Patent Application
20200239152
The use of hydrogen fuel cells is being explored for powering both manned and unmanned aircraft. Fuel cells operate by facilitating an electrochemical reaction between hydrogen and oxygen, which produces electricity, water, and heat. Different types of fuel cells have different optimal operating temperature ranges and deviation from those optimal temperature ranges can result in decreased efficiency of the fuel cell. As such, it is important to maintain the fuel cell within the optimal temperature range.
Fuel cells typically utilize a finned tube, or plate tube, type heat exchanger that circulates a coolant through the fuel cell stack, drawing heat from the fuel cells and then passing the coolant through a serpentine pipe passing back and forth through a plurality of fins or plates. The fins serve to increase the surface area of the serpentine pipe to increase the thermal conduction from the pipe to the surrounding air.
While the making and using of various embodiments of this disclosure are discussed in detail below, it should be appreciated that this disclosure provides many applicable inventive concepts, which can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative and do not limit the scope of this disclosure. In the interest of clarity, not all features of an actual implementation may be described in this disclosure. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another.
In this disclosure, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of this disclosure, the devices, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as “above,” “below,” “upper,” “lower,” or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the device described herein may be oriented in any desired direction. In addition, the use of the term “coupled” throughout this disclosure may mean directly or indirectly connected, moreover, “coupled” may also mean permanently or removably connected, unless otherwise stated.
Typically, a fuel cell generates approximately 1 kW of waste heat per 1 kW of electricity generated. Accordingly, if an aircraft relies on a fuel cell for powering its propulsion system, the aircraft must be able to eliminate a large amount of waste heat. Compared to a rotary-wing aircraft, a fixed-wing aircraft requires significantly less power to maintain flight, and the constant forward motion of a fixed-wing aircraft provides an airflow that may be utilized to dissipate the waste heat generated by the fuel cell, for example, through the use of a ram air intake to channel air toward a conventional heat exchanger. However, a rotary-wing aircraft uses substantially more power to hover, therefore producing substantially more waste heat, without the benefit of airflow provide by movement of the aircraft. The thermal management system divulged herein provides for heat dissipation for a fixed-wing aircraft without the added mass of a conventional heat exchanger or a drag inducing ram air intake and provides for heat dissipation for a rotary-wing aircraft while hovering.
This disclosure divulges a thermal management system utilizing coolant passages formed in leading edges of an aircraft for heat dissipation. It further divulges a fuel cell powered aircraft utilizing tilting ducted fans for generating lift and thrust, wherein the ducted fans are configured to dissipate heat generated by the fuel cell. Placing a fan inside a properly designed duct may increase the amount of lift/thrust produced by the ducted fan arrangement compared to a fan without a duct. This may be accomplished, at least in part, because the fan accelerates the airflow over the leading edge of the duct, thereby decreasing the pressure above the duct, while behind the fan disk, the duct diverges to decelerate the air and return it to atmospheric pressure. In addition, flow-straightening stator vanes downstream of the fan disk recover rotational energy of the airflow, generating additional axial thrust. The location of the stator vanes immediately downstream of the fan disk subjects the leading edges of the stator vanes to increased velocity airflow. Similarly, the leading edges of aircraft surfaces experience a large airflow. As such, incorporation of coolant passages in any leading edges of the aircraft may be utilized for heat dissipation.
As mentioned above, the thermal management system divulged herein may reduce the overall mass of an aircraft by downsizing or eliminating the need for a conventional heat exchanger. And by incorporating the elements of the thermal management system into the preferred shapes of the aircraft components, it may reduce the overall mass without increasing the drag of the aircraft.
While the thermal management system described herein focuses on utilizing the leading edges of aircraft structures, because the airflow at those locations maximizes the potential heat transfer, the system may be utilized by incorporating coolant passages on any exterior surface of an aircraft. Moreover, while this disclosure focuses on utilizing the thermal management system for the dissipation of heat generated by a fuel cell, the thermal management system disclosed herein may be used with any heat source on an aircraft, such as an internal combustion engine, etc. Moreover, the thermal management system may include features that make functional usage of the waste heat. For example, the thermal management system may direct heated coolant through passages in a passenger compartment of the aircraft to maintain a comfortable cabin temperature.
Propulsion system 114 includes a first ducted fan 138 rotatably coupled to distal end 124 of first wing 118, via a spindle 139, about a tilt axis 140 and a second ducted fan 142 rotatably coupled to distal end 132 of second wing 120 about tilt axis 140. Propulsion system 114 further includes a third ducted fan 144, and a fourth ducted fan 146, rotatably coupled to first side 110 and second side 112 of fuselage 102 proximate nose section 104, respectively. Propulsion system 114 also includes and a fifth ducted fan 148, and a sixth ducted fan 150, rotatably coupled to first side 110 and second side 112 of tail section 108, respectively.
As best shown in
Fan 152 is driven in rotation about rotation axis 158 by an electric motor (not shown) housed within stator hub 172. As shown in
Still referring to
As mentioned above, the passages of thermal management system 116 may include passages located on any leading edge of aircraft 100, such as one or more conduits traversing a cover comprising first end 162 of duct 160, nose section 104 of fuselage 102, leading portion 126 of first wing 118, leading portion 134 of second wing 120, and/or any other leading edge of aircraft 100. However, for simplicity, the plurality of passages of thermal management system 116 are described herein with respect to a first stator vane 174A of plurality of stator vanes 174, with the understanding that the structure shown on, and discussed with reference to, first stator vane 174A may be modified and utilized on any leading surface of aircraft 100. Moreover, while
Referring now to
For weight savings, body 182 may preferably be made of a composite material, such as carbon fiber, fiberglass, etc., and abrasion strip 192 may preferably be made of a metal, such as aluminum, stainless steel, etc. Abrasion strip 192 may preferably be made of metal because it must to be able to withstand high temperatures transferred thereto by coolant 196. Because composite materials may be damaged by exposure to high temperatures, first stator vane 174A includes a void 198 between body 182 and abrasion strip 192 along the portion of spanwise width 178 that passages 194 extend, which may include the entirety of spanwise width 178. Void 198 is filled with air (or may be a vacuum) and serves to insulate leading end 184 of body 182 from the heat dissipating from coolant 196 passing through plurality of passages 194. Alternatively, body 182 and abrasion strip 192 may both be made of a metal. Additionally, first stator vane 174A may comprise a single unibody structure wherein abrasion strip 192 and body 182 are one piece made of a metal.
At least one embodiment is disclosed, and variations, combinations, and/or modifications of the embodiment(s) and/or features of the embodiment(s) made by a person having ordinary skill in the art are within the scope of the disclosure. Alternative embodiments that result from combining, integrating, and/or omitting features of the embodiment(s) are also within the scope of the disclosure. Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example, whenever a numerical range with a lower limit, Rl, and an upper limit, Ru, is disclosed, any number falling within the range is specifically disclosed. In particular, the following numbers within the range are specifically disclosed: R=Rl+k*(Ru−Rl), wherein k is a variable ranging from 1 percent to 100 percent with a 1 percent increment, i.e., k is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . 50 percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent, 95 percent, 98 percent, 99 percent, or 100 percent. Moreover, any numerical range defined by two R numbers as defined in the above is also specifically disclosed. Use of the term “optionally” with respect to any element of a claim means that the element is required, or alternatively, the element is not required, both alternatives being within the scope of the claim. Use of broader terms such as comprises, includes, and having should be understood to provide support for narrower terms such as consisting of, consisting essentially of, and comprised substantially of. Accordingly, the scope of protection is not limited by the description set out above but is defined by the claims that follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated as further disclosure into the specification and the claims are embodiment(s) of the present invention. Also, the phrases “at least one of A, B, and C” and “A and/or B and/or C” should each be interpreted to include only A, only B, only C, or any combination of A, B, and C.
