THERMAL MANAGEMENT SYSTEM AND METHOD FOR AIRCRAFT FUEL CELLS

A fuel cell thermal management system and method for aerodynamic vehicles (such as aircraft) having propulsion systems powered by hydrogen fuel cells. The system and method reduce the overall amount of energy required to operate a propulsion system, which in turn reduces cooling requirements and improves efficiency. A cabin air reuse system uses cabin exhaust air as input air for the fuel cell. Because the cabin exhaust air is compressed, this saves the work involved in compressing air for input to the fuel cell.

TECHNICAL FIELD

This invention relates generally to the field of hydrogen fuel cell systems, and, more specifically, to thermal management of hydrogen fuel cell systems on aerodynamic vehicles such as electrically-powered or hybrid-powered aircraft.

BACKGROUND

A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells have been used to generate electrical power in many applications. Fuel cells are used for primary and backup power for commercial, industrial, and residential buildings and in remote or inaccessible areas. They are also used to power fuel cell vehicles, including forklifts, automobiles, buses, trains, boats, motorcycles, and submarines.

Fuel cell vehicles are powered by hydrogen that is fed into an onboard fuel cell “stack,” which transforms the hydrogen's chemical energy into electrical energy. This electricity is then available to power the vehicle and its onboard systems.

Hydrogen supplied to a fuel cell enters the anode, where it comes in contact with a catalyst that promotes the separation of hydrogen atoms into an electron and proton. The electrons are gathered by the conductive current collector, which is connected to the vehicle's high-voltage circuitry, feeding an onboard battery and/or electric motors that propel the vehicle. The byproduct of the reaction occurring in the fuel cell stack is water vapor, which is emitted through an exhaust.

Also included in fuel cell powered vehicles is a “balance-of-plant,” which contains all of the other components of a fuel cell system except the stack itself. This includes pumps, sensors, heat exchanger, gaskets, compressors, recirculation blowers or humidifiers, and so forth.

DETAILED DESCRIPTION

The following description of examples of the invention is not intended to limit the invention to these examples, but rather to enable any person skilled in the art to make and use this invention.

General Overview

Hydrogen fuel cells, as well as other types of non-combustion turbine propulsion power systems, have large cooling requirements. This can make designing a cooling system for fuel cells on aerodynamic vehicles quite challenging. As used herein, the phrase “aerodynamic vehicle” includes vehicles moving through air that are affected by aerodynamics forces. This includes aircraft and automobiles. In examples where the aerodynamic vehicle is an aircraft, cooling the one or more fuel cells powering an electric or hybrid aircraft may be done with air.

The fuel cell thermal management system and method described herein reduces the overall amount of energy required to operate a propulsion system on an aerodynamic vehicle, particularly aircraft. This reduces the cooling requirement for the fuel cell. A cabin air reuse system uses cabin exhaust air as input air for the fuel cell. Because the cabin exhaust air is at least somewhat compressed, this saves the work involved in compressing air for input to the fuel cell.

At altitudes where pressurization is needed, a compressor provides pressurized air for the aircraft cabin. The air within the cabin is continually exchanged for new air from the compressor, and the old air is exhausted from the cabin. This cabin exhaust air typically contains a small amount of carbon dioxide (CO2). The cabin air reuse system takes this cabin exhaust air and use it as input air to the stack of fuel cells, or fuel cell stack. This avoids wasting additional energy compressing air. Instead of dumping this cabin exhaust air, which contains most of the oxygen put into the cabin, it is reused in the fuel cell stack. This increases the overall efficiency by reducing the amount of air that needs to be compressed, thereby reducing the cooling requirements for the compressor, which avoid having to compress additional air for the fuel cell stack.

DESCRIPTION

FIG.1is a plan view of an aerodynamic vehicle in the form of an aircraft100according to some examples. The aircraft100includes a fuselage114, two wings112, an empennage110, and propulsion systems108embodied as ducted fans or rotor assemblies116located in nacelles102. The aircraft100includes one or more fuel cell stacks embodied inFIG.1as nacelle fuel cell stacks104and wing fuel cell stacks106. One or more heat exchangers120are located in the wings112, the fuselage114, nacelles102, or other locations. It should be noted that the fuel cell stacks104,106and heat exchangers120in some examples are positioned in locations other than those shown inFIG.1. For instance, in some examples, the fuel cell stacks and heat exchangers are located in one or more of the leading edges of wings or other aerosurfaces, wing nacelles, fuselage noses or in scoops sticking out from the sides of aircraft fuselages, wings, or nacelles.

The aircraft100will also typically include associated equipment such as an electronic infrastructure, control surfaces, a cooling system, landing gear and so forth. The wings112function to generate lift to support the aircraft100during forward flight. In some examples the wings112can additionally or alternately function to structurally support the fuel cell stacks104,106and/or propulsion systems108under the influence of various structural stresses (e.g., aerodynamic forces, gravitational forces, propulsive forces, external point loads, distributed loads, and/or body forces, and so forth).

FIG.2is a schematic view of an energy supply system200for an aerodynamic vehicle (such as an aircraft100) according to some examples. As shown, the energy supply system200includes one or more fuel cells212. Each fuel cell212may include one or more fuel cell stacks208. Typically associated with a fuel cell212are a source of hydrogen such as a liquid or compressed gaseous hydrogen tank118, a recirculation system202for supplying and returning hydrogen to the fuel cell212, a coolant fluid circulation system204for transferring heat, power electronics206for regulating delivery of electrical power from the fuel cells212during operation and to provide integration of the fuel cells212with the electronic infrastructure of the aircraft100, and a compressor/cathode air system210for providing compressed air to the fuel cells212. The electronic infrastructure can include an energy supply management system, for monitoring and controlling operation of the fuel cells212.

The fuel cells212function to convert chemical energy into electrical energy for supply to the propulsion systems108. Fuel cells212can be arranged and/or distributed about the aircraft100in any suitable manner. Fuel cell stacks can be arranged within wings (e.g., inside of an airfoil cavity), inside nacelles, and/or, as discussed below, in any other suitable location on the aircraft.

Also provided may be one or more battery packs for energy storage for start-up, for peak power loads, load following, and also for control and avionics safety in case of a failure in the fuel cell system. In some examples this provides a hybrid fuel cell and battery pack system, in which the propulsion systems108are powered jointly or alternately by the fuel cells212and battery packs, and in which the fuel cells recharge the battery packs as needed.

The energy supply system200can optionally include a heat transfer system (e.g., fluid circulation system204) and/or that functions to transfer heat from or to various components of the aircraft100, for example by circulating a working fluid within a fuel cell212to remove heat generated during operation, to provide heat for evaporation of liquid hydrogen from the tank118, or to remove heat from other heat-generating components within the aircraft100.

FIG.3is a schematic diagram of a fuel cell thermal management system300according to some examples. The fuel cell thermal management system300in some examples is an energy supply system (such as the energy supply system200shown inFIG.2), such as may be used to provide power to an aircraft. In other examples, the fuel cell thermal management system300is a compressor/cathode air system (such as the compressor/cathode air system210shown inFIG.2).

As shown inFIG.3, in some examples the fuel cell thermal management system300includes an airfoil302and an integrated air-cooling system303. The integrated air-cooling system303includes a heat exchanger304, variable-geometry openings, and, in some examples, a fan309, all contained within a cavity306. The variable-geometry openings include one or more of a variable-geometry inlet301and a variable-geometry outlet305. The variable-geometry inlet301and a variable-geometry outlet305are used, either alone or in any combination, to control the amount of cooling airflow311flowing through the cavity306dependent upon the fuel cell cooling requirements. Although shown inFIG.3as located within a wing, it should be noted that the integrated air-cooling system303can be located anywhere on the aircraft100, including the fuselage114, nacelles102, and a scoop located on the fuselage114, nacelles102, and wings112.

Air enters the cavity306via the variable-geometry inlet301. The incoming air undergoes a small amount of pressurization at it enter the variable-geometry inlet301due to the dynamic pressure. Air is tapped at a location313in the cavity306where there is a low-speed airflow and used as input air to the compressors.

The heat exchanger304can be a radiator, a fin-tube heat exchanger, and so forth. During operation, the cooling airflow311enters the cavity306and passes across and/or through the heat exchanger304. A coolant, such as water, glycol, and so forth, flows through a supply line308and a return line310to cool various components of system300as disclosed herein. By way of example, the coolant passes through a heat exchanger where it transfers heat from the fuel cell to the coolant, and the coolant is passed through the heat exchanger304where the heat is transferred from the coolant to the cooling airflow311.

In some examples, the fan309is used to draw the cooling airflow311into the cavity306. When cooling requirements are high, for example, while the aircraft100is on the ground and not in motion, the fan309is used to draw the cooling airflow311into the cavity306via the variable-geometry inlet301, which is adjustable in size, and across the heat exchanger304. WhileFIG.3illustrates fan309in front of the heat exchanger304, it should be noted that the fan309may be located aft of the heat exchanger304.

A water spray system307, in some examples, sprays coolant, such as water, onto the heat exchanger304. The water spray system307is typically used during ground operations and in other instances when there are additional cooling requirements. In some examples, water for the water spray system307is collected from the condensate of the exhaust of a fuel cell stack316. As such, the water spray system307may be self-replenishing. For example, a water accumulation tank may be located proximate a condenser to collect condensate from fuel cell stack316.

In some examples, the fuel cell thermal management system300includes various components for exchanging heat and energy, including heat exchangers312,321, and334, compressors320,322and324, and variable-geometry turbines (VGT)340,342and344, the functions of which will be described below. It will be appreciated that not all the components of the fuel cell thermal management system300are required in any example, or that the number of any component may vary in the fuel cell thermal management system300.

The coolant in the fluid loop to and from the heat exchanger304in some examples flows through the heat exchanger312. The coolant heats liquid hydrogen (LH2) flowing from a liquid hydrogen tank314. Heating the liquid hydrogen allows the hydrogen to be gasified and warmed to the temperature required by the fuel cell stack316. Gaseous hydrogen is often desirable in some examples to avoid condensing oxygen or otherwise freezing various components of the fuel cell thermal management system300. For example, the temperature of liquid hydrogen is approximately negative 250° C. At this temperature, any water vapor or other gasses with a higher condensing or freezing temperature that may contact the hydrogen may liquify or solidify. This may cause blockages within plumbing and potentially other problems during operation of fuel cell thermal management system300.

The heated hydrogen flows to the fuel cell stack316. The coolant also flows to the fuel cell stack316via a return line310. After cooling the fuel cell stack316, the coolant returns to heat exchanger304via a return line308. In addition to, or instead of flowing through heat exchanger312, in some examples the coolant bypasses the heat exchanger312via a bypass line318. In some examples, the coolant leaving the fuel cell stack316goes to the heat exchanger312first, before going to the heat exchanger304, since the outlet of the fuel cell stack316typically is the hottest coolant location in the fuel cell thermal management system300.

As shown inFIG.3, some examples of the fuel cell thermal management system300includes a multi-stage compressor system. In the examples shown inFIG.3, the multi-stage compressor system is a three-stage compressor system including a low-pressure (LP) stage333, a medium-pressure (MP) stage335, and a high-pressure (HP) stage337. Air flows through a first compressor320, a low-pressure compressor corresponding to the LP stage333, a second compressor322, a medium-pressure compressor corresponding to the MP stage335, and a third compressor324, a high-pressure compressor corresponding to the HP stage337. In each of these three stages the air compressed and consequently heated.

The three-stage compression system manages all altitudes from sea level to high altitude while still delivering 2 to 3 bar of pressurized air to the third compressor324at less than the operating temperature of the fuel cell stack316, which is typically about 70-80 C. If the aircraft100is operating at high altitudes, then up to three stages of compression are used. However, at lower altitudes one or more of the compressor stages is bypassed, using the bypass valves315,317at lower altitudes. In other words, bypass valves315,317provide a way to modulate the airflow around those compressor stages that are not needed.

In some examples, air from one or more of the compressors320,322,324is passed via a duct326to a cabin recuperative heat exchanger328. The cabin recuperative heat exchanger328pre-conditions the air used in a cabin330of the aircraft100. Preconditioning the cabin air in some examples includes heating or cooling the air to within a predetermined temperature range before passing the air into a cabin air heater or cooler332. If necessary, the cabin air heater or cooler332either adds or subtracts heat from the preconditioned air to make it usable in as cabin air. For example, a coolant may flow through the cabin air heater or cooler332and pass the heat exchanger334to heat or cool air flowing into the cabin once the air has been pretreated via the cabin recuperative heat exchanger321. In some examples, the output of the second compressor322is maintained at the required cabin air pressure to provide pressurized cabin air at altitude.

In general, the recuperative heat exchanger321reduces the temperature of hot compressor air prior to entering the cabin, and thus reduces the load on the cabin cooling system. Specifically, air from the compressors is run through the recuperative heat exchanger321against the air that is exiting the cabin330. This reduces the amount of heating or cooling needed for the incoming cabin air.

In the unusual event that the recuperated compressor air is too cold (such as at sea level on a cold day) the recuperative heat exchanger321reduces demand on the cabin heating system. For high altitude cruise, the compressor outlet air will be too hot for human habitation and the primary purpose of the recuperative heat exchanger321is to make the air fit for habitation (or closer to it). This is done while keeping heat within the inlet air compressor/exhaust air turbine cycle (as opposed to, for example, treating the compressor air with a ram-air heat exchanger from external airstream) to reduce shaft power demands on the inlet air compressor/exhaust air turbine system (compressors320,322,324and turbines340,342and344). To ensure adequate flow across the recuperative heat exchanger321, a pump323used in some examples The pump323is used to overcome frictional losses within the fuel cell thermal management system300and to supply adequate air to the recuperative heat exchanger321.

In addition to, or as an alternative to, heating from the compressors320,322, and324, coolant is received at heat exchanger334via a supply line348from the heat exchanger312. The coolant is used in some examples to cool the heat exchanger334so that the cabin air can be cooled for passenger comfort. After flowing over the heat exchanger334, the coolant is returned to the heat exchanger304via a return line350. The use of coolant via the supply line348allows the coldest coolant available to be used for conditioning the cabin, since the coolant in other systems may be about 70° C. or 80° C.

The compressors320,322, and324compress air that is used in part for the fuel cell stack316. As noted above, the compressors320,322, and324are part of a three-stage compressor system and allow the fuel cell stack316to work at a variety of ambient pressures. For example, at high altitudes compressors320,322,324compress ambient air, which this is supplied to the fuel cell stack316. Due to the varying pressures experienced during changes of altitude and speed of the aircraft100, different stages of compression can be achieved using the three-stage compressor system that includes the compressors320,322, and324.

A bypass valve327, in some examples, is used to control the flow of air to the fuel cell stack316. During operations where there are lower pressures and flows to the fuel cell stack316, the valve327is used to allow larger portions of air flowing from the compressors320,322, and324to bypass the fuel cell stack316. This bypassed air is sent to a low nitrous oxide (NOx) combustor329where it is combusted and the exhaust331is expelled through the cavity306near the variable-geometry outlet305of the airfoil302.

Another way of controlling the flow to the fuel cell stack316is through a series of “backpressure” valves located in the exhaust downstream of the fuel cell stack316. These bypass valves include a first bypass valve355, a second bypass valve357, and a third bypass valve359. Examples may include one or more, or none of the first bypass valve355, second bypass valve357, and third bypass valve359. These bypass valves355,357,359allow the bypass of certain turbines that are not needed or not being used, so that compressor stages that are not needed are not left running.

As shown inFIG.3, the compressors320,322, and324, may be connected to fixed or variable flow or variable geometry turbines (VGT)340,342, and344. It should be noted that the use of variable geometry turbines340,342, and344alleviates the need for the first bypass valve355, the second bypass valve357, and the third bypass valves359. In addition, the first bypass valve355, the second bypass valve357, and the third bypass valves359are in some examples to allow air to bypass the three compressor stages. Variable geometry turbines340,342, and344are driven by fuel cell exhaust gas in some examples, to provide additional work to assist the compressors320,322, and324.

Prior to flowing into the fuel cell stack316, air may flow through a recuperative heat exchanger338. The recuperative heat exchanger338is used in some examples to precondition air flowing into the fuel cell stack316. For example, recuperative heat exchanger338may cool air having an elevated temperature due to compression to lower the temperature to the operating temperature of the fuel cell stack316.

The recuperative heat exchanger138receives exhaust air from the fuel cell stack316after it has passed through a humidifier. The recuperative heat exchanger338transfers heat from the air from compressors320,322and324to the exhaust air from the fuel cell stack316, prior to the exhaust air being provided to the turbines340,342, and344.

An inlet air cooler339receives chilled coolant from the heat exchanger312. For example, water, or any other coolant, that is used to vaporize the liquid hydrogen in the heat exchanger312is routed through the inlet air cooler339and used to cool the air from compressors320,322and324before it is supplied to the fuel cell stack316to or below the operating temperature of the fuel cell stack316.

As shown inFIG.3, the humidity controls are shown around the inlet air cooler339. These are standard humidity controls341that are used to ensure ion exchange within each of the fuel cells. The inlet air being delivered to the fuel cell should have an appropriate level of humidity and this is achieved by recovering some water from the fuel cell exhaust. This is done in a humidifier, which in some examples is a collection of membranes that allow water to migrate from the fuel cell exhaust to the fuel cell inlet. In this way air entering the fuel cell has the proper humidity.

In some examples, the hydrogen cooling provided by the heat exchanger312is also used for cooling other systems or components (in addition to the fuel cell stack316). These systems or components include power electronics, superconducting machines and so forth. The liquid hydrogen from the liquid hydrogen tank314is extremely cold, which makes it a good “quality” heat sink. Additional coolant loops are provided in some examples to such systems or components, either from the heat exchanger312or as part of one of the other coolant loops, such as the loop including the heat exchanger304.

Cabin Air Reuse

As noted above with respect toFIG.3, at altitudes where cabin pressurization is required, some examples of the fuel cell thermal management system300use the multi-stage compressor system to provide pressurized air for the cabin. Another feature of some examples of the fuel cell thermal management system300is a cabin air reuse system400, shown inFIG.4.FIG.4is a schematic diagram of the cabin air reuse system400portion of the fuel cell thermal management system300according to some examples.

In general, the cabin air reuse system400takes cabin exhaust air (that may contain a small amount of carbon dioxide (CO2)) and exchanges that air for new air. The cabin exhaust air is bled off or released from the cabin330and additional fresh air is added to the cabin. Some examples of the cabin air reuse system400take the cabin exhaust air that was released from the cabin330and put it back into the fuel cell stack316. This avoids wasting additional energy compressing air because the air is at least partially compressed. The energy saved by not compressing additional air for the fuel cell stack316also reduces the overall heat generated by the fuel cell thermal management system300, thereby reducing cooling requirements for the fuel cell stack316. In other words, the compressor does not have to compress additional air for the fuel cell due to the use of conditioned cabin exhaust air in the fuel cell. This serves to reduce the heat generated by the compressor.

Referring toFIG.4, cabin exhaust air is bled off or released from the cabin330via a cabin air bleed mechanism405. The cabin air bleed mechanism captures the released air as cabin exhaust air. The cabin exhaust air enters the cabin recuperative heat exchanger321where it is either heated or cooled, depending on the temperature of the cabin exhaust air, to match the temperature requirements of input air for the fuel cell stack316. Coming out of the cabin recuperative heat exchanger321, the cabin exhaust air either goes into the third compressor324(based on a position of a bypass valve410) or bypasses the third compressor324. The cabin exhaust air is around 0.7 to 0.8 bar, which is the cabin pressurization level. Typically, the cabin exhaust air will need to be at a higher pressure before being used by the fuel cell stack316.

This is achieved by adjusting the cabin exhaust air go into the third compressor324where it is compressed and exits at about 2.5 bar. This adjusts the pressure of the cabin exhaust air to comply with air pressure requirements of input air for the fuel cell stack316to obtain conditioned cabin exhaust air. The cabin exhaust air then flows into the recuperative heat exchanger338. As discussed above, the recuperative heat exchanger338is used in some examples to precondition air flowing into the fuel cell stack316. For example, recuperative heat exchanger338may cool air having an elevated temperature due to compression to lower the temperature to the operating temperature of the fuel cell stack316. In this manner the cabin exhaust air, instead of being released overboard, is reused and passed to the fuel cell stack316for its use to avoid having to compress additional air.

FIG.5is a flow diagram illustrating the details of a fuel cell thermal management method according to some examples of this disclosure. The method500begins in operation510by releasing and capturing air from a pressurized cabin on an aircraft. The released air is captured as cabin exhaust air. The method500performs operation520by adjusting a pressure of the cabin exhaust air. This obtains conditioned cabin exhaust air that complies with the air pressure requirements of input air for the fuel cell. The fuel cell will have a range of pressures and temperatures that the input air should be at prior to being used by the fuel cell.

The method then performs operation530to further condition the conditioned exhaust air by ensuring that a temperature of the cabin exhaust air complies with air temperature requirements of the input air for the fuel cell. In some examples, a cabin recuperative heat exchanger is used to either heat or cool the cabin exhaust air to obtain the conditioned cabin exhaust air. If the temperature of the cabin exhaust air is below the air temperature requirements, then the cabin exhaust air is heated to comply with the air temperature requirements. On the other hand, if the temperature of the cabin exhaust air is above the air temperature requirements, then the cabin exhaust air is cooled to comply with the air temperature requirements.

In some examples, the method500includes operation540of using a recuperative heat exchanger to cool a temperature of the conditioned cabin exhaust air before being used by the fuel cell. Finally, the method500performs operation550of supplying the conditioned cabin exhaust air to the fuel cell for use by the fuel cell. This need to not have to compress additional air for the fuel cell serves to reduce the work of the compressor and the fuel cell.

FIG.6illustrates a diagrammatic representation of a machine600in the form of a computer system within which a set of instructions may be executed for causing the machine to perform any one or more of the methodologies discussed herein, according to an example. For example, the power electronics206shown inFIG.2may be embodied as the machine600.

Specifically,FIG.6shows a diagrammatic representation of the machine600in the example form of a computer system, within which instructions608(e.g., software, a program, an application, an applet, an app, or other executable code) for causing the machine600to perform any one or more of the methodologies discussed herein may be executed. The instructions608transform the general, non-programmed machine600into a particular machine600programmed to carry out the described and illustrated functions in the manner described. In alternative examples, the machine600operates as a standalone device or may be coupled (e.g., networked) to other machines. In a networked deployment, the machine600may operate in the capacity of a server machine or a client machine in a server-client network environment, or as a peer machine in a peer-to-peer (or distributed) network environment. The machine600may comprise, but not be limited to, a server computer, a client computer, a personal computer (PC), a tablet computer, a laptop computer, a netbook, a set-top box (STB), a PDA, an entertainment media system, a cellular telephone, a smart phone, a mobile device, a wearable device (e.g., a smart watch), a smart home device (e.g., a smart appliance), other smart devices, a web appliance, a network router, a network switch, a network bridge, or any machine capable of executing the instructions608, sequentially or otherwise, that specify actions to be taken by the machine600. Further, while only a single machine600is illustrated, the term “machine” shall also be taken to include a collection of machines600that individually or jointly execute the instructions608to perform any one or more of the methodologies discussed herein.

The machine600may include processors602, memory604, and I/O components642, which may be configured to communicate with each other such as via a bus644. In an example, the processors602(e.g., a Central Processing Unit (CPU), a Reduced Instruction Set Computing (RISC) processor, a Complex Instruction Set Computing (CISC) processor, a Graphics Processing Unit (GPU), a Digital Signal Processor (DSP), an ASIC, a Radio-Frequency Integrated Circuit (RFIC), another processor, or any suitable combination thereof) may include, for example, a processor606and a processor610that may execute the instructions608. The term “processor” is intended to include multi-core processors that may comprise two or more independent processors (sometimes referred to as “cores”) that may execute instructions contemporaneously. AlthoughFIG.6shows multiple processors602, the machine600may include a single processor with a single core, a single processor with multiple cores (e.g., a multi-core processor), multiple processors with a single core, multiple processors with multiples cores, or any combination thereof.

The memory604may include a main memory612, a static memory614, and a storage unit616, both accessible to the processors602such as via the bus644. The main memory604, the static memory614, and storage unit616store the instructions608embodying any one or more of the methodologies or functions described herein. The instructions608may also reside, completely or partially, within the main memory612, within the static memory614, within machine-readable medium618within the storage unit616, within at least one of the processors602(e.g., within the processor's cache memory), or any suitable combination thereof, during execution thereof by the machine600.

In further examples, the I/O) components642may include biometric components632, motion components634, environmental components636, or position components638, among a wide array of other components. For example, the biometric components632may include components to detect expressions (e.g., hand expressions, facial expressions, vocal expressions, body gestures, or eye tracking), measure biosignals (e.g., blood pressure, heart rate, body temperature, perspiration, or brain waves), identify a person (e.g., voice identification, retinal identification, facial identification, fingerprint identification, or electroencephalogram-based identification), and the like. The motion components634may include acceleration sensor components (e.g., accelerometer), gravitation sensor components, rotation sensor components (e.g., gyroscope), and so forth. The environmental components636may include, for example, illumination sensor components (e.g., photometer), temperature sensor components (e.g., one or more thermometers that detect ambient temperature), humidity sensor components, pressure sensor components (e.g., barometer), acoustic sensor components (e.g., one or more microphones that detect background noise), proximity sensor components (e.g., infrared sensors that detect nearby objects), gas sensors (e.g., gas detection sensors to detection concentrations of hazardous gases for safety or to measure pollutants in the atmosphere), or other components that may provide indications, measurements, or signals corresponding to a surrounding physical environment. The position components638may include location sensor components (e.g., a GPS receiver component), altitude sensor components (e.g., altimeters or barometers that detect air pressure from which altitude may be derived), orientation sensor components (e.g., magnetometers), and the like.

Communication may be implemented using a wide variety of technologies. The I/O components642may include communication components640operable to couple the machine600to a network620or devices622via a coupling624and a coupling626, respectively. For example, the communication components640may include a network interface component or another suitable device to interface with the network620. In further examples, the communication components640may include wired communication components, wireless communication components, cellular communication components, Near Field Communication (NFC) components, Bluetooth® components (e.g., Bluetooth® Low Energy), Wi-Fi® components, and other communication components to provide communication via other modalities. The devices622may be another machine or any of a wide variety of peripheral devices (e.g., a peripheral device coupled via a USB).

Executable Instructions and Machine Storage Medium

The various memories (i.e., memory604, main memory612, static memory614, and/or memory of the processors602) and/or storage unit616may store one or more sets of instructions and data structures (e.g., software) embodying or utilized by any one or more of the methodologies or functions described herein. These instructions (e.g., the instructions608), when executed by processors602, cause various operations to implement the disclosed examples.

Transmission Medium

Additional Notes

The following, non-limited examples, detail certain aspects of the present subject matter to solve the challenges and provide the benefits discussed herein, among others.

Example 1 is a method of thermal management of a fuel cell on an aircraft, the aircraft having a pressurized cabin, the method comprising: releasing air from the pressurized cabin and capturing the released air as cabin exhaust air; adjusting a pressure of the cabin exhaust air to comply with air pressure requirements of input air for the fuel cell to obtain conditioned cabin exhaust air; and supplying the conditioned cabin exhaust air to the fuel cell for use in the fuel cell to reduce cooling requirements of the fuel cell.

In Example 2, the subject matter of Example 1 includes, ensuring that a temperature of the cabin exhaust air complies with air temperature requirements of the input air for the fuel cell to obtain the conditioned cabin exhaust air.

In Example 3, the subject matter of Example 2 includes, using a cabin recuperative heat exchanger to either cool or heat the cabin exhaust air to obtain the conditioned cabin exhaust air.

In Example 4, the subject matter of Example 3 includes, determining that the temperature of the cabin exhaust air is lower than the air temperature requirements for the input air for the fuel cell; and, heating the cabin exhaust air so that the temperature of the cabin exhaust air meets the air temperature requirements of the input air for the fuel cell.

In Example 5, the subject matter of Examples 3-4 includes, determining that the temperature of the cabin exhaust air is higher than the air temperature requirements for the input air for the fuel cell; and, cooling the cabin exhaust air so that the temperature of the cabin exhaust air meets the air temperature requirements of the input air for the fuel cell.

In Example 6, the subject matter of Examples 1-5 includes, where adjusting a pressure of the cabin exhaust air to comply with air pressure requirements of input air for the fuel cell further comprises compressing and then cooling the cabin exhaust air to obtain the conditioned cabin exhaust air.

In Example 7, the subject matter of Example 6 includes, wherein the cabin exhaust air is compressed using a compressor on the aircraft and wherein the compressor also provides compressed air to the fuel cell.

In Example 8, the subject matter of Example 7 includes, wherein the compressor does not have to compress additional air for the fuel cell due to the use of conditioned cabin exhaust air in the fuel cell, thereby reducing heat generated by the compressor.

In Example 9, the subject matter of Examples 7-8 includes, using a three-stage compressor to compress the cabin exhaust air to obtain the conditioned cabin exhaust air, wherein the three-stage compressor includes a low-pressure compressor, a medium-pressure compressor, and a high-pressure compressor.

In Example 10, the subject matter of Example 9 includes, using a recuperative heat exchanger to cool a temperature of the conditioned cabin exhaust air before being used by the fuel cell.

Example 11 is a fuel cell thermal management system for an aircraft, comprising: an integrated air-cooling system having a heat exchanger located in a cavity on the aircraft; a fuel cell in fluid communication with the heat exchanger for transferring heat from the fuel cell to the heat exchanger; at least one compressor on the aircraft for compressing air prior to the air entering the fuel cell; and a cabin air bleed mechanism for releasing and capturing cabin air from a pressurized cabin of the aircraft and using this cabin exhaust air as input air to the fuel cell.

In Example 12, the subject matter of Example 11 includes, a cabin recuperative heat exchanger for either heating or cooling the cabin exhaust air such that a temperature of the cabin exhaust air approximately matches air temperature requirements for input air to the fuel cell.

In Example 13, the subject matter of Examples 11-12 includes, wherein the at least one compressor is a three-stage compressor system having a first low-pressure compressor, a second medium-pressure compressor, and a third high-pressure compressor.

In Example 14, the subject matter of Example 13 includes, bar for use as the input air to the fuel cell.

In Example 15, the subject matter of Examples 13-14 includes, a recuperative heat exchanger for cooling a temperature of the cabin exhaust air, after compression by the three-stage compressor system and before being used by the fuel cell.

In Example 16, the subject matter of Examples 11-15 includes, wherein the integrated air-cooling system further comprises: a variable-geometry outlet at one end of the cavity for controlling an amount of cooling airflow passing through the cavity and over the heat exchanger; a fan located in the cavity; wherein the integrated air-cooling system is located on one or more of: (a) a wing of the aircraft; (b) a fuselage of the aircraft; (c) a nacelle of the aircraft.

In Example 17, the subject matter of Examples 11-16 includes, a water spray system arranged to spray water onto surfaces of the heat exchanger.

In Example 18, the subject matter of Example 17 includes, a water accumulation tank that provides water to the water spray system and collects the water from exhaust of the fuel cell.

Example 19 is a method for reusing cabin exhaust air from pressurized cabin of an aircraft, comprising: releasing and capturing the cabin exhaust air from the pressurized cabin; conditioning the cabin exhaust air to adjust its pressure and temperature to obtain conditioned cabin exhaust air and to comply with air pressure requirements and air temperature requirements of input air for a fuel cell located on the aircraft; and supplying the conditioned cabin exhaust air to the fuel cell for use by the fuel cell.

In Example 20, the subject matter of Example 19 includes, increasing the pressure of the cabin exhaust air by using a high-pressure compressor on the aircraft, wherein the high-pressure compressor is part of a three-stage compressor system also having a low-pressure compressor and a medium-pressure compressor.

Examples of the system and method can include every combination and permutation of the various system components and the various method processes, wherein one or more instances of the method and/or processes described herein can be performed asynchronously (e.g., sequentially), concurrently (e.g., in parallel), or in any other suitable order by and/or using one or more instances of the systems, elements, and/or entities described herein.

As a person skilled in the art will recognize from the previous detailed description and from the figures and claims, modifications and changes can be made to the examples of the invention disclosed herein without departing from the scope of this invention defined in the following claims.