A self-igniting assisted combustion aeroengine ultra-compact turbine interstage combustion chamber

Abstract

The application discloses a self-ignition combustion supporting super-compact inter-stage combustion chamber for an aero-engine, aiming at optimizing the combustion efficiency of the transition section between the high-pressure turbine and the low-pressure turbine. The combustion chamber comprises a transition section outer casing, a transition section inner casing, a flame tube and an oil-gas premixing device. By coupling the oil-gas mixing and flow process under high-temperature conditions, the fuel droplets are rapidly evaporated and mixed in the high-temperature air, while the flow residence time and self-ignition delay time of the oil-gas mixture are adjusted, so that the chemical reaction rate is significantly improved. This design significantly shortens the flame length and improves the combustion efficiency, while allowing the length of the combustion chamber to be reduced, thereby shortening the engine shaft and improving the rotor dynamics. In addition, the short flame helps to reserve more space at the rear end of the combustion chamber for regulating the outlet temperature distribution, thereby providing more uniform inlet conditions for the turbine and improving the service life of the turbine.

Description

Technical Field

[0001] This invention belongs to the field of aero-engine combustor technology, and relates to the optimized design of inter-turbine burners (ITBs). Specifically, it is a self-igniting, ultra-compact inter-turbine burner for aero-engines. By utilizing the fuel-air mixture at high temperatures to achieve a near-self-ignition state to increase flame propagation speed, and by optimizing the residence time and self-ignition delay time of the fuel-air mixture, the chemical reactivity of the fuel-air mixture is changed, thereby accelerating the chemical reaction rate and shortening the combustion chemical reaction time. This is used to shorten the size of the combustor and reduce the engine shaft or weight. Background Technology

[0002] In modern aero-engine technology, increasing the thrust of the power plant section is key to optimizing the performance of wide-speed-range aircraft. Current main methods involve increasing the turbine inlet temperature or the compressor pressure ratio. Currently, the turbine inlet temperature of aero-engines has reached over 1800K, and further increasing it is becoming increasingly difficult, placing extremely high demands on materials and manufacturing technologies. Due to limitations in current material development, even with gradual improvements in turbine cooling technology, there are still certain limitations to increasing the turbine inlet temperature.

[0003] The demand for high-thrust engines has spurred the development of new engine technologies. One approach involves adding an inter-turbine burner (ITB) between the two turbine stages. Under high-thrust conditions, the ITB opens, increasing the engine's thrust. During low-power conditions such as cruise, the ITB closes, thus balancing the need for high thrust at takeoff and low fuel consumption during cruise. Existing overall engine performance studies show that engines with ITBs offer significantly higher thrust per unit area compared to conventional engines, while only slightly increasing fuel consumption.

[0004] Domestic and international research institutions have conducted extensive research on turbine-stage combustion chambers, with numerous experimental and theoretical studies focusing on improving combustion efficiency and optimizing outlet temperature distribution. Research results indicate that turbine-stage combustion chambers employing Trapped Vortex Combustion (TVC) exhibit excellent ignition and quenching characteristics, and the influence of TVC on combustion efficiency and outlet temperature has been determined.

[0005] While interstage combustion chamber technology has shown great potential in improving engine performance, its practical application still faces numerous technical challenges. Because the interstage combustion chamber is located in the transition section between the high- and low-pressure turbines, its spatial dimensions and layout are limited. This spatial constraint not only affects the design and overall layout of the combustion chamber but may also lead to technical issues such as low operating pressure and high characteristic velocity. Furthermore, compared to the main combustion chamber, the interstage combustion chamber operates at lower pressures and higher characteristic velocities. When using liquid fuels, this results in limited atomization, evaporation, mixing, and combustion chemical reaction times, easily leading to large total pressure losses, low combustion efficiency, and poor outlet temperature distribution, thus affecting the overall performance and reliability of the engine. Simultaneously, to meet the time requirements of combustion reactions, existing technologies typically require extending the length of the combustion chamber. However, this increases the engine's axial dimensions and weight, potentially adversely affecting rotor dynamics. Moreover, an extended combustion chamber may lead to heat loss during combustion, further reducing combustion efficiency.

[0006] In summary, designing an efficient and reliable interstage combustion chamber within a compact and limited space to address the limitations of liquid fuel atomization, evaporation, mixing, and combustion chemical reaction time, improve combustion efficiency and optimize outlet temperature distribution, shorten the combustion chamber length to reduce engine axial dimensions and weight, improve rotor dynamics, and reduce heat loss are urgent technical challenges. Solving these problems will help meet the requirements of wide-speed-range aircraft for high-section thrust power plants. Summary of the Invention

[0007] (I) Purpose of the Invention

[0008] Addressing the numerous shortcomings and deficiencies of existing turbine interstage combustion chambers in practical applications, such as low operating pressure and high characteristic velocity due to space constraints, fuel atomization, evaporation, mixing, and limited combustion chemical reaction time, this invention aims to provide a self-igniting, ultra-compact interstage combustion chamber to solve at least one of the aforementioned and other technical problems in the prior art. Through the coupled design of fuel-air mixing and flow processes under high-temperature conditions, on the one hand, fuel droplets rapidly evaporate and mix in high-temperature air; on the other hand, the flow residence time and self-ignition delay time of the fuel-air mixture are adjusted in the mixing channel, improving its combustion chemical reaction activity and rate, thereby shortening the flame length and significantly improving combustion efficiency. Furthermore, the shortened flame length and optimized combustion process also help to reserve more space to regulate the combustion chamber outlet temperature distribution, providing the turbine with more uniform intake conditions, improving turbine life, and also facilitating a shorter combustion chamber length, shorter engine shaft system, and improved rotor dynamics.

[0009] (II) Technical Solution

[0010] To achieve the objective of this invention and solve its technical problems, the present invention adopts the following technical solution:

[0011] An ultra-compact interstage combustion chamber with self-ignition and combustion assistance is disclosed for efficient afterburning in the transition section between the high-pressure and low-pressure turbines of an aero-engine. It includes an outer transition section casing, an inner transition section casing, a flame tube, and several fuel-air premixing devices. The outer and inner transition section casings are located in the meridional direction between the high-pressure and low-pressure turbines.

[0012] The outer casing of the transition section is generally annular, with its front sidewall connected to the upstream high-pressure turbine casing and its rear sidewall connected to the downstream low-pressure turbine casing. Its radially outer sidewall protrudes outward relative to the upstream high-pressure turbine casing and the downstream low-pressure turbine casing.

[0013] The flame tube is generally annular and is disposed within the annular space formed between the outer casing and the inner casing of the transition section. It is radially adjacent to the outer casing and, in the meridional direction, sequentially includes an upstream tube wall section, a midstream tube wall section, and a downstream tube wall section.

[0014] The upstream cylindrical wall section is shaped to fit the high-pressure turbine casing and has a radial distance between it and the high-pressure turbine casing.

[0015] The downstream cylindrical wall section is shaped to fit the radial outer wall of the transition section outer casing, with its upstream end fixedly connected to the midstream cylindrical wall section and its downstream end fixedly connected to the low-pressure turbine casing.

[0016] The midstream cylindrical wall section includes a front sidewall, a rear sidewall, and a radially outer sidewall located between the two. Its front sidewall connects to the upstream cylindrical wall section, and its rear sidewall connects to the downstream cylindrical wall section. The radially outer sidewall protrudes outward relative to both the upstream and downstream cylindrical wall sections, and this outward protrusion forms the combustion zone of the flame tube.

[0017] Furthermore, in the midstream cylindrical wall section, multiple vortex airflow guiding slots are evenly distributed circumferentially at the first connection between the upstream end of its radially outer sidewall and the top of its front sidewall, the second connection between the downstream end of its radially outer sidewall and the top of its rear sidewall, and the third connection between the bottom of its rear sidewall and the upstream end of the downstream cylindrical wall section.

[0018] The vortex airflow guide slots located at the first connection are structurally configured to guide the airflow radially in a direction toward the combustion chamber axis, from the outside to the combustion zone of the flame tube.

[0019] The airflow guide slots of each vortex system located at the second connection are structurally designed to guide the airflow from the outside to the inside into the combustion zone of the flame tube in a manner parallel to the radial outer wall of the midstream cylinder section.

[0020] The vortex airflow guide slots located at the third connection are structurally configured to guide the airflow radially in a direction opposite to the combustion chamber axis to be injected from the outside to the combustion zone of the flame tube;

[0021] The plurality of oil-gas premixing devices are evenly arranged circumferentially within the annular space between the outer casing and the inner casing of the transition section. Each of the oil-gas premixing devices is a tubular structure, and along its length includes a fuel atomization and evaporation mixing section and a fuel cracking section.

[0022] The fuel atomization and evaporation mixing section is radially arranged on the outer side of the upstream section of the flame tube. Its inlet is roughly aligned with the direction of the high-temperature combustion gas discharged from the high-pressure turbine, and a fuel nozzle is provided on the pipe wall near its inlet. The fuel nozzle is connected to the fuel pipe of an external fuel supply device.

[0023] The fuel cracking section passes through the front sidewall of the midstream section of the flame tube and extends into the combustion zone of the flame tube, with its outlet end extending spatially to a position near the first connection point.

[0024] Preferably, the high-pressure turbine gas entering the combustion zone of the flame tube accounts for 20%-60% of the total gas volume discharged from the high-pressure turbine, and the proportion of high-pressure turbine gas entering the combustion zone through the airflow guide slots of each vortex system is controlled at 10%-40% to ensure the formation of a strong swirling environment, guarantee the full mixing of fuel and high-pressure turbine gas and stable flame combustion, and realize an efficient and stable secondary combustion process in the combustion zone.

[0025] Preferably, the number of oil-gas premixing devices is 10-30, evenly arranged in the circumference, to ensure uniform distribution and efficient combustion of the oil-gas mixture inside the flame tube.

[0026] Furthermore, the inner diameter of each of the aforementioned oil-gas premixing devices ranges from 6 to 12 mm, the inner diameter of each of the aforementioned fuel pipes ranges from 2 to 4 mm, the diameter of each fuel nozzle ranges from 0.3 to 0.8 mm, and the oil-gas mixture in each of the aforementioned oil-gas premixing devices is in an oil-rich state with an oil-gas ratio of 0.5 to 1.2.

[0027] Preferably, in the fuel atomization, evaporation, and mixing section of the fuel-air premixing device, the fuel undergoes atomization, evaporation, and mixing under the action of the high-temperature, high-speed airflow of the high-pressure turbine gas to form a uniform fuel-air mixture. By optimizing the fuel-air ratio and the pipeline structure and dimensional parameters of the fuel-air premixing device, the residence time of the fuel-air mixture in the fuel-air premixing device is matched with its ignition delay time, so that the ratio of the ignition delay time of the fuel-air mixture to its residence time in the fuel-air premixing device is close to 1. This allows the fuel-air mixture to approach a self-ignition state when it is injected into the combustion zone, thereby improving the chemical reactivity of the fuel-air mixture.

[0028] Furthermore, the pipeline structure of the oil-gas premixing device adopts a multi-stage pipeline design with a small, gentle inclination angle to extend the flow distance of the oil-gas mixture. At the same time, the geometric dimensions of the flow channel of the oil-gas premixing device are optimized so that the oil-gas mixture flowing through the oil-gas premixing device obtains sufficient residence time, achieving precise matching with the ignition delay time.

[0029] Preferably, multiple air film cooling holes are evenly distributed circumferentially on each wall surface of the midstream section of the flame tube to guide a small amount of airflow from the outside to the inside to form a cooling air film to achieve cooling protection of the flame tube wall surface, and are optimized according to the working conditions and heat load distribution of the flame tube.

[0030] Furthermore, the aperture of each of the gas film cooling holes ranges from 0.6 to 1.2 mm, and the introduced cooling gas flow rate is optimized and controlled according to the working conditions and heat load distribution of the flame tube. This ensures that the cooling requirements of the flame tube wall are met while avoiding excessive cold gas inflow that could disrupt the combustion environment inside the flame tube.

[0031] Preferably, a plurality of mixing holes are evenly distributed around the periphery of the downstream wall section of the flame tube to guide some of the gas discharged from the high-pressure turbine into the downstream space of the flame tube from the outside to the inside, so that the space between the downstream wall section of the flame tube and the low-pressure turbine casing forms a mixing zone. The high-temperature combustion products generated in the combustion zone of the flame tube are mixed with the high-pressure turbine gas injected through the mixing holes in the mixing zone to optimize the gas temperature distribution and reduce the formation of local high-temperature areas.

[0032] Furthermore, the diameter of each of the mixing holes is in the range of 4-12 mm, and the high-pressure turbine gas introduced into each of the mixing holes accounts for 8%-20% of the total gas discharged from the high-pressure turbine, so as to achieve a mixing and cooling effect on the downstream of the combustion zone.

[0033] (III) Technical Effects

[0034] Compared with the prior art, the self-ignition and combustion-assisted ultra-compact interstage combustion chamber of the present invention has the following beneficial and significant technical effects:

[0035] (1) The self-ignition-assisted combustion ultra-compact interstage combustion chamber of the present invention, through the coupled design of oil-gas mixing and flow processes under high-temperature conditions, allows fuel droplets to rapidly evaporate and mix in the high-temperature combustion gas. Furthermore, by adjusting the flow residence time and self-ignition delay time of the oil-gas mixture in the mixing channel, its combustion chemical reactivity is improved, thereby increasing the chemical reaction rate, shortening the flame length, and improving combustion efficiency. The short flame not only reduces heat loss during transmission but also lowers the thermal load on the combustion chamber walls, thus extending the service life of the combustion chamber and reducing maintenance costs.

[0036] (2) The combustion chamber design of the present invention shortens the overall length of the combustion chamber by shortening the flame length, which directly leads to a reduction in the length of the engine shaft system. The short shaft system design not only reduces the weight of the engine, but also improves the rotor dynamics characteristics, thereby improving the overall performance and reliability of the engine. At the same time, the compact combustion chamber design can also leave more space for other components inside the engine, which helps to optimize the overall layout of the engine and improve the engine's maintainability.

[0037] (3) The combustion chamber design of this invention, by shortening the flame length, allows for more space to be reserved for regulating the combustion chamber outlet temperature distribution quality. This means that the downstream turbine can obtain more uniform intake conditions, thereby reducing the temperature gradient and local thermal stress caused by uneven temperature, extending the turbine's service life, and improving the overall reliability and economy of the engine. At the same time, uniform intake temperature also helps to improve turbine efficiency, further enhancing the engine's power output and performance. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the self-ignition and combustion-assisted ultra-compact interstage combustion chamber of the present invention.

[0040] Figure 2 A schematic diagram illustrating the working principle of an evaporator-based oil-gas premixing device for premixing and pre-evaporation.

[0041] Explanation of reference numerals in the attached figures:

[0042] 1-High-pressure turbine, 2-Fuel pipe, 3-Fuel nozzle, 4-Gas-fuel premixing device, 5-Transition section outer casing, 6-Flame tube, 7-Transition section inner casing, 8-Combustion zone, 9-Vortex airflow guide slot, 10-Mixing hole, 11-Mixing zone, 12-Low-pressure turbine, 13-Fuel atomization and evaporation mixing section, 14-Fuel cracking section. Detailed Implementation

[0043] To better understand the present invention, the following embodiments further illustrate its content. Throughout the accompanying drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions. The described embodiments are some, but not all, of the embodiments of the present invention. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. 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. The structure and technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings, providing one embodiment of the present invention.

[0044] To address the numerous shortcomings and deficiencies of existing turbine interstage combustors in practical applications, such as low operating pressure and high characteristic velocity due to space constraints, fuel atomization, evaporation, mixing, and limited combustion chemical reaction time, this invention proposes a self-igniting, ultra-compact interstage combustor to solve at least one of the aforementioned and other technical problems in the prior art. As a specific example, such as... Figure 1 , 2 As shown, the self-ignition and combustion-assisted ultra-compact interstage combustion chamber of the present invention includes an outer transition section casing 5, an inner transition section casing 7, a flame tube 6, and multiple oil-gas premixing devices 4.

[0045] In the ultra-compact interstage combustion chamber of the present invention, the transition section outer casing 5 is generally annular, with its front sidewall connected to the upstream high-pressure turbine casing and its rear sidewall connected to the downstream low-pressure turbine casing. Its radially outer sidewall has a structure that protrudes outward in the radial direction relative to the upstream high-pressure turbine casing and the downstream low-pressure turbine casing.

[0046] In the ultra-compact interstage combustion chamber of the present invention, the flame tube 6 is generally annular and is disposed in the annular space formed between the outer casing 5 and the inner casing 7 of the transition section, and is arranged radially adjacent to the outer casing 5 of the transition section. In the meridional direction, it sequentially includes an upstream tube wall section, a midstream tube wall section, and a downstream tube wall section. The shape of the upstream tube wall section is adapted to the high-pressure turbine casing and has a radial distance from it. The shape of the downstream tube wall section is adapted to the radial outer wall of the outer casing 5 of the transition section, with its upstream end fixedly connected to the midstream tube wall section and its downstream end fixedly connected to the low-pressure turbine casing. The midstream tube wall section includes a front sidewall, a rear sidewall, and a radial outer wall located between them. Its front sidewall is connected to the upstream tube wall section, and its rear sidewall is connected to the downstream tube wall section. Its radial outer wall has an outwardly protruding structure relative to the upstream and downstream tube wall sections, and this outwardly protruding structure forms the combustion zone 8 of the flame tube 6.

[0047] In the midstream section of the flame tube 6, multiple vortex airflow guiding slots 9 are evenly distributed circumferentially at the first connection between the upstream end of its radially outer sidewall and the top of its front sidewall, the second connection between the downstream end of its radially outer sidewall and the top of its rear sidewall, and the third connection between the bottom of its rear sidewall and the upstream end of the downstream section of the flame tube 6. Specifically, the vortex airflow guiding slots 9 located at the first connection are structurally configured to guide airflow radially inward toward the combustion chamber axis into the combustion zone of the flame tube 6; the vortex airflow guiding slots 9 located at the second connection are structurally configured to guide airflow radially inward toward the combustion zone of the flame tube 6 along a direction parallel to the radially outer sidewall of the midstream section of the flame tube 6; and the vortex airflow guiding slots 9 located at the third connection are structurally configured to guide airflow radially inward toward the combustion zone of the flame tube 6 along a direction opposite to the combustion chamber axis.

[0048] In the ultra-compact interstage combustion chamber of the present invention, several fuel-air premixing devices 4 are uniformly arranged circumferentially in the annular space between the outer casing 5 and the inner casing 7 of the transition section. Each fuel-air premixing device 4 is a tubular structure and includes a fuel atomization and evaporation mixing section 13 and a fuel cracking section 14 along its length. The fuel atomization and evaporation mixing section 13 is radially arranged on the outer side of the upstream cylinder wall section of the flame tube 6. Its inlet is roughly facing the direction of the high-temperature gas discharged from the high-pressure turbine, and a fuel nozzle 3 is provided on the pipe wall near its inlet. The fuel nozzle 3 is connected to the fuel pipe 2 of the external fuel supply device. The fuel cracking section 14 passes through the front side wall of the middle cylinder wall section of the flame tube 6 and extends into the combustion zone 8 of the flame tube 6. Its outlet extends spatially to a position near the first connection point.

[0049] In a preferred embodiment of the present invention, the proportion of high-pressure turbine gas entering the combustion zone 8 of the flame tube 6 to the total gas volume from the high-pressure turbine 1 is 20-60%, preferably 35%. The vortex airflow guiding hole slot 9 adopts a circumferentially distributed hole or slot structure, and the proportion of high-pressure turbine gas entering the vortex airflow guiding hole slot 9 is 10-40%, to ensure the formation of a strong swirling environment, ensure sufficient mixing of fuel and high-pressure turbine gas and stable flame combustion, and realize an efficient and stable secondary combustion process in the combustion zone.

[0050] In a preferred embodiment of the present invention, the number of oil-gas premixing devices 4 evenly arranged in the circumference is 10-30, preferably 16. The inner diameter d of each oil-gas premixing device 4 is 6-12 mm, preferably 8 mm. The inner diameter d of the fuel pipe 2 is 2-4 mm. The diameter d of the fuel nozzle 3 is 0.3-0.8 mm. The oil-gas mixture in the oil-gas premixing device 4 is in a rich oil state with an oil-gas ratio of 0.5-1.2 to ensure the uniform distribution and efficient combustion of the oil-gas mixture inside the flame tube 6.

[0051] In a preferred embodiment of the present invention, in the fuel atomization, evaporation, and mixing section 13 of the fuel-air premixing device 4, the fuel undergoes atomization, evaporation, and mixing under the action of the high-temperature, high-speed airflow of the high-pressure turbine gas to form a uniform fuel-air mixture. By optimizing the fuel-air ratio and the pipeline structure and dimensional parameters of the fuel-air premixing device 4, the residence time of the fuel-air mixture in the fuel-air premixing device 4 is matched with its ignition delay time, making the ratio of the ignition delay time to the residence time of the fuel-air mixture in the fuel-air premixing device 4 close to 1. This allows the fuel-air mixture to approach a self-ignition state when it is injected into the combustion zone 8, thereby improving the chemical reactivity of the fuel-air mixture. The pipeline structure of the fuel-air premixing device 4 preferably adopts a multi-stage pipeline design with a small, gentle inclination angle to extend the flow distance of the fuel-air mixture. At the same time, the geometric dimensions of the flow channel of the fuel-air premixing device 4 are optimized to ensure that the fuel-air mixture flowing through the fuel-air premixing device 4 obtains sufficient residence time, achieving precise matching with the ignition delay time.

[0052] In a preferred embodiment of the present invention, multiple film cooling holes are evenly distributed circumferentially on each wall surface of the midstream section of the flame tube 6. These holes guide a small amount of airflow from the outside in to form a cooling film, thereby achieving cooling and protection of the flame tube wall surface. The design is optimized based on the flame tube's operating conditions and heat load distribution. The diameter d of the film cooling holes on the flame tube 6 is 0.6-1.2 mm, and the introduced cooling airflow is optimized and controlled according to the flame tube's operating conditions and heat load distribution. This ensures that the cooling requirements of the flame tube wall surface are met while preventing excessive cold air inflow that could disrupt the combustion environment inside the flame tube.

[0053] In a preferred embodiment of the present invention, a plurality of mixing holes 10 are evenly distributed circumferentially around the downstream wall section of the flame tube 6. These holes guide a portion of the gas discharged from the high-pressure turbine 1 into the downstream space of the flame tube 6 from the outside in, thus forming a mixing zone between the downstream wall section of the flame tube 6 and the low-pressure turbine casing. The high-temperature combustion products generated in the combustion zone of the flame tube 6 are mixed with the high-pressure turbine gas injected through the mixing holes 10 within this mixing zone, thereby optimizing the gas temperature distribution and reducing the formation of localized high-temperature areas. The diameter d of the mixing holes is 4-12 mm, preferably 6 mm. The proportion of high-pressure turbine gas entering the mixing holes 10 is 8-20% of the total gas discharged from the high-pressure turbine 1, achieving a mixing and cooling effect downstream of the combustion zone.

[0054] The working principle of the self-ignition and combustion-assisted ultra-compact interstage combustion chamber of the present invention is as follows:

[0055] In order to achieve efficient afterburning in the transition section between the high and low pressure turbines 1 and 12 of the engine, the high-temperature gas enters the transition section after passing through the high-pressure turbine 1. The high-temperature gas is divided into two streams and enters the radial outer side and inner side of the transition section respectively. The high-temperature gas on the radial outer side enters the vortex combustion zone 8 through the oil-gas premixing device 4, the vortex airflow guide slot 9 and the gas film cooling holes on the wall of the flame tube 6. The air in the three vortex airflow guide slots 9 forms a counterclockwise swirling flow in the vortex combustion zone 8, forming a local low-speed zone, which increases the air residence time on the one hand and the combustion stability on the other. Fuel is supplied to the fuel injector 3 via fuel pipe 2. Under the action of high-temperature, high-speed airflow, the fuel is atomized, evaporated, and mixed, forming a uniform fuel-air mixture in the fuel-air premixing device 4. The ratio of the ignition delay time of the fuel-air mixture to its residence time in the fuel-air premixing device 4 is close to 1. The fuel-air ratio is adjusted to bring the fuel-air mixture in the fuel-air premixing device 4 closer to an auto-ignition state, increasing its chemical reactivity. The highly chemically active fuel-air mixture ejected from the fuel-air premixing device 4 undergoes rapid combustion in the vortex combustion zone 8, shortening the flame length. The higher-temperature combustion gas that has completed secondary combustion mixes with the high-temperature combustion gas radially inner side of the transition section. Further cooling and mixing through the mixing orifice further improves the outlet temperature distribution quality before finally entering the low-pressure turbine to perform power. Film cooling holes are provided on the flame tube wall for cooling and protection of the flame tube. The short flame formed in the vortex combustion zone can improve combustion efficiency and solve the problem of low combustion efficiency in the confined transition section. On the other hand, the short flame allows sufficient time for the gas at different temperatures on the radial inner and outer sides of the transition section to mix, improving the temperature distribution quality at the outlet of the interstage combustion chamber and thus increasing turbine life.

[0056] The objectives of this invention have been fully and effectively achieved through the above embodiments. Those skilled in the art will understand that this invention includes, but is not limited to, the contents described in the accompanying drawings and the specific embodiments described above. Although the invention has been described with reference to what is currently considered the most practical and preferred embodiments, it should be understood that the invention is not limited to the disclosed embodiments, and any modifications that do not depart from the functional and structural principles of the invention will be included within the scope of the claims.

Claims

1. A self-igniting, ultra-compact interstage combustion chamber for achieving efficient afterburning in the transition section between high-pressure and low-pressure turbines of an aero-engine, comprising an outer transition section casing, an inner transition section casing, a flame tube, and several fuel-air premixing devices, wherein the outer and inner transition section casings are located in the meridional direction between the high-pressure and low-pressure turbines, characterized in that... The outer casing of the transition section is generally annular, with its front sidewall connected to the upstream high-pressure turbine casing and its rear sidewall connected to the downstream low-pressure turbine casing. Its radially outer sidewall protrudes outward relative to the upstream high-pressure turbine casing and the downstream low-pressure turbine casing. The flame tube is generally annular and is disposed within the annular space formed between the outer casing and the inner casing of the transition section. It is radially adjacent to the outer casing and, in the meridional direction, sequentially includes an upstream tube wall section, a midstream tube wall section, and a downstream tube wall section. The upstream cylindrical wall section is shaped to fit the high-pressure turbine casing and has a radial distance between it and the high-pressure turbine casing. The downstream cylindrical wall section is shaped to fit the radial outer wall of the transition section outer casing, with its upstream end fixedly connected to the midstream cylindrical wall section and its downstream end fixedly connected to the low-pressure turbine casing. The midstream cylindrical wall section includes a front sidewall, a rear sidewall, and a radially outer sidewall located between the two. Its front sidewall connects to the upstream cylindrical wall section, and its rear sidewall connects to the downstream cylindrical wall section. The radially outer sidewall protrudes outward relative to both the upstream and downstream cylindrical wall sections, and this outward protrusion forms the combustion zone of the flame tube. Furthermore, in the midstream cylindrical wall section, multiple vortex airflow guiding slots are evenly distributed circumferentially at the first connection between the upstream end of its radially outer sidewall and the top of its front sidewall, the second connection between the downstream end of its radially outer sidewall and the top of its rear sidewall, and the third connection between the bottom of its rear sidewall and the upstream end of the downstream cylindrical wall section. The vortex airflow guide slots located at the first connection are structurally configured to guide the airflow radially in a direction toward the combustion chamber axis, from the outside to the combustion zone of the flame tube. The airflow guide slots of each vortex system located at the second connection are structurally designed to guide the airflow from the outside to the inside into the combustion zone of the flame tube in a manner parallel to the radial outer wall of the midstream cylinder section. The vortex airflow guide slots located at the third connection are structurally configured to guide the airflow radially in a direction opposite to the combustion chamber axis to be injected from the outside to the combustion zone of the flame tube; The plurality of oil-gas premixing devices are evenly arranged circumferentially within the annular space between the outer casing and the inner casing of the transition section. Each of the oil-gas premixing devices is a tubular structure, and along its length includes a fuel atomization and evaporation mixing section and a fuel cracking section. The fuel atomization and evaporation mixing section is radially arranged on the outer side of the upstream section of the flame tube. Its inlet is roughly aligned with the direction of the high-temperature combustion gas discharged from the high-pressure turbine, and a fuel nozzle is provided on the pipe wall near its inlet. The fuel nozzle is connected to the fuel pipe of an external fuel supply device. The fuel cracking section passes through the front sidewall of the midstream section of the flame tube and extends into the combustion zone of the flame tube, with its outlet end extending spatially to a position near the first connection point.

2. The self-ignition and combustion-assisted ultra-compact interstage combustion chamber according to claim 1, characterized in that, The high-pressure turbine gas entering the combustion zone of the flame tube accounts for 20%-60% of the total gas volume discharged from the high-pressure turbine. The proportion of high-pressure turbine gas entering the combustion zone through the airflow guide slots of each vortex system is controlled at 10%-40% to ensure the formation of a strong swirling environment, guarantee the full mixing of fuel and high-pressure turbine gas and stable flame combustion, and realize an efficient and stable secondary combustion process in the combustion zone.

3. The self-ignition and combustion-assisted ultra-compact interstage combustion chamber according to claim 1, characterized in that, The number of oil-gas premixing devices is 10-30, evenly arranged in the circumference, to ensure uniform distribution and efficient combustion of the oil-gas mixture inside the flame tube.

4. The self-ignition and combustion-assisted ultra-compact interstage combustion chamber according to claim 3, characterized in that, The inner diameter of each of the aforementioned oil-gas premixing devices ranges from 6 to 12 mm, the inner diameter of each of the aforementioned fuel pipes ranges from 2 to 4 mm, the diameter of each fuel nozzle ranges from 0.3 to 0.8 mm, and the oil-gas mixture in each of the aforementioned oil-gas premixing devices is in a rich oil state with an oil-gas ratio of 0.5 to 1.

2.

5. The self-ignition and combustion-assisted ultra-compact interstage combustion chamber according to claim 1, characterized in that, In the fuel atomization, evaporation, and mixing section of the fuel-air premixing device, fuel undergoes atomization, evaporation, and mixing under the action of high-temperature, high-speed airflow from the high-pressure turbine gas to form a uniform fuel-air mixture. By optimizing the fuel-air ratio and the pipeline structure and dimensional parameters of the fuel-air premixing device, the residence time of the fuel-air mixture in the device is matched with its ignition delay time, making the ratio of the ignition delay time to the residence time close to 1. This allows the fuel-air mixture to approach a self-ignition state when it is injected into the combustion zone, thereby improving the chemical reactivity of the fuel-air mixture.

6. The self-ignition and combustion-assisted ultra-compact interstage combustion chamber according to claim 5, characterized in that, The pipeline structure of the oil-gas premixing device adopts a multi-stage pipeline design with a small, gentle inclination angle to extend the flow distance of the oil-gas mixture. At the same time, the geometric dimensions of the flow channel of the oil-gas premixing device are optimized so that the oil-gas mixture flowing through the oil-gas premixing device obtains sufficient residence time, achieving precise matching with the ignition delay time.

7. The self-ignition and combustion-assisted ultra-compact interstage combustion chamber according to claim 1, characterized in that, Multiple air film cooling holes are evenly distributed circumferentially on each wall surface of the midstream section of the flame tube. These holes are used to guide a small amount of airflow from the outside to the inside to form a cooling air film, thereby achieving cooling and protection of the flame tube wall surface. The design is optimized according to the working conditions and heat load distribution of the flame tube.

8. The self-ignition and combustion-assisted ultra-compact interstage combustion chamber according to claim 7, characterized in that, The diameter of each of the gas film cooling holes ranges from 0.6 to 1.2 mm, and the flow rate of the introduced cooling gas is optimized and controlled according to the working conditions and heat load distribution of the flame tube. This ensures that the cooling requirements of the flame tube wall are met while avoiding excessive cold air inflow that could disrupt the combustion environment inside the flame tube.

9. The self-ignition and combustion-assisted ultra-compact interstage combustion chamber according to claim 1, characterized in that, The downstream wall section of the flame tube is provided with multiple mixing holes evenly distributed around its periphery. These holes guide some of the gas discharged from the high-pressure turbine into the downstream space of the flame tube from the outside to the inside. This creates a mixing zone between the downstream wall section of the flame tube and the low-pressure turbine casing. The high-temperature combustion products generated in the combustion zone of the flame tube are mixed with the high-pressure turbine gas injected through the mixing holes in the mixing zone to optimize the gas temperature distribution and reduce the formation of local high-temperature areas.

10. The self-ignition and combustion-assisted ultra-compact interstage combustion chamber according to claim 9, characterized in that, The diameter of each mixing hole ranges from 4 to 12 mm, and the high-pressure turbine gas introduced into each mixing hole accounts for 8% to 20% of the total gas discharged from the high-pressure turbine, so as to achieve a mixing and cooling effect on the downstream of the combustion zone.

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