A centrally staged low-emission combustor head with a highly efficient backfire prevention structure

Abstract

This invention discloses a centrally staged low-emission combustor head with a highly efficient backfire prevention structure, belonging to the technical field of low-emission combustor heads. It includes a pre-combustion stage component, a main combustion stage component, and a backfire prevention structure located between them. The pre-combustion stage component injects its internal fuel through a centrifugal nozzle, forming a solid cone-shaped atomization field. The main combustion stage component injects its internal fuel into the main combustion stage annular channel through a transverse fuel direct injection orifice, forming an annular atomization field that mixes with air in the first-stage radial cyclone separator of the main combustion stage to form a combustible premixed fuel-air mixture. The backfire prevention structure provides a backfire prevention air wall within the annular channel of the main combustion stage. The outlet of the backfire prevention air wall is located on the inner wall of the main combustion stage, and the angle between the outlet of the annular channel and the inner wall of the main combustion stage forms an acute angle, used to prevent the main combustion stage flame from extending upstream into the premixed fuel-air mixture. This invention effectively prevents backfire, thereby preventing safety hazards caused by backfire.

Description

Technical Field

[0001] This invention belongs to the technical field of low-emission combustion chamber head, specifically relating to a centrally staged low-emission combustion chamber head with a highly efficient backfire prevention structure. Background Technology

[0002] Against the backdrop of increasing global environmental awareness, the performance optimization and pollutant emission control of aero-engines have become a focus of common concern in the scientific research community. As one of the core components of an aero-engine, the design and performance of the combustor directly determine the engine's overall efficiency, economy, and environmental performance. In recent years, the central staged combustor has been widely used and researched in the field of aero-engines due to its efficient combustion organization, low pollutant emissions, and good stability.

[0003] The centrally staged swirl combustor is designed to improve combustion efficiency, reduce pollutant formation, and enhance combustion stability by optimizing the fuel-air mixing process and the layout of the combustion zones. Its unique aerodynamic structure helps suppress the formation of localized high-temperature zones, reduces thermal NOx formation, and promotes soot oxidation, thus lowering pollutant emissions. However, the centrally staged combustor suffers from severe backfire problems due to the premixed section of the main combustion stage.

[0004] In summary, in order to reduce pollutant emissions while effectively preventing backfire, this invention designs a centrally staged low-emission combustion chamber head with a highly efficient backfire prevention structure. Summary of the Invention

[0005] The technical problem to be solved:

[0006] To overcome the shortcomings of existing technologies, this invention provides a centrally staged low-emission combustion chamber head with a highly efficient backfire prevention structure. An annular channel is provided between the pre-combustion stage components and the main combustion stage components. Air from this annular channel is introduced into the main combustion stage channel through jet orifices, forming a high-speed flowing "air wall" that prevents the main combustion stage flame from extending upstream into the premixed fuel-air mixture, effectively preventing backfire and thus mitigating safety hazards caused by backfire. Simultaneously, this invention employs a centrally staged combustion organization method, maintaining stable combustion and widening the ignition point boundary under low operating conditions; and reducing pollutant emissions, especially NOx emissions, under high operating conditions. This invention solves the backfire problem inherent in centrally staged combustion organization technology while reducing pollutant emissions, ensuring both reduced pollutant generation and prevention of backfire.

[0007] The technical solution of this invention is: a centrally staged low-emission combustion chamber head with a highly efficient backfire prevention structure, characterized in that: it includes a pre-combustion stage component, a main combustion stage component, and a backfire prevention structure located between them, arranged sequentially from the inside to the outside; the pre-combustion stage component injects its internal fuel through a pre-combustion stage centrifugal nozzle to form a solid cone-shaped atomization field; the main combustion stage component injects its internal fuel into the main combustion stage annular channel through a main combustion stage transverse fuel direct injection hole to form an annular atomization field, which mixes with the air in the first-stage radial cyclone of the main combustion stage to form a combustible premixed fuel gas; the backfire prevention structure provides a backfire prevention air wall into the main combustion stage annular channel, the outlet of the backfire prevention air wall is located on the inner wall surface of the main combustion stage, and the angle between the outlet of the main combustion stage annular channel and the inner wall of the main combustion stage forms an acute angle, so as to prevent the main combustion stage flame from extending upstream into the premixed fuel gas.

[0008] A further technical solution of the present invention is as follows: the pre-combustion stage component includes a pre-combustion stage centrifugal nozzle, a pre-combustion stage dual-stage axial cyclone separator, a venturi tube, and a pre-combustion stage fuel supply pipe. The pre-combustion stage dual-stage axial cyclone separator is disposed on the outer periphery of the pre-combustion stage centrifugal nozzle to introduce reverse swirling air. The outer wall of the first-stage cyclone separator of the pre-combustion stage dual-stage axial cyclone separator extends downstream of the pre-combustion stage centrifugal nozzle, and the extended portion is a venturi tube. The input end of the pre-combustion stage fuel supply pipe is connected to the centrifugal nozzle to introduce fuel. The flow rate range of the pre-combustion stage centrifugal nozzle is 1 to 15 g / s, the spray type is a solid cone, a hollow cone, or a semi-solid cone, and the spray angle is 45°, 60°, or 80°.

[0009] A further technical solution of the present invention is: the pre-combustion stage dual-stage axial cyclone separator adopts axial flow straight blades, the two stages of blades rotate in opposite directions, and the number of blades is 12; the swirl angles of the inner and outer blades are 30° and 45° respectively; the ratio of the air flow of the inner and outer stages of the cyclone separator is 0.43 to 1.5.

[0010] A further technical solution of the present invention is: the angle of the converging section of the Venturi tube is the same as the cone angle of the centrifugal nozzle head, and the angle with the axis is 22.5°, while the angle with the axis of the expanding section is 11.5°.

[0011] A further technical solution of the present invention is as follows: the main combustion stage component is an annular structure, and a main combustion stage fuel delivery channel and a main combustion stage annular channel are provided inside its annular wall. The input end of the main combustion stage fuel delivery channel is provided with a main combustion stage fuel collecting ring, which is connected to the main combustion stage fuel supply pipe. The inlet of the main combustion stage annular channel is connected to the first-stage radial cyclone separator of the main combustion stage, and swirling air is introduced radially through the first-stage radial cyclone separator of the main combustion stage. Its outlet is located on the downstream end face, on the same side as the pre-combustion stage centrifugal nozzle. The main combustion stage fuel delivery channel and the main combustion stage annular channel are connected through a main combustion stage transverse fuel direct injection hole, so that the fuel in the main combustion stage fuel delivery channel is injected into the main combustion stage annular channel.

[0012] A further technical solution of the present invention is as follows: the angle between the transverse fuel direct injection orifice of the main combustion stage and the axial direction is 75° to 120°, the orifice diameter is 0.2 to 0.4 mm, the orifice length-to-diameter ratio is 2.5 to 5, and the number of orifices is 8 to 16; the swirl angle of the first-stage radial cyclone of the main combustion stage is 30° to 45°, the number of blades is 30, and the blade height is 12 mm.

[0013] A further technical solution of the present invention is: the main combustion stage oil collecting ring is an annular flow channel inside the front end of the main combustion stage, with a ring height of 6mm and a ring width of 2mm. The oil collecting ring has 8 to 16 deep holes with a diameter of 1mm inside, which are connected to the transverse fuel direct injection holes of the main combustion stage to supply fuel to it.

[0014] A further technical solution of the present invention is: the backfire prevention structure includes an interstage channel disposed between the pre-combustion stage component and the main combustion stage component, a main combustion stage transverse air jet hole connecting the interstage channel and the main combustion stage annular channel, and a head cooling hole leading from the interstage channel to the downstream end face; the outlet of the main combustion stage transverse air jet hole is located on the inner wall of the main combustion stage annular channel, with an axial angle of 45° with the head of the central stage low emission combustion chamber, a diameter of 1.9 mm, and two rows of oblique holes arranged in a cross pattern, totaling 80 holes.

[0015] A further technical solution of the present invention is: the interstage channel is an air channel between the pre-combustion stage and the main combustion stage, and the channel ring height is 5mm.

[0016] A further technical solution of the present invention is: the head cooling holes are located on the interstage steps between the pre-combustion stage and the main combustion stage, and are distributed in four concentric rings, with 20 micro-holes of 0.5 mm in diameter in each ring.

[0017] Beneficial effects

[0018] The beneficial effects of this invention are as follows: This invention proposes a centrally staged low-emission combustor head with a highly efficient backfire prevention structure. This head mainly consists of a pre-combustion stage component, a main combustion stage component, interstage channels, and head cooling holes. The pre-combustion stage component is located at the center of the head and consists of a centrifugal nozzle, a two-stage axial swirler, a venturi tube, and a pre-combustion stage fuel supply pipe. The blades of the two-stage axial swirler rotate in opposite directions, forming a central recirculation zone with a strong shear layer downstream, which helps to break up and atomize the fuel film and stabilize the flame. Under low operating conditions, the pre-combustion stage operates independently, stabilizing combustion in a diffuse flame form. Simultaneously, the locally rich fuel state greatly widens the flame stability working boundary. The main combustion stage component is arranged concentrically around the pre-combustion stage component and mainly includes a lateral fuel direct injection orifice, a first-stage radial swirler, a lateral air jet orifice, a fuel supply pipe, and a fuel collecting ring. The main combustion stage components activate under heavy operating conditions, working in conjunction with the pre-combustion stage components to regulate the temperature distribution of the flow field within the combustion chamber. Furthermore, the fuel-air distribution between the main and pre-combustion stages can be adjusted according to different operating conditions to achieve optimal combustion and emission performance. Multiple lateral fuel injection orifices in the main combustion stage atomize the fuel injection, and the resulting annular swirling flow formed by the first-stage radial swirler rapidly mixes the fuel within the premixing channel, creating a uniform combustible mixture. A 45° lateral air jet orifice is located on the inner wall of the main combustion stage, downstream of the fuel injection orifice. This design provides a near-identical velocity distribution in both the radial and axial directions. The radial velocity component effectively prevents direct contact between upstream fuel flowing near the inner wall and downstream high-temperature combustion gases, avoiding the extension of the high-temperature flame into the premixing channel and thus preventing backfire. Simultaneously, the axial velocity component increases the axial velocity of the mainstream airflow, shortening the dwell time and significantly reducing NOx emissions. Specific advantages are as follows:

[0019] (1) Enhanced ignition and stability. The diameter of the pre-combustion stage nozzle is 0.2 to 0.6 mm. The smaller nozzle diameter allows the fuel to be fully atomized under high oil pressure, making it easier to ignite and resulting in stronger flame stability.

[0020] (2) Lower pollutant emissions. The main combustion stage has 16 transverse fuel direct injection holes with a diameter of 0.2-0.4 mm, which are evenly arranged, resulting in better fuel penetration depth and atomization effect, and more uniform fuel-air mixing in the premixing section. Multiple transverse air jet holes with a 45° jet angle are set on the inner wall of the main combustion stage. The axial velocity they provide can increase the axial velocity of the mainstream air and shorten the stagnation time, which can significantly reduce NOx emissions.

[0021] (3) Highly efficient backfire prevention. The 45° jet angle provides a radial velocity equal to the axial velocity. This radial velocity, while ensuring that it does not significantly affect the mainstream axial velocity, can prevent the fuel flowing near the inner wall upstream from directly contacting the high-temperature gas downstream, thus preventing the high-temperature flame from extending into the premixed channel and causing backfire.

[0022] (4) Wider stable operating boundary of the combustion chamber. The central staged combustion technology is adopted. The pre-combustion stage works alone under small operating conditions to form a stable diffusion flame; the main combustion stage works simultaneously with the pre-combustion stage under large operating conditions. Through oil-gas matching, staged and zoned combustion is achieved, resulting in more stable combustion.

[0023] (5) The head structure is flexible and adaptable. Multiple components of the combustion chamber head are assembled by means of extrusion and threaded fastening. The components can be disassembled and replaced. The main combustion stage blade installation angle, the number of fuel direct injection holes, the position of fuel direct injection holes, and the atomization angle of the pre-combustion stage centrifugal nozzle can all be changed according to research needs, which has a wide range of research applications.

[0024] It has been verified that Figure 7 The results of temperature field simulations are shown for the initial model (a) and the optimized existing model (b). It can be seen that the 45° air jet hole structure designed on the inner wall of the main combustion stage effectively eliminates the backfire phenomenon. Figure 8 The results of NO concentration field simulations are presented for the initial model (a) and the optimized existing model (b). It can be seen that the 45° air jet orifice structure designed on the inner wall of the main combustion stage effectively reduces NO generation. The 45° air jet orifice angle design balances backfire prevention and low NOx emissions. Attached Figure Description

[0025] Figure 1 This is a cross-sectional view of the central staged low-emission combustion chamber head with a highly efficient backfire prevention structure according to the present invention.

[0026] Figure 2 This is a cross-sectional view of the pre-combustion stage component of the centrally staged low-emission combustion chamber head with a highly efficient backfire prevention structure according to the present invention.

[0027] Figure 3 This is one of the partial structural schematic diagrams of the pre-combustion stage component of the central staged low-emission combustion chamber head with a high-efficiency backfire prevention structure of the present invention;

[0028] Figure 4 This is a cross-sectional view of the main combustion stage component of the centrally staged low-emission combustion chamber head with a highly efficient backfire prevention structure according to the present invention.

[0029] Figure 5 This is one of the partial structural schematic diagrams of the main combustion stage component of the centrally staged low-emission combustion chamber head with a highly efficient backfire prevention structure according to the present invention.

[0030] Figure 6 The images show a front view (a), a left view (b), and an orthometric view (c) of the central staged low-emission combustion chamber head structure with a high-efficiency backfire prevention structure of the present invention.

[0031] Figure 7The results of the initial model (a) and the optimized existing model (b) in the temperature field simulation in the embodiments of the present invention are shown.

[0032] Figure 8 The results are shown in the NO concentration field simulation of the initial model (a) and the optimized existing model (b) in the embodiments of the present invention.

[0033] Explanation of reference numerals in the attached diagram: 1. Pre-combustion stage component; 2. Main combustion stage component; 3. Interstage channel; 4. Head cooling hole; 11. Pre-combustion stage centrifugal nozzle; 12. Pre-combustion stage two-stage axial swirler; 13. Venturi tube; 14. Pre-combustion stage fuel supply pipe; 21. Main combustion stage lateral fuel direct injection orifice; 22. Main combustion stage first-stage radial swirler; 23. Main combustion stage lateral air jet orifice; 24. Main combustion stage fuel supply pipe; 25. Main combustion stage fuel collecting ring; 26. Main combustion stage fuel delivery passage. Detailed Implementation

[0034] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0035] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0036] While existing central staged combustion technology reduces pollutant emissions, it also introduces the problem of backfire. This invention provides a central staged low-emission combustor head with a highly efficient backfire prevention structure. The head includes a pre-combustion stage component, a main combustion stage component, and a backfire prevention structure located between them, arranged sequentially from the inside out. The pre-combustion stage component injects its internal fuel through a centrifugal nozzle, forming a solid cone-shaped atomization field. The main combustion stage component injects its internal fuel into the main combustion stage annular channel through a transverse fuel direct injection orifice, forming an annular atomization field that mixes with air in the first-stage radial cyclone separator of the main combustion stage to form a combustible premixed fuel-air mixture. The backfire prevention structure provides a backfire prevention air wall within the main combustion stage annular channel. The outlet of the backfire prevention air wall is located on the inner wall of the main combustion stage, and the angle between the outlet of the annular channel and the inner wall of the main combustion stage forms an acute angle, preventing the main combustion stage flame from extending upstream into the premixed fuel-air mixture.

[0037] Specifically, the pre-combustion stage components include a pre-combustion stage centrifugal nozzle, a pre-combustion stage dual-stage axial cyclone separator, a venturi tube, and a pre-combustion stage fuel supply pipe. The pre-combustion stage dual-stage axial cyclone separator is disposed on the outer periphery of the pre-combustion stage centrifugal nozzle to introduce reverse swirling air. The outer wall of the first-stage cyclone separator of the pre-combustion stage dual-stage axial cyclone separator extends downstream of the pre-combustion stage centrifugal nozzle, and the extended portion is a venturi tube. The input end of the pre-combustion stage fuel supply pipe is connected to the centrifugal nozzle to introduce fuel.

[0038] Specifically, the main combustion stage component has an annular structure, with a main combustion stage fuel delivery channel and a main combustion stage annular channel arranged within its annular wall. The input end of the main combustion stage fuel delivery channel is equipped with a main combustion stage fuel collecting ring, which is connected to the main combustion stage fuel supply pipe. The inlet of the main combustion stage annular channel is connected to the first-stage radial cyclone separator of the main combustion stage, through which swirling air is introduced radially. Its outlet is located on the downstream end face, on the same side as the pre-combustion stage centrifugal nozzle. The main combustion stage fuel delivery channel and the main combustion stage annular channel are connected by a main combustion stage transverse fuel direct injection hole, through which fuel in the main combustion stage fuel delivery channel is injected into the main combustion stage annular channel.

[0039] Specifically, the backfire prevention structure includes an interstage channel disposed between the pre-combustion stage component and the main combustion stage component, a main combustion stage transverse air jet hole connecting the interstage channel and the main combustion stage annular channel, and a head cooling hole leading from the interstage channel to the downstream end face; the outlet of the main combustion stage transverse air jet hole is located on the inner wall of the main combustion stage annular channel.

[0040] The key features of this invention are: firstly, the central staged combustion organization technology greatly improves flame stability under low operating conditions and significantly reduces pollutant emissions under high operating conditions; secondly, a transverse air jet hole structure is designed at the outlet of the main combustion stage premixing section, forming an "air wall" that isolates the premixed gas from the flame, effectively preventing backfire and thus preventing safety hazards caused by backfire.

[0041] The above technical solution will be further explained below with reference to the accompanying drawings and embodiments:

[0042] Reference Figures 1-6 As shown, the centrally staged low-emission combustor head with a highly efficient backfire prevention structure in this embodiment includes a pre-combustion stage component 1, a main combustion stage component 2, an interstage channel 3, and a head cooling hole 4. This head employs centrally staged low-emission technology and a backfire prevention structure design, and is entirely made of high-temperature alloy steel GH3536, assembled using welding and threaded fastening methods.

[0043] The pre-combustion stage component 1 is located at the center of the head and consists of a pre-combustion stage centrifugal nozzle 11, a pre-combustion stage dual-stage axial cyclone separator 12, a venturi tube 13, and a pre-combustion stage oil supply pipe 14. Among them, the pre-combustion stage dual-stage axial cyclone separator 12 and the venturi tube 13 are integrally formed using 3D printing technology; the pre-combustion stage oil supply pipe 14 and the pre-combustion stage centrifugal nozzle 11 are machined and connected together by welding, and the end faces are pressed and sealed in the central channel of the cyclone separator by threaded fastening, with the downstream end face of the nozzle flush with the downstream end face of the central channel of the cyclone separator.

[0044] The blades of the pre-combustion stage dual-stage axial cyclone separator 12 rotate in opposite directions, forming a central recirculation zone with a strong shear layer downstream, which helps to break up and atomize the oil film and stabilize the flame. Under low operating conditions, the pre-combustion stage works alone, stabilizing combustion in the form of a diffuse flame. At the same time, the locally rich oil state also greatly widens the flame stability working boundary.

[0045] The main combustion stage component 2 is arranged in a concentric circle, surrounding the pre-combustion stage component. It mainly includes a main combustion stage lateral fuel direct injection orifice 21, a main combustion stage first-stage radial swirler 22, a main combustion stage lateral air jet orifice 23, a main combustion stage fuel supply pipe 24, and a main combustion stage fuel collecting ring 25. The main combustion stage component 2 is machined. The pre-combustion stage component 1 is concentrically placed inside the main combustion stage. The downstream outer end face of the pre-combustion stage is pressed against the downstream inner end face of the main combustion stage, forming an interstage channel 3 and an interstage step. Head cooling holes 4 are machined on the interstage step. The inner and outer rings of the main combustion stage are connected by long bolts through threaded holes on the front end face and are integrally fixed to the combustion chamber head baffle with a pressure plate.

[0046] The main combustion stage component 2 activates under heavy operating conditions, working in conjunction with the pre-combustion stage component 1 to regulate the temperature distribution of the flow field within the combustion chamber. It can also adjust the fuel-air distribution between the main and pre-combustion stages according to different operating conditions to achieve optimal combustion and emission performance. Multiple lateral fuel injection holes 21 in the main combustion stage atomize the fuel injection, and the resulting annular swirling flow formed by the first-stage radial swirler 22 rapidly mixes the fuel within the premixing channel, forming a uniform combustible mixture. Lateral air jet holes 23 in the main combustion stage form an "air wall" upstream of the main combustion stage outlet, effectively blocking direct contact between the flame and the combustible mixture and increasing the axial jet velocity of the mixture, effectively preventing backfire. Furthermore, the lateral jet shortens the gas stagnation time, further reducing emissions of pollutants such as NOx.

[0047] Reference Figure 1As shown, the air flowing through the combustion chamber head structure is divided into three streams: main combustion stage swirling air, pre-combustion stage swirling air, and interstage channel air. The first stream is introduced through the pre-combustion stage dual-stage axial swirler 12. This stream further breaks up and atomizes the fuel injected by the pre-combustion stage centrifugal nozzle 11 in a reverse swirling manner, while forming a central recirculation zone in the downstream region of the combustion chamber head, thereby stabilizing the flame combustion. The second stream enters the premixing channel of the swirler through the main combustion stage first-stage radial swirler 22, forming an annular swirling flow. This swirling flow rapidly mixes with the fuel injected by the main combustion stage lateral fuel direct injection orifice 21, forming a uniform premixed fuel-air mixture. As for the third stream, it is mainly injected into the main combustion stage channel in large quantities through the main combustion stage lateral air jet orifice 23. This stream constructs two layers of air barriers upstream of the channel outlet, like an "air wall," effectively preventing backfire. In addition, the addition of lateral jet air also reduces the swirling intensity of the main combustion stage air and the premixed gas stagnation time, thereby significantly reducing NOx generation. The remaining small portion of air flows into the combustion chamber through the head cooling holes 4 on the interstage steps, ensuring that the steps are protected from erosion by the high-temperature flames through an efficient porous heat exchange cooling method.

[0048] Reference Figure 2 As shown, the pre-combustion stage dual-stage axial cyclone separator 12 is integrally formed using 3D printing technology. It employs axial flow straight blades, with the two stages having blades rotating in opposite directions, and each stage containing 12 blades. The swirl angles of the inner and outer blades are 30° and 45°, respectively. The ring heights of the inner and outer stages are 4.55 mm and 3.25 mm, respectively, and the ring heights are geometrically adjustable. The airflow ratio between the two stages is 1. It should be noted that the upper half of the middle channel of the cyclone separator has a diameter of 15.2 mm, and the lower half has a diameter of 13.2 mm, forming a 1 mm wide step, which is used to form an end-face compression seal with the boss of the pre-combustion stage centrifugal nozzle 11.

[0049] Reference Figure 3 As shown, the pre-combustion stage oil supply pipe 14 and the pre-combustion stage centrifugal nozzle 11 are machined and connected by welding. The inner diameter of the oil supply pipe is 2 mm and the outer diameter is 4 mm. The outer diameter of the pre-combustion stage centrifugal nozzle 11 is 13 mm, and the nozzle orifice diameter is 0.4 mm. The pre-combustion stage centrifugal nozzle 11 has a boss in the middle with a height of 1 mm and a width of 4 mm. When assembled with the pre-combustion stage hydrocyclone, this boss is pressed tightly against the stepped end face of the pre-combustion stage central channel for a seal.

[0050] Reference Figure 4As shown, the main combustion stage component 2 has a lateral fuel direct injection orifice 21 with an axial angle of 90°, an orifice diameter of 0.2 mm, an aspect ratio of 5, and 16 orifices. The first-stage radial swirler 22 of the main combustion stage has a swirl angle of 35°, 30 blades, and a blade height of 12 mm. The main combustion stage lateral air jet orifice 23 has an axial angle of 45°, a diameter of 1.9 mm, and consists of two rows of oblique orifices arranged in a staggered pattern, totaling 80 orifices. The main combustion stage premixing channel is tapered, with a contraction angle of approximately 5° and a channel length of 17 mm.

[0051] Reference Figure 5 As shown, the oil collecting ring of the main combustion stage component is an annular flow channel inside the front end of the main combustion stage. The ring height is 6mm and the ring width is 2mm. There are 16 deep holes with a diameter of 1mm inside the oil collecting ring, which are connected to the transverse fuel direct injection holes of the main combustion stage, serving as the main combustion stage oil delivery channel 26.

[0052] Reference Figure 6 As shown, the maximum outer diameter of the combustion chamber head structure is 102 mm, and the axial length is 38.5 mm. In Figure (b), the head end face is provided with multiple threaded holes for assembling various head components. Combined with the threads on the outer ring wall of the main combustion stage in Figure (c), the entire head can be fixed to the combustion chamber front baffle.

[0053] Reference Figure 7 As shown, (a) and (b) are the temperature field calculation results of the old model before the optimized design of this invention and the low-emission combustor head model with the efficient anti-backfire structure of this invention, respectively. It can be seen that the general low-emission combustor head is prone to spontaneous combustion and backfire due to the presence of premixed gas in its premixed channel, which causes great erosion of the head structure and seriously affects the safety and reliability of the combustor. The optimized design of the head in Figure (a) and the setting of 80 45° air jet holes downstream of the fuel injection holes on the inner wall of the main combustion stage can provide a similar velocity distribution in the radial and axial directions. Among them, the radial velocity component can effectively block the direct contact between the fuel flowing near the inner wall upstream and the high-temperature gas downstream, preventing the high-temperature flame from extending into the premixed channel, thereby preventing backfire. At the same time, the design of the axial velocity component increases the axial velocity of the mainstream airflow and shortens the stagnation time, thereby significantly reducing NOx emissions. The 45° angle design of the air jet holes takes into account both the functions of anti-backfire and low NOx emissions.

[0054] Reference Figure 8 As shown, the results of the initial model (a) and the optimized existing model (b) in the NO concentration field simulation are presented. It can be seen that the 45° air jet orifice structure designed on the inner wall of the main combustion stage effectively reduces NO generation. The 45° air jet orifice angle design can simultaneously achieve the functions of preventing backfire and reducing NOx emissions.

[0055] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A centrally staged low-emission combustion chamber head with a highly efficient backfire prevention structure, characterized in that: The system includes a pre-combustion stage component, a main combustion stage component, and a backfire prevention structure arranged sequentially from the inside out. The pre-combustion stage component injects its internal fuel through a pre-combustion stage centrifugal nozzle, forming a solid cone-shaped atomization field. The main combustion stage component injects its internal fuel into the main combustion stage annular channel through a main combustion stage transverse fuel direct injection hole, forming an annular atomization field, which mixes with the air in the first-stage radial cyclone separator of the main combustion stage to form a combustible premixed fuel gas. The backfire prevention structure provides a backfire prevention air wall into the main combustion stage annular channel. The outlet of the backfire prevention air wall is located on the inner wall of the main combustion stage, and the angle between the outlet of the main combustion stage annular channel and the inner wall of the main combustion stage forms an acute angle, which is used to prevent the flame of the main combustion stage from extending upstream into the premixed fuel gas. The backfire prevention structure includes an interstage channel between the pre-combustion stage component and the main combustion stage component, a main combustion stage transverse air jet hole connecting the interstage channel and the main combustion stage annular channel, and a head cooling hole leading from the interstage channel to the downstream end face; the outlet of the main combustion stage transverse air jet hole is located on the inner wall of the main combustion stage annular channel, with an axial angle of 45° with the head of the central stage low emission combustion chamber, a diameter of 1.9 mm, and two rows of oblique holes arranged in a cross pattern, totaling 80 holes.

2. The centrally staged low-emission combustion chamber head with a highly efficient backfire prevention structure according to claim 1, characterized in that: The pre-combustion stage components include a pre-combustion stage centrifugal nozzle, a pre-combustion stage dual-stage axial cyclone separator, a venturi tube, and a pre-combustion stage fuel supply pipe. The pre-combustion stage dual-stage axial cyclone separator is disposed on the outer periphery of the pre-combustion stage centrifugal nozzle to introduce reverse swirling air. The outer wall of the first-stage cyclone separator extends downstream of the pre-combustion stage centrifugal nozzle, and the extended portion is a venturi tube. The inlet end of the pre-combustion stage fuel supply pipe is connected to the centrifugal nozzle to introduce fuel. The flow rate range of the pre-combustion stage centrifugal nozzle is 1–15 g / s, the spray type is a solid cone, hollow cone, or semi-solid cone, and the spray angle is 45°, 60°, or 80°.

3. The centrally staged low-emission combustion chamber head with a highly efficient backfire prevention structure according to claim 2, characterized in that: The pre-combustion stage dual-stage axial cyclone separator adopts axial flow straight blades, with the two stages of blades rotating in opposite directions, and each stage has 12 blades; the swirl angles of the inner and outer blades are 30° and 45°, respectively; the ratio of the air flow of the inner and outer stages of the cyclone separator is 0.43 to 1.

5.

4. The centrally staged low-emission combustion chamber head with a highly efficient backfire prevention structure according to claim 2, characterized in that: The converging section of the venturi tube has the same angle as the cone angle of the centrifugal nozzle head, with an angle of 22.5° to the axis, while the expanding section has an angle of 11.5° to the axis.

5. The centrally staged low-emission combustion chamber head with a highly efficient backfire prevention structure according to claim 1, characterized in that: The main combustion stage component has an annular structure, with a main combustion stage fuel delivery channel and a main combustion stage annular channel arranged inside its annular wall. The input end of the main combustion stage fuel delivery channel is equipped with a main combustion stage fuel collecting ring, which is connected to the main combustion stage fuel supply pipe. The inlet of the main combustion stage annular channel is connected to the first-stage radial cyclone separator of the main combustion stage, through which swirling air is introduced radially. Its outlet is located on the downstream end face, on the same side as the pre-combustion stage centrifugal nozzle. The main combustion stage fuel delivery channel and the main combustion stage annular channel are connected by a main combustion stage transverse fuel direct injection hole, which injects fuel from the main combustion stage fuel delivery channel into the main combustion stage annular channel.

6. The centrally staged low-emission combustion chamber head with a highly efficient backfire prevention structure according to claim 5, characterized in that: The lateral fuel injection orifice of the main combustion stage has an angle of 75° to 120° with the axial direction, an orifice diameter of 0.2 to 0.4 mm, an orifice length-to-diameter ratio of 2.5 to 5, and 8 to 16 orifices; the swirl angle of the first-stage radial cyclone of the main combustion stage is 30° to 45°, the number of blades is 30, and the blade height is 12 mm.

7. The centrally staged low-emission combustion chamber head with a highly efficient backfire prevention structure according to claim 6, characterized in that: The main combustion stage oil collecting ring is an annular flow channel inside the front end of the main combustion stage. The ring is 6mm high and 2mm wide. The oil collecting ring has 8 to 16 deep holes with a diameter of 1mm inside, which are connected to the transverse fuel direct injection holes of the main combustion stage to supply fuel to it.

8. The centrally staged low-emission combustion chamber head with a highly efficient backfire prevention structure according to claim 7, characterized in that: The interstage channel is the air passage between the pre-combustion stage and the main combustion stage, and the channel ring height is 5mm.

9. The centrally staged low-emission combustion chamber head with a highly efficient backfire prevention structure according to claim 8, characterized in that: The head cooling holes are located on the interstage steps between the pre-combustion stage and the main combustion stage, and are distributed in four concentric rings, with 20 micro-holes with a diameter of 0.5 mm in each ring.

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