Ablation-resistant spray pipe based on boundary layer effect

Abstract

The invention discloses an ablation-resistant spray pipe based on a boundary layer effect, and belongs to the technical field of solid rocket engines. A fuel gas generator combustion chamber shell is arranged at the position, close to a convergence section, of the outer diameter of a straight barrel section of a shell, and the shell is used for installing a fuel gas generator; the low-combustion-temperature fuel gas generator releases low-combustion-temperature propellant fuel gas on the wall face of the convergence section lining to form a boundary layer, and therefore erosion and ablation of high-temperature fuel gas of an engine to the convergence section lining of the spray pipe are actively weakened. The problem that in an existing nozzle convergence section adopting a heat insulation layer passive thermal protection structure, when an engine adopts a propellant with the high metal content and bears high overload, a heat insulation layer of the convergence section is difficult to resist erosion and ablation of engine gas is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of solid rocket engines, and in particular relates to an ablation-resistant nozzle based on boundary layer effect. Background Art

[0002] The combustion chamber of a solid rocket engine has a high combustion temperature, reaching approximately 3200K. The combustion gas often contains a large number of condensed phase particles. During engine operation, this high-temperature combustion gas, containing a large number of condensed phase particles, is accelerated from subsonic to supersonic speeds as it is discharged through the Laval nozzle to generate thrust. During this process, the high-temperature combustion gas inevitably erodes and ablates the nozzle convergent section lining at a certain angle, which can easily lead to rapid burn-through and failure of the nozzle convergent section. Especially when the engine experiences high lateral overload, the erosion and ablation of the nozzle convergent section by the combustion gas and condensed phase particles increases dramatically, significantly increasing the risk of nozzle failure. To ensure the reliable operation of solid rocket engines, thermal protection of the nozzle convergent section is essential.

[0003] Patent publication number CN110080909B discloses a nozzle for a solid rocket engine, which includes a convergent section insulation layer, a diffuser section insulation layer, and a shell bearing layer. The shell bearing layer includes a first section that abuts the convergent section insulation layer and a second section connected to the first section. The second section is connected to the diffuser section insulation layer. The outer wall of the first section is provided with a protruding bonding head. The two sides of the bonding head are used to bond with the inner wall of the combustion chamber shell and the combustion chamber insulation layer respectively. The outer wall of the first section is used to abut the combustion chamber shell. In this invention patent, a thicker convergent section insulation layer is designed on the inner wall of the nozzle convergent section. The insulation layer passively protects against the ablation and particle scouring of the nozzle convergent section by the combustion gas during the operation of the engine, thereby achieving thermal protection of the nozzle convergent section. This method is currently the commonly used thermal protection technology approach for solid rocket engines. However, when the engine uses propellants with a high metal content and is subjected to high overload, passive thermal protection through the insulation layer alone is difficult to completely resist the erosion and ablation of the combustion gas, resulting in reduced engine quality and reliability and even the risk of nozzle burn-through.

[0004] Therefore, there is an urgent need for a nozzle with an ablation-resistant convergent section to reduce the erosion and ablation damage of the fuel gas to the convergent section of the nozzle, thereby improving the quality and reliability of the engine, especially when the engine uses high-energy, high-metal content propellants and high overload conditions. Summary of the Invention

[0005] Technical issues to be solved:

[0006] To overcome the shortcomings of existing technologies, the present invention provides an ablation-resistant nozzle based on the boundary layer effect. A low-temperature gas generator is mounted outside the nozzle housing. This low-temperature gas generator releases low-temperature propellant gas onto the inner lining of the converging section, forming a boundary layer. This actively reduces the erosion and ablation of the nozzle's converging section lining by the engine's high-temperature gas. This addresses the problem that existing nozzle convergent sections, which rely on passive thermal insulation for protection, are unable to withstand erosion and ablation from the engine's gas when using propellants with high metal content and when the engine is subjected to high overload.

[0007] The technical solution of the present invention is: an ablation-resistant nozzle based on the boundary layer effect, comprising a shell and a lining applied to the inner wall of the shell for thermal insulation protection; the shell is an integral rotating cylinder having a convergent section and a straight section, the lining applied to the convergent section is the convergent section lining, and the lining applied to the straight section is the straight section lining;

[0008] A gas generator combustion chamber shell is provided at the outer diameter of the straight cylindrical section of the shell near the convergent section for installing the gas generator; a recess is provided on the inner wall of the convergent section of the shell, and a cavity is formed between the recess and the lining of the convergent section; a plurality of first through holes are provided on the side wall of the gas generator combustion chamber shell facing the convergent section of the shell, and the first through holes penetrate the inner cavity of the gas generator combustion chamber shell and the recess; a plurality of second through holes penetrating to the cavity are provided along the axial direction of the shell on the convergent section lining; the gas generator is installed to generate low combustion temperature gas of 800-1500K, and the low temperature gas flows through the first through holes and the second through holes to form a boundary layer on the wall of the convergent section lining facing away from the convergent section of the shell, which is used to resist the erosion and ablation of the high temperature gas of the engine.

[0009] A further technical solution of the present invention is: the gas generator combustion chamber shell and the shell are of an integral structure, the gas generator combustion chamber shell is an annular shell with one side open, and is composed of a front side plate, an outer ring plate and a section of the outer wall of the straight cylindrical section of the shell; the front side plate faces the convergent section of the shell and is structurally integrated with it, the outer ring plate is coaxial with the straight cylindrical section of the shell, and the side of the gas generator combustion chamber shell opposite to the front side plate is open; multiple first through holes are evenly distributed on the same circumference of the front side plate.

[0010] A further technical solution of the present invention is that the inner recess is arranged in an annular shape along the inner wall of the convergent section of the shell, and the inner recess is entirely coaxial with the shell; an annular cavity with an irregular cross-section is formed between the inner recess and the inner lining of the convergent section.

[0011] A further technical solution of the present invention is: multiple second through holes are distributed around the circumference of the convergent section lining and are parallel to the shell axis; the second through hole is provided with a tapered hole section and a straight hole section, the tapered hole section is located at the end of the convergent section lining away from the recessed portion, and the straight hole section is connected to the recessed portion; the tapered hole section is used to install a sealing plug, and the sealing plug is used to seal the second through hole when the gas generator is not working.

[0012] A further technical solution of the present invention is: the gas generator includes an insulating layer, an ignition box, an ignition threaded plug, a covering sleeve, a powder column and a head; the insulating layer is adhered to the inner cavity wall of the gas generator combustion chamber shell for thermal insulation protection; the front side plate is provided with two threaded holes for installing the ignition threaded plug; the ignition box is annular and adhered to the inner wall of the front side plate covered with the insulating layer, the ignition wire of the ignition box is connected with the wire of the ignition threaded plug, and the ignition threaded plug and the ignition box are used to ignite the powder column; the powder column is a low-ignition-temperature solid propellant powder column, and its structure is annular with a rectangular cross-section. The powder column is installed in the inner cavity of the gas generator combustion chamber shell, and the side of the powder column facing the ignition box is the combustion surface, and the other sides of the powder column are covered by the covering sleeve to limit combustion; the head is installed at the open end of the gas generator combustion chamber shell through a sealing fixing assembly to close the opening of the gas generator combustion chamber shell.

[0013] A further technical solution of the present invention is: the sealing and fixing assembly includes an external threaded pressure ring, an internal threaded pressure ring, a third sealing ring and a fourth sealing ring; the head is an annular plate, and its inner wall is axially provided with an annular boss, and a limiting step surface is formed between the boss and the inner and outer diameters of the head, and the limiting step surface is abutted against the limiting ring provided at the open end of the combustion chamber shell of the gas generator; the limiting ring is used to limit the movement of the head toward the direction of the medicine column; the third sealing ring and the fourth sealing ring are respectively located at the outer diameter and inner diameter of the boss, and are used for sealing at the contact surface between the boss and the limiting ring; the external threaded pressure ring is embedded in the outer ring plate and is threadedly connected to the outer ring plate; the internal threaded pressure ring is sleeved on the outer diameter of the straight cylinder section and is threadedly connected to the straight cylinder section; the external threaded pressure ring and the internal threaded pressure ring are installed on the same plane, and are both used to fix the head.

[0014] A further technical solution of the present invention is: the convergent section lining and the straight section lining are an integrated structure, coaxially embedded in the inner cavity of the shell, and the convergent section lining and the straight section lining are respectively glued and fixed to the inner wall surfaces of the convergent section and the straight section of the shell; the end of the convergent section lining away from the straight section lining is the engine gas inlet end, and a first sealing ring is installed at the outer diameter of the convergent section lining close to the gas inlet end, which is sealed with the inner wall of the convergent section of the shell; a second sealing ring is installed on the outer diameter of the straight section lining, which is sealed with the inner wall of the straight section of the shell.

[0015] A further technical solution of the present invention is: the ablation-resistant nozzle also includes an expansion section shell, an expansion section liner and a nozzle throat liner; the expansion section shell is a rotating shell, one end of which is threadedly connected to the end of the straight section of the shell away from the convergent section, and the other end is an expansion open structure; the inner wall of the expansion section shell is affixed with an expansion section liner for thermal insulation protection; the nozzle throat liner is located between the straight section liner and the expansion section liner, is coaxial with and in surface contact with the two, and is used for thermal insulation protection of the nozzle throat.

[0016] A further technical solution of the present invention is: the inner wall of the straight cylinder section of the shell is coaxially provided with an equal diameter portion and a tapered hole portion, the equal diameter portion is close to the convergent section of the shell, and the straight cylinder section liner is installed on the equal diameter portion; the tapered hole portion is located near one end of the expansion section shell, and is used to cooperate with the conical outer wall surface of the nozzle throat liner; the tapered hole of the tapered hole portion shrinks along the direction close to the expansion section shell.

[0017] A further technical solution of the present invention is that a fifth sealing ring is provided at the threaded connection between the expansion section housing and the straight section, for airtight protection of the connection between the two.

[0018] Beneficial effects

[0019] The beneficial effects of the present invention are as follows: the present invention is an ablation-resistant nozzle based on the boundary layer effect, a low-temperature gas generator is installed outside the nozzle, the annular combustion chamber shell of the gas generator is integrated with the convergent section and the straight section of the nozzle shell into an integrated structure, the inner cavity of the gas generator combustion chamber shell is connected with the recessed portion provided in the convergent section of the shell through a plurality of first through holes, the inner lining of the convergent section is provided with a plurality of second through holes penetrating the outer end surface and the inner recessed cavity along the axial direction, and the gas generator located in the combustion chamber shell of the gas generator is ignited after the gas generator is in operation The generated low combustion temperature combustion gas is ejected through the first through hole and the second through hole, and forms a boundary layer on the outer wall of the convergent section lining, thereby actively protecting the convergent section lining from being eroded and burned by the high-temperature combustion gas of the engine, so that the nozzle convergent section (including the convergent section lining and the convergent section of the shell) still has high reliability under the condition of a thinner insulation lining. When the engine uses a propellant with a high metal content and the engine is overloaded, the anti-erosion and ablation ability of the nozzle convergent section lining is significantly improved, preventing the nozzle convergent section from burning through, and ensuring the normal operation of the engine.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. The low combustion temperature gas generated by the gas generator is ejected from the second through hole of the nozzle convergent section liner and forms a boundary layer on the surface of the nozzle convergent section liner. This can reduce the flow of high-temperature gas in the engine combustion chamber to the surface of the nozzle liner, weaken the convective heat transfer between the high-temperature gas and the surface of the nozzle convergent section liner, and improve the ablation resistance of the nozzle convergent section liner.

[0022] 2. The low combustion temperature gas produced by the gas generator is ejected from the second through hole of the nozzle convergent section lining and forms a boundary layer on the surface of the nozzle convergent section lining, which can reduce the impact velocity of the condensed phase particles in the high-temperature gas on the surface of the nozzle convergent section lining, thereby improving the anti-particle scouring performance of the nozzle convergent section lining.

[0023] 3. The second through-holes of this invention are provided with tapered sections at their ends. Sealing plugs are installed to seal the second through-holes, ensuring that all second through-holes remain blocked when the gas generator is not ignited. This effectively prevents the engine's high-temperature fuel gas from flowing into the annular gas generator combustion chamber when the gas generator is not operating, thereby ensuring the high reliability of the gas generator. When the gas generator is operating, the pressure generated by the low-temperature fuel gas within the gas generator combustion chamber housing can unidirectionally dislodge the sealing plugs, without affecting the formation of a boundary layer on the inner lining surface of the nozzle convergent section.

[0024] 4. The number and distribution of the second through-holes in this invention can be adjusted based on the severity of localized ablation during high-temperature overload conditions, thereby regulating the flow distribution of the low-temperature combustion gas ejected from the second through-holes. In areas with severe ablation, the density of the second through-holes can be increased to increase the boundary layer thickness of the low-temperature gas in those areas, thereby improving the localized ablation resistance of the nozzle convergent section lining.

[0025] 5. The diameter of the first through-holes of the present invention can be adjusted as needed. By varying the diameter of the first through-holes, the low-temperature gas generated by the gas generator can be blocked through each of the first through-holes, thereby stabilizing the pressure in the combustion chamber of the annular gas generator and avoiding fluctuations in the burning rate of the low-temperature propellant. This allows for a constant flow rate of the low-temperature gas injected by the annular gas generator into the converging section liner, thereby improving the ablation resistance of the nozzle converging section liner and ensuring that the injection of the low-temperature gas does not affect the stable combustion of the engine's main charge. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a main cross-sectional view of an ablation-resistant nozzle based on the boundary layer effect of the present invention;

[0027] Figure 2 Schematic diagram of the structure of the shell, wherein (a) is a main sectional view of the shell, (b) is a left view of the shell, and (c) is a right view of the shell;

[0028] Figure 3 Schematic diagram of the structure of the lining, wherein (d) is a main cross-sectional view of the lining, (e) is a left view of the lining, and (f) is a right view of the lining;

[0029] Figure 4 Schematic diagram of the insulation layer structure of the gas generator, wherein (g) is a main cross-sectional view of the insulation layer, and (h) is a left view of the insulation layer;

[0030] Figure 5 Schematic diagram of the structure of the covering sleeve, wherein (i) is a main cross-sectional view of the covering sleeve, and (j) is a left side view of the covering sleeve;

[0031] Figure 6 Schematic diagram of the structure of the head, where (k) is the main sectional view of the head and (l) is the left view of the head;

[0032] Figure 7 Schematic diagram of the structure of the external thread pressure ring, wherein (m) is the main cross-sectional view of the external thread pressure ring, (n) is the left view of the external thread pressure ring, and (o) is the right view of the external thread pressure ring;

[0033] Figure 8 Schematic diagram of the structure of the internal thread pressure ring, wherein (p) is the main cross-sectional view of the internal thread pressure ring, (q) is the left view of the internal and external thread pressure ring, and (r) is the right view of the internal thread pressure ring;

[0034] Figure 9 Schematic diagram of the structure of the nozzle throat liner, where (s) is the main cross-sectional view of the nozzle throat liner, and (t) is the left view of the nozzle throat liner;

[0035] Figure 10 Schematic diagram of the structure of the expansion section shell, wherein (u) is a main sectional view of the expansion section shell, and (v) is a left view of the expansion section shell;

[0036] Figure 11 Schematic diagram of the structure of the expansion section lining, wherein (w) is the main cross-sectional view of the expansion section lining, and (x) is the right side view of the expansion section lining;

[0037] Figure 12 It is a structural diagram of the ignition cartridge; wherein (y) is the main cross-sectional view of the ignition cartridge, and (z) is the right side view of the ignition cartridge.

[0038] Figure 13 for Figure 1 A partial enlarged view of point A in the middle.

[0039] Explanation of reference numerals: 1. Shell, 11. Converging section, 111. Recessed portion, 12. Straight section, 121. Equal diameter portion, 122. Tapered hole portion, 13. Gas generator combustion chamber shell, 131. First through hole, 132. Front side plate, 133. Outer ring plate, 134. First limiting ring, 135. Second limiting ring, 136. Threaded hole, 2. Liner, 21. Converging section lining, 211. Second through hole, 22. Straight section lining, 3. Combustion chamber Gas generator, 31. Insulation layer, 32. Ignition cartridge, 33. Ignition threaded plug, 34. Coating sleeve, 35. Grain column, 36. Head, 361. Boss, 37. External thread pressure ring, 38. Internal thread pressure ring, 39. Third sealing ring, 310. Fourth sealing ring, 4. Cavity, 5. Sealing plug, 6. First sealing ring, 7. Second sealing ring, 8. Expansion section shell, 9. Expansion section liner, 10. Nozzle throat liner, 101. Fifth sealing ring. DETAILED DESCRIPTION

[0040] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0041] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0042] This embodiment provides an ablation-resistant nozzle based on the boundary layer effect, which is installed on a solid rocket engine. A low-combustion-temperature gas generator is installed outside the nozzle, and the low-combustion-temperature propellant gas is released on the inner lining wall of the convergent section of the nozzle through the gas generator, thereby forming a boundary layer on the outer wall of the inner lining of the convergent section, that is, the wall facing the high-temperature gas inlet of the engine, thereby weakening the erosion and ablation of the inner lining of the convergent section of the nozzle by the high-temperature gas of the engine, and improving the ablation resistance of the nozzle.

[0043] See Figure 1 In this embodiment, an ablation-resistant nozzle based on the boundary layer effect is a rotating hollow cylindrical structure, which is provided with a convergent part, a straight part and an expansion part in sequence. The high-temperature combustion gas of the engine enters from the convergent part and is then ejected from the expansion part. The nozzle throat is located between the straight part and the expansion part, and a nozzle throat liner 10 is installed inside.

[0044] See Figure 1 、 2In this embodiment, the converging portion and the straight-tube portion form a monolithic structure, comprising a one-piece metal shell 1 and a monolithic lining 2 coaxially attached to the inner wall of the shell 1 for thermal insulation. The one-piece shell 1 is a rotating cylindrical structure, comprising a conical converging section 11 and a cylindrical straight-tube section 12. The converging section 11 gradually converges and transitions to the straight-tube section 12, with the gas inlet located at the end of the converging section 11.

[0045] The integral liner 2 is coaxially embedded in the inner cavity of the shell 1. The liner applied to the inner wall of the convergent section 11 of the shell 1 is the convergent section liner 21, and the liner applied to the inner wall of the straight section 12 of the shell 1 is the straight section liner 22. The convergent section liner 21 and the straight section liner 22 are respectively fixed to the inner wall surfaces of the convergent section 11 and the straight section 12 of the shell using high-temperature resistant adhesive. A first sealing ring 6 is installed on the outer diameter of the convergent section liner 21 near the gas inlet end for sealing with the inner wall of the convergent section 11 of the shell 1. A second sealing ring 7 is installed on the outer diameter of the straight section liner 22 for sealing with the inner wall of the straight section 12 of the shell 1. The first sealing ring 6 and the second sealing ring 7 are both installed in the corresponding sealing ring grooves on the liner 2. The first sealing ring 6 and the second sealing ring 7 achieve a seal between the inner wall of the shell 1 and the liner 2.

[0046] A gas generator combustion chamber housing 13 is provided at the outer diameter of the straight section 12 of the housing 1 near the convergent section 11 for mounting the gas generator 3. The gas generator combustion chamber housing 13 also serves as the mounting shell of the gas generator 3 and is an integral structure with the housing 1. Figure 2 The gas generator combustion chamber shell 13 is an annular shell with one side open, consisting of a front side plate 132, an outer ring plate 133, and a section of the outer wall of the straight section 12 of the shell. The front side plate 132 is perpendicular to the axis of the shell 1, facing the convergent section 11 of the shell 1 and structurally integrated with it. The outer ring plate 133 is an annular plate, which is coaxially arranged with the straight section 12 of the shell 1 and is located on the side of the front side plate 132 on the outer diameter away from the convergent section 11. The side of the gas generator combustion chamber shell 13 opposite the front side plate 132 is open, forming an annular open end. The gas generator combustion chamber shell 13 forms an inner cavity with a rectangular cross-section.

[0047] A recessed portion 111 is formed along the inner wall of the converging section 11 of the housing 1, forming a fully annular cavity 4 with an irregular cross-section. Eight first through-holes 131 with a diameter of 3.2 mm are provided on the front side plate 132 of the gas generator combustion chamber housing 13. These eight first through-holes 131 are uniformly distributed along the circumference of the front side plate 132 and penetrate the interior cavity of the gas generator combustion chamber housing 13 and the recessed portion 111. The first sealing ring 6 and the second sealing ring 7 ensure the airtightness of the cavity 4.

[0048] Also, see Figure 3 The converging section liner 21 is provided with a plurality of second through-holes 211 extending axially along the housing 1 to the recessed portion 111, forming the cavity 4. The plurality of second through-holes 211 are distributed around the converging section liner 21 and are parallel to the axis of the housing 1. In this embodiment, the plurality of second through-holes 211 are distributed on three concentric circles, with eight second through-holes 211 distributed on each concentric circle. The circumference of the second through-holes 211 is coaxial with the axis of the converging section liner 21.

[0049] See Figure 1 、 13 The second through-hole 211 comprises a tapered section and a straight section. The tapered section is located at the end of the converging section liner 21 away from the recessed portion 111, while the straight section connects to the recessed portion 111. A sealing plug 5 is installed in the tapered section of each second through-hole 211. The sealing plug 5 is a solid conical structure with an inclined bottom surface, i.e., the outer mounting end surface, that aligns with the outer end surface of the converging section liner 21. The sealing plug 5 is bonded to the tapered section of the second through-hole 211 with a high-temperature resistant adhesive. The sealing plug 5 is used to seal the second through-hole 211 when the gas generator 3 is not in operation.

[0050] Considering that the heat flux density of the engine's main charge gas increases as the cross-sectional area decreases along the nozzle's convergent section, the heat flux density is higher at the tapered end of the convergent section liner 21, posing a higher risk of ablation. Therefore, the straight hole diameters of the three circles of second through holes 211 arranged on the conical surface of the convergent section liner 21 are 1.8 mm, 2.0 mm, and 2.2 mm, respectively, as the distribution circle moves from the outside to the inside. It should be noted that the arrangement of the second through holes 211 can also be determined based on the severity of local ablation during high-temperature overload conditions. In other embodiments, the density of the second through holes 211 can be increased in areas with severe ablation to increase the flow rate of low-temperature gas in that area, thereby increasing the boundary layer thickness of the low-temperature gas in that area and improving the local ablation resistance of the nozzle's convergent section liner 21.

[0051] The gas generator 3 is installed to generate low combustion temperature gas of 800-1500K. The low combustion temperature gas flows through the first through hole 131 and the second through hole 211 to form a boundary layer on the wall surface of the convergent section 11 of the convergent section liner 21 facing away from the convergent section 11 of the shell 1, which is used to actively resist the erosion and ablation of the high temperature gas of the engine.

[0052] For details, see Figure 1 、 2 , Figure 4-12 The gas generator 3 includes a gas generator combustion chamber shell 13, an insulation layer 31, an ignition cartridge 32, an ignition threaded plug 33, a covering sleeve 34, a charge column 35, a head 36, an external threaded pressure ring 37, an internal threaded pressure ring 38, a third sealing ring 39 and a fourth sealing ring 310.

[0053] The gas generator combustion chamber housing 13 is part of the monolithic housing 1 and also forms the outer shell of the gas generator 3. A thermal insulation layer 31 is adhered to the inner wall of the gas generator combustion chamber housing 13, providing thermal insulation and protection. The thermal insulation layer 31 is annular, with a cross-sectional shape that matches the inner cavity of the gas generator combustion chamber housing 13 and an open end oriented in the same direction as the open end of the gas generator combustion chamber housing 13. The sidewall where the thermal insulation layer 31 is adhered to the front side plate 132 is provided with through-holes corresponding to the eight first through-holes 131, ensuring continuity between the first through-holes 131 and the inner cavity of the gas generator combustion chamber housing 13.

[0054] Two threaded holes 136 are evenly distributed along the same circumference of the front side plate 132 for mounting two ignition threaded plugs 33. The ignition threaded plugs 33 are externally threaded and threadedly connected to the threaded holes 136. The ignition cartridge 32 is annular and contains 20g of boron / potassium nitrate ignition powder. The ignition cartridge 32 is bonded to the inner wall of the front side plate 132, which is covered with a thermal insulation layer, using high-temperature resistant adhesive. Multiple ignition holes are evenly distributed on the side facing away from the front side plate 132 for igniting the charge 35. The ignition wires of the ignition cartridge 32 are connected to the wires of the ignition threaded plugs 33. The ignition threaded plugs 33 and the ignition cartridge 32 cooperate to ignite the charge 35.

[0055] The charge 35 is a low combustion temperature solid propellant charge, and its structure is annular with a rectangular cross-section. The annular charge 35 is installed in the inner cavity of the gas generator combustion chamber shell 13. The side of the charge 35 facing the ignition cartridge 32 is the combustion surface, and the remaining surfaces of the charge 35 are covered by a covering sleeve 34 to limit combustion.

[0056] The end cap 36 is sealed and fixed to the open end of the gas generator combustor housing 13, sealing the annular opening. Specifically, the end cap 36 is an annular plate with an annular boss 361 axially disposed on the side facing the charge 35. The boss 361 forms a stoppered surface between the inner and outer diameters of the annular end cap 36. This stoppered surface abuts against a stopper ring provided at the open end of the gas generator combustor housing 13, preventing the end cap 36 from moving toward the charge 35. The stopper rings include a first stopper ring 134 provided on the inner wall of the outer ring plate 133 and a second stopper ring 135 provided on the outer diameter of the straight cylindrical section 12 of the housing. The first and second stopper rings 134, 135 are coplanar to ensure the flatness of the end cap 36 during installation. A third sealing ring 39 is installed in a sealing ring groove provided on the outer diameter of the boss 361, sealing between the outer diameter of the boss 361 and the inner diameter of the first stopper ring 134. The fourth sealing ring 310 is installed in the sealing ring groove provided on the outer diameter of the second limiting ring 135, and is used to seal between the outer diameter of the second limiting ring 135 and the inner diameter of the boss 136. The airtight seal between the head 36 and the combustion chamber shell 13 of the gas generator is achieved by the third sealing ring 39 and the fourth sealing ring 310. The external thread pressing ring 37 and the internal thread pressing ring 38 are used to fix the head 36 to prevent it from moving. The external thread pressing ring 37 is annular and has a 1.5mm trapezoidal external thread. The external thread pressing ring 37 is embedded in the outer ring plate 133 and is connected to the internal thread provided at the outer end of the outer ring plate 133. There are four rectangular grooves evenly distributed along the circumference of the side of the external thread pressing ring 37 facing away from the head 36, which are used to cooperate with the installation tool to facilitate its screwing installation. The internally threaded pressure ring 38 is annular and fits over the outer diameter of the straight section 12 of the housing 1. It features a 1.5mm trapezoidal internal thread that connects to the corresponding external thread on the straight section 12 of the housing 1. Four rectangular grooves are evenly distributed around the circumference of the internally threaded pressure ring 38 on the side facing away from the end cap 36 to facilitate screwing and installation with the installation tool. The externally threaded pressure ring 37 and the internally threaded pressure ring 38 are installed coplanarly to ensure the flatness of the end cap 36.

[0057] The nozzle's expansion section comprises an expansion section housing 8 and an expansion section liner 9. The expansion section housing 8 is a rotating, thin-walled metal shell, one end of which is threadedly connected to the end of the straight section 12 of the shell 1, away from the convergent section 11. The other end is an expandable, open structure. The connection between the expansion section housing 8 and the straight section 12 of the shell 1 is provided with a 1.5mm trapezoidal internal thread, which is coaxially threaded with the corresponding external thread of the straight section 12 of the shell. A fifth sealing ring 101 is installed at the threaded connection between the expansion section housing 8 and the straight section 12 of the shell to ensure airtightness. A sealing ring groove for the fifth sealing ring 101 is provided at the external threaded end of the straight section 12 of the shell. The expansion section liner 9 is applied to the inner wall of the expansion section housing 8 for thermal insulation. The expansion section liner 9 is a conical shell structure, with the outer wall of the expansion section liner 9 having the same taper angle as the inner wall of the expansion section housing 8. The outer taper of the expansion section liner 9 is bonded to the inner wall of the expansion section housing 8 using high-temperature-resistant adhesive.

[0058] The inner wall of the straight section 12 of the shell is provided with a constant diameter portion 121 and a tapered bore portion 122. The constant diameter portion 121 is located near the converging section 11 of the shell and has the same inner diameter. The straight section liner 22 is mounted on the constant diameter portion 121. The tapered bore portion 122 is located near one end of the diverging section shell 8 and is designed to mate with the conical outer wall of the nozzle throat liner 10. The nozzle throat liner 10 is made of carbon-carbon composite material and is mounted on the tapered bore portion 122. The nozzle throat liner 10 is located between the straight section liner 22 and the diverging section liner 9, coaxially and in surface contact with both, providing thermal insulation protection for the nozzle throat. The tapered bore of the tapered bore portion 122 converges as it approaches the diverging section shell 8.

[0059] When the nozzle is working, the ignition cartridge 32 ignites the charge 35 in the gas generator 3, and the low combustion temperature gas generated enters the cavity 4 formed by the recessed portion 111 of the shell convergent section 11 and the convergent section lining 21 through the first through hole 131, and then is ejected along the multiple second through holes 211 set in the convergent section lining 21, washing away the sealing plug 5 installed at the end of the second through hole 211, forming a boundary layer on the surface of the convergent section lining 21, preventing the high-temperature gas of the engine main charge from flowing to the surface of the convergent section lining 21, thereby weakening the convective heat transfer and scouring of the high-temperature gas of the engine main charge on the nozzle convergent section lining 21, thereby improving the ablation resistance of the nozzle convergent section lining 21 and improving the scouring and ablation resistance of the nozzle.

[0060] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention.

Claims

1. An ablation-resistant nozzle based on the boundary layer effect, comprising a shell and a lining applied to the inner wall of the shell 1 for thermal insulation protection; characterized in that: The shell is an integral rotating cylinder, provided with a convergent section and a straight section. The lining applied to the convergent section is the convergent section lining, and the lining applied to the straight section is the straight section lining. A gas generator combustion chamber shell is provided at the outer diameter of the straight cylindrical section of the shell near the convergent section for installing the gas generator; a recess is provided on the inner wall of the convergent section of the shell, and a cavity is formed between the recess and the convergent section lining; a plurality of first through holes are provided on the side wall of the gas generator combustion chamber shell facing the convergent section, and the first through holes penetrate the inner cavity and the recess of the gas generator combustion chamber shell; a plurality of second through holes penetrating to the cavity are provided along the axial direction of the shell on the convergent section lining; the installed gas generator is used to generate low combustion temperature gas of 800-1500K, and the low combustion temperature gas flows through the first through holes and the second through holes, forming a boundary layer on the wall surface of the convergent section lining facing away from the convergent section of the shell, which is used to resist the erosion and ablation of the high-temperature gas of the engine.

2. The ablation-resistant nozzle based on the boundary layer effect according to claim 1, characterized in that: The gas generator combustion chamber shell and the shell are of an integral structure. The gas generator combustion chamber shell is an annular shell with one side open, and is composed of a front side plate, an outer ring plate and a section of the outer wall of the straight section of the shell; the front side plate faces the convergent section of the shell and is structurally integrated with it, the outer ring plate is coaxial with the straight section of the shell, and the side of the gas generator combustion chamber shell opposite to the front side plate is open; multiple first through holes are evenly distributed on the same circumference of the front side plate.

3. The ablation-resistant nozzle based on the boundary layer effect according to claim 2, characterized in that: The inner concave portion is arranged in an annular shape along the inner wall of the convergent section of the shell, and the inner concave portion is coaxial with the shell as a whole; an annular cavity with an irregular cross section is formed between the inner concave portion and the inner lining of the convergent section.

4. The ablation-resistant nozzle based on the boundary layer effect according to claim 3, characterized in that: Multiple second through holes are distributed around the circumference of the convergent section lining and are parallel to the axis of the shell; the second through hole is provided with a tapered hole section and a straight hole section, the tapered hole section is located at the end of the convergent section lining away from the recessed portion, and the straight hole section is connected to the recessed portion; the tapered hole section is used to install a sealing plug, and the sealing plug is used to seal the second through hole when the gas generator is not working.

5. The ablation-resistant nozzle based on the boundary layer effect according to claim 4, characterized in that: The gas generator includes an insulating layer, an ignition box, an ignition threaded plug, a covering sleeve, a powder column and a head; the insulating layer is pasted on the inner cavity wall of the gas generator combustion chamber shell for thermal insulation protection; two threaded holes are provided on the front side plate for installing the ignition threaded plug; the ignition box is annular and is glued to the inner wall of the front side plate covered with the insulating layer, the ignition wire of the ignition box is connected with the wire of the ignition threaded plug, and the ignition threaded plug and the ignition box are used to ignite the powder column; the powder column is a low-ignition-temperature solid propellant powder column, and its structure is annular with a rectangular cross-section. The powder column is installed in the inner cavity of the gas generator combustion chamber shell, and the side of the powder column facing the ignition box is the combustion surface, and the remaining surfaces of the powder column are covered by the covering sleeve to limit combustion; the head is installed on the open end of the gas generator combustion chamber shell through a sealing and fixing assembly to close the opening of the gas generator combustion chamber shell.

6. The ablation-resistant nozzle based on the boundary layer effect according to claim 5, characterized in that: The sealing and fixing assembly includes an external threaded pressure ring, an internal threaded pressure ring, a third sealing ring and a fourth sealing ring; the head is an annular plate, and its inner wall is axially provided with an annular boss, and a limiting step surface is formed between the boss and the inner and outer diameters of the head, and the limiting step surface is abutted against the limiting ring provided at the open end of the combustion chamber shell of the gas generator; the limiting ring is used to limit the movement of the head toward the direction of the medicine column; the third sealing ring and the fourth sealing ring are respectively located at the outer diameter and inner diameter of the boss, and are used for air sealing at the contact surface between the boss and the limiting ring; the external threaded pressure ring is embedded in the outer ring plate and is threadedly connected to the outer ring plate; the internal threaded pressure ring is sleeved on the outer diameter of the straight cylinder section of the shell and is threadedly connected to the straight cylinder section; the external threaded pressure ring and the internal threaded pressure ring are installed in the same plane, and are both used to fix the head.

7. The ablation-resistant nozzle based on the boundary layer effect according to claim 1, characterized in that: The convergent section lining and the straight section lining are an integrated structure and are coaxially embedded in the inner cavity of the shell. The convergent section lining and the straight section lining are respectively glued and fixed to the inner wall surfaces of the convergent section and the straight section of the shell; the end of the convergent section lining away from the straight section lining is the engine gas inlet end, and a first sealing ring is installed at the outer diameter of the convergent section lining close to the gas inlet end, which is sealed with the inner wall of the convergent section of the shell; a second sealing ring is installed at the outer diameter of the straight section lining, which is sealed with the inner wall of the straight section of the shell.

8. The ablation-resistant nozzle based on the boundary layer effect according to claim 7, characterized in that: The ablation-resistant nozzle also includes an expansion section shell, an expansion section liner and a nozzle throat liner; the expansion section shell is a rotating shell, one end of which is threadedly connected to the end of the straight section of the shell away from the convergent section, and the other end is an expansion open structure; the inner wall of the expansion section shell is affixed with the expansion section liner for thermal insulation protection; the nozzle throat liner is located between the straight section liner and the expansion section liner, is coaxial with and in surface contact with the two, and is used for thermal insulation protection of the nozzle throat.

9. The ablation-resistant nozzle based on the boundary layer effect according to claim 8, characterized in that: The inner wall of the straight section of the shell is coaxially provided with an equal diameter portion and a tapered hole portion, the equal diameter portion is close to the convergent section of the shell, and the straight section liner is installed on the equal diameter portion; the tapered hole portion is located near one end of the expansion section shell, and is used to cooperate with the conical outer wall surface of the nozzle throat liner; the tapered hole of the tapered hole portion shrinks along the direction close to the expansion section shell.

10. The ablation-resistant nozzle based on the boundary layer effect according to claim 8, characterized in that: A fifth sealing ring is installed at the threaded connection between the expansion section housing and the straight section of the housing to ensure airtightness at the connection between the two.

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