A hot-jet igniter for a reheat combustor

Abstract

The present application relates to the technical fields of gas turbine afterburner, and particularly relates to a kind of afterburner hot jet ignition device.The present application solves the problems of the integrated afterburner, such as difficult ignition, slow flame propagation, insufficient lean burn stability and low fuel and main air mixing efficiency, etc.The present application comprises: a combustion chamber arranged inside a shell;a nozzle in communication with the combustion chamber at one end and penetrating through the shell at the other end;an end cover fixed to the shell away from the nozzle;wherein the shell, the end cover and the combustion chamber form a fuel cavity A, and the combustion chamber is provided with a plurality of injection holes for injecting oil in the fuel cavity A into the combustion chamber.The present application is used for afterburner.

Description

Technical Field

[0001] This invention relates to the field of gas turbine afterburner technology, and more specifically to an afterburner hot jet ignition device. Background Technology

[0002] Afterburners are widely used due to their ability to significantly increase thrust in a short time. Located between the power turbine and the exhaust nozzle, the afterburner requires rapid response during critical moments such as takeoff and climb, and its ignition speed and reliability directly affect the aircraft's survivability. However, the high inlet velocity and low oxygen content of afterburners increase the difficulty of ignition and efficient combustion, directly affecting the reliability and stability of the combustor. The actual performance of afterburners is affected by inlet conditions.

[0003] In a traditional afterburner, the combustion chamber is located after the turbine exit and before the exhaust nozzle. The structure of the afterburner consists of a diffuser, mixer, injector, rectifier, flame stabilizer, heat shield, and ignition device. In afterburner mode, high-temperature combustion gases from the turbine exit mix with cooling air from the bypass duct in the mixer, then flow through the diffuser and mix with the fuel. Ignition occurs under the action of the igniter. The flame propagates through the ignition source in the recirculation zone behind the rectifier, forming a stable flame and continuous combustion. Behind the cavity, the fuel flows with the recirculation zone downwards into the combustion chamber for complete combustion.

[0004] Therefore, it is necessary to conduct research on the effects of typical import parameters on the ignition and combustion characteristics of afterburners in order to broaden the ignition boundary, organize efficient combustion, and ensure the reliability and stability of aero engines under high maneuverability. Summary of the Invention

[0005] This invention proposes a hot jet ignition device for an afterburner, which solves the problems of existing integrated afterburners, such as difficulty in ignition, slow flame propagation, insufficient lean-burn stability, and low fuel-air mixing efficiency.

[0006] The technical solution adopted by the present invention to solve the above problems includes: The combustion chamber is located inside the outer casing; The nozzle has one end connected to the combustion chamber and the other end passing through the outer casing; End cap, fixed to the end of the housing away from the nozzle; The outer shell, end cap, and combustion chamber form a fuel chamber A, and the combustion chamber is provided with several nozzles for injecting oil from the fuel chamber A into the combustion chamber.

[0007] Furthermore, the nozzle is disposed on the wall of the combustion chamber and near the end cap.

[0008] Furthermore, the outer casing wall is provided with an oil supply port and an oil outlet, which are connected to the fuel chamber A.

[0009] Furthermore, the end cap is provided with an air branch pipe that communicates with the interior of the combustion chamber.

[0010] Furthermore, the air branch pipes are provided in a plurality of circumferentially distributed configurations, and the axis of the air branch pipes is tangentially inclined along the end cap.

[0011] Furthermore, the combustion chamber has an end face on the side near the end cover, and the end face has an inclined hole, with the air branch pipe corresponding to the inclined hole.

[0012] Furthermore, an igniter seat is provided in the middle of the end face, and the igniter seat passes through the middle of the end cover.

[0013] Furthermore, the nozzle is provided with a boss, which is sealed to the inner wall of the housing.

[0014] Furthermore, the nozzle is provided with a fixing plate, which is connected to the combustion chamber.

[0015] Furthermore, the nozzle inlet has a converging structure.

[0016] The beneficial effects of this invention are: 1. The device achieves direct ignition and continuous stable combustion support for the afterburner by constructing a stable, high-energy hot jet channel at the rear of the main combustion chamber. Without significantly increasing structural complexity and pressure loss, it significantly improves ignition reliability, combustion efficiency and operating stability range.

[0017] 2. The inlet flow field of the afterburner is actively reconstructed through a coupled organization method of "rotating hot jet + internal swirling mixing". By introducing a multi-branch air distribution method that combines axial air supply and tangential air intake inside the device, a swirling structure with strong angular momentum is formed in the combustion zone, which works synergistically with the tangential fuel injection, thereby establishing an efficient, compact and controllable ignition and combustion flow environment in a limited space.

[0018] 3. Utilizing the entrainment and turbulence-induced capabilities of the rotating hot jet upon entering the mainstream to enhance the rapid mixing process of fuel and air. When the rotating jet interacts with the mainstream in the afterburner, it generates significant shear layer structures, vortex diffusion, and radial entrainment effects, enabling the high-temperature jet to expand simultaneously in the axial and radial directions, rapidly transporting energy and active free radicals to the core region of the mainstream. Through optimized design of the air branch distribution method, swirl intensity, and jet outlet structure, the momentum flux of the jet is matched with the mainstream flow characteristics, thereby achieving uniform diffusion of energy and components within a shorter propagation distance and avoiding problems such as insufficient penetration or excessively rapid energy decay in traditional direct-jet ignition.

[0019] 4. Fuel enters the swirling zone, where it undergoes intense shear mixing with the air swirling flow. Upon entering the combustion zone, the fuel is rapidly entrained, stretched, and broken up, forming a homogeneous combustible mixture, which is reliably ignited under the influence of high-temperature reflux and the rotating jet. This structure not only improves fuel utilization and combustion uniformity but also avoids localized fuel enrichment and wall adhesion problems, effectively reducing the risk of carbon buildup and heat loss.

[0020] 5. By creating a high-temperature hot jet with rotating characteristics at the device outlet, a local recirculation and high-temperature recirculation zone is established in the inlet region of the afterburner. On the one hand, this zone can prolong the residence time of the combustible mixture, promoting the continued reaction of components that have not yet been fully mixed or reacted; on the other hand, the high-temperature products play a continuous ignition role for the newly entering mixture, forming a stable flame anchoring zone, thereby significantly expanding the lean-burn stable operating range and reducing the risk of flameout. The nozzle adopts a modular and replaceable design, which can flexibly adjust the jet structure and energy level according to different engine operating conditions and thrust requirements, further enhancing the adaptability and engineering application value of the device. Attached Figure Description

[0021] Figure 1 This is an overall schematic diagram of the present invention; Figure 2 This is a cross-sectional view of the present invention; Figure 3 This is the front view of the present invention; Figure 4 This is a schematic diagram of the outer casing of the present invention; Figure 5 This is a schematic diagram of the combustion chamber of the present invention; Figure 6 This is a schematic diagram of the nozzle of the present invention; Figure 7 This is a cross-sectional view of the nozzle of the present invention; Figure 8 This is a front view of the end cap of the present invention; Figure 9 This is a perspective view of the end cap of the present invention; Figure 10 Velocity contour plots of the intermediate cross section of the hot jet device under different fuel injection quantities; Figure 11 Temperature cloud diagrams of the intermediate cross section of the hot jet device under different fuel injection quantities; Figure 12 The outlet velocity of the hot jet device under different fuel injection quantities; Figure 13 The outlet temperature of the hot jet device under different fuel injection quantities; Figure 14 The mole fraction of the substance at the outlet of the hot jet device under different fuel injection rates.

[0022] In the diagram: 1. Outer shell; 2. End cap; 3. Combustion chamber; 4. Air branch pipe; 5. Fuel inlet; 6. Nozzle; 7. Spray hole; 8. Fuel outlet; 9. Fixed plate; 10. End face; 11. Inclined hole; 12. Igniter seat; 13. Boss; 14. Shrinkage structure. Detailed Implementation

[0023] Specific implementation method one: Combining Figure 1 This embodiment describes an afterburner hot jet ignition device, arranged axially along the engine between the main combustion chamber and the afterburner. The overall structure includes: a combustion chamber 3 housed inside a housing 1; a nozzle 6, one end connected to the combustion chamber 3 and the other end passing through the housing 1; and an end cap 2 fixed to the end of the housing 1 away from the nozzle 6. The housing 1, end cap 2, combustion chamber 3, and nozzle 6 form a fuel chamber A. The combustion chamber 3 has several nozzle holes 7 for injecting oil from the fuel chamber A into the combustion chamber 3. Fuel is first injected into the fuel chamber A, and a portion enters the combustion chamber 3 through the nozzle holes 7, mixing with the swirling compressed air entering from the end cap 2, forming a rotating flow field. After ignition, the fuel combustion forms a swirling combustion zone, generating high-temperature, high-energy gas which then enters the afterburner as a rotating hot jet through the nozzle 6, achieving rapid ignition and stable combustion in the afterburner.

[0024] The outer casing 1 is made of high-temperature resistant alloy material and is reliably sealed to the rear casing of the main combustion chamber through flanges or clamps. Its axial outlet is coaxially connected to the inlet of the afterburner to ensure that the hot jet enters the mainstream area of ​​the afterburner in the shortest path and reduces energy attenuation.

[0025] Combustion chamber 3 has several nozzles evenly distributed circumferentially. The number, diameter, and angle of the nozzles are designed to match the target flow rate and mixing requirements. In this embodiment, four nozzles are preferred. The fuel forms a high-speed tangential jet at the nozzle 7 and enters the swirling air field, either in the same direction as the air swirl or at a certain angle, to enhance shearing and entrainment. This structure allows the fuel to be torn, stretched, and uniformly dispersed in the swirling airflow within a very short distance, forming a combustible mixture with a controllable equivalence ratio. For liquid fuel operation, a pre-atomization structure can be used at the nozzle 7, or small-scale disturbance components can be introduced into the cavity to further improve atomization quality and evaporation rate.

[0026] In this embodiment, the nozzle 7 is located on the wall 9 of the combustion chamber 3, near the end cap 2. This ensures that the nozzle is positioned at the swirling airflow, allowing for thorough mixing of fuel and air, and ignition by the igniter.

[0027] In this embodiment, the outer casing 1 has an oil supply port 5 and an oil outlet 8 on its wall surface, which are connected to the fuel chamber A. Fuel enters the fuel chamber A through the oil supply port 5, part of which enters the combustion chamber 3 through the nozzle 7, and the other part flows out through the oil outlet 8. The nozzle 7 can be replaced with a nozzle to increase the atomization effect and facilitate the adjustment of the injection angle.

[0028] In this embodiment, the end cap 2 is provided with an air branch pipe 4 that communicates with the interior of the combustion chamber 3.

[0029] In this embodiment, the air branch pipes 4 are provided in a plurality of circumferentially distributed configurations, with their axes inclined tangentially along the end cap 2. After compressed air enters the end cap, the four circumferentially equally spaced air branch pipes are optimized in terms of cross-sectional area and flow resistance to ensure balanced flow in each branch. The air branch pipes extend axially and connect to the flow guide structure at the combustion zone inlet. The flow guide structure consists of inclined guide vanes or swirl channels, allowing the air to possess both axial and tangential velocity components upon entering the combustion zone, thereby forming a stable and controllable swirling field within the combustion zone. By adjusting the guide vane angle, channel contraction ratio, and branch pipe flow distribution ratio, suitable swirl numbers and recirculation zone dimensions can be obtained under different operating conditions, ensuring that the flow field provides a sufficient recirculation stability zone without introducing excessive total pressure loss.

[0030] In this embodiment, the combustion chamber 3 has an end face 10 near the end cap 2, and the end face 10 has an inclined hole 11. The air branch pipe 4 corresponds to the inclined hole 11. Compressed air passes through the air branch pipe 4, and then through the coaxial inclined hole 11 before entering the combustion chamber 3 to form a swirling flow.

[0031] In this embodiment, an igniter seat 12 is provided in the middle of the end face 10, and the igniter seat 12 passes through the middle of the end cover 2. The igniter seat 12 is cylindrical, and an igniter can be installed inside to ignite the mixture in the swirling zone.

[0032] In this embodiment, the nozzle 6 is provided with a boss 13, which is sealed to the inner wall of the outer casing 1. The nozzle 6 is provided with a fixing plate 9, which is connected to the combustion chamber 3. The inlet of the nozzle 6 is a contraction structure 14. The nozzle is connected to the combustion zone outlet by bolts, and nozzle modules with different throat diameters, expansion angles, and internal guiding structures can be selected according to different engine operating conditions. By changing the nozzle geometry parameters, the jet exit velocity, rotation intensity, and diffusion angle can be adjusted, thereby obtaining matching ignition energy density and coverage under different thrust conditions. The inner wall of the nozzle can be provided with a high-temperature resistant coating or a porous cooling structure. If necessary, some cooling air can be introduced to form a thin-film cooling film to improve service life and structural reliability under high-temperature environments. The nozzle 6 adopts a modular and replaceable design.

[0033] Working Principle: Initial ignition is achieved first in the swirling combustion zone via an igniter or upstream high-temperature gas, forming a stable flame in the swirling recirculation core region. With a continuous supply of fuel and air, the flame is stably anchored in the recirculation zone and propagates downstream, releasing heat that continuously heats the surrounding airflow, gradually establishing a high-temperature, highly reactive product environment within the combustion zone. This high-temperature gas is accelerated and transported to the nozzle outlet under the influence of the swirling flow and axial pressure gradient, forming a high-energy thermal jet with pronounced rotational characteristics. This jet not only carries high temperature but also contains active free radicals and turbulent pulsating structures, allowing it to rapidly exchange energy and mass with the mainstream fuel-air mixture upon entering the afterburner, achieving rapid and reliable ignition.

[0034] In the inlet region of the afterburner, the rotating hot jet interacts with the mainstream airflow to form a local recirculation and shear mixing zone. The entrainment effect of the rotating jet draws surrounding mainstream air and fuel into the jet core region, achieving rapid mixing. Simultaneously, the jet-induced low-pressure zone causes some high-temperature products to flow back upstream, forming a stable flame anchoring zone. This recirculation zone not only prolongs the residence time of the combustible mixture, allowing incompletely evaporated or reacted fuel to continue combustion, but also provides a continuous ignition source for newly entering mixtures, thereby significantly expanding the stable combustion range under lean and high-load conditions and reducing the risk of flameout.

[0035] Experiments, such as Figures 10 to 14 As shown: The injection rates of different hot jet devices were set to obtain the velocity, temperature and material composition at the outlet section. The mass flow rate of injection rate 1 was 0.058 g / s, the mass flow rate of injection rate 2 was 0.0812 g / s, the mass flow rate of injection rate 3 was 0.0928 g / s, the mass flow rate of injection rate 4 was 0.1044 g / s, the mass flow rate of injection rate 5 was 0.116 g / s, and the mass flow rate of injection rate 6 was 0.232 g / s.

[0036] like Figure 10 As shown in the velocity cloud diagram of the middle section of the hot jet device under different fuel injection quantities, it can be seen that as the fuel injection quantity increases, the outlet velocity first increases and then decreases. Due to the sudden reduction in the diameter of the outlet section pipe, its velocity will increase, thereby achieving the purpose of increasing the hot jet velocity and forming a high-temperature jet. At the same time, when the fuel injection quantity is moderate, the combustion is most complete, and the outlet velocity reaches the maximum.

[0037] like Figure 11 As shown in the temperature cloud diagram of the middle section of the hot jet device under different fuel injection quantities, it can be seen that as the fuel injection quantity increases, the outlet temperature first increases and then decreases. As the fuel injection quantity increases, the combustion is more complete, and the cross-sectional temperature gradually increases. As the fuel injection quantity continues to increase, the oxygen quantity is insufficient, the combustion is incomplete, the cross-sectional temperature decreases, and the outlet temperature decreases.

[0038] like Figure 12 and3 As shown in the figure, the outlet velocity and temperature of the hot jet device change trends under different fuel injection quantities. It can be seen that with the increase of fuel injection quantity, the outlet velocity first increases and then decreases, and the outlet temperature first increases and then decreases.

[0039] like Figure 14 As shown, the mole fraction of the substance at the outlet of the hot jet device varies under different fuel injection rates. With the increase of fuel injection rate, the mole fraction of CO2 first increases slightly and then decreases, the mole fraction of H2O first increases and then decreases, the mole fraction of O2 gradually decreases, the mole fraction of CO gradually increases, the mole fraction of OH first increases and then decreases, the mole fraction of O first increases and then decreases, and the mole fraction of H first increases and then decreases. With the increase of fuel injection rate, the degree of combustion first increases and then decreases.

[0040] After entering the swirling combustion zone along the air distribution system, air gradually develops a significant swirling motion due to structural expansion and flow deflection. This establishes a flow field structure with a certain swirling intensity within the combustion zone. The formation of the swirling flow enhances the radial transport capacity of the fluid, resulting in strong lateral momentum exchange in the cross-sectional direction. Furthermore, it induces localized low-speed recirculation structures within the combustion zone, providing the necessary flow conditions for stable combustion. Simultaneously, fuel is transported to the swirling combustion zone through fuel pipes, where it couples with the air swirling flow. Under shearing and vortex entrainment, it is rapidly stretched, coiled, and diffuses towards the mainstream core area, significantly enhancing the convective mixing process between fuel and air. In addition, the swirling structure continuously entrains surrounding air into the fuel-rich region, gradually distributing the fuel evenly and forming a relatively uniform combustible mixture field. This three-dimensional vortex flow structure, formed by the combined axial airflow rotation and tangential fuel injection, not only enhances the atomization and mixing effect of the fuel, but also establishes a stable flow and mixing environment in the combustion zone, providing favorable conditions for reliable ignition and stable combustion of the combustible mixture.

[0041] This embodiment can also match key parameters according to different engine types and fuel types, including the number and distribution of air manifolds, swirl induction angle, fuel nozzle diameter and number, nozzle throat diameter and expansion ratio, etc. Through the synergistic optimization of the above parameters, the overall optimal ignition energy, mixing intensity and flame stability can be achieved while ensuring a low total pressure loss. The device has a compact overall structure and few components, which facilitates processing, manufacturing and maintenance, and is suitable for various integrated afterburner structures.

Claims

1. A thermal jet ignition device for an afterburner, characterized in that, include: The combustion chamber (3) is located inside the outer casing (1); The nozzle (6) is connected at one end to the combustion chamber (3) and at the other end through the outer shell (1). End cap (2) is fixed to the end of the outer shell (1) away from the nozzle (6); The outer shell (1), end cap (2), combustion chamber (3) and nozzle (6) form a fuel chamber A. The combustion chamber (3) is provided with several nozzles (7) for injecting oil from the fuel chamber A into the combustion chamber (3).

2. The afterburner thermal jet ignition device according to claim 1, characterized in that, The nozzle (7) is located on the wall (9) of the combustion chamber (3) and close to the end cap (2).

3. The afterburner thermal jet ignition device according to claim 1, characterized in that, The outer casing (1) has an oil supply port (5) and an oil outlet (8) on its wall surface and is connected to the fuel chamber A.

4. The afterburner thermal jet ignition device according to claim 1, characterized in that, The end cap (2) is provided with an air branch pipe (4) that communicates with the interior of the combustion chamber (3).

5. The afterburner thermal jet ignition device according to claim 1, characterized in that, The air branch pipe (4) is provided with several circumferentially distributed, and the axis of the air branch pipe (4) is tangentially inclined along the end cap (2).

6. The afterburner thermal jet ignition device according to claim 5, characterized in that, The combustion chamber (3) has an end face (10) on the side near the end cap (2), and the end face (10) has an inclined hole (11). The air branch pipe (4) corresponds to the inclined hole (11).

7. The afterburner thermal jet ignition device according to claim 6, characterized in that, An igniter seat (12) is provided in the middle of the end face (10), and the igniter seat (12) passes through the middle of the end cover (2).

8. The afterburner thermal jet ignition device according to claim 1, characterized in that, The nozzle (6) is provided with a boss (13), which is sealed to the inner wall of the outer shell (1).

9. The afterburner thermal jet ignition device according to claim 1, characterized in that, The nozzle (6) is provided with a fixing plate (9), which is connected to the combustion chamber (3).

10. The afterburner thermal jet ignition device according to claim 1, characterized in that, The inlet of the nozzle (6) is a constriction structure (14).

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