Sealing and cleaning process for flow channel of 3D printed rocket engine combustion chamber

Abstract

The present application relates to the technical field of part processing, in particular to a sealing and cleaning process for a flow channel of a 3D printed part of a rocket engine combustion chamber, comprising the following steps: S1, sealing; S2, cleaning; S2-1, water bath dissolution; S2-2, solvent oil immersion treatment; S2-3, anhydrous ethanol immersion treatment; S2-4, rinsing; S2-5, blowing and drying; the present application is sealed by special paraffin vacuum perfusion, the paraffin melting temperature is lower than the tempering temperature of the combustion chamber material, does not change the internal structure of the material, does not affect the mechanical properties and high temperature resistance of the combustion chamber, and the hardness after solidification is moderate, the sealing stability is strong, and the machining waste and cooling liquid can be completely prevented from invading; the step-by-step cleaning process is used, the material used for the 3D printed combustion chamber is not corrosive, there is no harmful substance residue after the paraffin is dissolved, the cleaning is completely volatilized after the cleaning is completed, the inner wall of the flow channel is not polluted, and the flow channel cleanliness and the base material integrity are perfectly guaranteed.

Description

Technical Field

[0001] This invention relates to the field of parts processing technology, specifically to a sealing and cleaning process for the flow channel of a 3D printed part of a rocket engine combustion chamber. Background Technology

[0002] The rocket engine combustor is a core component of the propulsion system. Its inner wall is printed with precision regenerative cooling channels to circulate the cooling medium and remove the large amount of heat generated during combustion, ensuring stable operation under extreme conditions of high temperature and high pressure. These cooling channels have small apertures and complex, tortuous paths; some channels are blind holes or have interwoven multi-hole structures, and no foreign matter is allowed inside. However, after the combustor is 3D printed, metal shavings, cutting fluid, and coolant generated during subsequent machining processes (turning, milling, grinding, drilling, etc.) can easily seep into and clog the cooling channels. Tiny shavings become stuck in the corners and narrow gaps of the channels, making them difficult to clean using conventional methods; residual coolant can corrode the inner wall of the channels, damaging the surface properties of the substrate. This can range from affecting the efficiency of the cooling medium flow to causing complete blockage of the channels, rendering the entire combustor unusable. Therefore, it is necessary to seal and protect the channels during machining and then clean them after machining is completed.

[0003] Current methods for protecting cooling channels include putty, sealing tape, and resin sealing, which have the following drawbacks: putty can only seal open channels and cannot be adapted to complex, tortuous, and porous internal channels, resulting in dead zones in the seal; sealing tape has poor adhesion and is easily detached due to machining vibrations, causing the protection to fail; resin sealing has high curing strength after curing and is difficult to completely remove, leaving residual resin that can contaminate the channel and easily scratch the inner wall of the channel during the removal process.

[0004] Meanwhile, existing cleaning methods for cooling channels mostly involve high-pressure water flushing and mechanical blowing, which cannot thoroughly clean impurities and blockage residues in complex channels. Furthermore, there is no targeted gentle cleaning process, which can easily damage the surfaces of materials such as CuCr1Zr alloy and 304 stainless steel used in 3D printed combustion chambers. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a sealing and cleaning process for the flow channels of 3D-printed parts in the combustion chamber of a rocket engine.

[0006] A sealing and cleaning process for the flow channel of a 3D-printed rocket engine combustion chamber includes the following steps: S1, Sealing The flow channels of the combustion chamber are pre-cleaned, then the combustion chamber is placed into the vacuum injection equipment and the cavity of the vacuum injection equipment is sealed. The vacuum injection equipment is evacuated until the vacuum degree is -0.1~-0.095MPa, and maintained for 10~15min. Then, molten paraffin is injected into the vacuum injection equipment so that the paraffin immerses all the openings of the flow channels of the combustion chamber. The injection lasts for 20~30min. After the injection is completed, the pressure inside the vacuum injection equipment is restored to atmospheric pressure at a rate of 0.02~0.03MPa / min. Then, the combustion chamber is removed and allowed to cool naturally at room temperature for 50~60 minutes to obtain a combustion chamber with sealed flow channels. S2, Cleaning S2-1, Dissolve in water bath After the flow channel-sealed combustion chamber is machined, it is immersed in a constant temperature water bath to dissolve the paraffin inside the combustion chamber. The temperature of the constant temperature water bath is 60~70℃, and the immersion time is 20~25min. S2-2, Solvent oil immersion treatment Remove the combustion chamber treated with S1-1, allow it to cool naturally to room temperature, and then immerse it in solvent oil at a temperature of 25~70℃ for 25~65 minutes. Then the combustion chamber is removed, and the residual solvent oil on the surface of the combustion chamber is dried using compressed air at a pressure of 0.5~0.6MPa; S2-3, Anhydrous ethanol immersion treatment The combustion chamber treated with S2-2 was immersed in anhydrous ethanol for alcohol cleaning. The temperature of the anhydrous ethanol was 25~30℃ and the immersion time was 5~10min. S2-4, Rinse Take out the combustion chamber after S2-3 treatment, first rinse the flow channel with high-pressure pure water of 5.5~6.5MPa for 3~5 minutes, and then soak it in pure water at a temperature of 25~30℃ for 18~20 minutes. S2-5, Purge and dry Remove the combustion chamber after S2-4 treatment, and use compressed air to purge all flow channels in reverse through each hole. After purging, place the combustion chamber in a vacuum drying oven and dry it at 50~60℃ for 20~30 minutes to complete the flow channel cleaning.

[0007] Furthermore, in S1, the method for pre-cleaning the flow channels of the combustion chamber is as follows: First, flush the flow channel with high-pressure pure water at 5.5~6.5MPa, then purge the flow channel hole by hole with compressed air at 0.5~0.6MPa. After purging, place the combustion chamber in a drying oven and dry it at 40~50℃ for 30~60 minutes.

[0008] Note: Rinsing and purging ensure that the flow channel is unobstructed and free of any previous impurities; drying removes moisture from the flow channel to avoid affecting the density of subsequent paraffin injection.

[0009] Furthermore, in S2-2, ultrasonic treatment is applied during the soaking process, with an ultrasonic frequency of 30~40kHz and a power of 600~700W.

[0010] Explanation: Ultrasonic vibration separates residual paraffin and debris from the material surface inside the flow channel and on the combustion chamber surface, improving the solvent cleaning effect.

[0011] Furthermore, in S2-4, after soaking, the combustion chamber is subjected to high-pressure spraying. Pure water is used for high-pressure spraying, the pressure of which is 0.2~0.3MPa and the time is 45~60min. The spraying direction corresponds to the inlet and outlet of the flow channel.

[0012] Note: High-pressure spraying is used to assist in cleaning, ensuring that the inside of the flow channel is thoroughly cleaned and completely removing alcohol residue, trace debris and impurities from the surface of the combustion chamber and the flow channel.

[0013] Furthermore, in S2-4, the resistivity of the purified water at 25°C is ≥18.2 MΩ·cm, and the pH is 6.5~7.5.

[0014] Note: Using purified water with the above parameters ensures extremely low ion content, preventing ions from corroding the CuCr1Zr alloy and stainless steel surfaces; using neutral purified water prevents acidic or alkaline water from corroding the combustion chamber materials.

[0015] Further, in S2-1, the machining method is as follows: the outer wall, end face, mounting flange, and docking port of the combustion chamber are turned, milled, and drilled. After machining, the residual cutting fluid on the surface of the combustion chamber is wiped off with cotton cloth and alcohol, and the machining is completed.

[0016] Note: Although 3D printing can produce complex shapes, the dimensional accuracy and surface finish of its formed parts usually cannot directly meet the assembly requirements of high-performance rocket engines. Therefore, machining is absolutely necessary to ensure uniform combustion chamber wall thickness, flat end face, flange flatness, bolt hole position accuracy, and port shape and size.

[0017] Furthermore, in S1, the paraffin wax is modified paraffin wax, and the method for preparing the modified paraffin wax is as follows: Paraffin wax and silicone resin were mixed and stirred at a mass ratio of 2.5 to 4:3 at 70 to 80°C and 450 to 480 rpm to obtain the first mixture. Under nitrogen protection, 1g of alumina and 10-20mL of isoparaffin were stirred and mixed at 100-110℃ for 1-1.5h, then 0.1g of octadecyltrimethoxysilane was added and the mixture was heated to 150-160℃ and refluxed for 3-4h. The resulting reaction solution was cooled to 50-60℃ and then centrifuged, washed and dried to obtain modified alumina. The first mixture and modified alumina were subjected to a mass ratio of 3.5 to 4.5:1, and were first sheared at 3000 to 3500 rpm for 30 to 40 minutes, and then ultrasonically treated for 10 to 15 minutes to obtain the second mixture. Add silane oligomer to the second mixture, stir at 200-300 rpm for 5-6 minutes, then add tetraethyl orthosilicate and dibutyltin dilaurate in sequence, and continue stirring for 10-15 minutes. The mass ratio of the second mixture: silane oligomer: tetraethyl orthosilicate: dibutyltin dilaurate is 100:18:5:0.5-1, to obtain modified paraffin.

[0018] Explanation: Adding silicone resin to paraffin wax improves the cohesive strength and thermomechanical stability of the sealing material, making it less prone to microcracks due to vibration or temperature fluctuations in subsequent processes, thus maintaining the integrity of the seal. Furthermore, silicone resin has a higher heat distortion temperature than paraffin wax, allowing the sealing material to maintain good shape and strength even under localized high temperatures generated during machining. After silane modification, alumina can be uniformly dispersed in the paraffin-silicone resin matrix, thereby utilizing its high hardness and high aspect ratio to form a more effective anti-permeation path within the matrix. This further prevents micron-sized impurities (such as machining debris and dust) from entering the flow channel during subsequent processing, resulting in a barrier effect far superior to pure paraffin wax. During subsequent cleaning, the siloxane network in the modified paraffin can be further cross-linked and cured on the surface of the flow channel by the swelling effect of the solvent oil, allowing components such as silane oligomers and tetraethyl orthosilicate to form a strong siloxane polymer functional film in situ under the action of the catalyst dibutyltin dilaurate. This functional film can isolate the flow channel metal substrate from direct contact with air and moisture, providing temporary anti-corrosion protection during storage and subsequent processes. It can also reduce the surface energy of the inner wall of the flow channel, improve the fluidity of the medium, and thus enhance the cleaning effect of subsequent anhydrous ethanol and pure water.

[0019] Furthermore, the method for preparing the silane oligomer is as follows: Isopropanol and deionized water were mixed at a volume ratio of 1:1 to 1.2 to obtain a mixture. Then, p-toluenesulfonic acid was added to the mixture and stirred until completely dissolved. Then, methyltrimethoxysilane and diphenyldimethoxysilane were added sequentially to obtain a reaction system. The ratio of mixture:p-toluenesulfonic acid:methyltrimethoxysilane:dimethyldimethoxysilane was 100 ml:0.1 g:18 g:7-8 g. The reaction system was heated to 65-70°C and stirred for 3.5-4 hours. After the reaction was completed, the reaction system was cooled to 35-40°C and hexamethyldisilazane was added. The mass ratio of the reaction system to hexamethyldisilazane was 50-55:20. The reaction was stirred for another 1-1.5 hours to obtain the reaction solution. After cooling the reaction solution to room temperature, wash it to obtain an organic phase. Add 18-20g of anhydrous sodium sulfate to 150mL of the organic phase and react for 20-30min. After the reaction is complete, filter the solution, evaporate the filtrate by rotary evaporation, and then dry it under vacuum to obtain silane oligomers.

[0020] Explanation: The introduction of benzene rings into diphenyldimethoxysilane, which possess extremely high thermal stability and chemical inertness, increases the glass transition temperature of the entire polymer system. This allows the functional film formed by the modified paraffin to maintain its glassy state at higher temperatures, thereby preserving its mechanical strength and dimensional stability. Consequently, it can better withstand the high temperatures such as preheating before engine operation. Methyltrimethoxysilane and diphenyldimethoxysilane can form a moderately cross-linked network structure containing flexible segments. During the curing stage, these segments can absorb and release the internal stress generated by the difference in thermal expansion coefficients between the functional film and the metal substrate, facilitating the subsequent formation of a tough functional film. When the silane polymer is immersed in solvent oil and heated, the residual silanol groups and siloxane bonds undergo further hydrolysis-condensation reactions under the action of dibutyltin dilaurate, achieving in-situ curing and cross-linking film formation.

[0021] Furthermore, in S2-2, before soaking, nitrogen gas is continuously introduced into the flow channel at a flow rate of 50-100 mL / min for 10-15 min; during soaking, the solvent oil is first heated to 40-50℃ and soaked for 30-35 min. After soaking, it is removed and nitrogen gas is continuously introduced into the flow channel at a flow rate of 40-70 mL / min for 10-15 min; then the temperature is further increased to 60-70℃ and soaked for 20-30 min.

[0022] Explanation: At the heating temperature, the silicone resin only swells and does not dissolve rapidly. This facilitates the gradual contact of functional components such as silane oligomers and modified alumina with the metal surface of the flow channel under the swelling of the silicone resin. At this time, nitrogen gas is introduced to accelerate the removal of dissolved paraffin, prevent its re-adhesion, and free up surface adsorption sites for functional components. After heating, the silicone resin swells more and its fluidity increases, allowing the functional components to be fully released and migrate to the metal surface. The active groups of silane oligomers and tetraethyl orthosilicate condense with the hydroxyl groups on the metal surface, and at the same time, they further cross-link and solidify with each other, forming a robust siloxane functional film in situ. Heating significantly accelerates this reaction kinetics, making the film formation more complete. Nitrogen gas is introduced at this stage to continue to remove any small amount of dissolved substances that may remain, and to maintain an inert atmosphere to ensure that the moisture-sensitive tin-catalyzed condensation reaction proceeds efficiently and stably, avoiding the loosening of the film layer or the decrease in adhesion due to water vapor interference.

[0023] Compared with existing flow channel sealing and cleaning methods, the advantages of this invention are: (1) This application discloses a sealing and cleaning process for the flow channel of a 3D printed part of a rocket engine combustion chamber. The process involves vacuum injection sealing with special paraffin wax. The melting temperature of the paraffin wax is lower than the tempering temperature of the combustion chamber material. The injection process does not change the internal structure of the material and does not affect the mechanical properties and high temperature resistance of the combustion chamber. The hardness of the paraffin wax after solidification is moderate. It will not crack, fall off or shift during machining. The sealing stability is strong. It does not react chemically with CuCr1Zr alloy or 304 stainless steel and will not adhere to or corrode the surface of the workpiece. This achieves full-dimensional protection of the complex cooling flow channel of the combustion chamber and prevents machining waste and coolant from entering. The process adopts a step-by-step cleaning process of water bath and solvent dissolution. The solvent oil is a colorless, transparent and environmentally friendly solvent with moderate volatility. It does not corrode CuCr1Zr alloy or 304 stainless steel. There are no harmful substances left after dissolving the paraffin wax. It can be completely evaporated after cleaning and will not contaminate the inner wall of the flow channel. It can completely remove the sealing paraffin wax without residue or corrosion, and perfectly ensure the cleanliness of the flow channel and the integrity of the substrate.

[0024] (2) This application combines paraffin wax with silicone resin and other materials to obtain a modified sealing material. In the modified sealing material, the flake alumina, after being modified with silane, can be uniformly dispersed in the matrix formed by paraffin wax and silicone resin. Thus, the flake alumina, with its high hardness and high aspect ratio, forms a more effective anti-permeability path in the matrix, further blocking micron-sized impurities (such as machining debris and dust) from entering the flow channel during subsequent processing. Its barrier effect is far superior to that of pure paraffin wax. The addition of silicone resin to paraffin wax improves the cohesive strength and thermomechanical stability of the sealing material, making it less prone to microcracks due to vibration or temperature fluctuations in subsequent processes, thus maintaining the integrity of the seal. Moreover, silicone resin and silane oligomers have a higher viscosity than paraffin wax. The significantly higher heat distortion temperature of wax allows the sealing material to maintain its shape and strength even under the localized high temperatures generated during machining, preventing seal failure due to softening. Furthermore, during subsequent cleaning, the silicone resin and the resulting siloxane network can undergo further cross-linking and curing on the flow channel metal surface through the swelling effect of solvent oil. Components such as silane oligomers and tetraethyl orthosilicate, under the action of the catalyst dibutyltin dilaurate, form a robust siloxane polymer film in situ. This film isolates the metal substrate from direct contact with air and moisture, providing temporary corrosion protection during storage and subsequent processes. It also reduces the surface energy of the flow channel inner wall, improves media flowability, and thus enhances the subsequent cleaning effect.

[0025] (3) Based on modified sealing materials, this application utilizes solvent oil for in-situ film formation. At 40-50°C, the silicone resin only swells and does not dissolve rapidly. This facilitates the gradual contact of functional components such as silane oligomers and modified alumina with the flow channel metal surface under the movement of the silicone resin. At this time, nitrogen gas is introduced to accelerate the removal of dissolved paraffin, prevent its re-adhesion, and free up surface adsorption sites for functional components. When the temperature is raised to 60-70°C, the silicone resin network swells deeply, greatly increasing its fluidity, allowing silane oligomers and orthosilicic acid to form a film. Ethyl ester and dibutyltin dilaurate are fully released and migrate to the metal surface. The active groups of silane oligomer and tetraethyl orthosilicate condense with the hydroxyl groups on the metal surface, and at the same time, they further crosslink and solidify with each other, forming a robust siloxane functional film in situ. Heating significantly accelerates this reaction kinetics, making the film formation more complete. Nitrogen gas is introduced at this stage to continue to remove any possible residual dissolved substances and to maintain an inert atmosphere, ensuring that the moisture-sensitive tin-catalyzed condensation reaction proceeds efficiently and stably, and avoiding the loosening of the film layer or the decrease in adhesion due to water vapor interference. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the pressure drop results in Investigation 1 of this invention; Figure 2 This is a schematic diagram of the pressure drop results in Investigation 2 of this invention; Figure 3This is a schematic diagram of the adhesion strength results of Investigation 3 of this invention; Figure 4 This is a schematic diagram of the adhesion strength results of Investigation 4 of this invention; Figure 5 This is a schematic diagram of the adhesion strength results of Investigation 5 of the present invention. Detailed Implementation

[0027] To further illustrate the methods and effects of this invention, the technical solution of this invention will be clearly and completely described below in conjunction with experiments.

[0028] Example 1: A sealing and cleaning process for the flow channel of a 3D-printed rocket engine combustion chamber, comprising the following steps: S1, Sealing The flow channels of the combustion chamber are pre-cleaned: first, the flow channels are rinsed with 6MPa high-pressure pure water, and then the flow channels are purged hole by hole with 0.55MPa compressed air. After purging, the combustion chamber is placed in a drying oven and dried at 45℃ for 45 minutes. Next, place the combustion chamber into the vacuum injection equipment and seal the cavity of the vacuum injection equipment. Evacuate the vacuum injection equipment until the vacuum degree is -0.095MPa and maintain it for 12 minutes. Then, inject molten 58# fully refined paraffin wax at a temperature of 62℃ into the vacuum injection equipment so that the 58# fully refined paraffin wax immerses all the openings of the combustion chamber flow channel and injects for 25 minutes. After the injection is completed, the pressure inside the vacuum injection equipment is restored to normal pressure at a rate of 0.025 MPa / min. Then the combustion chamber is taken out and placed at room temperature to cool naturally for 55 minutes until the 58# fully refined paraffin wax is completely solidified and formed, resulting in a combustion chamber with a sealed flow channel. S2, Cleaning S2-1, Dissolve in water bath After machining the flow channel sealed combustion chamber, the machining method is as follows: turning, milling and drilling are performed on the outer wall, end face, mounting flange and docking port of the combustion chamber. After machining, the residual cutting fluid on the surface of the combustion chamber is wiped off with cotton cloth and alcohol. The machined combustion chamber was immersed in a constant temperature water bath to dissolve the 58# fully refined paraffin wax inside the combustion chamber. The temperature of the constant temperature water bath was 65℃ and the immersion time was 23 minutes. During the water bath dissolution process, the combustion chamber was shaken to ensure that the 58# fully refined paraffin wax was dissolved evenly. S2-2, Solvent oil immersion treatment The combustion chamber treated with S2-1 was removed, allowed to cool naturally to room temperature, and then immersed in 120# solvent oil at 30℃ for 28 minutes. During the immersion process, ultrasonic treatment was also applied at a frequency of 35kHz and a power of 650W. Remove the combustion chamber and use compressed air at a pressure of 0.55 MPa to blow dry the residual 120# solvent oil on the surface of the combustion chamber; S2-3, Anhydrous ethanol immersion treatment The combustion chamber treated with S2-2 was immersed in anhydrous ethanol with a purity of 99.7% at a temperature of 28°C for 8 minutes. S2-4, Rinse The combustion chamber treated with S2-3 was removed. First, the flow channel was rinsed with 6MPa high-pressure pure water for 4 minutes. After rinsing, it was immersed in pure water at 28℃ for 19 minutes. After immersion, the combustion chamber was subjected to high-pressure spraying using pure water at a pressure of 0.25MPa for 50 minutes. The spraying direction corresponded to the flow channel inlet and outlet; that is, the spray entered from the flow channel inlet and exited from the flow channel outlet. The resistivity of pure water at 25℃ is 18.2 MΩ·cm, and the pH is 7. S2-5, Purge and dry After the combustion chamber is treated with S2-4, it is removed and all flow channels are purged in reverse through compressed air. After purging, the combustion chamber is placed in a vacuum drying oven and dried at 55°C for 25 minutes. The flow channel cleaning is then complete.

[0029] Example 2: The difference between this example and Example 1 is that in S1, the flow channel is first flushed with 5.5MPa high-pressure pure water, and then the flow channel is purged hole by hole with 0.5MPa compressed air. After purging, the combustion chamber is placed in a drying oven and dried at 40°C for 30 minutes.

[0030] Example 3: The difference between this example and Example 1 is that in S1, the flow channel is first flushed with 6.5MPa high-pressure pure water, and then the flow channel is purged hole by hole with 0.6MPa compressed air. After purging, the combustion chamber is placed in a drying oven and dried at 50°C for 60 minutes.

[0031] Example 4: The difference between this example and Example 1 is that in S1, a vacuum process is performed until the vacuum degree is -0.1MPa, which is maintained for 10 minutes. Then, molten 58# fully refined paraffin wax at a temperature of 60°C is injected into the vacuum injection equipment so that the 58# fully refined paraffin wax immerses all the openings of the combustion chamber flow channel and is injected for 20 minutes.

[0032] Example 5: The difference between this example and Example 1 is that in S1, a vacuum process is performed until the vacuum degree is -0.095MPa, which is maintained for 15 minutes. Then, molten 58# fully refined paraffin wax at a temperature of 65°C is injected into the vacuum injection equipment so that the 58# fully refined paraffin wax immerses all the openings of the combustion chamber flow channel and is injected for 30 minutes.

[0033] Example 6: The difference between this example and Example 1 is that in S1, after the injection is completed, the pressure inside the vacuum injection equipment is restored to atmospheric pressure at a rate of 0.02 MPa / min, and then the combustion chamber is taken out and placed at room temperature to cool naturally for 50 minutes.

[0034] Example 7: The difference between this example and Example 1 is that in S1, after the injection is completed, the pressure inside the vacuum injection equipment is restored to atmospheric pressure at a rate of 0.03 MPa / min, and then the combustion chamber is taken out and placed at room temperature to cool naturally for 60 minutes.

[0035] Example 8: The difference between this example and Example 1 is that in S2-1, the temperature of the constant temperature water bath is 60℃ and the soaking time is 20min.

[0036] Example 9: The difference between this example and Example 1 is that in S2-1, the temperature of the constant temperature water bath is 70°C and the soaking time is 25 minutes.

[0037] Example 10: The difference between this example and Example 1 is that in S2-2, the temperature of the solvent oil is 25°C, the soaking time is 25 min, the ultrasonic frequency is 30 kHz, the power is 600 W, and compressed air with a pressure of 0.5 MPa is used for drying.

[0038] Example 11: The difference between this example and Example 1 is that in S2-2, the temperature of the solvent oil is 35°C, the soaking time is 30 min, the ultrasonic frequency is 40 kHz, the power is 700 W, and compressed air with a pressure of 0.6 MPa is used for drying.

[0039] Example 12: The difference between this example and Example 1 is that in S2-3, the temperature of anhydrous ethanol is 25°C and the soaking time is 5 minutes.

[0040] Example 13: The difference between this example and Example 1 is that in S2-3, the temperature of anhydrous ethanol is 30°C and the soaking time is 10 min.

[0041] Example 14: The difference between this example and Example 1 is that in S2-4, the flow channel is first rinsed with 5.5MPa high-pressure pure water for 3 minutes. After rinsing, it is then soaked in pure water at a temperature of 25°C for 18 minutes. The pressure of the high-pressure spray is 0.2MPa for 45 minutes, and the pH of the pure water is 6.5.

[0042] Example 15: The difference between this example and Example 1 is that in S2-4, the flow channel is first rinsed with 6.5MPa high-pressure pure water for 5 minutes. After rinsing, it is then soaked in pure water at a temperature of 30°C for 20 minutes. The pressure of the high-pressure spray is 0.3MPa for 60 minutes, and the pH of the pure water is 7.5.

[0043] Example 16: The difference between this example and Example 1 is that in S2-5, the product is dried at 50°C for 20 minutes.

[0044] Example 17: The difference between this example and Example 1 is that in S2-5, drying is carried out at 60°C for 30 minutes.

[0045] Example 18: This example differs from Example 1 in that, in S1, the paraffin wax is modified paraffin wax (melting temperature is 80℃), and the preparation method of the modified paraffin wax is as follows: 58# fully refined paraffin wax and organosilicon resin were mixed and stirred at 75°C and 465 rpm in a mass ratio of 3:3 to obtain the first mixture; Under nitrogen protection, 1 g of alumina and 15 mL of isoparaffin were stirred and mixed at 105 °C for 1.2 h. Then, 0.1 g of octadecyltrimethoxysilane was added and the mixture was heated to 155 °C and refluxed for 3.5 h. The resulting reaction solution was cooled to 55 °C and centrifuged at 8000 rpm for 10 min. The solid obtained by centrifugation was washed twice with toluene and twice with anhydrous ethanol. It was then dried under vacuum at 80 °C and 0.1 MPa for 10 h to obtain modified alumina. The first mixture and modified alumina were subjected to a mass ratio of 4:1, and were first sheared at 3200 rpm for 35 min, and then ultrasonically treated at 400 W for 13 min to obtain the second mixture. Add silane oligomer to the second mixture, stir at 250 rpm for 5.5 min, then add tetraethyl orthosilicate and dibutyltin dilaurate in sequence, and continue stirring for 12 min. The mass ratio of the second mixture: silane oligomer: tetraethyl orthosilicate: dibutyltin dilaurate is 100:18:5:0.8 to obtain modified paraffin. The preparation method of silane oligomers is as follows: Isopropanol and deionized water were mixed at a volume ratio of 1:1.1 to obtain a mixture. Then, p-toluenesulfonic acid was added to the mixture and stirred until completely dissolved. Then, methyltrimethoxysilane and diphenyldimethoxysilane were added sequentially to obtain a reaction system. The ratio of mixture:p-toluenesulfonic acid:methyltrimethoxysilane:dimethyldimethoxysilane was 100ml:0.1g:18g:7.5g. The reaction system was heated to 68°C and stirred for 3.8 hours. After the reaction was completed, the reaction system was cooled to 38°C and hexamethyldisilazane was added. The mass ratio of the reaction system to hexamethyldisilazane was 53:20. The reaction was stirred for another 1.2 hours to obtain the reaction solution. After cooling the reaction solution to room temperature, wash the reaction solution twice with saturated sodium bicarbonate aqueous solution to obtain an organic phase. Add 19g of anhydrous sodium sulfate to 150mL of the organic phase and react for 25min. After the reaction is complete, filter the solution and evaporate the filtrate at 55℃ and -0.098 MPa to remove the solvent, byproduct methanol and excess water. Then, dry the solution under vacuum at 85℃ and -0.1 MPa for 5h to obtain silane oligomers.

[0046] Example 19: The difference between this example and Example 18 is that 58# fully refined paraffin wax and organosilicon resin are mixed and stirred at 70°C and 450 rpm in a mass ratio of 2.5:3 to obtain the first mixture.

[0047] Example 20: This example differs from Example 18 in that 58# fully refined paraffin wax and organosilicon resin are mixed and stirred at 80°C and 480 rpm in a mass ratio of 4:3 to obtain the first mixture.

[0048] Example 21: The difference between this example and Example 18 is that 1g of alumina and 10mL of isoparaffin were stirred and mixed at 100°C for 1h, then 0.1g of octadecyltrimethoxysilane was added and the mixture was heated to 150°C and refluxed for 3h. The resulting reaction solution was cooled to 50°C and then centrifuged, washed and dried in sequence to obtain modified alumina.

[0049] Example 22: This example differs from Example 18 in that 1g of alumina and 120mL of isoparaffin were stirred and mixed at 110°C for 1.5h, then 0.1g of octadecyltrimethoxysilane was added and the mixture was heated to 160°C and refluxed for 4h. The resulting reaction solution was cooled to 60°C and then centrifuged, washed, and dried in sequence to obtain modified alumina.

[0050] Example 23: This example differs from Example 18 in that the first mixture and modified alumina are sheared at 3000 rpm for 30 min at a mass ratio of 3.5:1, and then ultrasonically treated at 400 W for 10 min to obtain the second mixture.

[0051] Example 24: This example differs from Example 18 in that the first mixture and modified alumina are sheared at 3500 rpm for 40 min at a mass ratio of 4.5:1, and then ultrasonically treated at 400 W for 15 min to obtain the second mixture.

[0052] Example 25: This example differs from Example 18 in that a silane oligomer is added to the second mixture, and the mixture is stirred at 200 rpm for 5 minutes. Then, tetraethyl orthosilicate and dibutyltin dilaurate are added sequentially, and the mixture is stirred for another 10 minutes. The mass ratio of the second mixture: silane oligomer: tetraethyl orthosilicate: dibutyltin dilaurate is 100:18:5:0.5, resulting in modified paraffin.

[0053] Example 26: This example differs from Example 18 in that a silane oligomer is added to the second mixture, and the mixture is stirred at 300 rpm for 6 minutes. Then, tetraethyl orthosilicate and dibutyltin dilaurate are added sequentially, and the mixture is stirred for another 15 minutes. The mass ratio of the second mixture: silane oligomer: tetraethyl orthosilicate: dibutyltin dilaurate is 100:18:5:1, resulting in modified paraffin.

[0054] Example 27: The difference between this example and Example 18 is that isopropanol and deionized water are mixed in a volume ratio of 1:1 to obtain a mixture. The ratio of the mixture to p-toluenesulfonic acid to methyltrimethoxysilane to dimethyldimethoxysilane is 100ml:0.1g:18g:7g.

[0055] Example 28: The difference between this example and Example 18 is that isopropanol and deionized water are mixed in a volume ratio of 1:1.2 to obtain a mixture. The ratio of the mixture to p-toluenesulfonic acid to methyltrimethoxysilane to dimethyldimethoxysilane is 100ml:0.1g:18g:8g.

[0056] Example 29: The difference between this example and Example 18 is that the reaction system was heated to 65°C and stirred for 3.5 hours. After the reaction was completed, the reaction system was cooled to 35°C and hexamethyldisilazane was added. The mass ratio of the reaction system to hexamethyldisilazane was 50:20. The reaction was stirred for another hour to obtain the reaction solution.

[0057] Example 30: The difference between this example and Example 18 is that the reaction system was heated to 70°C and stirred for 4 hours. After the reaction was completed, the reaction system was cooled to 40°C and hexamethyldisilazane was added. The mass ratio of the reaction system to hexamethyldisilazane was 55:20. The reaction was stirred for another 1.5 hours to obtain the reaction solution.

[0058] Example 31: This example differs from Example 18 in that, in S2-2, before soaking, nitrogen gas is continuously introduced into the flow channel at a flow rate of 75 mL / min for 12 minutes; during soaking, the 120# solvent oil is first heated to 45°C and soaked for 32 minutes. After soaking, it is removed and nitrogen gas is continuously introduced into the flow channel at a flow rate of 55 mL / min for 12 minutes; then the temperature is further increased to 65°C and soaked for 25 minutes.

[0059] Example 32: This example differs from Example 31 in that, before soaking, nitrogen gas is continuously introduced into the flow channel at a flow rate of 50 mL / min for 10 min; during soaking, the 120# solvent oil is first heated to 40°C and soaked for 30 min. After soaking, it is removed and nitrogen gas is continuously introduced into the flow channel at a flow rate of 40 mL / min for 10 min; then the temperature is further increased to 60°C and soaked for 20 min.

[0060] Example 33: This example differs from Example 31 in that, before soaking, nitrogen gas is continuously introduced into the flow channel at a flow rate of 100 mL / min for 15 min; during soaking, the 120# solvent oil is first heated to 50°C and soaked for 35 min. After soaking, it is removed, and nitrogen gas is continuously introduced into the flow channel at a flow rate of 70 mL / min for 15 min; then the temperature is further increased to 70°C and soaked for 30 min.

[0061] Experimental Example: The description of this experimental example is based on the scheme described in Example 1, and aims to illustrate the practical application effect of the present invention.

[0062] The cleanliness of the flow channels after cleaning in each embodiment of this application was tested using an endoscope with a diameter of 0.8 mm. The test showed that there was no paraffin residue, no impurities, and no scratches on the inner wall of the flow channels, indicating that the cleaning effect of this application is excellent.

[0063] The flow channel patency was tested by a liquid flow test. The test parameters included: the inlet pressure of the liquid flow was 8 MPa, the flow velocity was 25 m / s, and the outlet pressure was measured at the same time. The pressure drop was calculated (pressure drop = inlet pressure - outlet pressure). If the pressure drop was ≤ 5, it proved that the flow channel was patency, that is, the cleaning effect of this application was excellent.

[0064] At the same time, the surface condition of the workpiece was tested. The combustion chamber after cleaning was free of corrosion and performance damage, and the test was qualified, which means that the cleaning effect of this application is excellent.

[0065] Inquiry 1: Investigate the effect of sealing methods on the unobstructed flow of the channel.

[0066] The difference between Comparative Example 1 and Example 1 is that modeling clay was used instead of 58# fully refined paraffin wax for sealing; The difference between Comparative Example 2 and Example 1 is that sealing tape was used instead of 58# fully refined paraffin wax for sealing; The difference between Comparative Example 3 and Example 1 is that epoxy resin was used instead of 58# fully refined paraffin wax for sealing; like Figure 1 As shown, the putty in Comparative Example 1 can only seal open flow channels and cannot adapt to complex, tortuous, and porous internal flow channels, resulting in dead zones in the seal; the sealing tape in Comparative Example 2 has poor adhesion and is easily detached due to machining vibration, leading to protection failure; the resin in Comparative Example 3 has high curing strength after sealing, making it difficult to completely remove later, and residual resin will contaminate the flow channel, and the removal process can easily scratch the inner wall of the flow channel; therefore, the flow channel pressure drop of Comparative Examples 1 to 3 is significantly increased compared to Examples 1 to 7, resulting in poor flow channel unobstructedness; Comparing Examples 1 to 7, it can be seen that if the pretreatment parameters are too small or too large, the parameters of concern are too small or too large, or the cooling and curing parameters are too small or too large, the flow channel pressure drop will increase. Therefore, from a comprehensive perspective, the parameter effect of Example 1 is relatively better.

[0067] Inquiry 2: Investigate the impact of cleaning methods on the smoothness of the flow channel.

[0068] The difference between Comparative Example 4 and Example 1 is that the cleaning process only involves high-pressure water rinsing and blowing dry. like Figure 2 As shown, the high-pressure water jetting and mechanical purging in Comparative Example 4 could not thoroughly clean the impurities and blockage residues in the complex flow channels, and there was no targeted gentle cleaning process, which could easily damage the surface of materials such as CuCr1Zr alloy and 304 stainless steel; therefore, the flow channel pressure drop in Comparative Example 4 was significantly increased compared to Examples 1 to 17, and the flow channel unobstructedness was poor. Comparing Examples 8 to 17, it can be seen that excessively small parameters for water bath dissolution, solvent cleaning, alcohol cleaning, pure water cleaning, and purging and drying will all increase the flow channel pressure drop. Among them, the pressure drop of Examples 8 and 15 is comparable to that of Example 1, but the required parameters are larger. Therefore, from an economic point of view, the parameter effect of Example 1 is relatively better.

[0069] Compared to Example 1, the modified paraffin prepared in Examples 18 to 33 forms a functional film on the flow channel during the sealing and cleaning process, which can provide corrosion-resistant and heat-resistant protection for the flow channel. The relevant performance tests are as follows.

[0070] The flow channel patency was tested by a liquid flow test. The test parameters included: the inlet pressure of the liquid flow was 20 MPa, the flow velocity was 25 m / s, and the outlet pressure was measured at the same time. The pressure drop was calculated (pressure drop = inlet pressure - outlet pressure). The average pressure drop of each embodiment was ≤4.5, which proved that the cleaning effect could still be maintained under the action of forming a functional membrane.

[0071] According to ASTM B117, a neutral salt spray test was conducted, and it was found that after 168 hours, the functional film formed on the flow channel after cleaning had a corrosion grade of ≥9, which proved its good corrosion resistance.

[0072] A static high-temperature exposure test was then conducted. The thermal stability of each embodiment under this test was tested by the pull-out method, and the adhesion strength of the functional film after 24 hours was detected.

[0073] Inquiry 3: Investigate the effect of modified paraffin on flow channel performance.

[0074] like Figure 3 As shown, comparing Examples 18 to 26, it can be seen that if the preparation parameters of the first mixture are too small or too large, the preparation parameters of the modified alumina are too small or too large, the preparation parameters of the second mixture are too small or too large, and the preparation parameters of the modified paraffin are too small or too large, the adhesion strength of the functional film will be reduced. Therefore, from a comprehensive point of view, the parameter effect of Example 18 is relatively better.

[0075] Investigation 4: Investigate the effect of silane oligomers on flow channel performance.

[0076] like Figure 4 As shown, comparing Examples 27 to 30, it can be seen that if the preparation parameters of the reaction system are too small or too large, or if the preparation parameters of the reaction solution are too small or too large, the adhesion strength of the functional film will be reduced. Therefore, from a comprehensive point of view, the parameters of Example 18 are relatively better.

[0077] Investigation 5: Investigate the impact of improving the cleaning method based on modified paraffin on the performance of the flow channel.

[0078] like Figure 5 As shown, by comparing Examples 18 and 31-33, it can be seen that under the sealing of modified paraffin, the solvent cleaning of S2-2 is further enhanced, and the catalytic effect of 120# solvent oil on the functional membrane is utilized to enhance the in-situ film formation effect of the functional membrane. Therefore, Examples 31-33 further enhance the performance of the functional membrane based on Example 18. Comparing Examples 31 to 33, it can be seen that both excessively small and excessively large cleaning and ventilation parameters will reduce the adhesion strength of the functional membrane. Therefore, from a comprehensive perspective, the parameters of Example 31 are relatively better.

Claims

1. A sealing and cleaning process for the flow channel of a 3D-printed rocket engine combustion chamber, characterized in that, Includes the following steps: S1, Sealing The flow channels of the combustion chamber are pre-cleaned, then the combustion chamber is placed into the vacuum injection equipment and the cavity of the vacuum injection equipment is sealed. The vacuum injection equipment is evacuated until the vacuum degree is -0.1~-0.095MPa, and maintained for 10~15min. Then, molten paraffin is injected into the vacuum injection equipment so that the paraffin immerses all the openings of the flow channels of the combustion chamber. The injection lasts for 20~30min. After the injection is completed, the pressure inside the vacuum injection equipment is restored to atmospheric pressure at a rate of 0.02~0.03MPa / min. Then, the combustion chamber is removed and allowed to cool naturally at room temperature for 50~60 minutes to obtain a combustion chamber with sealed flow channels. S2, Cleaning S2-1, Dissolve in water bath After the flow channel-sealed combustion chamber is machined, it is immersed in a constant temperature water bath to dissolve the paraffin inside the combustion chamber. The temperature of the constant temperature water bath is 60~70℃ and the immersion time is 20~25min. S2-2, Solvent oil immersion treatment Remove the combustion chamber treated with S2-1, allow it to cool naturally to room temperature, and then immerse it in solvent oil at a temperature of 25~70℃ for 25~65 minutes. Then the combustion chamber is removed, and the residual solvent oil on the surface of the combustion chamber is dried using compressed air at a pressure of 0.5~0.6MPa; S2-3, Anhydrous ethanol immersion treatment The combustion chamber treated with S2-2 was immersed in anhydrous ethanol at a temperature of 25-30°C for 5-10 minutes. S2-4, Rinse Take out the combustion chamber after S2-3 treatment, first rinse the flow channel with high-pressure pure water of 5.5~6.5MPa for 3~5 minutes, and then soak it in pure water at a temperature of 25~30℃ for 18~20 minutes. S2-5, Purge and dry Remove the combustion chamber after S2-4 treatment, and use compressed air to purge all flow channels in reverse through each hole. After purging, place the combustion chamber in a vacuum drying oven and dry it at 50~60℃ for 20~30 minutes to complete the flow channel cleaning.

2. The sealing and cleaning process for the flow channel of a 3D-printed rocket engine combustion chamber as described in claim 1, characterized in that, In S1, the method for pre-cleaning the flow channels of the combustion chamber is as follows: First, flush the flow channel with high-pressure pure water at 5.5~6.5MPa, then purge the flow channel hole by hole with compressed air at 0.5~0.6MPa. After purging, place the combustion chamber in a drying oven and dry it at 40~50℃ for 30~60 minutes.

3. The sealing and cleaning process for the flow channel of a 3D-printed rocket engine combustion chamber as described in claim 1, characterized in that, In S2-2, ultrasonic treatment is also applied during the soaking process, with an ultrasonic frequency of 30~40kHz and a power of 600~700W.

4. The sealing and cleaning process for the flow channel of a 3D-printed rocket engine combustion chamber as described in claim 1, characterized in that, In S2-4, after soaking, the combustion chamber is subjected to high-pressure spraying. Pure water is used for high-pressure spraying, the pressure is 0.2~0.3MPa, the time is 45~60min, and the spraying direction corresponds to the inlet and outlet of the flow channel.

5. The sealing and cleaning process for the flow channel of a 3D-printed rocket engine combustion chamber as described in claim 1, characterized in that, In S2-4, the resistivity of the purified water at 25℃ is ≥18.2MΩ·cm, and the pH is 6.5~7.

5.

6. The sealing and cleaning process for the flow channel of a 3D-printed rocket engine combustion chamber as described in claim 1, characterized in that, In S2-1, the machining method is as follows: the outer wall, end face, mounting flange, and docking port of the combustion chamber are turned, milled, and drilled. After machining, the residual cutting fluid on the surface of the combustion chamber is wiped off with cotton cloth and alcohol. The machining is then completed.

7. The sealing and cleaning process for the flow channel of a 3D-printed rocket engine combustion chamber as described in claim 1, characterized in that, In S1, the paraffin wax is modified paraffin wax, and the preparation method of the modified paraffin wax is as follows: Paraffin wax and silicone resin were mixed and stirred at a mass ratio of 2.5 to 4:3 at 70 to 80°C and 450 to 480 rpm to obtain the first mixture. Under nitrogen protection, 1g of alumina and 10-20mL of isoparaffin were stirred and mixed at 100-110℃ for 1-1.5h, then 0.1g of octadecyltrimethoxysilane was added and the mixture was heated to 150-160℃ and refluxed for 3-4h. The resulting reaction solution was cooled to 50-60℃ and then centrifuged, washed and dried to obtain modified alumina. The first mixture and modified alumina were subjected to a mass ratio of 3.5 to 4.5:1, and were first sheared at 3000 to 3500 rpm for 30 to 40 minutes, and then ultrasonically treated for 10 to 15 minutes to obtain the second mixture. Add silane oligomer to the second mixture, stir at 200-300 rpm for 5-6 minutes, then add tetraethyl orthosilicate and dibutyltin dilaurate in sequence, and continue stirring for 10-15 minutes. The mass ratio of the second mixture: silane oligomer: tetraethyl orthosilicate: dibutyltin dilaurate is 100:18:5:0.5-1, to obtain modified paraffin.

8. The sealing and cleaning process for the flow channel of a 3D-printed rocket engine combustion chamber as described in claim 7, characterized in that, The method for preparing the silane oligomer is as follows: Isopropanol and deionized water were mixed at a volume ratio of 1:1 to 1.2 to obtain a mixture. Then, p-toluenesulfonic acid was added to the mixture and stirred until completely dissolved. Then, methyltrimethoxysilane and diphenyldimethoxysilane were added sequentially to obtain a reaction system. The ratio of mixture:p-toluenesulfonic acid:methyltrimethoxysilane:dimethyldimethoxysilane was 100mL:0.1g:18g:7~8g. The reaction system was heated to 65-70°C and stirred for 3.5-4 hours. After the reaction was completed, the reaction system was cooled to 35-40°C and hexamethyldisilazane was added. The mass ratio of the reaction system to hexamethyldisilazane was 50-55:

20. The reaction was stirred for another 1-1.5 hours to obtain the reaction solution. After cooling the reaction solution to room temperature, wash it to obtain an organic phase. Add 18-20g of anhydrous sodium sulfate to 150mL of the organic phase and react for 20-30min. After the reaction is complete, filter the solution, evaporate the filtrate by rotary evaporation, and then dry it under vacuum to obtain silane oligomers.

9. The sealing and cleaning process for the flow channel of a 3D-printed rocket engine combustion chamber as described in claim 7, characterized in that, In S2-2, before soaking, nitrogen gas is continuously introduced into the flow channel at a flow rate of 50-100 mL / min for 10-15 min. During soaking, the solvent oil is first heated to 40-50℃ and soaked for 30-35 min. After soaking, it is removed and nitrogen gas is continuously introduced into the flow channel at a flow rate of 40-70 mL / min for 10-15 min. Then, the temperature is further increased to 60-70℃ and soaked for 20-30 min.

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