Aircraft propulsion system and method

Abstract

The invention relates to a propulsion system for providing controllable propulsion, the propulsion system comprising: a fuel cell arrangement (210) for generating electrical energy; a gas generator (250) comprising a compressor (256), a combustor (254) and a turbine (252) wherein the output from the turbine is arranged to provide propulsion by rotational motion; a hydrogen source (212) for providing hydrogen to the fuel cell arrangement and the gas generator; an oxygen source (214) for providing oxygen to the gas generator (250) wherein, in use, the gas generator is selectively for providing electrical energy for additional propulsion.

Description

Technical Field

[0001] The present invention relates to aircraft propulsion systems and power systems. In particular, it relates to aircraft propulsion arrangements capable of providing controllable, variable power levels and therefore thrust at different pressure levels. Different levels of thrust may be delivered to an aircraft based on a particular flight phase, as the flight phase relates to the pressure experienced by the thrust generating portion of the aircraft. Pressure differences may lead to complications in power or thrust delivery within the aircraft. Background Art

[0002] An aircraft gas turbine system typically provides power in the region of 50% of its ground static propulsive power (the power required to provide thrust) at top of climb conditions, but provides approximately 100% power during takeoff. Thus, there is a difference between the power delivered by the aircraft propulsion system during different flight phases of the aircraft.

[0003] Typically, gas turbines work well in this regard because the thrust falloff of the gas turbine engine and therefore the thrust to power ratio at takeoff and top of climb are generally well suited to the inherent characteristics of gas turbines. In addition, the high specific power provided by larger and fewer gas turbines makes other propulsion architectures unable to compete with them for economic reasons. Therefore, modern systems favor gas turbines for aircraft propulsion arrangements.

[0004] Disadvantages of gas turbine engines include environmental demands, however, to date there has been no serious alternative to gas turbine engines that can provide variable thrust in the same manner with similar economic considerations. Gas turbines are therefore the preferred and practical choice for aircraft.

[0005] Although hydrogen fuel and hydrogen synthetic fuels (synfuels) are occasionally used in aircraft, this is not often the case in larger aircraft and not at all in passenger aircraft. This is due to the specific power provided by a gas turbine compared to that provided by a hydrogen system. For a typical system, a gas turbine can achieve approximately 5 to 8 kW / kg, while a hydrogen fuel cell system can achieve approximately 1 kW / kg. Therefore, hydrogen is a reasonable and environmentally conscious choice for smaller aircraft, but is completely blocked from commercial use in larger systems.

[0006] Fuel cells using hydrogen, such as polymer exchange membranes (PEMs), are being investigated, and recent work has shown that specific power values ​​for such systems could optimistically reach 2 kW / kg in the next 5 to 10 years. Some other work has noted that an absolute maximum of about 1.8 kW / kg may exist. It seems likely, therefore, that these systems will not be usable in commercial airliners without significant economic disadvantages.

[0007] The fuel cell can be operated with an over-rated power function to provide about 25% greater output for a small amount of time. This number is higher at the beginning of the life of the fuel cell, but deteriorates towards the end of life. Due to the mechanism of over-rated power, if the over-rated power is used for a long time, damage may occur to the fuel cell, and will cause degradation in the life of the fuel cell in any case. However, even with this method, it is clear that the significant difference between take-off thrust and thrust at the top of the climb cannot be made up in a fuel cell propulsion system.

[0008] Therefore, compared with cruising, the aircraft usually needs about twice the power during takeoff and climb. Compared with the flight time of more than 1 hour (and at most more than 12 hours), the takeoff and climb phase can last about 5-20 minutes. The total duration of the maximum power in flight is about 5 to 30 minutes. For peak power, the duration of the transition from takeoff to cruising altitude is about <300 seconds (s). The remaining peak power is a risk contingency reserve for a missed approach (during the pre-landing stage) and a transfer to another airport. The current state of the prior art arrangement structure contains this remaining peak power for about three missed approaches and one transfer to another airport.

[0009] In order to conserve hydrogen fuel, typically fuel cell systems are designed to consume hydrogen and cause up to 50% of the air (and therefore oxygen) to be wasted. While this may have the advantage of low mass heat dissipation due to the reaction into air, it requires greater compression power (almost doubled) and thus increases parasitic losses, with compression accounting for between 15%-45% of the fuel cell power and being the most significant parasitic power loss. Considerations regarding the cathode size of the fuel cell stack take into account the required oxygen reaction rate, with O2 accounting for approximately 20% of atmospheric air.

[0010] Oxygen can be used in fuel cells, however, oxygen is 8 times the mass of hydrogen and requires a 4:1 ratio (for H2O). Therefore, carrying oxygen on an aircraft is not considered efficient for flight.

[0011] Two-stage compression has been used to achieve the high pressure ratios required to operate fuel cells at high altitudes, however, when operating the fuel cell at low and high altitudes, where low and high pressure ratios are required, respectively, operating in a fixed configuration may not be efficient. Therefore, there are considerations regarding the use of fuel cells over a range of altitude conditions and delivering the necessary airflow to achieve appropriate power for different phases of flight.

[0012] There are therefore developments that could be made in the art, and advantages that could be obtained from such developments. However, the inventors of the invention described herein have created an alternative propulsion arrangement having a wide range of previously unrealizable advantages as described herein. Summary of the invention

[0013] Various aspects of the invention are set out in the accompanying claims.

[0014] From a first aspect, there is provided a propulsion system for providing controllable propulsion, the propulsion system comprising: a fuel cell arrangement for generating electrical energy; a gas generator comprising a compressor, a burner and a turbine, wherein the output from the turbine is arranged to provide propulsion by rotational motion; a hydrogen source for providing hydrogen to the fuel cell arrangement and the gas generator; an oxygen source for providing oxygen to the gas generator, wherein, in use, the gas generator is selectively used to provide electrical energy for additional propulsion.

[0015] This arrangement provides a reliable propulsion system that can selectively provide thrust enhancement when needed. The arrangement can be optimized for enhancement under specific conditions so that efficient thrust can be provided to the propulsion system when needed. This arrangement can be used as an efficient range extender with reduced environmental impact.

[0016] In one example, a propulsion system is provided, wherein the oxygen source is further arranged to provide oxygen to the fuel cell arrangement.Using the oxygen source increases the electrical efficiency of the fuel cell, thereby increasing the overall electrical output of the arrangement.

[0017] In one example, a propulsion system is provided, further comprising: a motor / generator connected to the gas generator; a rectifier electrically connected to the motor / generator; a propeller for providing propulsion by rotational motion; an inverter electrically connected to the rectifier and the propeller; and an electrical bus electrically connecting the rectifier and the inverter, the motor / generator, the rectifier, the propeller, the inverter and the electrical bus being arranged such that the electrical output of the motor / generator connected to the gas generator is converted by the rectifier, then converted by the inverter, and then provided to the propeller.

[0018] This arrangement provides further electrical efficiency benefits through efficient power transfer within the arrangement.

[0019] In one example, a propulsion system is provided, the propulsion system also including a converter electrically connected to the electrical bus and the fuel cell arrangement, the converter being arranged to convert an electrical output of the fuel cell arrangement, which is then received by the inverter.

[0020] This arrangement provides dual power outputs which in turn enables resilience in the system and indirectly helps provide controllable dual or single source applications for thrust. The arrangement provides the user with greater control in the selective operation of the thrust generating components of the arrangement.

[0021] In one example, a propulsion system is provided, the propulsion system also including an electrical energy storage device electrically connected to the fuel cell arrangement and the gas generator, the electrical energy storage device being arranged to store electrical energy output by the gas generator and the fuel cell arrangement.

[0022] This arrangement provides the ability to reserve some electrical power when desired, providing the user with a greater level of control over the system. The user can optimize the use of the stored electrical energy, such as during periods of time when additional thrust (or range) from the propulsion system is needed.

[0023] In one example, a propulsion system is provided, which also includes: a water arrangement structure, the water arrangement structure is used to provide fluid communication of water between a water storage and the fuel cell arrangement structure and the gas generator; and an air arrangement structure, the air arrangement structure is used to provide fluid communication of air between an air inlet and the fuel cell arrangement structure and the gas generator.

[0024] This arrangement provides reliable delivery of air for fuel and water for cooling.

[0025] In one example, a propulsion system according to any one of claims 1 to 6 is provided, wherein the hydrogen source and the oxygen source are in a closed loop system within the propulsion system.

[0026] This arrangement provides further electrical efficiency and overcomes the problems associated with local pressure drops experienced when using an ambient air source.

[0027] In one example, an aircraft is provided that includes the above-described propulsion system.

[0028] In one example, an electric power range extender for providing electrical energy is provided, comprising: a gas generator; a hydrogen source for providing hydrogen to the gas generator; and an oxygen source for providing oxygen to the gas generator, the gas generator being arranged to selectively use hydrogen from the hydrogen source and oxygen from the oxygen source to generate electrical energy during use.

[0029] This arrangement provides an effective, efficient range extender that also avoids the use of fuels that contribute to undesirable greenhouse gas emissions. Specifically, the present invention provides a solution for utilizing renewable and clean fuels while significantly increasing the range of such electrically driven vehicles. This arrangement makes long-term commercial use of clean transportation more feasible, particularly in aerospace. In addition, since the electricity is converted prior to transmission, this arrangement provides for more efficient transmission of electricity.

[0030] In one example, an electric power range extender is provided, the electric power range extender further comprising an electric energy storage device electrically connected to the gas generator, the electric energy storage device being arranged to store electric energy output by the gas generator.

[0031] This arrangement provides the ability to reserve some electrical power when desired, providing the user with a greater level of control over the system. The user can optimize the use of the stored electrical energy, such as during periods of time when additional thrust (or range) from the propulsion system is needed.

[0032] In one example, an electric power range extender is provided, wherein the hydrogen source and the oxygen source are in a closed loop system within the electric power range extender.

[0033] This arrangement provides further electrical efficiency and overcomes the problems associated with local pressure drops experienced when using an ambient air source.

[0034] In one example, an electric power range extender is provided that is also configured to be connected to an aircraft propulsion system.

[0035] This arrangement provides a "plug and play" solution for improving the range of an aircraft propulsion system, particularly an aircraft propulsion system in which electrical energy generation is already performed using a refrigerant.

[0036] In one example, an aircraft including an electric power range extender is provided. Such an arrangement provides a "plug and play" solution for improving the range of an aircraft, particularly an aircraft propulsion system where electrical energy generation is already performed using a refrigerant.

[0037] From another aspect, a method for generating propulsion is provided, comprising: providing hydrogen from a hydrogen source to a fuel cell arrangement to generate electrical output; providing the electrical output of the fuel cell arrangement to a propeller to generate propulsion; selectively providing hydrogen from the hydrogen source and oxygen from an oxygen source to a gas generator to selectively generate electrical output; and selectively providing the electrical output of the gas generator to a propeller to generate propulsion.

[0038] This arrangement provides a reliable method of propulsion generation that can selectively provide thrust enhancement when needed. The method can be optimized for enhancement under specific conditions so that efficient thrust can be provided when needed. This method can be used as an efficient range extender with reduced environmental impact.

[0039] In one example, a method of generating propulsion is provided, the method further comprising selectively providing hydrogen from a hydrogen source and oxygen from an oxygen source to a gas generator based on predetermined travel conditions requiring propulsion.

[0040] This arrangement provides thrust augmentation when needed, particularly at predetermined and calculated demand points. Thus, thrust provision can be optimized for that specific demand point and thus provide extremely efficient augmentation according to predetermined travel conditions. This approach can take into account travel speed, atmospheric conditions, etc. and provide optimized thrust output.

[0041] In one example, a method of generating propulsion is provided wherein the predetermined travel condition requiring propulsion is a takeoff and climb portion of a flight of an aircraft.

[0042] This arrangement provides thrust enhancement under specific travel conditions. Thus, the enhancement can be tailored to provide very efficient thrust at the point of demand, particularly at the points where thrust is most needed, such as takeoff and climb.

[0043] In one example, a method for generating propulsion is provided, the method further comprising: selectively providing hydrogen from the hydrogen source and oxygen from the oxygen source to the gas generator to selectively generate electrical energy output based on predetermined travel conditions that do not require propulsion; wherein the electrical energy output of the gas generator is provided to an electrical energy storage device for storage.

[0044] This arrangement provides a situation where electrical energy is not needed to provide thrust, but energy can be provided and stored until it is needed. For example, under low thrust requirement conditions, such as in horizontal travel (e.g., flight), energy can be provided to the battery for use in a later process. Such a process could be additional thrust provision or refrigeration on a vehicle (e.g., an aircraft), etc.

[0045] In one example, use of any of the above methods in an aircraft is provided.

[0046] These methods are particularly advantageous for use in aircraft, where thrust requirements may vary significantly during different phases of flight. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] One or more embodiments of the present invention will now be described, by way of example only, with reference to the following drawings, in which:

[0048] Figure 1 shows a schematic diagram of a fuel cell propulsion system including a cell stack and a turbo compressor; and

[0049] Figure 2 A schematic diagram of a fuel cell propulsion system having a hydrogen-fed fuel cell and an oxygen- and hydrogen-fed gas generator according to an example of the present invention is shown;

[0050] Figure 3 A schematic diagram showing a fuel cell propulsion system having an oxygen and hydrogen supply fuel cell and an oxygen and hydrogen supply gas generator according to an example of the present invention; and

[0051] Figure 4 A schematic diagram of a battery electric range extender with hydrogen and oxygen feeding a gas generator is shown.

[0052] Any reference to prior art documents in this specification should not be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the art. As used in this specification, the words "comprise", "comprising" and similar words should not be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean "including but not limited to". The present invention is further described with reference to the following examples. It should be understood that the claimed invention is not intended to be limited by these embodiments in any way. It will also be appreciated that the present invention covers not only individual embodiments but also combinations of the embodiments described herein.

[0053] The various embodiments described herein are presented only to help understand and teach the claimed features. These embodiments are provided only as representative samples of embodiments and are not exhaustive and / or exclusive. It should be understood that the advantages, embodiments, examples, functions, features, structures and / or other aspects described herein should not be considered as limitations on the scope of the invention defined by the claims or limitations on the equivalents of the claims, and other embodiments may be utilized and may be modified without departing from the spirit and scope of the claimed invention. In addition to those specifically described herein, various embodiments of the present invention may appropriately include appropriate combinations of disclosed elements, components, features, parts, steps, devices, etc., and may be composed of or substantially composed of appropriate combinations of disclosed elements, components, features, parts, steps, devices, etc. In addition, the present disclosure may include other inventions that are not currently claimed but may be claimed in the future. DETAILED DESCRIPTION

[0054] The invention described herein relates to generating propulsion for an aircraft and power systems. A particular engine system for an aircraft may involve a fuel cell, at least one compressor and at least one turbine. The generation of propulsion depends on factors that may be affected by altitude. Therefore, the aircraft propulsion system herein is arranged to take into account different power requirements during different flight phases due to different pressures at different altitudes. Additional power may be provided during takeoff / climb and then not provided during cruise. Therefore, additional power for takeoff and climb is required at a higher pressure when on the ground and at a lower pressure near the top of the climb phase.

[0055] The invention described herein relates to a battery electric range extender, also referred to as an electric power range extender, for efficient range extension and with low environmental impact.

[0056] The present invention provides a variety of creative strategies that can more efficiently use compressed and compressed fuel in a fuel cell propulsion system. The fuel cell operates by providing a portion of hydrogen and a portion of oxygen (for example from air) as reactants and oxidants, respectively. The fuel cell uses these to provide electrical energy. In this article, these are generally referred to as "fuels" provided to the fuel cell, that is, hydrogen and oxygen are referred to as "fuels". The term "fuel" used in the first sense is a reactant and in the second sense is an oxidant. The term is often used in a broad sense to refer to substances that are changed in some way in a process that can produce usable energy, such as hydrogen and oxygen being converted into water when releasing electrical energy.

[0057] Oxygen sources that can provide oxygen for use in fuel cell propulsion systems (e.g., aircraft arrangements) include an environmental control system (ECS), oxygen (O2) obtained by enriching ambient air or using a dedicated (or other) oxygen source. The oxygen source can be a liquid oxygen source (LOx). Advantageously, liquid oxygen has a lower spatial density than oxygen in the gas phase, so there are capacity advantages associated with the use of LOx in any system described herein. Specifically, the volume density of LOx is greater than oxygen in gaseous form.

[0058] Aircraft often carry oxygen on board, and this is a byproduct of the electrolysis process that produces hydrogen (H2) from water. Many current aircraft carry oxygen on board in bottles that can be used in the event of cabin decompression, where for example a blow out of a window etc. may occur. The amount stored is suitable to cover the period until a descent to a safe altitude can be achieved. While passengers use pull-down oxygen masks, crew members can for example use portable oxygen bottles. Therefore, current aircraft often have an oxygen generator or more usually an onboard gaseous oxygen tank.

[0059] Additional power may be provided from a fuel cell arrangement by using a compressed fuel provided to the fuel cell. In particular, the compressed fuel is in the form of compressed oxygen and hydrogen which is then provided to the fuel cell, fuel cell stack or fuel cell array.

[0060] Additional power can be provided from a fuel cell arrangement by using a control scheme in which oxygen (O2) is utilized and H2 is consumed during the process (which can be recycled back into the system and thus reused). The advantages that can be obtained from such an arrangement are related to the following benefits: Lower H2 mass, which is 1 / 8 the mass of O2, and a factor of 1 / 4 in the reaction to H2O. The volume and mass of H2 are such that the small increase in mass and volume will be relatively small in the design. Recirculation of H2 is also easier to achieve and beneficial because there is no need to handle oxygen-depleted air. Another advantage is that if air is released from the aircraft (spilled overboard), energy is not wasted on compression.

[0061] Reference now Figure 1 , a propulsion system 100 is shown that includes a fuel cell stack 110. The fuel cell stack 110 is connected to an H2 source 112 via an H2 source line. The hydrogen portion of the propulsion system 100 is labeled by portion 102.

[0062] Although a hydrogen source will be used throughout the examples shown herein, alternative suitable fuels such as reformed hydrocarbons can be used with the proposed propulsion system. The hydrogen source can include 99.99% hydrogen (about 100%, etc.) or a lower percentage, which will provide a workable fuel in the supply. This can include commercially pure hydrogen, typically about 99.99%. Alternatively, some fuels can be used with impurities at a level of about 0.4%, thus providing 99.6% hydrogen. Additionally or alternatively, the supply can provide a higher percentage of methane while converting methane to hydrogen or using a methane fuel cell at the same time.

[0063] The propulsion system 100 has a compressor 120, a motor / generator 122, and a turbine 124. The compressor 120 is connected to a heat exchanger 126, and the turbine 124 is connected to another heat exchanger / condenser 128. The compressor 120 is connected to an ECS exhaust source 130. The compressor 120 can be a single-stage centrifugal type turbo compressor, and needs to provide a full range of pressure ratios from about 3 to about 9 for all operating conditions. The system can be an electric drive compressor 120, and can use the turbine 124 to collect energy from the cathode (hot air exhaust) 132.

[0064] The ECS exhaust source 130 may be enriched by an oxygen concentrator. This enrichment may occur before or after the oxygen reaches the air source 130 in the process. The turbine 124 is connected to the cathode exhaust port 132. This air / exhaust portion is labeled by portion 104. Element 130 is referred to as an ECS exhaust source, but may also be an external (ambient) air source, etc. The primary function of element 130 is to provide air (whether enriched with oxygen in some way) for use in the fuel cell stack 110 via the single compressor 120 of the system 100.

[0065] The two heat exchangers 126, 128 are connected to the fuel cell stack 110. The heat exchanger 126 is connected to the compressor 120 and the fuel cell stack 110, and cools the air exiting from the compressor 120. The heat exchanger 120 may be optional, depending on both the temperature limit of the fuel cell stack 110 and the temperature of the air after being compressed by the compressor 120. The fuel cell stack 110 is connected to the water tank 140 via a water pump 142 and a heat exchanger 144. The water tank 140 is connected to the heat exchanger / condenser 128. The water portion is marked by portion 106.

[0066] The examples shown herein are examples of water-cooled fuel cell stack systems. The examples shown have been simplified to emphasize the most creative elements of the present system. However, these are merely examples. Such examples may omit in-depth details about less common elements in the system, such as an optional recirculation system that may be used to recirculate hydrogen. Other omissions include a humidifier that may be used for the cathode air source. Therefore, although not explicitly shown, these features may be included in the present arrangement. In addition, the present arrangement may be used with an evaporatively cooled fuel cell stack.

[0067] In fact, the condensing heat exchanger 128 may be optional for high power stages where no condensed water is extracted. Instead, the humid air may be sent outside ("overflow") or stored in an intermediate container until it can be sent outside. In this way, the pressure losses inherent in the use of the condensing heat exchanger 128 will not be included in the present arrangement, which results in a higher performance system (in the form of more power). To compensate for this overflow of humid air, a slightly larger water tank will be required.

[0068] exist Figure 1 In the arrangement shown, the propulsion system 100 uses ECS air with an oxygen concentrator. There are many advantages that derive from this arrangement.

[0069] An oxygen concentrator (oxygen separator) can be used to produce a higher percentage of O2 in the air in section 104 than in the cabin or in the outside ambient air. Using a higher percentage of O2 for a period of time will enable the fuel cell to operate at a net higher power level during that period of time. In contrast, a system without an oxygen concentrator uses the oxygen contained in the ambient air. The result is that many current fuel cell systems waste air and consume H2 to their maximum extent. This is necessary for ambient air because approximately 21% of O2 (as in air) will become depleted and could potentially starve the fuel cell. This is not the case with oxygen systems. O2 in the reactant ratio is 4 times heavier than H2, and it is therefore more reasonable that if waste occurs, H2 will be wasted. This is further justified because significantly more H2 is stored compared to O2, and therefore, the mass change at the system level (specifically, the tank mass) is lower. In addition and beneficially, in the case of high power for cryogenic cooling systems, this arrangement allows more available heat dissipation in liquid hydrogen.

[0070] The source air requires less compression than the outside ambient air (which can be low at high altitudes). Our estimates suggest that the required compression for ambient air is about 3 times rather than 9 times. This is because the source air may come from already pressurized cabin air, and because this air may be enriched with oxygen. The enrichment of oxygen results in less air being required, and therefore less compression being required.

[0071] Additional advantages may be obtained from the lower temperature air in the air source when compared to compressed ambient air. In an arrangement omitting the heat exchanger 126, there is no pressure loss associated with including the heat exchanger 126. Thus, the lower air temperature on the cathode side means that the fuel cell stack 110 can dissipate more heat into the air before reaching an equal fuel cell stack temperature (an arrangement that includes the heat exchanger 126). In this way, omitting the heat exchanger 126 may be beneficial in enabling the fuel cell stack 110 to operate at a higher power.

[0072] An oxygen concentrator may be used to increase the O2 ratio within the air supplied in portion 104, or the oxygen concentrator may be used to supply pure oxygen to the system 100. As previously described, using a higher ratio of O2 in the air source 130 to the fuel cell stack 110 enables greater power output from the fuel cell stack 110 because less non-reactive air (nitrogen, etc.) passes through the fuel cell stack 110. Alternatively, a smaller fuel cell stack may be provided that provides the same output power (due to the greater power output per size of the fuel cell stack 110 arrangement of the present invention).

[0073] In the case of using liquid oxygen from an oxygen source (such as a tank or the like), the specific heat of vaporization and the specific heat capacity of oxygen can be used to cool the elements of the propulsion system 100. Cooling the electrical elements results in efficiency benefits because there are no, for example, eddy currents, etc. In addition, the use of pure oxygen in the system 100 can enable the use of a smaller fuel cell area and therefore a smaller and lighter fuel cell stack 110. This results in efficiency benefits because the mass of the fuel cell stack needs to be carried, for example, by the aircraft in use. The lower the mass of the stack, the less fuel is needed to carry that mass compared to a heavier system.

[0074] Liquid oxygen allows the inlet temperature of the oxidant to be even lower, which in turn enables the fuel cell stack 110 to operate with potentially higher heat dissipation and therefore higher power. Additional potential advantages include that because the only gas content is oxygen, this oxygen can be completely consumed. With air systems, typically only 50% of the oxygen can be consumed because the system must ensure that the fuel cell stack has enough O2, so an over-supply of O2 is preferred. The current system 100 has benefits in ensuring less oxygen is wasted and reducing pressure losses (including back pressure) at the outlet of the fuel cell stack 110. This will most likely result in IP in how we get water to the stack while trying to keep O2 in.

[0075] exist Figure 1 In the example shown, the fuel cell stack 110 is required to operate well in both of the above conditions, so the more primary advantage relates to increased fuel cell stack power (before considering parasitic losses, i.e., turbine compressor, pumps, etc.) and net power, rather than the slightly secondary advantage of adjusting the size of the fuel cell stack 110.

[0076] By reusing ECS ​​air via source 130, system 100 does not require an external air intake to bring in air from the surrounding environment. Therefore, there is an aerodynamic drag benefit associated with omitting an external air intake element. This drag benefit translates into a benefit associated with the energy requirements of system 100 as a whole; it will be appreciated that system 100 will need to provide more thrust to accommodate an element that may provide additional drag. By eliminating the need for this element, system 100 is more efficient.

[0077] As mentioned, the system has a fixed configuration that may not be efficient for providing power over a wide range of altitudes, and therefore pressures.

[0078] Reference now Figure 2 , a fuel cell propulsion system 200 is shown having a hydrogen-fed fuel cell and an oxygen and hydrogen-fed gas generator 200. Reference numerals for similar components of the propulsion system 200 will be Figure 1The reference numerals used in the drawings are the same, but the numerals are increased by 100. For the sake of convenience, a complete description of similar components may not be provided.

[0079] The propulsion system 200 includes Figure 1 The arrangement structure shown is a fuel cell stack 210, an H2 source 212, a compressor 220, a motor / generator 222, a turbine 224, a heat exchanger 226, a heat exchanger / condenser 228, an air source 230, a cathode exhaust port 232, a water tank 240, a water pump 242 and a heat exchanger 244.

[0080] The propulsion system 200 has sections indicating which elements are supplied by which sources. In particular, the system 200 has a hydrogen section 202, an air section 204, a water section 206, and an oxygen section 208. The water section and the air section supply water and air, respectively, to the Figure 1 The elements previously shown in Figure 2 The gas generator 250 includes a turbine 252 , a combustor 254 , and a compressor 256 .

[0081] Gas generator 250 may also be referred to as a gas turbine. Gas generator 250 generates rotational power and uses a propulsion motor for converting electricity into motion. The arrangement is combined with a fuel cell for converting hydrogen into electrical energy. Burner 254 reacts fuel and oxygen, and the turbine converts electrical energy into kinetic energy. In some arrangements, compressor 256 may be optional. Fuel and oxygen may alternatively (or additionally) be provided from a compression tank or source, thereby eliminating any need for compressor 256.

[0082] The hydrogen source 212 supplies hydrogen to the gas generator 250 , and the oxygen source 214 supplies oxygen to the gas generator 250 .

[0083] In addition to Figure 1 In addition to the arrangement shown, Figure 2 The system 200 has an electrical portion 209 that includes a gas generator 250 , a motor / generator 260 , a rectifier 262 , an electrical storage device 264 , a converter 266 , an inverter 268 , and a fan / propeller and a motor / generator 270 .

[0084] The gas generator 250 of the electrical section 209 is connected to the air section 204, wherein air is transferred from the turbine 224 to the turbine 252 of the gas generator 250. The gas generator 250 of the electrical section 209 is also connected to the water section 206, wherein water is transferred from the heat exchanger / condenser 228 and the water tank 240 to the turbine 252. As described above, the gas generator 250 also receives hydrogen and oxygen from the hydrogen source 212 and the oxygen source 214, respectively.

[0085] Gas generator 250 is connected to motor / generator 260 via shaft 258. Motor generator 260 is electrically connected to rectifier 262. Rectifier 262 converts from AC current to DC current. Thus, rectifier 262 is a type of converter. By converting to DC, power distribution efficiency is gained.

[0086] The rectifier 262 is electrically connected to a DC electrical bus 263. The DC output of the rectifier 262 is thus carried by the DC electrical bus 263 to other components in the electrical portion 209. The electrical bus 263 connects the rectifier 262 to an electrical storage device 264. The electrical storage device 264 provides the function of retaining some electrical energy for later use. The electrical storage device 264 may be referred to as an electrical energy storage device. Thus, this may provide the user with control over the timing of the use of electrical energy, so that energy is used only when needed (such as during a particular moment of flight). Such a storage device may be in the form of a battery or the like.

[0087] The electrical bus 263 also connects the rectifier and the converter 266 connected to the fuel cell stack 210. Thus, the motor generator 260 and the fuel cell stack 210 output electrical energy that is distributed as DC through the electrical bus 263. This electrical energy can be stored in the electrical storage device 264 or provided to the inverter 268, which is connected to the fan / propeller and the motor / generator 270. The inverter 268 converts the electrical energy from direct current (DC) to alternating current (AC). This conversion occurs before the electrical energy is delivered to the fan / propeller and the motor / generator 270. Thus, the electrical energy is provided to the propulsion motor to generate thrust through the propulsion system 200.

[0088] There are a number of advantages associated with the arrangement shown in system 200, some of which will now be discussed.

[0089] Depending on the O2 inlet pressure from the oxygen source 214, relatively little compression is required, or even no compression in some arrangements. For the same available shaft power, since the compression ratio required for the use of pure O2 (100% O2) is significantly lower than the compression ratio required for the use of atmospheric air (about 22% O2) for the same amount of oxidant, a higher power density can be provided to all other components within the arrangement, including the combustor and turbine in the gas generator 250. Therefore, a greater electrical output can be provided.

[0090] By delivering hydrogen and oxygen from hydrogen source 212 and oxygen source 214, respectively, and delivering air and water from air inlet 230 and water tank 240, system 200 is effectively a closed loop machine. The inputs come from controlled sources at controlled temperature, pressure, and flow. Therefore, this is an efficient use of the resources provided. Although not shown, the gas generator 250 can be connected to receive waste exhaust H2 and / or O2 from the fuel cell stack 210. This further improves the use of the resources provided.

[0091] The closed loop nature of the arrangement 200 also has the benefit that there are no limitations on the start / re-ignition envelope when compared to conventional propulsion and APU gas turbines. This aspect is an improvement over systems where the APU utilizes air from the surrounding environment. When the aircraft is at high altitudes, the ambient air experiences a pressure drop, which can negatively affect the power system. In contrast, by storing hydrogen and oxygen on board the aircraft, the effects of low pressure are eliminated, thereby providing the above benefits.

[0092] The gas turbine 252 may be designed to be utilized as follows, i.e., transitioning from maximum static power to high speed cruise with similar compressor inlet 256 conditions and largely controllable turbine 252 outlet conditions. Thus, the design range of the system 200 is lower, thereby achieving higher utilization performance. The gas generator 250 may be arranged to provide greater specific performance for a given range (e.g., a given Mach power and a given altitude). The generator 250 may be arranged to provide specific power enhancement under certain conditions, thereby providing very high performance during those conditions, but not operating under other conditions and thus reserving performance for those conditions.

[0093] The sources of air, hydrogen, oxygen and water may be reservoirs, tanks or containers etc. There is no need for an inlet to be present on an aerodynamic surface of an aircraft etc. Therefore, there is no intake resistance and no inlet energy losses. This results in improved efficiency (with reference to consumed fuel) and a lower installed noise footprint. Thus, the arrangement 200 provides electrical and environmental advantages. The fact that there is no inlet duct reduces the propagation of aerodynamic noise from this source, thereby reducing the forward noise profile of the system 200 when integrated into an aircraft.

[0094] Further environmental benefits are provided by using pure oxygen from oxygen source 214, i.e., no nitrogen or other atmospheric gases. The only combustion product from system 200 will be water, with some products of incomplete combustion. Thus, system 200 is a true zero-emission power system.

[0095] The hydrogen source 212 and the oxygen source 214 contain liquid hydrogen and oxygen, respectively. These refrigerants can be used to cryogenically cool the generator and converter elements in the system 200 to a superconducting state. This cooling may occur during peak conditions because the latent heat of vaporization of LH2 alone may not be sufficient. This cooling can be used to cool turbines or other heat sources on an aircraft in which the system 200 is arranged. If necessary, it can also or alternatively be used to force condensation of exhaust effluent. This can prevent exhaust gas release, which in turn has further environmental benefits.

[0096] In more detail, Figure 2 In "normal" operation, only liquid hydrogen may be used for cooling without liquid oxygen. The generator and converter (and / or similar components) may be cooled by liquid hydrogen. When the arrangement is used in an enhanced arrangement to produce peak power and high levels of thermal energy, more intense cooling may be required. In this case, liquid oxygen may be used as the coolant for the generator and converter (and / or similar components).

[0097] Another advantage of the power generation system 200 is that the heat generated from the propulsion system is dissipated into the exhaust gas flow, thereby reducing the need for heat exchangers that operate less efficiently at low speeds. This again increases the overall electrical efficiency of the system 200.

[0098] The utilization of the gas turbine can be used for a specific period of time per flight. In one example, in each flight, the gas turbine 250 can be used for up to 500s, and possibly up to 30,000 flight cycles, which means an operational life of approximately 4,200 flight hours. In other examples, the system can be used for up to 3,000 flight hours. Therefore, mechanical and chemical fatigue will be a smaller challenge than for hydrogen turbines used for main propulsion. Therefore, there are available benefits in terms of the toughness of this system relative to currently known systems. This results in a longer life and greater resilience to degradation while in use.

[0099] The system 200 can be integrated with a fuel cell turbo compressor, including with the turbine of the turbo compressor, thereby enabling significant performance improvements. This can be used with decoupling techniques for efficient power generation and power management during flight.

[0100] Thus, the system 200 provides a number of interrelated advantages through the interaction of features within the system 200. Many of these relate to electrical efficiency, which in turn relates to the resulting propulsive and environmental efficiencies.

[0101] The system 200 may directly drive a fan / propeller or a generator, as shown by element 270. The system 200 may be used as a power generation unit and integrated into a multi-fuel or hydrogen fuel system with main propulsion from an internal combustion engine. Figure 2The option shown in the arrangement utilizes a fuel cell stack 210 , however this is not a limiting arrangement as explained.

[0102] By integrating the fuel cell stack 210 into the system 200, there are benefits to using it for cruise power because the fuel cells operate better with a controlled source than with high altitude, lower oxygen concentration air. In addition, the arrangement 200 has environmentally beneficial wake performance compared to other systems. As described above, during periods such as takeoff and climb when additional propulsion is clearly needed, a dedicated oxygen generator can be used to provide this additional propulsion energy. The additional propulsion energy can also be provided by a dedicated oxygen generator during an aborted landing or other flight deviations as needed. In fact, the oxygen generator provides an enhancer system that is highly electrically efficient, highly environmentally friendly, and relatively easy to integrate into current systems. Therefore, the solution provided herein has a wide range of benefits and is effective.

[0103] Although the arrangement 200 has a large number of features that are interrelated to provide the advantages described above, the implementation of the arrangement 200 in a system that requires propulsion, such as an aircraft, can be controlled to achieve additional advantages. For example, a steam turbine can be coupled to a thrust generating exhaust nozzle. Hydrogen and oxygen can be discharged through the nozzle, which provides additional thrust to the propulsion arrangement. This increases the efficiency of the entire arrangement in providing thrust. Combusting hydrogen provides higher exhaust temperatures than those produced by the fuel cell 210. Such higher exhaust temperatures can be used to generate high exhaust velocities. These exhausts can be implemented around the tail of the aircraft to minimize the wake / boundary layer, similar to boundary layer engulfment.

[0104] Figure 2 The arrangement 200 has a fuel cell stack 210. The arrangement 200 also has an oxygen source 214. The arrangement 200 can be used with additional fuel cell stacks. Figure 2There will be weight considerations when providing a second fuel cell stack for the system 200. If the weight of the second fuel cell stack is too large, this will result in an inefficient system 200, because the first fuel cell stack 210 will need to provide more power during transportation to bear the weight of the second fuel cell stack. Therefore, the system 200 can be arranged to carry just enough liquid oxygen for about 6 minutes of additional power (provided by the additional fuel cell stack) during takeoff and climb. This can be provided to the additional fuel cell stack from source 214. In this way, once entering cruise, the first fuel cell stack 210 can carry a minimum amount of additional weight, that is, only the required weight, thereby ensuring that the system 200 is as light as possible. This arrangement, with only the fuel cell stack A210 with the required fuel and the fuel cell stack without any fuel, is still lighter than two conventional fuel cell systems. Therefore, the system 200 can be particularly efficient in this arrangement (with two fuel cell stacks).

[0105] The size of the fuel cell stack can be different. The fuel cell stack can be load balanced to optimally provide power for a particular use of the system 200. For example, if the system 200 is used in an aircraft, an additional higher operating power fuel cell stack (not shown) can be 50-60% smaller than the fuel cell stack A 210. In this way, the system 200 can be arranged to have minimal impact on the space required to accommodate the system 200.

[0106] Thus, the additional fuel cell stack will not require additional auxiliary equipment, or at least only limited additional auxiliary equipment, which in turn increases the specific power output. Since the fuel cell stack 110 is about 50-60% of the mass of the system 100, this may result in an increase in the overall specific power of the system 200 of about >100% (e.g., about 3.1-4.1 kW / kg for a 1.5 kW / kg base system).

[0107] The benefit of having the additional fuel cell stack associated only with an oxygen source (i.e., using pure oxygen or very high oxygen percentage air) enables the auxiliary equipment to be kept to a minimum for the fuel cell stack integration. The additional fuel cell stack will be sufficiently more power dense than the baseline case (e.g., the ratio of cathode volume to oxidant volume can be increased from approximately 20% for air to 100%).

[0108] Although not shown, an arrangement having an additional fuel cell stack operating from an oxygen source is contemplated from the present disclosure.

[0109] Reference now Figure 3 , showing something like Figure 2 The propulsion system 300 of the propulsion system 200 is shown in FIG. 300 . The reference numerals for similar components of the propulsion system 300 will be Figure 2The reference numerals used in the drawings are the same, but the numerals are increased by 100. For the sake of convenience, a complete description of similar components may not be provided.

[0110] exist Figure 3 In the arrangement structure, the oxygen source 314 provides oxygen to the gas generator 350 and the fuel cell stack 310. Figure 2 In the process, the oxygen source is not supplied to the fuel cell stack.

[0111] The oxygen in the oxygen source 314 can be liquid oxygen. Using liquid oxygen has advantages regarding the volume density and energy density of liquid oxygen. An additional benefit of using this arrangement 300 can be that the fuel cell stack 310 can be used as an evaporator to help increase the temperature of the oxygen for input into the fuel cell stack 310. In addition, the oxygen can be used in the coolant (in Figure 3 In the embodiment of the present invention, the coolant is cooled before entering the fuel cell stack 310 from the water arrangement. In this way, the coolant is more efficient in its heat removal function.

[0112] Oxygen is delivered via the oxygen portion 308 of the system 300. The delivery of oxygen to the fuel cell stack 310 enables the fuel cell stack 310 to operate at a lower oxygen percentage than using only fuel cells having a lower oxygen percentage (e.g., Figure 2 The oxygen source 314 thus provides additional oxidant to the fuel cell stack 310 to provide additional power. The oxygen supplied to the fuel cell stack 310 can be supplied at a lower temperature than air. This results in the fuel cell stack 310 requiring less cooling to achieve the same power. This, in turn, results in mass savings because less auxiliary equipment (BoP) is required to achieve the same power as the fuel cell stack 310. Figure 2 Thus, in the arrangement 300, the fuel cell stack 310 provides a power of equal Figure 2 The fuel cell stack 210 in the arrangement structure 200 has a greater power output.

[0113] The system 300 can be used in two modes: in one mode, oxygen is supplied to the fuel cell stack 310; and in another mode, oxygen is not supplied to the fuel cell stack 310. In the first mode, the fuel cell stack 310 operates with oxygen, and the system 300 provides a large amount of power. In the second mode, the fuel cell stack 310 operates without oxygen. The second mode provides a lower amount of power than the first operating mode. In this way, the system 300 provides an arrangement for a fuel cell propulsion system that can controllably provide different levels of power that can be selected by an operator or controller based on environmental conditions. Therefore, the system 300 is well suited for transportation modes that may require additional power during different parts of the journey, such as aircraft, which require additional power during takeoff and do not require this power during cruising. This can be achieved by a simple shut-off valve or similar system to controllably prevent oxygen from flowing from the oxygen source 314 to the fuel cell stack 310.

[0114] exist Figure 3 In the arrangement 300 shown, it is possible to have the turbine 324 not do as much work, which would leave more energy in the exhaust flow. If enough energy is left in the exhaust flow, which can be controlled by a user controlling the behavior of the turbine 324, then this excess energy can drive the turbine 352 and subsequently operate the compressor 356. This is a particularly energy efficient operating arrangement. This operating arrangement utilizes the pressure of the effluent leaving the first turbine 324 and the ambient pressure. Therefore, this operating arrangement is particularly advantageous when the system 300 is at altitude. Figure 3 In the method of operation, turbine 324 is bypassed by the exhaust gas flow so as to leave enough energy in the exhaust gas flow to power turbine 354. Figure 3 In an alternative arrangement (not shown), turbine 324 may be omitted.

[0115] exist Figure 3 In the embodiment of the present invention, the motor / generator 322 can be omitted if the shaft between the turbine 324 and the compressor 320 can still be operated. There will be associated weight benefits in omitting the motor / generator 322. Although in the embodiment of the present invention, the motor / generator 322 can be omitted. Figure 3 Omitted from Figure 2 a, but in an alternative arrangement, motor / generator 222 may be omitted and motor / generator 252 included.

[0116] Although not explicitly shown, the systems described herein may include regulating elements, such as controllers, that regulate the water, hydrogen, oxygen, and air supplied from the sources to the fuel cell stack and the gas generator. The regulation may be performed based on the power and cooling requirements of the fuel cell stack and the gas generator. The regulation may include feedback sensors or detectors for reading the characteristics of the fuel cell stack and the gas generator.

[0117] In use, hydrogen is provided to the gas generator 350 to provide kinetic energy from chemical energy. To further improve efficiency, unconsumed hydrogen provided to the fuel cell (which in practice may be between 0.1% and 5% of the hydrogen) may be recirculated to the generator 350. This improves the overall efficiency of the propulsion arrangement. The 0.1% to 5% value is derived from the anode stoichiometry of a typical fuel cell, which results in a small amount of hydrogen being purged during fuel cell use. Many systems simply exhaust hydrogen into the exhaust by diluting it with enough air to avoid the formation of hazardous chemicals. The present system, by redirecting the hydrogen into the generator 350, can reduce the risk of such an arrangement and improve the overall propulsion output.

[0118] Alternatively or additionally, hydrogen can be captured and stored prior to use (which can be in the generator 350 or back into the fuel cell). Thus, this arrangement reduces gas emissions to the atmosphere while also improving the output of the arrangement. These advantages arise from recapture of unspent hydrogen, which can also be referred to as purged hydrogen capture.

[0119] Reference now Figure 4 , a battery electric range extender 400 for an aircraft propulsion system is shown. Reference numerals for similar components of the battery electric range extender 400 will be Figure 3 The reference numerals used in the drawings are the same, but the numerals are increased by 100. For the sake of convenience, a complete description of similar components may not be provided.

[0120] The battery electric range extender 400 includes a water line 406 that supplies water from a water source, an air line 404 that supplies air from an air source, a hydrogen source 412, an oxygen source 414, a gas generator 450 connected to a motor / generator 460 via a shaft 458, which is connected to a rectifier 462. The rectifier 462 supplies an electrical bus 463 that is connected to an electrical storage device 464 and an inverter 468 of the previously arranged structure. In this example of the battery electric range extender 400, the gas generator 450 is not mechanically linked to the fan 470. The generator 450 and the fan 470 may be linked by a gearbox (which may be magnetic) or mechanically linked on the same shaft.

[0121] Furthermore, an electrical bus may not need to be used in this arrangement, however modern aircraft use secondary aircraft power loads to provide power to other services on the aircraft or, for example in connection with a hybrid propulsion system, to enable operation of other aircraft components. This may enable one section to operate without another, or vice versa.

[0122] The arrangement 400 may be applied to an aircraft propulsion system to provide an additional power unit for providing propulsion to the aircraft. In effect, this is an addition that can significantly increase the power output, and therefore the range of the aircraft, if desired, at relatively cheap weight and fuel costs. Thus, this provides an effective and efficient way of providing additional thrust to the aircraft.

[0123] Any system that already includes a source of hydrogen and oxygen may employ the battery range extender 400. Thus, it is advantageous that the arrangement 400 is relatively simple to apply to an aircraft's propulsion arrangement to provide additional propulsive output.

[0124] The arrangement described herein may be suitable for short-haul flight operations, such as vertical takeoff and landing by using a pure oxygen and hydrogen gas turbine as a range extender using only batteries or similar storage devices as an electrical solution (also known as an electrical energy storage device solution), or for generating peak power so that the batteries do not need to be at a high C-rate during takeoff (the C-rate is a measure of the rate at which a battery is discharged relative to its maximum capacity).

[0125] Using approximations, it is possible to calculate how to provide energy from these disclosed propulsion arrangements for flight conditions. In one example, for a regional aircraft with an 8 megawatt (MW) takeoff peak power, this can be provided by approximately 3MW of gas generator power and using a 4MW fuel cell stack at 125% of the rating (the fuel cell can be operated at over-rated power for a period of time without significant degradation of the fuel cell). The 4MW fuel cell stack output is the rating required for cruise approximation. Therefore, the arrangement can operate the fuel cell stack for cruise, and additional enhancements for takeoff and climb are provided by the 3MW gas generator, and the fuel cell stack is operated at over-rated power for a limited period of time.

[0126] Continuing with the estimate in this particular example, the amount of hydrogen and oxygen consumed in the gas generator during takeoff and climb will be approximately 13 kg and 52 kg respectively. A further amount of 9 kg and 36 kg is required to be able to abort the landing and deflect (as described above). Therefore, one advantage of this arrangement is that this weight is mainly consumed during takeoff and climb, making the system lighter and therefore requiring less thrust intensity during cruise.

[0127] The same approach can be applied to Brayton or Otto cycle engines as well as hybrid constant volume combustion cycle engines. As a benefit of the integrated motor / generator, it can be used to reduce motor / lock or flex, enable start / restart and support transient performance. After a large amount of heat energy is generated using the arrangement, motor / lock or flex can occur by subsequent cooling of the element (such as the shaft).

[0128] The oxygen may be derived from a gaseous hydrogen system, a liquid oxygen system, or from an oxygen separation system (e.g. a molecular sieve oxygen concentrator (MSOC), or an on-board oxygen generation system (OBOGS) or a cryogenic vortex tube type system). The air used as the source of this oxygen may be the cabin, an environmental control system, or outside atmospheric air. The objective is to provide an air source of increasing oxygen percentage, the advantages of which (as described above) increase as the oxygen percentage increases.

[0129] The sources in the system proposed herein include hydrogen and oxygen. The conditions of these sources are important to control so that hydrogen and oxygen can be delivered reliably during operation of the system. To achieve a suitable inlet pressure for the arrangement, the arrangement may include: a high pressure tank, thereby eliminating the requirement for a pump / compressor; or a low pressure tank with a turbo pump.

[0130] Thus, with the foregoing in mind, a specific example of an embodiment of the arrangement shown herein may include two space rocket turbo pumps (one for the oxygen source and one for the hydrogen source) feeding a combustor that drives a turbine that in turn drives a generator. Alternatively, a combined space rocket turbo pump may be used to provide compression to both sources.

[0131] There are potentially many variations to this system that include driving the generator from the turbopump turbine (thereby reducing the number of components present in the system). Reducing the number of components will increase the life and reliability of the system because there are fewer components that can break (affecting reliability) or require replacement (affecting life).

[0132] The turbopump as described above may be driven electrically or using steam from the system.

[0133] Additional elements that provide additional levels of control to the user may be introduced to the systems described herein without eliminating the advantages associated with the systems. For example, clutches and gearboxes may be used to achieve greater control over the enabling and disabling of various components of the system. The gearbox may enable the user to control each component of the arrangement to operate at an optimal speed.

[0134] For example, when the aircraft is at sea level (or similar) air pressure, the fuel cell is caused to experience a higher pressure level than, for example, during flight. At sea level, the source may not need to be compressed to provide to the fuel cell stack, and it is therefore advantageous to provide the user with the option to deactivate these components, and therefore provide a more efficient system (due to the enablement of removing unnecessary elements in the arrangement). For example, at sea level, we can shut down aspects of the arrangement to increase the effectiveness of the entire arrangement. This decoupling therefore provides additional control and efficiency to the user.

[0135] Therefore, arrangements are provided in which performance control elements such as clutches or gearboxes may be included to provide a user with greater control over components of the arrangement. Performance control elements may be mechanical or electrical elements that may affect the operation of some components within the various arrangements shown in the examples in the drawings herein. Controlling the operation of such components may allow a user to optimize the operation of the arrangement as a whole to provide efficiency benefits (e.g., at low altitudes where fewer components need to be operated) or to provide additional thrust (e.g., at high altitudes where additional components may be enabled). Control of the operation of a component may include controlling whether a component is enabled or not enabled, or the operating conditions of the component (e.g., operating speed, etc.).

[0136] For components (such as Figure 2 and Figure 3 The choice of relative sizes of the two compressors in the arrangement of FIG. 1 and FIG. 2 can enable weight savings to be provided within these arrangements. The consideration is the power output according to the size of the compressors and balancing them accordingly.

[0137] In one arrangement, there may be an air filter between the air intake and the compressor. In an example of use, the air filter may be switched on or off at any available compression. This may advantageously reduce the amount of contaminants that can reach the fuel cell system of the arrangement. However, there will be a pressure loss across the air filter. Therefore, there is a balance between filtering the air to reduce the amount of contaminants that reach the fuel cell system and increasing the pressure loss across the air filter.

[0138] In this arrangement, the user can take advantage of switching the gas flow path at sea level compared to at high altitudes. In particular, because at high altitudes, the air is generally cleaner than at sea level. Therefore, the need for filtering is reduced at high altitudes. In this way, an arrangement with an air filter that can be enabled and disabled by the user provides the user with greater control in achieving filtering, bypassing the air filter when operating at high altitudes. Therefore, there is an efficiency benefit (in that the air flow path with the air filter is not permanently used) while also providing an improved life benefit due to the reduced level of contaminants reaching the fuel cell stack.

[0139] Thus, an effective and fuel efficient propulsion system is described herein. The system provides the multiple advantages described above. Additional advantages include that when using hydrogen and oxygen, the only byproducts are deionized superheated steam and water fluids: no nitrous oxide. The system uses the high power density of gas generators while overcoming the problem of wakes by operating mostly at less than 20-25,000 feet.

[0140] Oxygen is eight times heavier than hydrogen and has four times the mass of hydrogen when reacting with hydrogen to form water, so using oxygen for the entire flight is not feasible, even considering that the mass of hydrogen when combined with oxygen is only 1 / 3 of the mass of kerosene (a maximum of 2 / 3 of the mass of kerosene can be loaded), the total mass of fuel and oxidizer (when not installed) is still about 150% more than kerosene alone. However, with oxygen used to provide peak power, only about 500 seconds is required at most for any aircraft operation. This includes about 300 seconds of takeoff and climb time, about 3 rejected landings, and about one go-around climb in the event of a landing deviation.

[0141] As mentioned above, the use of pure oxygen and hydrogen enables significantly smaller (higher power density) and lighter mass (higher specific power) gas generators. The use of liquid hydrogen and liquid oxygen (ie as a refrigerant) also provides advantages in power density and cooling factors.

[0142] Although the disclosed fuel cell propulsion system is primarily described with respect to aircraft, other vehicles such as spacecraft and submarines may also carry oxygen or liquid oxygen for use in the proposed system (instead of an air intake or ECS source). Although this oxygen or liquid oxygen may be carried primarily for other reasons, the integration of additional oxygen for the fuel cell of the currently disclosed system is not mechanically complex. Alternatively or additionally, these vehicles may advantageously be arranged to provide excess oxygen or liquid oxygen to the fuel cell propulsion system as described herein. Therefore, the disclosed system will advantageously be provided in such a vehicle. Any vehicle that can be propelled by a fuel cell propulsion system such as described herein will benefit from using the system disclosed herein.

[0143] The systems disclosed herein can advantageously provide propulsion in vehicles or systems that can benefit from a system that can provide a controllable, variable amount of propulsion over a wide range of propulsion values, wherein the propulsion is provided by a fuel cell system that can operate in both a normal mode and an over-rated power mode and by additional power provided by a gas generator.

[0144] There are many advantages provided by generating power from a fuel cell rather than via a combustion engine. Producing water rather than generating harmful gaseous emissions (NOx, CO2, etc.) has obvious associated advantages. In addition, the noise level of the operation of the vehicle can be significantly reduced. In a specific example, the noise level during the takeoff and landing phases of an aircraft can be significantly reduced due to the lack of high-speed exhaust gas.

[0145] The vehicle operator can use the additional selectable thrust provided (from the gas generator) whenever needed. This flexibility will enable the pilot to optimize the thrust selection for the phase of flight or sport (such as racing in a straight line). These systems will also not limit the operator to a specific fuel cell stack if, for example, a change in thrust is required at any phase of flight to overcome or adapt to changes in flight conditions.

[0146] Therefore, applications of the system may include automotive, aviation, home or commercial, etc.

[0147] As disclosed herein, another benefit of using fuel cells compared to using combustion engines is the avoidance of the formation of microbial colonies in existing aircraft kerosene fuel tanks. Cleaning of such fuel tanks currently requires detergents and pesticides that are somewhat damaging to the environment. In some cases, such cleaning can be performed after each long-haul flight. Thus, reduced cleaning has further environmental benefits.

[0148] A propulsion system is disclosed herein. The propulsion system has a fuel cell system including features as shown in the previous figures, such as a fuel cell stack. An air source supplies the fuel cell system. A liquid hydrogen source provides liquid hydrogen to the fuel cell system including the fuel cell stack. In an example not shown, the system may also include a helium loop. The helium loop may include a helium source and a conduit for supplying helium. The helium loop may be arranged to provide additional cooling to specific parts of the propulsion system. Such parts may include conductive parts and motor / generators.

[0149] In one example, liquid hydrogen interacts with helium from a helium source. The liquid hydrogen can cool the helium and become gaseous hydrogen. The gaseous hydrogen can then be provided to a fuel cell stack or the like for use in generating electrical energy.

[0150] The fuel cell system provides electrical energy in the form of direct current. The fuel cell system also provides thermal energy in the form of air and water and heat. The electrical energy from the fuel cell system can be provided to the network controller. The current can then be provided to the motor and generator arrangement to provide kinetic energy from the electrical energy to the propeller to provide motion.

[0151] The helium in the helium loop is cooled by liquid hydrogen. The cooled helium can then provide cooling for direct components such as the electrical connections through which the network controller provides electrical energy to the motor and generator arrangement. The cooled helium can also provide cooling for the motor and generator arrangement itself. Helium is advantageous in such a system because it has a lower melting point than hydrogen and can therefore be cooled by the hydrogen without the risk of ice forming in the conduits containing the helium. Other cryogenic coolants can also be used, but helium is particularly advantageous.

Claims

1. A propulsion system for providing controllable propulsion, comprising: A fuel cell arrangement for generating electrical energy; a gas powered generator comprising a compressor, a combustor and a turbine, wherein the output from the turbine is arranged to provide propulsion by rotational motion; a hydrogen source for providing hydrogen to the fuel cell arrangement and the gas generator; an oxygen source, the oxygen source being used to provide oxygen to the gas generator, Therein, in use, the gas generator is selectively used to provide electrical energy for additional propulsion.

2. The propulsion system according to claim 1, wherein: The oxygen source is further arranged to provide oxygen to the fuel cell arrangement.

3. The propulsion system according to claim 1 or 2, further comprising: a motor / generator connected to the gas generator; a rectifier electrically connected to the motor / generator; a propeller for providing propulsion by rotational motion; an inverter electrically connected to the rectifier and the propeller; as well as an electrical bus electrically connecting the rectifier and the inverter, The motor / generator, the rectifier, the propeller, the inverter and the electrical bus are arranged so that the electrical output of the motor / generator connected to the gas generator is converted by the rectifier and then by the inverter before being provided to the propeller.

4. The propulsion system of claim 3, further comprising a converter electrically connected to the electrical bus and the fuel cell arrangement, The converter is arranged to convert an electrical output of the fuel cell arrangement before the electrical output of the fuel cell arrangement is received by the inverter.

5. The propulsion system according to any one of claims 1 to 4, further comprising an electrical energy storage device electrically connected to the fuel cell arrangement and the gas generator, The electrical energy storage device is arranged to store electrical energy output by the gas generator and the fuel cell arrangement.

6. The propulsion system according to any one of claims 1 to 5, further comprising: a water arrangement for providing fluid communication of water between a water reservoir and the fuel cell arrangement and the gas generator; as well as An air arrangement is provided for providing fluid communication of air between an air inlet and the fuel cell arrangement and the gas generator.

7. The propulsion system according to any one of claims 1 to 6, wherein: The hydrogen and oxygen sources are in a closed loop system within the propulsion system.

8. An aircraft comprising a propulsion system according to any one of claims 1 to 7.

9. An electric power range extender for providing electric energy, comprising: Gas generators; a hydrogen source, the hydrogen source being used to provide hydrogen to the gas generator; as well as an oxygen source, the oxygen source being used to provide oxygen to the gas generator, The gas generator is arranged, in use, to selectively use hydrogen from the hydrogen source and oxygen from the oxygen source to generate electrical energy.

10. The electric power range extender according to claim 9, further comprising: a motor / generator connected to the gas generator; a rectifier electrically connected to the motor / generator; an inverter electrically connected to the rectifier; as well as an electrical bus electrically connecting the rectifier and the inverter, The motor / generator, the rectifier, the inverter, and the electrical bus are arranged such that the electrical output of the motor / generator is converted by the rectifier, travels along the electrical bus, and then converted by the inverter.

11. The electric power range extender according to claim 9 or 10, further comprising an electric energy storage device, the electric energy storage device being electrically connected to the gas generator, The electrical energy storage device is arranged to store electrical energy output by the gas generator.

12. The electric power range extender according to any one of claims 9 to 11, wherein: The hydrogen source and oxygen source are in a closed loop system within the electric power range extender.

13. The electric power range extender according to any one of claims 9 to 12, further configured to be connected to an aircraft propulsion system.

14. An aircraft comprising an electric power range extender according to any one of claims 9 to 13.

15. A method of generating propulsion, comprising: providing hydrogen from a hydrogen source to the fuel cell arrangement to generate an electrical energy output; providing the electrical energy output of the fuel cell arrangement to a propeller to generate propulsion; selectively providing hydrogen from a hydrogen source and oxygen from an oxygen source to a gas-fired generator to selectively generate an electrical power output; The electrical power output of the gas generator is selectively provided to a propeller to generate propulsion.

16. The method of generating propulsion according to claim 15, further comprising: Hydrogen from a hydrogen source and oxygen from an oxygen source are selectively provided to the gas generator based on predetermined travel conditions requiring propulsion.

17. The method of generating propulsion according to claim 16, wherein: The predetermined travel conditions requiring propulsion are takeoff and climb portions of the aircraft's flight.

18. The method of generating propulsion according to any one of claims 15 to 17, further comprising: selectively providing hydrogen from the hydrogen source and oxygen from the oxygen source to the gas generator to selectively generate an electrical energy output based on predetermined travel conditions not requiring propulsion; The electric energy output of the gas generator is provided to an electric energy storage device for storage.

19. Use of the method according to any one of claims 15 to 18 in an aircraft.

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