hole (41) and then flows out; and at the mixing point, the flow direction of the air is perpendicular to the flow direction of the fuel; An air plate (72) is provided at the bottom of the second air channel (70), and an air door hole (71) is provided on the air plate (72); the number of the air distribution holes (52) is the same as the number of the air door holes (71), and the air distribution hole (52) is located between the two air door holes (71); and the second fuel injection hole (41) is provided in a one-to-one correspondence with the air door holes (71).

2. The axial composite nozzle structure according to claim 1, characterized in that: A group of axial swirl blades (61) in the first air channel (60) are arranged at even intervals in the circumferential direction, and the blades are tilted, with an inclination angle of 30 to 60 degrees.

3. The axial composite nozzle structure according to claim 2, characterized in that: A group of first fuel injection channels (32) is provided on the first fuel channel (30), the first fuel injection channels (32) are arranged corresponding to the axial swirl blades (61) and extend into the interior of the axial swirl blades (61), and a group of first fuel injection holes (33) communicating with the first fuel injection channels (32) is provided on the axial swirl blades (61) at the first fuel injection channels (32).

4. The axial composite nozzle structure according to claim 1, characterized in that: A group of second fuel channels (40) is arranged away from the central axis of the fuel distribution cavity (20) and is evenly spaced circumferentially along the central axis of the first fuel channel (30) to facilitate even distribution of fuel among the group of second fuel channels (40).

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