Patent Application
20240271754
The present disclosure relates generally to aircraft fuel storage systems and more particularly a light-weight cryogenic fluid storage system for flight vehicles.
Flight vehicle aerodynamics dictate that all components in the vehicle be as light as possible when accomplishing their function in order to maximize propulsion effectiveness and the flight range of the vehicle. This includes components used in fuel systems required to operate propulsion and power units on the vehicle. One particular case to examine is a liquid hydrogen fuel system used to operate a fuel cell power system that then can be used to operate electric propulsion systems.
Liquid hydrogen fuel systems are different than the hydro-carbon fuel systems typically used on flight vehicles. To stay in a liquid state at pressures less than 100 psi, liquid hydrogen must be stored between −434° F. and −406° F. (14 K to 30 K), which is much lower than the storage temperature of hydro-carbon fuels, which is near ambient temperature. Liquid hydrogen storage systems must be designed to operate at these extreme temperatures. Liquid hydrogen is typically stored in insulated containers, such as dewars, in order to minimize heat leak into the liquid hydrogen that will prematurely boil away the liquid hydrogen before it is used by the power system. Commercial ground based dewars for storing cryogenic liquids are designed for strength and durability. They are typically constructed from heavy stainless steel as the primary material. Commercial dewar designs are, therefore, heavy, and not practical for use in flight systems.
The combination of a) light weight and b) extreme temperature operation design constraints creates challenges for the use of liquid hydrogen as fuel for flight vehicles.
The innovation described herein takes into account the above requirements for storing and gasifying liquid hydrogen in a unique design that integrates and optimizes various subassemblies according to their required function to obtain a light-weight liquid hydrogen fuel flight storage system.
The present disclosure relates to a system for storing a cryogenic fluid and discharging a vapor. In accordance with an embodiment the system includes an inner tank, a heat exchanger in fluid communication with the inner tank, a cooling assembly, and an outer jacket assembly. The cooling assembly includes a cold plate heat exchanger and a bottom drain tube and a vapor return line fluidly connected to the inner tank and the cold plate heat exchanger such that liquid hydrogen from the inner tank feeds out the bottom drain tube and into the cold plate heat exchanger and vaporized hydrogen leaves the cold plate heat exchanger through the vapor return line to the inner tank.
The outer jacket assembly includes a first jacket cylinder and a second jacket cylinder. A first flange is affixed to the first jacket cylinder and a second flange is affixed to the second jacket cylinder. The outer jacket further includes a first connector body and second connector body, wherein the first connector body has a first face, and the second connector body has a second face, the connector bodies are configured such that they are disposed between the first and second flanges, when in a connected state the first face of the first connector body abuts the second face of the second connector body and at least one fastener connects the first and second flanges and the first and second connector bodies together. A first sealing ring is disposed between the first flange and the first connector body, and a second sealing ring disposed between the flange and second connector body. The outer jacket assembly encases the inner tank, the heat exchanger, and the cooling assembly.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate various example systems, methods, and so on, that illustrate various example embodiments of aspects of the invention. It will be appreciated that the illustrated element boundaries (e.g., boxes, groups of boxes, or other shapes) in the figures represent one example of the boundaries. One of ordinary skill in the art will appreciate that one element may be designed as multiple elements or that multiple elements may be designed as one element. An element shown as an internal component of another element may be implemented as an external component and vice versa. Furthermore, elements may not be drawn to scale.
The annexed drawings show various aspects of the disclosure.
The inner tank 12 is a lightweight pressure vessel boundary specifically designed with metallic materials (e.g., aluminum) that are compatible with liquid hydrogen and can hold from 1 to 6.8 atmospheres (0 to 100 psig) of pressure. The inner tank 12 may include a tank body 13, a first end cap 56, and a second end cap 58. The tank body 13 is preferably cylindrical in shape and preferably made of stainless steel, more preferably aluminum, more preferably titanium for storing the liquid hydrogen. The end caps 56, 58 may be made of a lightweight metal such as aluminum or titanium.
To interact with the tank interface flange subassembly 200 (see
The fill tube 64 may be constructed from a material that has a lower thermal conductivity than aluminum, such as stainless steel, to reduce heat conduction from the inner tank 12. The tube 64 may be kept relatively short to reduce weight of the overall system 10. The bi-metallic transition fitting 62 serves as interface between the two different metals and enables the optimization of light-weight and low heat leak, while containing liquid hydrogen at 21 K (−421° F.) under pressure.
The heat exchanger 14 is preferably constructed from high-thermal conductivity copper. The heat exchanger 14 is connected to the inner tank 12 by a discharge fitting tee 70 that connects a feed through 72 to a bi-metallic fitting 74 that connects to the second end cap 58. When pressurized, the inner vessel 12 will discharge ullage gas into the heat exchanger 14. The tubular heat exchanger 14 is disposed within the vacuum jacket 16 and may be insulated with multi-layer insulation to minimize external heat leak. The heat exchanger 14 may be heated by an electric heater (not shown) to warm the exiting gas. The tubular heat exchanger 14 may be traced with heating wire, preferably made from nichrome, that is connected to an external power supply and controller that provides an external source of heat to the coiled heat exchanger 14. The heat can be controlled to control the discharge vapor temperature at the outlet of the heat exchanger 14. The heater wire may be passed out of the vacuum jacket 16 through the removable compression fitting 80 along with the heat exchanger outlet tube 81. See
The outer jacket assembly 16 may further include a bi-metallic transition fitting 110 to connect the compression fitting 80 to the second end cap 108. The compression fitting 80 may be a Conax Technologies commercially available compression fitting for passing sensor and heater power wires. The transition fitting 110 may be a bi-metallic transition fitting to connect the stainless-steel compression fitting 80 to the aluminum end cap 108. The first end cap 106 may include a vacuum jacket pump out port 112 used for removing air from the vacuum jacket 16. The outer vacuum jacket assembly may be insulated with an appropriate insulation designed to operate in a vacuum. For example, the outer vacuum jacket may be insulated with multilayer insulation. The insulation may be easily removed and replaced because of the removable enclosures described herein.
The first end cap 106 and the first flange 24 attach (e.g., welded) to the first cylinder 20 while the second end cap 108 and second flange 26 attach (e.g., welded) to the second cylinder 22. The first and second end caps 106, 108 may be formed as flat disks or may be dished or semi-hemispherical in shape. As described in detail below, the first connector body 30 is attached to the second connector body 32. When the system 10 is assembled, the first connector body 30 is operably connected to the first jacket cylinder 20 and the second connector body 32 is operably connected to the second jacket cylinder 22. The outer jacket assembly 16 includes a first sealing ring 42 disposed between the first flange 24 and the first connector body 30, and a second sealing ring 44 disposed between the second flange 26 and the second connector body 32. The first and second sealing rings 42, 44 may be adhered to the first and second connector bodies 30, 32, respectively, by applying cryogenic rated epoxy. At least one fastener 40 may connect the first and second flanges 24, 26 to the first and second connector bodies 30, 32 and, thus, to each other.
The first and second flanges 24, 26 and first and second seal rings 42, 44 may have machined-in serrations for sealing on gaskets 43, 45 therebetween. The serrations may either be spiral or concentric and configured to dig into the between gaskets 43, 45 to form a seal. The gaskets 43, 45 may preferably be polytetrafluoroethylene (PTFE) gaskets. The first and second connector bodies 30, 32 may be made from high-pressure laminate such as garolite, G-10/FR-4, low-thermal conductivity type material. Fasteners 40 may be made of light-weight fiberglass. The first and second jacket cylinders 20, 22 may be made from durable, light-weight aluminum, and can be made in different lengths to accommodate various length inner tank assemblies and to accommodate any additional items to be cooled inside the vacuum environment such as, for example, sensors flown on the fight vehicle as payloads. The end caps 106, 108 may also be made from durable, light-weight aluminum.
The first connector body 30 has a first face 34, and the second connector body 32 has a second face 36. When connected together, the first face 34 of the first connector body 30 abuts the second face 36 of the second connector body 32.
The first connector body 30 may have a first semicircular opening 90, and the second connector body 32 a corresponding second semicircular opening 92. In the connected state the first and second semicircular openings 90, 92 form a circular aperture 94. The bi-metallic fitting 62 and/or the fill tube 64 fit inside the circular aperture 94 (and inside the aperture 102a of the vacuum jacket connection plate 102). The first connector body 30 may further have a first depression 96 and the second connector body 32 may have a second depression 98. When the first connector body and the second connector body 32 are connected, the depressions 96, 98 form a plate cavity 100 circumscribing the circular aperture 94. The vacuum jacket connection plate 102 (see
The inner tank 12, the heat exchanger 14, and the cooling assembly 18 are all encased when the outer jacket assembly 16 is in the connected state. When in the connected state, the outer jacket assembly 16 creates a vacuum seal around the inner tank 12, heat exchanger 14, and the cooling assembly 18.
The outer jacket assembly 16 is configured such that the first jacket cylinder 20 and the second jacket cylinder 22 are independently removable to access the inner tank 12. The independently removable jacket cylinders 20, 22 are advantageous because it allows access to the inner tank 12 and its associated components without having to dismantle the entire flight storage system 10. This cuts down on cost and time of maintenance of the flight storage system 10. Many conventional storage systems are constructed from a solid outer jacket that cannot be easily disassembled to access the inner tank.
Returning to
The following includes definitions of selected terms employed herein. The definitions include various examples or forms of components that fall within the scope of a term and that may be used for implementation. The examples are not intended to be limiting. Both singular and plural forms of terms may be within the definitions.
An “operable connection,” or a connection by which entities are “operably connected,” is one in which signals, physical communications, or logical communications may be sent or received. Typically, an operable connection includes a physical interface, an electrical interface, or a data interface, but it is to be noted that an operable connection may include differing combinations of these or other types of connections sufficient to allow operable control. For example, two entities can be operably connected by being able to communicate signals to each other directly or through one or more intermediate entities like a processor, operating system, a logic, software, or other entity. Logical or physical communication channels can be used to create an operable connection.
To the extent that the term “includes” or “including” is employed in the detailed description or the claims, it is intended to be inclusive in a manner similar to the term “comprising” as that term is interpreted when employed as a transitional word in a claim. Furthermore, to the extent that the term “or” is employed in the detailed description or claims (e.g., A or B) it is intended to mean “A or B or both.” When the applicants intend to indicate “only A or B but not both” then the term “only A or B but not both” will be employed. Thus, use of the term “or” herein is the inclusive, and not the exclusive use. See, Bryan A. Garner, A Dictionary of Modern Legal Usage 624 (2d. Ed. 1995).
While example systems, methods, and so on, have been illustrated by describing examples, and while the examples have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit scope to such detail. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the systems, methods, and so on, described herein. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Thus, this application is intended to embrace alterations, modifications, and variations that fall within the scope of the appended claims. Furthermore, the preceding description is not meant to limit the scope of the invention. Rather, the scope of the invention is to be determined by the appended claims and their equivalents.
