High-energy small coated grain and forming method thereof

Abstract

The invention belongs to the technical field of solid rocket engine manufacturing, and particularly relates to a high-energy small coated grain and a forming method thereof.The high-energy small coated grain comprises a grain body and a coating sleeve wrapping the outer side of the grain body; the coating sleeve is an annular sleeve with one closed end, and the coating sleeve has ablation resistance and is used for preventing the coating sleeve from burning and chipping in the grain burning process; the coating sleeve comprises 100-150 parts of liquid silicone rubber, 1-2 parts of aramid fiber, 5-10 parts of kaolin, 15-20 parts of ablation-resistant resin, 10-20 parts of fumed silica and 2 parts of a curing agent; the coated grain comprises a grain body and a coating sleeve wrapping the outer side of the grain body, and a first combustion hole and a second combustion hole are formed in the end, away from the end wrapped by the coating sleeve, of the grain body and the side wall of the grain body correspondingly and used for increasing the combustion face of the coated grain body through simultaneous combustion of the first combustion hole and the second combustion hole; the combustion speed is increased under the condition of a certain dose, higher energy output at the moment of combustion is achieved, and the requirement of a rocket engine for high energy is met.

Description

Technical Field

[0001] The invention belongs to the technical field of solid rocket engine manufacturing, and in particular relates to a high-energy small-sized coated grain column of a solid rocket engine and a molding method thereof. Background Art

[0002] In the field of solid rocket engine technology, small coated propellants play an indispensable role. As a key component of the solid rocket engine igniter or gas generator, they release specific energy or generate power through the combustion process, thereby driving the engine to complete a series of work processes.

[0003] Traditional small coated grains use a coating sleeve to wrap the side part of the spiral-pressed propellant with a coating material, leaving only one end as the starting combustion surface. In this structure, the coating sleeve fits tightly to the side of the propellant, protecting the propellant and limiting the combustion area. Usually, only one end is reserved as the starting combustion surface, which makes the combustion process of the propellant start from the reserved end and gradually carry out the combustion reaction according to the pre-designed coating profile; however, when the engine is working, since the combustion surface of the small coated grain is mainly concentrated at the reserved starting end and gradually expands along the coating profile, this combustion method generally has a low propellant combustion speed. Under limited drug quantity conditions, the energy released in a short time is also relatively small. With the development of rocket technology towards higher performance and more special application scenarios, more stringent requirements are put forward for energy acquisition, and it is necessary to achieve an instantaneous burst of greater energy under limited drug quantity; at the same time, the traditional small coated grain coating materials and their corresponding coating processes have many problems in the face of achieving instantaneous bursts of high energy requirements. On the one hand, traditional coating materials have poor ablation resistance. When the burning speed of the grain is greatly increased, it is difficult to resist the impact erosion of high temperature, high pressure and high-speed gas flow, and it is easy to cause burning chunks. Once these chunks enter the throat of the nozzle, it is very likely to cause throat blockage, which will seriously affect the normal operation of the product and may even cause engine failure, endangering the safety of the rocket launch mission. On the other hand, the existing coating process is insufficient in accurately controlling the shape and size of the combustion surface of the grain, making it difficult to ensure stability and uniformity during the combustion process at high burning speeds, resulting in the inability to efficiently release and utilize energy.

[0004] Therefore, it is necessary to design a coated drug column and a molding method thereof that can improve the above problems. Summary of the invention

[0005] In order to solve the problems of the prior art, the present invention provides a high-energy small coated grain column, comprising a grain column and a coating sleeve wrapped around the outside of the grain column; The coating sleeve is an annular sleeve with one end closed, and the coating sleeve has ablation resistance and is used to prevent the coating sleeve from burning off during the combustion of the charge; The coating sleeve comprises 100-150 parts of liquid silicone rubber, 1-2 parts of aramid fiber, 5-10 parts of kaolin, 15-20 parts of ablation-resistant resin, 10-20 parts of fumed silica and 2 parts of curing agent; the premix of 100-150 parts of liquid silicone rubber, 1-2 parts of aramid fiber, 5-10 parts of kaolin, 15-20 parts of ablation-resistant resin, 10-20 parts of fumed silica and 2 parts of curing agent is loaded into a rectangular vertical mold for compression molding; The end of the charge away from being wrapped by the coating sleeve and the side wall thereof are respectively provided with a first combustion hole and a second combustion hole, which are used to increase the combustion surface of the coated charge through simultaneous combustion of the first combustion hole and the second combustion hole.

[0006] Furthermore, the aramid fiber has a length of 2-3 mm.

[0007] Furthermore, the first combustion hole is a circular inner hole, the second combustion hole is a vertical long hole, the circular inner hole is arranged at the center of one end of the charge, and the vertical long hole is arranged on the side wall of the charge.

[0008] Furthermore, the rectangular vertical mold includes an inner ring, which is a petal structure for facilitating demoulding of the solidified drug column and the covering sleeve, and a protrusion is provided on the inner wall of the inner ring for forming vertical long holes on the side wall of the drug column.

[0009] Furthermore, a polytetrafluoroethylene coating is provided on the inner wall of the inner ring, and the thickness of the polytetrafluoroethylene coating is 0.01-0.02 mm, which is used to prevent the covering sleeve from adhering to the inner wall of the inner ring and affecting demoulding.

[0010] A method for forming a high-energy small coated drug column comprises the following steps: S1, grain surface treatment, first brush the surface treatment agent on the side wall of the grain, and then dry it for at least 2 hours; S2, assembling, putting the drug column into the rectangular vertical mold, wherein the rectangular vertical mold is composed of an upper mold, an inner sleeve ring, a guide sleeve and a lower mold. During assembly, first put the drug column on the upper mold, then put the guide sleeve on the upper mold, put the inner sleeve ring into the guide sleeve and assemble it with the lower mold; put the prepared coating sleeve into the inner sleeve ring; then put the upper mold into the inner sleeve ring and position it with the lower mold, finally clean up the excess coating sleeve, and finally clamp the rectangular vertical mold with a U-shaped clamp; S3, curing, placing the assembled rectangular vertical mold and the medicine column in an explosion-proof vacuum oven, and curing the coating sleeve and the medicine column into an integral body under vacuum conditions; S4, demoulding. After curing is completed, the grain is taken out from the rectangular vertical mold and allowed to stand at room temperature. The components of the rectangular vertical mold are disassembled in sequence, the inner ring and the grain are separated, and the excess coating on the surface of the vertical strip holes on the grain flash and its side wall is cleaned; S5, inspection, check the size of the coated grain according to the design drawing, whether the shape and size of the combustion surface are accurate, whether the appearance of the coated grain is intact, and perform non-destructive testing at the same time to confirm whether there is any debonding phenomenon on the interface.

[0011] Furthermore, the surface treatment agent is a coupling agent, which is used to enhance the bonding effect between the drug column and the coating sleeve.

[0012] Further, in step S3, the temperature is controlled at 40°C-50°C under vacuum conditions and the curing is performed for 4h-6h, so that the coating sleeve and the drug column are integrally cured and formed; Beneficial effects of the present invention: (1) The coated grain of the present invention comprises a grain and a coating sleeve wrapped around the outside of the grain, and a first combustion hole and a second combustion hole are respectively arranged on the end of the grain away from being wrapped by the coating sleeve and on the side wall thereof, so as to increase the combustion surface of the coated grain by burning the first combustion hole and the second combustion hole simultaneously; the combustion speed is increased under the condition of a certain amount of grain, and a higher energy output is achieved at the moment of combustion, effectively meeting the high energy demand of the rocket engine; a rectangular vertical mold is arranged to ensure the molding accuracy of the grain, an inner sleeve ring is arranged as a petal structure and a polytetrafluoroethylene coating is arranged on the inner wall of the inner sleeve ring, which effectively solves the demoulding problem of the coated grain and improves the production efficiency and the quality of the grain; the outer side of the grain is wrapped with the coating sleeve, so that the grain has good ablation resistance, and can effectively prevent the coating layer from burning and blocking the throat during the combustion of the grain; (2) In the process of forming the high-energy small coated grain of the present invention, each link from surface treatment of the grain to assembly, curing and demoulding is closely coordinated to ensure the precise size of the coated grain and the stable shape and size of its combustion surface, so that the grain is stable and uniform during combustion at a high burning rate, and the energy of the grain is efficiently released and utilized. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic diagram of the structure of the coated drug column of the present invention; Figure 2 A schematic diagram of the structure of a rectangular vertical mold of the present invention; Reference numerals: In the figure: 1-upper die, 2-inner ring, 3-guide sleeve, 4-lower die. DETAILED DESCRIPTION

[0014] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0015] See also Figure 1-2 The present invention provides a high-energy small-sized coated grain column, comprising a grain column and a coating sleeve wrapped around the outside of the grain column; The coating sleeve is an annular sleeve with one end closed, and the coating sleeve has ablation resistance and is used to prevent the coating sleeve from burning off during the combustion of the charge; The coating sleeve comprises 100-150 parts of liquid silicone rubber, 1-2 parts of aramid fiber, 5-10 parts of kaolin, 15-20 parts of ablation-resistant resin, 10-20 parts of fumed silica and 2 parts of curing agent; the premix of 100-150 parts of liquid silicone rubber, 1-2 parts of aramid fiber, 5-10 parts of kaolin, 15-20 parts of ablation-resistant resin, 10-20 parts of fumed silica and 2 parts of curing agent is loaded into a rectangular vertical mold for compression molding; The end of the charge away from being wrapped by the coating sleeve and the side wall thereof are respectively provided with a first combustion hole and a second combustion hole, which are used to increase the combustion surface of the coated charge by burning the first combustion hole and the second combustion hole simultaneously; Furthermore, the aramid fiber has a length of 2-3 mm.

[0016] Furthermore, the first combustion hole is a circular inner hole, the second combustion hole is a vertical long hole, the circular inner hole is arranged at the center of one end of the charge, and the vertical long hole is arranged on the side wall of the charge.

[0017] Furthermore, the rectangular vertical mold includes an inner ring, which is a petal structure for facilitating demoulding of the solidified drug column and the covering sleeve, and a protrusion is provided on the inner wall of the inner ring for forming a vertical long hole on the side wall of the drug column; Furthermore, a polytetrafluoroethylene coating is provided on the inner wall of the inner ring, and the thickness of the polytetrafluoroethylene coating is 0.01-0.02 mm, which is used to prevent the covering sleeve from adhering to the inner wall of the inner ring and affecting demoulding; A method for forming a high-energy small coated drug column comprises the following steps: S1, grain surface treatment, first brush the surface treatment agent on the side wall of the grain, and then dry it for at least 2 hours; S2, assembling, putting the drug column into the rectangular vertical mold, wherein the rectangular vertical mold is composed of an upper mold, an inner sleeve ring, a guide sleeve and a lower mold. During assembly, first put the drug column on the upper mold, then put the guide sleeve on the upper mold, put the inner sleeve ring into the guide sleeve and assemble it with the lower mold; put the prepared coating sleeve into the inner sleeve ring; then put the upper mold into the inner sleeve ring and position it with the lower mold, finally clean up the excess coating sleeve, and finally clamp the rectangular vertical mold with a U-shaped clamp; S3, curing, placing the assembled rectangular vertical mold and the medicine column in an explosion-proof vacuum oven, and curing the coating sleeve and the medicine column into an integral body under vacuum conditions; S4, demoulding. After curing is completed, the grain is taken out from the rectangular vertical mold and allowed to stand at room temperature. The components of the rectangular vertical mold are disassembled in sequence, the inner ring and the grain are separated, and the excess coating on the surface of the vertical strip holes on the grain flash and its side wall is cleaned; S5, inspection, check the size of the coated grain according to the design drawing, whether the shape and size of the combustion surface are accurate, whether the appearance of the coated grain is intact, and perform non-destructive testing at the same time to confirm whether there is any debonding phenomenon on the interface.

[0018] Furthermore, the surface treatment agent is a coupling agent, which is used to enhance the bonding effect between the drug column and the coating sleeve.

[0019] Further, in step S3, the temperature is controlled at 40°C-50°C under vacuum conditions and the curing is performed for 4h-6h, so that the coating sleeve and the drug column are integrally cured and formed; Embodiment 1, according to Figure 1 The structure of the coated grain column is shown in the figure. The forming process of the high-energy small coated grain column is as follows: Preparation of the coating: pre-mix 100 parts of liquid silicone rubber, 1 part of aramid fiber (length 2-3 mm), 5 parts of kaolin, 15 parts of ablation-resistant resin and 10 parts of fumed silica, evacuate for 1 hour after pre-mixing evenly, then add 2 parts of curing agent and stir for 0.5 hours before use; Among them, the length of the aramid fiber is 2-3mm; it plays a reinforcing role in the coating sleeve, improving the overall strength and ablation resistance of the coating sleeve; the curing agent is an organic tin compound, and the organic tin compound is dibutyltin dilaurate or stannous octoate; the ablation-resistant resin is a resin material that maintains its structure and performance unchanged under extremely high temperature environments; the ablation-resistant resin is an organic-inorganic hybrid resin composed of organic components and inorganic components, and the organic component is mainly prepared by reacting polycaprolactone polyol, succinic anhydride and aminopropyltriethoxysilane; the inorganic component is a silane-modified sol. The inorganic component is combined with the organic component by chemical bonds to form a stable interpenetrating network structure; the liquid silicone rubber is a high-performance silicone material, and the liquid silicone rubber is a two-component liquid silicone rubber; Grain surface treatment: brush the surface treatment agent on the side wall of the screw-pressed grain, and then dry it for at least 2 hours to ensure that the surface treatment agent can fully play its role and lay a good foundation for subsequent curing and molding; the surface treatment agent is a coupling agent, which is used to enhance the bonding effect between the grain and the coating sleeve; Assemble, put the medicine column into the rectangular vertical mold, wherein the rectangular vertical mold is composed of an upper mold 1, an inner sleeve ring 2, a guide sleeve 3 and a lower mold 4, and the inner sleeve ring 2 is a petal structure, consisting of 2-4 petals; to facilitate demoulding, the inner wall of the inner sleeve ring 2 is provided with a protrusion for forming the vertical long strip hole on the side wall of the medicine column; during assembly, first put the medicine column on the upper mold 1, then put the guide sleeve 3 on the upper mold 1, and then put the inner sleeve ring 2 into the guide sleeve 3 and assemble it with the lower mold 4; finally, put the prepared coating sleeve into the inner sleeve ring 2; then put the upper mold 1 into the inner sleeve ring 2 and position it with the lower mold 4, clean up the excess coating sleeve, and finally clamp the rectangular vertical mold with a U-shaped clamp to ensure that the components are closely matched and the molding accuracy of the medicine column is guaranteed; Among them, the design of rectangular vertical mold, reference Figure 2 Design the rectangular vertical mold; Curing: Place the assembled rectangular vertical mold and the drug column in an explosion-proof vacuum oven. Under vacuum conditions, control the temperature at 40°C and cure for 4 hours to solidify the coating and drug column into an integrated whole, ensure the stability of the drug column structure, and ensure that the coating and drug column are tightly combined, thus providing guarantee for the performance of the drug column; After demoulding and curing, take out the powder column and let it stand at room temperature, disassemble the U-shaped clamp, lower mold 4, upper mold 1, guide sleeve 3 and inner ring 2 in order, separate the inner ring 2 from the powder column, clean the excess coating sleeve on the surface of the vertical long holes on the flash of the powder column and its side wall, and strictly follow the safety operation requirements of pyrotechnics to ensure the safety and reliability of the production process and the appearance quality of the powder column; wherein, the inner wall of the inner ring 2 is sprayed with a polytetrafluoroethylene coating, the thickness of the polytetrafluoroethylene coating is 0.01-0.02mm, which is used to prevent the coating sleeve from adhering to the inner wall of the inner ring 2 and affecting demoulding; Inspection: Check the size of the coated powder column according to the dimensions on the design drawings, whether the shape and size of the combustion surface are accurate, and whether the appearance of the coated powder column is intact. At the same time, perform non-destructive testing to confirm whether there is any debonding phenomenon on the interface. The qualified products will be packaged and stored according to the requirements of pyrotechnics to ensure the reliable quality of the coated powder column put into use.

[0020] Embodiment 2, according to Figure 1 The structure of the coated grain column is shown in the figure. The forming process of the high-energy small coated grain column is as follows: Preparation of the coating: First, mix 100 parts of liquid silicone rubber with 2 parts of aramid fiber (length 2-3mm), 7 parts of kaolin, 18 parts of ablation-resistant resin and 15 parts of fumed silica. After mixing evenly, evacuate for 1 hour, then add 2 parts of curing agent and stir for 1 hour for use; For the surface treatment of the grain, apply two coats of coupling agent on the bonding surface of the screw pressed grain as a surface treatment agent and let it dry for at least 2 hours; Assembly, the assembly steps are the same as those of Example 1; Curing: Place the assembled rectangular vertical mold and drug column in an explosion-proof vacuum oven, control the temperature at 50°C under vacuum conditions, and cure for 6 hours; After demoulding, take out the powder column and let it stand at room temperature, disassemble the U-shaped clamp, lower mold 4, upper mold 1, guide sleeve 3 and inner sleeve ring 2 in order, separate the inner sleeve ring 2 from the powder column, clean the excess coating on the surface of the vertical strip hole on the flash of the powder column and its side wall, and perform demoulding according to the safety requirements of pyrotechnics; Inspection: Check the size of the coated powder column according to the dimensions on the design drawings, whether the shape and size of the combustion surface are accurate, and whether the appearance of the coated powder column is intact. At the same time, perform non-destructive testing to confirm whether there is any debonding phenomenon on the interface. The qualified products will be packaged and stored according to the requirements of pyrotechnics.

[0021] It is worth noting that (1) the coated grain of the present invention comprises a grain and a coating sleeve wrapped around the outside of the grain, and a first combustion hole and a second combustion hole are respectively provided on the end of the grain away from the coating sleeve and the side wall thereof, so as to increase the combustion surface of the coated grain by burning the first combustion hole and the second combustion hole simultaneously; the combustion speed is increased under the condition of a certain amount of grain, and a higher energy output is achieved at the moment of combustion, thereby effectively meeting the high energy requirements of the rocket engine; (2) A rectangular vertical mold is set to ensure the accuracy of the grain forming, the inner ring is set to a petal structure and a polytetrafluoroethylene coating is set on the inner wall of the inner ring, which effectively solves the problem of demoulding the coated grain and improves the production efficiency and grain quality; (3) The outer side of the grain is wrapped with a coating sleeve, which makes the grain have good ablation resistance. During the combustion process of the grain, it can effectively prevent the coating layer from burning and clogging the throat, thus ensuring the normal operation of the solid rocket engine.

[0022] (4) After multiple tests and ignition verification, the coated grain of the present invention can obtain higher energy at the moment of combustion. In the process of forming the coated grain, from surface treatment of the grain to assembly, curing and demolding, each link is closely coordinated to ensure the precise size of the coated grain and the stable shape and size of its combustion surface, so that the grain is stable and uniform during combustion at a high burning rate, and the energy of the grain is efficiently released and utilized; the coating has good ablation resistance, which effectively promotes the development of solid rocket engine technology and is of great significance in practical applications.

[0023] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-energy small coated powder column, characterized in that: It includes a medicine column and a coating sleeve wrapped around the outside of the medicine column; The coating sleeve is an annular sleeve with one end closed, and the coating sleeve has ablation resistance and is used to prevent the coating sleeve from burning off during the combustion of the charge; The coating sleeve comprises 100-150 parts of liquid silicone rubber, 1-2 parts of aramid fiber, 5-10 parts of kaolin, 15-20 parts of ablation-resistant resin, 10-20 parts of fumed silica and 2 parts of curing agent; the premix of 100-150 parts of liquid silicone rubber, 1-2 parts of aramid fiber, 5-10 parts of kaolin, 15-20 parts of ablation-resistant resin, 10-20 parts of fumed silica and 2 parts of curing agent is loaded into a rectangular vertical mold for compression molding; The end of the charge away from being wrapped by the coating sleeve and the side wall thereof are respectively provided with a first combustion hole and a second combustion hole, which are used to increase the combustion surface of the coated charge through simultaneous combustion of the first combustion hole and the second combustion hole.

2. The high-energy small coated powder column according to claim 1, characterized in that: The aramid fiber has a length of 2-3 mm.

3. The high-energy small coated powder column according to claim 1, characterized in that: The first combustion hole is a circular inner hole, and the second combustion hole is a vertical long hole. The circular inner hole is arranged at the center of one end of the charge, and the vertical long hole is arranged on the side wall of the charge.

4. The high-energy small coated powder column according to claim 3, characterized in that: The rectangular vertical mold includes an inner ring, which is a petal structure for facilitating demoulding of the solidified drug column and the covering sleeve, and a protrusion is provided on the inner wall of the inner ring for forming vertical long holes on the side wall of the drug column.

5. The high-energy small coated grain column according to claim 4, characterized in that: A polytetrafluoroethylene coating is provided on the inner wall of the inner ring. The thickness of the polytetrafluoroethylene coating is 0.01-0.02 mm, which is used to prevent the covering sleeve from adhering to the inner wall of the inner ring and affecting demoulding.

6. A method for forming a high-energy small coated drug column, characterized in that: The following steps are involved: S1, grain surface treatment, first brush the surface treatment agent on the side wall of the grain, and then dry it for at least 2 hours; S2, assembling, putting the drug column into the rectangular vertical mold, wherein the rectangular vertical mold is composed of an upper mold, an inner sleeve ring, a guide sleeve and a lower mold. During assembly, first put the drug column on the upper mold, then put the guide sleeve on the upper mold, put the inner sleeve ring into the guide sleeve and assemble it with the lower mold; put the prepared coating sleeve into the inner sleeve ring; then put the upper mold into the inner sleeve ring and position it with the lower mold, finally clean up the excess coating sleeve, and finally clamp the rectangular vertical mold with a U-shaped clamp; S3, curing, placing the assembled rectangular vertical mold and the medicine column in an explosion-proof vacuum oven, and curing the coating sleeve and the medicine column into an integral body under vacuum conditions; S4, demoulding. After curing is completed, the grain is taken out from the rectangular vertical mold and allowed to stand at room temperature. The components of the rectangular vertical mold are disassembled in sequence, the inner ring and the grain are separated, and the excess coating on the surface of the vertical strip holes on the grain flash and its side wall is cleaned; S5, inspection, check the size of the coated grain according to the design drawing, whether the shape and size of the combustion surface are accurate, whether the appearance of the coated grain is intact, and perform non-destructive testing at the same time to confirm whether there is any debonding phenomenon on the interface.

7. The method for forming a high-energy small-sized coated grain column according to claim 6, characterized in that: The surface treatment agent is a coupling agent, which is used to enhance the bonding effect between the drug column and the coating sleeve.

8. The method for forming a high-energy small-sized coated grain column according to claim 6, characterized in that: In step S3, under vacuum conditions, the temperature is controlled at 40°C-50°C and the curing is performed for 4h-6h, so that the coating sleeve and the drug column are cured and formed into an integral body.

Images