Fuel cell air system

Abstract

According to some aspects of the present disclosure, an air management system for a system, such as an electrical vehicle, utilizes various effects and byproducts of certain air- and water- management processes, including water dosing, air flow, heating and cooling, to perform or enhance other air- and water-management processes, thereby reducing consumption of electrical power, reducing number of components needed for the air management system, or otherwise enhance the performance, efficiency, simplicity and / or life of the overall fuel cell system. In some embodiments, the air management systems for fuel cells utilizes an expander or compressor with a one-way clutch attached, engaged or otherwise linked to certain one or more parts of the expander or compressor and adapted to constrain the motion of the one or more parts. In some embodiments, a one-way clutch is mounted on the shaft of a rotor in a Roots expander or compressor to ensure that the rotor rotates in only one direction.

Description

FUEL CELL AIR SYSTEMCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is being filed as a PCT International application and claims the benefit of and priority to U.S. Provisional Application No. 63 / 520,750, filed on August 21, 2023, and U.S. Provisional Application No. 63 / 600,822, filed on November 20, 2023. The disclosures of U.S. Provisional Application No. 63 / 520,750 and U.S. Provisional Application No. 63 / 600,822 are hereby incorporated herein by reference in their entirety.GOVERNMENT FUNDING

[0002] This invention was made with government support under Contract No. DE- EE0009618 awarded by the National Energy Technology Laboratory funded by the Office of Energy Efficiency & Renewable Energy of the United States Department of Energy. The government has certain rights in the invention.BACKGROUND

[0003] Fuel cells are a viable option as distributed sources of electrical power, such as power sources for electrical vehicles, due to their high efficiency and low emissions. Fuel cells generate electricity from electrochemical reactions without combustion. To optimize the electrochemical reactions, it is desirable to operate fuel cell under certain conditions, e.g., temperature, pressure, gas flowrate, and humidity. Such conditions can be maintained by fuel cell air systems.

[0004] A fuel cell air system can include a compressor for pushing air, and optionally moisture, into the fuel cell stack, where electrical power is generated from the reacting gasses, such as hydrogen and oxygen. Such a system can further include an expander, which is driven by the exhaust gas from the fuel cell to generate mechanical energy, and discharges the exhaust gas at reduced temperature and pressure. The mechanical energy can be used to assist the powering of the compressor, thereby recovering energy that would otherwise be wasted.

[0005] Traditional fuel cell air systems that utilize centrifugal style compressors and expanders can be sensitive to condensation. In order for the centrifugal style system to meet the fuel cell membrane humidity requirements, a humidifier and dryer are used resulting in pressure losses. The resulting pressure loss is undesirable. Further, the addition of the humidifier and dryer result in increased size and weight of a system.

[0006] Certain applications require the fuel cells and associated fuel cell air systems to operatein varying conditions. Efforts are ongoing in designing fuel cell air systems that can increase performance, increase durability, or otherwise increase efficiency of systems employing fuel cells, as well as function properly under varying conditions, as may be the case for electrical vehicles.SUMMARY

[0007] In certain embodiments disclosed herein, the air management systems for fuel cells utilize the heating or cooling effects of the various processes of the air and / or water management to enhance performance, efficiency, simplicity and / or life of the overall fuel cell system. In certain other embodiments, the air management systems for fuel cells utilizes an expander or compressor with a one-way clutch attached, engaged or otherwise linked to certain one or more parts of the expander or compressor and adapted to constrain the motion of the one or more parts. In some embodiments, a one-way clutch is mounted on the shaft of a rotor in a Roots expander to ensure that the rotor rotates in only one direction.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a functional schematic of an air management system, including a differential gear for driving the compressor and expander, or receiving power from the expander, at different rotational speeds, and expander bypass valve, for a system that includes a fuel cell according to some embodiments.

[0009] Figure 2 is a functional schematic of an air management system, including a single drive shaft for driving the compressor and expander, or receiving power from the expander, for a system that includes a fuel cell according to some embodiments.

[0010] Figure 3 is a functional schematic of an air management system, including a differential gear for driving the compressor and expander, or receiving power from the expander, at different rotational speeds, and post-expander throttle valve, for a system that includes a fuel cell according to some embodiments.

[0011] Figure 4 is a functional schematic of an air management system, include a single drive shaft for driving the compressor and expander, or receiving power from the expander, at different rotational speeds, and post-expander throttle valve, according to some embodiments.

[0012] Figure 5 is a functional schematic of an air management system, including a differential gear for driving the compressor and expander, or receiving power from the expander, at different rotational speeds, and pre-expander throttle valve.

[0013] Figure 6 is a functional schematic of an air management system, including a single drive shaft for driving the compressor and expander, or receiving power from the expander, and preexpander throttle valve, according to some embodiments.

[0014] Figure 7 is a functional schematic of an air management system, including a single drive shaft for driving the compressor and expander, or receiving power from the expander, preexpander throttle valve, expander bypass valve, and a water collection and recirculation system, according to some embodiments.

[0015] Figure 8 is a schematic of an air management system, including an expander with a one-way clutch, for a system that includes a fuel cell according to some embodiments.

[0016] Figure 9 shows an expander with a one-way clutch, according to some embodiments.

[0017] Figure 10 shows the expander shown in Figure 9, but from a different perspective than Figure 9, according to some embodiments.

[0018] Figure 11 shows the internal structure of the expander shown in Figures 9 and 10, according to some embodiments; the expander in this example includes a Roots machine with meshing rotors and a one-way clutch.

[0019] Figure 12A shows an axial view along the axes of the rotors of the expander shown in Figures 2, 3, and 4, according to some embodiments.

[0020] Figure 12B shows the cross-section 12B-12B marked in Figure 12A.

[0021] Figure 13 shows the cross-section 13-13 marked in Figure 12A.

[0022] Figure 14 shows the cross-section 13-13 marked in Figure 12A, with a portion surrounding the one-way clutch marked by the label “830-15.”

[0023] Figure 15 shows a closed-in view of a portion, labeled “830-15,” surrounding the oneway clutch in Figure 14.

[0024] Figure 16 is an exploded view of a one-way clutch in an expander, such as the one shown in Figure 15. Certain details, such as the precise geometry of the shaft, or inner ring, of the clutch, are known in the art and are not illustrated in the drawing.DETAILED DESCRIPTION

[0025] The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may alsoinclude embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and / or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and / or configurations discussed.

[0026] To optimize the electrochemical reactions, it is desirable to operate fuel cell under certain conditions, e.g., temperature, pressure, gas flowrate, and humidity. Such conditions can be maintained by fuel cell air management systems, also referred to as “fuel cell air systems.” Fuel cell air systems themselves consume electrical energy. Reducing the energy consumption of fuel cell air systems can improves the overall efficiency of the system operating on fuel cells. Certain aspects of the present disclosure can enhance performance, efficiency, and / or life of fuel cells.

[0027] A fuel cell air system can include a compressor for pushing air, and optionally moisture, into the fuel cell stack, where electrical power is generated from the reacting gasses, such as hydrogen and oxygen. Such a system can further include an expander, which is driven by the exhaust gas from the fuel cell to generate mechanical energy, and discharges the exhaust gas to the ambient at reduced temperature and pressure. The expander thus provides resistance to the air exiting the fuel cell stack and helps maintain a required pressure on the stack. Once torque equilibrium is reached among the motor, compressor and expander, mechanical energy is feed from the expander to the compressor and reduces the power needed from the motor. The mechanical energy generated by the expander is thus used to assist the powering of the compressor, thereby recovering energy that would otherwise be wasted. For example, an expander in some embodiments is a rotary machine, such as a Roots expander, with mechanical energy output in the form of rotation of a rotor shaft. The rotor shaft in some embodiments is coupled to a driveshaft of the compressor via a gear system, with the driveshaft of the compressor primarily driven by a motor, through the gear system, but also assisted by the rotor shaft of the expander. For example, the gear system can be a differential gear system, such as a planetary gear system. With such a differential system connecting the torque paths of a motor, there is a potential for the expander or compressor to rotate in an undesirable direction, i.e., reverse gas-flow direction, especially at the startup. Including a one-way restrictive device, such as a one-way clutch or rachet attached to the compressor or expander shaft, according to some embodiments, can prevent such undesirable rotation of the compressor and expander.

[0028] For example, an expander in some embodiments is a rotary machine, such as a Roots expander, with mechanical energy output in the form of rotation of a rotor shaft. The rotor shaft in some embodiments is coupled to a driveshaft of the compressor via a gear system, with the driveshaft of the compressor primarily driven by a motor, through the gear system, but also assisted by the rotor shaft of the expander. For example, the gear system can be a differential gear system, such as a planetary gear system. With such a differential system connecting the torque paths of a motor, there is a potential for the expander or compressor to rotate in an undesirable direction, i.e., reverse gas-flow direction, especially at the startup. Including a oneway restrictive device, such as a one-way clutch or rachet attached to the compressor or expander shaft, according to some embodiments, can prevent such undesirable rotation of the compressor and expander.

[0029] Certain examples disclosed in the present disclosure include certain aspects that are disclosed in Indian Patent Application No. 202111022706, entitled “HIGH EFFICIENCY FUEL CELL AIR MANAGEMENT SYSTEM” and filed on 21 May 2021, and International Patent Application No. PCT / EP2022 / 025238, entitled “HIGH EFFICIENCY FUEL CELL AIR MANAGEMENT SYSTEM,” filed on 23 May 2022, and published on 24 November 2022 as International Publication No. WO 2022 / 242915 AL Further, certain examples disclosed in the present disclosure include certain aspects that are disclosed in U.S. Provisional Application No. 63 / 519,552, entitled “HUMIDITY AND AIR CONTROL FOR FUEL CELL AIR SYSTEM” and filed on 14 August 2023. The Indian Patent Application No. 202111022706, International Patent Application No. PCT / EP2022 / 025238, and U.S. Provisional Application No. 63 / 519,552 are co-owned with the present application and are hereby incorporated herein by reference.

[0030] In some embodiments, such as the example shown in the functional diagram in Figure 1, an air management system 100 for a system, such as an electric vehicle, that includes a fuel cell, can manage air pressure, air and heat flow, and / or water inj ection / extraction between components as disclosed herein. Moreover, the air management system 100 may achieve an efficient power consumption to meet requirements of high efficiency systems. The air management system 100 in this example primarily includes a motor 110, compressor 120, expander 130, and recuperator 140. The air management system 100 may be coupled with a power source (not shown) for the motor 110, and a fuel cell 104. The air management system in some embodiments includes an intercooler (not shown) for adjusting the temperature of the air entering the fuel cell stack 104 from the recuperator 140. The air management system insome embodiments includes a water separator (not shown) connected to receiving the exhaust air from the expander and configured to extract water from the exhaust air.

[0031] The motor 110 in this example is configured to drive both the compressor 120 and the expander 130, or receive power from the expander. The motor 110 may comprise an electric motor powered by the power source. The motor 110 may include or be coupled to an inverter (not shown), which receives power from the power source. The inverter may include power electronics for the motor 110. The inverter may be additionally coupled to a motor cooling pump that is coupled to the motor 110. The motor cooling pump may be powered by the power source and may provide cooling for the motor 110, the inverter, or both. In some embodiments, the motor 110 includes a flux traction motor, such as a power-dense axial flux traction motor, and the inverter includes a silicon-carbide (SiC) inverter system. The flux traction motor and SiC inverter system may be appropriately scaled and may maintain an appropriate efficiency and power density. For instance, axial flux rotors may move cooling requirements to along radial positions. Moreover, the motor cooling pump may comprise a liquid cooling system that may cool the motor 110, the inverter, or both. It is noted that other motors, inverters, or cooling systems may be utilized. For example, a compressor flow cooling system may be utilized.

[0032] In some embodiments, the motor cooling pump may be configured to cool the motor 110 and / or other devices, such as the inverter. Sharing of the motor cooling pump resources may allow for one cooling loop between the inverter and the motor 110, which may provide improved and more efficient cooling, while reducing components and energy consumption.

[0033] In some embodiments, the motor 110 drives the compressor 120 and expander 130, or receive power from the expander, via one or more shafts 112, 114. In the example shown in Figure 1, the motor 110 drives, by a drive shaft 116, the shafts 112,114 via a gearbox 118. The gearbox 118 can include a gear set housed within a housing. In embodiments, the gear set includes appropriate gears, such as one or more timing gears. In some embodiments, the gear set included a differential gear, allowing the shaft 112 coupled to the compressor 120 and shaft 114 coupled to expander 130 to rotate at different rotational speeds. Alternatively, or more generally, the gear set can include a planetary gear set, including a sun gear, a ring gear, one or more planet gears interconnecting the sun and ring gears, and a carrier gear attached to the planet gears. In some embodiments, such as the one shown in Figure 1, the motor 110 drives the ring gear through the drive shaft 116 or a planetary gear 118; the carrier gear drives the compressor 120 through the shaft 112; and the sun gear drives the expander 130, or receives power from the expander, through the shaft 114. Other suitable gear / shaft configurations can be use. For example, the drive shaft 116 can be connected to drive the sun gear, and each ofthe ring gear and carrier gear can be used to drive a respective one of the compressor 120 or expander 130, or receive power from the expander 130. Coupling a single motor 110 to both the expander 130 and compressor 120, with or without gears coupling the expander and compressor, may reduce overall system size.

[0034] In some embodiments, the motor 110 drives compressor 120 and a generator on the expander 130. This may increase efficiency where the expander 130 output is taxed only about 4%, and electrical power added is taxed an additional about 4%.

[0035] In some embodiments, the expander 130 includes a Roots, screw or a variable geometry turbine expander. A Roots-style expander may receive wet exhaust (water vapor, liquid water, and air) from the recuperator 140. As described herein, the wet exhaust may be heated. The expander 130 may be fluidly connected to a water separator (e.g., a dryer). The water separator can separate water expelled by the expander. The water separator may be coupled to a waterline that may introduce water upstream of the compressor 120 in order to control the humidity in the fuel cell. For instance, water may be introduced upstream of the compressor 120 (e.g., in an inflow to the inlet of the compressor 120) by a water dosing device 128, such as a venturi or atomizing nozzle. This may increase compressor 120 efficiency and may wet the intake of the fuel cell 104. The water may be vaporized by the heat produced by the compressor 120, cooling the compressor 120, and thus reducing internal thermal expansion. It is further noted that, this may allow for reduced rotor and housing clearances which can lead to higher efficiencies. The water may act as a vapor barrier, making clearances more effective. Additionally or alternatively, the water serves to cool trapped air within the internal volume of the compressor 120, allowing for more mass in constant volume, increasing the pressure within the fuel cell and may provide humidity for the fuel cell, without the need for a separate humidifier.

[0036] In some embodiments, water can be injected in locations other than the inlet of the compressor 120. For example, water can be injected post-compressor, e.g., between the outlet of the compressor 120 and the recuperator 140, or between the outlet of the compressor 120 and fuel cell 104 in configurations without a recuperator.

[0037] In at least some embodiments, the expander 130 recovers part of the compression work by expanding the air exhausted by the fuel cell 104, as described herein. Recovering the work may allow for lower power consumption.

[0038] The compressor 120 in some embodiment comprises a positive displacement device, such as Roots compressor driven by the motor 110 via the gearbox 118. The compressor 120 includes a housing that defines an internal volume. The internal volume of the compressor 120includes rotors that are selectively driven by the motor 110. The internal volume is further fluidly coupled to an inlet of the recuperator 140.

[0039] The compressor 120 in some embodiments includes an inlet that receive ambient air and a fluid. For instance, the inlet in the example shown in Figure 1 receives water from a water line (not shown), which is connected to a water source, such the water separator.

[0040] The compressor 120 forces an air flow through the fuel cell 104, via the recuperator 140 (through the fresh air inlet 142 and fresh air outlet 146) and raises the pressure of such air flow such that higher power is generated by the fuel cell 104. Integration of water management with the compressor 120 may reduce system pressure drops and increase compression ratio and efficiency, and also allow for non-external water sources which would require refilling or a humidifier which requires additional space and energy.

[0041] The recuperator 140 may transfer heat from the fuel cell 104 via, for example, the exhaust air inlet 148 to the exhaust air outlet 144. The recuperator 140 may include a heat transfer device such as a cross-flow heat exchange device. In some embodiments, ambient air, after compression by the compressor 120, flows from the fresh air inlet 142 to the fresh air outlet 146; exhaust air from the fuel cell 104 flows from the exhaust air inlet 148 to the exhaust air outlet 144. The counter-flow heat exchanger puts the two flows in thermal contact with each other, thereby cooling the air from the compressor 120 and heating the air from the fuel cell 104. Heat may be transferred to the expander 130 via the exhaust air outlet 144. The expander 130 may utilize the transferred heat as energy thereby increasing enthalpy while also reducing a load on an intercooler and intercooler pump coupled to the fuel cell 104. Further, the recuperator 140 may transfer heat generated by the compressor 120 to useful energy for the expander 130 which improves system efficiency.

[0042] In an embodiment, the recuperator 140 includes a counter-flow, or cross-flow, heat exchanger that cools inflow received in the fresh air inlet 142, (e.g., from 150 degrees Celsius to 90 degrees Celsius) and transfers that heat to an exhaust flow flowing through the exhaust air outlet 144. The exhaust flow may be heated (e.g., from 90 degrees Celsius to 150 degrees Celsius). Accordingly, lost work in cooling the inflow by the intercooler may be avoided or reduced and additional work of expander 130 may be added. The power requirements of the air management system 100 may improve efficiency in comparison to traditional systems.

[0043] In some embodiments, for example, where cooling associated with water injection (e.g., by evaporative cooling) is sufficient to meet the target temperature for the fuel cell 104, the recuperator 140 can be by passed or eliminated.

[0044] The intercooler may comprise a heat exchanger configured to cool inflow to the fuelcell 104. In embodiments, the intercooler may include an intercooler pump (not shown) coupled to the power source. The intercooler may further reduce the temperature of the air out of the recuperator 140, before entering the fuel cell 104, to a point that is suitable for appropriate operation of the fuel cell 104.

[0045] In some embodiments, additive manufacturing processes may be utilized to build various components to reduce component sizes while balancing heat transfer effectiveness and flow restriction by considering entropy reduction. In examples, an additive manufacturing system may utilize finite element and computational fluid dynamics techniques, estimate recuperator 140 size by scaling the component results, and estimate cost and manufacturability. A resulting recuperator 140 may include a geometry designed to balance size and heat transfer efficiency.

[0046] In some embodiments, including the example shown in Figure 1, the air management system 100 further includes an expander bypass valve 152. The bypass valve 152 connects the exhaust air outlet 144 of the recuperator 140 to the outlet of the expander, providing a controlled air passage in parallel with the path through the expander 130. The bypass valve 152 can be used (e.g., by the fuel cell air system controller) to regulate the pressure in the fuel cell stack 104.

[0047] In some embodiments, such as those illustrated in Figure 2, a fuel cell air management system 200 is otherwise similar to the fuel cell air management system 100 in Figure 1, including the presence of an expander bypass valved 252, except that a single shaft 112 drives both the compressor 120 and expander 130, or receives power from the expander. A single-shaft configuration may reduce the complexity of the drive subsystem for driving the compressor and expander, or receive power from the expander, and / or enhance efficiency by reducing or eliminating energy dissipation by gears.

[0048] In some embodiments, such as those illustrated in Figure 3, a fuel cell air management system 300 is otherwise similar to the fuel cell air management system 100 in Figure 1 except that a throttle valve 352 is connected to the outlet of the expander 130, instead of the bypass valve 152 connected across the expander 130. A throttle valve 352 may serve to set the outlet / inlet pressure ratio of the expander 130, thereby optimize the performance of the expander 130, in some embodiments under certain operating conditions.

[0049] In some embodiments, such as those illustrated in Figure 4, a fuel cell air management system 400 is otherwise similar to the fuel cell air management system 300 in Figure 3, including the presence of a post-expander throttle valve 452, except that a single shaft 112 drives both the compressor 120 and expander 130, or receives power from the expander 130.A single-shaft configuration may reduce the complexity of the drive subsystem and / or enhance efficiency by reducing or eliminating energy dissipation by gears.

[0050] In some embodiments, such as those illustrated in Figure 5, a fuel cell air management system 500 is otherwise similar to the fuel cell air management system 300 in Figure 3 except that a throttle valve 552 is connected between to the inlet of the expander 130 and the recuperator 140, instead of to outlet of the expander 130. Such a pre-expander configuration may provide better control of the pressure at the fuel cell 104 in some embodiments under certain operating conditions.

[0051] In some embodiments, such as those illustrated in Figure 6, a fuel cell management manage system 600 is otherwise similar to the fuel cell air management system 300 in Figure 3, including the presence of a pre-expander throttle valve 652, except that a single shaft 112 drives both the compressor 120 and expander 130, or receive power from the expander 130. A single-shaft configuration may reduce the complexity of the drive subsystem and / or enhance efficiency by reducing or eliminating energy dissipation by gears.

[0052] In some embodiments, such as those illustrated in Figure 7, a fuel cell air management system 700 is otherwise similar to the fuel cell air management system 600 in Figure 6, but further includes an air filter 710 at the air intake end of the compressor 120, an expander bypass valve 720 connecting the intake end of the expander throttle valve 152 and the outlet of the expander 130, and a water collection and recirculation system 730. The water collection and recirculation system 730 in this example includes a water separator 732, a water reservoir 734, a water pump 736 and a water doser 738. The water separator 732 is connected between the recuperator 140 and expander throttle valve 152 includes a water discharge port for draining the water separated from the output air from the recuperator 140 into water reservoir 734. The water pump 736 is connected between the water reservoir 734 and the water doser, and is adapted to reintroduce the water collected in the water reservoir 734 into the airstream into the compressor 120 through the water doser 738. In this example, an intercooler 740 is connected between the recuperator 140 and fuel cell stack 104, and may include an intercooler pump (not shown).

[0053] In some embodiments, including those disclosed above, various components, including the motor 110 and valves 152, 252, 352, 452, 552, 652, 740 can be controlled by a controller, such as the fuel cell air system controller, to enhance the performance, efficiency and / or life of the overall fuel cell system or various components in the system.

[0054] In some embodiments, the air management systems for fuel cells utilizes an expander or compressor with a one-way clutch attached, engaged or otherwise linked to certain one or moreparts of the expander or compressor and adapted to constrain the motion of the one or more parts. In some embodiments, a one-way clutch is mounted on the shaft of a rotor in a Roots expander or compressor to ensure that the rotor rotates in only one direction.

[0055] Figure 8 depicts a schematic of an air management system 800 for a system, such as an electric vehicle, that includes a fuel cell, according to some embodiments. The air management system 800 in this example is similar to the system 100, depicted in Figure 1, with the expander 130 having a one-way clutch, to be described below in more detail.

[0056] In some embodiments at least one of the expander and compressor includes a one-way restrictive device, such as a one-way clutch or rachet attached to the compressor or expander shaft, to prevent rotation in an undesirable direction, i.e., the direction that reverses gas flow from the intended direction. In one exemplary embodiment, illustrated in Figures 9-16, the expander 830 in a fuel-cell air management system includes a housing 910, which includes an inlet portion 912, an outlet portion 914, and a midportion 916 interconnecting the inlet and outlet portions. The midportion 916 of the housing 910 substantially encloses the rotor assembly 920. As illustrated in Figure 11, the rotor assembly 920 in some embodiments includes a first rotor shaft 922 and a first rotor 924 mounted on the first rotor shaft. A first set of bearings 926, 928 are mounted in the midportion 916 of the housing 910 and rotatably support the first rotor shaft 922. A first gear 930 is mounted on the first rotor shaft 922. The rotor assembly 920 in some embodiments further includes a second rotor shaft 942 and a second rotor 944 mounted on the second rotor shaft. A second set of bearings 946, 948 are mounted in the midportion 916 of the housing 910 and rotatably support the second rotor shaft 942. A second gear 950 is mounted on the second rotor shaft 942. The first gear 930 and second gear 950 mesh with each other such that the first rotor 924 and second rotor 944 rotate cooperatively to move the exhaust gas from the fuel cell stack 104 from the inlet 912 through the midportion 916 to the outlet 914.

[0057] In some embodiments, a gear is mounted on, or extends from, an end portion of the first rotor shaft 922. In some embodiments, the gear forms a part of the planetary gear set 118; in other embodiments, the gear 932 is engaged to the planetary gear set 118. In operation, when equilibrium of torques has been reached among the motor, compressor 120 and expander 830, the rotors 924, 944 are driven by the exhaust gas from the fuel-cell stack 104 and, in turn, drives the compressor 120 through the gear set 118.

[0058] The rotors 924, 944 in this example have four helical lobes each but can have other numbers of lobes (e.g., two or six) and shapes of lobes (e.g., straight). The expander 830 inthis example is a Roots machine but can be of any other suitable type, including a screw or variable-geometry turbine expander.

[0059] In some embodiments, a one-way restrictive device is included in the expander or compressor, or both, to ensure that the expander and compressor do not rotate in the reverse direction from the desired direction. In some embodiments, such as the one shown in Figures 9-16, a one-way clutch 900 is mounted to the expander 830, more specifically to the first rotor shaft 922. In this example, clutch 900 is mounted at the opposite end of the first rotor shaft 922 from the gear 932 that outputs mechanical energy. In this example, as shown in further details in Figures 15 and 16, the end portion 934 forms or supports the inner race (or ring) of the clutch 900; the outer race (or ring) of the clutch 900 is mounted to the housing 910. The rollers 904 are disposed between the inner and outer races. In this example, the rotors 904 are supported by pins 906 that are mounted on the end walls 908 of the outer race 902. In other embodiments, the rollers 904 can be retained in braces. Instead of rollers, ball bearings can also be used for the one-way clutch 900.

[0060] The inner race 934 of the clutch 900 in the example shown in Figures 15 and 16 have sloped circumferential surface segments (not illustrated), forming a wedged space with the outer race 902 for each roller 904, such that the rollers 904 freely spin when the first rotor shaft 922 rotates in the desired direction but are jammed when the first rotor shaft 922 rotates in reverse. In other embodiments where the rollers are not fixed to the out race 902, the inner surface of the outer race 902 can have sloped segments, forming wedged spaces with the inner race 934 for rollers. Other types of one-way clutches can also be used.

[0061] In some embodiments, the one-way clutch is formed with, or mounted to, the second rotor shaft 942. The one-way clutch can also be disposed elsewhere but directly or indirectly engaged to either rotor shaft. For example, a one-way clutch can be disposed and configure to be engaged to either of gears 930 and 950. In other embodiments, a one-way clutch can be moved, for example by a solenoid or a servomotor, between a disengaged position, in which the clutch is disengaged from the rotor shafts to permit the rotor shafts to freely rotate, and an engaged position, in which the clutch is directly or indirectly engaged to the rotor shafts in the engaged position to prevent reverse rotation. In such embodiments, the one-way clutch can be moved, for example under the instruction from a controller, into the engaged position only under certain conditions, such as at the start-up. In other embodiments, one or more oneway clutches serves as a bearing supporting one or more rotor shafts. For example, any one or more of the bearings 926, 928, 946, 948 can be a one-way clutch.

[0062] Examples of the disclosure may be described according to the following aspects:

[0063] Aspect 1. An air management system for supplying air to a fuel cell, the air management system comprising: a compressor having an inlet adapted to receive ambient air, and an outlet adapted to be in fluid communication with an air inlet of a fuel cell; an expander having an inlet adapted to be in fluid communication with an air outlet of a fuel cell; a motor; a driving mechanism coupling the motor, compressor, and expander; and a throttle valve connected to the expander and adapted to control airflow through the expander.

[0064] Aspect 2. The air management system of aspect 1, further comprising a recuperator comprising a recuperator comprising: a fresh air inlet, a fresh air outlet, and a fresh air path connecting the fresh air inlet and fresh air outlet, the fresh air inlet being in fluid communication with the outlet of the compressor, and the fresh air outlet being adapted to be in fluid communication with the air inlet of the fuel cell; an exhaust air inlet, an exhaust air outlet, and an exhaust air path connecting the exhaust air inlet and exhaust air outlet, the exhaust air inlet being adapted to be in fluid communication with the outlet of the fuel cell, and the exhaust air outlet being in fluid communication with the inlet of the expander; and a heat exchanger in thermal contact with the fresh air path and exhaust air path.

[0065] Aspect 3. The air management system of aspect 1, further comprising a water injector adapted to introducing water into airflow to the air inlet of the fuel cell.

[0066] Aspect 4. The air management system of aspect 2, further comprising a water injector adapted to introducing water into airflow to the air inlet of the fuel cell.

[0067] Aspect 5. The air management system of aspect 1, 2, 3, or 4, further comprising a fluid path comprising a bypass valve and connected in parallel with the expander.

[0068] Aspect 6. The air management system of aspect 1, 2, 3, or 4, wherein the fluid communication between the inlet of the expander and the air outlet of the fuel cell passes through the throttle valve.

[0069] Aspect 7. The air management system of aspect 1, wherein: the expander has an outlet; and the throttle valve has an inlet connected to the outlet of the expander, and an outlet in fluid communication with ambient.

[0070] Aspect 8. The air management system of aspect 1, wherein the driving mechanism includes a shaft coupled to drive both the compressor and expander, and wherein the motor is adapted to drive the shaft.

[0071] Aspect 9. The air management system of aspect 1, wherein the driving mechanism includes a gear set interconnecting the compressor and expander and adapted to permit the compressor and expander to rotate at different rotational speeds, and wherein the motor is adapted to drive the gear set or the compressor.

[0072] Aspect 10. The air management system of aspect 8, further comprising a fluid path comprising a bypass valve and connected in parallel with the expander.

[0073] Aspect 11. The air management system of aspect 8, wherein the fluid communication between the inlet of the expander and the air outlet of the fuel cell passes through the throttle valve.

[0074] Aspect 12. The air management system of aspect 8, whereimthe expander has an outlet; and the throttle valve has an inlet connected to the outlet of the expander, and an outlet in fluid communication with ambient.

[0075] Aspect 13. The air management system of aspect 9, further comprising a fluid path comprising a bypass valve and connected in parallel with the expander.

[0076] Aspect 14. The air management system of aspect 10, wherein the fluid communication between the inlet of the expander and the air outlet of the fuel cell passes through the throttle valve.

[0077] Aspect 15. The air management system of aspect 9, wherein: the gear set comprises a planetary gear comprising a sun gear, a ring gear, one or more planet gears and a carrier connected to the one or more planet gears; the compressor is adapted to be driven by a first one of the sun gear, ring gear, and carrier; the expander is adapted to drive or be driven a second one of the sun gear, ring gear, and carrier; and the motor is adapted to drive a third one of the sun gear, ring gear, and carrier.

[0078] Aspect 16. A fuel cell system, comprising: a fuel cell comprising: a gas inlet adapted to supply an oxidizing gas; a gas outlet; and a fuel cell stack adapted to generate electricity from an electrochemical reaction between a fuel and the oxidizing gas; and an air management system for supplying air to a fuel cell, the air management system comprising: a compressor having an inlet adapted to receive oxidizing gas, and an outlet adapted to be in fluid communication with the gas inlet of a fuel cell; an expander having an inlet adapted to be in fluid communication with the gas outlet of a fuel cell; a motor; a driving mechanism coupling the motor, compressor, and expander, and configured to enable the motor to drive the compressor and expander, or receive power from the expander; and a throttle valve connected to the expander and adapted to control airflow through the expander.

[0079] Aspect 17. A method of supplying an oxidizing gas to a fuel cell, the method comprising: compressing an oxidizing gas with a compressor; supplying the compressed oxidizing gas to a fuel cell adapted to generate electricity from an electrochemical reaction using a fuel and the oxidizing gas, and generating an exhaust gas; receiving the exhaust gas from the fuel cell; generating, using an expander, mechanical energy from the receivedexhaust gas; controlling flow of the exhaust gas received by the expander; and transferring power between the compressor, expander, and a motor through a driving mechanism.

[0080] Aspect 18. The method of aspect 17, wherein the controlling flow of exhaust gas received by the expander comprises diverting at least a portion of the exhaust gas received from the fuel cell through bypass path in parallel with the expander.

[0081] Aspect 19. The method of aspect 17, wherein the controlling flow of exhaust gas received by the expander comprises restricting the flow of the exhaust gas received from the fuel cell to an inlet of the expander.

[0082] Aspect 20. The air management system of aspect 11, further comprising a bypass throttle valve interconnecting the inlet of the throttle valve in the fluid communication between the inlet of the expander and the air outlet of the fuel cell and the outlet of the expander.

[0083] Aspect 21. An air management system for supplying air to a fuel cell, the air management system comprising: a compressor having an inlet adapted to receive air, and an outlet adapted to be in fluid communication with an air inlet of a fuel cell; an expander having an inlet adapted to be in fluid communication with an air outlet of the fuel cell; and a one-way restrictive device engageable to the compressor or expander and adapted to permit gas flow only a predetermined direction through the compressor or expander.

[0084] Aspect 22. The air management system of aspect 21, wherein the one-way restrictive device comprises a one-way clutch.

[0085] Aspect 23. The air management system of aspect 22, wherein the compressor or expander is Roots machine having one or more rotor shafts, and the one-way clutch is attached to one of the one or more rotor shafts and adapted to permit the shaft to rotate in only one direction.

[0086] Aspect 24. A fuel cell system, comprising: a fuel-cell; an air management system for supplying air to the fuel cell, the air management system comprising: a compressor having an inlet adapted to receive air, and an outlet adapted to be in fluid communication with an air inlet of the fuel cell; an expander having an inlet adapted to be in fluid communication with an air outlet of the fuel cell; and a one-way restrictive device engageable to the compressor or expander and adapted to permit gas flow only a predetermined direction through the compressor or expander.

[0087] Aspect 25. The fuel cell of aspect 24, wherein the one-way restrictive device comprises a one-way clutch.

[0088] Aspect 26. The fuel cell of aspect 25, wherein the compressor or expander is Roots machine having one or more rotor shafts, and the one-way clutch is attached to one of the one or more rotor shafts and adapted to permit the shaft to rotate in only one direction.

[0089] Although various examples and examples are described herein, those of ordinary skill in the art will understand that many modifications may be made thereto within the scope of the present disclosure. Accordingly, it is not intended that the scope of the disclosure in any way be limited by the examples provided.

Claims

CLAIMSWhat is claimed is:

1. An air management system for supplying air to a fuel cell, the air management system comprising: a compressor having an inlet adapted to receive ambient air, and an outlet adapted to be in fluid communication with an air inlet of a fuel cell; an expander having an inlet adapted to be in fluid communication with an air outlet of a fuel cell; a motor; a driving mechanism coupling the motor, compressor, and expander; and a throttle valve connected to the expander and adapted to control airflow through the expander.

2. The air management system of claim 1, further comprising a recuperator comprising a recuperator comprising: a fresh air inlet, a fresh air outlet, and a fresh air path connecting the fresh air inlet and fresh air outlet, the fresh air inlet being in fluid communication with the outlet of the compressor, and the fresh air outlet being adapted to be in fluid communication with the air inlet of the fuel cell; an exhaust air inlet, an exhaust air outlet, and an exhaust air path connecting the exhaust air inlet and exhaust air outlet, the exhaust air inlet being adapted to be in fluid communication with the outlet of the fuel cell, and the exhaust air outlet being in fluid communication with the inlet of the expander; and a heat exchanger in thermal contact with the fresh air path and exhaust air path.

3. The air management system of claim 1, further comprising a water injector adapted to introducing water into airflow to the air inlet of the fuel cell.

4. The air management system of claim 2, further comprising a water injector adapted to introducing water into airflow to the air inlet of the fuel cell.

5. The air management system of claim 1, 2, 3, or 4, further comprising a fluid path comprising a bypass valve and connected in parallel with the expander.

6. The air management system of claim 1, 2, 3, or 4, wherein the fluid communication between the inlet of the expander and the air outlet of the fuel cell passes through the throttle valve.

7. The air management system of claim 1, wherein: the expander has an outlet; and the throttle valve has an inlet connected to the outlet of the expander, and an outlet in fluid communication with ambient.

8. The air management system of claim 1, wherein the driving mechanism includes a shaft coupled to drive both the compressor and expander, and wherein the motor is adapted to drive the shaft.

9. The air management system of claim 1, wherein the driving mechanism includes a gear set interconnecting the compressor and expander and adapted to permit the compressor and expander to rotate at different rotational speeds, and wherein the motor is adapted to drive the gear set or the compressor.

10. The air management system of claim 8, further comprising a fluid path comprising a bypass valve and connected in parallel with the expander.

11. The air management system of claim 8, wherein the fluid communication between the inlet of the expander and the air outlet of the fuel cell passes through the throttle valve.

12. The air management system of claim 8, wherein: the expander has an outlet; and the throttle valve has an inlet connected to the outlet of the expander, and an outlet in fluid communication with ambient.

13. The air management system of claim 9, further comprising a fluid path comprising a bypass valve and connected in parallel with the expander.

14. The air management system of claim 10, wherein the fluid communication between the inlet of the expander and the air outlet of the fuel cell passes through the throttle valve.

15. The air management system of claim 9, wherein: the gear set comprises a planetary gear comprising a sun gear, a ring gear, one or more planet gears and a carrier connected to the one or more planet gears; the compressor is adapted to be driven by a first one of the sun gear, ring gear, and carrier; the expander is adapted to drive or be driven a second one of the sun gear, ring gear, and carrier; and the motor is adapted to drive a third one of the sun gear, ring gear, and carrier.

16. The air management system of claim 4, wherein the fluid communication between the inlet of the expander and the air outlet of the fuel cell passes through the throttle valve, the air management system further comprising: a bypass valve having an inlet connected to the inlet of the throttle valve, and an outlet connected to the outlet of the expander; and a water collection and recirculation system connected between the exhaust air outlet of the recuperator and the fresh air inlet of the compressor, and adapted to collect water from an airflow from the exhaust air outlet and introduce the collected water into the compressor.

17. A fuel cell system, comprising: a fuel cell comprising: a gas inlet adapted to supply an oxidizing gas; a gas outlet; and a fuel cell stack adapted to generate electricity from an electrochemical reaction between a fuel and the oxidizing gas; and an air management system for supplying air to a fuel cell, the air management system comprising: a compressor having an inlet adapted to receive oxidizing gas, and an outlet adapted to be in fluid communication with the gas inlet of a fuel cell;an expander having an inlet adapted to be in fluid communication with the gas outlet of a fuel cell; a motor; a driving mechanism coupling the motor, compressor, and expander, and configured to enable the motor to drive the compressor and expander, or receive power from the expander; and a throttle valve connected to the expander and adapted to control airflow through the expander.

18. An air management system for supplying air to a fuel cell, the air management system comprising: a compressor having an inlet adapted to receive air, and an outlet adapted to be in fluid communication with an air inlet of a fuel cell; an expander having an inlet adapted to be in fluid communication with an air outlet of the fuel cell; and a one-way restrictive device engageable to the compressor or expander and adapted to permit gas flow only a predetermined direction through the compressor or expander.

19. The air management system of claim 18, wherein the one-way restrictive device comprises a one-way clutch.

20. The air management system of claim 19, wherein the compressor or expander is Roots machine having one or more rotor shafts, and the one-way clutch is attached to one of the one or more rotor shafts and adapted to permit the shaft to rotate in only one direction.

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