Butt joint structure and butt joint method for thrust chamber spray pipes of rocket engine

Abstract

The invention discloses a rocket engine thrust chamber spray pipe butt joint structure and a butt joint method, the rocket engine thrust chamber spray pipe butt joint structure comprises a spray pipe contraction and expansion section, a spray pipe expansion section and a spray pipe extension section, the spray pipe contraction and expansion section, the spray pipe expansion section and the spray pipe extension section each comprise an inner wall and an outer wall, and a first coaxial butt joint structure is arranged between the outer wall of the contraction and expansion section and the outer wall of the expansion section; and a second coaxial butt joint structure is arranged between the outer wall of the expansion section and the outer wall of the extension section. The first coaxial butt joint structure comprises a coaxial butt joint groove formed between the outer wall of the contraction and expansion section and the outer wall of the expansion section, a coaxial connecting ring is welded in the coaxial butt joint groove, and the coaxial connecting ring enables the end face of the contraction and expansion section of the spray pipe not to make contact with the end face of the expansion section of the spray pipe. According to the thrust chamber spray pipe butt joint structure, through welding of four different positions, the fusion welding thickness and the heat input amount are reduced, deformation of the inner wall and the outer wall is avoided, the welding quality and the coaxiality of spray pipe assemblies are guaranteed, and then the connection reliability of all the assemblies of the spray pipe is guaranteed under the conditions of high temperature, high pressure, large vibration and overload.

Description

Technical Field

[0001] The present invention belongs to the technical field of rocket engines, relates to a thrust chamber nozzle, and particularly relates to a docking structure and a docking method for a thrust chamber nozzle of a rocket engine. Background Art

[0002] The thrust chamber of a liquid rocket engine mainly consists of a head and a body. The body includes a combustion chamber and a nozzle. The nozzle includes a converging-diverging section, a diverging section, and an extension section. The thrust chamber adopts regenerative cooling. Each section component of the nozzle is brazed and connected by an inner wall and an outer wall, and a regenerative cooling channel is formed between the inner and outer walls. If a single docking joint (such as flat docking, lock-bottom docking, and corner docking, etc.) is used, the processability is poor, the fusion welding thickness is high, the heat input is large, it is easy to cause deformation of the inner and outer walls, reduce the coaxiality of the components and the strength of the welded joint, and cannot guarantee the brazing quality of the inner and outer walls, which may lead to crack damage and cause leakage of the regenerative cooling liquid.

[0003] The nozzle works under high temperature, high pressure, large vibration, and overload conditions, and the sealing performance at the nozzle docking position is prone to problems. Therefore, a docking structure is needed to achieve high-quality welding between components, ensure high-quality brazing and welding, including the coaxiality of the envelope brazing-welding structure, and the reliability of these docking parts. Summary of the Invention

[0004] Aiming at the deficiencies existing in the prior art, the purpose of the present invention is to provide a docking structure and a docking method for a thrust chamber nozzle of a rocket engine to solve the technical problem that it is difficult to balance the welding quality of the nozzle components and the coaxiality of the nozzle components in the prior art.

[0005] To solve the above technical problems, the present invention is implemented by adopting the following technical solutions:

[0006] A docking structure for a thrust chamber nozzle of a rocket engine includes a nozzle converging-diverging section, a nozzle diverging section, and a nozzle extension section connected in sequence. The nozzle converging-diverging section includes a converging-diverging section inner wall and a converging-diverging section outer wall coaxially arranged outside the converging-diverging section inner wall. The nozzle diverging section includes a diverging section inner wall and a diverging section outer wall coaxially arranged outside the diverging section inner wall. The nozzle extension section includes an extension section inner wall and an extension section outer wall coaxially arranged outside the extension section inner wall. A first coaxial docking structure is arranged between the converging-diverging section outer wall and the diverging section outer wall.

[0007] The first coaxial docking structure includes a coaxial docking groove opened between the converging-diverging section outer wall and the diverging section outer wall. A coaxial connecting ring is welded in the coaxial docking groove, and the coaxial connecting ring makes the end faces of the nozzle converging-diverging section and the nozzle diverging section not in contact.

[0008] The present invention also has the following technical features:

[0009] The coaxial connection ring described above includes multiple coaxial connection arc segments. The multiple coaxial connection arc segments are sequentially connected end to end in the circumferential direction to form a coaxial connection ring, and adjacent two coaxial connection arc segments are connected by a second weld seam.

[0010] The coaxial connection arc segment described above includes an integrally formed first outer arc segment and a first inner arc segment. The first outer arc segment is located radially outside the first inner arc segment, and the axial width of the first outer arc segment is greater than the axial width of the first inner arc segment, such that the cross-section of the coaxial connection ring is in a T shape.

[0011] One side wall of the coaxial butt joint groove is a first stepped section and a second stepped section provided on the inner end surface of the outer wall of the converging-diverging section; the other side wall of the coaxial butt joint groove is a third stepped section and a fourth stepped section provided on the inner end surface of the outer wall of the expanding section.

[0012] The inner side walls of the first outer arc segment of the coaxial connection ring are respectively in contact with the side walls of the first stepped section and the third stepped section; the first outer arc segment of the coaxial connection ring is connected to the first stepped section by a third weld seam, and the first outer arc segment of the coaxial connection ring is connected to the third stepped section by a fourth weld seam.

[0013] The two axial surfaces of the first inner arc segment of the coaxial connection ring are respectively in partial contact with the stepped surfaces of the second stepped section and the fourth stepped section, and there is a first gap between the inner side walls of the first inner arc segment of the coaxial connection ring and the side walls of the second stepped section and the fourth stepped section.

[0014] The coaxial connection arc segment described above includes an integrally formed second outer arc segment, a second middle arc segment, and a second inner arc segment. The second outer arc segment is located radially outside the second middle arc segment, the second middle arc segment is located radially outside the second inner arc segment, the axial width of the second outer arc segment is greater than the axial width of the second middle arc segment, the axial width of the second middle arc segment is greater than the axial width of the second inner arc segment, and one axial surface of the second inner arc segment is flush with one axial surface of the second middle arc segment.

[0015] One side wall of the coaxial butt joint groove is a fifth stepped section and a sixth stepped section provided on the inner end surface of the outer wall of the converging-diverging section; the other side wall of the coaxial butt joint groove is a seventh stepped section and an axially straight section provided on the inner end surface of the outer wall of the expanding section.

[0016] The inner side wall of the second outer arc segment of the coaxial connection ring is in contact with the side walls of the fifth stepped section and the seventh stepped section; the second outer arc segment of the coaxial connection ring is connected to the fifth stepped section by a third weld seam, and the second outer arc segment of the coaxial connection ring is connected to the seventh stepped section by a fourth weld seam.

[0017] One axial surface of the second middle-layer arc segment of the coaxial connection ring is in partial contact with the step surface of the sixth stepped segment. A second gap is left between the inner side wall of the second middle-layer arc segment of the coaxial connection ring and the side wall of the sixth stepped segment. A third gap is left between one axial surface of the second inner-layer arc segment of the coaxial connection ring and the side wall of the sixth stepped segment. The other axial surfaces of the second middle-layer arc segment and the second inner-layer arc segment of the coaxial connection ring are in complete contact with the end face of the axial straight segment. The inner side wall of the second inner-layer arc segment of the coaxial connection ring is not flush with the inner surfaces of the outer walls of the converging-diverging section and the diverging section.

[0018] The inner wall of the converging-diverging section is connected to the inner wall of the diverging section by a first weld seam. The first weld seam is located directly below the coaxial connection ring.

[0019] The first weld seam is welded by a flat butt joint. The second weld seam is welded by arc welding. The third weld seam is welded by a lock-bottom butt joint. The fourth weld seam is welded by a lock-bottom butt joint.

[0020] A second coaxial docking structure is provided between the outer wall of the diverging section and the outer wall of the extension section. The structure of the second coaxial docking structure is the same as that of the first coaxial docking structure.

[0021] A communicating cooling channel is formed between the inner walls of the converging-diverging section, the diverging section, and the extension section and the outer walls of the converging-diverging section, the diverging section, and the extension section.

[0022] The inner wall and the outer wall of the converging-diverging section are connected by ribs. The inner wall and the outer wall of the diverging section are connected by ribs. The inner wall and the outer wall of the extension section are connected by ribs.

[0023] The present invention also protects a docking method for a docking structure of a rocket engine thrust chamber nozzle. The docking method of the nozzle docking structure uses the above-mentioned rocket engine thrust chamber nozzle docking structure. The method specifically includes the following steps:

[0024] Step 1, brazing the inner wall and the outer wall of the converging-diverging section, the inner wall and the outer wall of the diverging section, and the inner wall and the outer wall of the extension section together by ribs respectively;

[0025] Step 2, welding the inner wall of the converging-diverging section and the inner wall of the nozzle diverging section to form a first weld seam;

[0026] Step 3, clamping multiple coaxial connection rings between the outer wall of the converging-diverging section and the outer wall of the diverging section;

[0027] Step 4: Weld the multiple coaxially connected rings clamped between the outer wall of the converging-diverging section and the outer wall of the diverging section in Step 3 to form the second weld seam.

[0028] Step 5: Weld the outer wall of the converging-diverging section to the first outer arc section of the coaxially connected ring in Step 3 to form the third weld seam.

[0029] Step 6: Weld the outer wall of the diverging section to the first outer arc section of the coaxially connected ring in Step 3 to form the fourth weld seam.

[0030] Step 7: Weld the nozzle diverging section and the nozzle extension section successively using the welding method between the nozzle converging-diverging section and the nozzle diverging section, so that the nozzle converging-diverging section, the nozzle diverging section and the nozzle extension are connected together.

[0031] Compared with the prior art, the present invention has the following technical effects:

[0032] (Ⅰ) For the thrust chamber nozzle docking structure proposed by the present invention, a single docking surface is connected by welding joints at four different positions, reducing the fusion welding thickness and heat input, capable of avoiding deformation of the inner wall and the outer wall, ensuring the welding quality and the coaxiality of the nozzle assembly, and further ensuring the connection reliability of each component of the nozzle under high temperature, high pressure, large vibration and overload conditions.

[0033] (Ⅱ) For the thrust chamber nozzle docking structure proposed by the present invention, a coaxially connected ring is used to dock the nozzle components. The structure is simple and easy to process. The gap with the outer wall can reduce the welding stress, avoid welding cracks or other defects, and improve the welding structure strength.

[0034] (Ⅲ) For the thrust chamber nozzle docking structure proposed by the present invention, it can effectively and reliably connect the regenerative cooling channels of each nozzle component, avoid situations such as welding beads and welding deformation, and ensure that the regenerative cooling channels are unobstructed and free of debris.

[0035] (Ⅳ) For the thrust chamber nozzle docking structure proposed by the present invention, the coaxially connected ring adopts a transverse segmented structure, which is convenient for assembly and can be applied to nozzles with different diameters. Description of the Drawings

[0036] Figure 1 It is a schematic structural diagram of a rocket engine thrust chamber nozzle.

[0037] Figure 2 It is a schematic cross-sectional view of a rocket engine thrust chamber nozzle before welding with a first gap left.

[0038] Figure 3 It is a schematic cross-sectional view of a rocket engine thrust chamber nozzle after welding with a first gap left.

[0039] Figure 4Schematic cross-sectional view before welding with a second gap and a third gap left for the nozzle of the rocket engine thrust chamber.

[0040] Figure 5 Schematic cross-sectional view after welding with a second gap and a third gap left for the nozzle of the rocket engine thrust chamber.

[0041] Figure 6 Schematic structural view of multiple coaxial connecting rings welded together.

[0042] Figure 7 Schematic structural view of the rib in the nozzle of the rocket engine thrust chamber.

[0043] The meanings of each label in the figure are as follows: 1 - nozzle converging-diverging section, 2 - nozzle diverging section, 3 - nozzle extension section, 4 - first weld seam, 5 - coaxial connecting ring, 6 - second weld seam, 7 - third weld seam, 8 - fourth weld seam, 9 - first gap, 10 - cooling channel, 11 - second gap, 12 - third gap, 13 - rib, 14 - first coaxial docking structure, 15 - coaxial docking groove, 16 - second coaxial docking structure.

[0044] 101 - inner wall of the converging section, 102 - outer wall of the converging section, 201 - inner wall of the diverging section, 202 - outer wall of the diverging section, 301 - inner wall of the extension section, 302 - outer wall of the extension section.

[0045] 501 - first outer arc section, 502 - first inner arc section, 503 - second outer arc section, 504 - second middle arc section, 505 - second inner arc section.

[0046] 10201 - first stepped section, 10202 - second stepped section, 10203 - fifth stepped section, 10204 - sixth stepped section, 20201 - third stepped section, 20202 - fourth stepped section, 20203 - seventh stepped section, 20204 - axial horizontal section.

[0047] The following further elaborates on the specific content of the present invention in conjunction with embodiments. Specific Embodiments

[0048] It should be noted that the equipment and components used in the present invention, unless otherwise specified, are all the equipment and components known in the prior art.

[0049] Complying with the above technical solutions, the following gives specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent transformations made on the basis of the technical solutions of this application fall within the protection scope of the present invention.

[0050] Embodiment 1:

[0051] This embodiment provides a docking structure for the nozzle of a rocket engine thrust chamber, as Figure 1 shown, which includes a nozzle converging-diverging section 1, a nozzle diverging section 2, and a nozzle extension section 3 connected in sequence. As Figures 2 to 5 shown, the nozzle converging-diverging section 1 includes a converging-diverging section inner wall 101 and a converging-diverging section outer wall 102 coaxially arranged outside the converging-diverging section inner wall 101. The nozzle diverging section 2 includes a diverging section inner wall 201 and a diverging section outer wall 202 coaxially arranged outside the diverging section inner wall 201. The nozzle extension section 3 includes an extension section inner wall 301 and an extension section outer wall 302 coaxially arranged outside the extension section inner wall 301. As Figure 1 shown, a first coaxial docking structure 14 is provided between the converging-diverging section outer wall 102 and the diverging section outer wall 202.

[0052] As Figures 2 to 5 shown, the first coaxial docking structure 14 includes a coaxial docking groove 15 opened between the converging-diverging section outer wall 102 and the diverging section outer wall 202. A coaxial connecting ring 5 is welded in the coaxial docking groove 15, and the coaxial connecting ring 5 makes the end faces of the nozzle converging-diverging section 1 and the nozzle diverging section 2 not in contact.

[0053] As a preferred solution of this embodiment, as Figure 2 、 Figure 3 and Figure 6 shown, the coaxial connecting ring 5 includes multiple coaxial connecting arc segments, and the multiple coaxial connecting arc segments are sequentially connected end to end in the circumferential direction to form the coaxial connecting ring 5. Adjacent two coaxial connecting arc segments are connected by a second weld 6.

[0054] As a preferred solution of this embodiment, as Figure 2 and Figure 3 shown, the coaxial connecting arc segment includes an integrally formed first outer arc segment 501 and a first inner arc segment 502. The first outer arc segment 501 is located radially outside the first inner arc segment 502, and the axial width of the first outer arc segment 501 is greater than the axial width of the first inner arc segment 502, so that the cross-section of the coaxial connecting ring 5 is in a T shape.

[0055] As a preferred solution of this embodiment, as Figure 2 shown, one side wall of the coaxial docking groove 15 is a first stepped section 10201 and a second stepped section 10202 provided on the inner end face of the converging-diverging section outer wall 102; the other side wall of the coaxial docking groove 15 is a third stepped section 20201 and a fourth stepped section 20202 provided on the inner end face of the diverging section outer wall 202.

[0056] As a preferred solution of this embodiment, as Figure 3As shown, the inner sidewalls of the first outer arc segment 501 of the coaxial connection ring 5 are respectively in contact with the sidewalls of the first stepped segment 10201 and the third stepped segment 20201; the first outer arc segment 501 of the coaxial connection ring 5 is connected to the first stepped segment 10201 through the third weld seam 7, and the first outer arc segment 501 of the coaxial connection ring 5 is connected to the third stepped segment 20201 through the fourth weld seam 8.

[0057] As a preferred solution of this embodiment, as Figure 2 and Figure 3 shown, the two axial surfaces of the first inner arc segment 502 of the coaxial connection ring 5 are respectively in partial contact with the step surfaces of the second stepped segment 10202 and the fourth stepped segment 20202, and a first gap 9 is left between the inner sidewalls of the first inner arc segment 502 of the coaxial connection ring 5 and the sidewalls of the second stepped segment 10202 and the fourth stepped segment 20202.

[0058] As a preferred solution of this embodiment, as Figure 4 and Figure 5 shown, the coaxial connection arc segment includes an integrally formed second outer arc segment 503, a second middle arc segment 504, and a second inner arc segment 505. The second outer arc segment 503 is located radially outside the second middle arc segment 504, the second middle arc segment 504 is located radially outside the second inner arc segment 505. The axial width of the second outer arc segment 503 is greater than the axial width of the second middle arc segment 504, the axial width of the second middle arc segment 504 is greater than the axial width of the second inner arc segment 505, and one axial surface of the second inner arc segment 505 is flush with one axial surface of the second middle arc segment 504.

[0059] As a preferred solution of this embodiment, as Figure 4 and Figure 5 shown, one sidewall of the coaxial docking groove 15 is the fifth stepped segment 10203 and the sixth stepped segment 10204 provided on the inner end surface of the outer wall 102 of the converging and diverging section; the other sidewall of the coaxial docking groove 15 is the seventh stepped segment 20203 and the axially straight segment 20204 provided on the inner end surface of the outer wall 202 of the expanding section.

[0060] As a preferred solution of this embodiment, as Figure 4 shown, the inner sidewall of the second outer arc segment 503 of the coaxial connection ring 5 is in contact with the sidewalls of the fifth stepped segment 10203 and the seventh stepped segment 20203; the second outer arc segment 503 of the coaxial connection ring 5 is connected to the fifth stepped segment 10203 through the third weld seam 7, and the second outer arc segment 503 of the coaxial connection ring 5 is connected to the seventh stepped segment 20203 through the fourth weld seam 8;

[0061] As a preferred solution of this embodiment, as Figure 5 shown, one axial surface of the second middle-layer arc segment 504 of the coaxial connection ring 5 is in contact with the stepped surface part of the sixth stepped segment 10204. A second gap 11 is left between the inner side wall of the second middle-layer arc segment 504 of the coaxial connection ring 5 and the side wall of the sixth stepped segment 10204. A third gap 12 is left between one axial surface of the second inner-layer arc segment 505 of the coaxial connection ring 5 and the side wall of the sixth stepped segment 10204; the other axial surfaces of the second middle-layer arc segment 504 and the second inner-layer arc segment 505 of the coaxial connection ring 5 are in complete contact with the end surface of the axial straight segment 20204. The inner side wall of the second inner-layer arc segment 505 of the coaxial connection ring 5 is not flush with the inner surfaces of the converging-diverging section outer wall 102 and the diverging section outer wall 202.

[0062] As a preferred solution of this embodiment, as Figure 2 and Figure 4 shown, the inner wall 101 of the converging-diverging section is connected to the inner wall 201 of the diverging section through the first weld 4; the first weld 4 is located directly below the coaxial connection ring 5.

[0063] Preferably in this embodiment, the first weld 4 is welded by a flush butt joint; the second weld 6 is welded by arc welding; the third weld 7 is welded by a lock butt joint; the fourth weld 8 is welded by a lock butt joint.

[0064] Preferably in this embodiment, a second coaxial docking structure 16 is provided between the outer wall 202 of the diverging section and the outer wall 302 of the extension section. The structure of the second coaxial docking structure 16 is the same as the structure of the first coaxial docking structure 14.

[0065] Preferably in this embodiment, as Figures 2 to 5 shown, a communicating cooling channel 10 is formed between the inner wall 101 of the converging-diverging section, the inner wall 201 of the diverging section, and the inner wall 301 of the extension section and the outer wall 102 of the converging-diverging section, the outer wall 202 of the diverging section, and the outer wall 302 of the extension section; as Figure 7 shown, the inner wall 101 and the outer wall 102 of the converging-diverging section are connected by ribs 13; the inner wall 201 and the outer wall 202 of the diverging section are connected by ribs 13; the inner wall 301 and the outer wall 302 of the extension section are connected by ribs 13.

[0066] Embodiment 2:

[0067] This embodiment proposes a docking method for a rocket engine thrust chamber nozzle docking structure. The docking method of this nozzle docking structure adopts the rocket engine thrust chamber nozzle docking structure proposed in Embodiment 1. The method specifically includes the following steps:

[0068] Step 1: Brazing the inner wall 101 and the outer wall 102 of the converging-diverging section, the inner wall 201 and the outer wall 202 of the diverging section, and the inner wall 301 and the outer wall 302 of the extension section together with ribs 13 respectively;

[0069] Step 2: Welding the inner wall 101 of the converging-diverging section and the inner wall 201 of the nozzle diverging section with a flat butt joint to form a first weld seam 4;

[0070] Step 3: Inserting multiple coaxial connecting rings 5 between the nozzle converging-diverging section 1 and the nozzle diverging section 2, making the inner side walls of the first outer arc segments 501 of the coaxial connecting rings 5 fit with the side walls of the first stepped segment 10201 and the third stepped segment 20201 respectively; the two axial surfaces of the first inner arc segments 502 of the coaxial connecting rings 5 partially fit with the step surfaces of the second stepped segment 10202 and the fourth stepped segment 20202 respectively, and a first gap 9 is left between the inner side walls of the first inner arc segments 502 of the coaxial connecting rings 5 and the side walls of the second stepped segment 10202 and the fourth stepped segment 20202;

[0071] Step 4: Welding the multiple coaxial connecting rings 5 inserted between the nozzle converging-diverging section 1 and the nozzle diverging section 2 in Step 3 by arc welding to form a second weld seam 6;

[0072] Step 5: Welding between the first outer arc segment 501 of the coaxial connecting ring 5 in Step 4 and the first stepped segment 10201 with a lock-bottom butt joint to form a third weld seam 7;

[0073] Step 6: Welding between the first outer arc segment 501 of the coaxial connecting ring 5 in Step 4 and the third stepped segment 20201 with a lock-bottom butt joint to form a fourth weld seam 8;

[0074] Step 7: Welding the nozzle diverging section 2 and the nozzle extension section 3 in sequence using the welding method between the nozzle converging-diverging section 1 and the nozzle diverging section 2 so that the nozzle converging-diverging section 1, the nozzle diverging section 2, and the nozzle extension section 3 are connected together.

Claims

1. A rocket engine thrust chamber nozzle docking structure, comprising a nozzle expansion section (1), a nozzle expansion section (2) and a nozzle extension section (3) connected in sequence, wherein the nozzle expansion section (1) comprises an expansion section inner wall (101), and an expansion section outer wall (102) coaxially arranged outside the expansion section inner wall (101); the nozzle expansion section (2) comprises an expansion section inner wall (201), and an expansion section outer wall (202) coaxially arranged outside the expansion section inner wall (201); the nozzle extension section (3) comprises an extension section inner wall (301), and an extension section outer wall (302) coaxially arranged outside the extension section inner wall (301), characterized in that: A first coaxial docking structure (14) is provided between the outer wall (102) of the contraction-expansion section and the outer wall (202) of the expansion section; The first coaxial docking structure (14) comprises a coaxial docking groove (15) provided between the outer wall (102) of the convergent-divergent section and the outer wall (202) of the divergent section, a coaxial connecting ring (5) being welded inside the coaxial docking groove (15), and the coaxial connecting ring (5) ensures that the end face of the convergent-divergent section (1) of the nozzle and the end face of the divergent section (2) of the nozzle are not in contact with each other.

2. The rocket engine nozzle docking structure according to claim 1, characterized in that: The coaxial connecting ring (5) comprises a plurality of coaxial connecting arc segments, which are connected end to end in the circumferential direction to form the coaxial connecting ring (5), and two adjacent coaxial connecting arc segments are connected by a second weld (6); The coaxial connecting circular arc segment comprises a first outer circular arc segment (501) and a first inner circular arc segment (502) which are integrally formed. The first outer circular arc segment (501) is located radially outside the first inner circular arc segment (502). The axial width of the first outer circular arc segment (501) is greater than the axial width of the first inner circular arc segment (502), so that the cross-section of the coaxial connecting ring (5) is T-shaped.

3. The rocket engine nozzle docking structure according to claim 2, characterized in that: One side wall of the coaxial butt groove (15) is a first step section (10201) and a second step section (10202) arranged on the inner end surface of the outer wall (102) of the contraction and expansion section; the other side wall of the coaxial butt groove (15) is a third step section (20201) and a fourth step section (20202) arranged on the inner end surface of the outer wall (202) of the expansion section; The inner side walls of the first outer circular arc segment (501) of the coaxial connecting ring (5) are respectively fitted with the side walls of the first step segment (10201) and the third step segment (20201); the first outer circular arc segment (501) of the coaxial connecting ring (5) is connected to the first step segment (10201) via a third weld (7), and the first outer circular arc segment (501) of the coaxial connecting ring (5) is connected to the third step segment (20201) via a fourth weld (8); The two axial surfaces of the first inner arc segment (502) of the coaxial connecting ring (5) are respectively fitted with the step surface portions of the second step segment (10202) and the fourth step segment (20202), and a first gap (9) is left between the inner side walls of the first inner arc segment (502) of the coaxial connecting ring (5) and the side walls of the second step segment (10202) and the fourth step segment (20202).

4. The rocket engine nozzle docking structure according to claim 2, characterized in that: The coaxially connected arc segments include an integrally formed second outer arc segment (503), a second middle arc segment (504) and a second inner arc segment (505), the second outer arc segment (503) is located radially outward of the second middle arc segment (504), the second middle arc segment (504) is located radially outward of the second inner arc segment (505), the axial width of the second outer arc segment (503) is greater than the axial width of the second middle arc segment (504), the axial width of the second middle arc segment (504) is greater than the axial width of the second inner arc segment (505), and an axial surface of the second inner arc segment (505) is flush with an axial surface of the second middle arc segment (504).

5. The rocket engine nozzle docking structure according to claim 4, characterized in that: One side wall of the coaxial butt groove (15) is a fifth step section (10203) and a sixth step section (10204) arranged on the inner end surface of the outer wall (102) of the expansion section; the other side wall of the coaxial butt groove (15) is a seventh step section (20203) and an axial straight section (20204) arranged on the inner end surface of the outer wall (202) of the expansion section; The inner side wall of the second outer circular arc segment (503) of the coaxial connecting ring (5) is in contact with the side walls of the fifth step segment (10203) and the seventh step segment (20203); the second outer circular arc segment (503) of the coaxial connecting ring (5) is connected to the fifth step segment (10203) via a third weld (7), and the second outer circular arc segment (503) of the coaxial connecting ring (5) is connected to the seventh step segment (20203) via a fourth weld (8); An axial surface of the second middle circular arc segment (504) of the coaxial connecting ring (5) is partially fitted with the step surface of the sixth step segment (10204), a second gap (11) is left between the inner side wall of the second middle circular arc segment (504) of the coaxial connecting ring (5) and the side wall of the sixth step segment (10204), and a third gap (12) is left between an axial surface of the second inner circular arc segment (505) of the coaxial connecting ring (5) and the side wall of the sixth step segment (10204); the other axial surfaces of the second middle circular arc segment (504) and the second inner circular arc segment (505) of the coaxial connecting ring (5) are completely fitted with the end face of the axial straight segment (20204), and the inner side wall of the second inner circular arc segment (505) of the coaxial connecting ring (5) is not flush with the inner surfaces of the outer wall (102) of the contraction and expansion segment and the outer wall (202) of the expansion segment.

6. The rocket engine nozzle docking structure according to claim 3 or 5, characterized in that: The inner wall (101) of the contraction-expansion section is connected to the inner wall (201) of the expansion section via a first weld (4); the first weld (4) is located directly below the coaxial connection ring (5).

7. The rocket engine nozzle docking structure according to claim 6, characterized in that: The first weld (4) is welded by a flat butt joint; the second weld (6) is welded by arc welding; the third weld (7) is welded by a bottom-locking butt joint; and the fourth weld (8) is welded by a bottom-locking butt joint.

8. The rocket engine nozzle docking structure according to any one of claims 1 to 7, characterized in that: A second coaxial docking structure (16) is provided between the outer wall (202) of the expansion section and the outer wall (302) of the extension section, and the structure of the second coaxial docking structure (16) is the same as that of the first coaxial docking structure (14).

9. The rocket engine nozzle docking structure according to claim 8, characterized in that: A cooling channel (10) is formed between the inner wall (101) of the contraction-expansion section, the inner wall (201) of the expansion section and the inner wall (301) of the extension section, and the outer wall (102) of the contraction-expansion section, the outer wall (202) of the expansion section and the outer wall (302) of the extension section; The inner wall (101) of the contraction-expansion section and the outer wall (102) of the contraction-expansion section are connected via ribs (13); the inner wall (201) of the expansion section and the outer wall (202) of the expansion section are connected via ribs (13); and the inner wall (301) of the extension section and the outer wall (302) of the extension section are connected via ribs (13).

10. A method for docking a rocket engine thrust chamber nozzle docking structure, characterized in that: The nozzle docking method adopts the rocket engine thrust chamber nozzle docking structure as claimed in claim 9, and the method specifically comprises the following steps: Step 1: brazing the inner wall (101) and the outer wall (102) of the contraction and expansion section, the inner wall (201) and the outer wall (202) of the expansion section, and the inner wall (301) and the outer wall (302) of the extension section together through ribs (13); Step 2: welding the inner wall (101) of the contraction-expansion section and the inner wall (201) of the nozzle expansion section to form a first weld (4); Step 3, inserting the multi-section coaxial connecting ring (5) between the outer wall of the contraction and expansion section (102) and the outer wall of the expansion section (202); Step 4, welding the multiple sections of coaxial connecting rings (5) inserted between the outer wall of the contraction and expansion section (102) and the outer wall of the expansion section (202) in step 3 to form a second weld (6); Step 5, welding the outer wall (102) of the expansion section to the first outer arc section (501) of the coaxial connecting ring (5) in step 3 to form a third weld (7); Step six, welding the outer wall (202) of the expansion section to the first outer arc segment (501) of the coaxial connecting ring (5) in step three to form a fourth weld (8); Step seven, the nozzle expansion section (2) and the nozzle extension section (3) are welded in sequence using the welding method between the nozzle expansion section (1) and the nozzle expansion section (2) so that the nozzle expansion section (1), the nozzle expansion section (2) and the nozzle extension section (3) are connected together.

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