A concave flame stabilizer structure and its fuel injection and cooling method, and an afterburner.

Abstract

This invention discloses a concave cavity flame stabilizer structure, its fuel injection and cooling method, and an afterburner. The structure includes a symmetrical Tesla valve, a fluid oscillator, and shape memory alloy ribs. The Tesla valve is located at the front end of the evaporation chamber of the afterburner, utilizing its unidirectional flow resistance characteristics to suppress fuel backflow caused by pressure fluctuations and ensure stable fuel supply. The fluid oscillator replaces the traditional injection hole, converting the fuel-air mixture into a high-frequency, large-scale periodic swept jet injected into the concave cavity, improving atomization, evaporation, and mixing efficiency. The shape memory alloy ribs are located on the cold side of the bottom and rear wall of the concave cavity, automatically adjusting their shape according to changes in wall temperature to achieve dynamic matching between cooling intensity and heat load. This invention, through the system integration of fuel supply, combustion, and cooling, solves the problems of fuel backflow, low atomization efficiency, and poor adaptability of the cooling system under wide operating conditions in traditional concave cavity structures, significantly improving the combustion efficiency and thermal protection reliability of the afterburner.

Description

Technical Field

[0001] This invention relates to the field of aero-engine technology, and in particular to a concave flame stabilizer structure and its fuel injection and cooling method, and an afterburner. Background Technology

[0002] With the continuous increase in turbine outlet temperature, hot-end components such as afterburners face increasingly severe challenges from high thermal loads and the demand for high-efficiency combustion. As a core component, the performance of the flame stabilizer directly determines the ignition, flame stabilization boundary, and overall efficiency of the combustion chamber. Therefore, developing an integrated flame stabilizer technology that can simultaneously achieve efficient and stable combustion with reliable, adaptive thermal protection has become an inevitable trend to overcome existing performance bottlenecks.

[0003] Among various stabilization solutions, the cavity flame stabilizer exhibits significant application potential due to its compact structure, low flow resistance loss, and ability to provide a stable recirculation zone. This configuration is easily integrated with engine flow channels and can utilize the bypass duct airflow for wall cooling. However, existing cavity-based integrated solutions still face three interrelated deep-seated technical bottlenecks in their progress towards practical engineering application, hindering their full performance realization:

[0004] The stability of fuel supply has inherent flaws. When engine operating conditions change, the pressure inside the combustion chamber fluctuates drastically, easily triggering reverse fuel flow (i.e., "backflow") in the evaporation chamber. This backflow phenomenon disrupts the continuity and stability of fuel supply, becoming a potential source of uneven combustion, efficiency fluctuations, and even stalling. Existing technologies mostly rely on complex active control systems to stabilize fuel pressure, which are complex and face reliability challenges.

[0005] The core efficiency of fuel atomization and mixing urgently needs improvement. Traditional concave combustion chambers mostly use simple direct-injection nozzles, which produce fuel jet atomized particles that are coarse, have slow evaporation rates, and are insufficiently mixed with the main combustion gases. This directly leads to prolonged ignition delay, limited flame propagation speed, and difficulty in further improving combustion efficiency, failing to meet the stringent requirements of advanced engines for combustion chamber performance.

[0006] The thermal protection system suffers from a severe lack of adaptability across various operating conditions. While the cavity enhances combustion performance, its walls also bear extreme and dynamically changing thermal loads. Currently, this is mainly addressed by film cooling or enhanced heat transfer structures with fixed geometry (such as turbulence columns). The former suffers from problems such as the film being easily torn apart by the mainstream and low cooling efficiency; the latter is a static design and cannot respond to changes in operating conditions: it causes excessive flow resistance and cooling waste at low operating conditions, and leads to wall overheating due to insufficient heat dissipation at high operating conditions. In addition, the thermal deformation of the wall itself can change the geometry of the cooling channels, further deteriorating the cooling effect and reducing system reliability. Summary of the Invention

[0007] Objectives of the invention: The present invention aims to provide a concave cavity flame stabilizer structure that combines steady-flow fuel supply, active atomization, and adaptive cooling; the second objective of the present invention is to provide a fuel injection and cooling method for the concave cavity flame stabilizer structure; the third objective of the present invention is to provide an afterburner.

[0008] Technical solution: The concave flame stabilizer structure of the present invention includes a symmetrical Tesla valve, a fluid oscillator, and shape memory alloy ribs. The symmetrical Tesla valve is located at the front end of the evaporation chamber of the afterburner to suppress fuel backflow. The fluid oscillator is located at the connection between the front wall of the concave cavity and the evaporation chamber to convert the fuel-air mixture into a periodic swept jet that is injected into the concave cavity. The shape memory alloy ribs are located on the cold side of the bottom surface and / or rear wall of the concave cavity to adaptively adjust heat exchange according to changes in wall temperature.

[0009] Furthermore, the fluid oscillator includes an inlet throat, a main chamber, an intermediate throat, a secondary chamber, an outlet nozzle, and a pair of feedback channels connected in sequence.

[0010] Furthermore, the inlet throat width is d, the main chamber inlet width is d1=1.1d, the intermediate throat width is d2=2.17d, the outlet nozzle width is d3=1.14d, the feedback channel width is e=0.36d, the overall length is c=7.25d, and the fluid oscillator thickness is 0.1~0.3δ1, where δ1 is the thickness at the connection between the front wall of the concave cavity and the evaporation chamber.

[0011] Furthermore, the Tesla valve has an inlet section L3, an intermediate section L2, an outlet section L1, and a diversion section L4 of equal length, a diversion angle θ = 10°~60°, and an inlet section thickness of 0.5~1.5 δ2, where δ2 is the thickness of the afterburner wall.

[0012] Furthermore, the formula for calculating the inner and outer arc radii of the Tesla valve is as follows:

[0013]

[0014] in, Let be the inner radius of the Tesla valve. The outer radius of the Tesla valve is... This refers to the width of the diversion section.

[0015] Furthermore, air film holes are made on each wall surface of the cavity, with a spacing of 5.0~8.0mm between the air film holes.

[0016] Furthermore, the ribs are straight ribs with a rib width L = 25~55mm, a rib thickness t = 0.5mm, and the rib spacing s is consistent with the air film hole spacing.

[0017] Furthermore, the deformation of the shape memory alloy ribs is related to temperature in a piecewise function:

[0018]

[0019] Among them, M f M s A s and A f These represent the temperatures at which the martensitic transformation begins, ends, and begins and ends, respectively; F max This represents the maximum deformation of the shape memory alloy. The instantaneous temperature of the local environment where the rib is located; This represents the deformation amount of the shape memory alloy.

[0020] The fuel injection and cooling method based on the above-described concave flame stabilizer structure of the present invention includes the following steps:

[0021] Flow-controlled fuel supply: Fuel is supplied to the fluid oscillator after being regulated by a Tesla valve;

[0022] Oscillating atomization: Fuel mixes with high-temperature combustion gas in a fluid oscillator and is converted into a swept jet that is injected into the concave cavity;

[0023] Adaptive cooling: Shape memory alloy fins automatically adjust their shape according to changes in wall temperature, achieving dynamic matching of cooling intensity. They automatically retract under low operating conditions to reduce resistance and cooling waste, and actively extend under high operating conditions to enhance heat dissipation. While ensuring wall safety, this achieves full-condition optimization of the cooling system's energy efficiency, and the structure is simple and reliable.

[0024] The afterburner of the present invention includes the above-mentioned concave flame stabilizer structure, and the wall thickness δ2 of the afterburner is 2~10mm.

[0025] Beneficial Effects: Compared with the prior art, the significant advantages of this invention are: 1. This invention introduces a symmetrical Tesla valve upstream of the fuel supply, utilizing its low forward flow resistance and high reverse flow resistance to generate unidirectional flow resistance, suppressing fuel backflow caused by pressure fluctuations at the source, and ensuring high stability and unidirectionality of the fuel flow supplied to the combustion zone; 2. It uses a fluid oscillator instead of a traditional direct injection nozzle as the core fuel injection device, converting the steady inflow into a high-frequency, large-scale swept jet, thereby achieving ultra-fine fuel atomization, rapid evaporation, and efficient mixing within the concave cavity, significantly improving ignition conditions, widening the stable combustion boundary, and directly enhancing combustion efficiency and flame stability. In the area of ​​concentrated heat load on the concave cavity wall, adaptive heat dissipation fins made of shape memory alloy are integrated. The fins can sense the local wall temperature and generate active geometric deformation through phase change drive, thereby reducing resistance under low operating conditions and enhancing heat transfer under high operating conditions, realizing dynamic and precise matching of cooling intensity, and achieving synergistic cooperation between passive fluid control, active flow excitation and intelligent material properties; 2. This invention deeply integrates steady flow fuel supply, active atomization and adaptive thermal management, and for the first time optimizes the fuel supply, combustion organization and thermal protection process at the system level, aiming to achieve a comprehensive improvement in the performance, reliability and adaptability of the concave cavity flame stabilizer under a wide range of operating conditions; Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the present invention installed on the concave wall of the afterburner;

[0027] Figure 2 This is a schematic diagram of the calculation area and boundary in an embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram of a partial structure of a Tesla valve;

[0029] Figure 4 Schematic diagram of a fluid oscillator jet unit;

[0030] Figure 5 This is a schematic diagram showing the change in rib height of a shape memory alloy rib before it starts working.

[0031] Figure 6 This is a schematic diagram showing the change in rib height after the shape memory alloy ribs are in operation. Detailed Implementation

[0032] The cavity flame stabilizer structure described in this invention, such as Figure 1As shown, the system includes a symmetrical Tesla valve 1, a fluid oscillator 2, shape memory alloy fins 3, a front wall surface of the cavity 4, a bottom surface of the cavity 5, a rear wall surface of the cavity 6, an evaporator cavity 7, containing fuel gas 8, fuel injection points within the evaporator cavity 9, and a connection point 10 between the front wall surface of the cavity and the evaporator cavity. The symmetrical Tesla valve, located at the front end of the evaporator cavity in the afterburner, is used to suppress fuel backflow; the fluid oscillator, located at the connection point between the front wall surface of the cavity and the evaporator cavity, is used to convert the fuel-fuel mixture into a periodic swept jet injected into the cavity; the shape memory alloy fins, located on the cold side of the bottom surface and / or rear wall surface of the cavity, are used to adaptively adjust heat exchange according to changes in wall temperature.

[0033] The fluid oscillator mainly includes: an inlet throat 11, a main chamber 12, an intermediate throat 13, a secondary chamber 14, an outlet nozzle 15, and a pair of feedback channels 16. The width of the inlet throat is d, the inlet width of the main chamber is d1=1.1d, the width of the intermediate throat is d2=2.17d, the width of the outlet nozzle is d3=1.14d, the width of the feedback channel is e=0.36d, the overall length is c=7.25d, and the thickness of the fluid oscillator is 0.1~0.3δ1, where δ1 is the thickness at the connection between the front wall of the concave cavity and the evaporation chamber.

[0034] The Tesla valve has an inlet section L3, an intermediate section L2, an outlet section L1, and a flow splitting section L4 of equal length, with a flow splitting angle θ = 10°~60°. The inlet section thickness is 0.5~1.5 δ2, where δ2 is the thickness of the afterburner wall. The formula for calculating the inner and outer arc radii of the Tesla valve is:

[0035]

[0036] in, Let be the inner radius of the Tesla valve. The outer radius of the Tesla valve is... This refers to the width of the diversion section.

[0037] Air film vents are formed on each wall surface of the concave cavity, with a vent spacing of 5.0~8.0mm. The ribs are straight ribs with a rib width L=25~55mm and a rib thickness t=0.5mm. The rib spacing s is consistent with the air film vent spacing. The deformation of the shape memory alloy ribs and its temperature relationship satisfy a piecewise function:

[0038]

[0039] Among them, M f M s A s and A f These represent the temperatures at which the martensitic transformation begins, ends, and begins and ends, respectively; F max This represents the maximum deformation of the shape memory alloy. The instantaneous temperature of the local environment where the rib is located; This represents the deformation amount of the shape memory alloy.

[0040] In this embodiment, the inlet throat width is preferably d = 1.2 mm, serving as the design baseline. The trailing edge of the feedback channel forms a throat with a width d1 slightly larger than the inlet throat, preferably d1 = 1.32 mm. The fuel and internal combustion gas mixture is accelerated through the inlet throat, forming a high-speed jet that enters the main chamber. The main chamber and secondary chamber are separated by an intermediate throat, the width of which, d2, is designed to be greater than the jet width to limit the amplitude of jet oscillation; preferably, d2 = 2.60 mm. An outlet nozzle is located at the end of the secondary chamber, with a width d3 slightly smaller than the jet width before oscillation, preferably d3 = 1.37 mm, to ensure necessary collision interaction between the jet and the throat wall. The feedback channel width e is slightly smaller than that of a conventional oscillator, preferably e = 0.43 mm, to reduce the feedback flow rate and minimize jet momentum loss. The overall length c is designed to be 8.7 mm. The fluid oscillator thickness is designed to be 1.2 mm.

[0041] The fluid oscillator operates based on two pairs of asymmetrically growing vortices formed in the main and secondary chambers. Upon entry of the high-speed jet, its shear layer interacts with the chamber walls, inducing a pair of vortices with opposite rotation directions in each of the two chambers. These vortices roll up on the jet shear layer and grow and contract asymmetrically, disrupting the jet's symmetry and inducing initial instability. Subsequently, a feedback channel is activated: when the jet deflects to one side, the vortices in the main chamber on that side intensify, leading to a decrease in local pressure, while the pressure on the corresponding side of the secondary chamber increases. This pressure difference drives fluid into the main chamber through the feedback channel on the same side, further agitating and pushing the jet to the opposite side. This process alternates between the two sides, forming a stable, harmonic self-excited oscillation.

[0042] In this implementation case, such as Figure 3 As shown, the forward flow F and the reverse flow R of the fluid inside the Tesla valve are as follows. The dimensions of each section of the Tesla valve structure are as follows: inlet section width a = 2.0 mm, inlet section thickness 2.0 mm, inlet section L3 = 5.0 mm, intermediate section L2 = 5.0 mm, outlet section L1 = 5.0 mm, diversion section L4 = 5.0 mm, diversion angle θ = 30°, diversion section width b = 1.0 mm, inner arc radius r1 = 1.3 mm, outer arc radius r2 = 2.3 mm.

[0043] In this implementation, the shape memory alloy ribs work as follows: below the critical design temperature (i.e., the martensitic phase transformation initiation temperature), the ribs maintain their initial rib height; when the wall temperature rises and exceeds the critical design temperature, the shape memory alloy undergoes a phase transformation, driving the ribs to extend, thereby significantly increasing the heat transfer area on the cooling side and enhancing flow disturbance. After the ribs extend, they not only directly increase the contact area with the cooling medium, but also significantly enhance the convective heat transfer process by disrupting the flow boundary layer and inducing turbulent wakes, achieving active enhanced cooling of high heat load areas.

[0044] In this implementation case, the computational domain is as follows: Figure 2 As shown, to reduce the amount of mesh and utilize the rotational periodicity of the structure, a sector model corresponding to 1 / 16 (i.e., 22.5°) of the 360° circumference of the complete afterburner was established as the computational domain. The two sector surfaces of this model are set as the rotational periodic boundary D to simulate the full circumference structure. A is the outer bypass cooling gas inlet, and B is the inner combustion gas inlet. The two are mixed and recirculated in the concave cavity before flowing out from the outlet C. The thickness δ1 at the connection between the front wall of the concave cavity and the evaporator cavity is 6.0 mm, and the thickness δ2 of the afterburner wall is 2.0 mm. The rib width L of the bottom surface of the concave cavity is 54 mm, the initial rib height H1 is 3 mm, the rib thickness t is 0.5 mm, and the rib spacing s is 7 mm; the rib width L of the rear wall of the concave cavity is 28 mm, the initial rib height H1 is 3 mm, the rib thickness t is 0.5 mm, and the rib spacing s is 7 mm.

[0045] In this implementation case, the flow field and temperature field are calculated and solved using the commercial computing software Ansys Fluent.

[0046] In this implementation case, a numerical simulation of the computational model was performed using typical operating conditions of an afterburner. Traditional fuel injection channels were arranged on the combustion chamber wall for fuel atomization. During simulated combustion, a portion of the rear wall of the concave cavity experienced high heat load, causing the wall temperature to exceed the material's temperature resistance limit, and resulting in low combustion efficiency. Compared to the traditional structure, under the same fuel mass flow rate, the concave cavity flame stabilizer of this invention exhibits comprehensive performance improvements: combustion efficiency is increased by approximately 5%; in terms of thermal protection, the average temperature of the rear wall of the concave cavity is reduced by approximately 8%, and the maximum temperature of local hot spots is reduced by approximately 20%, demonstrating the effectiveness of this integrated design in improving combustion efficiency and enhancing cooling capacity.

[0047] The fuel injection and cooling method based on the above-described concave flame stabilizer structure of the present invention includes the following steps:

[0048] Flow-controlled fuel supply: Fuel is supplied to the fluid oscillator after being regulated by a Tesla valve;

[0049] Oscillating atomization: Fuel mixes with high-temperature combustion gas in a fluid oscillator and is converted into a swept jet that is injected into the concave cavity;

[0050] Adaptive cooling: Shape memory alloy fins automatically adjust their shape according to changes in wall temperature, achieving dynamic matching of cooling intensity. They automatically retract under low operating conditions to reduce resistance and cooling waste, and actively extend under high operating conditions to enhance heat dissipation. While ensuring wall safety, this achieves full-condition optimization of the cooling system's energy efficiency, and the structure is simple and reliable.

[0051] The afterburner of the present invention includes the above-mentioned concave flame stabilizer structure, and the wall thickness δ2 of the afterburner is 2~10mm.

Claims

1. A reentrant flame holder structure, characterized by, The symmetrical Tesla valve (1), the fluid oscillator (2) and the shape memory alloy fin (3) are included, the symmetrical Tesla valve is arranged at the front end of the force chamber evaporation cavity and is used for inhibiting the fuel backflow, the fluid oscillator is arranged at the connection of the concave cavity front wall surface and the evaporation cavity and is used for converting the fuel-gas mixture into a periodic sweeping jet to spray into the concave cavity, and the shape memory alloy fin is arranged at the cold side of the concave cavity bottom surface and / or rear wall surface and is used for self-adapting adjustment of heat exchange according to the wall surface temperature change.

2. The cavity flame holder structure of claim 1, wherein, The fluid oscillator comprises an inlet throat, a main chamber, an intermediate throat, a secondary chamber, an outlet nozzle and a pair of feedback channels connected in sequence.

3. The cavity flame holder structure of claim 2, wherein, The inlet throat width is d, the main chamber inlet width d1=1.1d, the intermediate throat width d2=2.17d, the outlet nozzle width d3=1.14d, the feedback channel width e=0.36d, the overall length c=7.25d, and the fluid oscillator thickness is 0.1-0.3δ1, wherein δ1 is the thickness of the connection of the concave cavity front wall surface and the evaporation cavity.

4. The structure of a cavity flame holder according to claim 1, wherein The inlet section L3, the intermediate section L2, the outlet section L1 and the shunt section L4 of the Tesla valve have equal lengths, the shunt angle θ=10°-60°, and the inlet section thickness is 0.5-1.5δ2, wherein δ2 is the wall thickness of the force chamber.

5. The cavity flame holder structure of claim 4, wherein, The calculation formula of the inner and outer arc radii of the Tesla valve is: wherein, Ri is the inner radius of the Tesla valve, Ro is the outer radius of the Tesla valve, W is the width of the flow splitting section.

6. The cavity flame holder structure of claim 1, wherein, Gas film holes are arranged on each wall surface of the concave cavity, and the gas film hole spacing is 5.0-8.0mm.

7. The cavity flame holder structure of claim 6, wherein, The shape memory alloy fin is a straight fin structure, the fin width L=25-55mm, the fin thickness t=0.5mm, and the fin spacing s is consistent with the gas film hole spacing.

8. The cavity flame holder structure of claim 7, wherein, The deformation and temperature relationship of the shape memory alloy fin satisfies the piecewise function: wherein M f , M s , A s and A f represent the temperature at which the martensitic transformation starts, the martensitic transformation ends, the austenitic transformation starts and the austenitic transformation ends, respectively; F max is the maximum deformation of the shape memory alloy; is the instantaneous temperature of the local environment in which the fin is located; is the deformation of the shape memory alloy.

9. A method of fuel injection and cooling based on the cavity flame holder structure according to any one of claims 1-8, characterized in that, The method comprises the following steps: Steady flow oil supply: the fuel is supplied to the fluid oscillator after being supplied to the Tesla valve; Oscillating atomization: the fuel is mixed with the high-temperature gas in the fluid oscillator and converted into a sweeping jet to spray into the concave cavity; Self-adapting cooling: the shape memory alloy fin automatically adjusts the shape according to the wall surface temperature change to realize dynamic matching of the cooling intensity.

10. A thrust-reverser combustion chamber, characterized in that The concave cavity flame stabilizer structure of any one of claims 1-8 is included, and the force chamber wall thickness δ2 is 2-10mm.

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