Flame arrester for safely using hydrogen as lifting gas in airship
阅读说明：本技术 一种用于安全使用氢气作为飞艇中提升气体的阻火器 (Flame arrester for safely using hydrogen as lifting gas in airship ) 是由 迈克尔·伊恩·古德伊斯曼 于 2018-07-03 设计创作，主要内容包括：一种飞艇,所述飞艇包括容纳氢气的包封,该包封进一步包括沿所述包封分布的阻火器装置。该阻火器装置包括由多个网孔板制成的多个单元。所述多个单元紧邻所述包封并彼此端对端安装。(An airship including an envelope containing hydrogen gas, the envelope further including flame arrestor devices distributed along the envelope. The flame arrestor device comprises a plurality of cells made of a plurality of mesh panels. The plurality of units are mounted end-to-end with respect to each other immediately adjacent the envelope.)
1. An airship comprising an envelope containing hydrogen gas; wherein the envelope comprises flame arrestor devices distributed along the envelope; the flame arrestor device comprises a plurality of cells made of a plurality of mesh panels; the plurality of units are mounted end-to-end with respect to each other immediately adjacent the envelope.
2. The airship of claim 1, wherein the mesh panels forming the plurality of cells have between 1 and 3 mesh layers.
3. The airship of claim 1, wherein the mesh panels forming the plurality of cells are interconnected by stitching and a zipper.
4. The airship of claim 2, wherein the mesh layer is made of a material selected from the group consisting of carbon fiber tows, aluminum alloy wires, and combinations thereof.
5. The airship of claim 4, wherein the carbon fiber tow is characterized by a filament count between 1000(lk) and 12000(12 k).
6. The airship of claim 4, wherein the mesh layers are woven such that each channel has a hydraulic diameter that is less than a critical diameter of a lifting gas.
7. The airship of claim 4, wherein the mesh layer has a single or combined channel length greater than a quenching length of a lifting gas.
8. The airship of claim 4, wherein the cells are characterized by an open area ranging between 10% and 50% of a total area of the cells.
9. The airship of claim 1, wherein the cells have a size in a range between 0.5m and 8.0 m.
10. A method of manufacturing an airship; the method comprises the following steps:
a. providing an enclosure configured to contain hydrogen gas;
b. providing a flame arrestor device;
c. mounting the flame arrestor device on an inner wall of the enclosure;
d. filling the encapsulation with hydrogen;
wherein the step of the flame arrestor device comprises installing a plurality of units made of a plurality of mesh panels; the plurality of units are mounted end-to-end to each other proximate the enclosure.
11. The method of claim 10, wherein the mesh plates forming the plurality of cells have between 1 and 3 mesh layers.
12. The method of claim 10, wherein the mesh panels forming the plurality of cells are interconnected by stitching and zippers.
13. The method of claim 10, wherein the plurality of mesh panels are made of a material selected from the group consisting of carbon fiber tow, aluminum alloy wire, and combinations thereof.
14. The method of claim 10, wherein the carbon fiber tow is characterized by a filament count between 1000(lk) and 12000(12 k).
15. The method of claim 10, wherein the mesh layer is woven such that each channel has a hydraulic diameter that is less than a critical diameter of the lift gas.
16. The method of claim 10, wherein the mesh layer has a single or combined channel length that is greater than a quenching length of a lift gas.
17. The method of claim 10, wherein the mesh is characterized by an open area ranging between 10% and 50% of a total area of the mesh.
18. The method of claim 10, wherein the size of the cell is in a range between 0.5m and 8.0 m.
Technical Field
The present invention relates to an airship and more particularly to a fire-retarded airship which allows the safe use of hydrogen as a lifting gas.
Background
Airships combine the advantages of boats, airplanes, and helicopters. Airships are faster than ships, they can carry higher payloads than helicopters and use shorter take-off and landing distances than airplanes. Airship vibration levels are lower than those of aircraft and they are not affected by sea conditions or corrosive environments. Airships can transport heavy cargo to remote areas. Airship transportation systems produce low air and water pollution. This can meet challenging tasks that airplanes and helicopters cannot accommodate well. Long-term durability, low noise and vibration levels, and low vehicle acceleration provide an ideal platform for surveillance and patrolling.
Hydrogen airships were once commonly used in the early stages of the world and some airships have achieved numerous transoceanic traversals. The hydrogen airship age was terminated by the explosion of the xingdenburg airship, new jersey. The exact cause of the explosion has been debated for years, but the hydrogen lift gas at some stage mixes with the air and this mixture is ignited resulting in an explosion. Such ignition may be caused by lightning or electrostatic discharge (ESD).
The latter helium airship faces increasing challenges of limited availability of helium and increased cost. Helium gas cannot be produced at present and is in limited supply underground. Helium is also required by nuclear magnetic resonators, other cryogenic, welding, heat transfer, pressurization and purging, party balloons, leak detection, and other uses. Hydrogen can be easily produced in large quantities with today's technology.
US 6896222 discloses a lighter-than-air airship using hydrogen or other gases as the lifting gas, having at least one on-board hydrogen fuel cell. The fuel cell is capable of drawing hydrogen fuel from the lift gas reservoir to generate electricity for use by the airship and optionally for propulsion. The waste product of a fuel cell is water, which can be used for the needs of the crew on the airship. The hydrogen lift chamber is surrounded by an inert gas filled safety sheath and contains optional hydrogen and/or oxygen sensors.
Creating an additional safety sheath and filling it with inert gas complicates the layout of the airship and reduces the power rise. Therefore, there is a long felt and unmet need to provide a technically simple fire-resistant airship using (flammable) hydrogen as its lifting gas.
Disclosure of Invention
The present invention is based on the same method used to safely provide early miners with gas lamps (davit lamps). The flame of the davit lamp is surrounded by a metal gauze. Any gas leakage through the flame will only burn in the area of the gauze. The gas does not spread to the surrounding coal mine, so larger, potentially lethal, combustions are avoided. The first flame arrestor was a davenport lamp.
The invention allows the airship to have its envelope filled with hydrogen (combustible lift gas). The enclosure includes flame arrestor devices distributed along an interior surface of the enclosure. The flame arrestor device comprises a plurality of cells made of a plurality of mesh panels. The plurality of units are mounted end-to-end with respect to each other immediately adjacent the envelope. Each cell can be considered to be an enlarged scale (and without a permanent flame burning) davit lamp with a plurality of mesh plates of carbon fiber, aluminum alloy or other suitable material.
The mesh plates forming the plurality of cells are connected to each other by sewing and a zipper.
The mesh plate consists of between 1 and 3 mesh layers. The mesh layer is made of woven carbon fibre tows (which will consist of 1000 to 12000 monofilaments) or aluminium alloy wire or other suitable material.
The gaps between the carbon fibre tows (or aluminium alloy filament) are generally no more than 0.40mm (and never more than 1mm) in the weft (longitudinal tows or filaments) or in the warp (transverse tows or filaments) or both.
It is therefore an object of the present invention to disclose an airship including an envelope containing hydrogen, a combustible lifting gas.
It is a core object of the present invention to provide the envelope with a flame arrestor device distributed along the envelope. The flame arrestor device comprises a plurality of cells made of a plurality of mesh panels. The plurality of units are mounted end-to-end with respect to each other immediately adjacent the envelope.
It is another object of the invention to disclose the plurality of mesh plates forming the plurality of cells having between 1 and 3 mesh layers.
It is another object of the present invention to disclose the mesh panels forming the plurality of cells, interconnected by stitching and zippers.
It is another object of the present invention to disclose the plurality of mesh layers made of a material selected from the group consisting of carbon fiber tows, aluminum alloy wires, and combinations thereof.
It is a further object of the present invention to disclose the carbon fiber tow as characterized in that the number of filaments is between 1000(lk) and 12000(12 k).
It is a further object of the present invention to disclose weaving the mesh layer such that each channel has a hydraulic diameter less than the critical diameter of the lift gas.
It is a further object of the invention to disclose the mesh layer having a single or combined channel length greater than the quenching length of the lift gas.
It is a further object of this invention to disclose such a mesh layer, wherein said mesh layer is characterized by an open area ranging between 10% and 50% of the total area of said mesh layer.
It is a further object of the invention to disclose the length of the cell edge, which is in the range between 0.5m and 8.0 m.
It is a further object of the invention to disclose a method of manufacturing an airship. The method comprises the following steps: (a) providing an enclosure configured to contain hydrogen gas; (b) providing a flame arrestor device; (c) mounting the flame arrestor device on an inner surface of the envelope; (d) the encapsulation is filled with hydrogen.
It is a further core object of the invention that the step of providing the flame arrestor device comprises installing a plurality of cells made of a plurality of mesh panels. The plurality of units are mounted end-to-end to each other proximate the enclosure.
Drawings
In order to understand the invention and to see how it may be carried out in practice, embodiments will now be suitable for description, by way of non-limiting example only, with reference to the accompanying drawings, in which
FIG. 1 is a cross-sectional view of an airship;
FIG. 2 is a schematic perspective view of a unitary structure of a flame arrestor; and
FIG. 3 is a schematic perspective view of an exemplary mesh unit of a flame arrestor.
Detailed Description
The following description is provided to enable any person skilled in the art to make and use the invention and sets forth the best modes contemplated by the inventors of carrying out their invention. Nevertheless, various modifications will be apparent to those skilled in the art, since the general principles of the invention have been defined specifically to provide an airship and a method of manufacturing the airship.
The term "airship" refers hereinafter to airships, aircraft, airships, balloons, and other large aircraft that are completely or partially buoyant.
The term "hydrogen" refers hereinafter primarily to hydrogen, but also to other combustible gases that can be used as lifting gas in an airship. It is noted that critical diameter values and quench length values are determined for each gas type and can be different from the critical diameter values and quench length values of hydrogen.
Based on the experimental work in [ 3 ] and reported by [ 1 ] as part of the MESG comparison in [ 2 ], the MESG "maximum experimental safety gap" for hydrogen in the uk was 0.28mm (adjusted to 1 atmosphere and 293K). While MESG gives a representation of the flame arrestor channel dimensions, it is analyzed in more detail below.
The reference [ 1 ] states that for a flame to be quenched, the flame arrestor channel must be small enough to extract heat from the flame faster than the chemical reaction generates heat. Cross sectional area AcThe smaller the area, the longitudinal surface area to volume ratio ALThe greater the/V.
Thus for a cylindrical channel of length L:
therefore, the temperature of the molten metal is controlled,
It is noted that the channel length has been removed from the equation and, in practice, the equation has been successfully used to design flame arrestors for slow flame speeds. The reference [ 1 ] shows the work of [ 4 ], and [ 4 ] states the critical (quenching) diameter D of hydrogencr0.7 to 0.9 mm. DhMust be less than the critical (quenching) diameter DcrTo cause the flame arrestor to function.
For a woven mesh panel (with square channels instead of circular channels), the equivalent hydraulic diameter can be calculated for each channel according to [ 1 ] using the following equation:
Dh＝1/M-Dw
wherein D iswIs the diameter of the wire and M is the number of meshes per unit length.
For high velocity flames, such as those produced by the combustion of hydrogen, the length of the flame arrestor passage must also be considered. The longer passage allows the flame arrestor to have a longer time to quench a fast moving flame.
According to [ 5 ] based on the work product of [ 6 ] for corrugated belt flame arrestors, the quench length required for a high speed flame can be calculated according to the following formula:
Lq＝(viDh 2)/(100v) (1)
wherein L isqFor quenching length (cm), vtIs turbulent flame velocity (cm/s) and v is kinematic viscosity (cm) of the combustion products2In s). If the quench length is very short, say less than 1mm, it is reasonable to apply this equation to the woven mesh, and short waves would be similar.
Kinematic viscosity (m)2Is defined as:
v＝η/ρ (2)
wherein η is the dynamic viscosity (Pa.s) and ρ is the density (kg/m)3) η and ρ are both directed to combustion products in the current analysis.
According to [ 7 ], the dynamic viscosity of the drying air is a function of the static temperature t (k):
η＝1.5105×10-6×T1.5/(T+120) (3)
【7】 The inner graph 3.7 shows the above relationship of pure air and kerosene combustion products (fuel-air ratio, up to 0.05) and it is noted that the graph can be used for combustion products of all fuel-air mixtures with negligible error. The graph reaches 1600K. The inventors hypothesize that this equation can be used at higher temperatures to provide a reasonable estimate of the dynamic viscosity of the combustion products of the fuel-air mixture (including the fuel products of the hydrogen-air mixture).
The adiabatic flame temperature at atmospheric conditions at constant pressure of a stoichiometric hydrogen-air mixture will have a flame temperature of about 2550K. The adiabatic flame temperature is the maximum temperature that the combustion products can reach.
Reference [9 ] is an experimental study of an unconstrained large scale hydrogen-air deflagration process. Reference [8]Also refer to [9 ]]The key result of (1). This study showed that the unconstrained stoichiometric hydrogen-air deflagration process, for a first 4m flame front radius of 0.1s after ignition, the flame velocity was about vt40m/s and for the next 12m flame front radius after an additional 0.15s the flame speed is 80 m/s.
At high temperatures (and pressures near atmospheric), the combustion products can behave like perfect gases.
Therefore, the temperature of the molten metal is controlled,
ρ＝p/(R.T)
where p 110000Pa (the value is derived from the following), T2550K and the gas constant R287.1 Jkg-1K-1。
Therefore, ρ is 0.1503kg/m3。
Thus, from the above analysis, formula (3) gives η ═ 72.848x 10-4PaS, formula (2) gives v ═ 4.8484x 10- 4m2/s＝4.8484cm2The quenching length is given by/s and formula (1):
for flame front radii of up to 4m
Lq＝0.0132cm＝0.132mm
And the number of the first and second groups,
for flame front radii of up to 16m
Lq＝0.0264cm＝0.264mm
(for D)h0.04cm to 0.4mm, these quench lengths give channel length to hydraulic diameter ratios of 0.33 and 0.66, respectively).
Existing corrugated tape flame arrestors for hydrogen-air flames, used in pipes, are about 20mm long. Therefore why is this flame arrester theoretically less than 1 mm?
A key driver for such short quench lengths is the unconstrained natural nature of combustion, which results in flame speeds of about 40 to 80 m/s. Reference [ 10 ] measures the hydrogen-air flame velocity in (confined) piping at 400m/s during deflagration and near 1400m/s in an explosion.
According to equation (1), the quenching length is proportional to the flame speed. There is more time for the flame arrestor to quench the slower moving unconstrained flame front.
This small quenching length (less than 1mm) associated with the "thickness" of the flame arrestor allows the design of thin, lightweight woven meshes that in turn can be used to cover large areas to quench large unconstrained flame fronts.
The open area of the mesh openings will be 10% to 50% of the total mesh area.
The multiple cells and plate shapes will be distinct within the envelope, but most will be close to: a cubic cell shape made of a plurality of square "top" panels (panels not connected to the envelope) and rectangular "side" panels (connected to the envelope).
Thus, for example, the top panel can be 3m x 3m and the side panels can be 3m x2 m. The length and width of the plate will be between 0.5m and 0.8 m.
These connected cells form a layer of protective cells around the inside of the envelope. They are passive protection such that if there is a breach in the encapsulating fabric that causes mixing of hydrogen and air, then if ignition (e.g. from lightning or electrostatic discharge) occurs, the resulting combustion can be contained within one or several cells (depending on the nature of the breach). Most importantly, the central volume of hydrogen is less likely to combust.
Referring now to fig. 1, this fig. 1 presents a cross-sectional view of an airship 10 filled with hydrogen gas lighter than air. The envelope 20 is provided with a cellular mesh structure 50 arranged along the envelope 20 to prevent a fire from propagating from the peripheral portion 40 of the inner space next to the walls of the envelope 20 to the central space 30.
Referring now to fig. 2, this fig. 2 shows a cellular mesh structure 50 in detail. The base unit 55 is formed by mesh plates 51, 52, 53 and 54 substantially perpendicular to the envelope 20 and plates 58 substantially parallel to the envelope 20. Different geometries of the cellular mesh structure are within the scope of the invention.
Referring now to fig. 3, the base unit 55 is shown in fig. 3. According to an exemplary embodiment of the present invention, mesh plates 51-54 and 58 are made of carbon fiber tows or aluminum alloy wires. The interconnection of the aforementioned panels by stitching and zippers (not shown) is within the scope of the present invention.
A) Example design Using carbon fibers
For an airship design similar to HAV606 (200 metric tons payload)
Envelope volume of 457500m3。
Surface area (estimated) 37720m2。
Flame arrestor design and channeling parameters
Carbon fiber tow (commercially available Hexcel IM7 carbon fibers (6000 monofilaments)) having a thickness of 0.13mm2Cross-sectional area of (a) and a diameter of 0.407 mm. The mass of the tow per unit length was 0.223x 10-3kg/m。
For a cell with a top plate of 3m x 3m and side plates of 3m x2m, each plate has 2 mesh layers. The tows were woven to have a gap of 0.4mm between the weft (longitudinal tows) and warp (transverse tows).
For the top mesh layer, the number of tows will be 3000mm/(0.407mm +0.40mm) 3717 weft and 3717 warp (transverse tows), giving a total of 7435 tows with an open area of 25% of the total area of the mesh, so that the closed area is 75%.
Mesh (i.e., tow) per unit length, M3717/3000 1.239 per mm.
Hydraulic diameter Dh＝1/M-Dw1/1.239-0.407-0.400 mm (critical diameter D less than 0.7mm to 0.9mm)cr)。
And L ═ 2x Dw) x mesh layer number (2x 0.407) x2 1.628mm (greater than the required quenching length L for flame front radii of up to 4 m)q0.132mm and L for a flame front radius of up to 16mq0.264mm)。
(Note that compression of the tows during the braiding process will reduce L and DhSo the design may need to be adjusted).
Flame arrestor total mass and resulting airship payload
The mass of the top plate (2 mesh layers) was 2x 7435x 3x 0.223x 10-3＝9.948kg。
Using a similar approach for the rectangular adjustment,
the weight of the side panels (2 mesh layers) was 6.632 kg.
The mass of the unit (made of 1 top plate and 2 side plates) is 23.212 kg. (note that the 3-plate elements that are sewn to each other and attached to the envelope become a closed unit).
The number of units covering the surface area of the envelope is (roughly) 37720/9 4191.
The total weight of the flame arrestor plate was 37720x 23.212, 97284kg, 97.3 metric tons (excluding sutures and zippers).
Additional lift L-457,500 (0.164-0.085) -36,143 kg-36.1 metric tons with 0.164kg/m, using hydrogen instead of helium3Is a helium density of 0.085kg/m3Is the hydrogen density.
Thus by replacing helium with hydrogen and one layer of units (giving a protective layer of 2m envelope), the payload of the HAV606 becomes 200-97.3+ 36.1-138.8 metric tons, which can still be considered as the actual payload.
And if a two layer unit is used (giving a protective layer of 4 m) the payload becomes 41.5 metric tons, too low for this example panel design.
For larger airships, there is a reduced payload percentage drop for each layer in the cells.
Provided that the fire-stopping passage characteristics are satisfied (hydraulic diameter D)hLess than critical diameter DcrAnd the channel length L is greater than the quenching length Lq) Then a plate from other materials and/or an alternative to woven mesh such as a perforated sheet or film may provide design improvements.
Hydrogen-air combustion pressure load on the unit
According to [9 ], a stoichiometric hydrogen-air mixture is ignited in a hemispherical plastic envelope up to 25m diameter at ground and ambient conditions. The plastic envelope can easily burst during combustion to ensure unrestricted combustion.
As described above, the average flame front velocity is 40m/s during the first 4m radius, 0.1s, and 80m/s during the next 12m radius, 0.15s, thus producing a deflagration (not a more severe detonation).
A maximum static pressure increase of 3kPa was measured at a radius of 2m from the fire point and a maximum static pressure increase of 6kPa was measured at a radius of 5m from the fire point (in practice a peak of 10kPa static pressure increase was measured at a radius of 5m from the fire point, but the authors of [9 ] questioned that the instrument reaction resulted in a 10kPa peak, while the more constant 6kPa increase was a true maximum).
According to [ 11 ], it is possible to estimate the pressure drop across the wire mesh with 25% open area to be 2 kPa. Thus for 2 mesh layers, a total of 4kPa is estimated.
Thus, during combustion, we can estimate that the maximum static pressure downstream of the mesh plate is 100kPa (atmospheric) +6kPa (pressure rise during combustion) ═ 106kPa, and we can estimate that the maximum static pressure upstream of the mesh plate is 100kPa (atmospheric) +6kPa (pressure rise during combustion) +4kPa (pressure drop across the flame arrestor): 110 kPa.
For a top square mesh plate with 3m sides, a drop of 4kPa will result in a pressure drop across the mesh plate of x maximum shear stress of plate area/(tow cross-sectional area x number of tow warp threads of 1 layer x number of mesh layers):
(4x 103)x(3x 3)/(0.13x 10-6x 2x 7,435x2)＝4.66x 10-6Pa＝9.31MPa
the shear yield stress of the carbon fiber tow was 128MPa (tensile yield stress was 5480 MPa). This simple shear stress calculation therefore indicates that the top mesh plate design is sufficiently robust to withstand the combustion pressures within the cell. The smaller side plates will have lower shear stress than the top plate.
Hydrogen-air combustion heat load on the unit
The amount of heat generated in the cell during combustion is determined by the amount of hydrogen combusted in the cell.
The following analysis shows that most of the original hydrogen in the unit (prior to combustion) is vented through the mesh plate by the advancing flame front (during combustion) before it reaches the mesh plate. This is a key property to keep the energy released by burning hydrogen relatively low and thus to prevent the lightweight mesh panels from overheating during combustion.
Before combustion (p)1，V1＝m1RT1) And after combustion (p)2，V2＝m2RT2) Using equations of state in one of the units, it is assumed that the resulting high temperature (near atmospheric pressure) combustion products (water vapor, nitrogen and nitrogen oxides) behave like a perfect gas. And assume that the cell walls deflect during combustion to give about 20% extra volume (V)2/V1＝1.2)
Give m2/m1＝(p2/p1).(V2/V1).(T1/T2)＝(110kPa/100kPa)x 1.2x (288K/2550K)＝0.1491。
According to [8 ] and [9 ], the hydrogen-air mixture has 29.7% hydrogen by volume, which is very close to the published VH/(VH+Vair) Stoichiometric hydrogen-air mixture 0.296, 29.6% hydrogen (V) by volumeair/VH2.39), and the published mH/(mH+mair) 0.283, 2.83% by mass of hydrogen (m)air/mH)＝34.33。
According to [8 ] and [9 ], the density of the stoichiometric hydrogen-air mixture was 0.8775kg/m3. The volume of the unit before combustion was 18m3。
The mass of hydrogen in the unit before combustion is therefore:
mH1＝0.8775×18×0.0283＝0.4470kg
and the mass of hydrogen actually combusted (and not exhausted through the mesh plate) during combustion can be estimated as:
mH2＝mH1·m2/m1＝0.4470×0.1491＝0.06665kg
the combustion energy released per unit mass of hydrogen was 140MJ/kg
The energy released by the burning mass of hydrogen in the cell is therefore,
E＝140×0.06665＝9.331MJ
assuming that all energy is absorbed by 1 top panel and 4 side panels, m is 1x9948kg +4x6632kg is 36.476 kg.
c 879J/Kg.K (specific heat capacity of HexTow IM7 carbon fiber)
The temperature rise of each plate is therefore:
ΔT＝E/(m.c)＝9.331×106/(36.476×879)＝291K
the temperature of the plate immediately after combustion is therefore 288K +291K 579K.
In fact, during combustion (higher pressure stage on the mesh plate), a relatively small fraction of the hot gas transfers its heat to the mesh plate (the remaining hot gas will be initially retained within the unit).
Thus, if 30% of the released energy is transferred to the panel, the temperature increase Δ T is 87K, while the temperature of the panel immediately after combustion is 288K +87K 375K.
After combustion is complete, hot gases may flow through several plates. However, these plates will not be subjected to combustion pressure loads, and the heated plates will have more time to conduct heat to the adjacent cooler plates and cooler air outside the unit. Also, some of the heated gas may mix with cooler air near the initial breach, causing air to enter the enclosure first.
The auto-ignition temperature of hydrogen was 793K [ 12 ].
This very simple analysis therefore shows that the mesh plate does not auto-ignite the gas that has passed through the cell.
During the manufacturing stage, the carbon fibers are heated up to the range of 1800K-3000K. The carbon fibers have a melting point of about 3800K (it may be desirable to avoid the use of epoxy-containing carbon fibers because epoxy resins melt at lower temperatures).
B) Example designs Using aluminum alloys
It should be noted that ρ 2,700kg/m is used3Carbon fibre filaments are replaced by the same aluminium alloy filament (eg aluminium alloy 6061) of 0.407mm diameter and 0.4mm gap (giving a mass per unit length of 0.0003513kg/m) and the same mesh sheet size and number of mesh layers and c 897J kg-1K-1The key result is:
hydraulic diameter Dh＝1/M-Dw1/1.239-0.407 ═ 0.400mm (less than critical diameter, D)cr0.7mm to 0.9mm)
L ═ (2x Dw) x mesh layer number ═ (2x 0.407) x2 ═ 1.628mm (greater than the required quench length of 0.132mm for flame front radii up to 4m and 0.264mm for flame front radii up to 16 m).
Roof mass 15.672kg
Side plate weight 10.448kg
83 metric tons payload with hydrogen and cell (200 metric tons payload with helium)
Maximum shear stress 9.30MPa (shear yield stress 270MPa, tensile yield stress 310MPa)
The temperature of the plate immediately after combustion was 469K if all the energy was transferred to the cell plate and 342K if 30% of the energy was transferred to the cell plate (the autoignition temperature of hydrogen was 793K. the melting point of aluminum alloy 6061 was 855 to 925K).
According to one embodiment of the present invention, an airship is disclosed that includes an envelope containing hydrogen lifting gas. A core feature of the invention is to provide the envelope with a flame arrestor arrangement distributed along the envelope. The flame arrestor device comprises a plurality of cells made of a plurality of mesh panels. The plurality of units are mounted end-to-end with respect to each other immediately adjacent the envelope.
According to another embodiment of the invention, the mesh plate forming the plurality of cells has between 1 and 3 mesh layers.
According to another embodiment of the invention, the plurality of mesh panels forming the plurality of cells are interconnected by stitching and zippers.
According to a further embodiment of the invention, the mesh layer is made of a material selected from the group consisting of carbon fiber tow, aluminum alloy wire, and combinations thereof.
According to a further embodiment of the invention, the carbon fiber tow is characterized in that the number of filaments is between 1000(lk) and 12000(12 k).
According to a further embodiment of the invention, the mesh layer is woven such that each channel has a hydraulic diameter smaller than the critical diameter of the lifting gas.
According to a further embodiment of the invention, the mesh layer has a single or combined channel length that is larger than the quenching length of the lift gas.
According to a further embodiment of the invention, said mesh openings are characterized in that the open area ranges between 10% and 50% of the total area of said mesh openings.
According to a further embodiment of the invention, the size of the cells is in the range between 0.5m and 8.0 m.
According to yet another embodiment of the invention, a method of manufacturing an airship is disclosed. The method comprises the following steps: (a) providing an enclosure configured to contain hydrogen gas; (b) providing a flame arrestor device; (c) mounting the flame arrestor device on an inner wall of the enclosure; (d) the encapsulation is filled with hydrogen.
It is a further central feature of the invention that the step of providing the flame arrestor device comprises installing a plurality of cells made of a plurality of mesh panels. The plurality of units are mounted end-to-end to each other proximate the enclosure.
Glossary
Area A, m2
Specific heat capacity of C, J kg-1K-1
D diameter, m
E energy, J
H hydrogen gas
He helium gas
Length of L
M number of meshes M per unit length-1
m mass, kg
p pressure, Pa
R gas constant, J kg-1K-1
T temperature, K
Volume V, m3
v speed, m/s
Rho Density, kg/m3
η dynamic viscosity, Pa.s
V kinematic viscosity, m3/s
Lower corner mark
air of air
C cross section
cr critical value
H hydrogen gas
h hydraulic pressure
L longitudinal direction
q quenching
t turbulence
W wire
1 before combustion
2 after combustion
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stanley S.Grossel (2010) explosion detonation flame arrestor
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Britton, L.G.2000a. "use the maximum experimental safety gap to select flame arrestors. Process safety progress 19(3),140-
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