A multi-stage lobe type cavity trapped vortex type strut flame holder

Abstract

The application discloses a multi-stage lobe type cavity trapped vortex type strut flame stabilizer, which comprises a strut, wherein the tail of the strut is perpendicular to the flow direction of a thrust chamber; the two sides of the strut are respectively provided with cavities; the lower side of each cavity is sequentially provided with a first lobe mixer and a second lobe mixer; the second lobe mixer is located at the tail of the strut and is staggered with the first lobe mixer. The application adopts an asymmetric design to solve the problem of poor flow field distribution between any two struts in the actual application of the multi-strut array type arrangement, and uses the cavity to obtain a stable trapped vortex to preliminarily mix fuel and air; the first lobe mixer generates a flow direction vortex structure to efficiently mix the preliminarily mixed fuel-air mixture in the cavity with external airflow; after the first lobe mixer, the mixed oil-gas is further mixed with the airflow at the second lobe mixer, so that the fuel is more uniformly distributed in the combustion chamber, the distribution area of the fuel in the thrust chamber is expanded, and the fuel is more fully combusted when ignited.

Description

Technical Field

[0001] This invention relates to the field of afterburners for aero engines, and more particularly to a multi-stage lobe-type concave cavity vortex-type flame stabilizer for an integrated afterburner. Background Technology

[0002] The combat capability of a fighter jet is largely influenced by its engine. The afterburner, located between the turbine and the engine exhaust nozzle, injects secondary fuel into the exhaust gases flowing through the turbine, mixing them with fresh air introduced from the bypass duct for combustion to generate greater thrust. As a crucial component of an aero-engine, the afterburner accounts for only about 20% of the engine's total mass, yet it can increase the thrust of turbofan engines by 40%–50% and turbojet engines by 60%–70%. The afterburner comprehensively improves engine maneuverability and plays a vital role in the development of military aircraft.

[0003] In traditional afterburners, the flame stabilizer and support plate are arranged separately, occupying a considerable amount of space in the engine. Furthermore, more components mean a decrease in the total pressure recovery coefficient of the afterburner, resulting in significant flow resistance losses under cold conditions without afterburner operation. Therefore, integrating the traditional flame stabilizer and support plate into a single design can shorten the engine length and thus reduce engine weight.

[0004] Existing integrated flame stabilizers with diffusers struggle to balance mixing efficiency and total pressure recovery coefficient. They can be broadly categorized into two types: those with a triangular spoiler at the rear, which improves mixing efficiency but significantly reduces the total pressure recovery coefficient; and those without a triangular spoiler, which offer better total pressure recovery but have lower mixing efficiency. In advanced integrated afterburners, the inlet flow temperature and velocity are significantly increased, shortening the fuel's residence time within the combustion chamber. With increased engine flow velocity, these two types of existing integrated flame stabilizers inevitably affect fuel atomization and mixing efficiency, leading to incomplete combustion. Furthermore, current designs rarely optimize the flow field between adjacent diffusers in multi-diffuser arrays for practical applications, and symmetrical design methods struggle to improve the uniformity of fuel and hot / cold airflow distribution.

[0005] Therefore, in the integrated design of the fuel injector, support plate, and flame stabilizer in the afterburner, it is necessary to consider both the mixing efficiency of fuel atomization and the total pressure recovery performance of the afterburner. A good design can improve the combustion stability and economy of the afterburner, enhance its performance, and has excellent development prospects. Summary of the Invention

[0006] The purpose of this invention is to solve the aforementioned problems in the prior art and provide a multi-stage, lobe-type, concave cavity, vortex-type flame stabilizer with a reliable structure. It features an optimized design for the flow field distribution in an integrated afterburner with multiple stabilizers in practical applications. It maintains good performance under both cold and hot operating conditions in the afterburner, reducing flow losses, enhancing fuel-air mixing, improving combustion efficiency, and ultimately increasing thrust. Furthermore, it can reduce the blockage ratio and improve performance even with multiple stabilizers. Specifically, hot flow refers to the process where high-temperature exhaust gas from the turbine mixes with fresh air in the afterburner and is then re-injected and ignited; cold flow refers to the engine operating without afterburner, where high-temperature exhaust gas from the turbine flows directly through the exhaust nozzle.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A multi-stage lobe-type concave cavity vortex-type support plate flame stabilizer includes a support plate with an airfoil-shaped leading edge and a tail perpendicular to the flow direction of the afterburner. Concave cavities are located on the middle of both sides of the support plate, with a primary lobe mixer and a secondary lobe mixer sequentially arranged on the lower side of each cavity. The primary lobe mixer is integrated with the cavity. The secondary lobe mixer is located at the tail of the support plate and is staggered with the primary lobe mixer. The lobe structure of the secondary lobe mixer begins at the junction of a traditional triangular spoiler and the support plate, extending through to the tail of the support plate. The line connecting the centers of the lobes of the primary lobe mixer is parallel to the boundary of the cavity, and the lobes of the secondary lobe mixer are vertically arranged in the radial direction of the afterburner.

[0009] The depth of the cavity is 20% to 40% of the thickness of the support plate.

[0010] The width of the cavity is 7% to 15% of the length of the support plate.

[0011] The concave cavity extends longitudinally through the support plate.

[0012] The lobe structures of the primary and secondary lobe mixers are semi-circular, with the radius of a single semi-circular lobe structure accounting for 5% to 20% of the support plate height.

[0013] The lobes of the first-stage lobe mixer are tangent to the cavity structure, and the lobe depth is consistent with the depth of the cavity structure at the same position.

[0014] The first-stage beam mixers on both sides are arranged asymmetrically and alternately.

[0015] The two secondary lobe mixers on both sides are arranged asymmetrically and alternately.

[0016] The secondary beam mixer occupies 20% to 30% of the total length of the support plate in the flow direction.

[0017] Compared with the prior art, the beneficial effects achieved by the technical solution of this invention are:

[0018] The multi-stage lobe-type concave cavity vortex-type flame stabilizer of this invention can utilize the concave cavity to obtain a stable vortex for initial mixing of fuel and air; the first-stage lobe mixer can efficiently mix the initially mixed fuel-air mixture inside the concave cavity with the external incoming air by generating a flow vortex structure; after passing through the first-stage lobe mixer, the mixed fuel and air are further mixed with the incoming air at the second-stage lobe mixer, making the fuel distribution in the combustion chamber more uniform, increasing the fuel distribution area in the afterburner, and making combustion more complete during ignition.

[0019] This invention benefits from the asymmetrical design and staggered arrangement of the lobes in the two-stage lobe mixer, enabling better mixing of fuel and air without increasing flow resistance and maintaining the same flow channel area. Compared to a spoiler-free support plate, the traditional support plate with a triangular spoiler at the tail has a total pressure recovery coefficient of 90.5%, a downstream recirculation zone length of 237%, and a circumferential width of 223%. The multi-stage lobe-type concave cavity vortex-type support plate flame stabilizer of this invention has a total pressure recovery coefficient of 97.4%, a downstream recirculation zone length of 157%, and a circumferential width of 171%. This invention's integrated support plate significantly improves the recirculation zone length to achieve flame stabilization while maintaining the total pressure recovery coefficient, demonstrating remarkable effectiveness. Attached Figure Description

[0020] Figure 1 This is a left-side schematic diagram of a flame stabilizer with a support plate.

[0021] Figure 2 This is a right-side view of the flame stabilizer with a support plate.

[0022] Figure 3 This is a left-side three-dimensional structural diagram of the support plate flame stabilizer.

[0023] Figure 4 This is a three-dimensional structural diagram of the support plate flame stabilizer from the right.

[0024] Figure 5 This is a schematic diagram of the rear three-dimensional structure of the support plate flame stabilizer.

[0025] Figure 6 A left-facing three-dimensional schematic diagram of a symmetrical support plate with a concave cavity and a traditional triangular spoiler.

[0026] Figure 7 This is a circumferential diagram showing the installation of the support plate at a 30° interval.

[0027] Figure 8This is a three-dimensional schematic diagram of the support plate installed at a 30° interval.

[0028] Figure 9 When the support plates are installed at 60° intervals, the ratio of the total pressure recovery coefficient of the flame stabilizer of the support plate of the present invention and the support plate with a conventional triangular spoiler at the tail of Comparative Example 1 to the support plate without a tail spoiler of Comparative Example 2 is as follows.

[0029] Figure 10 When the support plates are installed at 60° intervals, the downstream flow velocity changes of the flame stabilizer of the support plate of the present invention, the support plate with a conventional triangular spoiler at the tail of Comparative Example 1, and the support plate without a tail spoiler of Comparative Example 2.

[0030] Figure reference numerals: 1. Cavity; 2. First-stage lobe mixer; 3. Second-stage lobe mixer; 4. Leading edge of airfoil; 5. Outer bypass inlet; 6. Inner bypass inlet; 7. Conventional triangular spoiler. Detailed Implementation

[0031] To make the technical problems, technical solutions and beneficial effects of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0032] Example 1

[0033] Reference Figures 1 to 6 This invention discloses a multi-stage lobe-type concave cavity vortex-type support plate flame stabilizer for an integrated afterburner, comprising a support plate with an airfoil-shaped leading edge to reduce flow resistance loss; this embodiment uses the NACA 66018 airfoil as an example. The dimensions of the upper and lower surfaces of the support plate are proportional to the flow field radius to ensure a consistent blocking ratio in the radial direction. The tail of the support plate is perpendicular to the flow direction of the afterburner. Concave cavities are provided in the middle of both sides of the support plate. A primary lobe mixer and a secondary lobe mixer are sequentially arranged on the lower side of each cavity. The line connecting the centers of the lobes of the primary lobe mixer is parallel to the boundary of the cavity, and the lobes of the secondary lobe mixer are vertically arranged in the radial direction of the afterburner.

[0034] The cavity 1 is located at the point where the leading edge 4 of the airfoil of the support plate is tangent to the flow field direction; the depth of the cavity 1 is related to the thickness of the support plate, and the depth of the cavity on one side can be adjusted to 20% to 40% of the thickness of the support plate according to actual needs, and the depth along the radial direction is consistent with the radius of the combustion chamber; the width of the cavity 1 accounts for 7% to 15% of the length of the support plate.

[0035] The first-stage lobe mixer 2 is located downstream of the concave cavity 1 along the flow direction. The lobes adopt a semi-circular lobe structure, with the lobe radius related to the support plate height. The radius of a single semi-circular lobe structure occupies 5% to 20% of the support plate height, corresponding to 5 to 20 semi-circular lobes. In this embodiment, the lobe radius is designed to be 10% of the support plate height, with 10 lobes in total. The arrangement is such that the height occupied by a single semi-circular lobe structure on any side of the support plate in the radial direction of the afterburner remains consistent. The specific radius varies depending on the size of the concave cavity structure, but the design ensures that the lobe is tangent to the initial concave cavity structure, and the lobe depth is consistent with the depth of the concave cavity structure at the same location. To optimize the flow field distribution when multiple support plates are simultaneously arranged in practical applications, the two sides of the first-stage lobe mixer are arranged asymmetrically and staggered. Due to the limitations of the support plate and concave cavity dimensions, the lobe sizes on both sides are different.

[0036] In designing this invention, existing technologies were taken into account, and all existing mature technologies based on support plate spraying can be used for the support plate described in this invention. The combined design of the cavity 1 and the first-stage beam mixer 2 in this invention can optimize the effect of existing spraying technologies, and the specific spraying position and quantity can be implemented according to existing mature technologies.

[0037] The secondary lobe mixer 3 is located at the tail of the support plate, corresponding to the primary lobe mixer 2 in terms of position, number, and radial height, and is 5% to 20% of the support plate height. The corresponding number of lobe structures ranges from 5 to 20. The lobe structures on both sides are arranged asymmetrically. The lobe structure begins at the junction of the traditional triangular spoiler 7 and the support plate, extending through to the tail of the support plate. Its specific height, length, radius, and other dimensions vary depending on the size of the support plate at this location. The secondary lobe mixer 3 occupies 20% to 30% of the total length of the support plate in the flow direction.

[0038] When the afterburner is operating, the incoming flow passes through the leading edge 4 of the airfoil on the support plate, forming a vortex in the concave cavity 1. The fuel injected by the injector mixes efficiently with air at the vortex, then disperses into the flow field after passing through the first-stage lobe mixer 2, flowing downstream with the incoming flow. Simultaneously, the lobe mixers on both sides of the support plate are arranged in a dog-tooth staggered pattern; this asymmetrical design allows for further mixing of the vortices formed by the lobe mixers between adjacent support plates. When the fuel-air mixture flows to the second-stage lobe mixer 3, it is further mixed with air, optimizing the fuel distribution within the afterburner. The lobe mixer designed in this invention can enhance the flowing vortices and improve the mixing efficiency between adjacent support plates.

[0039] Reference Figure 7 and Figure 8The support plates described in this invention are circumferentially arranged inside the inner inlet 6 of the afterburner. The number of support plates is related to the size of the support plates and the performance of the afterburner, but the blockage ratio must be kept less than 40%. The support plates should be arranged as close as possible to the junction of the outer inlet 5 and the inner inlet 6, where the fuel-air mixture can mix with the incoming flow from the outer inlet 5 to achieve a better mixing effect.

[0040] Comparative Example 1

[0041] The structure of this comparative example is the same as that of Example 1 in terms of the leading edge 4 of the airfoil, the cavity 1, and the first-stage beam mixer 2, but it uses a traditional triangular spoiler 7 and does not design a second-stage beam mixer 3.

[0042] Comparative Example 2

[0043] The structure of this comparative example is the same as that of Example 1 in terms of the leading edge 4 of the airfoil, the cavity 1, and the first-stage lobe mixer 2, but the second-stage lobe mixer 3 and the conventional triangular spoiler 7 are not designed.

[0044] Simulation results obtained from the commercial software Fluent are as follows Figures 9-10 As shown in Table 1, Figure 9 When the support plates are installed at 60° intervals, the ratio of the total pressure recovery coefficient of the flame stabilizer of the support plate of the present invention and the support plate with a conventional triangular spoiler at the tail of Comparative Example 1 to the support plate without a tail spoiler of Comparative Example 2 is as follows. Figure 10 The downstream flow velocity changes of the flame stabilizer of this invention, the support plate with a conventional triangular spoiler at the tail of Comparative Example 1, and the support plate without a tail spoiler of Comparative Example 2 are shown when the support plates are installed at 60° intervals. The horizontal axis x / L is the distance from the cross section of the calculation area to the end of the support plate / the length of the longest position of the support plate, where x is the distance from the cross section of the calculation area to the end of the support plate, and L is the length of the longest position of the support plate. With the airfoil leading edge 4, cavity 1, and first-stage lobe mixer 2 all identical, the total pressure recovery coefficient ratios of the airfoil with conventional triangular spoilers in Comparative Example 1 and the airfoil flame stabilizer of the present invention, compared to the airfoil without spoilers at the tail of Comparative Example 2, are 90.5% and 97.4%, respectively. The downstream flow return zone length of the airfoil with conventional triangular spoilers at the tail of Comparative Example 1 is 237% of that of the airfoil without spoilers at the tail of Comparative Example 2, and the circumferential return zone width is 223% of that of the airfoil without spoilers at the tail of Comparative Example 2. The downstream flow return zone length of the airfoil flame stabilizer of the present invention is 157% of that of the airfoil without spoilers at the tail of Comparative Example 2, and the circumferential return zone width is 171% of that of the airfoil without spoilers at the tail of Comparative Example 2.

[0045] Without a spoiler, the fuel-air mixing efficiency is poor. Adding a spoiler can improve mixing efficiency and increase the recirculation area, but it also significantly affects the total pressure recovery coefficient of the flow field. This invention designs a two-stage lobe mixer 3 to replace the traditional spoiler, which can strike a balance between total pressure loss and mixing efficiency. The asymmetric multi-stage lobe mixer designed in this invention can improve mixing efficiency and increase the recirculation area to achieve flame stabilization and improve the efficiency of the afterburner when multiple support plates are installed, ensuring that the total pressure loss is not significantly affected.

[0046] Table 1 compares the length of the recirculation zone and the total pressure recovery coefficient of the three types of support plates calculated in commercial software.

[0047] Table 1

[0048] Support plate type Size of the reflux zone Size of the circumferential reflux region Total pressure recovery coefficient Comparative Example 2 1 1 1 Comparative Example 1 2.37 2.23 0.905 This invention 1.57 1.71 0.974

[0049] In this invention, the leading edge of the support plate is an airfoil design. Theoretically, any airfoil that can reduce drag loss can be applied to the design of the support plate in this invention. In this invention, only the NACA 66018 airfoil support plate is used as an example, and a concave cavity is used to achieve the purpose of vortex retention. The concave cavity is located on the airfoil surface perpendicular to the flow direction and is combined with the airfoil of the support plate. In order to ensure a consistent blockage ratio, the ratio of the circumferential dimensions of the support plate is consistent with the ratio of the radial radius of the afterburner.

[0050] This invention innovatively designs a two-stage lobe mixer. Each stage of the lobe mixer is composed of lobe structures of different sizes, varying according to the circumferential dimensions of the support plate. Each stage of the lobe mixer on both sides of the support plate is asymmetrically designed to optimize the flow field distribution on both sides of the support plate when multiple support plates are arranged. The first-stage lobe mixer is attached to the support plate perpendicular to the flow direction, i.e., on the side wall of the support plate, and is combined with a concave cavity for efficient one-time mixing of the oil-gas mixture. The second-stage lobe mixer of this invention is located at the tail of the support plate, replacing the traditional triangular spoiler to reduce the excessive blockage ratio caused by the traditional spoiler. Its lobe structure is staggered with the first-stage lobe mixer, compensating for the uneven fuel distribution in the flow direction of the airflow passing through the first-stage lobe mixer.

Claims

1. A multi-stage lobe-type concave cavity vortex-type flame stabilizer, characterized in that: The device includes a support plate with a wing-shaped leading edge and a tail perpendicular to the flow direction of the afterburner. Both sides of the support plate have concave cavities, and a primary lobe mixer and a secondary lobe mixer are sequentially arranged on the lower side of each cavity. The primary lobe mixer is integrated with the cavity. The secondary lobe mixer is located at the tail of the support plate and is staggered with the primary lobe mixer. The line connecting the centers of the lobes of the primary lobe mixer is parallel to the boundary of the cavity, and the lobes of the secondary lobe mixer are perpendicular to the radius of the afterburner. The lobes of the primary lobe mixer are tangent to the cavity structure, and their depth is consistent with the depth of the cavity structure at the same location.

2. The multi-stage lobe-type concave cavity vortex-type support plate flame stabilizer as described in claim 1, characterized in that: The depth of the cavity is 20% to 40% of the thickness of the support plate.

3. The multi-stage lobe-type concave cavity vortex-type flame stabilizer as described in claim 1, characterized in that: The width of the cavity is 7% to 15% of the length of the support plate.

4. The multi-stage lobe-type concave cavity vortex-type support plate flame stabilizer as described in claim 1, characterized in that: The concave cavity extends longitudinally through the support plate.

5. The multi-stage lobe-type concave cavity vortex-type support plate flame stabilizer as described in claim 1, characterized in that: The first-stage and second-stage lobe mixers employ a semi-circular lobe structure, with the radius of a single semi-circular lobe structure accounting for 5% to 20% of the support plate height.

6. The multi-stage lobe-type concave cavity vortex-type support plate flame stabilizer as described in claim 1, characterized in that: The first-stage beam mixers on both sides are arranged asymmetrically and alternately.

7. The multi-stage lobe-type concave cavity vortex-type support plate flame stabilizer as described in claim 1, characterized in that: The two secondary lobe mixers on both sides are arranged asymmetrically and alternately.

8. The multi-stage lobe-type concave cavity vortex-type support plate flame stabilizer as described in claim 1, characterized in that: The secondary beam mixer occupies 20% to 30% of the total length of the support plate in the flow direction.

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