An aircraft composite fuel tank and method of designing the same

Abstract

The application discloses a kind of aircraft composite material oil tank and design method in the technical field of composite material oil tank, including multi-section oil tank barrel section, oil tank connecting frame, end face sealing plate, internal partition and lid;Multi-section oil tank section is connected by oil tank connecting frame;Oil tank connecting frame is sleeved with front and rear oil tank barrel section;Multiple internal partitions are provided in multi-section oil tank section;Internal partition is connected with the inner wall of oil tank barrel section by riveting cover sealing mode;Lid is arranged at the front end of multi-section oil tank barrel section;The rear end of multi-section oil tank barrel section is sealed by end face sealing plate;Multiple internal partitions are provided on the entire tank body of multi-section oil tank barrel section also bonding outer skin.The application is segmented from length direction to oil tank, is assembled and connected by multi-section structure;Realize the production and preparation of special-shaped cross-section oil tank, guarantee its internal pipeline installation and sealing, and meet the overload requirement under each flight working condition.

Description

Technical Field

[0001] This invention relates to the field of composite material fuel tank technology, and in particular to a composite material fuel tank for aircraft and its design method. Background Technology

[0002] Currently, the fuel tank materials used in aircraft are mainly divided into two types: aluminum alloy and composite materials. Aluminum alloy has the characteristics of high strength and good resistance to high and low temperatures. Compared with aluminum alloy fuel tanks, composite fuel tanks have the advantages of being lightweight while maintaining comparable strength and rigidity. However, composite fuel tanks are often difficult to manufacture due to limitations in mold making and demolding, especially for fuel tanks with irregular cross-sections. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a composite material fuel tank for aircraft and its design method, which enables the production of fuel tanks with irregular cross-sections, ensures the installation and sealing of internal pipelines, and meets the overload requirements under various flight conditions.

[0004] The objective of this invention is achieved in part by providing a design method for a composite material fuel tank for an aircraft, comprising the following steps: 1) First, the three sections of the fuel tank barrel, the fuel tank connecting frame, the internal partition frame and the cap are formed by mold. The fuel tank end face sealing plate is formed by machining. Then, they are assembled and installed. 2) Internal frame connection: Install the frame inside the fuel tank. The frame is broken into two parts and connected by a frame connecting plate. On the outside of the fuel tank, make connection holes between the frame and the fuel tank skin according to the frame position, and connect them using fasteners. 3) Tank Segment Positioning: Position the polished and fitted tank segment using an assembly fixture, ensuring the positioning plate fits snugly against the tank without gaps; position the first end face of the tank using the fixture's end face positioning block; sequentially fix the tank connecting frame, second tank segment, third tank segment, and end face sealing plate onto the assembly fixture, and position the end face sealing plate web surface using the end face sealing plate positioning block; fix the outer clamping plate in place to ensure the overall relative position of the tank; 4) Making connection holes: After the tooling clamps position the parts, make the connection holes between the oil tank section and the oil tank connection frame, the oil tank connection plate and the oil tank section, and the oil tank section and the end face partition. 5) Fuel line assembly: According to the theoretical position of the digital model, make the vent holes, oil passage holes and connector holes of each partition; seal and install the pipeline connectors on the end face partition, connect the pipeline, and use clamps to fix the pipeline to the partition to ensure that the pipeline does not shake. 6) Fuel Tank Sealing Connection: Roughen and clean the joint area of ​​the fuel tank section. Apply sealant to the mating surfaces of the first fuel tank section, the fuel tank connecting frame, and the fuel tank connecting plate, and position them on the fixture. Connect them using fasteners. Then, apply sealant to the second fuel tank section and fit it onto the fuel tank connecting frame, positioning it with the fixture. Wet-install the fasteners. Connect all fuel tank sections in this order. When connecting the fuel tanks in sequence, fillet the corners and seal the nail heads at each connection point. 7) Fuel tank cap installation: Place the cap frame inside the fuel tank opening, make the connection hole, fit the cap to the skin opening, and make the connection hole between the cap and the cap frame; install the support plate nut at the hole position on the cap frame; apply sealant to the mating surface of the cap frame and the fuel tank, and connect with rivets; apply sealant around the cap frame, and connect the cap with countersunk screws.

[0005] As a further limitation of the present invention, the three oil tank sections in step 1) are formed by a male mold, and the oil tank connecting frame is formed by a female mold.

[0006] As a further limitation of the present invention, the partition frame connecting plate in step 2) is positioned at the corner of the partition frame. After the position of the partition frame connecting plate is determined, the connecting hole between the partition plate and the partition frame is made, and the connection is made using a blind rivet.

[0007] Another aspect of the objective of this invention is achieved as follows: A composite material fuel tank for aircraft includes multiple fuel tank sections, a fuel tank connecting frame, an end face sealing plate, an internal partition frame, and a cover; the multiple fuel tank sections are connected to each other via the fuel tank connecting frame; the fuel tank connecting frame is sleeved with the front and rear fuel tank sections; multiple internal partition frames are provided within each of the multiple fuel tank sections; the internal partition frames are connected to the inner wall of the fuel tank sections by riveting and sealing; the cover is located at the front end of each of the multiple fuel tank sections; the rear end of each of the multiple fuel tank sections is sealed by the end face sealing plate; and an outer skin is also adhered to the entire tank body of each of the multiple fuel tank sections.

[0008] As a further limitation of the present invention, the multi-section oil tank includes a first section, a second section, and a third section; the first section has a closed front end face and an open rear end face; the second and third sections have open front and rear end faces.

[0009] As a further limitation of the present invention, the oil tank connecting frame is respectively sleeved with the front and rear oil tank barrel sections, with each oil tank barrel section being sleeved by 20mm.

[0010] As a further limitation of the present invention, the bottom of the oil tank connecting frame is provided with an oil passage hole and the top is provided with a vent hole; an oil tank connecting plate is provided on the oil tank connecting frame.

[0011] As a further limitation of the present invention, the internal partition is a disconnected structure, connected by a partition connecting plate; the top connecting gap of the internal partition serves as a vent hole, and the bottom of the internal partition has an oil passage hole.

[0012] As a further limitation of the present invention, the end face sealing plate is made of aluminum alloy with a thickness of 2mm and a flange length of 40mm; the outer side and bottom side of the end face sealing plate bonded to the outer skin are connected by countersunk rivets, and the inner side and top side are connected by semi-circular head rivets.

[0013] As a further limitation of the present invention, the outer side and bottom of the multi-section oil tank barrel are connected to the outer skin using countersunk rivets, and the inner side and top are connected using semi-circular head rivets.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention manufactures the fuel tank section by section, which simplifies the part structure and effectively reduces the cost and manufacturing difficulty of the parts; the internal frame is easy to install and seal, and can effectively control the deformation effect of the aircraft load on the fuel tank under various operating conditions; the internal frame can be added or reduced according to different operating conditions of the aircraft, which has strong adaptability.

[0015] Each pair of fuel tank sections is connected by a composite material connecting frame. The connecting frame is formed using a female mold to ensure the surface profile of the section that fits into the fuel tank, making it easy to fit and reducing the amount of assembly and grinding. At the same time, the connecting plate of the fuel tank connecting frame can provide a baffle inside the fuel tank, limiting the violent sloshing of fuel and playing a role in preventing waves. The segmented assembly can ensure the sealing quality of each internal partition and connecting frame. The use of low-density composite materials can achieve the requirements of lightweighting and reduce the overall structural weight. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0017] Figure 1 A schematic diagram of the segmented fuel tank of this invention.

[0018] Figure 2 A schematic diagram of the segmented connection of the fuel tank in this invention.

[0019] Figure 3 A schematic diagram of the fuel tank connection frame structure of the present invention.

[0020] Figure 4 A schematic diagram of the internal partition frame installation of this invention.

[0021] Figure 5 A schematic diagram of the internal partition frame structure of the fuel tank of this invention.

[0022] Figure 6 A side view of a section of the fuel tank of this invention.

[0023] Figure 7 Cross-sectional view at point AA of this invention.

[0024] Figure 8 A schematic diagram of the connection between the mouth frame and the mouth cover of this invention.

[0025] Figure 9 Schematic diagram of the end face sealing plate of the present invention.

[0026] Among them, 1 is the first section of the oil tank, 2 is the second section of the oil tank, 3 is the third section of the oil tank, 4 is the oil tank connecting frame, 4-1 is the oil tank connecting plate, 4-2 is the vent hole, 4-3 is the oil passage hole; 5 is the internal partition frame, 5-1 is the partition frame connecting plate, 5-2 is the oil passage hole; 6 is the port cover, 6-1 is the port frame, and 7 is the end face sealing plate. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] A design method for a composite material fuel tank for an aircraft includes the following steps: 1) First, the three sections of the fuel tank barrel, the fuel tank connecting frame, the internal partition frame and the cap are formed by mold. The fuel tank end face sealing plate is formed by machining. Then, they are assembled and installed. The three sections of the fuel tank barrel are formed by positive mold and the fuel tank connecting frame is formed by negative mold to ensure the profile of the fuel tank fitting section, which is easy to fit and reduces the amount of assembly grinding. 2) Internal frame connection: Install the frame inside the fuel tank. The frame is divided into two parts and connected by a frame connecting plate. The frame connecting plate is positioned at the corner of the frame. After the position of the frame connecting plate is determined, make the connection holes between the frame connecting plate and the frame, and connect them using blind rivets. On the outside of the fuel tank, make the connection holes and countersunk recesses between the frame and the fuel tank skin according to the position of the frame, and connect them using rivets and screws. 3) Tank Segment Positioning: Position the polished and fitted tank segment using an assembly fixture, ensuring the positioning plate fits snugly against the tank without gaps; position the first end face of the tank using the fixture's end face positioning block; sequentially fix the tank connecting frame, second tank segment, third tank segment, and end face sealing plate onto the assembly fixture, and position the end face sealing plate web surface using the end face sealing plate positioning block; fix the outer clamping plate in place to ensure the overall relative position of the tank; 4) Making connecting holes: After the tooling clamps position the parts, make the connecting holes and countersinks for the oil tank section and the oil tank connecting frame, the oil tank connecting plate and the oil tank section, and the oil tank section and the end face partition. 5) Fuel line assembly: According to the theoretical position of the digital model, make the vent holes, oil passage holes and connector holes of each partition; seal and install the pipeline connectors on the end face partition, connect the pipeline, and use clamps to fix the pipeline to the partition to ensure that the pipeline does not shake. 6) Fuel Tank Sealing Connection: Roughen and clean the joint area of ​​the fuel tank section. Apply sealant to the mating surfaces of the first fuel tank section, the fuel tank connecting frame, and the fuel tank connecting plate, and position them on the fixture. Connect them using fasteners. Then, apply sealant to the second fuel tank section and fit it onto the fuel tank connecting frame, positioning it with the fixture. Wet-install the fasteners. Connect all fuel tank sections in this order. When connecting the fuel tanks in sequence, fillet the corners and seal the nail heads at each connection point. 7) Fuel Tank Cap Installation: Insert the tank frame into the fuel tank opening and drill the connection hole; fit the cap to the skin opening, ensuring a proper mating clearance, and drill the connection hole between the cap and the tank frame; install a support nut at the connection hole on the tank frame to ensure the cap is removable. Apply sealant to the mating surfaces of the tank frame and connect using rivets. Apply sealant around the perimeter of the tank frame and connect the cap using countersunk screws.

[0029] like Figure 1 As shown, a composite material fuel tank for aircraft has a unique structure with a tapered front end and a recessed middle section. The fuel tank is segmented along its length and assembled into multiple sections. Each section is assembled from three smaller fuel tank sections. Considering the ease of demolding during fuel tank molding, the arrangement of T-ribs, and the angle of fuel pipe installation, the length of each smaller fuel tank section is approximately 400mm to 500mm to ensure its operability. Specifically, it includes multiple tank sections, a tank connecting frame 4, an end face sealing plate 7, internal partitions 5, and a cover 6. The multiple tank sections are connected by the tank connecting frame 4. The tank connecting frame 4 is fitted with the front and rear tank sections. Multiple internal partitions 5 are set inside the multiple tank sections. The internal partitions 5 are connected to the inner wall of the tank section by riveting and sealing. The cover 6 is set at the front end of the multiple tank sections. The rear end of the multiple tank sections is sealed by the end face sealing plate 7. An outer skin is also bonded to the entire tank body of the multiple tank sections. The parts of the tank outside and bottom of the multiple tank sections that are bonded to the outer skin use countersunk rivets HB6316 to ensure a close fit, while the inner side and top use semi-circular head rivets HB6231 to optimize the stress form and reduce the amount of countersinking work during assembly.

[0030] The fuel tank has a ring-shaped "barrel" structure, with multiple fuel tank sections including fuel tank section 1, fuel tank section 2, and fuel tank section 3. Fuel tank section 1 has a closed front end and an open rear end. Fuel tank section 2 and fuel tank section 3 have open front and rear end faces, ensuring the demolding capability of each fuel tank section.

[0031] like Figure 2-3 As shown, the fuel tank connecting frame 4 is fitted onto the front and rear fuel tank sections, with each section fitting in 20mm. Sealant is applied to the fitting surfaces before fitting, and the sections are then connected with rivets and sealed. The fuel tank connecting frame is made of composite material with a thickness of 2mm and a flange length of 40mm. The bottom of the fuel tank connecting frame 4 has a φ15mm oil passage hole 4-3, and the top has a φ10mm vent hole 4-2 to ensure the flow of fuel inside the fuel tank. A fuel tank connecting plate 4-1 is installed on the fuel tank connecting frame 4; the fuel tank connecting plate 4-1 provides a baffle inside the fuel tank, limiting violent fuel sloshing and acting as a wave stopper; and pipe holes can be opened on the connecting plate according to different fuel pipeline configurations.

[0032] like Figure 4-5 As shown, multiple T-shaped internal partitions 5 are arranged inside the oil tank according to requirements, with a structural thickness of 2mm. The internal partitions 5 are connected to the inner wall of the oil tank by riveting and sealing. To ensure the surface sealing of the internal partitions 5, the internal partitions 5 are disconnected structures and connected by partition connecting plates 5-1, which are fixed by pop rivets. The top connection gap of the internal partitions 5 serves as a vent hole, and the bottom of the internal partitions has a φ15mm oil passage hole 5-2 for oil connection.

[0033] like Figure 6-8As shown, considering the installation of the oil pipe joint and the operability of the filler seal of the oil tank connecting plate, a cover 6 structure is designed at the front end of the front oil tank. The thickness of the cover 6 and the frame 6-1 is the same as the thickness of the oil tank, both being 2mm. The frame 6-1 is connected to the oil tank using semi-circular head rivets, and the cover 6 and the frame 6-1 are connected using GB933 airtight support plate nuts GB933 and semi-circular head screws.

[0034] like Figure 9 As shown, the rear end face of the fuel tank is sealed by the fuel tank end face sealing plate 7. The end face sealing plate 7 is made of 7075 aluminum alloy with a thickness of 2mm and a flange length of 40mm. The flange has a variable cross section, which can be connected to the fuel tank and the skin at the same time, optimizing the force transmission path of the entire body structure. The outer side and bottom side of the end face sealing plate 7 are bonded to the outer skin by countersunk rivets, and the inner side and top side are connected by semi-circular head rivets.

[0035] This invention provides a composite material fuel tank for aircraft. The fuel tank has an irregular shape with a tapered front end and a recessed middle section. The fuel tank is segmented along its length and assembled into multiple sections. Each section is assembled from three smaller fuel tank sections. The internal partition is easy to install and seal, effectively controlling the deformation of the fuel tank caused by the load of the aircraft under various operating conditions. The internal partition can be added or removed according to different operating conditions of the aircraft, making it highly adaptable. Each pair of fuel tank sections is connected by a composite material connecting frame, which is formed by a negative mold to ensure the profile of the section that fits into the fuel tank, making it easy to fit and reducing the amount of assembly and grinding. This invention enables the production of fuel tanks with irregular cross-sections, ensuring the installation and sealing of internal pipelines and meeting the overload requirements under various flight conditions.

[0036] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A design method for a composite material fuel tank for an aircraft, characterized in that, Includes the following steps: 1) First, the three sections of the fuel tank barrel, the fuel tank connecting frame, the internal partition frame and the cap are formed by mold. The fuel tank end face sealing plate is formed by machining. Then, they are assembled and installed. 2) Internal frame connection: Install the frame inside the fuel tank. The frame is broken into two parts and connected by a frame connecting plate. On the outside of the fuel tank, make connection holes between the frame and the fuel tank skin according to the frame position, and connect them using fasteners. 3) Tank Segment Positioning: Position the polished and fitted tank segment using an assembly fixture, ensuring the positioning plate fits snugly against the tank without gaps; position the first end face of the tank using the fixture's end face positioning block; sequentially fix the tank connecting frame, second tank segment, third tank segment, and end face sealing plate onto the assembly fixture, and position the end face sealing plate web surface using the end face sealing plate positioning block; fix the outer clamping plate in place to ensure the overall relative position of the tank; 4) Making connection holes: After the tooling clamps position the parts, make the connection holes between the oil tank section and the oil tank connection frame, the oil tank connection plate and the oil tank section, and the oil tank section and the end face partition. 5) Fuel line assembly: According to the theoretical position of the digital model, make the vent holes, oil passage holes and connector holes of each partition; seal and install the pipeline connectors on the end face partition, connect the pipeline, and use clamps to fix the pipeline to the partition to ensure that the pipeline does not shake. 6) Fuel Tank Sealing Connection: Roughen and clean the joint area of ​​the fuel tank section. Apply sealant to the mating surfaces of the first fuel tank section, the fuel tank connecting frame, and the fuel tank connecting plate, and position them on the fixture. Connect them using fasteners. Then, apply sealant to the second fuel tank section and fit it onto the fuel tank connecting frame, positioning it with the fixture. Wet-install the fasteners. Connect all fuel tank sections in this order. When connecting the fuel tanks in sequence, fillet the corners and seal the nail heads at each connection point. 7) Fuel tank cap installation: Place the cap frame inside the fuel tank opening, make the connection hole, fit the cap to the skin opening, and make the connection hole between the cap and the cap frame; install the support plate nut at the hole position on the cap frame; apply sealant to the mating surface of the cap frame and the fuel tank, and connect with rivets; apply sealant around the cap frame, and connect the cap with countersunk screws.

2. The design method for a composite material fuel tank for an aircraft according to claim 1, characterized in that, The three oil tank sections mentioned in step 1) are formed by a positive mold, and the oil tank connecting frame is formed by a negative mold.

3. The design method for a composite material fuel tank for an aircraft according to claim 1, characterized in that, In step 2), the partition frame connecting plate is positioned at the corner of the partition frame. After the position of the partition frame connecting plate is determined, the connecting hole between the partition frame connecting plate and the partition frame is made, and the connection is made using a blind rivet.

4. A composite material fuel tank for an aircraft, designed using the design method described in claim 1, characterized in that, The system includes multiple fuel tank sections, a fuel tank connecting frame, end face sealing plates, internal partitions, and a cover. The multiple fuel tank sections are connected to each other via the fuel tank connecting frame. The fuel tank connecting frame is fitted onto the front and rear fuel tank sections. Multiple internal partitions are provided inside each fuel tank section. The internal partitions are connected to the inner wall of the fuel tank section by riveting and sealing. The cover is located at the front end of each fuel tank section. The rear end of each fuel tank section is sealed by the end face sealing plate. An outer skin is also adhered to the entire body of each fuel tank section.

5. The aircraft composite material fuel tank according to claim 4, characterized in that, The multi-section fuel tank includes a first section, a second section, and a third section; the first section has a closed front end and an open rear end; the second and third sections have open front and rear end faces.

6. The composite material fuel tank for aircraft according to claim 4, characterized in that, The oil tank connecting frame is fitted into the front and rear oil tank sections respectively, with each oil tank section fitting in 20mm.

7. The composite material fuel tank for aircraft according to claim 6, characterized in that, The oil tank connecting frame has an oil passage hole at the bottom and a vent hole at the top; the oil tank connecting frame is provided with an oil tank connecting plate.

8. The composite material fuel tank for aircraft according to claim 4, characterized in that, The internal partition is a discontinuous structure, connected by a partition connecting plate; the top connecting gap of the internal partition serves as a vent, and the bottom of the internal partition has an oil passage.

9. The composite material fuel tank for aircraft according to claim 4, characterized in that, The end face sealing plate is made of aluminum alloy with a thickness of 2mm and a flange length of 40mm. The outer side and bottom side of the end face sealing plate are bonded to the outer skin by countersunk rivets, and the inner side and top side are bonded by semi-circular head rivets.

10. The aircraft composite material fuel tank according to claim 4, characterized in that, The outer side and bottom of the multi-section oil tank are connected to the outer skin using countersunk rivets, while the inner side and top are connected using semi-circular head rivets.

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