Double-walled elbow and reverse-flow combustion chamber

Abstract

This invention discloses a double-walled small bend tube and a recirculation combustion chamber, comprising an inner wall and an outer wall spaced apart. One end of the inner wall near the flame tube is connected to the other end of the outer wall near the flame tube. The inner and outer walls form a cavity for forming a cooling gas film. The outer wall has n rows of impact cooling holes for introducing cooling gas into the cavity. Each row of impact cooling holes is evenly distributed along the circumferential direction of the outer wall and has the same diameter. The diameter of the n rows of impact cooling holes increases gradually from the end of the outer wall near the flame tube to the end away from the flame tube, so that the flow rate of cooling gas impacting the inner wall increases gradually with the distance from the flame tube. This can effectively reduce the highest wall surface temperature at the end of the inner wall, reduce the ablation and uneven deformation of the double-walled small bend tube, extend its service life, and effectively solve the air leakage problem between the small bend tube and the casing under different vibrations and thermal expansion deformation, ensuring a seal.

Description

Technical Field

[0001] This invention relates to the field of gas turbine technology, and in particular, to a double-walled small bend. Furthermore, this invention also relates to a recirculation combustion chamber comprising the aforementioned double-walled small bend. Background Technology

[0002] The recirculation combustor mainly consists of a casing, a large bend, a small bend, a flame tube, and nozzles. Among these, the small bend is a key component in the structure of modern small and medium-sized gas turbine recirculation combustors. Its main function is to rotate the flow direction of the high-temperature gas by 180°, while also assisting in regulating the gas temperature at the combustor outlet. Structurally, the small bend is generally a thin-walled part with a large curvature; in terms of its operating environment, the small bend operates in a high-temperature region within the gas turbine engine for extended periods, enduring very high thermal loads.

[0003] Currently, the small bends in the recirculation combustion chamber typically employ a single-wall or double-wall structure. For example... Figure 1 As shown, single-walled small bends are typically integrated with the inner ring of the flame tube, bearing significant thermal and mechanical stresses. Furthermore, single-walled small bends often employ traditional film cooling, which has low cooling efficiency, making them prone to ablation and deformation. Therefore, this structure cannot guarantee structural safety. In contrast, double-walled small bends, while also integrated with the inner ring of the flame tube, effectively improve strength and rigidity due to the addition of an outer wall layer. Consequently, double-walled small bends are widely used.

[0004] like Figure 2As shown, the existing double-walled small bend tube of the recirculation combustion chamber adopts a pure impact cooling method. The impact cooling holes are opened on the outer wall of the small bend tube. All impact cooling holes are evenly distributed and have the same diameter. The inner wall is not perforated. The cooling gas acts directly on the inner wall of the small bend tube through the impact cooling holes to achieve the effect of reducing the temperature. As the temperature rise requirements for small and medium-sized gas turbines increase, the thermal load on the inner wall of the double-walled small bend in the recirculation combustion chamber also increases accordingly. This leads to an increase in the hot side wall temperature of the small bend's inner wall. On the one hand, along the flow direction of the high-temperature gas, the gas temperature gradually increases from top to bottom along the arc-shaped surface of the small bend (the end of the small bend closer to the flame tube is defined as the upper section, and the end of the small bend closer to the inner casing is defined as the lower section). The cooling gas film formed by the uniformly distributed impact holes is insufficient to cool the lower wall temperature of the small bend's inner wall. This results in insufficient cooling gas flow through the impact cooling holes at the lower end of the small bend due to the excessively high gas temperature, leading to a higher temperature on the lower section of the inner wall (hot side) of the small bend compared to the upper section. On the other hand, if the impact distance between the inner and outer walls of the double-walled small bend is too large or too small, the gas film formed after the cooling gas passes through the impact cooling holes will not completely cover the outer surface of the entire inner wall of the small bend, resulting in an excessively high temperature on the inner surface (hot side) of the double-walled inner wall. For the reasons mentioned above, under the long-term scouring of hot gas, the wall temperature distribution of the inner wall of the small bend exhibits a "cold at the top and hot at the bottom" distribution trend along the flow direction of the high-temperature gas. Local high-temperature hot spots and excessively high wall temperatures are prone to occur in the lower section, especially at the end, which can easily cause the small bend to burn out. At the same time, the temperature difference between the inner and outer walls of the small bend is too large. After long-term use and deformation, it is also easy to cause uneven thermal deformation of the small bend, resulting in air leakage between the small bend and the casing, which affects the service life of the small bend. Summary of the Invention

[0005] This invention provides a double-walled small bend and a recirculation combustion chamber to solve the technical problems of excessively high temperature at the end of the inner wall of the double-walled small bend in the existing gas turbine combustion chamber, which easily causes the small bend to burn; and the small bend deforming after long-term use, which easily causes uneven thermal deformation of the small bend, resulting in air leakage between the small bend and the casing.

[0006] According to one aspect of the present invention, a double-walled small curved tube is provided, comprising an inner wall and an outer wall arranged at intervals. One end of the inner wall near the flame tube is connected to one end of the outer wall near the flame tube. The inner wall and the outer wall form a cavity for forming a cooling gas film. The outer wall is provided with n rows of impact cooling holes for introducing cooling gas into the cavity. Each row of impact cooling holes is uniformly arranged along the circumferential direction of the outer wall and has the same hole diameter. The hole diameter of the n rows of impact cooling holes increases gradually from the end of the outer wall near the flame tube to the end away from the flame tube, so that the flow rate of the cooling gas impacting the inner wall increases gradually with the distance from the flame tube.

[0007] Furthermore, the impact distance between the inner wall and the outer wall is 2 to 2.5 mm.

[0008] Furthermore, the centerline of the impact cooling holes is arranged perpendicular to the inner wall surface of the outer wall.

[0009] Furthermore, the center points of two adjacent rows of impact cooling holes are spaced the same in the radial direction along the arc-shaped surface of the outer wall.

[0010] Furthermore, the impact cooling holes are round holes or flared holes, with the diameter of the flared hole on the inner side of the outer wall being larger than the diameter on the outer side of the outer wall.

[0011] Furthermore, the diameter Φ of the impact cooling holes is 0.5–1 mm, and n rows of impact cooling holes are arranged sequentially along the flow direction of the high-temperature combustion gas. The diameter of adjacent rows of impact cooling holes satisfies the condition Φ. n =Φ n-1 +d, where Φ n Φ is the diameter of the nth row of impact cooling holes. n-1 d is the diameter of the (n-1)th row of impact cooling holes, and d is the increase in hole diameter, ranging from 0.05 to 0.1 mm.

[0012] Furthermore, a sealing ring mounting groove is provided on the end of the outer wall away from the flame tube, and a sealing ring for sealing the gap between the outer wall and the inner casing is embedded in the sealing ring mounting groove.

[0013] Furthermore, the sealing ring is equipped with an adjustable gap joint structure.

[0014] The joint structure includes a first fitting protrusion and a first fitting recess disposed on one end of the sealing ring. The joint structure also includes a second fitting recess disposed on the other end of the sealing ring for fitting with the first fitting protrusion and a second fitting protrusion for fitting with the first fitting recess, so as to ensure that the sealing ring can seal the gap between the outer wall and the inner casing under different vibration conditions.

[0015] Furthermore, the cross-sectional shape of the first fitting protrusion includes a first inclined sealing section, a first straight-edge sealing section for abutting the sealing ring mounting groove, and a second straight-edge sealing section for abutting the inner casing. The cross-sectional shape of the second fitting recess matches the cross-sectional shape of the first fitting protrusion. The cross-sectional shape of the second fitting protrusion includes a second inclined sealing section that matches the first inclined sealing section, a third straight-edge sealing section for abutting the sealing ring mounting groove, and a fourth straight-edge sealing section for abutting the inner casing. The cross-sectional shape of the first fitting recess matches the cross-sectional shape of the second fitting protrusion.

[0016] According to another aspect of the invention, a reflux combustion chamber is also provided, which includes the aforementioned double-walled small bend.

[0017] The present invention has the following beneficial effects:

[0018] In use, the double-walled small bend of this invention allows cooling gas to enter the cavity through impact cooling holes on the outer wall. Due to the high velocity of the cooling gas jet, it directly impacts the outer surface of the inner wall, achieving heat exchange and cooling the inner wall. The impact cooling holes in the same row are evenly distributed along the circumferential direction of the outer wall, and the holes in the same row have the same diameter, ensuring that the cooling effect on the circumferential direction of the inner wall is uniform, resulting in a uniform temperature along the inner wall's circumference. The diameter of the nth row of impact cooling holes gradually increases from the end of the outer wall closer to the flame tube to the end farther away from the flame tube. This ensures that the cooling gas flow rate entering the nth row of impact cooling holes is greater than that entering the (n-1)th row. The cooling gas flow rate corresponds to the "colder at the top, hotter at the bottom" distribution trend of the inner wall temperature, effectively reducing the temperature at the lower end of the inner wall. This reduces erosion and allows the double-walled small bend to withstand [the heat generated by the impact cooling holes]. The higher temperature of the combustion gas ensures a more uniform temperature on the inner wall, preventing localized high temperatures that could lead to inconsistent deformation and cracking, thus extending service life. Efficient cooling at the lower end of the inner wall lowers the overall temperature and reduces the temperature difference between the inner and outer walls, resolving the issue of uneven thermal deformation of the double-walled small bend, which could cause leakage between the small bend and the casing. Without increasing the total cooling gas flow, the impact cooling holes in the double-walled small bend employ a "progressive expansion" distribution method along the flow direction of the high-temperature combustion gas. By reducing the impact cooling gas volume in the upper and middle sections of the inner wall, the volume in the final section increases, achieving a more rational distribution of the impact cooling gas flow. This design is simple, easy to manufacture, and effectively reduces the highest wall surface temperature at the final section of the inner wall, minimizing ablation and uneven deformation of the double-walled small bend, ensuring a good seal and extending service life.

[0019] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0021] Figure 1 This is a schematic diagram of the structure of a single-walled small bend in the prior art;

[0022] Figure 2 This is a schematic diagram of the structure of a double-walled small bend in the prior art;

[0023] Figure 3 This is a schematic diagram of the structure of the double-walled small bend pipe according to a preferred embodiment of the present invention;

[0024] Figure 4 This is a radial cross-sectional view of the arcuate surface of the outer wall of a preferred embodiment of the present invention;

[0025] Figure 5 yes Figure 4 The diagram shown is in direction P.

[0026] Figure 6 This is a schematic diagram of the sealing ring structure according to a preferred embodiment of the present invention;

[0027] Figure 7 This is a schematic diagram of the joint structure of a preferred embodiment of the present invention;

[0028] Figure 8 This is a schematic diagram of the cross-sectional shape of the first fitting protrusion in a preferred embodiment of the present invention;

[0029] Figure 9 This is a schematic diagram of the cross-sectional shape of the second fitting protrusion in a preferred embodiment of the present invention.

[0030] Legend:

[0031] 10. Inner wall; 20. Outer wall; 201. Impact cooling hole; 202. Sealing ring mounting groove; 30. Cavity; 40. Sealing ring; 401. Joint structure; 4011. First fitting protrusion; 40111. First inclined sealing section; 40112. First straight edge sealing section; 40113. Second straight edge sealing section; 4012. First fitting recess; 4013. Second fitting recess; 4014. Second fitting protrusion; 40141. Second inclined sealing section; 40142. Third straight edge sealing section; 40143. Fourth straight edge sealing section; 4015. Rounded corner section. Detailed Implementation

[0032] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0033] like Figure 3 , Figure 4 and Figure 5As shown, the double-walled small curved tube of this embodiment includes an inner wall 10 and an outer wall 20 arranged at intervals. Both the inner wall 10 and the outer wall 20 are annular walls. The end of the inner wall 10 near the flame tube is connected to the end of the outer wall 20 near the flame tube. The inner wall 10 and the outer wall 20 form a cavity 30 for forming a cooling gas film. The outer wall 20 has n rows of impact cooling holes 201 for introducing cooling gas into the cavity 30. Each row of impact cooling holes 201 is evenly arranged along the circumferential direction of the outer wall 20 and has the same hole diameter. The hole diameter of the n rows of impact cooling holes 201 increases from the end of the outer wall 20 near the flame tube to the end away from the flame tube, so that the flow rate of the cooling gas impacting the inner wall 10 increases row by row as it moves away from the flame tube.

[0034] When the double-walled small elbow pipe of this embodiment is in use, the cooling gas enters the cavity 30 through the impingement cooling holes 201 on the outer wall 20. Due to the relatively high jet velocity of the cooling gas, the cooling gas will directly impinge on the outer side of the inner wall 10, and the impingement heat transfer can achieve the effect of cooling the inner wall 10 and reducing the temperature; the impingement cooling holes 201 in the same row are evenly arranged along the circumferential direction of the outer wall 20, and the apertures of the impingement cooling holes 201 in the same row are the same, which can ensure that the cooling effect of the impingement cooling holes 201 in the same row on the circumferential direction of the inner wall 10 is the same, making the temperature of the inner wall 10 circumferentially uniform; the apertures of the n rows of impingement cooling holes 201 gradually increase from the end of the outer wall 20 close to the combustion chamber to the end far from the combustion chamber, so that the flow rate of the cooling gas entering the nth row of impingement cooling holes 201 is more than the flow rate of the cooling gas entering the (n - 1)th row of impingement cooling holes 201. The flow rate of the cooling gas corresponds to the "upper cold and lower hot" distribution trend of the wall temperature distribution of the inner wall 10, which can efficiently reduce the temperature at the lower end of the inner wall 10. On the one hand, it can reduce ablation, enabling the double-walled small elbow pipe to withstand higher-temperature gas. On the other hand, it makes the temperature of the profile of the inner wall 10 uniform, avoiding local high temperatures on the profile of the inner wall 10, resulting in inconsistent deformation and cracking, thereby extending the service life; due to the efficient cooling of the lower end of the inner wall 10, the overall temperature of the inner wall 10 is reduced, and the temperature difference between the inner wall 10 and the outer wall 20 can also be reduced, thus solving the problem of uneven thermal deformation of the double-walled small elbow pipe, resulting in air leakage between the small elbow pipe and the casing; without increasing the total flow rate of the cooling gas, the impingement cooling holes of the double-walled small elbow pipe adopt a "progressive expansion type" distribution method along the flow direction of the high-temperature gas. By reducing the impingement cooling gas volume in the upper and middle sections of the inner wall of the small elbow pipe, the impingement cooling gas volume in the end section of the inner wall of the small elbow pipe is increased, realizing a more reasonable distribution of the flow rate of the impingement cooling gas. The structure is simple, the processing difficulty is low, it can effectively reduce the highest wall temperature at the end section of the inner wall 10, reduce ablation and uneven deformation of the double-walled small elbow pipe, ensure the sealing effect, and extend the service life. Optionally, the number of rows n of the impingement cooling holes 201 is 5 to 7 rows, the number of impingement cooling holes 201 in each row is the same, and the quantity is 130 to 160, that is, the impingement cooling holes 201 are in j columns, 130 < j < 160, and the impingement cooling holes 201 in adjacent two rows are staggered, and the impingement cooling holes 201 in the C j column of the impingement cooling holes 201 are arranged between the C j-1 column and the C j+1 column to ensure that the cooling gas introduced by the impingement cooling holes 201 can completely cover the inner side of the inner wall 10, making the overall temperature of the inner wall 10 uniform, avoiding local high temperatures and deformation, thereby ensuring the airtightness of the small elbow pipe and extending the service life.

[0035] As Figure 3As shown, in this embodiment, the impact distance between the inner wall 10 and the outer wall 20 is 2 to 2.5 mm; this ensures that after the cooling gas passes through the impact cooling hole 201, the formed gas film can completely cover the entire outer surface of the inner wall 10, preventing local high temperature and deformation of the inner wall 10, thereby ensuring the airtightness of the small bend and extending its service life.

[0036] like Figure 3 As shown, in this embodiment, the axis of the impact cooling hole 201 is arranged perpendicular to the inner wall surface of the outer wall 20 to make full use of the impulse of the cooling airflow and ensure the cooling effect.

[0037] like Figure 4 and Figure 5 As shown in this embodiment, on a circumference of the same size, with a fixed number of impact cooling holes 201, the larger the diameter of the impact cooling holes 201, the denser the impact cooling holes 201 are considered to be. The center points of two adjacent rows of impact cooling holes 201 are spaced in the radial direction along the arc-shaped surface of the outer wall 20, i.e., L1=L2=L3=…Ln. The diameter of the nth row of impact cooling holes 201 is larger than that of the (n+1)th row of impact cooling holes 201, making the impact cooling holes 201 on the outer wall 20 a non-uniform layout of "sparse at the top and dense at the bottom". The cooling air volume impacting the inner wall 10 increases as it goes down, which more rationally distributes the impact cooling air volume and reduces the impact cooling air volume in the upper and middle sections of the inner wall. This corresponds to the "cold at the top and hot at the bottom" distribution trend of the wall temperature distribution of the inner wall 10, which can effectively reduce the highest wall surface temperature at the end of the inner wall 10, thereby reducing ablation and uneven deformation, ensuring airtightness, and extending service life.

[0038] like Figure 4 As shown, in this embodiment, the impact cooling hole 201 is a round hole, which has a simple structure and is easy to process. Optionally, the impact cooling hole 201 is a trumpet hole, and the diameter of the trumpet hole on the inner side of the outer wall 20 is larger than the diameter on the outer side of the outer wall 20, so that the cooling gas introduced into a single impact cooling hole 201 can cover a larger area on the inner side of the inner wall 10, thereby improving the cooling efficiency.

[0039] like Figure 5 As shown, in this embodiment, the aperture Φ of the impact cooling hole 201 is 0.5-1mm. A aperture smaller than 0.5mm is difficult to process, while an aperture larger than 1mm may reduce the strength of the outer wall 20. When the impact spacing is 2-2.5mm, the cooling gas coverage is optimal after passing through the impact cooling hole 201 with an aperture Φ of 0.5-1mm. n rows of impact cooling holes 201 are arranged sequentially along the flow direction of the high-temperature gas, and the aperture of two adjacent rows of impact cooling holes 201 satisfies the Φ... n =Φ n-1 +d, where Φ n Φ is the diameter of the nth row of impact cooling holes 201.n-1 Let d be the diameter of the (n-1)th row of impact cooling holes 201, and d be the increase in hole diameter, ranging from 0.05 to 0.1 mm; so that the cooling gas flow rate Q introduced into the nth row of impact cooling holes 201 is... n The flow rate Q of the cooling gas introduced into the (n-1)th row of impact cooling holes 201 n-1 The temperature distribution of the inner wall 10 is 1.05 to 1.1 times that of the outer wall, exhibiting a "cold at the top and hot at the bottom" distribution trend. This allows for a more rational allocation of the flow rate of the impact cooling gas, improving the cooling effect and reducing the temperature at the lower end of the inner wall 10. This reduces erosion at the end of the inner wall 10 (the end furthest from the flame tube), preventing uneven deformation and cracking due to localized high temperatures. This ensures the airtightness of the double-walled small bend and extends its service life. If Q n Less than 1.05 times Q n-1 The temperature drop at the lower end of the inner wall 10 is not significant, making it difficult to avoid end ablation of the inner wall 10; if Q n Greater than 1.1 times Q n-1 If the cooling airflow at the upper end of the inner wall 10 is too low, the cooling effect at the upper end of the inner wall 10 will be poor, and the wall temperature distribution of the inner wall 10 will show a "hot at the top and cold at the bottom" distribution trend, which may lead to uneven deformation and cracking due to local high temperature.

[0040] like Figure 3 and Figure 4 As shown, in this embodiment, a sealing ring mounting groove 202 is provided at the end of the outer wall 20. A sealing ring 40 for sealing the gap between the outer wall 20 and the inner casing is embedded in the sealing ring mounting groove 202. The sealing ring 40 is detachably connected to the sealing ring mounting groove 202 for easy replacement. The sealing ring 40 is mainly made of a high-temperature alloy with good elasticity, so that the inner casing always abuts against the sealing ring 40 to ensure the sealing effect. Optionally, the diameter of the sealing ring 40 is 150mm to 250mm. Optionally, a reinforcing structure 203 for opening the sealing ring mounting groove 202 is provided at the end of the outer wall 20 to enhance the support strength of the end of the outer wall 20, prevent deformation of the end of the outer wall 20, and ensure that the sealing ring 40 always fits against the inner casing to ensure the sealing effect.

[0041] like Figure 6 and Figure 7As shown, in this embodiment, the sealing ring 40 is provided with an adjustable gap seam structure 401. The seam structure 401 includes a first fitting protrusion 4011 and a first fitting recess 4012 provided on one end of the sealing ring 40. The seam structure 401 also includes a second fitting recess 4013 and a second fitting protrusion 4014 provided on the other end of the sealing ring 40 for fitting with the first fitting protrusion 4011 and for fitting with the first fitting recess 4012, so as to ensure that the sealing ring 40 can withstand different vibration conditions. The sealing ring 40 can seal the gap between the outer wall 20 and the inner casing. In its natural state, the first fitting protrusion 4011 and the second fitting protrusion 4014 partially overlap, and the joint structure 401 can both expand and compress. Under different vibration levels, the inner casing and the outer wall 20 may separate slightly due to different vibration frequencies, or separate due to thermal expansion deformation caused by long-term use. The adjustable gap joint structure 401 can fill the gap between the inner casing and the outer wall 20 due to its own elasticity. During installation, the joint structure 401 is opened, allowing the first fitting protrusion 4011 and the second fitting protrusion 4014 to disengage. The sealing ring 40 is then inserted into the sealing ring mounting groove 202 at the end of the outer wall 20. The sealing ring mounting groove 202 tightens the sealing ring 40, causing the first fitting protrusion 4011 and the second fitting protrusion 4014 to overlap again. The inner casing is then overlapped at the end of the outer wall 20. The inner casing presses the sealing ring 40, causing the joint structure 401 to be in a compressed state. At this time, the sealing ring 40 abuts against the inner casing due to its own elasticity, thereby sealing the gap between the outer wall 20 and the inner casing. When the inner casing and the outer wall 20 are separated, the sealing ring 40 returns to its elastic state, causing the joint structure 401 to expand further, filling the gap between the inner casing and the outer wall 20. This ensures that no air leakage occurs between the outer wall 20 and the inner casing, regardless of the different operating conditions of the gas turbine or the thermal expansion and deformation that may occur during long-term use, thus guaranteeing airtightness. Optionally, the first fitting protrusion 4011 and the second fitting protrusion 4014 have the same length in the circumferential direction, and the first fitting recess 4012 and the second fitting recess 4013 have the same length in the circumferential direction. Optionally, the joint distance between the first fitting recess 4012 and the second fitting protrusion 4014 is 0.5 to 3 mm. If the joint distance is too small, the sealing ring 40 will have difficulty filling the gap between the inner casing and the outer wall 20; if the joint distance is too large, the sealing ring 40 will easily loosen from the sealing ring mounting groove 202.

[0042] like Figure 6 , Figure 7 , Figure 8 and Figure 9As shown, in this embodiment, the cross-sectional shape of the first fitting protrusion 4011 includes a first inclined sealing section 40111 for sealing the gap between the first fitting protrusion 40111 and the second fitting protrusion 4014, a first straight-edge sealing section 40112 for abutting the sealing ring mounting groove 202, and a second straight-edge sealing section 40113 for abutting the inner casing. The cross-sectional shape of the second fitting recess 4013 matches the cross-sectional shape of the first fitting protrusion 4011. The cross-sectional shape of the second fitting protrusion 4014 includes a second inclined sealing section 40141 that matches the first inclined sealing section 40111, a third straight-edge sealing section 40142 for abutting the sealing ring mounting groove 202, and a fourth straight-edge sealing section 40143 for abutting the inner casing. The cross-sectional shape of the first fitting recess 4012 matches the cross-sectional shape of the second fitting protrusion 40111. The cross-sectional shape of 4 is matched; during installation, the joint structure 401 is opened so that the first inclined sealing section 40111 and the second inclined sealing section 40141 are no longer in contact. The opened sealing ring 40 is inserted into the sealing ring mounting groove 202. After the sealing ring 40 is tightened, the first inclined sealing section 40111 and the second inclined sealing section 40141 are in contact. The first straight edge sealing section 40112 and the third straight edge sealing section 40142 are both in contact with the sealing ring mounting groove 202. Then the inner casing is overlapped on the outer wall 20. At this time, the sealing ring 40 expands outward due to its own elasticity. The second straight edge sealing section 40113 and the fourth straight edge sealing section 40143 are both in contact with the inner casing. The joint structure 401 of this structure is ingenious. When the joint distance changes, the sealing ring 40 can still achieve the sealing of the gap between the inner casing and the outer wall 20. Optionally, the cross-sectional shape of the sealing ring 40 is quadrilateral. The cross-sectional shape of the first fitting protrusion 4011 includes a first inclined sealing section 40111, a first straight-edge sealing section 40112, and a second straight-edge sealing section 40113. The cross-sectional shape of the second fitting protrusion 4014 includes a second inclined sealing section 40141, three third straight-edge sealing sections 40142, and a fourth straight-edge sealing section 40143. The cross-sectional shapes of the first fitting protrusion 4011 and the second fitting protrusion 4014 are spliced ​​together to form the cross-sectional shape of the sealing ring 40. It can be understood that the cross-sectional shape of the sealing ring 40 can also be triangular, pentagonal, or other polygonal, and the shape of the sealing ring mounting groove 202 can be adjusted accordingly. Optionally, the inclination angle α of the first inclined sealing section 40111 is 20° to 70°, and the inclination angle of the second inclined sealing section 40141 is the same as that of the first inclined sealing section 40111, so that the first fitting protrusion 4011 and the second fitting protrusion 4014 are completely fitted together to ensure the sealing effect.Optionally, the first straight edge sealing section 40112 and the second straight edge sealing section 40113, the third straight edge sealing section 40142 and the fourth straight edge sealing section 40143, and two adjacent third straight edge sealing sections 40142 are all connected by rounded corner sections 4015. The rounded corner sections 4015 can prevent the sealing ring 40 from scratching the operators and parts.

[0043] A recirculation combustion chamber includes the aforementioned double-walled small bend tube. The impact cooling holes 201 on the outer wall 20 of the double-walled small bend tube are arranged in a "gradually expanding" manner along the flow direction of the high-temperature combustion gas. The cooling gas flow rate entering the nth row of impact cooling holes 201 is greater than that entering the (n-1)th row of impact cooling holes 201. The cooling gas flow rate corresponds to the "cold at the top and hot at the bottom" distribution trend of the wall temperature distribution of the inner wall 10. On the one hand, it can efficiently reduce the temperature of the lower end of the inner wall 10, reduce ablation, and enable the recirculation combustion chamber to withstand higher-temperature combustion gas. On the other hand, it can make the overall temperature of the inner wall 10 uniform, avoid uneven deformation caused by local high temperature in the double-walled small bend tube, ensure the airtightness of the recirculation combustion chamber, and extend its service life. At the same time, an adjustable joint gap sealing ring 40 is used to prevent the sealing failure at the connection between the inner casing and the small bend tube after long-term deformation due to long-term use of the small bend tube or casing, further ensuring the sealing effect.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A double-walled small bend pipe, characterized in that, Including the spaced-out inner wall (10) and outer wall (20), The inner wall (10) near the flame tube is connected to the outer wall (20) near the flame tube, and the inner wall (10) and the outer wall (20) form a cavity (30) for forming a cooling gas film. The outer wall (20) is provided with n rows of impact cooling holes (201) for introducing cooling gas into the cavity (30). Each row of impact cooling holes (201) is evenly distributed along the circumferential direction of the outer wall (20), and the hole diameter is consistent. The diameter of the n rows of impact cooling holes (201) increases gradually from the end of the outer wall (20) closer to the flame tube to the end farther away from the flame tube, so that the flow rate of cooling gas impacting the inner wall (10) increases gradually as it moves away from the flame tube.

2. The double-walled small bend pipe according to claim 1, characterized in that, The impact distance between the inner wall (10) and the outer wall (20) is 2 to 2.5 mm.

3. The double-walled small bend pipe according to claim 1, characterized in that, The centerline of the impact cooling hole (201) is arranged perpendicular to the inner wall surface of the outer wall (20).

4. The double-walled small bend according to claim 1, characterized in that, The center points of two adjacent rows of impact cooling holes (201) are spaced at the same distance along the radial direction of the arc-shaped surface of the outer wall (20).

5. The double-walled small bend pipe according to claim 1, characterized in that, The impact cooling hole (201) is a round hole, or The impact cooling hole (201) is a horn hole, and the diameter of the horn hole on the inner side of the outer wall (20) is larger than the diameter on the outer side of the outer wall (20).

6. The double-walled small bend pipe according to any one of claims 1 to 5, characterized in that, The diameter Φ of the impact cooling holes (201) is 0.5~1mm, and n rows of impact cooling holes (201) are arranged sequentially along the flow direction of the high-temperature gas. The diameters of two adjacent rows of impact cooling holes (201) satisfy Φ n =Φ n-1 +d, Where Φ n Φ is the diameter of the nth row of impact cooling holes (201). n-1 d is the diameter of the (n-1)th row of impact cooling holes (201), and d is the increase in diameter, ranging from 0.05 to 0.1 mm.

7. The double-walled small bend according to claim 6, characterized in that, A sealing ring mounting groove (202) is provided on the end of the outer wall (20) away from the flame tube, and a sealing ring (40) for sealing the gap between the outer wall (20) and the inner casing is embedded in the sealing ring mounting groove (202).

8. The double-walled small bend according to claim 7, characterized in that, The sealing ring (40) is provided with an adjustable gap joint structure (401). The joint structure (401) includes a first fitting protrusion (4011) and a first fitting recess (4012) disposed on one end of the sealing ring (40). The joint structure (401) also includes a second fitting recess (4013) disposed on the other end of the sealing ring (40) for fitting with the first fitting protrusion (4011) and a second fitting protrusion (4014) for fitting with the first fitting recess (4012), so as to ensure that the sealing ring (40) can seal the gap between the outer wall (20) and the inner casing under different vibration conditions.

9. The double-walled small bend according to claim 8, characterized in that, The cross-sectional shape of the first fitting protrusion (4011) includes a first inclined sealing section (40111), a first straight-edge sealing section (40112) for abutting against the sealing ring mounting groove (202), and a second straight-edge sealing section (40113) for abutting against the inner casing. The cross-sectional shape of the second fitting recess (4013) matches the cross-sectional shape of the first fitting protrusion (4011). The cross-sectional shape of the second fitting protrusion (4014) includes a second inclined sealing section (40141) that matches the first inclined sealing section (40111), a third straight-edge sealing section (40142) for abutting the sealing ring mounting groove (202), and a fourth straight-edge sealing section (40143) for abutting the inner casing. The cross-sectional shape of the first fitting recess (4012) matches the cross-sectional shape of the second fitting protrusion (4014).

10. A recirculation combustion chamber, characterized in that, Includes the double-walled small bend according to any one of claims 1 to 9.

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