Ablation-resistant solid rocket engine nozzle and method of making same

Abstract

The present application belongs to the technical field of solid rocket engine nozzle, and particularly relates to a kind of ablation-resistant solid rocket engine nozzle and a preparation method thereof.The method comprises the following steps: processing the flange structure of the expansion section shell;Preparation of three-dimensional four-way woven, chemical vapor deposition, resin impregnation, carbonization densification, high temperature graphitization and coating treatment throat lining;Short cut high silica fiber heat insulation layer is formed by molding;The expansion section heat insulation layer is prepared by using carbon layer and high silica layer composite winding;Finally, each part is assembled by embedding plug-in and adhesive joint, and a thermal expansion gap is reserved between the throat lining and the heat insulation layer.The application is designed by material-structure-process integration, which eliminates the thermal mismatch risk of traditional multi-component interface, significantly improves the ablation resistance and long-term working reliability of the nozzle.

Description

Technical Field

[0001] This invention belongs to the field of solid rocket motor nozzle technology, specifically relating to an ablation-resistant solid rocket motor nozzle and its preparation method. Background Technology

[0002] As a key component for energy conversion in solid rocket engines, the nozzle plays an absolutely crucial role in the overall performance of the solid rocket and its ability to complete its mission. Traditional solid rocket engine nozzles are mainly divided into two parts: a functional layer (converging section liner, throat liner, and dilator liner) and a structural layer (converging section shell and dilator shell). Specifically, the nozzle consists of the convergent section, the dilator section, and the throat liner. The throat liner is generally simply embedded in the front and back liners at the connection with the rear section. The convergent section consists of a metal shell and a convergent section liner, and the dilator section also consists of a metal shell and a dilator section liner. In terms of manufacturing methods, the convergent section is formed through material pretreatment and integral molding; the throat liner is formed using special materials or special alloy steel with precision machining; and the dilator section is formed using molding or winding processes. The nozzle structure is simple, and the material selection is limited.

[0003] In recent years, with the continuous breakthroughs in aerospace technology both domestically and internationally, the structure and technology of nozzles have also been improved and optimized accordingly. As a key component of the nozzle, the preparation methods and materials of the throat liner are also constantly being improved and optimized, and its ablation resistance and erosion resistance are also continuously improving. However, under complex working conditions, the following defects still exist: (1) Traditional nozzles are made by molding each component separately. The throat liner is often simply connected or nested with the backing or front inner liner. The components are joined by adhesive bonding or mechanical connection. There are various material interface matching forms. Due to the difference in materials, the coefficient of thermal expansion and thermal conductivity of each interface are also different. This makes the nozzle prone to thermal expansion mismatch and stress concentration during operation. Under long-term working conditions, the risk of interface debonding and cracking increases.

[0004] (2) Single material solutions are difficult to balance ablation resistance and long-term changes. For nozzles that operate for a long period of time, the insulation layers of the convergence and diffusion sections are prone to burn-through failure under the combined effect of high temperature and particle erosion. Traditional single material insulation layers are difficult to provide reliable thermal protection under long-term operating conditions.

[0005] (3) The nozzle structure is simple and the overall weight is redundant. The existing nozzles are composed of a front section and a rear section, both of which are equipped with metal shells. The overall weight of the nozzle is too heavy, resulting in redundant overall nozzle mass and insufficient local ablation resistance and long-term working capability.

[0006] Therefore, there is an urgent need to develop a new nozzle structure and its fabrication method that can simultaneously meet the requirements of ablation resistance under long-term working conditions, which is of great significance for improving the long-cycle working capability and reliability of solid rocket engines. Summary of the Invention

[0007] The purpose of this invention is to provide an ablation-resistant solid rocket motor nozzle and its manufacturing method. This invention employs an integrated design of materials, structure, and process to create a structure consisting of only four parts: a throat liner, an insulation layer, an expansion section liner, and an expansion section shell. This design meets ablation performance requirements while reducing the insulation layer and shell, decreasing nozzle weight, saving material costs, and achieving high reliability and safety of the nozzle during long-term use.

[0008] The specific implementation process of this invention is as follows: A method for preparing an ablation-resistant solid rocket motor nozzle includes the following steps: (1) According to the structure in the design drawings, the ablation-resistant solid rocket motor nozzle includes a throat liner, a heat insulation layer, an expansion section shell, and an expansion section insulation layer; (2) Machining of the expansion section shell According to the drawings, the front of the expansion section shell is provided with an integrated flange structure, and the expansion section shell is integrally formed using alloy steel through existing machining methods; (3) Processing of throat liner (3.1) Preform preparation Using polyacrylonitrile carbon fiber filaments as raw material, a three-dimensional four-directional weaving process with a ring layout is adopted on the throat liner tooling to obtain a bulk density of 0.7–1.1 g / cm³. 3 Annular throat liner preform; (3.2) Pre-curing of precast structures The prepared throat liner preform is placed in an oven for pre-curing; (3.3) Chemical vapor deposition In a deposition furnace, C3H6 is used as the carbon source gas and N2 is used as the carrier gas to perform pyrolytic carbon deposition on the pre-cured throat liner blank. The deposition process is repeated until the density of the pre-cured throat liner blank reaches 1.30 to 1.60 g / cm³, thus obtaining the throat liner blank. (3.4) Resin impregnation and carbonization densification In an impregnation furnace, the throat liner preform after chemical vapor deposition is impregnated with phenolic resin or furan resin under pressure; the impregnated throat liner preform is then carbonized in a carbonization furnace under N2 protection; the impregnation and carbonization processes are repeated until the density of the throat liner preform reaches 1.80 to 2.05 g / cm³, thus obtaining a denser throat liner preform. (3.5) High-temperature graphitization The densified throat liner blank is placed in a high-temperature graphitization furnace and graphitized under a N2 protective atmosphere. (3.6) Machining According to the drawings, the graphitized throat liner blank is machined on its inner and outer surfaces. The outer surface is machined into a conical surface with a cone angle of 25° to 65°. The machining accuracy is controlled within ±0.10mm. An annular groove for inserting into the front of the expansion section shell is also machined on the throat liner blank, and it is adapted to the front of the expansion section shell. (3.7) Coating SiC powder or Si powder is sprayed onto the inner surface of the processed throat liner using low-pressure plasma spraying. The coating thickness is 20-60 μm, thus obtaining the formed throat liner. (4) Thermal insulation layer processing (4.1) Short high-silica fibers with a length of 25-50 mm, thermosetting phenolic resin and ethanol solvent are mixed evenly at a mass ratio of (40-50):(50-60):(4-15). The mixture is kneaded in a kneader to make the short high-silica fibers and thermosetting phenolic resin evenly mixed. Then it is transferred to a tearing machine for the first tearing to loosen the agglomerated fibers in the mixture. The torn mixture is spread on a screen for drying. After spreading it evenly, the dried mixture is placed in an oven for drying. The dried mixture is then transferred to a tearing machine for the second tearing. After tearing, a premix is ​​obtained. Then it is transferred to an oven for pre-drying to obtain a molding premix. (4.2) Preheat the insulation layer molding mold at 60~80℃ for 30~60min, put the pre-baked molding premix into the insulation layer molding mold, heat it to 85~100℃ at a heating rate of 0.2~0.5℃ / min, apply pressure of 5~10MPa, hold pressure for 30~60min for pre-curing, then heat it to 100~180°C at a heating rate of 0.5~0.7℃ / min, apply pressure of 10~20MPa, hold pressure for 100~150min for curing, cool down and demold to obtain the insulation layer blank, and machine it into an insulation layer according to the dimensions of the drawing; (5) Processing of the insulation layer of the expansion section The expansion section insulation layer consists of an inner carbon layer and an outer high-silica oxygen layer; (5.1) The inner carbon layer is made by wet winding of fibers. According to the size of the insulation layer of the expansion section, starting from the small end of the mold, the carbon fiber filaments impregnated with adhesive are selected and put into the fiber winding machine to perform the first layer of winding in an axial flat winding manner. Then, the second layer of winding is performed in an oblique winding manner. Then, the third layer of winding is performed in a radial annular winding manner. The axial flat winding, oblique winding and radial annular winding operations are repeated until the thickness of the carbon layer reaches 3 to 5 mm to obtain the carbon layer. (5.2) Wrap the outer layer of high silica layer around the carbon layer obtained in step (5.1); select a high silica prepreg tape with a width of 30-60mm and enter the fiber winding machine from the small end of the mold to one-third of the total length of the expansion section insulation layer, and use dense winding; after one-third of the total length of the expansion section insulation layer, use rapid winding; repeat the steps of dense winding and rapid winding until the high silica layer thickness reaches 8-10mm, then cut the tape, the winding ends, and the expansion section insulation layer blank is obtained; (5.3) After the winding is completed, several layers of absorbent felt are wrapped around the outer layer of the expansion section insulation blank in sequence, and then wrapped again with a porous isolation film, absorbent felt and vacuum bag in sequence. (5.4) Curing the wrapped expansion section insulation layer. After curing, demolding the wrapped expansion section insulation layer when it cools to below 50°C. Machining according to the dimensions in the drawing to obtain the expansion section insulation layer. (6) According to the drawings, the front part of the expansion section shell is embedded in the annular groove of the throat liner. The center of the throat liner is the airflow channel. The heat insulation layer fills the gap between the throat liner and the front part of the expansion section shell. The heat insulation layer is connected to the inner wall of the front part of the expansion section shell and is bonded with adhesive. The front part of the expansion section shell is provided with an integrated flange structure for bolting and assembly with the end face of the solid rocket engine combustion chamber. The expansion section heat insulation layer is tightly attached to the inner wall of the long-tailed conical structure of the expansion section shell and is bonded with adhesive. The front end of the expansion section heat insulation layer is bonded to the end face of the heat insulation layer with adhesive. An expansion gap of 0.2-0.3mm is provided between the rear end of the throat liner and the front end of the expansion section heat insulation layer. The expansion section heat insulation layer and the expansion section shell form a gradually expanding long-tailed channel. After assembly and bonding, an ablation-resistant solid rocket engine nozzle is obtained.

[0009] Furthermore, in step (3.1), the polyacrylonitrile carbon fiber filament is T700 grade polyacrylonitrile carbon fiber filament; during the weaving process, the volume fraction of polyacrylonitrile carbon fiber is controlled in the range of 45% to 55%, the weaving angle is controlled in the range of 25° to 40°, and the height of the knot is controlled in the range of 10 to 35 mm. In step (3.2), the pre-curing process involves raising the oven temperature from room temperature to 110-150°C at a rate of 1-3°C / min and holding it at that temperature for 1-3 hours; then raising the temperature to 220-250°C at a rate of 2-4°C / min and holding it at that temperature for 2-4 hours to complete the pre-curing. After the throat liner preform cools to below 70°C, the throat liner preform is removed to obtain the pre-cured throat liner blank.

[0010] Furthermore, in step (3.3), the flow rate ratio of C3H6 to N2 is (70~100):(1~5), the deposition temperature is 800~1200℃, the furnace pressure is 1.0~5.0 kPa, the deposition time is 100~300h, and the deposition process is repeated 2~3 times.

[0011] Furthermore, in step (3.4), the pressure impregnation process involves impregnating under a vacuum of ≤120 Pa for 2–5 hours, followed by pressurization to 0.8–1.2 MPa and impregnation for 2–4 hours; during the carbonization process, the temperature is increased to 900–1000 ℃ at a heating rate of 2–5 ℃ / min for carbonization, and the carbonization time is 2–4 hours; the impregnation and carbonization processes are repeated 2–6 times. In step (3.5), during the graphitization process, the high-temperature graphitization furnace is heated to 2300-2600 ℃ at a heating rate of 5-20 ℃ / min, and held at that temperature for 2-5 h to carry out graphitization; In step (3.7), the spraying pressure is 300-800 Pa, the gas flow rate is controlled at 30-60 L / min, and the spraying distance is 50-200 mm.

[0012] Furthermore, in step (4.1), the mixing process is carried out in a mixing tank; the kneading speed is 20-50 rpm, and the kneading time is 30-120 min; the drying time is 12-48 hours, and the spreading thickness does not exceed 10 cm; the drying temperature is 60-100℃, and the drying time is 30-150 min; the speed of the tearing machine is 10-50 rpm during the first and second tearing processes; the pre-drying temperature in the oven is 70-80℃, and the pre-drying time is 60-120 min.

[0013] Further, in step (5.1), the carbon fiber filament is a 1K carbon fiber filament; the temperature of the adhesive used to impregnate the carbon fiber filament is controlled at 30-60℃, the winding speed is controlled at 1-3m / s, and the tension of the carbon fiber filament during the winding process is controlled at 5-20N; the temperature of the adhesive tank of the fiber winding machine is set to 30-60℃; the number of times the axial flat winding, oblique winding and radial annular winding operations are repeated is 3-5 times.

[0014] Further, in step (5.2), the high-silica prepreg tape is a high-silica tape impregnated with adhesive; the axial speed is controlled at 0.16~0.3mm / r during the tight winding process and at 0.3~0.7mm / r during the rapid winding process; the width of the high-silica prepreg tape is 30~60mm; during the tight winding process, the overlap width of the high-silica prepreg tape is 25~55mm, and the tension of the high-silica prepreg tape is controlled at 200~500N during the tight winding process; during the rapid winding process, the overlap width of the high-silica prepreg tape is 10~30mm, and the tension of the high-silica prepreg tape is controlled at 300~500N during the rapid winding process.

[0015] Furthermore, in step (5.3), the pore size of the porous isolation membrane is 20–50 μm.

[0016] Furthermore, in step (5.4), the specific curing process of the wrapped expansion section insulation layer is as follows: (1) Start the heating program of the vacuum tank, raise the temperature from room temperature to 70-90℃ at a rate of 0.3-1.8℃ / min, hold for 1-3 hours, start the initial pressure of 0.5-1.5MPa at 50-70℃ at a rate of 0.01-0.06MPa / min, and after the holding period, raise the pressure to 2-3.5MPa and hold for 1-3 hours at a rate of 0.01-0.04MPa / min; (2) Heat to 100-130℃ and hold for 1-4 hours at a rate of 0.2-0.8℃ / min; (3) Heat to 160-180℃ and keep warm for 2-4 hours. The heating rate is 0.5-0.8℃ / min.

[0017] An ablation-resistant solid rocket motor nozzle includes a throat liner, a heat insulation layer, an expansion section shell, and an expansion section insulation layer. The expansion section shell has a long-tailed conical structure. The rear of the throat liner has an annular groove. The front of the expansion section shell is embedded in the annular groove of the throat liner. The center of the throat liner is a gas flow channel. The heat insulation layer fills the gap between the throat liner and the front of the expansion section shell. The heat insulation layer is connected to the inner wall of the front of the expansion section shell. The front of the expansion section shell has an integrated flange structure for... The solid rocket motor combustion chamber end face is bolted together; the expansion section insulation layer consists of an inner carbon layer and an outer high-silica layer, which are tightly attached to the inner wall of the long-tailed conical structure of the expansion section shell. The front end of the expansion section insulation layer is bonded to the end face of the insulation layer with adhesive, and a 0.2-0.3 mm expansion gap is provided between the rear end of the throat liner and the front end of the expansion section insulation layer. The expansion section insulation layer and the expansion section shell form a gradually expanding long-tailed channel, constituting the inner wall protective layer of the gas expansion acceleration channel.

[0018] The positive effects of this invention: (1) The present invention adopts an embedded nozzle structure and a throat-covered throat liner, abandoning the nozzle convergent section structure, improving the overall ablation resistance and erosion resistance of the nozzle, increasing the service life of the nozzle, reducing the overall weight of the nozzle, reducing the raw material cost of nozzle manufacturing, and improving the overall safety and reliability of solid rocket engine.

[0019] (2) The throat liner of the present invention adopts a three-dimensional four-way woven structure of polyacrylonitrile carbon fiber, combined with deposition and resin impregnation-carbonization cycle densification, the throat liner density reaches 1.80-2.05 g / cm³, and after high temperature graphitization treatment at 2300-2600℃, the crystal structure is complete and the throat liner line ablation rate is ≤0.15 mm / s; the inner surface of the throat liner adopts a SiC or Si coating structure, utilizing the excellent anti-oxidation and anti-erosion properties of SiC or Si, which not only significantly improves the ablation resistance and anti-oxidation properties of the throat liner surface, but also extends the service life of the nozzle throat liner and increases the reliability of long-term use of the nozzle.

[0020] (3) The insulation layer of the nozzle expansion section of the present invention adopts a structure of fiber filament winding + cloth tape winding, which reduces the difficulty in controlling tension, slow climbing speed and large amount of cloth tape waste when pure cloth tape winding, and reduces the nozzle preparation cycle and raw material cost. Attached Figure Description

[0021] Figure 1 This is a schematic cross-sectional view of the ablation-resistant solid rocket motor nozzle of the present invention; in the figure, 1 is the throat liner, 2 is the expansion section shell, 3 is the heat insulation layer, 4 is the expansion section insulation layer, 41 is the high silica layer, 42 is the carbon layer, 5 is the integrated flange, and 6 is the expansion gap. Figure 2 A schematic cross-sectional view of the throat liner tooling; Figure 3 A partial cross-sectional view of the mold for forming the insulation layer after filling with premixed material; in the figure, 1 is the upper mold, 2 is the lower mold, 3 is the top plate, and 4 is the premixed material being filled. Figure 4 This is a cross-sectional structural diagram of the insulation layer forming mold; in the diagram, 1 is the upper mold, 2 is the lower mold, 3 is the top plate, 5 is the premix filling cavity, 6 is the boss, and 7 is the temperature measuring hole. Figure 5 This is a schematic diagram of the cross-sectional structure of the mold for the expansion section insulation layer; in the diagram, 1 is the nut, 2 is the winding baffle, and 3 is the winding core mold; Figure 6 A schematic diagram of the cross-sectional structure of the core mold for the expansion section insulation layer. Detailed Implementation

[0022] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0024] The ablation-resistant solid rocket motor nozzle of this invention is an embedded nozzle structure, which reduces the convergence section structure of traditional nozzles.

[0025] On one hand, the ablation-resistant solid rocket motor nozzle provided by this invention adopts an embedded structural design, integrating four parts: throat liner, heat insulation layer, expansion section shell, and expansion section insulation layer. This eliminates the traditional convergent section shell structure, thus reducing overall weight. The integrated flange structure at the front of the expansion section shell connects to the combustion chamber, and the expansion section adopts a long-tail structure. Finally, all components are connected by adhesive bonding to assemble into a molded product. The method of this invention constructs a ring-shaped throat liner preform using polyacrylonitrile carbon fiber filaments through three-dimensional four-directional weaving. Combined with chemical vapor deposition, resin impregnation-carbonization cycle densification, and high-temperature graphitization treatment, the throat liner matrix becomes dense and has a complete lattice structure, thereby obtaining a high-density, high-strength carbon / carbon composite matrix. Based on this, plasma spraying of SiC or Si coatings on the inner surface of the throat liner utilizes the excellent oxidation and erosion resistance properties of SiC or Si materials to effectively block the direct erosion of the matrix by high-temperature combustion gases. Meanwhile, the heat insulation layer is molded from short-cut high-silica fibers and phenolic resin, filling the gap between the throat liner and the expansion section shell, blocking the heat transfer path to the metal shell. The expansion section insulation layer adopts a composite structure of wet-wound inner carbon fiber layer and segmented-wound outer high-silica layer. The inner layer provides structural support, and the outer layer provides high thermal resistance protection, forming a gradient thermal protection system together. The components are assembled as a whole through embedded mechanical fit and multi-point adhesive bonding, and thermal expansion gaps are reserved at key interfaces, thereby effectively alleviating the thermal stress caused by the difference in thermal expansion coefficients between different materials. Therefore, this invention effectively solves the technical problem that traditional split nozzle structures are prone to stress concentration due to the mismatch of thermal expansion coefficients at the interfaces of multiple materials under long-cycle operating conditions, leading to interface debonding, cracking, or even burn-through failure, making it difficult to balance high ablation resistance and long-cycle structural reliability. It avoids nozzle function loss due to interface failure during long-cycle operation, significantly improving the safety and service life of solid rocket engines under complex operating conditions.

[0026] On the other hand, the preparation method provided by this invention includes the following steps: processing an expansion section shell with an integrated flange structure; preparing a throat liner treated with three-dimensional four-way weaving, chemical vapor deposition, resin impregnation and carbonization densification, high-temperature graphitization, and coating; molding a short-cut high-silica fiber insulation layer; preparing an expansion section insulation layer by composite winding of a carbon layer and a high-silica layer; and finally assembling the components by embedded insertion and adhesive bonding, with a thermal expansion gap reserved between the throat liner and the insulation layer. This application, through integrated material-structure-process design, eliminates the risk of thermal mismatch at the interfaces of traditional multi-component systems, significantly improving the nozzle's ablation resistance and long-term operational reliability.

[0027] Example 1 An ablation-resistant solid rocket motor nozzle, see Figure 1 The system includes a throat liner, a heat insulation layer, an expansion section shell, and an expansion section insulation layer. The expansion section shell has a long-tailed conical structure. The rear of the throat liner has an annular groove, and the front of the expansion section shell is embedded in the annular groove of the throat liner. The center of the throat liner is an airflow channel. The heat insulation layer has an annular structure and fills the gap between the throat liner and the front of the expansion section shell. The heat insulation layer is connected to the inner wall of the front of the expansion section shell. The front of the expansion section shell has an integrated flange structure for fastening. The combustion chamber end face of the rocket engine is bolted together; the expansion section insulation layer consists of an inner carbon layer and an outer high-silica layer. The expansion section insulation layer is tightly attached to the inner wall of the long-tailed conical structure of the expansion section shell. The front end of the expansion section insulation layer is bonded to the end face of the insulation layer with adhesive. The rear end of the throat liner and the front end of the expansion section insulation layer are provided with an expansion gap of 0.2 to 0.3 mm. The expansion section insulation layer and the expansion section shell form a gradually expanding long-tailed channel, which constitutes the inner wall protective layer of the gas expansion acceleration channel.

[0028] Example 2 The solid rocket motor in this embodiment has a nozzle throat diameter of φ45mm, an expansion ratio of 9:1, and a designed operating time of 20s.

[0029] The method for preparing the ablation-resistant solid rocket motor nozzle described in this embodiment includes the following steps: (1) According to the structure in the design drawings of Example 1, the ablation-resistant solid rocket motor nozzle includes a throat liner, a heat insulation layer, an expansion section shell and an expansion section heat insulation layer, and adopts an embedded nozzle structure; (2) Machining of the expansion section shell According to the drawings, the expansion section shell is an integral rotating structure. The front of the expansion section shell is provided with an integral flange structure. The expansion section shell is integrally formed using alloy steel through existing machining methods. Specifically, GH4169 high-temperature alloy forgings are selected, solution treated at 980 ℃ for 1 h, then cooled in air and aged at 720 ℃ for 8 h, furnace cooled to 620 ℃ and held for 8 h, then cooled in air, and then integrally formed using a five-axis CNC lathe. The shell wall thickness is 4 mm, and the machining accuracy of the inner wall surface is controlled within ±0.05 mm.

[0030] (3) Processing of throat liner (3.1) Preform preparation Using T700 grade polyacrylonitrile carbon fiber as raw material, a three-dimensional four-way weaving is carried out on the throat liner tooling using a ring layout. During the weaving process, the volume fraction of polyacrylonitrile carbon fiber is controlled at 48%, the weaving angle is controlled at 28°, and the knot height is controlled at 20mm, resulting in a ring-shaped throat liner preform with a bulk density of 0.9g / cm³.

[0031] (3.2) Pre-curing of precast structures The prepared throat liner preform was placed in an oven and heated from room temperature to 130°C at a rate of 2°C / min, and held for 2 hours; then heated to 235°C at a rate of 3°C / min, and held for 3 hours; after cooling to below 60°C, it was removed to obtain the pre-cured throat liner blank.

[0032] (3.3) Chemical vapor deposition (CVI) In a deposition furnace, C3H6 is used as the carbon source gas and N2 is used as the carrier gas. The flow ratio of C3H6 to N2 is 85:3. The deposition temperature is 1000°C, the furnace pressure is 3.0 kPa, and the deposition time is 200 h. The deposition process is repeated twice until the density of the pre-cured throat liner blank reaches 1.45 g / cm³, thus obtaining the throat liner blank.

[0033] (3.4) Resin impregnation and carbonization densification In an impregnation furnace, the throat liner preform after chemical vapor deposition is immersed in phenolic resin and impregnated under vacuum of 100 Pa for 3 hours, then pressurized to 1.0 MPa and impregnated for another 3 hours. The impregnated throat liner preform is then carbonized in a carbonization furnace under N2 protection at a heating rate of 3°C / min to 950°C for 3 hours. The impregnation and carbonization process is repeated 4 times until the density of the throat liner preform reaches 1.95 g / cm³, thus obtaining a denser throat liner preform.

[0034] (3.5) High-temperature graphitization The densified throat liner blank was placed in a high-temperature graphitization furnace and heated to 2450°C at a heating rate of 10°C / min under a N2 protective atmosphere for 3 hours for graphitization.

[0035] (3.6) Machining According to the drawings, the graphitized throat liner blank is machined on its inner and outer surfaces. The outer surface is machined into a conical surface with a 50° cone angle. The machining accuracy is controlled within ±0.10mm. An annular groove for inserting into the front of the expansion section shell is also machined on the throat liner blank, which is adapted to the front of the expansion section shell.

[0036] (3.7) SiC coating: SiC powder is sprayed on the inner surface of the throat liner after processing. Low-pressure spraying is carried out by plasma spraying. The spraying pressure is 500Pa, the gas flow rate is controlled at 45L / min, the spraying distance is 120mm, and the coating thickness is 40μm, thus obtaining the formed throat liner.

[0037] (4) Insulation layer processing: (4.1) Short high silica fiber with a length of 36 mm, thermosetting phenolic resin and ethanol solvent are mixed evenly at a mass ratio of 45:55:10. The mixture is kneaded in a mixing tank at a speed of 35 r / min for 60 min. Then it is transferred to a tearing machine at a speed of 30 r / min for the first tearing. The torn mixture is spread on a screen and left to dry for 24 hours with a thickness of 8 cm. The dried mixture is placed in an 80°C oven and dried for 90 min. The dried mixture is then transferred to a tearing machine at a speed of 30 r / min for the second tearing. After tearing, a premix is ​​obtained. Then it is pre-dried in a 75°C oven for 100 min to obtain a molding premix.

[0038] (4.2) Preheat the insulation layer molding mold at 70°C for 45 min, put the pre-baked molding premix into the insulation layer molding mold, heat it to 92°C at a heating rate of 0.4°C / min, apply pressure of 8MPa, and hold pressure for 45 min for pre-curing; then heat it to 170°C at a heating rate of 0.6°C / min, apply pressure of 15MPa, and hold pressure for 120 min for curing and molding, cool down and demold to obtain the insulation layer blank, and machine it into an insulation layer according to the dimensions of the drawing, and match the dimensions of the annular groove of the throat liner and the front of the expansion section shell to achieve assembly.

[0039] (5) Processing of the insulation layer of the expansion section The expansion section insulation layer consists of an inner carbon layer and an outer high-silica oxygen layer; (5.1) The inner carbon layer is made by wet winding of fibers. According to the size of the insulation layer of the expansion section, 1K carbon fiber filaments impregnated with adhesive are selected from the small end of the mold and enter the fiber winding machine. The adhesive temperature is controlled at 45°C, the winding speed is controlled at 2m / s, and the fiber tension is controlled at 12N. The adhesive tank temperature of the fiber winding machine is set to 45°C. The first layer is wound in an axial flat winding manner, then the second layer is wound in an oblique winding manner, and then the third layer is wound in a radial annular winding manner. The above winding operation is repeated 4 times until the thickness of the carbon layer reaches 4 mm to obtain the carbon layer.

[0040] (5.2) The high-silica layer is wound around the outer layer of the carbon layer obtained in step (5.1); a 55mm wide high-silica prepreg tape is selected and fed into the fiber winding machine from the small end of the mold to one-third of the total length of the expansion section insulation layer. Dense winding is used, with the axial speed controlled at 0.25mm / r, the tape overlap width at 40mm, and the tension controlled at 350N. From one-third of the total length of the expansion section insulation layer onwards, rapid winding is used, with the axial speed controlled at 0.5mm / r, the tape overlap width at 20mm, and the tension controlled at 400N. The dense winding and rapid winding steps are repeated until the high-silica layer thickness reaches 9mm. The tape is then cut, and the winding is complete, yielding the expansion section insulation layer blank. The high-silica prepreg tape is a high-silica tape impregnated with adhesive.

[0041] (5.3) After the winding is completed, several layers of absorbent felt are wrapped around the outer layer of the expansion section insulation blank in sequence, and then wrapped again with a porous isolation membrane with a pore size of 30μm, absorbent felt and vacuum bag in sequence.

[0042] (5.4) The encapsulated expansion section insulation layer is cured. The specific process is as follows: the heating program of the vacuum tank is turned on, and the temperature is increased from room temperature to 80°C at a heating rate of 0.6°C / min, and held for 2 hours. At 60°C, the initial pressure is increased to 1.0 MPa at a pressure increase rate of 0.03 MPa / min. After the initial pressure increase, the pressure is increased to 3.0 MPa at a pressure increase rate of 0.02 MPa / min and held for 2 hours. Then, the temperature is increased to 120°C at a heating rate of 0.5°C / min and held for 2 hours. Finally, the temperature is increased to 170°C at a heating rate of 0.6°C / min and held for 3 hours. After the curing is completed, when the encapsulated expansion section insulation layer cools to below 50°C, it is removed from the furnace and demolded. According to the dimensions in the drawing, it is machined to obtain the expansion section insulation layer, the dimensions of which are adapted to the expansion section shell.

[0043] (6) Assembly According to the drawings, the throat liner has an annular groove at its rear. The front part of the expansion section shell is embedded in the annular groove of the throat liner. The center of the throat liner is an airflow channel. The heat insulation layer fills the gap between the throat liner and the front part of the expansion section shell. The heat insulation layer is bonded to the inner wall of the front part of the expansion section shell with adhesive. The expansion section insulation layer is tightly attached to the inner wall of the long-tailed conical structure of the expansion section shell and is bonded with adhesive. The front end of the expansion section insulation layer is bonded to the end face of the heat insulation layer with adhesive. A 0.3 mm expansion gap is provided between the rear end of the throat liner and the front end of the expansion section insulation layer. After assembly and bonding, an ablation-resistant solid rocket motor nozzle is obtained.

[0044] The throat liner prepared in this embodiment has a density of 1.95 g / cm³, a SiC coating thickness of 40 μm, and a carbon layer thickness of 4 mm for the expansion section insulation layer.

[0045] Example 3 The solid rocket motor in this embodiment has a nozzle throat diameter of φ45mm, an expansion ratio of 9:1, and a designed operating time of 20s.

[0046] The method for preparing the ablation-resistant solid rocket motor nozzle described in this embodiment includes the following steps: (1) According to the structure in the design drawings of Example 1, the ablation-resistant solid rocket motor nozzle includes a throat liner, a heat insulation layer, an expansion section shell and an expansion section heat insulation layer, and adopts an embedded nozzle structure; (2) Machining of the expansion section shell According to the drawings, the expansion section shell is an integral rotating structure. The front of the expansion section shell is provided with an integral flange structure. The expansion section shell is integrally formed using alloy steel through existing machining methods. Specifically, GH4169 high-temperature alloy forgings are selected, solution treated at 980 ℃ for 1 h, then cooled in air and aged at 720 ℃ for 8 h, furnace cooled to 620 ℃ and held for 8 h, then cooled in air, and then integrally formed using a five-axis CNC lathe. The shell wall thickness is 4 mm, and the machining accuracy of the inner wall surface is controlled within ±0.05 mm.

[0047] (3) Processing of throat liner (3.1) Preform preparation Using T700 grade polyacrylonitrile carbon fiber as raw material, a three-dimensional four-way weaving is carried out on the throat liner tooling using a ring layout. During the weaving process, the volume fraction of polyacrylonitrile carbon fiber is controlled at 45%, the weaving angle is controlled at 25°, and the knot height is controlled at 10mm, resulting in a ring-shaped throat liner preform with a bulk density of 0.7g / cm³.

[0048] (3.2) Pre-curing of precast structures The prepared throat liner preform was placed in an oven and heated from room temperature to 110°C at a rate of 1°C / min, and held for 3 hours; then heated to 220°C at a rate of 2°C / min, and held for 4 hours; after cooling to below 50°C, it was removed to obtain the pre-cured throat liner blank.

[0049] (3.3) Chemical vapor deposition (CVI) In a deposition furnace, C3H6 is used as the carbon source gas and N2 is used as the carrier gas. The flow ratio of C3H6 to N2 is 70:1. The deposition temperature is 800°C, the furnace pressure is 1.0 kPa, the deposition time is 300 h, and the deposition process is repeated 3 times until the density of the pre-cured throat liner blank reaches 1.3 g / cm³, thus obtaining the throat liner blank.

[0050] (3.4) Resin impregnation and carbonization densification In an impregnation furnace, the throat liner preform after chemical vapor deposition is immersed in phenolic resin and impregnated under vacuum of 110 Pa for 5 hours, then pressurized to 0.8 MPa and impregnated for 4 hours. The impregnated throat liner preform is then carbonized in a carbonization furnace under N2 protection at a heating rate of 2°C / min to 900°C for 4 hours. The impregnation and carbonization processes are repeated twice until the density of the throat liner preform reaches 1.8 g / cm³, thus obtaining a denser throat liner preform.

[0051] (3.5) High-temperature graphitization The densified throat liner blank was placed in a high-temperature graphitization furnace and heated to 2300°C at a heating rate of 5°C / min under a N2 protective atmosphere for 2 hours for graphitization.

[0052] (3.6) Machining According to the drawings, the graphitized throat liner blank is machined on its inner and outer surfaces. The outer surface is machined into a conical surface with a 25° cone angle, and the machining accuracy is controlled within ±0.10mm. An annular groove for inserting into the front of the expansion section shell is also machined on the throat liner blank, and it is adapted to the front of the expansion section shell.

[0053] (3.7) Si coating: Si powder is sprayed on the inner surface of the throat liner after processing. Low-pressure spraying is performed by plasma spraying. The spraying pressure is 300 Pa, the gas flow rate is controlled at 30 L / min, the spraying distance is 120 mm, and the coating thickness is 50 μm, thus obtaining the formed throat liner.

[0054] (4) Insulation layer processing: (4.1) Short high silica fiber with a length of 25 mm, thermosetting phenolic resin and ethanol solvent are mixed evenly at a mass ratio of 40:50:4. The mixture is kneaded in a mixing tank at a speed of 20 r / min for 30 min. Then it is transferred to a tearing machine at a speed of 20 r / min for the first tearing. The torn mixture is spread on a screen and left to dry for 12 hours with a thickness of 4 cm. The dried mixture is placed in a 60°C oven and dried for 30 min. The dried mixture is then transferred to a tearing machine at a speed of 10 r / min for the second tearing. After tearing, a premix is ​​obtained. Then it is transferred to a 70°C oven for pre-drying for 60 min to obtain a molding premix.

[0055] (4.2) Preheat the insulation layer molding mold at 60°C for 60 min, put the pre-baked molding premix into the insulation layer molding mold, heat it to 85°C at a heating rate of 0.2°C / min, apply pressure of 5MPa, and hold pressure for 30 min for pre-curing; then heat it to 100°C at a heating rate of 0.5°C / min, apply pressure of 10MPa, and hold pressure for 100 min for curing and molding, cool down and demold to obtain the insulation layer blank, and machine it into an insulation layer according to the dimensions of the drawing, and match the dimensions of the annular groove of the throat liner and the front of the expansion section shell to achieve assembly.

[0056] (5) Processing of the insulation layer of the expansion section The expansion section insulation layer consists of an inner carbon layer and an outer high-silica oxygen layer; (5.1) The inner carbon layer is made by wet winding of fibers. According to the size of the insulation layer of the expansion section, 1K carbon fiber filaments impregnated with adhesive are selected from the small end of the mold and enter the fiber winding machine. The adhesive temperature is controlled at 30°C, the winding speed is controlled at 1m / s, and the fiber tension is controlled at 5N. The adhesive tank temperature of the fiber winding machine is set to 30°C. The first layer is wound in an axial flat winding manner, then the second layer is wound in an oblique winding manner, and then the third layer is wound in a radial annular winding manner. The above winding operation is repeated 3 times until the thickness of the carbon layer reaches 3 mm to obtain the carbon layer.

[0057] (5.2) The high-silica layer is wound around the outer layer of the carbon layer obtained in step (5.1); a 30mm wide high-silica prepreg tape is selected and fed into the fiber winding machine from the small end of the mold to one-third of the total length of the expansion section insulation layer. Dense winding is used, with the axial speed controlled at 0.16mm / r, the tape overlap width at 25mm, and the tension controlled at 200N. From one-third of the total length of the expansion section insulation layer onwards, rapid winding is used, with the axial speed controlled at 0.3mm / r, the tape overlap width at 10mm, and the tension controlled at 300N. The dense winding and rapid winding steps are repeated until the high-silica layer thickness reaches 8mm. The tape is then cut, and the winding is complete, yielding the expansion section insulation layer blank. The high-silica prepreg tape is a high-silica tape impregnated with adhesive.

[0058] (5.3) After the winding is completed, several layers of absorbent felt are wrapped around the outer layer of the expansion section insulation blank in sequence, and then wrapped again with a porous isolation membrane with a pore size of 20μm, absorbent felt and vacuum bag in sequence.

[0059] (5.4) The encapsulated expansion section insulation layer is cured. The specific process is as follows: the heating program of the vacuum tank is turned on, and the temperature is increased from room temperature to 70°C at a heating rate of 0.3°C / min, and held for 3 hours. At 50°C, the initial pressure is increased to 0.5MPa at a pressure increase rate of 0.01MPa / min. After the initial pressure increase, the pressure is increased to 2MPa at a pressure increase rate of 0.01MPa / min and held for 1 hour. Then, the temperature is increased to 100°C at a heating rate of 0.2°C / min and held for 4 hours. Finally, the temperature is increased to 160°C at a heating rate of 0.5°C / min and held for 4 hours. After the curing is completed, when the encapsulated expansion section insulation layer cools to below 50°C, it is removed from the furnace and demolded. According to the dimensions in the drawing, it is machined to obtain the expansion section insulation layer, the dimensions of which are adapted to the expansion section shell.

[0060] (6) Assembly According to the drawings, the throat liner has an annular groove at its rear. The front part of the expansion section shell is embedded in the annular groove of the throat liner. The center of the throat liner is an airflow channel. The heat insulation layer fills the gap between the throat liner and the front part of the expansion section shell. The heat insulation layer is bonded to the inner wall of the front part of the expansion section shell with adhesive. The expansion section insulation layer is tightly attached to the inner wall of the long-tailed conical structure of the expansion section shell and is bonded with adhesive. The front end of the expansion section insulation layer is bonded to the end face of the heat insulation layer with adhesive. A 0.3 mm expansion gap is provided between the rear end of the throat liner and the front end of the expansion section insulation layer. After assembly and bonding, an ablation-resistant solid rocket motor nozzle is obtained.

[0061] The throat liner prepared in this embodiment has a density of 1.8 g / cm³, a Si coating thickness of 50 μm, and a carbon layer thickness of 3 mm for the expansion section insulation layer. It still achieves the technical effects of the present invention, thus proving that within the above parameter range, the technical solution of the present invention has good feasibility and stability.

[0062] Example 4 The solid rocket motor in this embodiment has a nozzle throat diameter of φ45mm, an expansion ratio of 9:1, and a designed operating time of 20s.

[0063] The method for preparing the ablation-resistant solid rocket motor nozzle described in this embodiment includes the following steps: (1) According to the structure in the design drawings of Example 1, the ablation-resistant solid rocket motor nozzle includes a throat liner, a heat insulation layer, an expansion section shell and an expansion section heat insulation layer, and adopts an embedded nozzle structure; (2) Machining of the expansion section shell According to the drawings, the expansion section shell is an integral rotating structure. The front of the expansion section shell is provided with an integral flange structure. The expansion section shell is integrally formed using alloy steel through existing machining methods. Specifically, GH4169 high-temperature alloy forgings are selected, solution treated at 980 ℃ for 1 h, then cooled in air and aged at 720 ℃ for 8 h, furnace cooled to 620 ℃ and held for 8 h, then cooled in air, and then integrally formed using a five-axis CNC lathe. The shell wall thickness is 4 mm, and the machining accuracy of the inner wall surface is controlled within ±0.05 mm.

[0064] (3) Processing of throat liner (3.1) Preform preparation Using T700 grade polyacrylonitrile carbon fiber as raw material, a three-dimensional four-way weaving is carried out on the throat liner tooling using a ring layout. During the weaving process, the volume fraction of polyacrylonitrile carbon fiber is controlled at 55%, the weaving angle is controlled at 40°, and the knot height is controlled at 35mm, resulting in a ring-shaped throat liner preform with a bulk density of 1.1g / cm³.

[0065] (3.2) Pre-curing of precast structures The prepared throat liner preform was placed in an oven and heated from room temperature to 150°C at a rate of 3°C / min, and held for 1 hour; then heated to 250°C at a rate of 4°C / min, and held for 2 hours; after cooling to below 70°C, it was removed to obtain the pre-cured throat liner blank.

[0066] (3.3) Chemical vapor deposition (CVI) In a deposition furnace, C3H6 is used as the carbon source gas and N2 is used as the carrier gas. The flow ratio of C3H6 to N2 is 100:5. The deposition temperature is 1200°C, the furnace pressure is 5.0 kPa, and the deposition time is 100 h. The deposition process is repeated 3 times until the density of the pre-cured throat liner blank reaches 1.6 g / cm³, thus obtaining the throat liner blank.

[0067] (3.4) Resin impregnation and carbonization densification In an impregnation furnace, the throat liner preform after chemical vapor deposition was immersed in furan resin and impregnated under vacuum of 120 Pa for 2 hours, then pressurized to 1.2 MPa and impregnated for another 2 hours. The impregnated throat liner preform was then carbonized in a carbonization furnace under N2 protection at a heating rate of 5°C / min to 1000°C for 2 hours. The impregnation and carbonization process was repeated 6 times until the density of the throat liner preform reached 2.05 g / cm³, thus obtaining a denser throat liner preform.

[0068] (3.5) High-temperature graphitization The densified throat liner blank was placed in a high-temperature graphitization furnace and heated to 2600°C at a heating rate of 20°C / min under a N2 protective atmosphere for 5 hours for graphitization.

[0069] (3.6) Machining According to the drawings, the graphitized throat liner blank is machined on its inner and outer surfaces. The outer surface is machined into a conical surface with a 65° cone angle, and the machining accuracy is controlled within ±0.10mm. An annular groove for inserting into the front of the expansion section shell is also machined on the throat liner blank, and it is adapted to the front of the expansion section shell.

[0070] (3.7) SiC coating: SiC powder is sprayed on the inner surface of the throat liner after processing. Low-pressure spraying is performed by plasma spraying. The spraying pressure is 800Pa, the gas flow rate is controlled at 60L / min, the spraying distance is 200mm, and the coating thickness is 60μm, thus obtaining the formed throat liner.

[0071] (4) Insulation layer processing: (4.1) Short high silica fibers with a length of 50 mm, thermosetting phenolic resin and ethanol solvent are mixed evenly at a mass ratio of 50:60:15. The mixture is kneaded in a mixing tank at a speed of 50 r / min for 120 min. Then it is transferred to a tearing machine at a speed of 50 r / min for the first tearing. The torn mixture is spread on a screen and left to dry for 48 hours with a thickness of 5 cm. The dried mixture is placed in a 100°C oven and dried for 150 min. The dried mixture is then transferred to a tearing machine at a speed of 50 r / min for the second tearing. After tearing, a premix is ​​obtained. Then it is transferred to an 80°C oven for pre-drying for 120 min to obtain a molding premix.

[0072] (4.2) Preheat the insulation layer molding mold at 80°C for 30 min, put the pre-baked molding premix into the insulation layer molding mold, heat it to 100°C at a heating rate of 0.5°C / min, apply pressure of 10MPa, and hold pressure for 60 min for pre-curing; then heat it to 180°C at a heating rate of 0.7°C / min, apply pressure of 20MPa, and hold pressure for 150 min for curing and molding, cool down and demold to obtain the insulation layer blank, and machine it into an insulation layer according to the dimensions of the drawing, and match the dimensions of the annular groove of the throat liner and the front of the expansion section shell to achieve assembly.

[0073] (5) Processing of the insulation layer of the expansion section The expansion section insulation layer consists of an inner carbon layer and an outer high-silica oxygen layer; (5.1) The inner carbon layer is made by wet winding of fibers. According to the size of the insulation layer of the expansion section, 1K carbon fiber filaments impregnated with adhesive are selected from the small end of the mold and enter the fiber winding machine. The adhesive temperature is controlled at 60°C, the winding speed is controlled at 3m / s, and the fiber tension is controlled at 20N. The adhesive tank temperature of the fiber winding machine is set to 60°C. The first layer is wound in an axial flat winding manner, then the second layer is wound in an oblique winding manner, and then the third layer is wound in a radial annular winding manner. The above winding operation is repeated 5 times until the thickness of the carbon layer reaches 5 mm to obtain the carbon layer.

[0074] (5.2) The high-silica layer is wound around the outer layer of the carbon layer obtained in step (5.1); a 60mm wide high-silica prepreg tape is selected and fed into the fiber winding machine from the small end of the mold to one-third of the total length of the expansion section insulation layer. Dense winding is used, with the axial speed controlled at 0.3mm / r, the tape overlap width at 55mm, and the tension controlled at 500N. From one-third of the total length of the expansion section insulation layer onwards, rapid winding is used, with the axial speed controlled at 0.7mm / r, the tape overlap width at 30mm, and the tension controlled at 500N. The dense winding and rapid winding steps are repeated until the high-silica layer thickness reaches 10mm. The tape is then cut, and the winding is complete, yielding the expansion section insulation layer blank. The high-silica prepreg tape is a high-silica tape impregnated with adhesive.

[0075] (5.3) After the winding is completed, several layers of absorbent felt are wrapped around the outer layer of the expansion section insulation blank in sequence, and then wrapped again with a porous isolation membrane with a pore size of 50μm, absorbent felt and vacuum bag in sequence.

[0076] (5.4) The encapsulated expansion section insulation layer is cured. The specific process is as follows: the heating program of the vacuum tank is turned on, and the temperature is increased from room temperature to 90°C at a heating rate of 1.8°C / min, and held for 1 hour. At 70°C, the initial pressure is increased to 1.5MPa at a pressure increase rate of 0.06MPa / min. After the initial pressure increase, the pressure is increased to 3.5MPa at a pressure increase rate of 0.04MPa / min and held for 3 hours. Then, the temperature is increased to 130°C at a heating rate of 0.8°C / min and held for 1 hour. Finally, the temperature is increased to 180°C at a heating rate of 0.8°C / min and held for 2 hours. After the curing is completed, when the encapsulated expansion section insulation layer cools to below 40°C, it is removed from the furnace and demolded. According to the dimensions in the drawing, it is machined to obtain the expansion section insulation layer, the dimensions of which are adapted to the expansion section shell.

[0077] (6) Assembly According to the drawings, the throat liner has an annular groove at its rear. The front part of the expansion section shell is embedded in the annular groove of the throat liner. The center of the throat liner is an airflow channel. The heat insulation layer fills the gap between the throat liner and the front part of the expansion section shell. The heat insulation layer is bonded to the inner wall of the front part of the expansion section shell with adhesive. The expansion section insulation layer is tightly attached to the inner wall of the long-tailed conical structure of the expansion section shell and is bonded with adhesive. The front end of the expansion section insulation layer is bonded to the end face of the heat insulation layer with adhesive. A 0.3 mm expansion gap is provided between the rear end of the throat liner and the front end of the expansion section insulation layer. After assembly and bonding, an ablation-resistant solid rocket motor nozzle is obtained.

[0078] The throat liner prepared in this embodiment has a density of 2.05 g / cm³, a SiC coating thickness of 60 μm, and a carbon layer thickness of 5 mm for the expansion section insulation layer. It still achieves the technical effects of the present invention, thus proving that within the above parameter range, the technical solution of the present invention has good feasibility and stability.

[0079] Example 5 Performance Testing To verify the performance of the ablation-resistant solid rocket motor nozzle prepared according to this invention, ground static ignition tests and performance tests were conducted on the nozzles prepared in Examples 2-4. The test conditions were: combustion chamber pressure 3.0 MPa, operating time 20 s.

[0080] Test sample: Nozzle prepared in Example 2.

[0081] Comparative Example 1: A throat liner made of conventional graphite material, with the remaining structure being the same as in Example 2.

[0082] Comparative Example 2: An expanded section insulation layer was prepared by winding a single high-silica fabric tape, and the rest of the structure was the same as in Example 2.

[0083] Experimental results: (1) Throat liner ablation performance: After the test, the inner and outer surfaces of the throat liner of the nozzle in Example 2 were smooth and intact, without macroscopic cracks or ablation marks. The throat diameter increased from φ45 mm to φ46.8 mm, the ablation amount on one side was 0.9 mm, and the average linear ablation rate was 0.045 mm / s, which was about 70% lower than the average linear ablation rate of Comparative Example 1. This confirms that the use of three-dimensional four-way woven carbon / carbon composite material combined with SiC coating can effectively improve the ablation resistance of the throat liner.

[0084] (2) Status of each functional layer: Post-experimental dissection revealed that the inner surface of the throat liner in Example 2 was protected by a SiC coating with no obvious ablation marks, and the overall structure was intact; the surface of the expansion section had slight ablation marks with ablation depth ≤2.0 mm, which was much lower than the total thickness of the diffuser section liner, and it was firmly bonded to the throat liner and the shell without any detachment or loosening; the temperature of the insulation layer was ≤180 ℃, which was much lower than the decomposition temperature of phenolic resin, and the insulation effect was good. The temperature of the insulation layer in Comparative Example 2 was 210 ℃, which was close to the decomposition temperature of phenolic resin, and the surface of the expansion section was severely ablated with obvious marks. This indicates that the composite structure of the insulation layer and the expansion section insulation layer of the present invention has a superior insulation effect. It also shows that the nozzle and its preparation method provided by the present invention significantly improve the ablation resistance, long-term working reliability and structural integrity of the nozzle through the synergistic design of materials, structure and process.

[0085] (3) Structural integrity: After the test, the nozzle of Example 2 had an intact overall structure, no deformation of the shell, no leakage marks on the sealing surfaces, and the sealing components were intact. Comparative Example 1 and Comparative Example 2 both showed obvious ablation damage.

[0086] Figure 2 The throat liner tooling structure is demonstrated. The tooling structure includes an upper ring and a lower ring. Polyacrylonitrile carbon fiber filaments are fixed to the lower ring of the tooling and woven in a three-dimensional, four-directional circular pattern. This allows for precise control of the geometry and fiber arrangement of the preform, thus laying the foundation for subsequent high-performance densification processes. The aforementioned mold can be used in the preparation of the throat liner, or any existing tooling capable of processing the throat liner structure described in this invention can be used; this invention is not limited to any particular method.

[0087] Figure 3 and Figure 4The structure of the insulation layer forming mold ensures the dimensional accuracy and internal structural uniformity of the insulation layer during the pressing process. The insulation layer forming mold consists of three parts: an upper mold, a lower mold, and a top plate. Temperature measuring holes are provided on both the upper and lower molds for temperature detection during the pressing process. The mold has a cylindrical structure, comprising an upper mold, a lower mold, a premix filling cavity, and a top plate. The lower mold is a hollow cylindrical structure. The upper part of the upper mold has a boss that abuts against the upper end face of the lower mold. The lower part of the upper mold is a conical structure. The top plate is located below the upper mold and is engaged in the inner cavity of the lower surface of the lower mold. The upper surface of the top plate abuts against the lower surface of the conical structure of the upper mold. The conical surface of the lower part of the upper mold and the inner wall of the lower mold form the premix filling cavity. Temperature measuring holes are provided on both the upper and lower molds for temperature detection during the pressing process. The above-described mold can be used to prepare the insulation layer, or any existing mold capable of processing the insulation layer structure described in this invention can be used; this invention is not limited to any particular mold.

[0088] Figure 5 and Figure 6 This is a schematic diagram of the mold structure for the expanded section insulation layer. The conical design of the mandrel ensures uniform tension distribution during the winding process. The mold for the expanded section insulation layer consists of a winding mandrel with a conical rear end, a winding baffle, and a nut. The front and rear ends of the winding mandrel have fixing holes or screw holes for fixing the winding mandrel to the fiber winding machine. The front end of the winding mandrel is the smaller end of the mold, and its outer diameter is smaller than that of its rear end. The winding baffle is fixed to the front end of the winding mandrel with a nut, and the expanded section insulation layer blank is formed by winding on the winding mandrel. The above-described mold can be used to prepare the expanded section insulation layer, or any existing mold capable of processing the expanded section insulation layer structure described in this invention can be used; this invention is not limited to any particular mold.

[0089] In the throat liner preparation process of this invention, the polyacrylonitrile carbon fiber filaments used are those with a general epoxy resin sizing agent applied to their surface at the factory, and the manufacturer is Zhongfu Shenying's T700-1K carbon fiber. Other types of carbon fiber filaments can also be used, as long as they can achieve the three-dimensional four-directional weaving for the ring layout described in this invention; this invention is not limited to any particular type.

[0090] In the preparation of the expansion section insulation layer of this invention, the adhesive used in the impregnated carbon fiber filaments and high-silica prepreg tape can be F01-36 phenolic resin produced by Xi'an Jingjian Paint Co., Ltd., or other types of adhesives suitable for wet winding that can achieve the effects of this invention. The mass percentage of carbon fiber filaments or high-silica tape to adhesive is (60~65):(35~50), and this invention does not limit this percentage.

[0091] The high-silica tape used in this invention can be purchased from Shaanxi Huatai New Material Co., Ltd., with a width of 30-60mm and a surface density of 200-300g / m2. This invention does not impose any limitations.

[0092] The phenolic resin mentioned in this invention is a thermosetting phenolic resin.

[0093] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing an ablation-resistant solid rocket motor nozzle, characterized in that, Includes the following steps: (1) The ablation-resistant solid rocket motor nozzle includes a throat liner, a heat insulation layer, an expansion section shell, and an expansion section insulation layer; (2) Machining of the expansion section shell The front part of the expansion section shell is provided with an integrated flange structure. The expansion section shell is integrally formed using alloy steel through existing machining methods. (3) Processing of throat liner (3.1) Preform preparation Using polyacrylonitrile carbon fiber filaments as raw materials, a three-dimensional four-way weaving is carried out on the throat liner tooling using a ring layout to obtain a ring-shaped throat liner preform with a bulk density of 0.7 to 1.1 g / cm3. (3.2) Pre-curing of precast structures The prepared throat liner preform is placed in an oven for pre-curing. After pre-curing, it is demolded to obtain the pre-cured throat liner blank. (3.3) Chemical vapor deposition In a deposition furnace, C3H6 is used as the carbon source gas and N2 is used as the carrier gas to perform pyrolytic carbon deposition on the pre-cured throat liner blank. The deposition process is repeated until the density of the pre-cured throat liner blank reaches 1.30 to 1.60 g / cm³, thus obtaining the throat liner blank. (3.4) Resin impregnation and carbonization densification In an impregnation furnace, the throat liner preform after chemical vapor deposition is impregnated with phenolic resin or furan resin under pressure; the impregnated throat liner preform is then carbonized in a carbonization furnace under N2 protection; the impregnation and carbonization processes are repeated until the density of the throat liner preform reaches 1.80 to 2.05 g / cm³, thus obtaining a denser throat liner preform. (3.5) High-temperature graphitization The densified throat liner blank is placed in a high-temperature graphitization furnace and graphitized under a N2 protective atmosphere. (3.6) Machining The graphitized throat liner blank is machined on its inner and outer surfaces. The outer surface is machined into a conical surface with a cone angle of 25° to 65°. The machining accuracy is controlled within ±0.10mm. An annular groove for inserting into the front of the expansion section shell is also machined on the throat liner blank, and it is adapted to the front of the expansion section shell. (3.7) Coating SiC powder or Si powder is sprayed onto the inner surface of the processed throat liner using low-pressure plasma spraying. The coating thickness is 20-60 μm, thus obtaining the formed throat liner. (4) Thermal insulation layer processing (4.1) Short high-silica fibers with a length of 25-50 mm, thermosetting phenolic resin and ethanol solvent are mixed evenly at a mass ratio of (40-50):(50-60):(4-15). The mixture is kneaded in a kneader to make the short high-silica fibers and thermosetting phenolic resin evenly mixed. Then it is transferred to a tearing machine for the first tearing to loosen the agglomerated fibers in the mixture. The torn mixture is spread on a screen for drying. After spreading it evenly, the dried mixture is placed in an oven for drying. The dried mixture is then transferred to a tearing machine for the second tearing. After tearing, a premix is ​​obtained. Then it is transferred to an oven for pre-drying to obtain a molding premix. (4.2) Preheat the insulation layer molding mold at 60~80℃ for 30~60min, put the pre-baked molding premix into the insulation layer molding mold, heat it to 85~100℃ at a heating rate of 0.2~0.5℃ / min, apply pressure of 5~10MPa, hold pressure for 30~60min for pre-curing, then heat it to 100~180°C at a heating rate of 0.5~0.7℃ / min, apply pressure of 10~20MPa, hold pressure for 100~150min for curing, cool down and demold to obtain the insulation layer blank, and machine it into an insulation layer according to the dimensions of the drawing; (5) Processing of the insulation layer of the expansion section The expansion section insulation layer consists of an inner carbon layer and an outer high-silica oxygen layer; (5.1) The inner carbon layer is made by wet winding of fibers. According to the size of the insulation layer of the expansion section, starting from the small end of the mold, the carbon fiber filaments impregnated with adhesive are selected and put into the fiber winding machine to perform the first layer of winding in an axial flat winding manner. Then, the second layer of winding is performed in an oblique winding manner. Then, the third layer of winding is performed in a radial annular winding manner. The axial flat winding, oblique winding and radial annular winding operations are repeated until the thickness of the carbon layer reaches 3 to 5 mm to obtain the carbon layer. (5.2) Wrap the outer layer of high silica layer around the carbon layer obtained in step (5.1); select a high silica prepreg tape with a width of 30-60mm and enter the fiber winding machine from the small end of the mold to one-third of the total length of the expansion section insulation layer, and use dense winding; after one-third of the total length of the expansion section insulation layer, use rapid winding; repeat the steps of dense winding and rapid winding until the high silica layer thickness reaches 8-10mm, then cut the tape, the winding ends, and the expansion section insulation layer blank is obtained; (5.3) After the winding is completed, several layers of absorbent felt are wrapped around the outer layer of the expansion section insulation blank in sequence, and then wrapped again with a porous isolation film, absorbent felt and vacuum bag in sequence. (5.4) Curing the wrapped expansion section insulation layer. After curing, demolding the wrapped expansion section insulation layer when it cools to below 50°C. Machining according to the dimensions in the drawing to obtain the expansion section insulation layer. (6) According to the drawings, the throat liner is provided with an annular groove at the rear, and the front part of the expansion section shell is embedded in the annular groove of the throat liner. The center of the throat liner is an airflow channel. The heat insulation layer fills the gap between the throat liner and the front part of the expansion section shell. The heat insulation layer is connected to the inner wall of the front part of the expansion section shell and is bonded with adhesive. The front part of the expansion section shell is provided with an integrated flange structure for bolting and assembly with the end face of the solid rocket engine combustion chamber. The expansion section heat insulation layer is tightly attached to the inner wall of the long-tailed conical structure of the expansion section shell and is bonded with adhesive. The front end of the expansion section heat insulation layer is bonded to the end face of the heat insulation layer with adhesive. An expansion gap of 0.2-0.3mm is provided between the rear end of the throat liner and the front end of the expansion section heat insulation layer. The expansion section heat insulation layer and the expansion section shell form a gradually expanding long-tailed channel. After assembly and bonding, an ablation-resistant solid rocket engine nozzle is obtained.

2. The method for preparing the ablation-resistant solid rocket motor nozzle according to claim 1, characterized in that: In step (3.1), the polyacrylonitrile carbon fiber filament is T700 grade polyacrylonitrile carbon fiber filament; during the weaving process, the volume fraction of polyacrylonitrile carbon fiber is controlled in the range of 45% to 55%, the weaving angle is controlled in the range of 25° to 40°, and the height of the knot is controlled in the range of 10 to 35 mm. In step (3.2), the pre-curing process involves raising the oven temperature from room temperature to 110-150°C at a rate of 1-3°C / min and holding it at that temperature for 1-3 hours; then raising the temperature to 220-250°C at a rate of 2-4°C / min and holding it at that temperature for 2-4 hours to complete the pre-curing. After the throat liner preform cools to below 70°C, the throat liner preform is removed to obtain the pre-cured throat liner blank.

3. The method for preparing the ablation-resistant solid rocket motor nozzle according to claim 1, characterized in that: In step (3.3), the flow rate ratio of C3H6 to N2 is (70~100):(1~5), the deposition temperature is 800~1200℃, the furnace pressure is 1.0~5.0kPa, the deposition time is 100~300h, and the deposition process is repeated 2~3 times.

4. The method for preparing the ablation-resistant solid rocket motor nozzle according to claim 1, characterized in that: In step (3.4), the pressure impregnation process involves impregnating under a vacuum of ≤120 Pa for 2–5 hours, followed by pressurization to 0.8–1.2 MPa and impregnation for 2–4 hours; during the carbonization process, the temperature is increased to 900–1000 ℃ at a rate of 2–5 ℃ / min for carbonization, and the carbonization time is 2–4 hours; the impregnation and carbonization processes are repeated 2–6 times. In step (3.5), during the graphitization process, the high-temperature graphitization furnace is heated to 2300-2600 ℃ at a heating rate of 5-20 ℃ / min, and held at that temperature for 2-5 h to carry out graphitization; In step (3.7), the spraying pressure is 300-800 Pa, the gas flow rate is controlled at 30-60 L / min, and the spraying distance is 50-200 mm.

5. The method for preparing the ablation-resistant solid rocket motor nozzle according to claim 1, characterized in that: In step (4.1), the mixing process is carried out in a mixing tank; the kneading speed is 20-50 rpm, and the kneading time is 30-120 min; the drying time is 12-48 hours, and the spreading thickness does not exceed 10 cm; the drying temperature is 60-100℃, and the drying time is 30-150 min; the speed of the tearing machine is 10-50 rpm during the first and second tearing processes; the pre-drying temperature in the oven is 70-80℃, and the pre-drying time is 60-120 min.

6. The method for preparing the ablation-resistant solid rocket motor nozzle according to claim 1, characterized in that: In step (5.1), the carbon fiber filament is a 1K carbon fiber filament; the temperature of the adhesive used to impregnate the carbon fiber filament is controlled at 30-60℃, the winding speed is controlled at 1-3m / s, and the tension of the carbon fiber filament during the winding process is controlled at 5-20N; the temperature of the adhesive tank of the fiber winding machine is set to 30-60℃; the number of times the axial flat winding, oblique winding and radial annular winding operations are repeated is 3-5 times.

7. The method for preparing the ablation-resistant solid rocket motor nozzle according to claim 1, characterized in that: In step (5.2), the high-silica prepreg tape is a high-silica tape impregnated with adhesive; the axial speed is controlled at 0.16~0.3mm / r during the tight winding process and at 0.3~0.7mm / r during the fast winding process; the width of the high-silica prepreg tape is 30~60mm; during the tight winding process, the overlap width of the high-silica prepreg tape is 25~55mm, and the tension of the high-silica prepreg tape is controlled at 200~500N during the tight winding process; during the fast winding process, the overlap width of the high-silica prepreg tape is 10~30mm, and the tension of the high-silica prepreg tape is controlled at 300~500N during the fast winding process.

8. The method for preparing the ablation-resistant solid rocket motor nozzle according to claim 1, characterized in that: In step (5.3), the pore size of the porous isolation membrane is 20-50 μm.

9. The method for preparing the ablation-resistant solid rocket motor nozzle according to claim 1, characterized in that: In step (5.4), the specific curing process of the wrapped expansion section insulation layer is as follows: (1) Start the heating program of the vacuum tank, raise the temperature from room temperature to 70-90℃ at a rate of 0.3-1.8℃ / min, hold for 1-3 hours, start the initial pressure of 0.5-1.5MPa at 50-70℃ at a rate of 0.01-0.06MPa / min, and after the holding period, raise the pressure to 2-3.5MPa and hold for 1-3 hours at a rate of 0.01-0.04MPa / min; (2) Heat to 100-130℃ and hold for 1-4 hours at a rate of 0.2-0.8℃ / min; (3) Heat to 160-180℃ and keep warm for 2-4 hours. The heating rate is 0.5-0.8℃ / min.

10. An ablation-resistant solid rocket motor nozzle, characterized in that: The system includes a throat liner, a heat insulation layer, an expansion section shell, and an expansion section insulation layer. The expansion section shell has a long-tailed conical structure. The rear of the throat liner has an annular groove, and the front of the expansion section shell is embedded in the annular groove of the throat liner. The center of the throat liner is a gas flow channel. The heat insulation layer fills the gap between the throat liner and the front of the expansion section shell. The heat insulation layer is connected to the inner wall of the front of the expansion section shell. The front of the expansion section shell has an integrated flange structure for bolting to the end face of the solid rocket motor combustion chamber. The expansion section insulation layer consists of an inner carbon layer and an outer high-silica layer. The expansion section insulation layer is tightly attached to the inner wall of the long-tailed conical structure of the expansion section shell. The front end of the expansion section insulation layer is bonded to the end face of the heat insulation layer with adhesive. A 0.2-0.3 mm expansion gap is provided between the rear end of the throat liner and the front end of the expansion section insulation layer. The expansion section insulation layer and the expansion section shell form a gradually expanding long-tailed channel, constituting the inner wall protective layer of the gas expansion acceleration channel.

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