A type of locally swirling afterburner

Abstract

This invention discloses a partially swirling afterburner, comprising an outer cylinder assembly, a central body assembly, and an oil circuit assembly. The outer cylinder assembly includes an outer casing and a shock-absorbing heat shield. The central body assembly includes an inner casing, a central cone located inside the inner casing, a rectifier support plate located between the inner casing and the central cone, an outer cavity stabilizer, and a central cavity stabilizer. The outer and central cavity stabilizers are located at the rear end of the rectifier support plate. The outer cavity stabilizer forms a protrusion from the inner casing towards the outer casing, and the central cavity stabilizer is an annular cavity disposed on the central cone. The rectifier support plate includes several direct-flow blades and several swirling blades, arranged sequentially from the inside to the outside. Through the cooperation between the outer cavity stabilizer, the central cavity stabilizer, and the partially swirling rectifier support plate, centrifugal force is used to achieve radial propagation of the cavity flame, solving the problem of difficult circumferential flame connection in traditional radial stabilizers and achieving flame connection across the entire combustion chamber cross-section.

Description

Technical Field

[0001] This invention relates to afterburners for turbofan engines, and more specifically to an afterburner with localized swirling flow. Background Technology

[0002] With the development of aerospace technology, the performance requirements of aero engines are becoming increasingly demanding. The exhaust gas temperature at the turbine outlet, i.e., the inlet of the afterburner, of most modern fighter jet engines has reached as high as 1200K~1300K. This makes ignition in the afterburner easier, but the high temperature places higher demands on the heat resistance and ablation resistance of the internal structural materials of the afterburner, making a reasonable cooling design crucial.

[0003] In the integrated turbine rear frame structure commonly used in today's advanced engines, the turbine rear fairing plate is integrated with the afterburner stabilizer and fuel supply system, eliminating the fuel injection device and afterburner stabilizer in the flow path. While this reduces flow losses and shortens the length of the combustion chamber, the integrated structure of the radial stabilizer and fairing plate faces the problem of being easily eroded under high-temperature airflow. Meanwhile, because the rapidly evaporating fuel at high temperatures has a very shallow penetration depth in the high-speed airflow, it is difficult to achieve uniform circumferential diffusion of fuel and air using traditional methods of introducing jets to mix fuel mist and air. Therefore, it is necessary to add streamlined blunt bodies or concave cavities to the front section of the afterburner and employ a multi-point, multi-path fuel supply method to improve fuel and air distribution at various cross-sections and promote flame propagation and diffusion within the combustion chamber. The trade-off is greater flow resistance losses, necessitating the design of better fuel supply methods to achieve better circumferential distribution of fuel mist.

[0004] Furthermore, with the continuous development of infrared and radar technologies, the stealth requirements for fighter jets are becoming increasingly stringent. As the hot-end component at the tail of a fighter jet engine, the afterburner must also meet infrared and radar stealth requirements in its design. The traditional central truncated cone structure is no longer suitable, and a non-right-angled blunt body structure is needed to meet stealth requirements. If a swirling afterburner design with ignition near the outer wall is adopted, the airflow temperature near the center is high and the density is low, resulting in less centrifugal force generated by the swirling flow. After the flame is ignited in the outer concave cavity, the radial propagation depth of the flame towards the center is insufficient, leading to a problem of low temperature in the central area of ​​the combustion chamber. Summary of the Invention

[0005] Purpose of the invention: To address the above-mentioned shortcomings, the present invention provides an afterburner that enables fuel and air to evaporate and mix more quickly along the axial direction, thereby achieving a more compact combustion chamber structure through localized swirling.

[0006] Technical Solution: To solve the above problems, the present invention adopts a localized swirling afterburner, including an outer cylinder assembly, a central body assembly, and an oil circuit assembly. The outer cylinder assembly includes an outer casing and a shock-absorbing and heat-insulating screen. The central body assembly includes an inner casing, a central cone located inside the inner casing, a rectifier support plate located between the inner casing and the central cone, an outer cavity stabilizer, and a central cavity stabilizer. The outer cavity stabilizer and the central cavity stabilizer are located at the rear end of the rectifier support plate. The outer cavity stabilizer forms a protrusion from the inner casing to the outer casing. The central cavity stabilizer is an annular cavity disposed on the central cone. The rectifier support plate includes a plurality of direct current blades and a plurality of swirling blades, which are arranged sequentially from the inside to the outside.

[0007] The oil circuit assembly includes a main flow injection ring located within the rectifier support plate, an outer cavity injection hole located on the wall of the outer cavity stabilizer, and a central cavity injection hole located on the wall of the central cavity stabilizer.

[0008] Furthermore, the DC blades and swirl blades are evenly arranged in the circumferential direction. The rectifier support plate includes an inner ring DC blade, an inner ring swirl blade, an outer ring swirl blade, and an outer ring DC blade arranged sequentially from the inside to the outside. The inner ring DC blade, the inner ring swirl blade, the outer ring swirl blade, and the outer ring DC blade are connected by an annular connecting plate, which divides the cross-sectional area of ​​the combustion chamber inlet into four equal parts.

[0009] Furthermore, the inlet angles of the inner ring DC blade, inner ring swirl blade, outer ring swirl blade, and outer ring DC blade are 10-20°; the outlet angles of the outer ring DC blade and inner ring DC blade are 0°; and the outlet angles of the outer ring swirl blade and inner ring swirl blade are 8-35°.

[0010] Furthermore, the external concave cavity stabilizer includes a front wall surface, a cavity surface, and a rear wall surface. The leftmost starting position of the front wall surface is aligned axially with the leftmost starting position of the central cavity front wall surface, forming an acute angle in the axial direction. The cavity surface is connected to the rear end of the front wall surface and is parallel to the outer casing. The rear wall surface is connected to the rear end of the cavity surface and is perpendicular to the cavity surface. The rear wall surface is connected to the shock-absorbing and heat-insulating screen. The leading edge angle of the front wall surface is 30-60°; the length-to-depth ratio of the external concave cavity stabilizer is 2-5.

[0011] Furthermore, the central cavity stabilizer includes a central cavity front wall surface, a central cavity cavity surface, and a central cavity rear wall surface connected in sequence. The central cavity cavity surface is parallel to the outer casing. Both the central cavity front wall surface and the central cavity rear wall surface are perpendicular to the central cavity cavity surface. The central cavity front wall surface is aligned axially with the leftmost starting position of the outer cavity front wall surface, and the central cavity rear wall surface is aligned axially with the outer cavity rear wall surface. The ratio of the axial length to the radial depth of the central cavity stabilizer is 2-4.

[0012] Furthermore, the central body assembly also includes a drainage pipe, which includes an air inlet, a radial section, and an air outlet connected in sequence. The radial section of the drainage pipe is located inside the rectifier support plate, the air inlet of the drainage pipe faces the external duct, and the air outlet of the drainage pipe is located on the front wall of the central cavity.

[0013] Furthermore, the main injection ring includes an oil inlet pipe and an injection ring, the injection ring being located at or behind the blade throat; the injection ring includes three rings arranged from the inside out, the three rings coinciding with three connecting plates respectively, each ring having several injection holes evenly arranged in the circumferential direction, the oil inlet pipe extending from the innermost ring of the injection ring to the outside of the outer casing, and communicating with all three rings of the injection ring.

[0014] Beneficial effects: Compared with the prior art, the significant advantages of this invention are: (1) By cooperating with the outer concave cavity stabilizer, the central concave cavity stabilizer and the rectifier support plate with partial swirl, the radial propagation of the concave cavity flame is completed by centrifugal force, which solves the problem of difficult flame connection in the circumferential direction of the traditional radial stabilizer and realizes flame connection on the entire cross section of the combustion chamber. At the same time, it makes the overall structure more compact, improves the thrust-to-weight ratio and improves the overall performance. (2) The dual-shift ignition of the outer concave cavity and the central concave cavity solves the problem of insufficient radial flame transmission depth when only the outer concave cavity is used for shift ignition in the swirling afterburner, so that the radial and circumferential flame transmission performance of the combustion chamber can achieve better results. (3) The central enhanced shift jet is set up to introduce air with a higher oxygen content into the central concave cavity from the outer bypass duct in the form of a jet, which helps to mix the oil mist, supplement oxygen and promote radial flame transmission, improves the problem of the central flame transmission depth being affected by the low oxygen content in the central part of the swirling afterburner, and improves the combustion efficiency. (4) By placing the main fuel injection ring at the blade throat, the fuel droplets can evaporate and mix between the blades earlier under high-temperature incoming flow, which greatly shortens the fuel mist mixing distance and further shortens the combustion chamber length, resulting in a more compact structure. At the same time, the evaporation of fuel mist between the blades can cool the blades and has a certain protective effect on the blade material. Attached Figure Description

[0015] Figure 1 This is a three-dimensional structural diagram of the combustion chamber of the present invention;

[0016] Figure 2 This is a schematic diagram of the longitudinal half-section three-dimensional structure of the combustion chamber of the present invention;

[0017] Figure 3 This is a schematic diagram of the inner and outer annular swirl flow and the DC blades of the present invention;

[0018] Figure 4 This is a schematic diagram of the rectifier support plate structure of the present invention;

[0019] Figure 5 This is a schematic diagram of the mainstream fuel injection ring structure of this invention;

[0020] Figure 6 This is a cold-state flow field streamline diagram of the present invention;

[0021] Figure 7 This is a contour plot of the tangential velocity of the present invention; Detailed Implementation

[0022] like Figure 1 and Figure 2 As shown, this embodiment of a locally swirling afterburner includes an outer cylinder assembly, a central body assembly, and an oil circuit assembly. The outer cylinder assembly includes an outer casing 1 and a shock-absorbing and heat-insulating screen 9; the central body assembly includes an inner casing 10, a rectifier support plate 4, an outer cavity stabilizer 2, a central cavity stabilizer 3, and a flow guide pipe 6; the oil circuit assembly includes a main flow injection ring 5, an outer cavity injection hole 7, and a central cavity injection hole 8.

[0023] The external concave cavity stabilizer 2 is located at the rear end of the rectifier branch plate 4. The external concave cavity stabilizer 2 forms a protrusion from the inner casing 10 toward the outer casing 1. The external concave cavity stabilizer 2 includes an external concave cavity front wall surface, an external concave cavity surface, and an external concave cavity rear wall surface. The leftmost starting position of the external concave cavity front wall surface is aligned with the leftmost starting position of the central concave cavity front wall surface in the axial direction and forms an acute angle in the axial direction. The front edge angle of the external concave cavity front wall surface is 60°. The external concave cavity surface is connected to the rear end of the external concave cavity front wall surface and is arranged parallel to the outer casing. The external concave cavity rear wall surface is connected to the rear end of the external concave cavity surface and is perpendicular to the external concave cavity surface. The external concave cavity rear wall surface is connected to the shockproof and heat insulation screen. The external concave cavity front wall surface is provided with an external concave cavity oil injection hole 7.

[0024] The central cavity stabilizer 3 is located at the rear end of the rectifier branch plate 4 and includes a central cavity front wall surface, a central cavity cavity surface, and a central cavity rear wall surface connected in sequence. The central cavity cavity surface is arranged parallel to the outer casing 1. The central cavity front wall surface and the central cavity rear wall surface are both perpendicular to the central cavity cavity surface. The central cavity front wall surface is aligned with the leftmost starting position of the outer cavity front wall surface in the axial direction. The central cavity rear wall surface is aligned with the outer cavity rear wall surface in the axial direction. The central cavity cavity surface is provided with a central cavity oil injection hole 8.

[0025] like Figure 3 and Figure 4As shown, the rectifier support plate 4 includes, from the inside out, an inner ring DC blade 44, an inner ring swirl blade 43, an outer ring swirl blade 42, and an outer ring DC blade 41. These blades are connected by an annular connecting plate, which divides the combustion chamber inlet cross-sectional area into four equal parts. In this embodiment, the outer ring blades 41 and 42, and the inner ring blades 43 and 44 are distributed at 22.5° intervals in the circumferential direction, for a total of 16 blades. The outlet and inlet of each corresponding inner ring DC blade 441, inner ring swirl blade 431, outer ring swirl blade 421, and outer ring DC blade 411 are located on the same diameter of the combustion chamber inlet cross-section. The inlet angle of the outer and inner ring blades is 20°; the thickness of the outer and inner ring blades is 3 mm. The outer ring swirl blade 42 has an outlet angle of 35°, the inner ring swirl blade 43 has an outlet angle of 20°, and the outer ring DC blade 41 and the inner ring DC blade 44 have an outlet angle of 0°.

[0026] like Figure 5 As shown, the main injection ring 5 includes an inlet pipe 51 and an injection ring 52. The injection ring 52 is located at or behind the blade throat. The injection ring 52 includes three rings arranged from the inside out, each ring coinciding with one of the three connecting plates. Each ring has several injection holes evenly arranged in the circumferential direction. The inlet pipe 51 extends from the innermost ring of the injection ring 52 to the outside of the outer casing and communicates with all three rings of the injection ring 52. It is located inside the blade within the inner casing. In this embodiment, the injection ring is located axially at the narrowest point of the blade throat.

[0027] The central body assembly also includes a drainage pipe 6, which includes an air inlet, a radial section and an air outlet connected in sequence. The radial section of the drainage pipe is located inside the rectifier support plate. The air inlet of the drainage pipe is facing the external duct, and the air outlet of the drainage pipe is located on the front wall of the central cavity.

[0028] High-temperature combustion gas enters the combustion chamber through the inlet of casing 10. After passing through the rectifier plate 4 and the outer ring direct current blades 41, it forms an outer ring axial flow 11. This flow then passes through the inner ring direct current blades 44 to form an inner ring axial flow 12, and finally passes through the two intermediate layers of inner and outer ring swirling blades to form a swirling flow 13. The inner and outer ring axial flows 11 and 12 act as a barrier to the swirling flow 13, ensuring that the gas on the central cone surface and near the upper wall of the inner casing does not separate. The gas then passes through a fuel injection ring device located at the blade throat. Each layer of the fuel injection ring has eight injection holes evenly distributed circumferentially. Under the high-temperature gas flow, the fuel evaporates at the blade throat, cooling the trailing section of the blade. Furthermore, the strong swirling flow behind the blade utilizes the difference in centrifugal force on oil droplets of different sizes to achieve a reasonable radial distribution of the fuel, thus achieving a uniform and rational fuel distribution. By matching the distance between the inner ring and the inner casing, the distance between the outer ring and the outer casing, and the angle of the blades, the fluid distribution pattern of the axial flow passing through the swirl blades can be adjusted, controlling the ratio of swirling to axial flow, thereby achieving the regulation of the centrifugal force field within the combustion chamber. Figure 6 As shown. Unlike the mechanism by which conventional swirling combustion chambers form an axial low-speed recirculation zone to stabilize the flame, in this invention, the swirling effect is to generate a centrifugal force field to accelerate the radial propagation of the flame.

[0029] The incoming flow passes through the central cone and the splitter plate to form a diffuser section. In this embodiment, the equivalent expansion angle of the central cone is about 15°. Under the premise of avoiding separation when the airflow flows along the cone surface, the airflow is diffused and decelerated by using a shorter axial length of the combustion chamber. A reasonable low-speed recirculation zone is formed in the central cavity, and a stable central cavity flame is formed with lower flow loss.

[0030] The oil-gas mixture then passes through a swirling cavity formed between the external concave flame stabilizer, the shock-absorbing heat shield, and the central cone. This swirling cavity is located behind the diffuser section. Figure 7 As shown, in this example, the incoming flow of 50 m / s, under the action of the swirl blades at 20° and 35°, forms a hypergravity region with a maximum tangential velocity of 30 m / s. This creates a centrifugal acceleration of 2000g~3000g within the swirl chamber, and a centrifugal acceleration of 1000g~1500g in the region near the center behind the central cone. The centrifugal force and thermal buoyancy generated by the swirl enhance the mixing between the hot and cold fluids, intensify the wrinkling of the outer concave cavity flame surface, increase the flame surface area and heat release rate, and accelerate the concave cavity flame to propagate radially towards the center of the combustion chamber, connecting with the truncated cone flame to achieve flame fusion across the entire combustion chamber cross-section. This ensures combustion stability and improves combustion efficiency. The swirl ratio generated by the outer concave cavity flame stabilizer and the swirl device is matched, allowing the swirl to dissipate significantly at the combustion chamber outlet, avoiding excessive airflow rotation angle in the tailpipe and preventing additional thrust loss.

[0031] When the oil-gas mixture passes through the central cavity, it forms a low-speed, stable reflux zone. Under the action of the outer bypass gas jet ejected from the drainage pipe, the mixing of oil and gas is accelerated, the local oxygen content in the central cavity is increased, and the central duty flame is helped to propagate outward radially, thus mitigating the adverse effects of centrifugal force on the flame in the central cavity.

[0032] This embodiment achieves rapid propagation and flame stabilization of the ignition source within the swirling cavity through the coordination of the external concave cavity flame stabilizer, the rectifier support plate swirl blades, the central concave cavity, the fuel injection ring device at the blade throat, and the central duty enhanced jet. This can significantly reduce the use of conventional radial or circumferential flame stabilizers and reduce combustion chamber resistance loss.

[0033] This embodiment utilizes the strong centrifugal effect generated by the swirling flow to accelerate flame propagation and enhance fuel-air mixing. It reduces the use of radial stabilizers in conventional integrated rear frame designs, improving combustion efficiency while ensuring combustion stability and total pressure loss in the combustion chamber. It also shortens the combustion chamber length, widens the ignition threshold, reduces the difficulty of wall cooling, and achieves a uniform and reasonable distribution of combustion chamber outlet temperature. Furthermore, the fuel injection design utilizes a high-temperature inflow to pre-evaporate fuel droplets at the blade throat, which not only shortens the fuel mist evaporation distance and makes the overall combustion chamber structure more compact, but also cools the rear end of the blades. The central concave cavity replaces the traditional truncated cone, ensuring the aerodynamic stealth performance of the combustion chamber. The central enhanced standby jet within the central concave cavity accelerates fuel-air mixing and flame propagation, compensating for the drawbacks of strong swirling flow in suppressing central flame propagation.

Claims

1. A local swirl afterburner comprising an outer barrel assembly, a center body assembly and an oil path assembly, the outer barrel assembly comprising an outer casing (1) and a shock absorbing heat shield (9), characterized in that, The central body assembly includes an inner casing (10), a central cone located inside the inner casing (10), a rectifier support plate (4) located between the inner casing (10) and the central cone, an outer cavity stabilizer (2), and a central cavity stabilizer (3). The outer cavity stabilizer (2) and the central cavity stabilizer (3) are located at the rear end of the rectifier support plate (4). The outer cavity stabilizer (2) forms a protrusion from the inner casing (10) toward the outer casing (1). The central cavity stabilizer (3) is an annular cavity set on the central cone. The rectifier support plate (4) includes an inner ring DC blade (44), an inner ring swirl blade (43), an outer ring swirl blade (42), and an outer ring DC blade (41) arranged sequentially from the inside to the outside. The inner ring DC blade (44), the inner ring swirl blade (43), the outer ring swirl blade (42), and the outer ring DC blade (41) are connected by an annular connecting plate. The connecting plate divides the cross-sectional area of ​​the combustion chamber inlet into four equal parts. The oil circuit assembly includes a main flow injection ring located in the rectifier branch plate (4), an outer cavity injection hole located on the wall of the outer cavity stabilizer (2), and a central cavity injection hole located on the wall of the central cavity stabilizer (3).

2. The stressed combustor of claim 1 wherein, The DC blades and swirl blades are evenly arranged in the circumferential direction.

3. The stressed combustor of claim 2 wherein, The inlet angles of the inner ring DC blade (44), inner ring swirl blade (43), outer ring swirl blade (42), and outer ring DC blade (41) are 10-20°; the outlet angles of the outer ring DC blade (41) and inner ring DC blade (44) are 0°; and the outlet angles of the outer ring swirl blade (42) and inner ring swirl blade (43) are 8-35°.

4. The stressed combustor of claim 1 wherein, The concave cavity stabilizer (2) includes a front wall surface of the concave cavity, a cavity surface of the concave cavity, and a rear wall surface of the concave cavity. The leftmost starting position of the front wall surface of the concave cavity is aligned with the leftmost starting position of the front wall surface of the central cavity in the axial direction and forms an acute angle in the axial direction. The cavity surface of the concave cavity is connected to the rear end of the front wall surface of the concave cavity and is arranged parallel to the outer casing. The rear wall surface of the concave cavity is connected to the rear end of the cavity surface of the concave cavity and is perpendicular to the cavity surface of the concave cavity. The rear wall surface of the concave cavity is connected to the shockproof and heat-insulating screen.

5. The stressed combustor of claim 4 wherein, The leading edge angle of the front wall of the concave cavity is 30-60°; the length-to-depth ratio of the concave cavity stabilizer (2) is 2-5.

6. The afterburner according to claim 4, characterized in that, The central cavity stabilizer (3) includes a central cavity front wall surface, a central cavity cavity surface, and a central cavity rear wall surface connected in sequence. The central cavity cavity surface is arranged parallel to the outer casing. The central cavity front wall surface and the central cavity rear wall surface are both perpendicular to the central cavity cavity surface. The central cavity front wall surface is aligned with the leftmost starting position of the outer cavity front wall surface in the axial direction. The central cavity rear wall surface is aligned with the outer cavity rear wall surface in the axial direction.

7. The afterburner according to claim 6, characterized in that, The ratio of the axial length to the radial depth of the central cavity stabilizer (3) is 2-4.

8. The afterburner according to claim 1, characterized in that, The central body assembly also includes a drainage pipe (6), which includes an air inlet, a radial section and an air outlet connected in sequence. The radial section of the drainage pipe is located inside the rectifier support plate. The air inlet of the drainage pipe is facing the external duct, and the air outlet of the drainage pipe is located on the front wall of the central cavity.

9. The afterburner according to claim 2, characterized in that, The main injection ring (5) includes an oil inlet pipe (51) and an injection ring (52). The injection ring (52) is located at or behind the blade throat. The injection ring (52) includes three rings arranged from the inside to the outside. The three rings coincide with three connecting plates respectively. Each ring is evenly provided with several injection holes in the circumferential direction. The oil inlet pipe (51) extends from the innermost ring of the injection ring (52) to the outside of the outer casing and is connected to all three rings of the injection ring (52).

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