Aerodynamic hydrogen tanks, and cryogenic insulated pipes

Abstract

A cryogenic insulated pipe having a conformally-bonded aerogel paper layer on an outer surface of the pipe. The conformally-bonded aerogel paper layer is conformally-bonded to the pipe outer surface in a pre-applied resin layer. An insulative blanket is applied over the aerogel paper, and a breathable protective layer is applied over the insulative blanket. Also disclosed is a cryogenic fuel tank for retrofitting a conventional fossil fuel-powered aircraft, or for a purposely built aircraft to run on hydrogen has an aerodynamically shaped outer surface including an ogive shaped nose cone, and a tapered tail cone, wherein the tapered tail cone includes actively adjustable elements for adjusting aerodynamic characteristics of the cryogenic fuel tank. The cryogenic fuel tank is configured to be attached below wings of the aircraft, through support pylons, which include sensors configured to measure forces applied by the cryogenic fuel tank to the airframe. The cryogenic fuel tank includes a nozzle and valve configured to vent gas from the cryogenic fuel tank by expansion through the nozzle in the event that the cryogenic fuel tank is j ettisoned from the aircraft.

Description

AERODYNAMIC HYDROGEN TANKS, AND CRYOGENIC INSULATED PIPES

[0001] The present disclosure relates to clean energy-based transportation systems. The disclosure has particular utility in connection with hydrogen-powered aircraft and, in particular, aircraft powered by electric power generated by hydrogen fuel cells and will be described in such utility, although other utilities are contemplated, including aircraft powered by hydrogen- burning internal combustion engines including jet engines. The disclosure also relates to cryogenic insulated pipes and methods for making cryogenic insulated pipes.

[0002] This section provides background information which is not necessarily prior art, and which is related to the present disclosure. This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all its features.

[0003] Exhaust emissions from transport vehicles are a significant contributor to climate change. Conventional fossil fuel-powered aircraft engines release CO2 emissions. Also, fossil fuel-powered aircraft emissions include non-CCh effects due to nitrogen oxide (NOx), vapor trails and cloud formation triggered by the altitude at which aircraft operate. These non-CCh effects are believed to contribute twice as much to global warming as aircraft CO2 and are estimated to be responsible for two-thirds of aviation’s climate impact. Additionally, the highspeed exhaust gases of conventional fossil fuel-powered aircraft engines contribute significantly to the extremely large noise footprint of commercial and military aircraft, particularly in densely populated areas.

[0004] Moreover, in surveillance and defense applications, the high engine noise and exhaust temperatures of conventional fossil fuel-burning engines significantly hamper the ability of aircraft to avoid detection and, therefore, reduce the mission capabilities of the aircraft.

[0005] Rechargeable battery-powered terrestrial vehicles, i.e., “EVs”, are slowly replacing conventional fossil fuel-powered terrestrial vehicles. However, the weight and limited energy storage of batteries makes rechargeable, battery-powered aircraft generally impractical.

[0006] Hydrogen fuel cells offer an atractive alternative to fossil fuel-burning engines. Hydrogen fuel cell tanks may be quickly filled and store significant energy, and other than the relatively small amount of unreacted hydrogen gas, the reaction exhaust from hydrogen fuel cells comprises essentially only water.

[0007] While purposely built hydrogen fuel cell-powered aircraft are being designed and tested, converting and retrofiting conventional fossil fuel-powered airframes to be powered by hydrogen (H2) provides an attractive alternative to purposely built hydrogen fuel cell-powered aircraft.

[0008] Converting and retrofitting a conventional fossil fuel-powered aircraft to run on hydrogen-powered fuel cells involves replacing the fossil fuel-powered engine, fuel tanks and assorted fuel lines, fuel pumps and various valves, sensors, gauges, and instruments specific to a conventional fossil fucl-powcrcd engine, by an electric powered engine, a source of electricity, typically, a hydrogen fuel cell configured to generate electricity, and cryogenic fuel tanks for storing hydrogen either in liquid or gaseous form.

[0009] Retrofitting aircraft to run on hydrogen (H?) requires cryogenic fuel tanks of larger volume than the fossil fuel tanks being replaced, to hold sufficient compressed H2 gas or H2 liquid to power the aircraft for a desired range. The commonly proposed solution of mounting H2 cryogenic fuel tanks under the aircraft wings results in changes to wing aerodynamic characteristics (e.g., lift, drag, moment distribution) and wing structural loads (e.g., point loads, wing weight distribution) which can affect both aerodynamic stability and aeroelastic response, as well as increase drag.

[0010] Unlike conventional H cryogenic fuel tanks that typically are cylindrical in shape with blunt, rounded caps, in accordance with the present disclosure, we configure the shape of the H2 cryogenic fuel tanks to make them more aerodynamic by shaping them as an ogive nose with a cylindrical body and conical narrowing at the tail. We also provide our shaped cryogenic tank bodies with H2 flow paths or flow channels in couplers, typically mounting bosses on the tank, whereby to eliminate the necessity for additional H2 plumbing connections. In one aspect, we equip our H2 cryogenic fuel tanks with active aerodynamic control surfaces and components to compensate for added weight and drag, and aerodynamic and structural loads. In some embodiments, active aero components are configured to guide a dropped or jettisoned fuel tank (e.g., in an emergency situation where a hard landing may occur), and valving and nozzles are included so that H2 vented from the tank optionally may be used for propulsion. Active aerodynamic control has been employed on winglets on conventional aircraft but, heretofore, not on dropped or jettisoned tanks to compensate for loads while attached to the wing. Active aerodynamic control has been employed to guide Joint Direct Attack Munition (JDAM) munitions but heretofore not in connection with dropped or jettisoned fuel tanks. Nor has tank venting heretofore been used to propel dropped or jettisoned drop tanks. As a consequence, in an emergency scenario, where it may be necessary to jettison an H2 tank before landing to ensure passenger safety, active aerodynamic elements may be used to guide a jettisoned tank away from the plane and to a safe landing location, e.g., under autopilot control, using venting H2 gas to provide thrust for maneuvering.

[0011] Retrofiting aircraft with H? cryogenic fuel tanks wherein, in the original aircraft design, the fossil fuel load was distributed within the wing, typically requires wing modifications to accommodate additional loads. Modifying the aerodynamic properties and mounting method of the tanks in accordance with the present disclosure allows for retrofiting aircraft with minimal or no modifications to the wing structure. Active aerodynamic elements on our cryogenic fuel tanks also can be used to improve aerodynamic performance, reduce stall speed, compensate for mass property changes, and improve stability of the aircraft in flight. In one aspect of the disclosure, we include couplers for mounting in the cryogenic fuel tank, which include H2 flow paths or flow channels integrated into the mountings.

[0012] In accordance with the present disclosure, a H2 cryogenic fuel tank is manufactured in an aerodynamic shape, for example by forming a composite filament outer tank body with front and rear caps configured to improve aerodynamic characteristics. Specifically, the rear cap is rearwardly tapered (e.g., 5 to 15 degrees, preferably 7 to 13 degrees, more preferably ~10 degrees) and the front cap is shaped as an ogive nose cone. In one embodiment, the nose cone is constructed of an energy absorbing material to reduce the possibility of damage in the event of an impact (e.g., bird strike). The nose cone shape is designed to enable maintenance of laminar flow over the tank body. Couplers are designed to include flow paths or flow channels for the H2, thus eliminating the need for a separate H2 piping system. Hardpoints for mounting, containing the H2 flow paths, preferably are integrally formed, i.e., in the composite filament winding process, to allow for an integrated mounting / plumbing system at points of connection. In some embodiments, the tank outer mold line (OML) may be shaped to blend with the wing lower surface. In another embodiment, a fairing is included around the mounting points to protect the connection carrying H2 from impact (e.g., bird strike).

[0013] Active aerodynamic elements (such as wings, rudders, elevators) are provided on surfaces of the cryogenic fuel tank, changing the aerodynamic characteristics of the tank, and which may be adjusted resulting in forces and moments on the aircraft wing. Specifically, the tank / fuel center of gravity (CG) may be adjusted to be ahead of the mounting location, and tank center of pressure (CP) may be adjusted to be behind the mounting point. This enables aerodynamic stability of the tank system.

[0014] In one embodiment, support pylons for the tank include a strain gauge or gauges or other force sensors to measure forces applied by the tank assembly to the airframe. A controller is provided, configured to interpret those signals to detect trim conditions. The controller may interpret those sensor signals and adjust the aerodynamic elements to minimize loads, avoid aeroelastic divergence, or augment other aerodynamic interactions with the airframe. Also,active control of tank CG can be accomplished by dividing the tank by internal dividers into two or more bays and using a fuel pumping system to transfer fuel between bays, as needed.

[0015] A feature and advantage of the instant disclosure is that, in the event of an emergency landing, the H2 cryogenic fuel tanks can be jettisoned. Optionally active aerodynamic elements can be used to guide the tanks away from the aircraft, or to a safe landing zone, e.g., under autopilot control. In one embodiment, a thermal / pressure relief device in the tank tail can be used to vent H2 from the jettisoned tank and the vented H2 used to propel the tank by expansion through a nozzle.

[0016] In another embodiment, to handle an over-pressure or over-temperature event, a pressure relief device (PRD) is provided to vent fuel in a safe direction. Venting may be up and aft which are safe directions both in flight and while on the ground. Typically, the PRDs are housed in a tail cone of the tank to protect the PRDs from bird strikes or other impact damage.

[0017] More particularly, in accordance with Aspect A of the present disclosure, there is provided a cryogenic fuel tank for aircraft, said cryogenic fuel tank having an aerodynamically shaped outer surface including an ogive shaped nose cone and a tapered tail cone, wherein said cryogenic fuel tank includes actively adjustable elements for adjusting aerodynamic characteristics of the cryogenic fuel tank, wherein the cryogenic fuel tank further includes a valve and nozzle configured to vent fuel from the tank in the event that the cryogenic fuel tank is jettisoned from the aircraft, where the venting fuel expanded through the nozzle can be used to propel the fuel tank.

[0018] In one aspect, the cryogenic fuel tank is configured to be attached below wings of the aircraft.

[0019] In another aspect, the cryogenic fuel tank is configured to be attached to wings of the aircraft through support pylons.

[0020] In a further aspect, the support pylons preferably include sensors configured to measure forces applied by the cryogenic tank to the airframe.

[0021] In yet another aspect, the support sensors include strain gauges.

[0022] In a still further aspect, the cryogenic fuel tank further includes a controller configured to interpret signals from the sensors and to configure the aerodynamic elements to adjust loads on the aircraft.

[0023] In yet another aspect, the cryogenic fuel tank includes thermal dividers for dividing the cryogenic fuel tank into two or more bays and further including a pumping system to transfer fuel between bays to control the cryogenic fuel tank center of gravity.

[0024] In a further aspect, the cryogenic fuel tank further includes pressure relief devices configured to vent fuel away from the cryogenic fuel tank in the event of over-pressure or overtemperature.

[0025] In another aspect, the cryogenic fuel tank further includes a valve and nozzle configured to vent fuel from the cryogenic fuel tank in the event that the cryogenic fuel tank is jettisoned from the aircraft, where the venting fuel expanded through the nozzle can be used to propel the fuel tank.

[0026] In a further aspect, the cryogenic fuel tank further comprises a controller, configured to control venting of the fuel.

[0027] According to Aspect B, the present disclosure also provides an aircraft vehicle configured to be propelled by a cryogenic fuel, and comprising a cryogenic fuel tank as above described, and having aerodynamically-shaped outer surface including an ogive shaped nose cone, a cylindrical body, and a tapered tail cone, wherein said tapered tail cone includes actively adjustable elements for adjusting aerodynamic characteristics of the fuel tank, and wherein the cryogenic fuel tank further includes a valve and nozzle configured to vent fuel from the tank in the event that the cryogenic fuel tank is jettisoned from the aircraft, where the venting fuel expanded through the nozzle can be used to propel the fuel tank.

[0028] In one aspect the aircraft comprises a hydrogen fuel cell-powered aircraft.

[0029] In another aspect, the cryogenic fuel tank is configured to be attached to wings of the aircraft through support pylons, wherein the support pylons preferably include sensors configured to measure forces applied by the cryogenic fuel tank to the airframe, wherein the sensors preferably include strain gauges, and further optionally including a controller configured to interpret signals from the sensors and to configure the aerodynamic elements to adjust loads on the aircraft.

[0030] In a further aspect, wherein the cryogenic tank includes dividers for dividing the cryogenic fuel tank into two or more bays and further including a pumping system to transfer fuel between bays to control the cryogenic fuel tank center of gravity, and / or wherein the cryogenic tank further includes pressure relief devices configured to vent fuel away from the cryogenic fuel tank in the event of over-pressure or over-temperature.

[0031]

[0032] In another aspect the aircraft vehicle comprises a fossil fuel-burning aircraft vehicle retrofitted to run on hydrogen.

[0033] In still another aspect the aircraft comprises a purposely built hydrogen fuel cell- powered aircraft.

[0034] In a further aspect the cryogenic fuel tank is positioned below the wings of the aircraft.

[0035] In a further aspect the cryogenic fuel tank is supported below wings of the aircraft through pylons.

[0036] In a further aspect the cryogenic fuel tank is fixed to the pylons through integrally joined couplers which include flow paths or flow channels configured for carrying fuel from an interior of the cryogenic fuel tanks to a power train on the aircraft.

[0037] In yet another aspect the pylons include ullage controls and / or gasifier heat exchangers.

[0038] In a further aspect the coupler includes hard point fittings for mounting to support pylons, wherein the hard point fittings are configured to release the cryogenic fuel tanks so that they may be dropped or jettisoned under emergency conditions.

[0039] In still another aspect the cryogenic fuel tank includes a controller configured to control venting of gas from the cryogenic fuel tank under emergency conditions.

[0040] The present disclosure relates to insulation systems, and more particularly, to insulation systems for use at cryogenic temperatures. The disclosure has particular utility in connection with insulation systems for use with insulating cryogenic piping or cryogenic conduits for transferring highly volatile materials, such as liquid hydrogen between cryogenic storage tanks and fuel cells for powering vehicles such as aircraft, and will be described in connection with such utility, although other utilities are contemplated.

[0041] As noted supra, use of cryogenic fluids, such as liquid hydrogen (LH2) for powering fuel cell-powered aircraft, offers an attractive alternative to conventional liquid fossil fuelburning engines. Liquid hydrogen is stored in a liquid state at very low temperature, i.e., below -252°C (2 IK), in high pressure cryogenic tanks. Typically, cryogenic tanks are multiwalled structures with supports or studs maintaining space between the walls. The space between the tank walls may contain insulating material and / or is evacuated, i.e., to form a vacuum.

[0042] In use, LH2 fuel is flowed from cryogenic storage tanks through cryogenic pipes to the fuel cells, which create electrical energy for powering electric motors. However, pockets or inclusions between the cold cryogenic pipes and their surrounding insulation may permit gaseous oxygen from ambient air to become liquid. The liquid oxygen may ignite if brought into contact with a combustible material (e.g., drippings onto the tarmac or organic polymers within insulation). Water from ambient air also may build up in the outer layers of cryogenic pipe insulation, which may lead to degradation of the cryogenic pipe insulation performance and foreign object debris risk from thermal cycling, causing pieces of the cryogenic pipe insulation to break off. Water buildup also may substantially increase weight, cause corrosionto critical components in or below the tank, and / or create a fertile environment for pathogens, such as certain bacteria.

[0043] In accordance with another aspect of the present disclosure, cryogenic pipes running between a cryogenic storage tank and a fuel cell arc thermally insulated by an insulation system having a conformally-bonded aerogel paper layer adjacent to the pipe surface to prevent pockets of disbond between the pipe and insulation. An insulative blanket is applied over the aerogel paper, and a breathable glass composite layer is applied over the insulative blanket to protect the insulative blanket and to prevent moisture / ice buildup in the insulative blanket.

[0044] More particularly, in accordance with the present disclosure, cryogenic pipes are insulated using a composite insulation formed as follows. A resin layer formed of, e.g., an epoxy or another thermoset material selected to have low out-gassing is applied to a pipe outer surface. The resin layer typically will have a resin weight fraction of 20 to 80 %, preferably 40 to 50 %, more preferably about 45%. A layer of aerogel paper is tightly wrapped over the resin layer before the resin layer sets, bonding the layer of aerogel paper conformally to the pipe outer surface. The layer of aerogel paper, being closely bonded to the outer surface of the cryogenic pipe, prevents pockets / inclusions where ambient oxygen may condense and build up. The layer of aerogel paper may have a thickness of 0. 1 to 10 mm, preferably 0.35 to 3 mm, more preferably 1-2 mm.

[0045] The aerogel paper is then covered by an insulative blanket. The insulative blanket may be a blanket of aerogel material of 5 to 50mm thickness, preferably 5 to 20mm thickness, more preferably about 10 mm thickness with a density of 3 to 300 kg / m3, preferably 110 to 220 kg / m3, more preferably 160 kg / m3. A protective outer layer of scrim glass composite is then wrapped around the insulative blanket, providing a breathable, protective outer layer. Alternatively, the insulative blanket may be formed on an inside surface of the protective outer layer, and the insulative blanket / protective outer layer composite applied together over the aerogel paper.

[0046] The insulation system may be applied to the cryogenic pipe using standard pipe insulation wrapping methods. In one embodiment, the one or more layers of aerogel paper are counter-wrapped around the cryogenic pipe, bedded in a pre-applied resin layer. Also, tape attachments may be used to fix the insulative blanket to the cryogenic pipe. Also, a foil backing may be used as a surface for tape application.

[0047] In accordance with Aspect C of the disclosure, there is provided a cryogenic insulated pipe comprising a pipe having a conformally-bonded aerogel paper layer on an outer surface of the pipe.

[0048] In one embodiment, the conformally-bonded aerogel paper layer is conformally-bonded to the pipe outer surface in a pre-applied resin layer.

[0049] In another embodiment, an insulative blanket is provided over the aerogel paper.

[0050] In a further embodiment a breathable layer is provided over the insulative blanket.

[0051] In one embodiment, the insulative blanket comprises an aerogel material.

[0052] In another embodiment the insulative blanket comprises a spray-on foam, or expanded cork.

[0053] In still yet another embodiment the breathable protective layer comprises a breathable plan composite material, wherein the breathable plan composite material preferably comprises a woven or braided glass sheet.

[0054] In yet another embodiment, the cryogenic insulated pipe is configured to transport liquid hydrogen.

[0055] According to Aspect D of the disclosure, there is provided a method for forming a cryogenic insulated pipe as above described in Aspect C, comprising providing a pipe, and covering an outer surface of the pipe with a conformally-bonded layer of aerogel paper.

[0056] In one embodiment, the outer surface of the pipe is coated with a resin, and the coated pipe wrapped with the aerogel paper before the resin sets.

[0057] In another embodiment, an insulative blanket is added over the aerogel paper layer.

[0058] In one embodiment, the insulative blanket comprises an aerogel.

[0059] In another embodiment, the insulative blanket comprises a spray-on foam or an expanded cork.

[0060] In a further embodiment, a breathable protective layer is added over the thermal insulating layer.

[0061] In a further embodiment, the protective layer comprises a breathable glass composite material.

[0062] In yet another embodiment, the breathable glass composite material comprises a woven or braided glass sheet.

[0063] According to Aspect E of the disclosure there is provided a vehicle comprising an insulated cryogenic pipe as above described in Aspect C.

[0064] In one embodiment, the vehicle comprises a hydrogen fuel cell-powered vehicle.

[0065] In another embodiment, the vehicle comprises a fuel cell-powered aircraft.

[0066] In still another embodiment, the vehicle comprises a rocket.

[0067] Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

[0068] Further features and advantages of the disclosure will be seen in the following detailed description, taken in conjunction with the accompanying drawings. The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations and are not intended to limit the scope of the present disclosure.In the drawings:Fig. 1 is a top plan view of an aircraft in accordance with one embodiment of the present disclosure;Fig. 2 is a side elevational view of the aircraft of Fig. 1;Fig 3 is a side elevational view, in partial section, showing details of a cryogenic tank in accordance with one embodiment of the disclosure, and Fig. 3A is an enlarged view showing details of a boss element of the cryogenic tank;Fig. 4 is a detailed sectional view showing elements of the tail end of a cryogenic tank in accordance with the present disclosure;Fig. 5 is a view similar to Fig. 3 of another embodiment of a cryogenic fuel tank in accordance with the present disclosure;Fig. 6 is a block diagram of a controller configured for use with an aircraft of Fig. 1;Fig. 7 is a schematic view of a hydrogen fuel cell-powered aircraft in accordance with the present disclosure;Fig. 8 is a simplified cross-sectional view of an insulated cryogenic pipe insulation system in accordance with still yet another embodiment of the present disclosure, at the pipe midline;Fig. 9 is a flow diagram of a process for insulating a cryogenic pipe in accordance with the present disclosure; andFig. 10 is a flow diagram of an alternative process for insulating a cryogenic pipe in accordance with the present disclosure.

[0069] Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments are provided so that this disclosure will be thorough and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth, such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may beembodied in many different forms, and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

[0070] The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and / or components but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.

[0071] When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected, or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0072] Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of the example embodiments.

[0073] Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe oneelement or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0074] As used herein, “cryogenic pipe(s)”; and “cryogenic conduit(s)” are used interchangeably, and are intended to describe pipe or conduit sections as well as fittings on the pipe(s) and conduit(s), and the ends of the pipe(s) and conduit(s), e.g., where the pipe(s) and conduit(s) are affixed to cryogenic tanks at one end, and the fuel cells at the other end.

[0075] Referring to Fig. 1, an airplane 10 in accordance with the present disclosure includes a fuselage 12, wings 14, 16, and an electric motor driven propulsor 18. Propulsor 18 is powered by fuel cells 22, 24 carried within the wings 14, 16. Alternatively, fuel cells 22, 24 may be carried within the fuselage 12.

[0076] Referring also to Figs. 2-5, a pair of cryogenic fuel tanks 26, 28 are mounted below the wings 14, 16.

[0077] Tanks 26, 28 each include an insulated inner cryogenic tank 25 and a shell comprising a tank main body section 30, having an ogive nose cone section 32 which is shaped to minimize drag using natural laminar flow, boundary layer control or other industry-standard techniques. Tank main body section 30 is generally cylindrically shaped and may have a slightly convex central portion. Each tank 26, 28 includes a tail cone section 34 tapered for optimal pressure recovery to minimize drag. Specifically, tail cone section 34 is rearwardly tapered 5 to 15 degrees, preferably 7 to 13 degrees, more specifically ~10 degrees. Tail cone section 34 may include fill ports 36, emergency dump valves 38, and pressure relief and thermal relief valves 40. Also, in a preferred embodiment, tail cone section 34 may include a nozzle or nozzles 52 connected via valve(s) 54 to the hydrogen tank so that hydrogen fuel can be vented through valve(s) 54 and expanded from nozzle 52 providing thrust for a jettisoned tank as will be discussed below.

[0078] The tank surface / volume ratio should be minimized to reduce heat conducted into the tank, consistent with low induced and parasite drag from the airframe.

[0079] Tanks 26, 28 are supported below the wings 14, 16 by support pylons 46. Support pylons 46 are shaped to minimize drag and may include ullage controls and hydrogen gasifierheat exchangers 48. Alternatively, the hydrogen gasifier heat exchanger may be carried within the wings or the fuselage of the aircraft. Support pylons 46 also may include connection / disconnection fittings as will be discussed below.

[0080] Tanks 26, 28 also include aerodynamic elements optimized to minimize structural torsion loads transferred to the aircraft including vertical fins 42 to control yaw motions or loads, and horizonal fins 44 to control pitch motions or loads.

[0081] The tanks 26, 28 also may include internal baffles 50 to reduce sloshing of fuel. Alternatively, as shown in Fig. 5, the tanks also may be divided into two or more bays divided either by baffles 55 or divider(s) 56. In the cases where the tanks are divided into two or more bays, fuel pumps 58 may be provided to transfer fuel between bays to allow for active control of the tank center of gravity during use. Dividing the tanks into two or more bays also has an advantage in that if one of the bays develops a leak or the tank is otherwise damaged, for example, by a bird strike, the plane may safely be flown and landed on fuel in the undamaged tank bay.

[0082] Referring in particular to Fig. 3 A, the tanks 26, 28 are connected to the aircraft via support pylons 46 via couplers 60. Couplers 60 preferably include flowpaths or flow channels 62 configured for carrying H2 from the interior of the tanks for connection to the fuel cells 22, 24. In practice, the tank outer shell is formed of a strong lightweight material such as composite filament material. Couplers 60 may include hard point fittings 64 formed integrally with or attached to the tank outer shell and include hard points for mounting to the support pylons 46. The mountings also may include fixtures 66 that can be activated to release the tanks 26, 28 so that they may be dropped or jettisoned under emergency conditions. The support pylons 46 also may include strain gauges 68 and sensors 70 configured to measure structural torsion loads and aerodynamic forces on the support pylons so that the vertical and horizontal fins 42, 44 may be trimmed as necessary to minimize strain.

[0083] Referring also to Fig. 6, a control system 80 is provided for controlling the vertical fins 42 and horizontal fins 44 based on signals received from strain gauges and sensors in the support pylons. Controller 80 also may be configured to control the flight path of a jettison tank away from the aircraft.

[0084] Referring to Fig. 7, there is illustrated a hydrogen fuel cell-powered aircraft 110 in accordance with the present disclosure. Aircraft 110 comprises a fuselage 112, wings 114 and two electric motors 116 powering propulsors 118. Electric motors 116 are powered by hydrogen fuel cells 120 which are supplied with hydrogen fuel from cryogenic hydrogen fuel tank 122 via cryogenic fuel lines 124.

[0085] Referring to Fig. 8, cryogenic fuel lines 124 comprise a conduit or pipe 126 formed of metal or a reinforced composite material. A resin layer 128 formed of epoxy or another thermoset resin material chosen to have a low-outgassing is applied to the pipe 126 outer surface. Any commercially available thermoset (c.g., epoxy), or thermoplastic material having a low out-gassing and fire resistance may be used in the practice of this disclosure. Preferred examples are Hexcell epoxy resin matrix systems, either the Hexply prepreg resin or Hexflow infusion resin available from Hexcell. A layer of aerogel paper 130, preferably 1 mm thick, is applied over the resin layer 128. Any commercially available aerogel paper material may be used in the practice of this disclosure. Preferred is Aerogel Paper available from Aerogel Solutions. The aerogel paper layer 130 should be applied over the resin layer 128 before the resin layer sets and should be wrapped so as to closely conform to the pipe surface whereby to prevent pockets / inclusions where atmospheric oxygen may condense and build up. An insulative blanket 132 is then wrapped over the aerogel paper layer 130. Insulative blanket 132 preferably is formed of an aerogel blanket material. Any commercially available aerogel blanket material may be used in the practice of this disclosure. In a preferred embodiment, aerogel blanket 132 comprises Cryogel Aerogel Insulation available from Aspen Aerogels, though similar nanoporous insulation materials could be used, having a thickness of about 10 mm and an aerial mass of about 160 kg / m3.

[0086] An outer layer of scrim glass composite sheet 134 (e.g., Teflon-coated glass as a sleeve, braided PTFE glass scrim, or non-glass Kevlar or Dacron Nomex) is bonded over insulative blanket 132, providing a breathable and protective outer layer. In some embodiments, scrim glass composite sheet 134 is made breathable with a tight weave to prevent foreign object debris (FOD) damage.

[0087] Referring to Fig. 9, the cryogenic pipe insulation system is formed as follows: resin layer 128 is applied to the outer surface of pipe 126 in a first coating step 140, such as by brush or spray coating. Thereafter, one or more layers of aerogel paper 130 is applied to the resin, before the resin sets, tightly wrapping the aerogel paper to the pipe, for example, by hand in a wrapping step 142. The aerogel paper 130 may be applied in one or more layers.

[0088] An insulative blanket 132 is then applied over the aerogel paper 130. Insulative blanket 132 may be applied by wrapping in step 144 or may be formed in place. Preferably, insulative blanket 132 is formed of an aerogel blanket which is wrapped over the aerogel paper 130. Preferred aerogel blankets in the practice of the disclosure are metal oxide aerogels such as silica aerogels, which are formed as composite aerogels incorporating fibrous batting. The aerogels are produced by aggregation of colloidal particles, typically under acidic conditions,to form 3-dimensional gel microstructures. Aerogel insulation is preferred since aerogels have extremely high specific surface areas and, when cooled to cryogenic temperatures, are capable of absorbing gases such as oxygen. Alternatively, insulative blanket 132 may comprise spray- on foam insulation or expanded cork. A protective top layer or composite sheet 134, for example, comprising a breathable glass / composite layer is then applied over insulating blanket 132 and taped in place in step 146.

[0089] Referring to Fig. 10, in an alternative process, the insulating blanket 132 may be preformed on composite sheet 134 in an off-line step 148, and the pre-formed material is applied on the outer surface of the aerogel paper 130 and taped in place in step 150.

[0090] A feature and advantage of the instant disclosure which results from the bonding of aerogel paper directly to the outer surface of a cryogenic pipe is that the aerogel paper prevents ambient oxygen condensation and concentration at the cryogenic pipe surface. This in turn minimizes the risk of flammability, degraded performance, and failure / debris. Also, the scrim glass composite sheet over the insulative blanket allows the insulative blanket to “breathe”, preventing moisture buildup inside the insulative blanket.

[0091] It should be noted that in addition to bonding aerogel paper directly to the outer surface of the cryogenic pipe, aerogel paper also may be directly bonded to fittings on the pipe, as well as to bridge the area where the pipe is fitted to the fuel tank at one end and to the fuel cells at the other end.

[0092] While the foregoing disclosure has been described in connection with converting and retrofitting a fossil fuel-powered aircraft to a fuel cell-powered electric propulsor driven aircraft, the disclosure similarly may be used for converting a fossil fuel-burning aircraft to a hydrogen gas burning aircraft by replacing the fossil fuel tanks of the aircraft and related apparatus with cryogenic hydrogen fuel tanks in accordance with the present disclosure. Also, while the disclosure has been directed specifically to converting and retrofitting a conventional fossil fuel-powered aircraft with a hydrogen driven power train, the above-described cryogenic fuel tank design principles including aerodynamic shape, nose cone and tail cone shape, internal baffle designs, venting and nozzle designs, etc., also advantageously may be employed in purposely built hydrogen fuel-powered aircraft.

[0093] Also by way of example, but not limitation, the cryogenic piping advantageously may be employed as cryogenic fuel lines and / or liquid oxidant lines for rockets and space vehicles. The cryogenic piping also may be employed with conventional land and sea vehicles including, for example, LNG tankers, and as piping for fixed cryogenic storage tanks.

[0094] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, arc interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure. Various changes and advantages may be made in the above disclosure without departing from the spirit and scope thereof.List of References:10 airplane12 fuselage14 wing16 wing18 propulsor22 fuel cell24 fuel cell25 tank26 tank28 tank30 main body section32 ogive nose cone section34 tail cone section36 fill ports38 emergency dump valves40 pressure relief and thermal relieve valves42 vertical fin44 horizontal fin46 support pylons48 heat exchangers50 baffles52 nozzle(s)54 valve(s)55 baffles56 dividcr(s)58 fuel pumps60 couplers62 flow channels66 fixtures68 gauges70 sensors80 control system110 hydrogen fuel cell-powered aircraftfuselage wings electric motors propulsors hydrogen fuel cells cryogenic hydrogen fuel tank cryogenic fuel lines conduit or pipe resin layer aerogel paper insulative blanket composite sheet coating step wrapping step wrapping step step step step

Claims

What is Claimed:

1. A cryogenic insulated pipe comprising a pipe having:(a) a conformally-bonded aerogel paper layer on an outer surface of the pipe;(b) an insulative blanket over the aerogel paper; and(c) a breathable protective layer over the insulative blanket.

2. The cryogenic insulated pipe of claim 1, characterized by one or more of the following features:(a) wherein the conformally -bonded aerogel paper layer is conformally -bonded to the pipe outer surface in a pre-applied resin layer;(b) wherein the insulative blanket comprises an aerogel material, or wherein the insulative blanket comprises a spray-on foam or expanded cork;(c) wherein the cryogenic insulated pipe is configured to transport liquid hydrogen; and(d) wherein the breathable protective layer comprises a breathable glass composite material, wherein the breathable glass composite material preferably comprises a woven or braided glass sheet.

3. A method for forming a cryogenic insulated pipe as claimed in claim 1 or claim 2, comprising the steps in sequence of:(a) providing a pipe and covering an outer surface of the pipe with a conformally- bonded layer of aerogel paper;(b) adding an insulative blanket over the aerogel paper layer; and(c) adding a breathable protective layer over the thermal insulating layer.

4. The method of claim 3, characterized by one or more of the following features:(a) including the step of coating the outer surface of the pipe with a resin and wrapping the coated pipe with the aerogel paper before the resin sets;(b) wherein the insulative blanket comprises an aerogel;(c) wherein the insulative blanket comprises a spray-on foam or an expanded cork, or wherein the breathable protective layer comprises a breathable glass composite material; and(d) wherein the breathable glass composite material comprises a woven or braided glass sheet.

5. A vehicle comprising an insulated cryogenic pipe as claimed in claim 1 or claim 2.

6. The vehicle of claim 5, wherein the vehicle comprises a fuel cell-powered vehicle, preferably a fuel cell-powered aircraft, or a rocket.

7. A cryogenic fuel tank for aircraft, said cryogenic fuel tank having an aerodynamically shaped outer surface including an ogive shaped nose cone and a tapered tail cone, wherein said cryogenic fuel tank includes actively adjustable elements for adjusting aerodynamic characteristics of the cryogenic fuel tank; wherein the cryogenic fuel tank further includes a valve and nozzle configured to vent fuel from the tank in the event that the cryogenic fuel tank is jettisoned from the aircraft, where the venting fuel expanded through the nozzle can be used to propel the fuel tank.

8. The cryogenic fuel tank of claim 7, wherein the cryogenic fuel tank is configured to be attached below wings of the aircraft.

9. The cryogenic fuel tank of claim 8, wherein the cryogenic fuel tank is configured to be attached to wings of the aircraft through support pylons, wherein the support pylons preferably include sensors configured to measure forces applied by the cryogenic fuel tank to the airframe, wherein the sensors preferably include strain gauges, and further optionally including a controller configured to interpret signals from the sensors and to configure the aerodynamic elements to adjust loads on the aircraft.

10. The cryogenic fuel tank of any of claims 7-9, wherein the cryogenic tank includes dividers for dividing the cryogenic fuel tank into two or more bays and further including a pumping system to transfer fuel between bays to control the cryogenic fuel tank center of gravity, and / or wherein the cryogenic tank further includes pressure relief devices configured to vent fuel away from the cryogenic fuel tank in the event of over-pressure or overtemperature.

11. The cryogenic fuel tank of any of claims 7-10, further comprising a controller configured to control venting of the fuel.

12. An aircraft vehicle configured to be propelled by a cryogenic fuel and comprising a cryogenic fuel tank as claimed in any of clams 7-11.

13. The aircraft vehicle as claimed in claim 12, wherein the aircraft comprises a hydrogen fuel cell-powered aircraft, or a fossil fuel-burning aircraft vehicle retrofitted to run on hydrogen.

14. The aircraft vehicle of claim 12 or claim 13, wherein the cryogenic fuel tank is fixed to the pylons through integrally formed couplers, which include flow paths or flow channels configured for carrying fuel from an interior of the cryogenic fuel tank to a power train on the aircraft, and wherein the pylons preferably include ullage controls and / or gasifier heat exchangers.

15. The aircraft vehicle of claim 14, wherein the couplers include hard point fittings for mounting to support pylons, wherein the hard point fittings are configured to release the cryogenic fuel tanks so that they may be dropped or jettisoned under emergency conditions.

16. The aircraft vehicle of any of claims 7-15, wherein the cryogenic fuel tank includes a controller configured to control venting of fuel from the cryogenic fuel tank under emergency conditions.

Images