Method for manufacturing a conical engine housing

Abstract

The present application relates to the technical field of solid rocket engine shell, and more particularly to a preparation method of a conical engine shell, which comprises the following steps: S1, preparing a sand core mold; S2, making a rubber sheet; S3, coating and assembling a front joint and a rear joint; S4, coating an inner lining layer; S5, winding and forming a composite material layer; S6, mounting a front skirt and a rear skirt; S7, machining the front skirt and the rear skirt; and S8, demolding.The preparation method of the conical engine shell can realize the winding of the conical shell with equal wall thickness.

Description

Technical Field

[0001] This invention relates to the field of solid rocket motor casing technology, and more particularly to a method for preparing a conical motor casing. Background Technology

[0002] As a key component of the power and fuel system of solid rocket motors, the solid rocket motor casing is increasingly being developed towards a structure that can withstand higher loads while maintaining high efficiency and lightweight design. Carbon fiber composites, with their advantages of high specific strength, high specific modulus, and strong design flexibility, have been widely used in the fiber-wound casings of solid rocket motors. Conical motor casings offer the advantage of lower drag during the gliding phase compared to cylindrical casings; however, research on conical motor casings in China is limited, especially regarding the winding process. Due to the different diameters at both ends of the conical casing, current winding processes cannot achieve uniform wall thickness winding, leading to a decrease in the performance of the conical motor casing. Summary of the Invention

[0003] To address the problem of the inability to achieve equal wall thickness winding for conical shells, this invention provides a method for preparing a conical engine shell, which enables equal wall thickness winding for conical shells.

[0004] The method for preparing the conical engine housing provided by this invention specifically includes the following steps:

[0005] S1. Preparation of sand core mold: Design a sand core mold with the same proportion as the size of the conical cylinder, fill the prepared sand material into the mold cavity of the sand core mold, cure and demold, and fix the prepared sand core mold on the mandrel.

[0006] S2. Film Making: Measure the thickness of the film over its entire surface and make the film that meets the tolerance requirements according to the dimensions of the conical cylinder.

[0007] S3. Wrapping and assembly of front and rear connectors: Sandblast the positions where the front and rear connectors are to be laid, apply adhesive to the sandblasted positions and lay the film, insert the front and rear connectors into the mandrel, and then fix the front and rear connectors to the conical cylinder body by the front connector clamping plate and the rear connector clamping plate.

[0008] S4. Inner lining layer covering: Determine the reference position for film splicing on the outer surface of the sand core mold, and lay the film circumferentially from the reference position to both ends, ensuring the surface of the film is flat during the splicing process.

[0009] S5. Composite material layer winding molding: Determine the winding angle of the carbon fiber composite material according to the size of the conical cylinder, and wind the outer surface of the inner liner layer with equal wall thickness according to the winding angle, the moving speed of the axial moving mechanism of the nozzle and the rotation speed of the mandrel.

[0010] S6. Installation of the front and rear skirts: An elastic layer is bonded to the inner and outer surfaces of the front and rear skirts that contact the conical body. Bolts are used to fix the front skirt and front skirt positioning fixture and the rear skirt and rear skirt positioning fixture together. The front skirt positioning fixture and the rear skirt positioning fixture are fixed by tightening the front skirt clamping plate and the rear skirt clamping plate respectively, and the conical engine housing is assembled. The assembled conical engine housing is cured according to the curing regime.

[0011] S7. Machining of the front and rear skirts: Machining of the front and rear skirts according to the design requirements of the conical engine housing.

[0012] S8. Demolding: Disassemble the front skirt clamping plate, rear skirt clamping plate, front skirt positioning fixture, rear skirt positioning fixture, front connector clamping plate and rear connector clamping plate, pull the mandrel out from the large end face of the conical cylinder, and remove the sand core mold.

[0013] Preferably, step S1 specifically includes the following steps:

[0014] S11. The sand core mold is made by dividing the conical cylinder into two parts according to the size of the conical cylinder and along the vertical axis of symmetry of the conical cylinder. Both sand core molds are equipped with stop positioning.

[0015] S12. Mix polyvinyl alcohol granules with hot water at a ratio of 1:3 to form a polyvinyl alcohol solution. Mix the polyvinyl alcohol solution with sand at a ratio of 1:5 to form sand.

[0016] S13. Apply a release agent to the mold cavity of the sand core mold, fill the mold cavity with sand, and after the mold cavity is filled with sand, scrape the sand at the filling opening of the sand core mold to make it smooth.

[0017] S14. Place the sand core mold filled with sand into an oven, set the oven temperature to 100℃, and remove the sand core mold from the oven and demold it after five hours.

[0018] S15. After splicing and fixing the two sand core mold parts, insert the mandrel and use plaster to smooth the joint between the two sand core mold parts. Use sandpaper to polish the surface of the dried plaster to make the surface of the sand core mold smooth.

[0019] Preferably, step S2 requires measuring the thickness at least 6 to 8 points within each 100mm*100mm film area.

[0020] Preferably, in steps S3 and S4, the two films are spliced ​​and laid out by overlapping with oblique cuts.

[0021] Preferably, step S5 specifically includes the following steps:

[0022] S51. From the dimensions of the conical cylinder, we can know that:

[0023] D1×cosθ1=D2×cosθ2 (1);

[0024] The small end diameter of the conical cylinder is D1, the small end winding angle is θ1, the large end diameter of the conical cylinder is D2, and the large end winding angle is θ2.

[0025] S52. Suppose that the carbon fiber composite material is wound from the large end to the small end of the conical cylinder, and the cone angle of the conical cylinder is:

[0026] β=tan -1 *[(D2-D1) / 2L] (2);

[0027] Where L is the length of the conical cylinder;

[0028] S53. Combining equations (1) and (2), the winding angle corresponding to the axial movement mechanism of the screw nozzle during the movement process is derived as follows:

[0029] α=cos -1 [(D2*cosθ2) / (D2-2*Z*tanβ)] (3);

[0030] Where Z is the distance that the axial moving mechanism of the screw nozzle moves axially from the large end to the small end;

[0031] S54. Combining equations (1), (2), and (3), the relationship between the moving speed V of the screw tip axial moving mechanism and the rotational speed n of the spindle is derived as follows:

[0032]

[0033] S55. Write a winding program according to formula (4) to control the axial movement mechanism of the nozzle and the mandrel to realize the equal wall thickness winding of carbon fiber composite material on the outer surface of the inner liner.

[0034] Preferably, the curing process in step S6 is as follows: a) curing at 85℃~95℃ for 115min~125min; b) curing at 105℃~115℃ for 55min~65min; c) curing at 135℃~145℃ for 55min~65min; d) curing at 165℃~175℃ for 235min~245min.

[0035] Preferably, the method for splicing and fixing the two sand core molds in step S15 is as follows: apply glue to the splicing surfaces of the two sand core molds and insert them into the mounting shaft. Set nuts at both ends of the mounting shaft and clamp the two sand core molds with the two nuts so that the splicing surfaces of the two sand core films come into contact with each other. Remove the sand core film that has been glued and fixed from the mounting shaft.

[0036] Compared with the prior art, the present invention can achieve the following beneficial effects: The present invention proposes a method for preparing a conical shell and a method for achieving equal wall thickness winding of the conical engine shell, so that the conical shell is subjected to uniform stress during use and the performance of the conical engine shell is improved. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of the conical engine housing provided according to an embodiment of the present invention;

[0038] Figure 2 This is a side view of the conical engine housing during the manufacturing process according to an embodiment of the present invention;

[0039] Figure 3 This is a cross-sectional structural diagram of the conical engine casing during the manufacturing process according to an embodiment of the present invention;

[0040] Figure 4 This is a schematic flowchart of a method for preparing a conical engine housing according to an embodiment of the present invention;

[0041] Figure 5 This is a schematic diagram of the structure of the fixing fixture for the sand core mold provided in an embodiment of the present invention;

[0042] Figure 6 This is a schematic diagram of the winding of a conical engine housing according to an embodiment of the present invention.

[0043] The reference numerals in the attached drawings include: conical cylinder 1, front connector 2, rear connector 3, front skirt 4, rear skirt 5, sand core mold 6, mandrel 7, front connector clamping plate 8, rear connector clamping plate 9, front skirt positioning fixture 10, rear skirt positioning fixture 11, front skirt clamping plate 12, rear skirt clamping plate 13, and mounting shaft 14. Detailed Implementation

[0044] In the following description, embodiments of the invention will be described with reference to the accompanying drawings. In the description below, the same modules are denoted by the same reference numerals. Where the same reference numerals are used, their names and functions are also the same. Therefore, their detailed description will not be repeated.

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0046] Figure 1 The structure of a conical engine housing provided according to an embodiment of the present invention is shown.

[0047] like Figure 1 As shown, the conical engine housing provided in this embodiment of the invention includes a front skirt 4, a rear skirt 5, a front connector 2, a rear connector 3, and a conical cylinder 1. The conical cylinder 1 is a cylindrical tube with openings at both ends and different diameters at both ends. The centers of the openings at both ends of the conical cylinder 1 are on the same horizontal line. The front connector 2 and the rear connector 3 are respectively connected to the openings at both ends of the conical cylinder 1. The front skirt 4 and the rear skirt 5 are respectively connected to the two ends of the conical cylinder 1.

[0048] The foregoing description details the conical engine housing structure provided by this invention. This conical engine housing is manufactured using a mold, the structure of which is as follows: Figure 2 and Figure 3 As shown below, in conjunction with Figure 2 and Figure 3 The preparation method of the conical engine casing is described in detail.

[0049] Figure 4 The flowchart of a method for preparing a conical engine housing according to an embodiment of the present invention is shown.

[0050] like Figure 4 As shown, the method for preparing the conical engine housing provided in this embodiment of the invention specifically includes the following steps:

[0051] S1. Preparation of sand core mold 6: Design a sand core mold 6 with the same proportion according to the size of the conical cylinder 1, fill the prepared sand material into the mold cavity of the sand core mold 6, solidify and demold, and fix the prepared sand core mold 6 on the mandrel 7.

[0052] Step S1 specifically includes the following steps:

[0053] S11. The sand core mold 6 is made by dividing the conical cylinder 1 into two parts along the vertical axis of symmetry of the conical cylinder 1 according to the size of the conical cylinder 1. Both parts of the sand core mold 6 are provided with a stop for positioning.

[0054] S12. Mix polyvinyl alcohol granules with hot water at a ratio of 1:3 to form a polyvinyl alcohol solution. Mix the polyvinyl alcohol solution with sand at a ratio of 1:5 to form sand.

[0055] S13. Apply a release agent to the mold cavity of the sand core mold 6, fill the mold cavity with sand, and after the sand fills the mold cavity, scrape the sand at the filling opening of the sand core mold 6.

[0056] S14. Place the sand core mold 6 filled with sand into the oven, set the temperature of the oven to 100℃, and remove the sand core mold 6 from the oven and demold it after five hours.

[0057] S15. After splicing and fixing the two sand core molds 6, insert the mandrel 7, and use plaster to smooth the joint between the two sand core molds 6. Use sandpaper to polish the surface of the dried plaster to make the surface of the sand core mold 6 flat.

[0058] Figure 5 The structure of a fixing fixture for a sand core mold provided according to an embodiment of the present invention is shown.

[0059] like Figure 5 As shown, glue is applied to the splicing surfaces of the two sand core molds 6 and inserted into the mounting shaft 14. Nuts are fitted at both ends of the mounting shaft 14. The two sand core molds 6 are clamped together by the two nuts, so that the splicing surfaces of the two sand core molds 6 come into contact with each other. The sand core molds 6 that have been glued and fixed are then removed from the mounting shaft 14.

[0060] S2. Film making: Measure the thickness of the film over its entire surface area, and make the film that meets the tolerance requirements according to the surface dimensions of the conical cylinder 1.

[0061] The production requirement for step S2 is to measure the thickness at least 6 to 8 points within each 100mm*100mm film area.

[0062] S3. Covering and assembly of front connector 2 and rear connector 3: Sandblast the positions where the film is laid on the front connector 2 and rear connector 3, apply adhesive to the surface of the sandblasted position and lay the film. After inserting the front connector 2 and rear connector 3 into the mandrel 7, fix the front connector 2 and rear connector 3 to the conical cylinder 1 by the front connector clamping plate 8 and the rear connector clamping plate 9.

[0063] In steps S3 and S4, the purpose of sandblasting at the film laying position is to increase the surface roughness of the front and rear joints and improve the bonding strength between the film and the front and rear joints. The two films are spliced ​​and laid in the form of oblique cut overlap.

[0064] Before applying the inner lining, prepare the adhesive application tools, including two 1-inch brushes. Place the adhesive sheet on a platform, heat it with a heat gun, and bevel the edges with a utility knife. When splicing the adhesive sheet circumferentially, ensure that the sheets overlap seamlessly, without misalignment, and without wrinkles during installation. After the sheets are installed, air out the air. Trim any excess adhesive and protrusions to ensure a smooth surface.

[0065] S4. Inner lining layer covering: Determine the reference position for film splicing on the outer surface of the sand core mold 6, and lay the film circumferentially from the reference position to both ends, ensuring that the surface of the film is flat during the splicing process.

[0066] Figure 6 The winding of a conical engine housing according to an embodiment of the present invention is shown. Figure 6 As shown, equal wall thickness winding can be achieved by winding at a constant winding angle for cylindrical engine housings. However, to achieve equal wall thickness winding for conical engine housings and meet the requirement of fibers being adjacent to each other, variable angle winding is required. The winding angle is larger at the end with a larger diameter and smaller at the end with a smaller diameter. This results in the fiber component in the circumferential direction of the conical engine housing being wider at the larger end and narrower at the smaller end, thus achieving dense fiber packing in the conical engine housing.

[0067] S5. Composite material layer winding molding: Determine the winding angle of the carbon fiber composite material according to the size of the conical cylinder 1, and perform equal wall thickness winding on the outer surface of the inner liner according to the winding angle, the moving speed of the axial moving mechanism of the screw nozzle and the rotation speed of the mandrel 7.

[0068] Step S5 specifically includes the following steps:

[0069] S51. From the dimensions of the conical cylinder 1, we can know that:

[0070] D1×cosθ1=D2×cosθ2 (1);

[0071] Among them, the small end diameter of the conical cylinder 1 is D1, the small end winding angle is θ1, the large end diameter of the conical cylinder 1 is D2, and the large end winding angle is θ2;

[0072] S52. Assume that the carbon fiber composite material is wound from the large end of the conical cylinder 1 to the small end of the conical cylinder 1, and the cone angle of the conical cylinder 1 is:

[0073] β=tan -1 *[(D2-D1) / 2L] (2); where L is the length of the conical cylinder 1;

[0074] S53. Combining equations (1) and (2), the winding angle corresponding to the axial movement mechanism of the screw nozzle during the movement process is derived as follows:

[0075] α=cos -1 [(D2*cosθ2) / (D2-2*Z*tanβ)] (3);

[0076] Where Z is the distance that the axial moving mechanism of the screw nozzle moves axially from the large end to the small end;

[0077] S54. Combining equations (1), (2), and (3), the relationship between the moving speed V of the screw tip axial moving mechanism and the rotational speed n of the spindle 7 is derived as follows:

[0078]

[0079] S55. Write a winding program according to formula (4) to control the axial movement mechanism of the thread nozzle and the mandrel 7 to realize the equal wall thickness winding of the carbon fiber composite material on the outer surface of the inner liner.

[0080] S6. Installation of front skirt 4 and rear skirt 5: An elastic layer is bonded to the inner and outer surfaces of the front skirt 4 and rear skirt 5 that contact the conical cylinder 1. The front skirt 4 and the front skirt positioning fixture 10 and the rear skirt 5 and the rear skirt positioning fixture 11 are fixed together with bolts. The front skirt positioning fixture 10 and the rear skirt positioning fixture 11 are fixed by tightening the front skirt clamping plate 12 and the rear skirt clamping plate 13 respectively, and the conical engine housing is assembled. The assembled conical engine housing is cured according to the curing regime.

[0081] The curing process in step S6 is as follows: a) Curing at 85℃~95℃ for 115min~125min; b) Curing at 105℃~115℃ for 55min~65min; c) Curing at 135℃~145℃ for 55min~65min; d) Curing at 165℃~175℃ for 235min~245min. S7. Machining of the front skirt 4 and rear skirt 5: The front skirt 4 and rear skirt 5 are machined according to the design requirements of the conical engine housing.

[0082] S8. Demolding: Disassemble the front skirt clamping plate 12, the rear skirt clamping plate 13, the front skirt positioning fixture 10, the rear skirt positioning fixture 11, the front connector clamping plate 8, and the rear connector clamping plate 9. Pull the mandrel 7 out from the large end face of the conical cylinder 1 and remove the sand core mold 6.

[0083] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0084] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for preparing a conical engine casing, characterized in that, Specifically, the steps include the following: S1. Preparation of sand core mold: Design a sand core mold with the same proportion according to the size of the conical cylinder, fill the prepared sand material into the mold cavity of the sand core mold, solidify and demold, and fix the prepared sand core mold on the mandrel. S2. Making the film: The film is fully measured for thickness, and the film that meets the tolerance requirements is made according to the surface dimensions of the conical cylinder. The manufacturing requirement for step S2 is that every 100mm Measure the thickness at least 6 points within a 100mm film area; S3. Covering and assembly of the front and rear connectors: Sandblasting is performed on the film placement positions of the front and rear connectors to increase the surface roughness of the front and rear connectors. Adhesive is applied to the sandblasted surfaces and the film is then placed on them. After the front and rear connectors are inserted into the mandrel, they are fixed to the conical cylinder body by the front and rear connector clamping plates. S4. Inner lining layer covering: Determine the reference position for splicing the film on the outer surface of the sand core mold, and lay the film circumferentially from the reference position to both ends, ensuring that the surface of the film is flat during the splicing process; In steps S3 and S4, the two films are spliced ​​and laid out using a beveled overlap. S5. Composite material layer winding molding: The winding angle of the carbon fiber composite material is determined according to the size of the conical cylinder. The outer surface of the inner liner is wound with equal wall thickness according to the winding angle, the moving speed of the axial moving mechanism of the nozzle and the rotation speed of the mandrel. Step S5 specifically includes the following steps: S51. From the dimensions of the conical cylinder, it can be known that: 1×cos 1= 2×cos 2(1); The small end diameter of the conical cylinder is D1, and the small end winding angle is...

1. The large end diameter of the conical cylinder is D2, and the large end winding angle is... 2; S52. Assume the carbon fiber composite material is wound from the large end to the small end of the conical cylinder, and the cone angle of the conical cylinder is: =tan 1 [( 2 1) / 2 ](2); Where L is the length of the conical cylinder; S53. Combining equations (1) and (2), the winding angle corresponding to the axial movement mechanism of the screw nozzle during the movement process is derived as follows: =cos 1 [( 2 cos 2) / ( 2 2 so )](3); Where Z is the distance that the axial moving mechanism of the screw nozzle moves axially from the large end to the small end; S54. The moving speed of the axial moving mechanism of the screw nozzle is derived by combining equations (1), (2) and (3). With respect to the rotational speed of the mandrel The relationship is: （4）； S55. Write a winding program according to formula (4) to control the axial movement mechanism of the filament and the mandrel to realize the equal wall thickness winding of the carbon fiber composite material on the outer surface of the inner liner. S6. Installation of the front and rear skirts: An elastic layer is bonded to the inner and outer surfaces of the front and rear skirts that contact the conical cylinder body. The front skirt and the front skirt positioning fixture and the rear skirt and the rear skirt positioning fixture are fixed together with bolts. The front skirt positioning fixture and the rear skirt positioning fixture are fixed by tightening the front skirt clamping plate and the rear skirt clamping plate respectively, and the conical engine housing is assembled. The assembled conical engine housing is cured according to the curing regime. S7. Machining of the front and rear skirts: Machining of the front and rear skirts according to the design requirements of the conical engine housing; S8. Demolding: Disassemble the front skirt clamping plate, the rear skirt clamping plate, the front skirt positioning fixture, the rear skirt positioning fixture, the front connector clamping plate, and the rear connector clamping plate, and pull the mandrel out from the large end face of the conical cylinder to remove the sand core mold.

2. The method for preparing the conical engine housing according to claim 1, characterized in that, Step S1 specifically includes the following steps: S11. The sand core mold is made by dividing the conical cylinder into two parts along the vertical axis of symmetry of the conical cylinder according to the size of the conical cylinder. Both sand core molds are provided with stop positioning. S12. Polyvinyl alcohol particles and hot water are stirred evenly in a ratio of 1:3 to form a polyvinyl alcohol solution, and the polyvinyl alcohol solution is stirred evenly with sand in a ratio of 1:5 to form sand material. S13. Coat the mold cavity of the sand core mold with a release agent, fill the mold cavity with sand, and after the mold cavity is filled with sand, scrape the sand at the filling opening of the sand core mold flat. S14. Place the sand core mold filled with the sand material into an oven, set the temperature of the oven to 100°C, and remove the sand core mold from the oven and demold it after five hours. S15. After splicing and fixing the two sand core mold parts, insert them into the mandrel, and use plaster to smooth the joint between the two sand core mold parts. Use sandpaper to polish the surface of the plaster after it has dried, so that the surface of the sand core mold is flat.

3. The method for preparing the conical engine housing according to claim 1, characterized in that, The curing process in step S6 is as follows: a) curing at 85℃~95℃ for 115min~125min; b) curing at 105℃~115℃ for 55min~65min; c) curing at 135℃~145℃ for 55min~65min; d) curing at 165℃~175℃ for 235min~245min.

4. The method for preparing the conical engine housing according to claim 2, characterized in that, The method for splicing and fixing the two sand core molds in step S15 is as follows: apply glue to the splicing surfaces of the two sand core molds and insert them into the mounting shaft. Set nuts at both ends of the mounting shaft and clamp the two sand core molds together with the two nuts so that the splicing surfaces of the two sand core molds come into contact with each other. Remove the sand core molds that have been glued and fixed from the mounting shaft.

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