Fireproof sealed cargo hold and design method thereof

Abstract

The invention provides a fireproof sealed cargo hold and a design method thereof, and belongs to the field of helicopter body structure function design, the method comprises the following steps: 1, an interior trim, a floor, a cargo hold door, a front frame channel door and a rear frame channel door enclose a fireproof sealed boundary; (2) fireproof sealing design of a front frame channel door is carried out, and a fireproof and fire-resistant test is completed; (3) fireproof sealing design of a rear frame channel door is carried out, and a fireproof and fire-resistant test is completed; (4) fireproof sealing design of a cargo hold door is carried out, and a fireproof and fire-resistant test is completed; and (5) air convection path design in a cargo hold is carried out. The cargo hold has fireproof sealing performance and can contain flames in the cargo hold, so that the flames cannot reach a passenger cabin and a tail beam; in the flight process of the aircraft, under the action of aerodynamic load, the cargo hold door is reliably sealed, and new oxygen is prevented from entering the cargo hold, so that the flame combustion time is prevented from being increased; interior trims and structural parts in the cargo hold are strictly tested according to airworthiness clauses, it is proved that the requirement for 5-minute fire resistance is met, and the fireproof sealing performance of the cargo hold can be guaranteed.

Description

Technical Field

[0001] The invention belongs to the field of helicopter body structure function design, and in particular relates to a fireproof sealed cargo compartment and a design method thereof. Background Art

[0002] The fireproof sealing of the cargo hold is crucial in helicopter design. If a fire occurs in the cargo hold, the flames in the cabin will spread to the passenger cabin, causing casualties, and spreading to the tail boom will cause equipment damage. During the flight of the aircraft, there is a pressure difference between the inside and outside of the cabin door and the door sealing strip, which causes deformation, which can easily cause poor sealing and allow oxygen to enter the cargo hold; when the cargo hold does not have fireproof sealing conditions, it is easy to be affected by a large amount of airflow, causing the fire to become larger or allowing harmful smoke and other toxic gases to enter the passenger cabin.

[0003] Therefore, when designing the cargo hold, it is crucial to ensure that there is an air convection path and how to achieve fireproof sealing of the cargo hold when the cabin door is deformed during the flight of the aircraft. Summary of the invention

[0004] The present invention proposes a fireproof sealed cargo hold and design method, which can contain the flame in the hold and prevent the flame from reaching the passenger cabin and tail beam; under the action of aerodynamic load during the flight of the aircraft, the cargo hold door ensures reliable sealing, and prevents new oxygen from entering the cargo hold, thereby avoiding increasing the burning time of the flame; the interior decoration and structural parts in the cargo hold are strictly tested in accordance with the airworthiness clauses, and it has been confirmed that they meet the fire resistance requirement of 5 minutes, which can ensure the fireproof sealing of the cargo hold. The technical solution is as follows:

[0005] In a first aspect, a design method for a fireproof sealed cargo hold is provided, comprising:

[0006] In the first step, the interior, floor, cargo door, front frame passage door and rear frame passage door are surrounded by a fireproof sealing boundary;

[0007] The second step is to carry out the fireproof sealing design of the front frame passage door and complete the fireproof and fire resistance test;

[0008] The third step is to carry out the fireproof sealing design of the rear frame passage door and complete the fireproof and fire resistance test;

[0009] The fourth step is to carry out the fireproof sealing design of the cargo door and complete the fireproof and fire resistance test;

[0010] The fifth step is to design the air convection path inside the cargo hold.

[0011] Optionally, the front frame passage door includes a left detachable passage door, a middle detachable passage door, and a right detachable passage door;

[0012] The upper part of the middle detachable passage door is connected to the interior decoration and the front frame web through a bracket; an annular fireproof sealing toothed rubber strip is arranged between the middle detachable passage door and the bracket; a flat rubber strip is arranged between the bracket and the interior decoration; and a strip-shaped fireproof sealing toothed rubber strip is arranged between the bracket and the front frame web;

[0013] The lower part of the middle detachable passage door is connected to the floor and the front frame web through an aluminum alloy angle bar; a strip-shaped fireproof sealing toothed rubber strip is arranged between the middle detachable passage door and the aluminum alloy angle bar; the floor adopts an aluminum panel aluminum honeycomb structure; a strip-shaped fireproof sealing toothed rubber strip is arranged between the left detachable passage door and the front frame web; a strip-shaped fireproof sealing toothed rubber strip is arranged between the middle detachable passage door and the left detachable passage door;

[0014] When conducting fire prevention and fire resistance tests, test pieces are used for testing. The test pieces are made according to the strength of different areas of the front frame channel door. The test pieces are made of two types of carbon cloth, ECS2259.20 and ECS2042.20, laid alternately. The outer surface of the test piece is sprayed with polyurethane fire retardant topcoat.

[0015] Optionally, the rear frame passage door includes an upper detachable passage door and a lower detachable passage door;

[0016] The upper part of the upper detachable channel door is connected to the rear frame web through an aluminum alloy reinforcement; a flat rubber strip is arranged between the upper detachable channel door, the interior decoration, the rear frame web and the aluminum alloy reinforcement;

[0017] The lower part of the upper detachable passage door is connected to the lower detachable passage door, and a strip-shaped fireproof sealing toothed rubber strip is arranged between the two;

[0018] The upper detachable passage door, the interior trim and the rear frame belly plate are connected by aluminum alloy reinforcing angle bars, and flat rubber strips are arranged between the upper detachable passage door, the interior trim and the aluminum alloy reinforcing angle bars;

[0019] A flat rubber strip is arranged between the lower detachable passage door and the rear frame belly plate;

[0020] When conducting fire prevention and fire resistance tests, test pieces are used for testing. The test pieces are made according to the strength of different areas of the rear frame channel door. The test pieces are paved with ECS0037, and the outer surface of the test pieces is sprayed with polyurethane fire retardant paint.

[0021] Optionally, an O-type fireproof sealing strip is provided between the cargo door and the door frame, and the interior trim is screwed to the door frame; the O-type fireproof sealing strip is cut at a 45° bevel angle in the middle of the door to separate it into two parts, the upper part is bonded to the door frame, and the lower part is bonded to the cargo door body;

[0022] When conducting fire prevention and fire resistance tests, test pieces are used for testing. The test pieces are made according to the strength of different areas of the cargo door 4. The test pieces are paved with ECS0017.108 and ECS2042.20, and the outer surface of the test pieces is sprayed with polyurethane fire retardant topcoat.

[0023] Optionally, the fireproof sealing design process of the O-type fireproof sealing strip under negative pressure is:

[0024] Step 1, calculate the compression amount e1 of the O-type fireproof sealing strip: compression amount e1 = Hs-H1, where Hs is the strip height; H1 is the strip height after compression;

[0025] Step 2, calculate the displacement dep2 of the cargo door under negative pressure conditions and calculate the target displacement dep3: displacement dep2 = (F2 / F1)*dep1, where F1 is the limit load, F2 = P2*S, P2 = (1 / 2)Cp*ρ*V2, Cp is the value given in the load manual under the maximum negative pressure value P2 of the cabin door, ρ is the air density, V is the air flow velocity, S is the surface area of ​​the cargo door, dep1 is the maximum displacement of the edge of the cargo door along the H1 direction; target displacement dep3 = dep2+1;

[0026] Step 3: Calculate the remaining compression amount e2 of the O-type fireproof sealing strip under negative pressure: e2 = e1 – dep2;

[0027] Step 4: When the residual compression amount e2 is ≥ 1-2 mm under the maximum negative pressure, it is determined that the fireproof seal of the O-type fireproof sealing strip is effective.

[0028] Optionally, in the fifth step,

[0029] When there are unblocked mounting holes on the left and right floors inside the cargo hold, the mounting holes are used as air convection holes; otherwise, air convection holes are drilled on the floor inside the cargo hold to ensure a small amount of air flow at the bottom of the helicopter.

[0030] In a second aspect, there is provided a fireproof sealed cargo hold designed by any method as described in the first aspect, comprising: a front frame passage door, a rear frame passage door, a cargo hold door, and air convection holes on the floor inside the cargo hold,

[0031] The front frame passage door is located on the reinforced frame of the cabin, the rear frame passage door is located on the reinforced frame of the tail beam, and the cargo hold door is located on the cargo hold skin.

[0032] Optionally, the front frame passage door includes a left detachable passage door, a middle detachable passage door, and a right detachable passage door;

[0033] The upper part of the middle detachable passage door is connected to the interior decoration and the front frame web through a bracket; a strip-shaped fireproof sealing toothed rubber strip is arranged between the middle detachable passage door and the bracket; a flat rubber strip is arranged between the bracket and the interior decoration; a strip-shaped fireproof sealing toothed rubber strip is arranged between the bracket and the front frame web;

[0034] The lower part of the middle detachable passage door is connected to the floor and the front frame web through an aluminum alloy angle; a strip-shaped fireproof sealing toothed rubber strip is arranged between the middle detachable passage door and the aluminum alloy angle; the floor adopts an aluminum panel aluminum honeycomb structure; a strip-shaped fireproof sealing toothed rubber strip is arranged between the left detachable passage door and the front frame web; a strip-shaped fireproof sealing toothed rubber strip is arranged between the middle detachable passage door and the left detachable passage door.

[0035] Optionally, the rear frame passage door includes an upper detachable passage door and a lower detachable passage door;

[0036] The upper part of the upper detachable channel door is connected to the rear frame belly plate through an aluminum alloy reinforcement; a flat rubber strip is arranged between the upper detachable channel door, the interior trim, the rear frame belly plate and the aluminum alloy reinforcement;

[0037] The lower part of the upper detachable passage door is connected to the lower detachable passage door, and a strip-shaped fireproof sealing toothed rubber strip is arranged between the two;

[0038] The upper detachable channel door, the interior trim and the rear frame belly plate are connected by aluminum alloy reinforcing angle bars, and flat rubber strips are arranged between the upper detachable channel door, the interior trim and the aluminum alloy reinforcing angle bars;

[0039] A flat rubber strip is arranged between the lower detachable passage door and the belly plate of the rear frame.

[0040] Optionally, an O-type fireproof sealing strip is provided between the cargo door and the door frame, and the interior decoration and the door frame are screwed; the O-type fireproof sealing strip is cut at a 45° bevel angle in the middle of the door and is divided into two parts, the upper part is bonded to the door frame, and the lower part is bonded to the cargo door body.

[0041] The beneficial effects of the present invention are at least:

[0042] The fireproof sealed cargo hold of the present invention can contain the flame in the cabin, so that the flame cannot reach the passenger cabin and the tail beam; under the action of aerodynamic load during the flight of the aircraft, the cargo door ensures reliable sealing, and prevents new oxygen from entering the cargo hold, thereby avoiding increasing the burning time of the flame; the interior decoration and structural parts in the cargo hold are strictly tested in accordance with the airworthiness clauses, and it has been confirmed that they meet the fire resistance requirement of 5 minutes, thereby ensuring the fireproof sealing of the cargo hold. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a schematic diagram of the cargo hold structure;

[0044] Figure 2 This is a schematic diagram of the fireproof sealing boundary of the cargo hold;

[0045] Figure 3 It is a schematic diagram of the structure of the front frame and its passage door;

[0046] Figure 4 It is the AA section view of the front frame channel door and the surrounding structure;

[0047] Figure 5 This is a schematic diagram of the cross section of the fireproof sealing toothed rubber strip;

[0048] Figure 6 Sectional views of the front frame channel door and surrounding structures BB, CC and DD;

[0049] Figure 7 It is a schematic diagram of a typical fire-resistant structure 1 of a front frame passage door;

[0050] Figure 8 It is a schematic diagram of a typical fire-resistant structure 2 of a front frame passage door;

[0051] Fig. 9 It is a schematic diagram of a typical fire-resistant structure 3 of a front frame passage door;

[0052] Fig.10 It is a schematic diagram of the rear frame and its passage door structure;

[0053] Fig.11 It is the AA section view of the rear frame channel door and the surrounding structure;

[0054] Fig.12 This is the BB section view of the rear frame channel door and the surrounding structure;

[0055] Fig.13 It is a CC section view of the rear frame channel door and the surrounding structure;

[0056] Fig.14 It is the DD section view of the rear frame channel door and the surrounding structure;

[0057] Fig.15 This is a schematic diagram of a typical fire-resistant structure of a rear frame passage door;

[0058] Fig.16 It is a schematic diagram of a typical connection structure 2 of the upper door and the lower door of the rear frame passage door;

[0059] Fig.17 Schematic diagram of a typical ply structure 3 of the upper and lower doors of the rear frame channel door in the test piece 2;

[0060] Fig.18 It is a schematic diagram of a typical fire-resistant structure 4 of a rear frame passage door;

[0061] Fig.19 This is a schematic diagram of the fireproof sealing structure of the cargo door;

[0062] Fig. 20 This is a schematic diagram of the installation structure of the fireproof sealing strip for the cargo door;

[0063] Fig.21 This is a schematic diagram of the installation structure of the fireproof sealing strip for the cargo door;

[0064] Fig. 22 Schematic diagram of the installation structure of the fireproof sealing strip for the cargo door.

[0065] Among them, 1- fuselage structure 2- interior 3- floor 4- cargo door 5- front frame channel door 6- rear frame channel door 7- fireproof sealing boundary 8- left removable channel door 9- middle removable channel door 10- right removable channel door 11- front frame belly plate 12- bracket 13- flat rubber strip 14- fireproof sealing toothed rubber strip 15- aluminum alloy reinforcement plate 16- blind nut 17- aluminum alloy angle 18- upper removable channel door 19- lower removable channel door 20- rear frame belly plate 21- aluminum alloy reinforcement 22- aluminum alloy reinforcement angle 23- door frame 24- fireproof sealing strip 25- upper part of the fireproof sealing strip 26- lower part of the fireproof sealing strip. DETAILED DESCRIPTION

[0066] The present invention is further described in detail below through specific implementation modes and drawings.

[0067] The present invention proposes a fireproof sealed cargo hold structure and a fireproof sealed design method for a cargo hold door sealing strip, which can contain the flame in the cabin and prevent the flame from reaching the passenger cabin and the tail beam; under the action of aerodynamic load during the flight of the aircraft, the cargo hold door ensures reliable sealing and prevents new oxygen from entering the cargo hold, thereby avoiding increasing the burning time of the flame; the interior decoration and structural parts in the cargo hold are strictly tested in accordance with the airworthiness clauses, and it has been confirmed that they meet the fire resistance requirement of 5 minutes, thereby ensuring the fireproof sealing of the cargo hold. The specific implementation process includes the following steps:

[0068] The first step is to define the boundaries of the fireproof and sealed cargo hold:

[0069] like Figure 1 , Figure 2 As shown, the cargo hold is located inside the fuselage structure 1, and its fireproof sealing area 8 is surrounded by the cabin interior 2, the floor 3, the cargo hold door 4, the front frame passage door 5 and the rear frame passage door 6 to form a fireproof sealing boundary 7.

[0070] Step 2: Fireproof sealing design of front frame passage door 5:

[0071] like Figure 3 As shown, in order to facilitate personnel to enter the cargo hold for maintenance, the front frame is designed with a left detachable passage door 8, a middle detachable passage door 9, and a right detachable passage door 10.

[0072] like Figure 4 As shown, the upper part of the middle detachable passage door 9 is connected to the interior decoration 2 and the front frame belly plate 11 through the bracket 12; a strip-shaped fireproof sealing toothed rubber strip 14 is arranged between the middle detachable passage door 9 and the bracket 12, and considering the limitation of the installation space, it is connected by blind nuts 16 and bolts, and in order to meet the requirements of the blind nuts on the countersink thickness, an aluminum alloy reinforcement plate 15 is added; a flat rubber strip 13 is arranged between the bracket 12 and the interior decoration 2, which is connected by support plate nuts and bolts; a strip-shaped fireproof sealing toothed rubber strip 14 is arranged between the bracket 12 and the front frame belly plate 11, which is connected by support plate nuts and bolts.

[0073] The bracket 12 is a composite laminate structure, and the material used is a bidirectional prepreg glass cloth ECS2259.20 with self-extinguishing function and high temperature resistance of 180°C. The surface of the part is sprayed with primer ECS2067 and then sprayed with polyurethane fire retardant topcoat ECS2066; Figure 5 As shown, the strip-shaped fireproof sealing toothed rubber strip 14 has 4 toothed protrusions, and its material should be fire-resistant and self-extinguishing, with a compression ratio between 25% and 30% (sufficient elastic variation range can ensure that the web surface with slightly poor rigidity is sufficient to withstand the impact of flames and does not leak harmful gases); the flat rubber strip 13 is made of high-temperature resistant, glass fiber-coated chloroprene rubber ASNA4110.

[0074] like Figure 6 As shown, the lower part of the middle detachable passage door 9 is connected to the floor 3 and the front frame web 11 through an aluminum alloy angle 17; a strip-shaped fireproof sealing toothed rubber strip 14 is arranged between the middle detachable passage door 9 and the aluminum alloy angle 17; the floor 3 adopts an aluminum panel aluminum honeycomb structure; a strip-shaped fireproof sealing toothed rubber strip 14 is arranged between the left detachable passage door 8 and the front frame web 11, which is screwed together by bolts and support plate nuts; a strip-shaped fireproof sealing toothed rubber strip 14 is arranged between the middle detachable passage door 9 and the left detachable passage door 8, which is screwed together by bolts and support plate nuts.

[0075] The passage door is a composite material structure with laminated areas and honeycomb sandwich areas that meets the strength requirements. Although the materials used are all self-extinguishing, the typical structure of its composition should still be tested for 5 minutes of fire resistance in accordance with the airworthiness requirements of CCAR 29-855. According to the airworthiness instructions, aluminum alloy metal materials meet the fire resistance requirements and do not need to be tested for verification.

[0076] The selection principle of typical structural test pieces is: taking into account both weak areas and typical areas; Figure 7 , Figure 8 , Fig. 9 The typical structural forms shown in the figure have passed the 5-minute fire resistance verification test that meets airworthiness requirements.

[0077] In order to verify the fireproof sealing performance of the designed front frame channel door 5, the present invention manufactures multiple test pieces of the front frame channel door 5, namely test piece 1, test piece 2 and test piece 3. Test piece 1 is a test piece at the honeycomb position of the detachable channel door on the left and right parts of the front frame channel door 5, test piece 2 is a test piece at the lamination position of the detachable channel door on the left and right parts of the front frame channel door 5, and test piece 3 is a test piece at the position of the detachable channel door 9 in the middle part of the front frame channel door 5.

[0078] Test piece 1 is a test piece at the honeycomb position of the left and right detachable channel door of the front frame channel door 5, such as Figure 7 As shown, the size is 560mm*560mm; the honeycomb area ply is ECS2042.20(45°) / ECS2259.20(0°) / ECS2259.20(45°) / ECS2259.20(45°) / ECS2259.20(0°) / ECS2042.20(45°), and the laminated area ply is ECS2042.20(45°) / ECS2259.20(0°) / / ECS2259.20(45°) / ECS2259.20(45°) / ECS2259.20(0°) / ECS2259.20(45°) / ECS2259.20(45°) / ECS2259.20(0°) / ECS2259.20(45°) / E CS2259.20 (0°) / ECS2042.20 (45°); ECS2042.20 is a self-adhesive, self-extinguishing epoxy bidirectional glass cloth prepreg cured at 180°C, operating temperature 120°C, density 284g / m2; ECS2259.20 is a self-adhesive, self-extinguishing epoxy bidirectional glass cloth prepreg cured at 180°C, operating temperature 120°C, density 400g / m2; the honeycomb material is aramid paper honeycomb DHS251-135.15 with a thickness of 15mm and a density of 48kg / m^3; a layer of moisture-proof TELDAR film ECS0008.20 is attached to the inner surface of the honeycomb area; the surface of the parts is sprayed with primer ECS2067 and then sprayed with polyurethane fire retardant topcoat ECS2066 that meets the self-extinguishing standards.

[0079] Test piece 2 is a test piece at the lamination position of the left and right detachable channel doors of the front frame channel door 5, such as Figure 8As shown, the size is 560mm*560mm; the plies in the lamination area are ECS2042.20(45°) / ECS2259.20(0°) / / ECS2259.20(45°) / ECS2259.20(0°) / ECS2259.20(45°) / ECS2259.20(45°) / ECS2259.20(45°) / ECS2259.20(0°) / ECS2259.20(45°) / ECS2259.20(0°) / E CS2042.20 (45°); ECS2042.20 is a self-adhesive, self-extinguishing epoxy bidirectional glass cloth prepreg with a curing temperature of 180°C, a use temperature of 120°C, a density of 284g / m2; ECS2259.20 is a self-adhesive, self-extinguishing epoxy bidirectional glass cloth prepreg with a curing temperature of 180°C, a use temperature of 120°C, a density of 400g / m2; the surface of the parts is sprayed with primer ECS2067 and then sprayed with polyurethane fire retardant topcoat ECS2066 that meets the self-extinguishing standards.

[0080] Test piece 3 is a test piece at the position of the detachable channel door 9 in the middle of the front frame channel door 5. Fig. 9 As shown, the size is 560mm*560mm; the honeycomb area ply is ECS2042.20(45°) / ECS2259.20(0°) / ECS2259.20(45°) / ECS2259.20(45°) / ECS2259.20(0°) / ECS2042.20(45°), and the laminated area ply is ECS2042.20(45°) / ECS2259.20(0°) / / ECS2259.20(45°) / ECS2259.20(45°) / ECS2259.20(0°) / ECS2259.20(45°) / ECS2259.20(45°) / ECS2259.20(0°) / ECS2259.20(45°) / E CS2259.20 (0°) / ECS2042.20 (45°); ECS2042.20 is a self-adhesive, self-extinguishing epoxy bidirectional glass cloth prepreg cured at 180°C, operating temperature 120°C, density 284g / m2; ECS2259.20 is a self-adhesive, self-extinguishing epoxy bidirectional glass cloth prepreg cured at 180°C, operating temperature 120°C, density 400g / m2; the honeycomb material is aramid paper honeycomb DHS251-142.20 with a thickness of 20mm and a density of 32kg / m^3; a layer of moisture-proof TELDAR film ECS0008.20 is attached to the inner surface of the honeycomb area; the surface of the parts is sprayed with primer ECS2067 and then sprayed with polyurethane fire retardant topcoat ECS2066 that meets the self-extinguishing standards.

[0081] After the test pieces 1, 2 and 3 were manufactured, fire resistance tests were performed.

[0082] Step 3: Fireproof seal design of rear frame passage door 6:

[0083] like Fig.10 As shown, in order to facilitate personnel to enter the cargo hold for maintenance, the front frame is designed with an upper detachable passage door 18 and a lower detachable passage door 19.

[0084] like Fig.11 As shown, the upper part of the upper detachable channel door 18 is connected to the rear frame web 20 through an aluminum alloy reinforcement 21; a flat rubber strip 13 is arranged between the upper detachable channel door 18, the interior trim 2 and the rear frame web 20 and the aluminum alloy reinforcement 21, and is connected by support plate nuts and bolts.

[0085] like Fig.12 As shown, the lower part of the upper detachable passage door 18 is connected to the lower detachable passage door 19 by means of support plate nuts and bolts, and a strip-shaped fireproof sealing toothed rubber strip 14 is arranged between the two.

[0086] like Fig.13 As shown, the upper detachable channel door 18 , the interior trim 2 and the rear frame web 20 are connected by an aluminum alloy reinforcing angle bar 22 , and a flat rubber strip 13 is arranged between the upper detachable channel door 18 , the interior trim 2 and the aluminum alloy reinforcing angle bar 22 .

[0087] like Fig.14 As shown, a flat rubber strip 13 is arranged between the lower detachable passage door 19 and the rear frame web 20, and is connected by support plate nuts and bolts.

[0088] In order to verify the fireproof sealing performance of the designed rear frame channel door 6, the present invention manufactures a plurality of test pieces of the rear frame channel door 6, namely test piece 1, test piece 2 and test piece 3. Test piece 1 is a test piece at the honeycomb position of the rear frame channel door 6, test piece 2 is a test piece at the connection position of the upper door and the lower door of the rear frame channel door 6, and test piece 3 is a test piece at the lamination position of the rear frame channel door 6.

[0089] Test piece 1 is a test piece at the honeycomb position of the rear frame channel door 6, such as Fig.15As shown, the size is 510mm*510mm; the honeycomb area ply is ECS0037-255(0°) / ECS0037-256(0°) / ECS0037-256(0°) / ECS0037-255(0°), and the laminated area ply is ECS0037-255(0°) / ECS0037-256(45°) / ECS0037-256(0°) / ECS0037-256(45°) / ECS0037-256(0°) / ECS0037-255(45°); among which, ECS0037-255 is 130℃ curing, operating temperature 70℃, density 210g / m^2, self-adhesive and self-extinguishing epoxy bidirectional glass cloth prepreg; ECS0037-256 is 130℃ curing, operating temperature 70℃, density 400g / m^2, self-adhesive and self-extinguishing epoxy bidirectional glass cloth prepreg; the honeycomb material is aramid paper honeycomb DHS251-142.08 with a thickness of 8mm and a density of 32kg / m^3; a layer of moisture-proof TELDAR film ECS0008.20 is attached to the inner surface of the honeycomb area; the surface of the parts is sprayed with primer ECS2067 and then sprayed with polyurethane fire retardant topcoat ECS2066 that meets the self-extinguishing standards.

[0090] Test piece 2 is the test piece at the connection position between the upper door and the lower door of the rear frame channel door 6. Fig.16 The figure shows a typical test piece of the upper door and lower door connection form, the connecting bolts are titanium alloy bolts A0164TK050S018X, the support plate nuts are stainless steel nuts 52358CB050N, and the strip-shaped fireproof sealing toothed rubber strip 14 is used to seal between the connecting parts. Fig.17 for Fig.16The typical structural layup of the honeycomb sandwich of the upper and lower doors of the channel door 6 shown in the figure, the test piece size is 560mm*560mm, the honeycomb area layup is ECS0037-255(0°) / ECS0037-256(0°) / ECS0037-256(0°) / ECS0037-255(0°), and the laminated area layup is ECS0037-255(0°) / ECS0037-256(45°) / ECS0037-256(0°) / ECS0037-256(45°) / ECS0037-256(0°) / ECS0037-255(45°); wherein , ECS0037-255 is a self-adhesive and self-extinguishing epoxy bidirectional glass cloth prepreg cured at 130℃, operating temperature 70℃, density 210g / m^2; ECS0037-256 is a self-adhesive and self-extinguishing epoxy bidirectional glass cloth prepreg cured at 130℃, operating temperature 70℃, density 400g / m^2; the honeycomb material is aramid paper honeycomb DHS251-142.08 with a thickness of 8mm and a density of 32kg / m^3; a layer of moisture-proof TELDAR film ECS0008.20 is attached to the inner surface of the honeycomb area; the surface of the part is sprayed with primer ECS2067 and then sprayed with polyurethane fire retardant topcoat ECS2066 that meets the self-extinguishing standards.

[0091] Test piece 3 is a test piece at the lamination position of the rear frame channel door 6, such as Fig.18 As shown, the size of the test piece is 560mm*560mm; the ply in the lamination area is ECS0037-255(45°) / ECS0037-256(0°) / ECS0037-256(0°) / ECS0037-256(45°) / ECS0037-256(0°) / ECS0037-255(45°); among which, ECS0037-25 5 is a self-adhesive and self-extinguishing epoxy bidirectional glass cloth prepreg that is cured at 130℃, used at 70℃, has a density of 210g / m^2; ECS0037-256 is a self-adhesive and self-extinguishing epoxy bidirectional glass cloth prepreg that is cured at 130℃, used at 70℃, has a density of 400g / m^2; the surface of the parts is sprayed with primer ECS2067 and then sprayed with polyurethane fire retardant topcoat ECS2066 that meets the self-extinguishing standards.

[0092] like Fig.15 , Fig.16 , Fig.17 , Fig.18 , Fig.19 As shown in the figure, the typical structural forms shown in the figure have passed the 5-minute fire resistance verification test in accordance with airworthiness requirements;

[0093] Step 4: Fireproof sealing design of cargo door 4:

[0094] like Fig.19As shown, the fireproof sealing strip 24 is used between the cargo door 4 and the door frame 23 to achieve the fireproof sealing function, and the interior decoration 2 and the door frame 23 are screwed together; the fireproof sealing strip 24 is a hollow O-ring structure. Considering the limitation of its molding process after adding the fireproof cloth, it is cut at a 45° bevel angle in the middle of the left and right sides of the door, and is divided into two parts, upper and lower; Fig. 20 As shown, the upper part 25 of the fireproof sealing strip is bonded to the door frame 23 to achieve a better sealing effect (the sealing contact surface is away from one side of the door frame to avoid the strip from moving during the closing process of the cabin door), and the lower part 26 of the fireproof sealing strip is bonded to the cargo door 4 to avoid wear of the strip during the loading of goods; during assembly, the upper part 25 of the fireproof sealing strip and the lower part 26 of the fireproof sealing strip should be ensured to have no gap.

[0095] Step 5: Fireproof seal design of cargo door sealing strip:

[0096] (1) Fig.21 As shown, it is ensured that the huge deformation of the cargo hold door will not cause the failure of the connection between the sealing strip and the door, thereby causing new oxygen to enter the cargo hold and making the flame burn more fiercely; the pressure difference on both sides of the sealing strip will not cause the failure of the connection between the sealing strip and the door, thereby causing new oxygen to enter the cargo hold and making the flame burn more fiercely.

[0097] A. Extrusion of cargo door seal strip under normal conditions (e1):

[0098] Assumption: There is no pressure difference on both sides of the sealing strip (P1 = P2). When the cargo door is closed, the compression of the sealing strip is:

[0099] e1=Hs–H1

[0100] Hs: rubber strip height; H1: rubber strip compression height;

[0101] B. Displacement of cargo door under negative pressure conditions (dep2):

[0102] Assumption: Under negative pressure conditions, the edge of the cargo door reaches the maximum displacement along the H1 direction.

[0103] Referring to the strength calculation report, under a certain limit load (F1), the finite element analysis will provide the maximum displacement value (dep1) of the edge of the cargo door along the H1 direction:

[0104] The maximum negative pressure value of the hatch is P2 = (1 / 2) Cp*ρ*V2;

[0105] ρ is air density; S is the surface area of ​​the cargo door; V is the air velocity;

[0106] Therefore, when subjected to pressure P2, the limit load F2 on the cargo door is:

[0107] F2=P2*S,

[0108] When the hatch is subjected to the maximum negative pressure, the edge displacement along the H1 direction is the largest, and the ratio dep2 is:

[0109] dep2=(F2 / F1)*dep1,

[0110] Taking into account some factors, the door and the structure will not fit perfectly, and the assembly error is 1mm according to experience:

[0111] dep3=dep2+1,

[0112] C. Remaining compression of cargo door sealing strip under negative pressure (e2):

[0113] Under negative pressure, the compression of the cargo door seal is reduced due to the displacement of the door in the H1 direction:

[0114] e2=e1–dep2

[0115] When subjected to maximum negative pressure, the residual compression of the cargo door sealing strip e2 ≥ 1 ~ 2mm can ensure effective sealing.

[0116] (2) Fig. 22 As shown, the pressure difference on both sides of the sealing strip will not cause failure of the connection between the sealing strip and the door: when the deformation of the cargo hold door at both ends reaches a certain value, no failure will occur; the pressure difference on both sides of the sealing strip causes the sealing strip to twist and deform.

[0117] A comparative analysis is necessary to demonstrate that the sealing strip will not rotate about its axis, causing failure of the connection between the sealing strip and the door.

[0118] A. Due to the different pressures P2 / P1, the load on the sealing strip is limited (Fdep):

[0119] Under maximum negative pressure, considering that the cargo door is not at the same height as the structure, the distance H2 between the door and the structure is:

[0120] H2=H1+dep3,

[0121] Therefore, the limit load Fdep acting on the sealing strip, when P1 = 0:

[0122] Fdep=P2*H2,

[0123] B. Due to the different pressures P2 / P1, the load on the sealing strip is limited (Fdep):

[0124] In order to calculate the friction force Ffric of the rubber strip, it is necessary to calculate the reaction force Fps acting on the sealing strip; Fps is the inherent mechanical property of the rubber strip, which is related to the material of the rubber strip itself and its deformation. The reaction force of the rubber strip is queried according to the residual compression e2 of the sealing strip (the rubber strip manufacturer will provide the reaction force-displacement curve of the rubber strip obtained by using a press test):

[0125] Ffric=Fps*Cf,

[0126] Cf: friction coefficient;

[0127] When the maximum pressure difference between the inner and outer sides of the rubber strip is borne, the condition for the rubber strip connection not to fail is:

[0128] Ffric>Fdep,

[0129] Step 6: Design of air convection path inside the cargo hold:

[0130] Two Φ6mm process holes on the left and right sides of the cargo hold floor are used to ensure a small amount of air flow at the bottom of the helicopter. The small holes in these areas ensure a small amount of air flow at the bottom of the helicopter. They are not sealed and will not affect the sealing of the cargo hold.

[0131] Sealant should be used between all the above assembly surfaces, rivets at non-electrical overlaps should be dipped in sealant and riveted, and sealants should be used to seal the heads or tails of bolts; fireproof sealing rings or fireproof sealing foam should be used to plug all system penetration holes; composite parts are sprayed with fireproof paint; sealing strips are made of high-temperature resistant elastic rubber; and the covers are installed and fixed with fire-resistant steel bolts.

[0132] The above only expresses the implementation mode of the present invention, and its description is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. In addition, the parts not detailed in the present invention are all conventional technologies.

Claims

1. A method for designing a fireproof sealed cargo hold, characterized in that: include: In the first step, the interior, floor, cargo door, front frame passage door and rear frame passage door are surrounded by a fireproof sealing boundary; The second step is to carry out the fireproof sealing design of the front frame passage door and complete the fireproof and fire resistance test; The third step is to carry out the fireproof sealing design of the rear frame passage door and complete the fireproof and fire resistance test; The fourth step is to carry out the fireproof sealing design of the cargo door and complete the fireproof and fire resistance test; The fifth step is to design the air convection path inside the cargo hold.

2. The method according to claim 1, characterized in that The front frame passage door includes a left detachable passage door, a middle detachable passage door, and a right detachable passage door; The upper part of the middle detachable passage door is connected to the interior decoration and the front frame web through a bracket; an annular fireproof sealing toothed rubber strip is arranged between the middle detachable passage door and the bracket; a flat rubber strip is arranged between the bracket and the interior decoration; and a strip-shaped fireproof sealing toothed rubber strip is arranged between the bracket and the front frame web; The lower part of the middle detachable passage door is connected to the floor and the front frame web through an aluminum alloy angle bar; a strip-shaped fireproof sealing toothed rubber strip is arranged between the middle detachable passage door and the aluminum alloy angle bar; the floor adopts an aluminum panel aluminum honeycomb structure; a strip-shaped fireproof sealing toothed rubber strip is arranged between the left detachable passage door and the front frame web; a strip-shaped fireproof sealing toothed rubber strip is arranged between the middle detachable passage door and the left detachable passage door; When conducting fire prevention and fire resistance tests, test pieces are used for testing. The test pieces are made according to the strength of different areas of the front frame channel door. The test pieces are made of two types of carbon cloth, ECS2259.20 and ECS2042.20, laid alternately. The outer surface of the test piece is sprayed with polyurethane fire retardant topcoat.

3. The method according to claim 1, characterized in that The rear frame passage door includes an upper detachable passage door and a lower detachable passage door; The upper part of the upper detachable channel door is connected to the rear frame web through an aluminum alloy reinforcement; a flat rubber strip is arranged between the upper detachable channel door, the interior decoration, the rear frame web and the aluminum alloy reinforcement; The lower part of the upper detachable passage door is connected to the lower detachable passage door, and a strip-shaped fireproof sealing toothed rubber strip is arranged between the two; The upper detachable passage door, the interior trim and the rear frame belly plate are connected by aluminum alloy reinforcing angle bars, and flat rubber strips are arranged between the upper detachable passage door, the interior trim and the aluminum alloy reinforcing angle bars; A flat rubber strip is arranged between the lower detachable passage door and the rear frame belly plate; When conducting fire prevention and fire resistance tests, test pieces are used for testing. The test pieces are made according to the strength of different areas of the rear frame channel door. The test pieces are paved with ECS0037, and the outer surface of the test pieces is sprayed with polyurethane fire retardant paint.

4. The method according to claim 1, characterized in that: An O-type fireproof sealing strip is installed between the cargo door and the door frame, and the interior trim is screwed to the door frame; the O-type fireproof sealing strip is cut at a 45° bevel angle in the middle of the door to separate it into two parts, the upper part is bonded to the door frame, and the lower part is bonded to the cargo door body; When conducting fire prevention and fire resistance tests, test pieces are used for testing. The test pieces are made according to the strength of different areas of the cargo door 4. The test pieces are paved with ECS0017.108 and ECS2042.20, and the outer surface of the test pieces is sprayed with polyurethane fire retardant topcoat.

5. The method according to claim 4, characterized in that The fireproof seal design process of O-type fireproof seal strip under negative pressure is: Step 1, calculate the compression amount e1 of the O-type fireproof sealing strip: compression amount e1 = Hs-H1, where Hs is the strip height; H1 is the strip height after compression; Step 2, calculate the displacement dep2 of the cargo door under negative pressure conditions and calculate the target displacement dep3: displacement dep2 = (F2 / F1)*dep1, where F1 is the limit load, F2 = P2*S, P2 = (1 / 2)Cp*ρ*V2, Cp is the value given in the load manual under the maximum negative pressure value P2 of the cabin door, ρ is the air density, V is the air flow velocity, S is the surface area of ​​the cargo door, dep1 is the maximum displacement of the edge of the cargo door along the H1 direction; target displacement dep3 = dep2+1; Step 3: Calculate the remaining compression amount e2 of the O-type fireproof sealing strip under negative pressure: e2 = e1 – dep2; Step 4: When the residual compression amount e2 is ≥ 1-2 mm under the maximum negative pressure, it is determined that the fireproof seal of the O-type fireproof sealing strip is effective.

6. The method according to claim 1, characterized in that In the fifth step, When there are unblocked mounting holes on the left and right floors inside the cargo hold, the mounting holes are used as air convection holes; otherwise, air convection holes are drilled on the floor inside the cargo hold to ensure a small amount of air flow at the bottom of the helicopter.

7. A fireproof sealed cargo hold designed by the method according to any one of claims 1 to 6, characterized in that: include: The front frame passage door, rear frame passage door, cargo hold door, and air convection holes on the floor inside the cargo hold, The front frame passage door is located on the reinforced frame of the cabin, the rear frame passage door is located on the reinforced frame of the tail beam, and the cargo hold door is located on the cargo hold skin.

8. The fireproof sealed cargo hold according to claim 7, characterized in that: The front frame passage door includes a left detachable passage door, a middle detachable passage door, and a right detachable passage door; The upper part of the middle detachable passage door is connected to the interior decoration and the front frame web through a bracket; a strip-shaped fireproof sealing toothed rubber strip is arranged between the middle detachable passage door and the bracket; a flat rubber strip is arranged between the bracket and the interior decoration; a strip-shaped fireproof sealing toothed rubber strip is arranged between the bracket and the front frame web; The lower part of the middle detachable passage door is connected to the floor and the front frame web through an aluminum alloy angle; a strip-shaped fireproof sealing toothed rubber strip is arranged between the middle detachable passage door and the aluminum alloy angle; the floor adopts an aluminum panel aluminum honeycomb structure; a strip-shaped fireproof sealing toothed rubber strip is arranged between the left detachable passage door and the front frame web; a strip-shaped fireproof sealing toothed rubber strip is arranged between the middle detachable passage door and the left detachable passage door.

9. The fireproof sealed cargo hold according to claim 7, characterized in that: The rear frame passage door includes an upper detachable passage door and a lower detachable passage door; The upper part of the upper detachable channel door is connected to the rear frame belly plate through an aluminum alloy reinforcement; a flat rubber strip is arranged between the upper detachable channel door, the interior trim, the rear frame belly plate and the aluminum alloy reinforcement; The lower part of the upper detachable passage door is connected to the lower detachable passage door, and a strip-shaped fireproof sealing toothed rubber strip is arranged between the two; The upper detachable channel door, the interior trim and the rear frame belly plate are connected by aluminum alloy reinforcing angle bars, and flat rubber strips are arranged between the upper detachable channel door, the interior trim and the aluminum alloy reinforcing angle bars; A flat rubber strip is arranged between the lower detachable passage door and the belly plate of the rear frame.

10. The fireproof sealed cargo hold according to claim 7, characterized in that: An O-type fireproof sealing strip is installed between the cargo door and the door frame, and the interior decoration and the door frame are screwed together; the O-type fireproof sealing strip is cut at a 45° angle in the middle of the door and is divided into two parts, the upper part is bonded to the door frame, and the lower part is bonded to the cargo door body.

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