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Systems and methods for regulating fuel cell air flow, such as during low loads and/or cold temperature operation. These systems and methods may include providing a thermal management fluid, such as air, to the fuel cell stack, transferring thermal energy between the thermal management fluid and the

Systems and methods for regulating fuel cell air flow, such as during low loads and/or cold temperature operation. These systems and methods may include providing a thermal management fluid, such as air, to the fuel cell stack, transferring thermal energy between the thermal management fluid and the fuel cell stack, and varying the flow rate of the thermal management fluid that comes into contact with the fuel cell stack to maintain the temperature of the fuel cell stack within an acceptable temperature range. Varying the flow rate of the thermal management fluid may include varying the overall supply rate of the thermal management fluid within the fuel cell system and/or providing an alternative flow path for the thermal management fluid such that a portion of the thermal management fluid supplied by the fuel cell system does not come into contact with the fuel cell stack.

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1. A fuel cell system, comprising: a fluid conduit;a fuel cell stack in fluid communication with the fluid conduit, wherein the fuel cell stack is configured to receive a stack thermal management fluid stream that flows through the fluid conduit to regulate a temperature of the fuel cell stack, wher

1. A fuel cell system, comprising: a fluid conduit;a fuel cell stack in fluid communication with the fluid conduit, wherein the fuel cell stack is configured to receive a stack thermal management fluid stream that flows through the fluid conduit to regulate a temperature of the fuel cell stack, wherein the fuel cell stack includes an open cathode fuel cell stack, wherein the stack thermal management fluid stream supplies an oxidant to the fuel cell stack, and further wherein the fuel cell stack consumes at least a portion of the oxidant with a fuel and produces an electrical output therefrom;a flow-regulating device in fluid communication with the fluid conduit, wherein the flow-regulating device is configured to passively control a flow rate of a bypass stream associated with the fluid conduit, wherein the flow-regulating device includes at least an open configuration, in which the bypass stream may pass therethrough, and a closed configuration, in which at least a substantial portion of the bypass stream may not pass therethrough, and further wherein the flow-regulating device is configured to passively transition between the open configuration and the closed configuration responsive to a value of a variable associated with the fuel cell system; anda thermal management fluid drive assembly in fluid communication with the fluid conduit, wherein the thermal management fluid drive assembly is configured to provide a motive force to a thermal management fluid drive assembly stream that flows through the fluid conduit, and further wherein the fluid conduit, the fuel cell stack, the flow-regulating device, and the thermal management fluid drive assembly are configured such that:(i) the thermal management fluid drive assembly stream includes the stack thermal management fluid stream;(ii) responsive to the flow-regulating device being in the open configuration, the thermal management fluid drive assembly stream includes the bypass stream and the bypass stream bypasses the fuel cell stack such that a flow rate of the stack thermal management fluid stream is less than a flow rate of the thermal management fluid drive assembly stream; and(ii) responsive to the flow-regulating device being in the closed configuration, the flow rate of the stack thermal management fluid stream is equal or substantially equal to the flow rate of the thermal management fluid drive assembly stream. 2. The fuel cell system of claim 1, wherein the bypass stream flows through the fluid conduit. 3. The fuel cell system of claim 1, wherein the fuel cell stack is configured to receive the stack thermal management fluid stream from the fluid conduit, the flow-regulating device is configured to receive the bypass stream from the fluid conduit, and the thermal management fluid drive assembly is configured to supply the thermal management fluid drive assembly stream to the fluid conduit. 4. The fuel cell system of claim 1, wherein the thermal management fluid drive assembly is configured to create a positive pressure between the fuel cell stack and the thermal management fluid drive assembly. 5. The fuel cell system of claim 1, wherein the fuel cell stack receives an ambient air stream from an ambient environment proximal to the fuel cell system to generate the stack thermal management fluid stream, wherein the fuel cell stack is configured to supply the stack thermal management fluid stream to the fluid conduit, wherein the flow-regulating device is configured to supply the bypass stream to the fluid conduit, and further wherein the thermal management fluid drive assembly is configured to receive the thermal management fluid drive assembly stream from the fluid conduit. 6. The fuel cell system of claim 1, wherein the thermal management fluid drive assembly is configured to create a negative pressure between the fuel cell stack and the thermal management fluid drive assembly. 7. The fuel cell system of claim 1, wherein the flow-regulating device is configured to passively transition between the open configuration and the closed configuration responsive to the value of the variable associated with the fuel cell system exceeding a threshold value. 8. The fuel cell system of claim 7, wherein the threshold value includes at least one of a threshold pressure and a threshold pressure differential of at least one of the stack thermal management fluid stream, the bypass stream, the thermal management fluid drive assembly stream, and an ambient pressure. 9. The fuel cell system of claim 7, wherein the threshold value is a threshold pressure differential, and further wherein the threshold pressure differential includes at least one of a pressure differential across the flow-regulating device, a pressure differential across the fuel cell stack, a pressure differential across the thermal management fluid drive assembly, and a pressure differential between an interior of the fluid conduit and an exterior of the fluid conduit. 10. The fuel cell system of claim 1, wherein the flow-regulating device includes an orifice and plate assembly that includes an orifice plate and a separate sealing plate, wherein the orifice plate defines an orifice, and further wherein the sealing plate is operatively attached to the orifice plate and is configured to transition the orifice and plate assembly between the open configuration and the closed configuration via translation relative to the orifice plate to selectively permit or restrict flow of the bypass stream through the orifice. 11. The fuel cell system of claim 1, wherein the flow-regulating device is maintained in at least one of the open configuration and the closed configuration by at least one of gravity and a biasing mechanism. 12. The fuel cell system of claim 1, wherein the fuel cell system includes a plurality of flow-regulating devices. 13. The fuel cell system of claim 12, wherein a first portion of the plurality of flow-regulating devices is configured to transition between the open configuration and the closed configuration at a different magnitude of the variable associated with the fuel cell system than a second portion of the plurality of flow-regulating devices. 14. The fuel cell system of claim 1, wherein the flow-regulating device includes a plurality of plate assemblies, wherein a portion of the plurality of plate assemblies includes an orifice, and further wherein the flow-regulating device is configured to provide a plurality of discrete flow restrictions to a flow rate of the bypass stream. 15. The fuel cell system of claim 1, wherein the stack thermal management fluid stream does not include the bypass stream when the bypass stream is flowing through the flow-regulating device. 16. The fuel cell system of claim 1, wherein the thermal management fluid drive assembly includes at least one of a fan, a vane, a pump, a compressor, an impeller, and an ejector. 17. The fuel cell system of claim 1, wherein the stack thermal management fluid stream, the bypass stream, and the thermal management fluid drive assembly stream include a thermal management fluid. 18. The fuel cell system of claim 17, wherein the thermal management fluid includes air, wherein the stack thermal management fluid stream is a stack air stream, wherein the thermal management fluid drive assembly is an air drive assembly, and further wherein the thermal management fluid drive assembly stream is an air drive assembly stream. 19. The fuel cell system of claim 1, in combination with a source of hydrogen gas configured to supply hydrogen gas to the fuel cell stack. 20. A method of controlling a temperature of a fuel cell stack, the method comprising: supplying a thermal management fluid to the fuel cell system of claim 1 as at least one of a stack thermal management fluid stream, a bypass stream, and a thermal management fluid drive assembly stream; andcontrolling a flow rate of the stack thermal management fluid stream that is supplied to the fuel cell stack. 21. The method of claim 20, wherein the controlling includes actively controlling a flow rate of the thermal management fluid drive assembly stream with a thermal management fluid drive assembly. 22. The method of claim 20, wherein the controlling includes passively controlling a flow rate of the bypass stream with a flow-regulating device. 23. The method of claim 22, wherein the passively controlling includes passively transitioning the flow-regulating device between an open configuration, in which the bypass stream may pass therethrough, and a closed configuration, in which at least a substantial portion of the bypass stream may not pass therethrough, responsive to a pressure differential across the flow-regulating device. 24. The method of claim 23, wherein the passively controlling includes controlling without the use of at least one of a controller, a detector, and an actuator. 25. The method of claim 24, wherein the passively controlling includes controlling without the use of any of a controller, a detector, and an actuator. 26. A fuel cell system, comprising: a fluid conduit;a fuel cell stack in fluid communication with the fluid conduit, wherein the fuel cell stack is configured to receive a stack thermal management fluid stream that flows through the fluid conduit, wherein the stack thermal management fluid stream includes a stack air stream that is supplied from an ambient environment proximal to the fuel cell stack, and further wherein the fuel cell stack at least one of receives the stack thermal management fluid stream from the fluid conduit and supplies the stack thermal management fluid stream to the fluid conduit;a flow-regulating device in fluid communication with the fluid conduit, wherein the flow-regulating device is configured to passively control a flow rate of a bypass stream, wherein the flow-regulating device at least one of receives the bypass stream from the fluid conduit and supplies the bypass stream to the fluid conduit, wherein the flow-regulating device includes an open configuration, in which the bypass stream may pass therethrough, and a closed configuration, in which at least a substantial portion of the bypass stream may not pass therethrough, and further wherein the flow-regulating device is configured to passively transition between the open configuration and the closed configuration responsive to a value of a variable associated with the fuel cell system; anda thermal management fluid drive assembly in fluid communication with the fluid conduit, wherein the thermal management fluid drive assembly is configured to provide a motive force to a thermal management fluid drive assembly stream, and further wherein the fluid conduit, the fuel cell stack, the flow-regulating device, and the thermal management fluid drive assembly are configured such that:(i) the thermal management fluid drive assembly at least one of receives the thermal management fluid drive assembly stream from the fluid conduit and supplies the thermal management fluid drive assembly stream to the fluid conduit;(ii) the thermal management fluid drive assembly stream includes the stack thermal management fluid stream;(iii) responsive to the flow-regulating device being in the open configuration, the thermal management fluid drive assembly stream also includes the bypass stream and the bypass stream bypasses the fuel cell stack such that a flow rate of the stack thermal management fluid stream is less than a flow rate of the thermal management fluid drive assembly stream; and(iv) responsive to the flow-regulating device being in the closed configuration, the flow rate of the stack thermal management fluid stream is equal or substantially equal to the flow rate of the thermal management fluid drive assembly stream.