A method for replacing and repairing the composite liner of the converging and straight sections of a long-tail nozzle.

Abstract

This invention belongs to the field of small solid rocket motor technology, specifically disclosing a method for replacing and repairing the composite liner of the converging and straight sections of a long-tail nozzle. First, the composite liner of the converging and straight sections of the long-tail nozzle is removed without damaging the metal shell. After verifying that the metal shell's performance meets the usage requirements through dimensional, hydraulic, and weld inspections, the metal shell is bonded to the prepared composite liner and then capped and bonded to the small port of the long-tail nozzle. Finally, the performance of the replaced and repaired long-tail nozzle is tested to ensure that the repaired product meets the usage requirements. This method preserves the original metal shell of the long-tail nozzle, avoiding the need for complete replacement of the entire long-tail nozzle. It significantly reduces costs during the repair process. By adjusting the mating dimensions of the composite liner of the converging and straight sections, effective use of diffuser sections with different mating dimensions is achieved, realizing efficient and low-cost replacement and repair of the composite liner of the converging and straight sections of the long-tail nozzle.

Description

Technical Field

[0001] This invention belongs to the field of small solid rocket engine technology, and specifically discloses a method for replacing and repairing the composite liner of the converging section and the straight section of the long tail nozzle. Background Technology

[0002] The long-tail nozzle is a crucial component of a solid rocket motor. Its function is to form a combustion channel during the combustion of propellant, converting chemical energy into thrust kinetic energy, providing excellent thermal protection, and ensuring normal engine operation. Over time, defects such as debonding and cracking may appear in the composite liner of the long-tail nozzle. This can lead to burn-through during operation, causing a sudden surge in lateral thrust within the solid rocket motor, resulting in abnormal missile flight and posing a serious safety hazard.

[0003] Currently, for long-tail nozzles with quality defects in the composite liner of the convergent and straight sections, the entire nozzle is replaced, which is costly. Therefore, there is an urgent need to explore an efficient and low-cost method for repairing the composite liner of the convergent and straight sections of long-tail nozzles. Summary of the Invention

[0004] To address the problems in the background art, this invention discloses a method for replacing and repairing the composite liner of the converging section and straight section of a long-tail nozzle, achieving the replacement and repair of the composite liner of the converging section and straight section of the long-tail nozzle at a lower cost, and ensuring that the repaired product meets the usage requirements.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0006] A method for replacing and repairing the composite liner of the converging section and straight section of a long-tail nozzle includes the following steps:

[0007] Step 1: After heating the converging and straight sections of the long tail nozzle to be repaired, remove the composite liner, clean the residual adhesive residue inside the metal shell, and then test the dimensions and performance of the metal shell to ensure that the performance of the metal shell meets the usage requirements.

[0008] Step 2: The prepreg of the material to be used for the composite liner is heated and pressurized in a special mold to prepare the composite liner, thus completing the molding preparation of the composite liner;

[0009] After the composite lining prepared in Step 3 and Step 2 is visually inspected and found to have no visible defects, the upper and lower tolerances of the composite lining fit dimensions in the converging section and straight section are calculated according to the requirements of the diffusion section fit dimensions and gap control, and then the machining is carried out according to the design drawings.

[0010] Step 4: Perform X-ray digital imaging inspection on the composite lining after machining in Step 3 to determine its internal quality. If the internal quality of the composite lining meets the requirements, proceed to the bonding process.

[0011] Step 5: Sandblast the inner surface of the metal shell treated in Step 1 until the metal on the inner surface of the metal shell is silvery white. Use room temperature curing epoxy adhesive to bond the metal shell to the composite lining inspected in Step 4. Apply pressure with tooling during bonding and keep it under pressure for 20-24 hours.

[0012] Step 6: The plug is prepared by molding process, using glass fiber and phenolic materials as raw materials, and is formed by heating and pressurizing in a special mold.

[0013] Step 7: Use silicone rubber to bond the plug prepared in step 6 to the small port of the long tail nozzle treated in step 5.

[0014] Step 8: Perform an airtightness test on the long tail nozzle obtained in Step 7, and observe by injecting water. If the pressure is stabilized for 1 minute under the required pressure, it is determined that the replacement and repair of the composite liner of the converging section and the straight section of the long tail nozzle is complete.

[0015] Furthermore, in the method for replacing and repairing the composite liner of the converging section and the straight section of the long tail nozzle, in step 1, the converging section and the diffuser section of the long tail nozzle to be repaired are heated at 200℃~280℃ for 2~4 hours to destroy the bonding structure of the liner material. After the heating treatment, the composite liner of the converging section and the diffuser section of the long tail nozzle is pressed out.

[0016] Furthermore, in the method for replacing and repairing the composite liner of the converging section and straight section of the long tail nozzle, in step 1, the dimensions of the metal shell are measured, and then the metal shell is subjected to hydraulic testing. The testing pressure is 1.2 times its maximum working pressure and lasts for 1 minute. After the hydraulic testing, the dimensions are measured again to check whether the metal shell has leaked and / or has residual deformation, so as to ensure that the performance of the metal shell meets the usage requirements.

[0017] Furthermore, in the method for replacing and repairing the composite liner of the converging section and straight section of the long tail nozzle, step 1 also requires X-ray non-destructive testing of the weld seam of the metal shell to ensure that the inner and outer surfaces of the weld seam of the metal shell are flat with the substrate of other parts of the metal shell, and that the appearance and internal quality of the metal shell meet the Class II quality requirements specified in QJ1842.

[0018] Furthermore, in the method for replacing and repairing the composite liner of the converging section and straight section of the long-tail nozzle, in step 2, the prepreg is pre-baked at 110°C for 10 minutes. The prepreg is then quickly extruded into a ball and added to the mold cavity. After the mold is closed, pressure is applied. Timing begins when the curing temperature is reached. The heating device is adjusted so that the temperature in the mold cavity is 155-165°C. The temperature and pressure are maintained for 25-30 minutes. After pressing for the specified time, the product is removed, the product serial number is recorded, and the appearance is inspected to check for cracks or missing material defects. If any of the above defects are visible to the naked eye, the product is deemed unqualified, and the unqualified product is removed, labeled, and stored in isolation.

[0019] Furthermore, in the method for replacing and repairing the composite liner of the converging section and straight section of the long tail nozzle, in step 4, X-ray digital imaging inspection must ensure that there are no cracks, looseness, or high-density inclusions exceeding the acceptance standard size inside the product.

[0020] Furthermore, in the method for replacing and repairing the composite liner of the converging section and straight section of the long-tail nozzle, in step 7, the raw materials for the plug are glass fiber and phenolic material. The baked prepreg is quickly extruded into a ball and added to the mold cavity. After the mold is closed, pressure is applied. Once the curing temperature is reached, timing begins. The heating device is adjusted, and the temperature in the mold cavity is 155-165℃. The temperature and pressure are maintained for 10-15 minutes. After the plug is pressed for the specified time, the product is taken out, the product serial number is recorded, and the appearance is inspected to see if there are any defects such as cracks, looseness, or missing material. If any of the above defects are visible to the naked eye, the product is judged to be unqualified, the unqualified product is removed, and it is marked and stored in isolation.

[0021] Furthermore, in the method for replacing and repairing the composite liner of the converging section and straight section of the long tail nozzle, step 8 requires a pressure of 0.100±0.002MPa during the airtightness test.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] This invention discloses a method for replacing and repairing the composite liner of the converging and straight sections of a long-tail nozzle. First, without damaging the metal casing, the composite liner of both sections is removed. After verifying that the metal casing meets performance requirements through dimensional, hydraulic, and weld inspections, the metal casing is bonded to the prepared composite liner and then capped and bonded to the small port of the long-tail nozzle. Finally, the replaced and repaired long-tail nozzle undergoes performance testing to ensure that the repaired product meets usage requirements. This method preserves the original metal casing of the long-tail nozzle, avoiding the need for complete replacement and significantly reducing costs during the repair process. Furthermore, due to significant dimensional deviations in the manufacturing process of the diffuser sections that mate with the converging and straight sections, this invention proposes a gap-controlled processing scheme. The mating dimensions of the composite materials in the converging and straight sections are adjusted for different diffuser section mating dimensions to ensure that the gap remains within a controllable range during docking. This allows for effective mating of diffuser sections with different mating dimensions, achieving efficient and low-cost replacement and repair of the composite liner of the converging and straight sections of a long-tail nozzle. Attached Figure Description

[0024] Figure 1 This is a flowchart of the method for replacing and repairing the composite liner of the converging section and straight section of the long tail nozzle according to the present invention.

[0025] Figure 2 This is a dimensional inspection diagram of the metal casing of the long-tail nozzle in this invention;

[0026] Figure 3 This is a schematic diagram of the completed bonding state of the composite lining of the present invention;

[0027] Figure 4 This is a machining dimension drawing of the composite liner for the converging and straight sections of the long-tail nozzle. Detailed Implementation

[0028] To better understand the present invention, the following embodiments further illustrate the content of the invention, but the scope of protection of the present invention is not limited to the following embodiments. Numerous specific details are set forth in the following description to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the present invention can be practiced without one or more of these details.

[0029] Combined with appendix Figure 1-4 This invention details a method for replacing and repairing the composite liner of the converging section and straight section of a long-tail nozzle, as described in the present invention. Figure 1 As shown, the implementation process mainly includes: removal and hydraulic testing of the original nozzle composite liner, dimensional measurement, weld inspection, processing and fabrication of the composite liner, machining and flaw detection, bonding of the composite liner, fabrication and bonding of the plug, and airtightness testing of the repaired long tail nozzle, etc. The specific steps for replacing and repairing the composite liner are as follows:

[0030] Step 1: Turn on the oven and blower, set the temperature to 250℃, place the original long-tail nozzle convergent section and straight section in the oven, keep it warm for 2-4 hours after reaching the set temperature, take out the nozzle, place it on the nylon fixture with the large end facing down, place a steel pressure block in the inner hole of the small end, tap the pressure block or use a spinning fixture to press the inner liner out of the nozzle housing, and clean the residual adhesive residue inside the metal housing.

[0031] according to Figure 2 Dimensions A to I are measured and the measured values ​​are recorded. The metal shell of the nozzle is subjected to hydraulic testing at 1.2 times the maximum working pressure for 1 minute. After the hydraulic test, the metal shell of the nozzle is visually inspected and its dimensions are measured again. The metal shell is not allowed to leak. The cross-sectional diameters E and F are measured again. If the difference between the second measurement value and the corresponding dimension measured at the first time before the hydraulic test is not greater than 0.1 mm, it is determined that there is no residual deformation in the long tail tube shell.

[0032] X-ray inspection of the weld seams of the nozzle metal shell shall be performed, and the internal quality shall meet the Class II quality requirements specified in QJ1842.

[0033] Step 2: The inner lining material is glass fiber and phenolic material. The prepreg after pre-baking is soft, non-sticky and non-pricking. After the material is dried, the first piece of product is pressed. The pre-baked material must ensure that no glue flows out during pressing. After pressing, the first piece of product is inspected. The product surface must be flat and free from looseness and material shortage.

[0034] Pre-dry the prepreg at 110℃ for 10 minutes. Quickly extrude the prepreg into a ball and add it into the mold cavity. After closing the mold, apply pressure and start timing when the curing temperature is reached. The time from entering the mold to starting timing should not exceed 40 minutes. Adjust the heating device to keep the temperature in the mold cavity at 160±5℃. Maintain the temperature and pressure for 25 to 30 minutes. After pressing for the specified time, take out the product and record the product serial number.

[0035] Step 3: Inspect the appearance of the composite lining product prepared in Step 2 to see if there are any defects such as cracks or missing materials. If any of the above defects are visible to the naked eye, the product is deemed unqualified, the unqualified product is removed, marked and stored in isolation.

[0036] according to Figure 4For dimensioning and machining, dimensions P and Q are calculated as follows: Measure the axial and radial fit dimensions of the diffuser section. Subtract 0.10mm and 0.20mm from the axial fit dimension of the diffuser section, respectively. The resulting values ​​are the upper and lower tolerances of the axial fit dimension P of the composite lining in the converging and straight sections, respectively. Subtract 0.20mm and 0.36mm from the radial fit dimension of the diffuser section, respectively. The resulting values ​​are the upper and lower tolerances of the radial fit dimension Q of the composite lining in the converging and straight sections, respectively. Machining is then performed on the composite lining according to the obtained tolerances and design drawing requirements.

[0037] Step 4: Use X-ray digital imaging to perform non-destructive testing on the composite liner blank. The product must be free of cracks, looseness, and high-density inclusions exceeding the acceptance standard size. After the flaw detection is qualified, the composite liner blank is machined according to the drawing.

[0038] Step 5: Visually inspect the metal casing of the long-tail nozzle. It should be free of rust and mechanical damage. The surface of the composite liner should be smooth, free of cracks and mechanical damage. The end face should be free of chipping with dimensions greater than 5mm × 1mm × 1mm in the circumferential × radial × axial direction. Sandblast the inner surface of the casing to remove residual adhesive residue until the metal is silvery-white. Wipe the inner surface of the long-tail nozzle metal casing and the outer surface of the composite liner with gauze soaked in anhydrous ethanol. Allow to air dry at room temperature for 10 minutes. Perform a trial assembly of the composite liner and the long-tail nozzle metal casing. The liner should be able to rotate within the casing without significant gaps. Figure 3 As shown, the non-metallic step at the large-diameter end is flush with the metal step surface. The threads of the long-tail nozzle's metal shell are protected with masking tape. A beaker is placed on an electronic scale. 115g of high-temperature resistant epoxy adhesive component A and 27.5g of component B are poured into the beaker sequentially. Component A is based on amino epoxy resin and contains toughening agents and fillers, while component B is a modified curing agent. The mixture is stirred thoroughly and set aside. Using gauze and a utility knife, the prepared adhesive is evenly applied to the bonding surfaces of the long-tail nozzle's metal shell and composite lining. It should be noted that in winter when the room temperature is too low, it is permissible to leave the epoxy resin and long-tail nozzle unmixed before application. Place the nozzle metal shell and liner in an oven at 30℃~50℃ for 1 hour; place the long-tail nozzle metal shell with the large diameter end facing up, and slowly rotate the liner clockwise to press it into the metal shell until the liner cannot be pressed down by hand. There should be glue overflowing from both ends of the mating surface. Clean the overflowing glue with gauze. Place the long-tail nozzle in the pressing fixture, place the nylon pressing block at the converging section of the inner surface of the liner, and apply pressure to the pressing block by tightening the fixture. After applying pressure, clean the overflowing glue with gauze. After the non-metallic step at the large diameter end is flush with the metal step surface, keep it under pressure and stand for more than 20 hours. Disassemble the pressing fixture and remove the paper tape from the threads.

[0039] Step 6: The sealing raw materials are glass fiber and phenolic materials. Before each batch of prepreg is pressed, the amount of material added and the pre-drying parameters need to be adjusted. The prepreg after pre-drying is soft, not sticky or prickly. After the material is dried, the first piece of product is pressed. The material after pre-drying must ensure that no glue flows out during pressing. After pressing, the first piece of product is inspected. The product surface should be flat and free from looseness or missing material.

[0040] The dried prepreg is quickly extruded into a ball and added to the mold cavity. After the mold is closed, pressure is applied. Once the curing temperature is reached, the time from the time the material is put into the mold to the start of the timer should not exceed 40 minutes. The heating device is adjusted to keep the temperature in the mold cavity at 160±5℃. The temperature and pressure are maintained for 10 to 15 minutes. After the specified time is reached, the product is removed, the product serial number is recorded, and the appearance is inspected to see if there are any defects such as cracks, looseness, or missing material. If any of the above defects are visible to the naked eye, the product is judged to be unqualified, the unqualified product is removed, and it is marked and stored in isolation.

[0041] Step 7: Trial installation of the plug. Place the plug into the small port of the composite liner of the long tail nozzle treated in Step 5. The plug should be able to rotate manually. Wipe the outer surface of the plug and the inner surface of the small port of the composite liner with gauze dipped in anhydrous ethanol. Let it air dry at room temperature for 10 minutes. Apply an appropriate amount of GD414 silicone rubber evenly to the bonding surfaces of the plug and the composite liner. The thickness should cover the base color of the bonding surfaces of the plug and the composite liner. Slowly rotate the plug from the large port of the liner and press it into the small port of the liner in a clockwise direction. Clean the excess glue with gauze. Press the pressure block on the plug and let it stand under pressure for more than 20 hours.

[0042] Step 8: Perform an airtightness test on the replaced and repaired long tail nozzle. Under a pressure of 0.100±0.002MPa, the pressure should be stabilized for 1 minute, and there should be no pressure drop.

[0043] The replaced and repaired long tail nozzle underwent Y / Z vibration tests, X / Y impact tests, transportation tests, and temperature shock tests. The transportation tests included 700 km of asphalt or cement road transportation and 400 km of dirt road transportation tests. In the temperature shock test, the nozzle was first placed in a low-temperature chamber and then transferred to a high-temperature chamber for one cycle, which was repeated three times. The test temperature ranged from 50°C to -50°C, with the temperature held for 18 hours and the temperature transition time not exceeding 5 minutes. Ignition tests were also conducted with the engine at +50°C, -50°C, and 23°C. After the tests, the long tail nozzle structure remained intact, with no overheating or discoloration. The experimental results demonstrate that the method used in this invention can replace and repair faulty composite linings, and the repaired product meets the usage requirements.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A method for replacing and repairing a convergent section and a straight section composite inner liner of a long tail nozzle, characterized in that, The method comprises the following steps: Step 1, the convergent section and straight section of the long tail nozzle to be repaired are heated, and the composite inner liner is taken out, the residual glue stains in the metal shell are cleaned, and the size and performance of the metal shell are detected to ensure that the performance of the metal shell meets the use requirements; Step 2, the prepreg of the composite inner liner is prepared by heating and pressing in a special mold, and the mold pressing of the composite inner liner is completed; Step 3, after the composite inner liner prepared in step 2 is inspected and no visible defects are found, the upper and lower tolerances of the composite inner liner fitting size of the convergent section and the straight section are calculated according to the fitting size and gap control requirements of the diffuser section, and mechanical processing is performed according to the design drawing requirements; Step 4, the composite inner liner after mechanical processing in step 3 is subjected to X-ray digital imaging inspection to judge its internal quality, and the composite inner liner with internal quality meeting the requirements enters the bonding process; Step 5, the inner surface of the metal shell treated in step 1 is subjected to sand blasting treatment until the inner surface of the metal shell is silver white, and the metal shell and the composite inner liner subjected to the inspection in step 4 are bonded together by using room temperature curing epoxy adhesive, and a tool is used for pressing during bonding, and the pressure is kept for 20-24 hours; Step 6, the plug is prepared by mold pressing, and glass fiber and phenolic material are used as raw materials, and the plug is formed by heating and pressing in a special mold; Step 7, the plug prepared in step 6 is bonded to the small port of the long tail nozzle treated in step 5 by using silicone rubber; Step 8, the long tail nozzle obtained in step 7 is subjected to air tightness detection, and water injection observation is performed, and under the required pressure, the pressure maintaining time is 1 minute, and then it is judged that the replacement and repair of the composite inner liner of the convergent section and the straight section of the long tail nozzle are completed.

2. The method for replacing and repairing the composite liner of the converging section and straight section of the long-tail nozzle according to claim 1, characterized in that, In step 1, the convergent section and the diffuser section of the long tail nozzle to be repaired are heated at 200-280℃ for 2-4 hours to destroy the adhesive structure of the inner liner material, and after heating treatment, the composite inner liner of the convergent section and the diffuser section of the long tail nozzle is pressed out.

3. The method of claim 2, wherein the step of replacing the convergent section and the straight section of the complex liner of the long tail nozzle is performed by using a replacement tool having a shape corresponding to the shape of the convergent section and the straight section of the complex liner of the long tail nozzle. In step 1, the size of the metal shell is measured, and then the hydraulic detection of the metal shell is performed, the detection pressure is 1.2 times of the maximum working pressure, and the duration is 1 minute, and after the hydraulic detection, the size is measured again to check whether the metal shell has leakage and / or residual deformation, so as to ensure that the performance of the metal shell meets the use requirements.

4. The method of claim 3, wherein the step of replacing the convergent section and the straight section of the complex liner of the long tail nozzle is performed by using a replacement tool having a shape corresponding to the shape of the convergent section and the straight section of the complex liner of the long tail nozzle. In step 1, X-ray nondestructive testing of the weld of the metal shell is also required to ensure that the inner and outer surfaces of the weld of the metal shell and other parts of the metal shell are flat, and the appearance and internal quality of the metal shell meet the II level quality requirements specified in QJ1842.

5. The method of claim 3, wherein the step of replacing the convergent section and the straight section of the complex liner of the long tail nozzle is characterized by, In step 2, the prepreg is pre-dried at 110℃ for 10 minutes, the dried prepreg is quickly extruded into a lump and added to the mold cavity, the mold is closed and pressurized, the timer starts when the temperature reaches the curing temperature, the heating device is adjusted, the temperature in the mold cavity is 155-165℃, and the product is taken out after 25-30 minutes of pressure holding, the product serial number is recorded, and the appearance is inspected to check whether there is a crack or a material defect, if one of the above visible defects exists, the product is judged as unqualified, the unqualified product is removed, and the unqualified product is marked and stored separately.

6. The method of claim 1 wherein the convergent section and straight section composite liner replacement repair method further comprises: In Step 4, X-ray digital imaging inspection is used to ensure that there are no cracks, porosity, and high-density inclusions exceeding the acceptance standard size inside the product.

7. The method of claim 1 wherein the step of replacing the convergent section and straight section composite liner of the afterburner nozzle further comprises the step of: In Step 7, the raw materials for the plug cap are glass fiber and phenolic material. The baked pre-impregnated material is quickly extruded into a mass and added to the mold cavity. After the mold is closed, pressure is applied. Timing starts after reaching the curing temperature. The heating device is adjusted, and the temperature in the mold cavity is 155-165°C. The product is removed after 10-15 minutes of holding and pressure. The product number is recorded, and the appearance is inspected for cracks, porosity, material defects, etc. If any of the above defects are visible to the naked eye, the product is judged to be unqualified, and the unqualified product is removed, marked, and stored separately. ​ 8. The method for replacing and repairing the composite liner of the converging section and straight section of the long tail nozzle according to claim 1, characterized in that, In Step 8, the air tightness test requires a pressure of 0.100±0.002MPa.

Images