A supercritical kerosene based anti-coking, low pluggage ratio augmented combustor

Abstract

The application discloses a supercritical kerosene-based anti-coking and low-blockage-ratio afterburner, and relates to the technical field of aero-engines.The supercritical kerosene-based anti-coking and low-blockage-ratio afterburner comprises a nitrogen pipeline, a normal-temperature oil circuit, a preheating oil circuit, a supercritical kerosene oil supply device formed by an afterburner oil supply circuit and a backflow oil circuit, and the like; and the afterburner is composed of an outer duct, an inner duct, a pressure atomizing nozzle, a direct injection nozzle, a center cone, an oil pipe heat insulation protective sleeve, a first kerosene superheater, a second kerosene superheater and a cavity.The application has the advantages of small flow resistance loss and no additional shaft power consumption by using supercritical kerosene jets to replace blunt body flame stabilizers and aerodynamic flame stabilizers; the mixing effect and combustion efficiency of fuel can be effectively improved by using supercritical kerosene as fuel; and the short board of easy coking of supercritical kerosene is made up by oxygen removal, superheat adjustment, nitrogen purging and the like.

Description

Technical Field

[0001] This invention relates to the field of aero-engine technology, specifically to an afterburner based on supercritical kerosene that is coking-resistant and has a low blockage ratio. Background Technology

[0002] Afterburners are typically located between the turbine and exhaust nozzle of military aircraft engines. Their working principle involves injecting fuel again after the turbine, significantly increasing the temperature and exhaust velocity of the combustion gases, thereby improving the engine's specific thrust and total thrust. The afterburner operates in an environment characterized by high temperature, high flow velocity, low pressure, and low oxygen content. Except for the high temperature, the other three conditions are unfavorable for combustion, resulting in relatively low combustion efficiency. Even with increased combustion chamber size, the efficiency is generally below 90%. Furthermore, the afterburner remains in a non-ignited state for most of the engine's operation. Its complex internal structure, including fuel injectors and flame stabilizers, along with its long combustion chamber walls, contributes to significant flow resistance losses, reducing the engine's fuel economy during cruise.

[0003] In terms of combustion organization and flame stabilization in afterburners, three types of flame stabilizers are most commonly used: blunt-body flame stabilizers, pneumatic flame stabilizers, and standby flame stabilizers. The principle of a pneumatic flame stabilizer is to first draw air from the compressor, then inject a high-speed jet of air laterally or against the main flow direction in the afterburner. After the jet interacts with the main flow, it is deflected and forms a recirculation zone. Within this recirculation zone, there are always some low-velocity areas where the airflow velocity is exactly equal to the flame propagation velocity under that operating condition, thus stabilizing the flame. Compared to blunt-body and standby flame stabilizers, pneumatic flame stabilizers have advantages such as lower flow resistance loss in non-afterburning conditions, adjustability, and less erosion due to not directly contacting the flame surface. However, they also consume approximately 2% of the total main flow rate of compressor bleed air, which diverts a portion of the compressed air originally used for film cooling, leading to a deterioration in overall engine performance.

[0004] Supercritical state is a special fluid state, distinct from the common solid, liquid, and gas phases, and possesses unique physical properties. For aviation kerosene, when the pressure and temperature simultaneously exceed its critical pressure (approximately 2.4 MPa) and critical temperature (approximately 380°C), it transforms into a supercritical state, exhibiting both the high density of liquid fuels and the easily miscible characteristics of gaseous fuels. Therefore, according to combustion theory, replacing traditional room-temperature kerosene with supercritical kerosene can improve combustion efficiency, shorten combustion reaction time, and maintain flame stability at higher flow velocities. However, because supercritical kerosene needs to be heated to temperatures above 380°C, the potential for kerosene cracking, oxidation, and coking at high temperatures must be considered, which can easily lead to fuel line blockage. The coking mechanism of supercritical kerosene can be divided into the following three points: 1. Cracking in an oxygen-free environment: When the oil temperature is near the critical temperature and the environment is oxygen-free, the kerosene will slowly crack into small molecule olefins. This process will only produce a very small amount of carbon deposits. 2. Oxidation in an oxygen-containing environment: When the oil temperature is near the critical temperature and the environment contains oxygen, the kerosene will slowly oxidize to produce carbon monoxide, carbon dioxide, peroxides, and a small amount of carbon deposits. 3. Carbonization at high temperature: When supercritical kerosene has a high degree of superheat (i.e., the temperature difference between the current oil temperature and the critical temperature), the kerosene will rapidly decompose to produce hydrogen, methane, and elemental carbon. This process produces the most carbon deposits. Summary of the Invention

[0005] The purpose of this invention is to provide an anti-coking, low-blockage-ratio afterburner based on supercritical kerosene, which can not only solve the problems of low combustion efficiency and large flow resistance loss in non-ignition state in existing afterburners, but also improve the shortcoming of supercritical kerosene being prone to coking at high temperatures.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a supercritical kerosene-based anti-coking, low-blockage ratio afterburner, characterized in that: it includes a main oil tank, which is installed inside the wing and has a pipeline leading to the inlet pipe of the oil pump. The outlet pipe of the oil pump is connected to a check valve via a pipeline. The outlet end of the check valve is connected to a reserve oil tank via a pipeline after passing through a kerosene filter deaerator. The reserve oil tank has three pipelines. Except for one connected to the aforementioned check valve, the other two are respectively connected to the inlet of a centrifugal oil pump and the outlet of a kerosene cooler. The outlet of the centrifugal oil pump is connected to a pipeline, which then branches into two lines and is named the ambient temperature oil line and the preheating oil line, respectively. The preheating oil line passes through a preheating oil line solenoid valve and a kerosene preheater in sequence, and finally leads to the kerosene mixer. The ambient temperature oil line is equipped with an ambient temperature oil line solenoid valve and also leads to the kerosene mixer. The kerosene mixer is connected to four oil circuits. In addition to the aforementioned ambient temperature oil circuit and preheating oil circuit, it also has an afterburner supply oil circuit and a return oil circuit. The afterburner supply oil circuit is connected to a first pneumatic valve, the outlet of which is connected to the afterburner. The return oil circuit first passes through a throttle valve and then branches, one end connecting to an exhaust valve, and the other end connecting to the inlet of the kerosene cooler via a second pneumatic valve. A nitrogen pipeline is inserted into the preheating oil circuit between the preheating oil circuit solenoid valve and the kerosene preheater. One end of the nitrogen pipeline is connected to the preheating oil circuit, and the other end is connected to a high-pressure nitrogen tank. A nitrogen pipeline solenoid valve is also connected to the middle section of the nitrogen pipeline.

[0007] Furthermore, the afterburner structure includes a central cone. Two layers of cylindrical bodies are coaxially fitted around the central cone, dividing the flow channel into an inner duct and an outer bypass duct. The cross-sections of the inner and outer bypass ducts are concentric circles. The left side of the inner duct connects to the turbine and the main combustion chamber, while the left side of the outer bypass duct is the outer bypass duct of the turbofan engine. The length of the inner cylindrical body is less than the length of the central cone, and the length of the central cone is less than the length of the outer cylindrical body. Additionally, an inner and outer bypass mixer is connected to the right end of the inner cylindrical body. A ring of pressure atomizing nozzles is radially arranged on the outer surface of the central cone at the inlet position of the inner duct, and a ring of direct-injection nozzles is radially arranged on the outer surface of the central cone at the right side position of the inner and outer bypass mixer. A recessed cavity is formed on the right side of each direct-injection nozzle. The above-mentioned afterburner oil supply line penetrates the outer cylinder and enters the afterburner, extending into the central cone. Subsequently, the afterburner oil supply line branches into two paths: one path goes to the left into the first kerosene superheater and then to the pressure atomizing nozzle; the other path goes to the right into the second kerosene superheater and then to the direct injection nozzle.

[0008] Furthermore, the first and second kerosene superheaters are annular structures, installed inside the central cone and closely attached to its inner surface. The first kerosene superheater is installed between the pressure atomizing nozzle and the direct-fire nozzle; the second kerosene superheater is installed between the right side of the recess and the tip of the central cone. Even further, the effective heat exchange area of ​​the second kerosene superheater is smaller than that of the first kerosene superheater.

[0009] Furthermore, the fuel supply circuit of the afterburner is equipped with a heat-insulating protective sleeve on the outside of the pipeline between the central cone and the outer cylinder of the afterburner.

[0010] Furthermore, the cavity includes a room-temperature kerosene nozzle and a spark plug.

[0011] Furthermore, the spray direction of the direct-fire nozzle is perpendicular to the mainstream direction or at a 30° or 45° angle to the mainstream direction. Even further, it is preferable that the direct-fire nozzle sprays at a 45° angle to the mainstream direction.

[0012] Furthermore, the kerosene preheater can be placed at the inlet of the main combustion chamber at the compressor outlet, or inside the compressor's cooling gas pipeline, allowing it to exchange heat with the hot air compressed by the compressor. The kerosene preheater comprises multiple heat exchanger modules, each including a three-way valve. This three-way valve is a T-type confluence three-way valve (with two inlets and one outlet). A branch pipe from the first kerosene pipeline leads to one inlet of the three-way valve; similarly, a branch pipe from the nitrogen pipeline leads to the other inlet of the three-way valve. The outlet of the three-way valve is connected to the heat exchanger via a pipeline, and the other end of the heat exchanger leads to a dedicated one-way valve, which then extends and merges into the second kerosene pipeline. Even further, the three-way valve and the dedicated one-way valve must be located away from high-heat-load areas surrounding the heat exchanger.

[0013] Furthermore, the first and second kerosene superheaters can also adopt the same structure as the kerosene preheater described above.

[0014] Furthermore, the interior of the kerosene filter deaerator is divided into two cavities by a perforated plate. The cavity on the left side of the perforated plate is filled with a deaerator, and an outlet is provided at its lower part. Alternating partitions are arranged in the cavity on the right side of the perforated plate, with a hexagonal metal mesh sandwiched between the partitions. The hexagonal metal mesh is located at the bottom of the cavity. A gas collecting pipe is provided near the top of each pair of partitions. These gas collecting pipes extend to the outside of the kerosene filter deaerator and converge into a single gas collecting pipe leading to an oil-gas separator. The oil-gas separator is connected to a dedicated exhaust valve for the kerosene filter deaerator via a pipeline. An inlet is located at the rightmost end of the kerosene filter deaerator, and this inlet communicates with the cavity on the right side of the perforated plate. Furthermore, the deaerator is a composite material composed of a porous medium and active metal powder. The porous medium is preferably sponge copper, and the active metal powder is preferably aluminum powder or active iron powder.

[0015] Furthermore, the kerosene cooler is installed inside the wing at the rear upper position.

[0016] Furthermore, a metal diaphragm is installed inside the preparatory oil tank. The metal diaphragm is elastic and divides the preparatory oil tank into two areas. One area of ​​the preparatory oil tank is filled with kerosene, and its corresponding outer shell is connected to the three pipelines mentioned above, such as the return oil circuit. The air in the other area is connected to the outside through a connecting pipe inserted into the outer shell.

[0017] Furthermore, the kerosene mixer has a cylindrical upper end and a funnel-shaped lower end, and is hollow inside. The cylindrical top surface of the kerosene mixer is connected to the ambient temperature oil circuit, and the funnel-shaped bottom surface is connected to the fuel supply circuit for the afterburner. A preheating oil circuit is connected to the cylindrical side of the kerosene mixer, and the connection position of the preheating oil circuit is located on one side of the kerosene mixer and is tangent to the cylindrical side of the kerosene mixer. A return oil circuit is connected to the center of the funnel-shaped side of the kerosene mixer.

[0018] Furthermore, the inner and outer duct mixer is selected from one of the following: ring mixer, funnel-shaped mixer, chrysanthemum-shaped mixer, and finger-shaped mixer, with the chrysanthemum-shaped mixer being preferred.

[0019] Furthermore, the first pneumatic valve, the second pneumatic valve, the exhaust valve, and all types of solenoid valves are normally closed valves, except for the exhaust valve for the kerosene filter deaerator, which is a normally open valve.

[0020] Compared with existing technologies, the beneficial effects of the supercritical kerosene-based anti-coking and low-blockage ratio afterburner provided by this invention include:

[0021] 1. This invention heats kerosene to a subcritical state through a preheating oil circuit, a kerosene preheater, and heat exchange with the compressor bleed air. Then, through a first and second kerosene superheater and heat exchange with the afterburner, the kerosene is further heated to a supercritical state. Supercritical kerosene has advantages such as easier ignition, better air mixing, faster combustion reaction, and higher combustion efficiency. Therefore, using supercritical kerosene as fuel can improve the thermal efficiency of aero-engines, reduce the size of the afterburner, and increase the thrust-to-weight ratio of aero-engines. Furthermore, the heat absorbed during the heating process of the kerosene can pre-cool the compressor bleed air used for film cooling and cool the surface of the central cone of the afterburner, effectively reducing the temperature of various components within the combustion chamber and extending their service life.

[0022] 2. This invention replaces the bluff flame stabilizer or pneumatic flame stabilizer in a traditional afterburner with a direct-injection nozzle. The principle is that the high-speed supercritical kerosene jet interacts with the mainstream to create a recirculation zone, achieving flame stabilization. Compared to traditional bluff flame stabilizers, it has the advantage of lower flow resistance loss. Furthermore, compared to pneumatic flame stabilizers, the supercritical kerosene injection energy primarily comes from waste heat generated by engine cooling, and the injected supercritical kerosene itself can be used as fuel, eliminating waste. Therefore, this invention eliminates the need to extract compressed air from the compressor for injection, reducing the shaft work done by the compressor and improving engine thermal efficiency.

[0023] 3. This invention innovatively suppresses coking of supercritical kerosene through five methods: First, removing air bubbles and dissolved oxygen from the kerosene through a kerosene filter deaerator, thus inhibiting coking caused by the high-temperature reaction between kerosene and air; Second, employing a two-stage heating method using a kerosene preheater and a first kerosene superheater (second kerosene superheater), shortening the residence time of kerosene at supercritical temperature, thereby slowing down the coking rate in the pipeline; Third, the kerosene mixer and modular heat exchanger can adjust the superheat of the supercritical kerosene, preventing carbonization due to excessive superheat; Fourth, when the booster combustion chamber is shut down, nitrogen is used as a purging gas to purge the oil supply pipeline, allowing the kerosene adhering to the inner surface of the pipeline to vaporize and be discharged from the pipeline, ensuring pipeline cleanliness and preventing the formation of black viscous tar on the inner wall of the pipeline, which would affect subsequent kerosene flow; Fifth, when a certain number of heat exchanger modules are shut down, nitrogen is used to fill their interiors to prevent residual kerosene from being repeatedly heated in the heat exchanger for a long time, causing coking and clogging of the heat exchanger pipeline. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0025] Figure 2 In this invention Figure 1 Enlarged cross-sectional view of section A (afterburner);

[0026] Figure 3 In this invention Figure 2 Enlarged structural diagram of section C (concave cavity);

[0027] Figure 4 In this invention Figure 1 Enlarged cross-sectional view of section B (kerosene preheater);

[0028] Figure 5 This is a schematic cross-sectional view of the kerosene filter deaerator in this invention;

[0029] Figure 6 This is a schematic diagram of the wing cross-section in this invention;

[0030] Figure 7This is a schematic cross-sectional view of the pre-existing fuel tank in this invention;

[0031] Figure 8 This is a schematic diagram of the kerosene mixer structure in this invention;

[0032] Figure 9 This is a diagram illustrating the effect of a single heat exchanger module in operation according to the present invention;

[0033] Figure 10 This is a diagram showing the effect of a single heat exchanger module being shut down (filled with nitrogen) in this invention;

[0034] Figure 11 This is a schematic diagram of the kerosene preheater structure in Embodiment 1 of the present invention;

[0035] Figure 12 This is a schematic diagram of the structure of the first kerosene superheater / second kerosene superheater in Embodiment 1 of the present invention;

[0036] Figure 13 This is a streamline and oil and gas distribution cloud map on the axial section in the comparative example of this invention;

[0037] Figure 14 This is a streamline and oil and gas distribution cloud map on the axial section in Embodiment 1 of the present invention;

[0038] Figure 15 This is a streamline and oil and gas distribution cloud map on the axial section in Embodiment 2 of the present invention;

[0039] Figure 16 This is a streamline and oil and gas distribution cloud map on the axial section in Embodiment 3 of the present invention;

[0040] Figure 17 This is a streamline and oil and gas distribution cloud map on the axial section in Embodiment 4 of the present invention;

[0041] Figure 18 This is a streamline and oil and gas distribution cloud map on the axial section in Embodiment 5 of the present invention;

[0042] In the diagram: 11. Main oil tank; 12. Reserve oil tank; 121. Metal diaphragm; 122. Connecting pipe; 13. High-pressure nitrogen tank; 14. Centrifugal oil pump; 15. Oil transfer pump; 16. Kerosene mixer; 17. Wing; 18. Kerosene preheater; 19. Kerosene cooler; 21. Check valve; 22. Nitrogen pipeline solenoid valve; 23. Preheating oil circuit solenoid valve; 24. Normal temperature oil circuit solenoid valve; 25. First pneumatic valve; 26. Throttle valve; 27. Exhaust valve; 28. Second pneumatic valve; 3. Kerosene filter deaerator; 31. Inlet; 32. Outlet; 33. Baffle plate; 34. Orifice plate; 35. Deaerator; 36. Hexagonal metal mesh; 37. Gas collecting pipe; 38. Oil-gas separator; 39. Kerosene filter deaerator exhaust valve; 41. Nitrogen pipeline; 42. Normal temperature oil pipeline; 43. Preheating oil pipeline; 44. Afterburner fuel supply pipeline; 45. Return oil pipeline; 5. Afterburner; 51. Outer duct; 52. Inner duct; 53. Pressure atomizing nozzle; 54. Direct injection nozzle; 55. Inner and outer duct mixer; 56. Center cone; 57. Oil pipe heat insulation sleeve; 581. First kerosene superheater; 582. Second kerosene superheater; 59. Cavity; 591. Normal temperature kerosene nozzle; 592. Spark plug; 61. First kerosene pipeline; 62. Second kerosene pipeline; 63. Nitrogen pipeline; 64. Three-way valve; 65. Heat exchanger check valve; 66. Heat exchanger. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] In the description of the invention, it should be noted that the terms "vertical," "upper," "lower," "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the invention.

[0045] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a connection via a pipe, or an electrical connection; they can refer to a direct connection or an indirect connection via an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0046] Please refer to Figure 1 A coking-resistant, low-blockage afterburner based on supercritical kerosene is characterized by comprising a main fuel tank 11, which is located inside the wing 17 and has a pipeline leading to the inlet pipe of a fuel pump 15. The outlet pipe of the fuel pump 15 is connected to a check valve 21 via a pipeline. The outlet end of the check valve 21 is connected to a reserve fuel tank 12 via a pipeline after passing through a kerosene filter deaerator 3. The reserve oil tank 12 is equipped with three pipelines. Except for one pipeline connected to the aforementioned check valve 21, the other two pipelines lead to the inlet of the centrifugal oil pump 14 and the outlet of the kerosene cooler 19, respectively. The outlet of the centrifugal oil pump 14 is connected to a pipeline, which then branches into two pipelines and is named the ambient temperature oil line 42 and the preheating oil line 43, respectively. The preheating oil line 43 passes through the preheating oil line solenoid valve 23 and the kerosene preheater 18 in sequence, and finally leads to the kerosene mixer 16. The ambient temperature oil line 42 is equipped with an ambient temperature oil line solenoid valve 24, which also leads to the kerosene mixer 16. The kerosene mixer 16 is connected to four oil lines. In addition to the ambient temperature oil line 42 and the preheating oil line 43, it also has a booster combustion chamber oil supply line 44 and a return oil line 45. The booster combustion chamber oil supply line 44 is connected to the first pneumatic valve 25, and the outlet end of the first pneumatic valve 25 is connected to the booster combustion chamber 5. The return oil line 45 first passes through the throttle valve 26, and then branches. One end is connected to the exhaust valve 27, and the other end passes through the second pneumatic valve 28 and is connected to the inlet of the kerosene cooler 19. A nitrogen pipeline 41 is inserted into the preheating oil line 43 between the preheating oil line solenoid valve 23 and the kerosene preheater 18. One end of the nitrogen pipeline 41 is connected to the preheating oil line 43, and the other end is connected to the high-pressure nitrogen tank 13. A nitrogen pipeline solenoid valve 22 is also connected to the middle section of the nitrogen pipeline 41.

[0047] The function of the oil transfer pump 15 is to transport aviation kerosene from the main fuel tank 11 to the reserve fuel tank 12. This process does not require very high oil pressure, so the oil transfer pump 15 with lower power is sufficient. The function of the centrifugal oil pump 14 is to pressurize the aviation kerosene to a supercritical pressure of more than 2.4 MPa, so a centrifugal pump with higher power and excellent pressurization capacity is used.

[0048] The function of check valve 21 is to allow aviation kerosene to flow only from the main fuel tank 11 to the reserve fuel tank 12, preventing the aviation kerosene in the reserve fuel tank 12 from flowing back into the main fuel tank 11. This is because some of the kerosene in the reserve fuel tank 12 is heated and then cooled for recovery. The recovered kerosene appears yellow or dark yellow, a darker color than unheated kerosene, because it contains a small amount of kerosene cracking products at high temperatures. Check valve 21 prevents these cracking products from contaminating the kerosene stored in the main fuel tank 11, and ensures that the kerosene is consumed preferentially during the next afterburner operation. Similarly, the dual-tank design of the main fuel tank 11 and the reserve fuel tank 12 is also to prevent the kerosene in the main fuel tank 11 from being contaminated.

[0049] The reason for using a first pneumatic valve 25 to control the fuel supply line 44 in the afterburner is that the kerosene in this line has been heated in the kerosene preheater 18, reaching a temperature of 200-350℃. Prolonged operation of the solenoid valve at this temperature would slowly demagnetize its magnet, shortening its lifespan and making it prone to damage. The pneumatic valve, however, does not contain electronic components and is remotely controlled by compressed air, enabling it to operate reliably at high temperatures for extended periods. Similarly, a second pneumatic valve 28 is used to control the return fuel line 45. Furthermore, the nitrogen line solenoid valve 22, the preheating fuel line solenoid valve 23, and the ambient temperature fuel line solenoid valve 24 all operate at ambient temperature, making solenoid valves advantageous for their convenient control and fast response.

[0050] The function of the throttle valve 26 is to regulate pressure, maintaining the kerosene pressure before the throttle valve 26 above 2.4 MPa, and rapidly reducing the pressure after the kerosene passes through the throttle valve 26. In this way, the return oil circuit 45, the kerosene cooler 19, and the reserve oil tank 12 after the throttle valve 26 can be regarded as unpressurized, thus allowing for the use of thinner walls and effectively reducing the system weight.

[0051] Please refer to Figure 2The afterburner structure 5 includes a central cone 56. Two cylindrical bodies coaxially surround the central cone 56, dividing the flow channel into an inner duct 52 and an outer bypass duct 51. The cross-sections of the inner and outer bypass ducts 52 are concentric circles. The left side of the inner duct 52 connects to the turbine and the main combustion chamber, while the left side of the outer bypass duct 51 is the outer bypass duct of the turbofan engine. The length of the inner cylindrical body is less than the length of the central cone 56, and the length of the central cone 56 is less than the length of the outer cylindrical body. Furthermore, an inner and outer bypass mixer 55 is connected to the right end of the inner cylindrical body. A ring of pressure atomizing nozzles 53 is radially arranged on the outer surface of the central cone 56 at the inlet position of the inner duct 52. A ring of direct-injection nozzles 54 is radially arranged on the outer surface of the central cone 56 at the right side position of the inner and outer bypass mixer 55. A recessed cavity 59 is opened on the right side of the direct-injection nozzles 54. The above-mentioned afterburner oil supply line 44 penetrates the outer cylinder and enters the afterburner 5, extending into the central cone 56. Subsequently, the afterburner oil supply line branches into two paths: one path goes to the left into the first kerosene superheater 581 and then to the pressure atomizing nozzle 53; the other path goes to the right into the second kerosene superheater 582 and then to the direct injection nozzle 54.

[0052] Furthermore, the first kerosene superheater 581 and the second kerosene superheater 582 are annular structures, installed inside the central cone 56 and closely attached to the inner surface of the central cone 56. The first kerosene superheater 581 is installed between the pressure atomizing nozzle 53 and the direct-fire nozzle 54; the second kerosene superheater 582 is installed between the right side of the recess 59 and the tip of the central cone 56. Even further, the effective heat exchange area of ​​the second kerosene superheater 582 is smaller than that of the first kerosene superheater 581.

[0053] Furthermore, the oil supply circuit 44 of the afterburner is fitted with an oil pipe heat insulation protective sleeve 57 on the outside of the pipe between the central cone 56 and the outer shell of the afterburner. The reasons for installing the oil pipe heat insulation protective sleeve 57 are: first, to protect the pipe between the central cone 56 and the outer shell of the afterburner and prevent its surface from being burned under the high temperature and high flow rate conditions of the afterburner; second, to insulate the oil supply circuit 44 of the afterburner and prevent the high temperature above 1300K in the afterburner from being conducted into the pipe and causing the kerosene to coke.

[0054] Furthermore, the direct-fire nozzle 54 is positioned perpendicular to the mainstream direction or at a 30° or 45° angle to the mainstream direction. More preferably, the direct-fire nozzle 54 sprays at a 45° angle to the mainstream direction. The direct-fire nozzle 54 acts as a pneumatic flame stabilizer, creating a recirculation zone through the interaction of the high-speed supercritical kerosene jet with the mainstream, which is beneficial for flame stability. Using a supercritical kerosene jet instead of the compressed air used in traditional pneumatic flame stabilizers saves compressor bleed air and reduces the shaft work done by the compressor.

[0055] Please refer to Figure 3The cavity 59 includes a room-temperature kerosene nozzle 591 and a spark plug 592. The function of the cavity 59 is to ignite the afterburner. During ignition, the airflow can form a local recirculation zone within the cavity 59, which facilitates the development and propagation of the initial flame nucleus formed by the spark plug 592. In addition, a small amount of liquid kerosene can be injected through the room-temperature kerosene nozzle 591 during ignition. Room-temperature kerosene is used here because the injection pressure of supercritical kerosene is as high as 2.4 MPa, which results in a supersonic injection velocity. On the one hand, the fuel residence time in the cavity is too short, and on the other hand, the high-speed injection of supercritical kerosene will extinguish the flame nucleus formed by the spark plug, both of which are unfavorable for ignition. In contrast, the injection velocity of room-temperature kerosene is usually only a few to tens of meters per second, which is conducive to ignition and flame propagation.

[0056] Furthermore, the kerosene preheater 18 can be placed at the inlet of the main combustion chamber at the compressor outlet, or inside the compressor's cooling gas pipeline, where it can exchange heat with the hot air compressed by the compressor. Please refer to [reference needed]. Figure 4 The kerosene preheater 18 includes multiple heat exchanger modules. Each heat exchanger module includes a three-way valve 64, which is a T-type confluence three-way valve (with two inlets and one outlet). A branch pipe from the first kerosene pipeline 61 leads to one inlet of the three-way valve 64; similarly, a branch pipe from the nitrogen pipeline 63 leads to the other inlet of the three-way valve 64. The outlet of the three-way valve 64 is connected to the heat exchanger 66 via a pipe. The other end of the heat exchanger 66 leads to a dedicated one-way valve 65 and then extends and merges into the second kerosene pipeline 62. Furthermore, the three-way valve 64 and the dedicated one-way valve 65 must be located away from the high heat load area around the heat exchanger 66. Figure 4 The area enclosed by the dotted line is to prevent the service life of the three-way valve 64 and the heat exchanger-specific check valve 65 from being shortened under the influence of high temperature.

[0057] Furthermore, the first kerosene superheater 61 and the second kerosene superheater 62 may also adopt the same structure as the kerosene preheater 18.

[0058] Please refer to Figure 5 The kerosene filter deaerator 3 is internally divided into two cavities by an orifice plate 34. The cavity on the left side of the orifice plate 34 is filled with deaerator 35, and has an outlet 32 ​​at its lower part. The cavity on the right side of the orifice plate 34 has alternating partitions 33, with hexagonal metal mesh 36 sandwiched between the partitions 33. The hexagonal metal mesh 36 is located at the bottom of the cavity. Near the top of each pair of partitions 33, a gas collecting pipe 37 is provided. The gas collecting pipes 37 extend to the outside of the kerosene filter deaerator 3 and converge into a single gas collecting pipe 37 leading to an oil-gas separator 38. The oil-gas separator 38 is connected to the dedicated exhaust valve 39 of the kerosene filter deaerator via a pipeline. An inlet 31 is located at the rightmost end of the kerosene filter deaerator 3, and the inlet 31 communicates with the cavity on the right side of the orifice plate.

[0059] Furthermore, the oxygen scavenger 35 is a composite material composed of a porous medium and an active metal powder. The porous medium is preferably sponge copper, and the active metal powder is preferably aluminum powder or active iron powder.

[0060] The purpose of the kerosene filter deaerator 3 is to inhibit kerosene coking. Background technology indicates that one factor contributing to kerosene coking is the oxidation reaction between oxygen in the system and kerosene at high temperatures, producing elemental carbon. Therefore, removing as much oxygen as possible from the kerosene can effectively prevent coking. Specifically, the main oil tank 11 is unpressurized. As long as the tank is not full, a two-phase interface between kerosene and air will exist within it. When the oil pump 15 draws oil, some air bubbles will inevitably be introduced into the pipeline. When kerosene containing air bubbles enters the inlet 31 of the kerosene filter deaerator 3, alternating baffles 33 force the kerosene to flow in a zigzag pattern inside the kerosene filter deaerator 3. This reduces the flow rate of the kerosene and prolongs its residence time in the kerosene filter deaerator 3. The hexagonal metal mesh 36 increases the resistance to kerosene flow and further reduces the flow rate. At low flow rates, air bubbles entrained in the kerosene are more easily separated. In addition, air bubbles can also be adsorbed onto the hexagonal metal mesh 36 under the influence of polarity or surface tension. The air bubbles separated or adsorbed on the metal mesh will float to the surface under the influence of buoyancy and be collected in the space enclosed by two baffles 33 at the top of the cavity. After the air in this space accumulates to a certain amount, it will enter the gas collecting pipe 37, pass through the oil-gas separator 38, and be discharged through the dedicated exhaust valve 39 of the kerosene filter deaerator. When kerosene flows through orifice plate 34, there are no more bubbles, but the kerosene still contains a small amount of dissolved oxygen. The active metal powder in deoxygenating agent 35 can remove the dissolved oxygen by reacting with oxygen to generate metal oxides. The principle of oil-gas separator 38 is to separate the gas and liquid phases under the action of gravity or surface tension. As an accessory of kerosene filter deoxygenator 3, its function is to separate the small amount of kerosene contained in the air introduced through gas collecting pipe 37 and return it to kerosene filter deoxygenator 3 through gas collecting pipe 37, avoiding the waste caused by kerosene being discharged from exhaust valve 39. In addition, oil-gas separator 38 can also prevent outside air from entering the pipeline through exhaust valve 39.

[0061] Please refer to Figure 6The kerosene cooler 19 is installed inside the upper rear of the wing 17. This is because, under supersonic conditions, the wing section configuration is selected as either a double-arc or diamond shape. When the supersonic airflow encounters the leading edge of the wing, it generates two oblique shock waves on the upper and lower surfaces of the wing, heating the stagnation point at the leading edge. When the supersonic airflow passes over the middle corner of the diamond-shaped wing (or the apex of the double-arc wing), a second oblique shock wave is generated. Because the rear half of the airfoil is narrowed, the airflow generates a series of expansion waves, with the upper surface of the wing expanding more significantly than the lower surface. When the supersonic airflow leaves the wing, two tail shock waves are formed at the trailing edge of the wing. According to thermodynamic principles, shock waves (compression waves) heat the air, while expansion waves lower the air temperature. Therefore, the kerosene cooler 19 is installed on the upper rear surface of the wing, where the expansion effect is strongest.

[0062] Please refer to Figure 7 A metal diaphragm 121 is installed inside the preparatory oil tank 12. The metal diaphragm 121 is elastic and divides the interior of the preparatory oil tank 12 into two areas. One area of ​​the preparatory oil tank 12 is filled with kerosene, and its corresponding outer casing is connected to the three pipelines, including the aforementioned return oil passage 45. The air in the other area is connected to the outside through a connecting pipe 122 inserted into the outer casing. The reason for this design is that the kerosene entering the preparatory oil tank 12 has already had oxygen removed by the kerosene filter deaerator 3. To prevent outside air from re-entering the pipeline and causing coking, the kerosene in the preparatory oil tank 12 needs to be isolated from the outside atmosphere. If a rigid reserve fuel tank 12 design is used, a vacuum will be created inside when the tank is not full. To resist atmospheric pressure, the reserve fuel tank 12 would need a thicker wall, which would add extra weight to the aircraft. Therefore, the reserve fuel tank 12 adopts a flexible design. When the fuel level in the reserve fuel tank 12 changes, the metal diaphragm 121 can move upward or downward under the combined action of fuel pressure and external atmospheric pressure, changing the volume of the effective fuel storage space. Therefore, the reserve fuel tank 12 is designed with a thinner wall, and because of the balance of internal and external pressure, outside air is not easily able to seep into the tank. This solution effectively reduces the aircraft's weight while ensuring isolation from the outside atmosphere.

[0063] Please refer to Figure 8The kerosene mixer 16 has a cylindrical upper end and a funnel-shaped lower end, and is hollow inside. The cylindrical top surface of the kerosene mixer 16 is connected to the ambient temperature oil circuit 42, and the funnel-shaped bottom surface of the lower end is connected to the afterburner oil supply circuit 44. The cylindrical side of the kerosene mixer 16 is connected to the preheating oil circuit 43, and the connection position of the preheating oil circuit 43 is located on one side of the kerosene mixer 16 and is tangent to the cylindrical side of the kerosene mixer. The center position of the funnel-shaped side of the lower end of the kerosene mixer 16 is connected to the return oil circuit 45. This design method is adopted so that when the hot kerosene in the preheating oil line 43 enters the kerosene mixer 16, it will rotate along the cylindrical inner wall of the kerosene mixer 16. When it is necessary to reduce the temperature of the preheating oil line 43, the cold kerosene in the ambient temperature oil line 42 enters the kerosene mixer 16 normally and mixes with the hot kerosene quickly. The funnel shape at the bottom of the kerosene mixer 16 helps to promote uniform mixing of kerosene and concentrate it into the fuel supply line 44 of the afterburner. When recovering kerosene, the kerosene goes through the return oil line 45. Setting the return oil line 45 opposite the preheating oil line 43 helps to reduce flow resistance loss.

[0064] Furthermore, the inner and outer bypass mixer 55 is selected from one of the following: annular mixer, funnel-shaped mixer, chrysanthemum-shaped mixer, and finger-shaped mixer, with the chrysanthemum-shaped mixer being preferred. This is because the chrysanthemum-shaped mixer is the most widely used in turbofan engines in various countries, and it can completely mix the inner and outer bypass airflows in the shortest distance.

[0065] Furthermore, the first pneumatic valve 25, the second pneumatic valve 28, the exhaust valve 27, and various solenoid valves are all normally closed valves, except for the kerosene filter deaerator-specific exhaust valve 39, which is a normally open valve.

[0066] It is worth noting that the compressor, main combustion chamber and turbine mentioned above are indispensable components in traditional aero engines and are based on existing mature technologies. Therefore, only the relative positional relationship of the components of the afterburner mentioned in this invention is described, and their structure and working principle will not be elaborated here.

[0067] Working principle of oil supply pipeline:

[0068] ① Preheating: Aviation kerosene stored in the main fuel tank 11 is drawn out by the fuel pump 15, flows through the check valve 21 and the kerosene filter deaerator 3, and then enters the reserve fuel tank 12; subsequently, the centrifugal fuel pump 14 pressurizes the kerosene to a pressure of over 2.4 MPa and inputs the oil into the preheating pipeline 43. After passing through the preheating oil solenoid valve 23, the kerosene preheating pipeline 43 enters the kerosene preheater 18, where the highest temperature of the heat exchange airflow in the kerosene preheater 18 is 678.5 K. Furthermore, because the specific heat capacity of kerosene... Because the kerosene is relatively large and has a short residence time in the kerosene preheater 18, and because there is a heat transfer temperature difference, the kerosene preheater 18 will only heat the kerosene to about 620K (not exceeding the critical temperature of 653K). The advantage of the kerosene preheater 18 heating the kerosene to a subcritical state is that the lower temperature helps to suppress coking of the kerosene in the preheating pipe 43, and the subcritical kerosene will not undergo a phase change in the pipe, which can avoid the formation of "gas resistance" in the preheating pipe 43 and reduce the kerosene flow rate at the same pressure. The heated kerosene then flows from the preheating pipe 43 into the kerosene mixer 16. Since the ambient temperature oil circuit solenoid valve 24 and the first pneumatic valve 25 are closed, the kerosene must enter the return oil circuit 45. After passing through the throttle valve 26, the Joule-Thomson effect causes a decrease in both the pressure and temperature of the kerosene, especially the pressure, which is almost at atmospheric pressure. It then enters the kerosene cooler 19 through the second pneumatic valve 28. Inside the kerosene cooler 19, the hot kerosene exchanges heat with the cold air outside the wing, cooling it down. When the kerosene is re-injected into the reserve fuel tank 12, it can be considered to be at ambient temperature. The preheating process aims to bring the kerosene to supercritical pressure and subcritical temperature before it enters the afterburner, typically requiring only 20 seconds. During aircraft takeoff and other operating conditions, the kerosene entering the afterburner can be preheated to ensure the afterburner reaches its optimal design conditions. In emergency situations, the preheating process can be skipped, and the system can directly enter the operating state.

[0069] ② Operation: The working principle from the main oil tank 11 to the kerosene preheater 18 is the same as that of preheating. After heating, the kerosene flows out of the kerosene preheater 18 and enters the kerosene mixer 16 through the preheating pipeline 43. Since the second pneumatic valve 28 on the return oil line 45 is in a normally closed state, the kerosene can only enter the afterburner oil supply line 44 through the open first pneumatic valve 25 and be injected into the afterburner 5. In addition, if the temperature of the supercritical kerosene injected by the nozzle of the afterburner is too high (generally higher than 750K, at which point the superheat is 97K), the ambient temperature oil line solenoid valve 24 can be opened to release a certain amount of cold kerosene. The oil is fed into the kerosene mixer 16. The hot kerosene in the preheating pipeline 43 and the ambient temperature kerosene in the ambient temperature oil line 42 are mixed in the kerosene mixer 16 to reduce the temperature of the kerosene entering the afterburner fuel supply line 44. This reduces the superheat of the supercritical kerosene injected into the afterburner nozzles, effectively inhibiting coking of the kerosene in the pressure atomizing nozzle 53, direct injection nozzle 54, first kerosene superheater 581, and second kerosene superheater 582, preventing carbon buildup from affecting fuel injection in the afterburner. The ambient temperature oil line solenoid valve 24 can be controlled by a pulse electrical signal, i.e., high-frequency, periodic switching of its opening and closing state. The advantage of this method is that the oil temperature after mixing in the kerosene mixer 16 is more uniform and easier to control.

[0070] ③ Cooling: Based on the above operating conditions, close the first pneumatic valve 25 to stop supplying fuel to the afterburner and open the second pneumatic valve 28 to allow kerosene to enter the return oil circuit 45. At the same time, increase the power of the centrifugal oil pump 14 (that is, increase the mass flow rate of kerosene). Since the heat flux of the kerosene preheater 18 is constant, increasing the mass flow rate of kerosene will reduce the outlet temperature of the kerosene preheater 18 (generally below 550K). In addition, the ambient temperature oil circuit solenoid valve 24 is also in the open state. The cooled hot kerosene in the preheating pipeline 43 and the ambient temperature kerosene in the ambient temperature oil circuit 42 are mixed together in the kerosene mixer 16, further reducing the oil temperature of the kerosene entering the return oil circuit 45. Finally, the kerosene enters the kerosene cooler 19 to exchange heat with the cold air outside the wing and is cooled to ambient temperature before being re-injected into the reserve oil tank 12. The cooling process is necessary to cool and recover the remaining kerosene in the pipeline after the afterburner is shut down. Generally, it is sufficient to ensure that all the kerosene heated during operation enters the kerosene cooler 19, which usually takes no more than 10 seconds.

[0071] ④Purge: After the cooling process is completed, open the nitrogen pipeline solenoid valve 22. Nitrogen gas enters the preheating oil circuit through the nitrogen pipeline 41 and the nitrogen pipeline solenoid valve 22. Since the preheating oil circuit solenoid valve 23 is closed, the nitrogen gas can only enter the kerosene preheater 18 downwards. After the purging of the kerosene preheater 18 is completed, the nitrogen gas is discharged from the kerosene preheater 18 and enters the kerosene mixer 16. Since the ambient temperature oil circuit solenoid valve 24 is closed, the nitrogen gas is divided into two paths and enters the afterburner combustion chamber supply line 44 and the return oil line 45 respectively. The purging air entering the return oil circuit 45, after passing through the throttle valve 26, can only be discharged into the outside atmosphere through the exhaust valve 27 because the second pneumatic valve 28 is closed. The purging air entering the afterburner fuel supply circuit 44, after passing through the first kerosene superheater 581 and the second kerosene superheater 582, is discharged into the afterburner through the pressure atomizing nozzle 53 and the direct injection nozzle 54, and finally discharged into the outside atmosphere through the tailpipe. The purpose of nitrogen purging is to blow out residual liquid oil droplets in the pipeline. In addition, some heavier components in kerosene may adhere to the pipe wall; nitrogen, heated by the preheating pipeline 43, can evaporate these components into gaseous form and discharge them from the pipeline, ensuring pipeline cleanliness. The purging process generally lasts 3-5 seconds.

[0072] ⑤ Shutdown: After purging, close all valves. At this time, the entire pipeline system, from the preheating oil circuit solenoid valve 23 to the second pneumatic valve 28, is filled with nitrogen, while the remaining pipelines are still filled with kerosene. The afterburner operates for only 1% of the total lifespan of the aircraft engine, so the fuel supply lines are closed most of the time. Replacing the kerosene in the pipelines with nitrogen has two advantages: firstly, it reduces the weight of the entire pipeline system; secondly, the preheating pipeline 43 is in a high heat load area, and using nitrogen as a protective gas to fill the pipeline during non-operational periods can prevent kerosene from coking and clogging the pipeline.

[0073] Table 1. Statistics on the opening and closing status of various valves in the oil supply pipeline under different operating conditions.

[0074]

[0075]

[0076] Afterburner ignition and flame stabilizer principle:

[0077] ①Fuel supply: After entering the afterburner 5 from the fuel supply line 44, the kerosene branches into two lines, which enter the first kerosene superheater 581 and the second kerosene superheater 582 respectively. Since the intake temperature of the inner duct 52 is very high, the heat will be transferred to the first kerosene superheater 581 and the second kerosene superheater 582 through the wall of the central cone 56, heating the kerosene in it from the subcritical state to the supercritical state. At the same time, the kerosene absorbs a lot of heat during the heating process, which can effectively reduce the temperature of the wall of the central cone 56 and play a cooling role.

[0078] ② Mixing: The pressure atomizing nozzle 53 injects supercritical kerosene into the inner duct 52. Due to the large injection angle of the pressure atomizing nozzle 53, the sprayed oil mist field is similar to a cone, which has the advantages of rapid momentum decay and good kerosene mixing effect. In addition, the high intake temperature of the inner duct 52 and the easy mixing characteristics of supercritical kerosene mean that the intake air of the inner duct 52 is already uniformly mixed with kerosene before reaching the inner and outer bypass mixer 55, forming a gas-fuel mixture with an oil-gas ratio of around 0.04. Subsequently, under the action of the inner and outer bypass mixer 55, the high-temperature, low-oxygen intake air of the inner duct 52 mixes with the lower-temperature, normal-oxygen intake air of the outer bypass duct 51, which plays a role in supplementing oxygen to the afterburner. The mixture is considered to be uniformly mixed before reaching the direct injection nozzle 54. It is worth mentioning that the nozzle size of the pressure atomizing nozzle 53 is relatively large, and according to Bernoulli's principle, it cannot achieve a high injection pressure, belonging to transcritical injection (injection pressure 2.2-2.6MPa).

[0079] ③ Flame Stabilization: The direct-injection nozzle 54 acts as a pneumatic flame stabilizer. Due to its small orifice size, the direct-injection nozzle 54 can achieve a higher injection pressure (3.8-4.0 MPa) according to Bernoulli's principle. Furthermore, the second kerosene superheater 582 is close to the flame position in the afterburner, resulting in a larger heat flux entering the superheater and heating the kerosene to a higher injection temperature (700-713 K). Therefore, the kerosene ejected from the direct-injection nozzle 54 has high velocity and momentum. A recirculation zone is constructed through the interaction of the high-speed supercritical kerosene jet with the mainstream. Within this recirculation zone, there are always areas where the airflow velocity is exactly equal to the flame propagation velocity at that point, satisfying the flame stabilization condition.

[0080] ④ Ignition: During ignition, a small amount of liquid kerosene can be injected using the room temperature kerosene nozzle 591, while the spark plug 592 continues to discharge. Due to the low injection velocity of the room temperature kerosene, and the low-velocity recirculation zone formed by the airflow in the concave cavity 59, the room temperature kerosene droplets form a flame nucleus under the excitation of the electric spark. Because of the low-velocity conditions in the concave cavity 59, the flame nucleus stays in the concave cavity 59 for a longer period of time, allowing it to fully develop until a stable ignition source is formed. At this point, stop the injection of kerosene from the room temperature kerosene nozzle 591 and the discharge from the spark plug 592; the afterburner ignition is successful.

[0081] Working principle of kerosene preheater 18 (first kerosene superheater 581, second kerosene superheater 582):

[0082] The formula for calculating the heat of a partitioned heat exchanger is Φ = k·A·Δt. m

[0083] Where: Q is the heat transfer rate in kW; k is the overall heat transfer coefficient in W / (m³). 2·K); A is the effective heat exchange area, in m² 2 Δtm is the average temperature difference between the inlet and outlet of the heat exchanger, in K.

[0084] The kerosene preheater 18, the first kerosene superheater 581, and the second kerosene superheater 582 include multiple independently operable heat exchanger modules 66. When the heat exchangers are operating, some of the heat exchanger modules 66 can be shut down. At this time, A represents a reduction in the effective heat exchange area. Simultaneously, the mass flow rate of kerosene entering the heat exchangers remains constant, but the kerosene flow velocity increases. This leads to a decrease in the overall heat transfer coefficient k. Since the mass flow rate of air outside the heat exchangers remains constant, the heat transfer Φ remains constant. According to the heat calculation formula for indirect heat exchangers, the final result is Δt. m As the inlet kerosene temperature remains constant, the outlet kerosene temperature increases compared to before. Similarly, when a portion of heat exchanger module 66 is activated, the effective heat exchange area (A) increases. Simultaneously, the mass flow rate of kerosene entering the heat exchanger remains constant, but the kerosene flow velocity decreases. This leads to an increase in the overall heat transfer coefficient (k). Since the mass flow rate of air outside the heat exchanger remains constant, the heat transfer rate (Φ) remains constant. According to the heat calculation formula for indirect heat exchangers, the final result is Δt. m The temperature of the kerosene at the outlet decreases compared to the original temperature, while the inlet kerosene temperature remains unchanged.

[0085] Working principle of a single heat exchanger module:

[0086] ① Operation: The aforementioned three-way valve 64 is a T-type confluence three-way valve with three operating modes: left-in, right-in, and closed. During operation, the three-way valve 64 is in the "right-in" mode. Kerosene in the first kerosene pipeline 61 enters the three-way valve 64 from the right side of the T-type confluence three-way valve and flows out from the valve outlet into the heat exchanger 66. However, because the left inlet of the T-type confluence three-way valve is closed, nitrogen in the nitrogen pipeline 63 cannot enter the three-way valve 64. Subsequently, the kerosene is heated in the heat exchanger 66 and flows out from the heat exchanger outlet, passing through the heat exchanger-specific check valve 65 before converging into the second kerosene pipeline 62. See details... Figure 9 .

[0087] ②Purge: When switching from the working state to the purging state, the three-way valve 64 is in the "left-in" working mode. Nitrogen in the nitrogen pipeline 63 enters the three-way valve 64 from the left side of the T-type merging three-way valve and flows out from the outlet of the three-way valve into the heat exchanger 66. However, because the right inlet of the T-type merging three-way valve is closed, the kerosene in the first kerosene pipeline 61 cannot enter the three-way valve 64. Subsequently, nitrogen enters the heat exchanger 66, discharging the residual liquid kerosene in the heat exchanger 66. Finally, the mixture of nitrogen and liquid kerosene enters the second kerosene pipeline 62. In addition, some kerosene may adhere to the tube wall of the heat exchanger 66. The nitrogen heated by the heat exchanger 66 can evaporate the residual kerosene into gas and blow it out of the pipeline to ensure pipeline cleanliness.

[0088] ③ Shutdown: With the purging state in place, switch the three-way valve 64 to the "closed" operating mode. The nitrogen in heat exchanger 66 loses its supply pressure. However, under the action of the dedicated one-way valve 65, the high-pressure kerosene in the second kerosene pipeline 62 cannot flow back into heat exchanger 66. Therefore, a cavitation filled with nitrogen is formed in the pipeline of heat exchanger 66. See details... Figure 10 Replacing the kerosene in the pipes of heat exchanger 66 with nitrogen can prevent the kerosene from coking and clogging the pipes of heat exchanger 66 due to long-term exposure to the high heat load environment of heat exchanger 66.

[0089] Table 2. Statistics on the opening and closing status of the three-way valve under different operating conditions of a single heat exchanger module.

[0090]

[0091] The technical effects of the present invention will be illustrated below through specific embodiments and comparative examples. Specific Implementation Example 1:

[0093] The design parameters of the afterburner in a specific embodiment are shown in the table below.

[0094] Table 3 Design Point Parameters for Example 1

[0095] parameter need parameter need Import pressure 192.66 kPa Import pressure on foreign ducts 164.04 kPa Internal import temperature 2167.25K Outer duct inlet temperature 678.5K Internal import flow 51.93 kg / s Outer duct inflow 15.75kg / s Internal oxygen content 12％ Oxygen content at the outer duct inlet 21％ Maximum speed in afterburner 0.6Ma

[0096] In addition, the minimum kerosene flow rate in the afterburner is 1.42 kg / s, and the maximum flow rate is 2.71 kg / s; the minimum kerosene injection temperature is 390℃ (superheat is 10℃), and the injection pressure is 2.2 MPa. Since it does not reach the supercritical pressure, it belongs to transcritical injection; the maximum kerosene injection temperature is 440℃ (superheat is 60℃), and the injection pressure is 4.0 MPa, which belongs to supercritical injection.

[0097] Heat exchanger implementation method: The design method of kerosene preheater 18 is as follows Figure 11As shown, it consists of six heat exchanger modules. Heat exchangers 66 are installed inside the compressor's cooling gas outlet pipeline, and the six heat exchangers 66 are arranged sequentially perpendicular to the pipeline's axial direction. The first kerosene pipeline 61, the second kerosene pipeline 62, and the nitrogen pipeline 63 are located outside the compressor's cooling gas outlet pipeline. The inlet of each heat exchanger 66 is connected to the first kerosene pipeline 61 and the nitrogen pipeline 63 respectively via a three-way valve 64; the outlet of each heat exchanger 66 is connected to the second kerosene pipeline 62 via a dedicated one-way valve 65. The heat exchanger modules are named one through six in sequence according to the flow direction of the compressor's cooling gas outlet pipeline. When the kerosene preheater 18 is working, heat exchanger module one is opened first, and then adjusted according to the outlet temperature of the kerosene preheater 18. When the outlet temperature is high, some heat exchanger modules can be opened sequentially; when the outlet temperature is low, some heat exchanger modules are closed. The design method of the first kerosene superheater 581 (second kerosene superheater 582) is as follows: Figure 12 As shown, the system consists of twelve heat exchanger modules. Heat exchangers 66, the first kerosene pipeline 61, the second kerosene pipeline 62, the nitrogen pipeline 63, the three-way valve 64, and the dedicated one-way valve 65 are all installed inside the central cone 56. The heat exchangers 66 are tightly attached to the inner surface of the central cone and occupy a 30° arc. The second kerosene pipeline 62 is located on the axis inside the central cone 56. Its inlet section branches into twelve branches, which are connected to the outlets of the twelve heat exchangers 66 via the dedicated one-way valve 65. The inlets of the heat exchangers 66 are also connected to the three-way valve 64 via pipes. The first kerosene pipeline 61 is also located on the axis of the central cone 56. The nitrogen pipeline 63 is parallel to the axis of the central cone 56 but in an eccentric position. The end of the first kerosene pipeline 61 branches into twelve branches, which are connected to the right inlets of the twelve three-way valves 64. The end of the nitrogen pipeline 63 is a loop pipe, which is connected to the left inlets of the twelve three-way valves 64. The heat exchanger modules are named one through twelve in clockwise order. When the kerosene preheater 18 is working, the heat exchanger modules are opened symmetrically. For example, the first step is to open heat exchanger modules one and seven, the second step is to open heat exchanger modules four and ten, and so on. Choosing to open the heat exchanger modules symmetrically is to minimize thermal stress and improve the service life of the central cone 56. In summary, the working principle of the kerosene preheater 18 and the first kerosene superheater 581 (second kerosene superheater 582) in specific embodiment 1 is similar to... Figure 4 The kerosene preheater shown is no different from the one in the example; the only difference is that the number and shape of the heat exchanger modules have been optimized according to the application scenario in Specific Embodiment 1.

[0098] The method of injecting fuel into the nozzles is as follows: The pressure atomizing nozzle 53 injects fuel perpendicular to the main flow direction, with a 45° injection cone angle. 24 pressure atomizing nozzles 53 are arranged at 15° intervals around the circumference of the afterburner. Similarly, 24 direct-injection nozzles 54 are arranged around the central cone 56, also perpendicular to the main flow direction. The mass flow rate ratio of the pressure atomizing nozzles 53 to the direct-injection nozzles 54 is 9:1. The flow rate of a single pressure atomizing nozzle 53 is 36 g / s, the injection pressure is 2.5 MPa, and the kerosene injection temperature is 398°C. The flow rate of a single direct-injection nozzle 54 is 4 g / s, the injection pressure is 3.9 MPa, and the kerosene injection temperature is 435°C. Specific Implementation Example 2:

[0100] The design parameters and heat exchanger implementation methods are the same as in Example 1.

[0101] Nozzle oil injection method: The injection direction of the pressure atomizing nozzle 53 is perpendicular to the mainstream, and the injection cone angle is 45°; the injection direction of the direct injection nozzle 54 is 30° opposite to the mainstream direction; the mass flow rate ratio of the pressure atomizing nozzle 53 to the direct injection nozzle 54 is 9:1; the flow rate of a single pressure atomizing nozzle 53 is 36 g / s, the injection pressure is 2.5 MPa, and the kerosene injection temperature is 398°C; the flow rate of a single direct injection nozzle 54 is 4 g / s, the injection pressure is 3.9 MPa, and the kerosene injection temperature is 435°C. Specific Implementation Example 3:

[0103] The design parameters and heat exchanger implementation methods are the same as in Example 1.

[0104] Nozzle oil injection method: The injection direction of the pressure atomizing nozzle 53 is perpendicular to the mainstream, and the injection cone angle is 45°; the injection direction of the direct injection nozzle 54 is opposite to the mainstream direction at 45°; the mass flow rate ratio of the pressure atomizing nozzle 53 to the direct injection nozzle 54 is 9:1; the flow rate of a single pressure atomizing nozzle 53 is 36 g / s, the injection pressure is 2.5 MPa, and the kerosene injection temperature is 398°C; the flow rate of a single direct injection nozzle 54 is 4 g / s, the injection pressure is 3.9 MPa, and the kerosene injection temperature is 435°C. Specific Implementation Example 4:

[0106] The design parameters, heat exchanger implementation method, and spraying of pressure atomizing nozzle 53 and direct injection nozzle 54 are the same as in Example 3.

[0107] The mass flow rate ratio of the pressure atomizing nozzle 53 to the direct injection nozzle 54 is 19:1. The flow rate of a single pressure atomizing nozzle 53 is 38 g / s, the injection pressure is 2.5 MPa, and the kerosene injection temperature is 400℃. The flow rate of a single direct injection nozzle 54 is 2 g / s, the injection pressure is 3.8 MPa, and the kerosene injection temperature is 425℃. Specific Implementation Example 5:

[0109] The design parameters, heat exchanger implementation method, and spraying of pressure atomizing nozzle 53 and direct injection nozzle 54 are the same as in Example 3.

[0110] The mass flow rate ratio of the pressure atomizing nozzle 53 to the direct injection nozzle 54 is 4:1. The flow rate of a single pressure atomizing nozzle 53 is 32 g / s, the injection pressure is 2.3 MPa, and the kerosene injection temperature is 385℃; the flow rate of a single direct injection nozzle 54 is 8 g / s, the injection pressure is 4.0 MPa, and the kerosene injection temperature is 440℃.

[0111] Example for comparison:

[0112] The design parameters, heat exchanger implementation method, and spraying of pressure atomizing nozzle 53 and direct injection nozzle 54 are the same as in Example 1, but pressure atomizing nozzle 53 and direct injection nozzle 54 do not spray oil.

[0113] To investigate the influence of the supercritical kerosene jet ejected from the direct-injection nozzle 54 on the size of the recirculation zone and the total pressure recovery coefficient in Examples 1-5, Fluent computational fluid dynamics software was used to simulate Examples 1-5 and the control example. To simplify the model, a 1 / 12 circle of the afterburner was selected as the fluid domain, containing a pair of pressure atomizing nozzles 53 and a direct-injection nozzle 54. The pressure atomizing nozzle 53 did not inject oil, while only the direct-injection nozzle 54 injected oil. The streamlines and oil-gas distribution cloud maps on the axial cross-section of each example were obtained, and the pressure parameters at each point at the inlet and outlet of the fluid domain were extracted. The total pressure recovery coefficient was calculated using the following formula.

[0114] Total pressure recovery coefficient

[0115] Figure 13 The streamlines and oil-gas distribution cloud map on the axial section in the comparative example show that no backflow zone is observed in the fluid domain. Only the streamlines of the pressure atomizing nozzle 53 are slightly curved at the concave cavity 59. Since the direct-injection nozzle 54 in the comparative example does not spray oil, the oil-gas ratio in the fluid domain is 0.

[0116] Figure 14The streamlines and oil-gas distribution cloud map on the axial section of Specific Embodiment 1 show that after the supercritical kerosene is injected, it is driven by momentum and sprayed onto the wall of the afterburner 5. A large elliptical recirculation zone is formed near the central cone 56 on the rear side of the jet, with the major axis of the elliptical recirculation zone closely attached to the outer wall of the central cone 56. A smaller recirculation zone is formed on the wall of the afterburner 5 on the front side of the jet. The streamlines of the air intake in the outer duct 51 of the afterburner deflect downward after passing through the inner and outer duct mixer 55, indicating that a good mixing effect between the inner and outer ducts has been achieved. Immediately after injection, the supercritical kerosene jet has a core oil-to-gas ratio greater than 0.1. Subsequently, the jet rapidly mixes with the mainstream, reaching a near-equivalent ratio of 0.04-0.06 in the middle of the jet. However, near the wall of the afterburner 5, it reaches a lean state with an equivalent ratio less than 0.03. This indicates that the direct-injection nozzle 54 achieves excellent mixing after injection, and the equivalent ratio in the middle of the combustion chamber is optimal for combustion, which is beneficial for subsequent combustion and flame stability. However, specific embodiment 1 also has drawbacks. The recirculation zone being too close to the wall of the central cone 56 causes the flame to also be close to the wall of the central cone 56 after ignition, resulting in excessively high wall temperatures and affecting its service life.

[0117] Figure 15 The streamlines and oil-gas distribution cloud map on the axial section in Specific Embodiment 2 show that, compared to Specific Embodiment 1, the recirculation zone behind the jet has moved upward and away from the outer wall of the central cone 56, but the area of ​​the recirculation zone is smaller than in Specific Embodiment 1; while the recirculation zone at the wall of the afterburner 5 in front of the jet is slightly larger than in Specific Embodiment 1. Apart from this, the oil-gas ratio distribution is not significantly different from that in Specific Embodiment 1.

[0118] Figure 16 The diagram shows the streamlines and oil-gas distribution cloud map on the axial section in Specific Embodiment 3. Compared with Specific Embodiments 1-2, two recirculation zones, one large and one small, appear behind the jet. The combined area of ​​the recirculation zone can be approximated as an ellipse. However, one short axis of the elliptical recirculation zone is in close contact with the outer wall of the central cone 56, while the other short axis is in close contact with the wall of the afterburner 5, presenting a "vertical" state sandwiched between the two walls of the fluid domain. Furthermore, the area of ​​the recirculation zone is the largest among all embodiments. Compared with Specific Embodiments 1-2, the recirculation zone in front of the jet disappears. Considering the oil-gas ratio distribution, this may be due to insufficient supercritical kerosene jet flow, preventing it from directly acting on the wall of the afterburner 5. Since the recirculation zone area in Specific Embodiment 3 is the largest, almost encompassing the entire fluid domain, and does not adhere to the wall surface, Specific Embodiment 3 can ensure flame stability and prevent overheating of the afterburner 5 wall during subsequent combustion, making it the most preferred embodiment.

[0119] Figure 17The streamlines and oil-gas distribution cloud map on the axial section in specific embodiment 4 show that, compared with specific embodiment 3, the most obvious difference is that the jet deflects in the middle of the fluid domain in the oil-gas distribution map. This is caused by the reduced injection flow rate and insufficient jet momentum of the direct-injection nozzle 54. The most obvious effect of insufficient jet momentum is that the recirculation zone behind the jet becomes smaller and its position shifts downward; the recirculation zone formed on the wall of the afterburner 5 in front of the jet disappears.

[0120] Figure 18 The streamlines and oil-gas distribution cloud map on the axial section of Specific Embodiment 5 show the most significant difference compared to Specific Embodiment 3. The recirculation zone behind the jet is smaller and more closely adheres to the outer wall of the central cone 56; while the recirculation zone formed on the wall of the afterburner 5 in front of the jet is larger, the largest among all embodiments. The reason for the larger recirculation zone in front of the jet is that the jet interacts with the wall of the afterburner 5 with greater momentum. The reason for the smaller recirculation zone behind the jet is that the supercritical kerosene injection velocity is too high, forming a low-pressure zone behind the jet. In the three-dimensional fluid domain, some gas flow bypasses the jet and enters the low-pressure zone, effectively "filling" the original recirculation zone position. Therefore, blindly increasing the jet flow rate will not increase the area of ​​the recirculation zone and may even have the opposite effect.

[0121] Table 4. Total pressure recovery coefficients of specific embodiments 1-5 and the control example under different conditions.

[0122]

[0123] The simulation results of the above six sets of structures show that a recirculation zone appears in the flow field of all five specific embodiments, with the largest recirculation zone areas in specific embodiments 1 and 3. The total pressure recovery coefficients of specific embodiments 1-5 and the control example are almost identical under cold conditions. As shown in specific embodiments 1-3, under hot conditions, the total pressure recovery coefficient decreases as the injection angle of the direct-injection nozzle 54 increases. However, in specific embodiments 3-5, under hot conditions, the total pressure recovery coefficient increases as the injection flow rate of the direct-injection nozzle 54 decreases, but the injection angle and flow rate have little effect on the total pressure recovery coefficient. Considering factors such as the location of the recirculation zone and the distribution of oil and gas, specific embodiment 3 is the most preferred.

[0124] In summary, this invention replaces the bluff flame stabilizer or pneumatic flame stabilizer in a traditional afterburner with a direct-injection nozzle injecting supercritical kerosene, achieving a total pressure recovery coefficient of over 97.6% while constructing a larger recirculation zone. Furthermore, using supercritical kerosene as fuel offers advantages such as higher injection pressure and jet flow, easier ignition, better air mixing, faster combustion reaction, and higher combustion efficiency. Moreover, it overcomes the drawback of supercritical kerosene's tendency to coke.

[0125] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A supercritical kerosene-based anti-coking, low-blockage afterburner, characterized in that, include: The main fuel tank (11) is located inside the wing (17) and has a pipeline leading to the inlet pipe of the fuel pump (15). The outlet pipe of the fuel pump (15) is connected to the check valve (21) via a pipeline. The outlet end of the check valve (21) is connected to the reserve fuel tank (12) via a pipeline after passing through the kerosene filter deaerator (3). The reserve fuel tank (12) has three pipelines, one of which is connected to the check valve (21) mentioned above, and the rest are connected to the check valve (21). Two pipes lead to the inlet of the centrifugal oil pump (14) and the outlet of the kerosene cooler (19), respectively. The outlet of the centrifugal oil pump (14) is connected to a pipeline, which then branches into two pipes named the ambient temperature oil circuit (42) and the preheating oil circuit (43), respectively. The preheating oil circuit (43) passes through the preheating oil circuit solenoid valve (23) and the kerosene preheater (18) in sequence, and finally leads to the kerosene mixer (16). The ambient temperature oil circuit (42) is equipped with an ambient temperature oil circuit solenoid valve (24), which then... The kerosene mixer (16) is connected to four oil circuits. In addition to the above-mentioned ambient temperature oil circuit (42) and preheating oil circuit (43), there is also an afterburner oil supply circuit (44) and a return oil circuit (45). The afterburner oil supply circuit (44) is connected to the first pneumatic valve (25), and the outlet end of the first pneumatic valve (25) is connected to the afterburner (5). The return oil circuit (45) first passes through the throttle valve (26) and then branches off, with one end... Connected to the exhaust valve (27), the other end is connected to the inlet of the kerosene cooler (19) via the second pneumatic valve (28); a nitrogen pipeline (41) is inserted into the preheating oil pipeline (43) between the preheating oil pipeline solenoid valve (23) and the kerosene preheater (18). One end of the nitrogen pipeline (41) is connected to the preheating oil pipeline (43), and the other end is connected to a high-pressure nitrogen tank (13). A nitrogen pipeline solenoid valve (22) is also connected to the middle section of the nitrogen pipeline (41). The afterburner (5) structure includes a central cone (56), and two layers of cylindrical bodies are coaxially fitted on the outside of the central cone (56) to divide the flow channel into an inner duct (52) and an outer bypass duct (51). The cross-sections of the inner duct (52) and the outer bypass duct (51) are concentric circles. The left side of the inner duct (52) is connected to the turbine and the main combustion chamber, and the left side of the outer bypass duct (51) is the outer bypass duct of the turbofan engine. The length of the inner cylindrical body is less than the length of the central cone (56), and the length of the central cone (56) is less than the length of the outer cylindrical body. In addition, the right end of the inner cylindrical body is connected to an inner and outer bypass mixer (55). The central cone (56) has a ring of pressure atomizing nozzles (53) radially arranged on the outer surface of the inner channel (52) entrance. The central cone (56) has a ring of direct-shot nozzles (54) radially arranged on the outer surface of the inner and outer channel mixer (55) on the right side. The direct-shot nozzles (54) have a recess (59) on the right side. The spray direction of the direct-shot nozzles (54) is perpendicular to the mainstream direction or opposite to the mainstream direction at 30° or 45°. The above-mentioned afterburner oil supply line (44) penetrates the outer cylinder and enters the afterburner (5) and extends into the central cone (56). Then the afterburner oil supply line (44) branches into two paths. One path goes to the left and enters the first kerosene superheater (581) and then leads to the pressure atomizing nozzle (53); the other path goes to the right and enters the second kerosene superheater (582) and then leads to the direct injection nozzle (54). The pressure atomizing nozzle (53) serves as the main fuel injection hole, injecting supercritical kerosene into the main stream and rapidly mixing the kerosene evenly. The direct-fire nozzle (54) acts as a flame stabilizer, creating a recirculation zone by injecting a small portion of high-speed supercritical kerosene jets that interact with the main stream, thereby maintaining flame stability.

2. The anti-coking, low-blockage ratio afterburner based on supercritical kerosene according to claim 1, characterized in that: The first kerosene superheater (581) and the second kerosene superheater (582) are annular structures, installed inside the central cone (56) and close to the inner surface of the central cone. The first kerosene superheater (581) is installed between the pressure atomizing nozzle (53) and the direct injection nozzle (54). The second kerosene superheater (582) is installed between the right side of the concave cavity (59) and the tip of the central cone (56). The effective heat exchange area of ​​the second kerosene superheater (582) is smaller than that of the first kerosene superheater (581).

3. The anti-coking, low-blockage ratio afterburner based on supercritical kerosene according to claim 1, characterized in that: The oil supply line (44) of the afterburner is covered with an oil pipe heat insulation protective sleeve (57) between the central cone (56) and the outer cylinder of the afterburner.

4. The anti-coking, low-blockage ratio afterburner based on supercritical kerosene according to claim 1, characterized in that: The kerosene preheater (18) is placed at the inlet of the main combustion chamber at the compressor outlet or inside the cooling gas pipeline leading out of the compressor, where it exchanges heat with the hot air compressed by the compressor. The kerosene preheater (18) includes multiple heat exchanger modules, each of which includes a three-way valve (64). The three-way valve (64) is a T-type confluence three-way valve. A branch pipe branches off from the first kerosene pipeline (61) to one inlet of the three-way valve (64). Similarly, a branch pipe branches off from the nitrogen pipeline (41) to the other inlet of the three-way valve (64). The outlet of the three-way valve (64) is connected to the heat exchanger (66) through a pipeline. The other end of the heat exchanger (66) leads out a pipeline to the heat exchanger-specific check valve (65) and then extends and merges into the second kerosene pipeline (62). The three-way valve (64) and the heat exchanger-specific check valve (65) are located away from the high heat load area around the heat exchanger.

5. The anti-coking, low-blockage ratio afterburner based on supercritical kerosene according to claim 1, characterized in that: The interior of the kerosene filter deaerator (3) is divided into two cavities by a perforated plate (34). The cavity on the left side of the perforated plate (34) is filled with deaerator (35), and an outlet (32) is provided at its lower part. The cavity on the right side of the perforated plate (34) is alternately equipped with partitions (33), and a hexagonal metal mesh (36) is sandwiched between the partitions (33). The hexagonal metal mesh (36) is located at the bottom of the cavity. A gas collecting pipe (37) is provided between each pair of partitions (33) near the top of the cavity. The gas collecting pipe (37) extends... Extending to the outside of the kerosene filter deaerator (3) and converging into a gas collecting pipe (37) leading to the oil-gas separator (38), the oil-gas separator (38) is connected to the kerosene filter deaerator special exhaust valve (39) through a pipeline; the rightmost end of the kerosene filter deaerator (3) is provided with an inlet (31), the inlet (31) is connected to the cavity on the right side of the orifice plate (34); the deaerator (35) is a composite material composed of porous media and active metal powder, the porous media is sponge copper, and the active metal powder is aluminum powder or active iron powder.

6. The anti-coking, low-blockage ratio afterburner based on supercritical kerosene according to claim 1, characterized in that: The kerosene cooler (19) is installed inside the rear upper part of the wing (17).

7. The anti-coking, low-blockage ratio afterburner based on supercritical kerosene according to claim 1, characterized in that: The kerosene mixer (16) is cylindrical at the top and funnel-shaped at the bottom, and is hollow inside. The cylindrical top surface of the kerosene mixer (16) is connected to the ambient temperature oil circuit (42), and the funnel-shaped bottom surface of the bottom is connected to the afterburner oil supply circuit (44). The cylindrical side of the kerosene mixer (16) is connected to a preheating oil circuit (43), and the connection position of the preheating oil circuit (43) is located on one side of the kerosene mixer (16) and is tangent to the cylindrical side of the kerosene mixer (16). The center position of the funnel-shaped side of the bottom of the kerosene mixer (16) is connected to a return oil circuit (45).

8. A supercritical kerosene-based anti-coking, low-blockage ratio afterburner according to any one of claims 1 to 5, characterized in that: The first pneumatic valve (25), the second pneumatic valve (28), the exhaust valve (27), and all kinds of solenoid valves are normally closed valves, except for the exhaust valve (39) for the kerosene filter deaerator, which is normally open valve.

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