Polyethylene film airship inflatable empennage and manufacturing method

Abstract

The invention discloses a polyethylene film airship inflation empennage which is characterized by comprising a spherical film made of a polyethylene film. The reinforcing ribs are used for tightening the ball film; the interlayer is welded in the spherical membrane cavity and extends longitudinally, and the longitudinal direction refers to the direction from the root of the empennage to the end of the empennage; and a plurality of interlayers are transversely arranged in the spherical membrane cavity. The invention further discloses a manufacturing method of the polyethylene film airship inflatable empennage. The problem that a polyethylene film cannot resist high pressure is solved.

Description

Technical Field

[0001] The present application relates to the field of near-space aerostat design, and in particular to the design of an aerostat tail structure. Background Art

[0002] Aerostats fly by filling their interior with gas that is lighter than air, including airships, tethered balloons and free balloons. One of the current development directions of airships is stratospheric high-altitude airships. Stratospheric airships have received much attention among near-space flight platforms. Unlike free balloons, they can fly with power and obtain certain trajectory control capabilities, which makes them have important application value and broad development prospects. At present, stratospheric airships are mostly made of fabric skin materials, which obtain rigidity after withstanding the internal and external pressure difference at the ceiling altitude. However, the membrane surface density of traditional fabric airships is relatively large, and the design is simply similar to the early development of superpressure balloons, which rely on the film itself to resist the pressure difference.

[0003] The heavy weight of the capsule increases the cost of each process including manufacturing, folding and transportation, pressure-maintaining and unfolding, and distribution.

[0004] The polyethylene film airship integrates super-pressure balloon technology into the airship design, uses polyethylene film as the airship bladder material, and uses warp and circumferential reinforcement ribs to withstand stress. The hull shape is modified to form a water drop streamline to reduce resistance, so as to overcome a series of problems caused by the deadweight of the bladder during the production, pressure maintenance and release of the fabric airship, increase the flight altitude, and increase the load carrying capacity. The polyethylene film airship can be an effective supplement to traditional fabric airships and super-pressure balloons, and has great application value in long-duration flight and regional residence.

[0005] The tail fin plays an important role in the stability and control of the airship. The hull alone does not have attitude stability.

[0006] Since the main airbag of the polyethylene film airship is made of an extremely thin polyethylene film structure, a hard tail structure cannot be installed, and only a flexible inflatable tail structure can be tied. At the same time, the tail must also be made of polyethylene film. This makes the design of a polyethylene tail structure with overpressure resistance a major technical challenge for the polyethylene film airship. Summary of the invention

[0007] The present application proposes a polyethylene film airship inflatable tail and a manufacturing method to solve the problem that the polyethylene film cannot withstand high pressure.

[0008] On the one hand, an embodiment of the present application proposes an inflatable tail wing of a polyethylene film airship, comprising: a spherical membrane made of polyethylene film; reinforcing ribs for restraining the spherical membrane; and a longitudinally extending partition welded in the spherical membrane cavity, wherein the longitudinal direction refers to the direction from the root of the tail wing to the end of the tail wing; a plurality of partitions are arranged horizontally in the spherical membrane cavity.

[0009] In one embodiment of the present application, the structure of the tail wing is a longitudinal stack of columns that are bounded by multiple circles of circumferential reinforcing ribs, and the longitudinal reinforcing ribs are connected at multiple designated points between longitudinally adjacent columns.

[0010] In one embodiment of the present application, a space is reserved at the bottom of the tail wing for the main airbag bulge to expand, so that the bottom of the tail wing is conformal to the meridian bulge of the main airbag.

[0011] In one embodiment of the present application, the tail wing is provided with a plurality of longitudinal reinforcing ribs, and the longitudinal reinforcing ribs are used for consolidation with the main airbag reinforcing ribs at the root of the tail wing.

[0012] In one embodiment of the present application, the partition is in the shape of a rectangle, an isosceles trapezoid or an isosceles triangle.

[0013] In one embodiment of the present application, the tail wing film has longitudinal wrinkles.

[0014] In one embodiment of the present application, the spherical membrane is deformed when subjected to the internal and external pressure difference, and the maximum force on the partition is in the middle of the bottom of the tail wing.

[0015] On the other hand, an embodiment of the present application also proposes a method for manufacturing an inflatable tail of an ethylene film airship to manufacture the inflatable tail of an ethylene film airship described in any embodiment of the present application, the method comprising the following steps: making a spherical membrane with a polyethylene film; tightening the spherical membrane with reinforcing ribs to withstand the internal and external pressure difference; and welding a longitudinally extending partition in the spherical membrane cavity.

[0016] Furthermore, the mass point discretization method of the three-dimensional triangular membrane element is used to analyze the layout of the partition and the reinforcement, satisfying at least one of the following conditions:

[0017] Maximum internal and external pressure difference of the tail wing;

[0018] Weld the interlayer at the location with less longitudinal force;

[0019] When the tail is kept flat, the longitudinal force is smaller than the lateral force.

[0020] Further, in one embodiment of the present application, longitudinal reinforcement ribs are connected at designated points between adjacent columnar bubbles of the tail wing to maintain the geometric shape of the tail wing, and / or, the tail wing is mounted on the longitudinal bulge at the rear of the main airbag, and the mounting method is that the tail wing reinforcement ribs and the main airbag reinforcement ribs are consolidated at the bottom;

[0021] Furthermore, in one embodiment of the present application, a stiffness test and a pressure test are performed on the tail wing.

[0022] At least one of the above technical solutions adopted in the embodiments of the present application can achieve the following beneficial effects:

[0023] The present invention is different from the previous inflatable tail design. It uses the reinforcement ribs to hold the polyethylene film to bear the internal and external pressure difference, and uses ropes to connect the common contact surface of the bubbles to maintain the geometric airfoil of the tail. The tail configuration of this cable membrane structure can be easily tied to the longitudinal and circumferential reinforcement ribs of the polyethylene airship. In addition, the assembly of multiple bubbles improves the rigidity of the tail itself, which has many beneficial effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0025] Figure 1 This is a schematic diagram of the polyethylene film airship and tail structure in the application scenario of this application scheme;

[0026] Figure 2 This is a flow chart of an embodiment of the method of this application;

[0027] Figure 3 is the initial calculated shape of the tail;

[0028] Figure 4.a is the deformation change of the tail wing;

[0029] Figure 4.b It is the shape of the tail fin assembled on the airship, the rear view;

[0030] Figure 4.c It is the shape of the tail fin assembled on the airship, side view;

[0031] Figure 5 is the stress condition of the longitudinal partition;

[0032] Figure 6 is the meridional and circumferential stress of the bottom bulge;

[0033] Figure 7.a It is the shape of the large bubble plane cut film on the upper part of the tail wing;

[0034] Figure 7.b It is the shape of the large bubble plane cut film in the middle of the tail wing;

[0035] Figure 7.c It is the shape of the large bubble plane cut film at the lower part of the tail wing;

[0036] Figure 8 Final film shape;

[0037] Fig. 9 The shape of the membrane cut on the diaphragm plane after fitting;

[0038] Fig.10 The finished polyethylene inflatable tail structure. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described below in combination with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

[0040] In view of the shortcomings of the existing technology, this patent solves the problem of installing an inflatable tail at the tail of a polyethylene film airship to achieve airship stability and good maneuverability.

[0041] The technical solutions provided by various embodiments of the present application are described in detail below in conjunction with the accompanying drawings.

[0042] Figure 1 This is a schematic diagram of the polyethylene film airship and tail structure in the application scenario of the present application. The present application embodiment proposes an inflatable tail of a polyethylene film airship, including: a spherical membrane made of polyethylene film; reinforcing ribs for holding the spherical membrane; and a longitudinally extending partition welded in the spherical membrane cavity, wherein the longitudinal direction refers to the direction from the root of the tail to the end of the tail; a plurality of partitions are arranged laterally in the spherical membrane cavity. To ensure the cleanliness of the structure, the film used is still 38μm polyethylene film. The method of maintaining the shape of the tail is still to use ropes (3mm reinforcing ribs) to hold the spherical membrane to withstand the internal and external pressure difference, and to weld the partition at a position with less longitudinal force. The initial tail shape is as follows Figure 3 shown.

[0043] In one embodiment of the present application, the structure of the tail wing is a longitudinal stack of cylinders that are bounded by multiple circles of circumferential reinforcing ribs, and the longitudinal reinforcing ribs are connected at multiple designated points between the longitudinally adjacent cylinders. The basic design idea of ​​the tail wing is to stack cylinders up and down with circles of circumferential reinforcing ribs, and connect the longitudinal reinforcing ribs at designated points between the upper and lower adjacent cylinders. That is, the traditional tail wing is constrained by the interlayer line, while the polyethylene cable membrane tail wing is constrained by the point of the reinforcing ribs. In addition, in order to maintain the flat shape of the tail wing, the longitudinal force is smaller than the lateral force, and a partition is further installed in the longitudinal direction of the tail wing.

[0044] It can be understood that the circumferential direction of the tail wing refers to a direction substantially perpendicular to the longitudinal direction. Preferably, the circumferential section of the tail wing is parallel to the axial direction of the main airbag.

[0045] In one embodiment of the present application, a space is reserved at the bottom of the tail wing for the main airbag bulge to expand, so that the bottom of the tail wing is conformal to the meridian bulge of the main airbag.

[0046] In one embodiment of the present application, the tail wing is provided with a plurality of longitudinal reinforcing ribs, and the longitudinal reinforcing ribs are used for consolidation with the main airbag reinforcing ribs at the root of the tail wing.

[0047] It should be noted that Figure 3 It is a schematic diagram of the tail structure, and is also the initial shape of the tail deformation shape simulation calculation.

[0048] The bottom generatrix is ​​the generatrix after the deformation of the warp reinforcement ribs of the main airbag. The material of the bottom of the tail wing can be directly interpolated according to the shape of the main airbag bulge. The designed tail wing adopts the upper, middle and lower three airbag structures. The bottom airbag can level the uneven tail area of ​​the main airbag in the height direction to facilitate the design and installation of the upper and middle airbags. The bottom contains 8 small bulges, corresponding to the two large bulges of the main airbag. Since the tail wing also needs to fit the main airbag bulge in the circumferential direction, the bottom airbag adopts a triangular structure at the leading and trailing edges. Here, the circumference of the main airbag is the direction around the axis of the main airbag. The base of the triangle is the circumferential length of the main airbag bulge, and the vertices of the triangle are the straight lines of the leading and trailing edges of the upper and middle airbags. The upper and middle airbags need to realize the function of the hypotenuse of the leading edge of the tail wing, so the leading edge bulge is no longer a quadrilateral structure, but a triangular bulge shape, and the upper airbag has only 7 bulges. In addition, the top of the tail wing also needs to be sealed. The initial shape is a plane, but there are only 6 bulges (including 1 triangular bulge). Therefore, the tail wing structure has a total of (8+2)+8+7+6=31 small bulges. The discrete points of a single bulge on the tail wing are reduced to 7×7. For the rib structure, the cross nodes are fixed in the simulation, and the stiffness and diameter of the mass segment representing the rib are increased. In one embodiment of the present application, the spherical membrane deforms when subjected to the internal and external pressure difference, and the maximum force on the interlayer is in the middle of the bottom of the tail wing. The deformed tail wing after being subjected to a pressure difference of 300Pa is as follows. Figure 4.a Figures 1 to 3 show the shape of the airship tail after deformation and the shape after assembly on the airship. Figure 5 and Figure 6 shown.

[0049] Figure 5 is the stress of each interlayer, indicating that the interlayer stress is much smaller than the yield strength of the film. Among them, it can be concluded that the maximum stress of the spherical membrane is also 2.5MPa at the middle position of the bottom. The maximum stress of the interlayer is in the middle airbag and the upper airbag, and the maximum is only 0.01MPa, which means that the stress of the interlayer film is greatly reduced compared with the stress when only the longitudinal diaphragm is used without the reinforcement ribs to constrain the tail wing. The horizontal axis in the figure is the number of the selected discrete nodes, and the vertical axis is the diaphragm stress (Pa). According to the number of each diaphragm, the location of the diaphragm can be seen Figure 3 .

[0050] Figure 6The circumferential and longitudinal stress distribution of the film including the top airbag. The 14 curves correspond to the 7 bulges formed by the longitudinal reinforcement ribs of the top airbag. The 5 curves in each figure represent the stress at the intersection of the unit constrained by the 5 circumferential reinforcement ribs and the longitudinal reinforcement ribs. It can be concluded that the stress on the film is much smaller than the yield strength stress (10MPa).

[0051] In one embodiment of the present application, the partition is in the shape of a rectangle, an isosceles trapezoid or an isosceles triangle.

[0052] In one embodiment of the present application, the tail film has longitudinal wrinkles. During processing, the film cutting pattern of three large bubbles is as follows Figure 7.a The figure shows the cutting pattern of the tail film, which corresponds to the upper, middle and lower three large bubbles respectively.

[0053] Since the designed tail wing is an assembled structure, the three airbags at the top, middle and bottom need to be welded and sealed during processing. The method for obtaining the plane film cutting shape of the tail wing is still determined according to the solved transverse and longitudinal mass segment lengths. Taking the most complex bottom airbag film cutting shape as an example, the film cutting pattern is shown in Figure 7. Since the tail wing is a front-to-back symmetrical structure, the upper midline of the bottom airbag is used as the symmetry axis of the film cutting pattern. From the upper midline downward, the spherical film material of half the upper surface, the front of the airbag, and half the bottom of the airbag is passed in turn. Calculate from the first longitudinal line of the first small bulge on the right to the left. First, calculate the length of the current longitudinal line y(n), n is the current longitudinal line number, and then calculate the distance x(n,i) between each mass point on the longitudinal line and the corresponding mass point of the next column of longitudinal lines in turn, i is the mass point number on the longitudinal line, i=1~7, and add the longest distance max(x(n,i)) to the current longitudinal line position to obtain the position of the next film cutting longitudinal line. Finally, the film cutting shapes of 8 small bulges are obtained, as shown by the vertical black thin lines in the figure. In addition, the bottom airbag needs to add front and rear triangular film cutting patterns. At this time, the vertical line is a line segment starting from the vertex of the triangle, and the horizontal distance is equivalent to the deflection angle, that is, the maximum vertex deflection angle corresponding to the distance between the corresponding mass points of each line segment. The middle and upper airbags adopt the same film cutting method, but it should be noted that the film cutting shape of the head is a triangle due to the oblique line of the leading edge of the tail wing.

[0054] The tail wing film cutting pattern after edge fitting is as follows Figure 8 As shown. The tail film has extra wrinkles. Specifically, the film shape is required to be as smooth as possible without wavy shapes during processing, and the edge of the obtained film pattern needs to be fitted. The fitting curve is shown in the figure, where the discrete points are Figure 7.aThe material required for the vertical line obtained in ~c. The fitting curve used is of lower order, which is a quadratic and cubic polynomial curve. Unlike the main airbag film cutting, the tail wing film cutting not only needs to fit the edges, but also the positions containing the transverse reinforcement ribs inside, and the excess material of the spherical film is obtained by subtracting the fitted position from the original position. It can be seen from the film cutting curve that there is a lot of residual material at the leading edge of the tail wing, especially at the bottom of the triangular leading edge. The remaining material of the airfoil on each airbag is less than that on the bottom, so that after the tail is inflated and maintains the same pressure difference, the spherical film below the upper airbag may extend into the top of the middle airbag. Similarly, the excess spherical film below the middle airbag will extend into the top of the lower airbag.

[0055] Figure 2 This is a flow chart of an embodiment of the method of the present application, which includes the following steps 210-250.

[0056] Step 210: Make a spherical membrane using a polyethylene film.

[0057] Step 220: Use reinforcing ribs to tighten the spherical membrane to withstand the internal and external pressure difference.

[0058] Preferably, the mass particle discretization method of the three-dimensional triangular membrane unit is used to analyze the layout of the stiffeners to meet the maximum internal and external pressure difference of the tail wing.

[0059] Step 230: welding a longitudinally extending partition in the spherical membrane cavity.

[0060] Preferably, the mass particle discretization method of the three-dimensional triangular membrane unit is used to analyze the layout of the partitions, and the partitions are welded at positions with smaller longitudinal forces, so that the longitudinal forces are smaller than the lateral forces while maintaining the flat shape of the tail wing.

[0061] It should be noted that the polyethylene tail structure optimization analysis method uses the mass particle discretization method of the three-dimensional triangular membrane unit. Since the overall size of the tail is much smaller than the main airbag, even if it is designed according to the elastic modulus of the structure itself, it will not reach the 10MPa yield strength. In other words, the tail is easy to meet the strength requirements, but the reasonable arrangement of the partitions and reinforcement ribs is required to maintain the shape.

[0062] It can be concluded that the maximum force on the interlayer is 2.5MPa at the middle of the bottom when the internal pressure is 300Pa. The maximum force on the spherical membrane is also 2.5MPa at the middle of the bottom. It is expected that the maximum pressure difference of the tail wing can reach 1000Pa.

[0063] Step 240: Assemble the tail wing components and install the main airbag.

[0064] Furthermore, in one embodiment of the present application, longitudinal reinforcement ribs are connected at designated points between adjacent columnar bubbles of the tail wing to maintain the geometric shape of the tail wing.

[0065] When the main airbag is installed, the tail wing is installed on the longitudinal bulge at the rear of the main airbag, and the installation method is that the tail wing reinforcement ribs and the main airbag reinforcement ribs are consolidated at the bottom;

[0066] Preferably, the tail wing airfoil is a wider NACA0024 symmetrical airfoil. For example, it is installed on the second and third radial bulges from the main airbag. The installation method is that the tail wing reinforcement ribs and the main airbag reinforcement ribs are consolidated at the bottom. At the same time, space is reserved at the bottom of the tail wing for the second to third bulges of the main airbag to be fully expanded.

[0067] Step 250: In one embodiment of the present application, a stiffness test and a pressure test are performed on the tail wing.

[0068] It can be concluded that the shape of each longitudinal partition film is as follows Fig. 9 As shown in the figure, the shapes and sizes of the 20 diaphragms determine the shape of the entire tail. According to the serial number of each diaphragm, the location of the diaphragm is shown in the figure. Figure 3 The horizontal coordinate of each membrane image is the width of the membrane, and the vertical coordinate is the height of the membrane, and the unit is meter (m).

[0069] The finished polyethylene tail structure is as follows Fig.10 As shown in the figure, this figure is a photo of the actual tail shape produced.

[0070] It should also be noted that the terms "include", "comprising" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of further restrictions, the elements defined by the sentence "comprising..." do not exclude the presence of other identical elements in the process, method, commodity or device including the elements.

[0071] It will be understood by those skilled in the art that, unless otherwise stated, the singular forms "a", "an", "said" and "the" used may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. The term "and / or" used herein includes all or any unit and all combinations of one or more associated listed items.

[0072] Those skilled in the art will understand that unless otherwise defined, all terms (including technical, technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which this invention belongs.

[0073] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A polyethylene film airship inflatable tail, characterized in that: include: Ball membrane made of polyethylene film; A reinforcing rib, used to hold the spherical membrane; And a longitudinally extending partition welded in the spherical membrane cavity, wherein the longitudinal direction refers to the direction from the tail root to the tail end; a plurality of partitions are arranged transversely in the spherical membrane cavity.

2. The polyethylene film airship inflatable tail wing according to claim 1, characterized in that: The structure of the tail wing is a longitudinal stack of columns bounded by a plurality of circumferential reinforcing ribs, and longitudinal reinforcing ribs are connected at a plurality of designated points between longitudinally adjacent columns.

3. The polyethylene film airship inflatable tail wing according to claim 1, characterized in that: The bottom of the tail wing reserves space for the main airbag bulge after expansion, so that the bottom of the tail wing is conformal to the meridian bulge of the main airbag.

4. The polyethylene film airship inflatable tail wing according to claim 1, characterized in that: The tail wing is provided with a plurality of longitudinal reinforcing ribs, and the longitudinal reinforcing ribs are used for consolidation with the main airbag reinforcing ribs at the root of the tail wing.

5. The polyethylene film airship inflatable tail wing according to claim 1, characterized in that: The partition is in the shape of a rectangle, an isosceles trapezoid or an isosceles triangle.

6. The polyethylene film airship inflatable tail wing according to claim 1, characterized in that: The tail wing membrane has longitudinal wrinkles.

7. The polyethylene film airship inflatable tail wing according to claim 1, characterized in that: The spherical membrane deforms when subjected to the internal and external pressure difference, and the maximum force on the partition is in the middle of the bottom of the tail wing.

8. The method for manufacturing the inflatable tail of the vinyl film airship according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: a polyethylene film is made into a spherical membrane; reinforcing ribs are used to tighten the spherical membrane to withstand the internal and external pressure difference; and a longitudinally extending partition is welded in the cavity of the spherical membrane.

9. The manufacturing method according to claim 8, characterized in that: The mass point discretization method of three-dimensional triangular membrane elements is used to analyze the layout of interlayers and stiffeners, satisfying at least one of the following conditions: Maximum internal and external pressure difference of the tail wing; Weld the interlayer at the location with less longitudinal force; When the tail is kept flat, the longitudinal force is smaller than the lateral force.

10. The manufacturing method according to claim 8, characterized in that: Connecting longitudinal stiffeners at designated points between adjacent columnar bubbles of the empennage to maintain the geometric shape of the empennage, and / or, the empennage is mounted on the longitudinal bulge at the rear of the main airbag in such a way that the empennage stiffeners are consolidated with the main airbag stiffeners at the bottom; Perform stiffness and pressure tests on the tail wing.

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