Retrofitted combustion chamber flame tube outer ring assembly

Abstract

This application discloses an outer ring assembly for a recirculating combustor flame tube, belonging to the field of gas turbine recirculating combustors. It includes an outer ring body for connection to an inner ring assembly; a large bend outer wall connected to the outer ring body, with multiple impact holes distributed on the large bend outer wall, and a first floating connection structure at the end of the large bend outer wall; and a large bend inner wall connected to the outer ring body, with a second floating connection structure at the end of the large bend inner wall away from the outer ring body, and multiple divergence holes distributed on the large bend inner wall. A divergence cavity is formed between the large bend outer wall and the large bend inner wall, with the divergence holes and impact holes misaligned. The first and second floating connection structures are clearance-fitted to compensate for the thermal deformation differences between the large bend outer wall and the large bend inner wall. This application improves the wall temperature distribution of the flame tube outer ring assembly and ensures structural stability during long-term operation, thereby extending the assembly's service life and improving overall operational reliability.

Description

Technical Field

[0001] This application relates to the field of gas turbine recirculation combustors, specifically to the outer ring assembly of the flame tube of a recirculation combustor. Background Technology

[0002] The recirculation combustion chamber of a gas turbine engine typically employs a structure consisting of an outer ring assembly and an inner ring assembly. The outer ring assembly generally comprises an outer ring cylinder and a large bend assembly. In existing technologies, film cooling air is often introduced into the combustion chamber through film cooling holes in the combustion chamber wall, forming a film layer on the wall to isolate it from the direct impact of the high-temperature combustion gases. While this structure can reduce wall temperature to some extent, the relatively simple arrangement of the film cooling holes results in uneven circumferential and axial cooling airflow coverage, often leading to excessively high local wall temperatures and large temperature gradients. This can easily cause cracks, ablation, and other failures, becoming a significant factor limiting the lifespan of the combustion chamber.

[0003] Meanwhile, in the large bend area of ​​the recirculation combustion chamber, the outer wall is typically located on the cold air side, while the inner wall is directly exposed to the high-temperature combustion gas. The temperature conditions experienced by these two components during operation differ significantly, resulting in inconsistent thermal deformation. Most existing outer ring assembly structures use an integral connection to fix the inner and outer walls of the large bend. Under long-term high-temperature cycling conditions, this difference in deformation between the inner and outer walls can easily lead to stress concentration, thus affecting the long-term stability and reliability of the combustion chamber. Summary of the Invention

[0004] This application provides a recirculation combustion chamber flame tube outer ring assembly to solve the technical problem of uneven wall temperature distribution and thermal deformation failure of the flame tube outer ring assembly.

[0005] According to one aspect of this application, a recirculation combustion chamber flame tube outer ring assembly is provided, comprising an outer ring body for connection to an inner ring assembly of the flame tube; a large bend tube outer wall connected to the outer ring body, wherein the end of the large bend tube outer wall away from the outer ring body is connected to a centrifugal impeller cover, the large bend tube outer wall has a plurality of impact holes distributed thereon, and the end of the large bend tube outer wall is provided with a first floating connection structure; a large bend tube inner wall connected to the outer ring body, the end of the large bend tube inner wall away from the outer ring body is provided with a second floating connection structure, the large bend tube inner wall has a plurality of divergence holes distributed thereon; a divergence cavity is formed between the large bend tube outer wall and the large bend tube inner wall, the divergence holes and the impact holes are staggered to form a cooling airflow channel along the impact holes, the divergence cavity, and the divergence holes; the first floating connection structure and the second floating connection structure are clearance-fitted to compensate for the thermal deformation difference between the large bend tube outer wall and the large bend tube inner wall.

[0006] Optionally, the first floating connection structure includes a first vertical plate and two first horizontal plates, with a first horizontal plate connected to each end of the first vertical plate to form a first opening groove; the second floating connection structure includes a second vertical plate and two second horizontal plates, with a second horizontal plate connected to each end of the second vertical plate to form a second opening groove; the first opening groove and the second opening groove have opposite opening directions and fit together, so that there is a radial gap between the first horizontal plate and the second horizontal plate, and there is an axial gap between the first vertical plate and the second horizontal plate and between the second vertical plate and the first horizontal plate, and the radial gap and the axial gap together form a labyrinthine zigzag channel.

[0007] Optionally, the axis of the impact hole is perpendicular to the heated wall surface of the inner wall of the large bend, so that the cooling airflow directly impacts the heated wall surface of the inner wall of the large bend. The axis of the diverging hole is inclined at a certain angle relative to the heated wall surface of the inner wall of the large bend, so that the ejected cooling airflow spreads along the heated wall surface to form an air film cooling layer.

[0008] Optionally, the projections of the impact holes on the inner wall of the large bend and the diverging holes are arranged alternately along the axial and circumferential directions, with the holes in adjacent rows being staggered to form a differential arrangement.

[0009] Optionally, the hot air flow initiation section of the outer ring cylinder is uniformly provided with initial gas film holes along the circumference. The initial gas film holes are used to spray cooling air flow when the combustion chamber is working, forming an initial cooling film layer on the wall surface of the outer ring cylinder.

[0010] Optionally, a guide plate is provided at the outlet position of the initial film gas hole in the outer ring cylinder. The guide plate is used to guide the cooling airflow ejected from the initial film gas hole to flow along the outer ring cylinder wall.

[0011] Optionally, the outer ring assembly of the flame tube is provided with a multi-stage stepped structure along the axial direction, and each stage is provided with secondary air film holes distributed circumferentially. The secondary air film holes are used to introduce cooling airflow step by step.

[0012] Optionally, the multi-stage stepped structure includes a first-stage step, a second-stage step, and a third-stage step. The secondary air film holes include a primary air film hole set on the first-stage step, a secondary air film hole set on the second-stage step, and a tertiary air film hole set on the third-stage step. The injection angles of the primary, secondary, and tertiary air film holes increase progressively.

[0013] Optionally, the pore size of the secondary air film pores is positively correlated with the magnitude of the temperature gradient in the region.

[0014] Optionally, the outer wall of the large bend is connected to the outer ring cylinder by a weld, which is used to replace the outer wall of the large bend separately after grinding the weld when the outer wall of the large bend is damaged.

[0015] In summary, this application includes at least one of the following beneficial technical effects:

[0016] This solution incorporates impact holes on the outer wall of the large bend and divergence holes on the inner wall, forming a divergence cavity between them. This allows cooling airflow to sequentially pass through the impact holes into the divergence cavity and then adhere to the inner wall surface through the divergence holes. This creates a cooling channel on the inner wall of the outer ring assembly of the flame tube, providing both localized reinforcement and overall coverage. This effectively avoids the localized overheating problem caused by uneven cooling airflow distribution in existing technologies, resulting in a more uniform wall temperature along the circumferential and axial directions. Simultaneously, a first floating connection structure is provided at the end of the outer wall of the large bend, and a second floating connection structure is provided at the end of the inner wall, with a clearance fit between them. This allows the different thermal deformations generated by the outer and inner walls under high-temperature conditions to be absorbed and coordinated, preventing stress concentration and structural cracking caused by deformation differences. Through the combination of the above-mentioned cooling airflow organization and floating connection structures, this invention improves the wall temperature distribution of the outer ring assembly of the flame tube and ensures structural stability during long-term operation, thereby extending the service life of the assembly and improving overall operational reliability.

[0017] In addition to the purposes, features, and advantages described above, this application has other purposes, features, and advantages. A further detailed description of this application will be provided below with reference to the figures. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0019] Figure 1 This is a schematic diagram of the structure of the outer ring assembly of the recirculation combustion chamber flame tube in this application;

[0020] Figure 2 This is a schematic diagram illustrating the cooperation between the first floating connection structure and the second floating connection structure of this application;

[0021] Figure 3 This is a schematic diagram showing the distribution of the diverging holes and impact holes in this application;

[0022] Figure 4 This is a schematic diagram showing the distribution of the secondary air film pores in this application;

[0023] Figure 5 A schematic diagram showing the different aperture sizes set in different regions of the secondary air film pores in this application.

[0024] Legend:

[0025] 1. Outer ring cylinder; 101. Outer ring cylinder flange; 102. Support pin hole; 103. Initial air film hole; 104. First-stage air film hole; 105. Second-stage air film hole; 106. Third-stage air film hole; 1041. Standard hole; 1042. Enlarged hole; 2. Outer wall of the large bend; 201. Outer wall flange of the large bend; 202. Weld; 203. First floating connection structure; 204. Impact hole; 3. Inner wall of the large bend; 301. Second floating connection structure; 302. Diverging hole; 303. Fourth-stage air film hole. Detailed Implementation

[0026] The embodiments of this application are described in detail below with reference to the accompanying drawings; however, this application may be implemented in a variety of different ways as defined and covered below.

[0027] The following is in conjunction with the appendix Figure 1-5 This application will be described in further detail.

[0028] This embodiment discloses an outer ring assembly for a recirculating combustion chamber flame tube. For example... Figure 1 As shown, the component mainly includes an outer ring cylinder 1, a large bend outer wall 2, a large bend inner wall 3, and a floating connection structure.

[0029] The outer annular cylinder 1 is used to connect with the inner annular assembly of the combustion chamber's flame tube, and the two together define the combustion flow path of the combustion chamber. The outer annular cylinder 1 has a circular shell structure and is provided with an installation interface for reliable connection with the engine casing, inner annular assembly, and other auxiliary components. Its main body material is typically a high-temperature alloy, capable of withstanding the heat load from the combustion gas scouring and providing an installation reference.

[0030] One end of the outer wall 2 of the large bend is connected to the outer ring cylinder 1, and the other end extends toward the centrifugal impeller cover to guide air into the combustion chamber. Multiple impact holes 204 are arranged circumferentially and axially on the outer wall, providing inlet channels for subsequent cooling airflow. To ensure structural stability under high-temperature conditions, a first floating connection structure 203 is also provided at the end of the outer wall to cooperate with the floating structure of the inner wall.

[0031] The inner wall 3 of the large bend is also connected to the outer ring cylinder 1 and is located on the side of the high-temperature combustion gas. A second floating connection structure 301 is provided at the end of the inner wall away from the outer ring cylinder 1. Multiple diverging holes 302 are evenly distributed on the inner wall surface to guide cooling air to the wall surface and spread along it, forming a protective gas film layer. Since the inner wall directly bears the radiation and scouring of the high-temperature combustion gas, it is one of the components with the highest heat load in the outer ring assembly of the flame tube, and its cooling effect directly affects the lifespan and reliability of the combustion chamber.

[0032] An annular diffusion cavity is defined between the outer and inner walls. The impact holes 204 and diffusion holes 302 are staggered in the circumferential and axial directions, allowing the cooling airflow to first enter the diffusion cavity through the impact holes 204, then exit through the diffusion holes 302 and adhere to the inner wall surface, thus forming a cooling airflow channel that sequentially passes through the impact holes 204, the diffusion cavity, and the diffusion holes 302. This airflow organization method ensures continuous coverage of the cold air on the wall surface while also taking into account both local enhancement and overall uniform distribution.

[0033] To address the issue of differing thermal deformation between the outer wall 2 and the inner wall 3 of the large bend during operation, a clearance fit is used between the first floating connection structure 203 at the outer wall end and the second floating connection structure 301 at the inner wall end. This clearance fit ensures a secure connection while allowing limited relative displacement between the inner and outer walls. Furthermore, the zigzag joint interface maintains airtightness, preventing stress concentration caused by thermal deformation differences and ensuring structural stability during long-term operation. Through this design, the outer ring assembly of the flame tube achieves uniform cooling airflow coverage on the combustion chamber wall, preventing localized high temperatures and cracks caused by uneven cooling. Simultaneously, the clearance fit of the floating connection structure ensures stable and coordinated operation of the inner and outer walls under long-term high-temperature conditions, thereby improving wall temperature distribution, reducing the risk of structural failure, extending service life, and enhancing overall operational reliability.

[0034] The front end of the outer ring assembly of the flame tube is bolted to the inner ring assembly of the flame tube via bolt holes on the outer ring flange 101. When either the outer or inner ring assembly of the flame tube fails independently due to localized cracks or ablation under high-temperature conditions, the failed component can be disassembled and replaced individually without replacing the entire combustion chamber structure, thus significantly reducing maintenance costs and improving maintenance efficiency. The outer ring assembly is supported in the combustion chamber by inserting support pins into the support pin holes 102 provided on its wall, reliably fixing the assembly to the combustion chamber casing and ensuring the stability and concentricity of the flame tube during engine operation. Simultaneously, the rear end of the inner ring assembly of the flame tube is bolted to the centrifugal impeller cover via bolt holes on the outer flange 201 of the large bend, forming a stable assembly structure at both ends. Through the above connection method, the inner and outer ring assemblies of the flame tube maintain overall airtightness and structural strength while possessing good disassembly and maintainability, ensuring reliable operation and convenient maintenance of the combustion chamber during long-term service.

[0035] Reference Figure 2In one embodiment, a first floating connection structure 203 is formed at the end of the outer wall 2 of the large bend, and a second floating connection structure 301 is formed at the end of the inner wall 3 of the large bend. The two structures are interlocked during assembly, with gaps reserved in the axial and radial directions. Through this floating connection, the outer wall 2 and the inner wall of the large bend can maintain a stable connection during combustion chamber operation while allowing for a certain degree of relative displacement.

[0036] The first floating connection structure 203 consists of a vertically extending first vertical plate and two first horizontal plates at its ends. The first vertical plate and the two horizontal plates together form an open slot structure, with the slot opening facing the inner wall. The configuration of the second floating connection structure 301 is similar to that of the first floating connection structure 203, consisting of a second vertical plate and two second horizontal plates at its ends. The second vertical plate and the two horizontal plates also form an open slot, but its slot opening faces the outer wall. In this way, the first and second open slots have opposite opening directions during assembly, enabling them to be interlocked and nested.

[0037] In the fitted state, a radial gap exists between the first and second horizontal plates, and axial gaps exist between the first and second vertical plates, as well as between the second vertical plate and the first horizontal plate. These gaps work together in three dimensions, making the connection between the outer and inner walls no longer completely rigid, but possessing a certain degree of flexibility, capable of absorbing relative deformation caused by temperature differences while maintaining overall assembly accuracy. Furthermore, because the first and second opening slots are geometrically interlocked, the radial and axial gaps together form a zigzag channel, i.e., a labyrinthine zigzag channel. When the combustion chamber is operating, cold and hot air cannot leak directly through the connecting gaps, but instead form multiple deflections within the channel, thus significantly improving airtightness. This structure not only ensures the efficient utilization of cooling airflow but also avoids the adverse effects on combustion stability caused by gap leakage.

[0038] Through the above design, the floating connection structure achieves a balance between strong connection, reliable sealing, and adaptability to thermal deformation. On the one hand, the outer and inner walls will not experience excessive stress concentration due to inconsistent expansion under long-term high-temperature cycling conditions, thus avoiding cracks and weld 202 cracking. On the other hand, the labyrinthine zigzag channel ensures sufficient sealing effect, preventing unexpected crossflow of cold and hot air and ensuring the normal operation of the cooling system.

[0039] In one embodiment, the axis of each impact hole 204 is perpendicular to the heated wall surface of the inner wall 3 of the large bend. Cooling air enters the impact hole 204 from the cold air side of the outer wall and is then sprayed at high speed onto the inner wall surface in a nearly orthogonal direction, thereby creating an impact cooling effect in the area where the heat is most concentrated. The high-speed jet can enhance local heat transfer, rapidly reduce the wall temperature, and avoid the formation of local hot spots. Depending on the heat load distribution, several to several hundred impact holes 204 can be arranged around the outer wall 2 of the large bend in the circumference. The specific number is determined according to the engine model and the cold air flow rate, and they are usually evenly distributed within every 360° circumferential range to ensure the continuity of the cooling effect.

[0040] Multiple diverging holes 302 are evenly distributed on the inner wall 3 of the large bend. The axis of these diverging holes 302 is inclined at a certain angle relative to the heated inner wall surface. In this embodiment, the inclined angle is preferably 15°~45°, so that the cold air can stably adhere to the wall surface and spread along the longitudinal direction after being ejected, forming a continuous air film layer. The number of diverging holes 302 corresponds to the number of impact holes 204, and they are also evenly arranged in the circumferential direction. The number of holes in each ring is usually similar to that of the impact holes 204 to ensure that the cold air flow is evenly distributed in the circumferential direction. Since the diverging holes 302 mainly serve the function of air film coverage, their diameter is generally slightly larger than that of the impact holes 204, so that the ejected cold air can form a stable coverage on the wall surface.

[0041] Reference Figure 3 In one embodiment, the projection positions of the impact holes 204 on the outer wall 2 of the large bend and the diverging holes 302 on the inner wall 3 of the large bend do not coincide. Instead, they are arranged in a staggered manner along the axial and circumferential directions. Specifically, when viewed from the inner wall surface, the projections of the impact holes 204 and the arrangement of the diverging holes 302 are misaligned. The centers of adjacent rows of holes are not on the same straight line but are relatively offset, thus forming a differential arrangement in the circumferential and axial directions. The differential arrangement requires that adjacent rows of cooling holes be offset from each other in the axial and / or circumferential directions, so that adjacent three holes roughly form a triangular distribution. This arrangement is similar to the form of brick wall construction, that is, the holes in the upper and lower rows are not completely aligned, but are offset by about half a hole distance. Through this staggered distribution, the coverage areas of the cooling air on the wall surface after injection can overlap, reducing the gaps between the cooling airflows and avoiding discontinuous film cooling or local dead zones.

[0042] The advantage of this arrangement is that the high-speed cold air ejected from the impact holes 204 can create forced scouring in local areas, while the gaps are covered by the cold air ejected from the adjacent diverging holes 302 along the wall surface. The two airflows complement each other in space, avoiding discontinuities and dead zones in the distribution of cooling airflow. Through differential arrangement, the cooling airflow forms a grid-like coverage effect on the inner wall surface, combining local and overall cooling effects, thereby significantly improving the wall temperature distribution.

[0043] To further enhance cooling performance, the staggered arrangement can be optimized based on the heat load distribution in local areas. In high heat flux regions, the spacing between holes can be appropriately reduced or the number of radiating holes 302 can be increased to make the air film denser. In low heat flux regions, the conventional arrangement can be maintained to save cooling airflow and thus improve the overall cooling efficiency.

[0044] In actual manufacturing, the staggered arrangement of impact holes 204 and diverging holes 302 is achieved through precision drilling, laser drilling, or electrical discharge machining. Since the holes in each row need to maintain a staggered relationship, specialized tooling or CNC positioning is required during machining to ensure that the staggered spacing between adjacent holes meets design requirements. After machining, a cold airflow distribution experiment should be conducted to verify whether the staggered arrangement can achieve uniform airflow coverage. By staggering the impact holes 204 and diverging holes 302 along the axial and circumferential directions and offsetting adjacent rows of holes, this embodiment forms a differentially arranged cooling hole array on the inner wall 3 of the large bend. This arrangement ensures the mutual complementarity of impact cooling and film cooling, enabling continuous and uniform coverage and distribution of cooling airflow on the wall surface, thereby reducing local temperature gradients, minimizing the risk of cracking and ablation, and significantly improving the lifespan and operational reliability of the outer ring assembly of the flame tube.

[0045] In one embodiment, the outer annular cylinder 1 has a plurality of initial film gas holes 103 evenly arranged circumferentially in the initial section of the hot gas flow. The initial section of the hot gas flow refers to the inlet area where the high-temperature combustion gas in the combustion chamber just enters the outer annular assembly of the flame tube. At this location, the wall surface is directly exposed to the initial impact of the high-temperature combustion gas, resulting in concentrated heat load and drastic temperature fluctuations. Without effective cooling, high-temperature ablation and thermal fatigue damage are very likely to occur at this location.

[0046] The initial film cooling holes 103 are basically evenly distributed in the circumferential direction, with dozens or even hundreds of small holes in each ring. The hole diameter is generally controlled within the range of 1.0~1.5mm to ensure that sufficient cooling air can enter the wall surface without significantly affecting the mainstream air supply. After the cooling air is ejected through these initial film cooling holes 103, it forms an initial cooling film layer along the inner wall surface of the outer ring cylinder 1. This film can cover the wall surface at the beginning of combustion, blocking the direct impact of high-temperature combustion gases, thereby establishing basic cooling protection in the entire outer ring assembly.

[0047] Reference Figure 1In one embodiment, a guide plate is provided at the outlet position of the initial film cooling orifice 103. The guide plate is arranged close to the inner wall of the outer annular cylinder 1, and its shape can be a small stepped protrusion, a sheet-like structure, or an arc-shaped guiding surface, the specific form of which is determined according to the cold air flow characteristics and wall structure. The main function of the guide plate is to change the initial flow direction of the cooling airflow after injection, guiding the cold air to adhere to the wall of the outer annular cylinder 1. Since the airflow ejected from the initial film cooling orifice 103 has a high velocity, if it is directly sprayed onto the wall, some airflow is prone to detach from the wall and enter the main combustion flow due to excessive momentum, resulting in a decrease in cold air utilization efficiency and possibly forming a cooling dead zone in a local area. By adding a guide plate at the orifice outlet position, a buffer and transition can be formed between the ejected airflow and the high-temperature mainstream, allowing the cold air to extend longitudinally along the wall and enhancing the adhesion and stability of the film cooling system.

[0048] In one embodiment, the outer ring assembly of the flame tube is provided with a multi-stage stepped structure along the axial direction. This stepped structure is formed by the outer ring body 1 gradually contracting or expanding at different axial positions, with each step constituting a relatively independent cooling distribution section. This stepped design allows for segmented cooling channels to be formed in different axial regions of the flame tube wall, making the introduction of cooling airflow more regular and targeted. Several secondary film cooling holes are evenly distributed on the wall surface of each step. These secondary film cooling holes are distributed circumferentially, with dozens or even hundreds arranged in a circle; the specific number is determined based on the circumferential length of the step and the required cooling airflow. After the cooling air is injected into the combustion chamber through the secondary film cooling holes, it spreads along the wall surface, gradually covering the wall surface where the heat load is concentrated. Thus, as the airflow gradually enters the combustion chamber axially, the steps at different positions can sequentially provide new cooling airflow, increasing the cooling effect segment by segment from front to back.

[0049] Reference Figure 1 and Figure 4 In one embodiment, the multi-stage stepped structure includes a first-stage step, a second-stage step, and a third-stage step, as well as secondary-stage film cooling holes 104, secondary-stage film cooling holes 105, and tertiary-stage film cooling holes 106. The injection angles of the primary-stage film cooling holes 104, secondary-stage film cooling holes 105, and tertiary-stage film cooling holes 106 increase progressively. Specifically, primary-stage film cooling holes 104 are uniformly arranged on the first-stage step, and these holes have relatively small injection angles. After the cooling air is ejected from the primary-stage film cooling holes 104, it flows longitudinally close to the wall surface, forming an initial film cooling layer. Since this location is close to the initial combustion section, the gas flow velocity is low and the turbulence is limited. The smaller injection angle helps the cold air to stably adhere to the wall, preventing the film cooling layer from detaching prematurely under the influence of the high-temperature mainstream.

[0050] Secondary film gas holes 105 are evenly distributed on the second-stage step, with injection angles greater than those of the primary film gas holes 104. As the combustion gas flows further in the combustion chamber, its velocity and turbulence intensity gradually increase, and the primary film gas layer is partially consumed and attenuated. At this point, new cooling airflow is introduced through the secondary film gas holes 105 to cover the wall at a larger angle, effectively compensating for the loss of the previous film gas layer and enhancing cooling in the middle section. Tertiary film gas holes 106 are evenly distributed on the third-stage step, with injection angles further increased, exceeding those of the secondary film gas holes 105. Here, the combustion gas temperature and velocity have increased, making the film gas layer more susceptible to erosion by the high-temperature mainstream during wall adhesion. By increasing the injection angle, the cool air can spread more intensely, thereby enhancing the coverage of the film gas in the downstream section and ensuring continuous protection of the wall. The step height and the number of film gas holes in the three-stage step are designed and optimized based on the combustion chamber size and heat flow distribution. Generally, the film cooling holes on each step are evenly distributed circumferentially, with dozens to hundreds of small holes per circumference to ensure a uniform supply of cooling air. The hole diameter and spacing between different steps can be adjusted appropriately to achieve a balance between cooling intensity and cooling air utilization efficiency. For example, the diameter of the first-stage film cooling hole 104 can be relatively small to ensure the cooling air jet velocity; while the diameter of the third-stage film cooling hole 106 can be slightly larger to supplement more airflow in the downstream area.

[0051] Through the above design, this embodiment forms a multi-stage cooling system in the outer ring assembly of the flame tube, with primary, secondary, and tertiary film cooling orifices 106 acting sequentially. The injection angle of the film cooling orifices increases progressively along the axial direction, which can adapt to the characteristics of the gas flow rate and heat load gradually increasing from upstream to downstream, ensuring that the film cooling layer has good wall adhesion and coverage throughout the entire process. This structure effectively improves the uniformity of wall temperature distribution, reduces the risk of thermal fatigue and ablation caused by local overheating, and improves the service life and reliability of the combustion chamber.

[0052] Reference Figure 5 In one implementation, the secondary air film pores on the multi-stage stepped structure are not only optimized in terms of angle and position, but their aperture size is also differentiated according to the temperature gradient of the area. The temperature gradient refers to the range of temperature variation on the wall surface per unit area. If the wall surface temperature difference is large in a certain area, it indicates that the heat load is concentrated and the cooling effect is insufficient, requiring an increase in cooling airflow to enhance cooling.

[0053] Therefore, in this embodiment, the pore size of the secondary air film vents is positively correlated with the wall temperature gradient. Specifically, when the temperature gradient in a certain area is small, the pore size is designed to be a standard size, for example, the standard 1041 pore size is 1.0-1.2 mm, to ensure normal cooling requirements; when the temperature gradient exceeds a preset threshold (e.g., 80℃ / cm²), the pore size is adjusted accordingly. 2When the secondary air film pore diameter in this area is appropriately increased to form an enlarged pore 1042 with a diameter of 1.5-2.0 mm, the injection cooling air flow rate can be increased, thereby effectively reducing the local wall temperature.

[0054] This differentiated orifice allocation method enables more rational utilization of cooling airflow. In areas with a large wall temperature gradient, larger orifices provide more cooling air replenishment, preventing localized hot spots; while in areas with relatively low heat load, smaller orifices ensure that cooling air is not excessively consumed, thereby improving cooling efficiency and overall aerodynamic performance. In practical implementation, orifice design needs to be optimized by combining computational fluid dynamics (CFD) simulations and engine test data. By monitoring the wall temperature distribution in different areas of the combustion chamber, a correspondence between temperature gradient and orifice setting is established. During manufacturing, processes such as laser drilling and electrical discharge machining can be used to precisely control the diameter of each orifice according to design requirements. After processing, the cooling air flow rate needs to be tested orifice by orifice to ensure that the orifice size and cooling air distribution meet the design expectations. Through this temperature gradient-based differentiated orifice design, this embodiment achieves targeted and enhanced utilization of cooling resources, making the distribution of cooling air flow rate in different areas of the wall more rational, significantly improving the temperature uniformity of the outer ring components of the combustion chamber, reducing localized thermal stress and crack risk, thereby further improving the service life of the combustion chamber and the overall operational reliability.

[0055] Reference Figure 2 In this embodiment, to ensure that the wall temperature distribution at the outlet of the large bend is close to that of the preceding region, several fourth-stage air film holes 303 are provided on the inner wall 3 of the large bend near the outlet. Cooling air is injected through these air film holes and spreads along the wall surface to form an adhesive cooling film layer, thereby providing additional protection for the high heat load area of ​​the outlet section.

[0056] In one embodiment, the outer wall 2 of the large bend and the outer ring cylinder 1 are fixed together by a weld 202. The welded connection ensures the structural strength and sealing performance of both components under high-temperature gas conditions, preventing leakage of cold or hot gas at the joint, while also offering high processing and assembly efficiency. The weld 202 is typically located near the transition area between the outer ring cylinder 1 and the large bend, where stress distribution is relatively uniform, facilitating subsequent disassembly and assembly operations.

[0057] During long-term engine operation, the outer wall 2 of the large bend is prone to localized wear, oxidation corrosion, or high-temperature ablation due to direct interaction with the cooling air and combustion gas flow. When the damage reaches a certain level, replacing the entire outer ring assembly would result in high costs and excessively long repair cycles. To address this issue, the weld 202 in this embodiment is designed to be detachable. That is, when the outer wall 2 of the large bend is damaged, it can be separated from the outer ring cylinder 1 by grinding away the weld 202. Afterward, a new outer wall 2 of the large bend can be installed and re-welded, restoring the flame tube outer ring assembly to normal operation.

[0058] In terms of specific processes, high-precision welding techniques such as tungsten inert gas welding (TIG), electron beam welding, or laser welding can be used to ensure the quality of weld 202 and joint strength. During disassembly, a special grinding tool is used to grind weld 202 layer by layer until the weld fusion zone is completely removed without damaging the main structure of the outer ring cylinder 1. Before re-welding, the interface position needs to be cleaned and dimensionally checked to ensure that the new large bend outer wall 2 can be tightly bonded to the outer ring cylinder 1. In addition, to ensure the operability of maintenance, the shape and thickness of weld 202 have been designed with machining allowance, which can meet the structural strength under high temperature conditions and facilitate subsequent disassembly and re-welding. Through the above design, the outer ring assembly of the flame tube in this embodiment achieves the replaceability of the large bend outer wall 2 while maintaining structural strength and airtightness. Compared with the whole replacement solution, this method significantly reduces maintenance costs and downtime, extends the overall service life of the outer ring assembly, and improves the maintenance convenience and economy of the engine.

[0059] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An outer annulus assembly for a reverse flow combustor flame tube, characterized by, include: The outer ring cylinder (1) is used to connect with the inner ring assembly of the flame tube; The outer wall (2) of the large bend is connected to the outer ring cylinder (1). The end of the outer wall (2) of the large bend away from the outer ring cylinder (1) is used to connect with the centrifugal impeller cover. Multiple impact holes (204) are distributed on the outer wall (2) of the large bend, and the end of the outer wall (2) of the large bend is provided with a first floating connection structure (203). The inner wall (3) of the large bend is connected to the outer ring cylinder (1). The end of the inner wall (3) of the large bend away from the outer ring cylinder (1) is provided with a second floating connection structure (301). Multiple diverging holes (302) are distributed on the inner wall (3) of the large bend. A diverging cavity is formed between the outer wall (2) and the inner wall (3) of the large bend pipe. The diverging holes (302) and the impact holes (204) are staggered to form a cooling airflow channel along the impact holes (204), the diverging cavity, and the diverging holes (302). The first floating connection structure (203) and the second floating connection structure (301) are clearance-fitted to compensate for the thermal deformation difference between the outer wall (2) and the inner wall (3) of the large bend pipe. The outer ring cylinder (1) is provided with a multi-stage stepped structure along the axial direction. Each step is provided with secondary air film holes distributed in the circumferential direction. The secondary air film holes are used to introduce cooling airflow step by step. The multi-stage stepped structure includes a first-stage step, a second-stage step, and a third-stage step. The secondary air film holes include a first-stage air film hole (104) set on the first-stage step, a second-stage air film hole (105) set on the second-stage step, and a third-stage air film hole (106) set on the third-stage step. The injection angles of the first-stage air film hole (104), the second-stage air film hole (105), and the third-stage air film hole (106) increase progressively.

2. The recirculation combustion chamber flame tube outer ring assembly according to claim 1, characterized in that: The first floating connection structure (203) includes a first vertical plate and two first horizontal plates, with a first horizontal plate connected to each end of the first vertical plate to form a first opening groove; The second floating connection structure (301) includes a second vertical plate and two second horizontal plates, with a second horizontal plate connected to each end of the second vertical plate to form a second opening groove; The first and second opening slots have opposite opening directions and interlock with each other, creating a radial gap between the first and second horizontal plates. There are also axial gaps between the first and second vertical plates and between the second and first horizontal plates. The radial and axial gaps together form a labyrinthine zigzag channel.

3. The recirculation combustion chamber flame tube outer ring assembly according to claim 1, characterized in that: The axis of the impact hole (204) is perpendicular to the heated wall surface of the inner wall (3) of the large bend, so that the cooling airflow directly impacts the heated wall surface of the inner wall (3) of the large bend. The axis of the diverging hole (302) is inclined relative to the heated wall surface of the inner wall (3) of the large bend, so that the ejected cooling airflow spreads along the heated wall surface to form a gas film cooling layer.

4. The recirculation combustion chamber flame tube outer ring assembly according to claim 3, characterized in that: The projection of the impact hole (204) on the inner wall (3) of the large bend is staggered with the diverging hole (302) along the axial and circumferential directions, and the holes in adjacent rows are staggered to form a differential arrangement.

5. The recirculation combustion chamber flame tube outer ring assembly according to claim 1, characterized in that: The outer ring cylinder (1) has multiple initial gas film holes (103) in the circumferential direction of the hot air flow initiation section. The initial gas film holes (103) are used to spray cooling air flow when the combustion chamber is working, forming an initial cooling film layer on the wall surface of the outer ring cylinder (1).

6. The recirculation combustion chamber flame tube outer ring assembly according to claim 5, characterized in that: The outer ring cylinder (1) is provided with a guide plate at the outlet position of the initial film gas hole (103). The guide plate is used to guide the cooling airflow ejected from the initial film gas hole (103) to adhere and flow along the wall of the outer ring cylinder (1).

7. The recirculation combustion chamber flame tube outer ring assembly according to claim 1, characterized in that: The pore size of the secondary air film pores is positively correlated with the magnitude of the temperature gradient in the region.

8. The recirculation combustion chamber flame tube outer ring assembly according to claim 1, characterized in that: The outer wall (2) of the large bend is connected to the outer ring cylinder (1) by a weld (202), which is used to replace the outer wall (2) of the large bend separately after grinding the weld (202) when the outer wall (2) of the large bend is damaged.

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