Hydrogen Flow Control Methods for Fuel Cell Efficiency

Pulse hydrogen supply system for a proton exchange membrane fuel cell that can provide a pulsating hydrogen flow to remove water droplets from the fuel cell. The system has two vessels, one high-pressure and the other low-pressure, which can generate pressure waves through opening and closing of electromagnetic valves. This pulsating hydrogen flow helps dynamically dislodge and remove water droplets that can accumulate in the fuel cell, ensuring proper humidification of the membrane, thus improving cell performance and durability.

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A recirculation system for purging and recirculating hydrogen in a fuel cell stack, which avoids the need for external compressors and enables recovery of purged hydrogen. The system uses a tank with outlet connected to the fuel cell and an inlet to receive purged water and hydrogen. A one-way valve allows flow from the fuel cell to the tank during normal operation when pressure is high. When pressure drops due to hydrogen consumption, the valve opens to allow recirculation back to the fuel cell. This recirculates purged hydrogen without external compression.

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A fuel cell system for vehicles like tractors and backhoes that adjusts the temperature inside the hydrogen tank based on the amount of hydrogen remaining. When the hydrogen level gets low, the system increases the tank temperature to release more available gas. This allows quick response to load changes without reducing fuel cell output. It also reduces unused hydrogen left in the tank.

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Automated switching between multiple hydrogen fuel tanks on a mobile power generator to provide continuous power and avoid interruptions. A pressure-based latching switch monitors the fuel tank pressures, and automatically switches from an empty tank to a full tank to maintain a constant fuel supply to the generator's fuel cell system.

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Preventing accidental closing of fuel cell hydrogen injectors when starting power-hungry vehicle auxiliaries. A fuel cell vehicle has a hydrogen injector that opens when a current threshold is reached. The injector controller increases the current target when it detects start signals from high-power auxiliaries like AC. This prevents power dips from closing the injector prematurely. However, if a voltage converter supplies the injector, the target is not increased if converter output exceeds the main power supply.

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Process and system to mitigate overpressure in fuel cell anodes to prevent damage in the event of injector failure by detecting a stuck open injector and closing the hydrogen valve to prevent excess supply. The fuel cell stack continues to run and consume hydrogen to deplete the anode pressure. Other actions include opening the anode bleed valve, increasing cathode air pressure, and modulating load to maintain pressure balance.

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Method to maintain constant hydrogen partial pressure in a fuel cell stack during purging cycles. It involves measuring hydrogen concentration at the stack outlet and updating the target hydrogen supply pressure based on the nitrogen crossover pressure increase between purges. This compensates for nitrogen dilution during purging to prevent hydrogen pressure drops. The target pressure is calculated by summing the normal hydrogen pressure needs with the crossover nitrogen pressure.

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Determining and controlling excess hydrogen flow in a fuel cell stack to improve efficiency and longevity without overcomplicating the system. The method involves mixing two fuel streams to form a third stream that enters the anode inlet. A controller compares the excess hydrogen ratio of the mixed flow to a target. If excess is too high, it adjusts components like blowers, ejectors, or bypass valves to lower excess. This prevents over-fueling without measuring stack internal pressure.

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Fuel cell system that prevents moisture ingress and freezing in the hydrogen circulation pump to improve reliability. The system has a hydrogen recirculation passage connected to the fuel cell stack and a hydrogen circulation pump to recirculate emission gas. The pump housing merges the recirculation and main hydrogen flow passages. But it also has a bypass around the merge point controlled by a valve. This allows normal operation with full recirculation, but when the system is shut down, the bypass can be opened to divert hydrogen flow around the pump housing to prevent condensation moisture from entering the pump body.

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Preventing clogging of fuel cell hydrogen channels by reversing pump direction during cell stack shutdown. The fuel cell system has a hydrogen pump in the circulation passage connecting the channel inlet and outlet. It feeds hydrogen into the cells during normal operation at a rate exceeding minimum for power generation. During stack shutdown, it reverses direction to extract hydrogen through the outlet, moving water to the cell center. This prevents channel clogging by preventing water freezing in the inlet during future starts.

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Fuel cell system and control method to improve power generation efficiency, especially during intermittent operation when hydrogen cross-leakage is higher. The system has a circulation pump to recirculate unused anode exhaust gas back to the anode. The pump speed is optimized based on current level to balance reducing cross-leakage with minimizing pump power consumption. In normal operation, pump speed is lower. In intermittent operation, pump speed increases to lower anode hydrogen partial pressure and reduce cross-leakage. This improves efficiency by ensuring enough hydrogen for power generation without excessive pump power.

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Controlling hydrogen supply to a fuel cell stack using a jet pump and proportional control solenoid valve to improve recirculation flow efficiency at low power levels. The method involves switching between pulse flow control and proportional control for the valve based on stack power. At low power, a peak-hold method is used to reduce valve plunger impulses. At high power, proportional control is used. This allows sufficient recirculation flow even at low loads without additional pumps or blowers.

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Fuel cell system with integrated surge tank and variable gas supply device to reduce vibration and noise from fuel pulsations. The system has a surge tank on the fuel cell gas supply line upstream of the variable gas supply device. This surge tank smoothens the fuel gas pressure fluctuations before they reach the variable gas supply device. It also has an integrated surge tank and variable gas supply device assembly that is fixed to the fuel cell. This eliminates misalignment between the two devices that could cause vibrations. The integrated design also allows direct pressure sensing on the surge tank to accurately control the variable gas supply device.

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Reducing hydrogen exhaust from fuel cells during low efficiency operation and estimating hydrogen generation in fuel cell cathodes. To reduce hydrogen exhaust, the fuel cell system regulates dilution of cathode gas based on anode gas in the cathode. During low efficiency, bypass valves allow some cathode gas to bypass the cell and dilute the exhaust hydrogen. A valve controls the amount based on anode gas in the cathode. This prevents excessive hydrogen in the exhaust. To estimate cathode hydrogen generation during low efficiency, the system estimates air stoichiometry and hydrogen generation using cell voltage, current, and temperature. This provides more accurate hydrogen generation estimates compared to normal operation.

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Fuel cell system with compact and simplified hydrogen recycling to improve efficiency and reduce complexity compared to separate fuel pumps. The system recirculates hydrogen off-gas back to the fuel cell using an ejector instead of a separate pump. A flow rate sensor determines if the hydrogen feed is below a threshold. If so, a pressure varying mechanism increases and decreases the hydrogen feed pressure intermittently. This prevents excessive hydrogen permeation into the cathode during intermittent operation.

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A gas flow control assembly for fuel cells that accurately controls fuel flow to the anode without requiring expensive analyzers. The assembly uses a hydrogen sensor on the anode exhaust to detect hydrogen concentration. Based on the sensor reading, it adjusts the fuel flow to the anode. This allows precise control without needing an online analyzer for fuel composition. A cooling system condenses water from the exhaust to separate it, and the sensor measures hydrogen in the water-separated exhaust gas. This provides reliable fuel flow control unaffected by fuel composition variations.

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Reducing carbon corrosion and ruthenium migration in fuel cell anodes during shutdown and restart to prevent degradation. The technique involves storing excess hydrogen from the primary source in a secondary source during normal operation. During shutdown and restart, hydrogen from the secondary source is added to the anode gas mixture to prevent oxygen/air from migrating and stabilize the anode potential. This remediates the anode gas composition to prevent carbon corrosion and ruthenium migration.

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Balancing hydrogen flow through a fuel cell stack to optimize performance by equalizing flow distribution in the flow field channels. The method involves branched channel sections that connect multiple channels to balance flow in areas where hydrogen volume decreases during cell reaction. This compensates for uneven flow caused by different channel lengths upstream and downstream of the active region where fuel is consumed. By branching channels to balance flow, it prevents uneven fuel distribution in the flow field that can affect stoichiometry and performance.

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Fuel cell system with reduced hydrogen emissions during low power generation. The system allows decreased reactant gas supply to the fuel cell for lower power generation. The voltage limit is set so anode gas formation in the cathode is kept below a threshold. This prevents excessive hydrogen in the exhaust. The system uses a bypass valve to dilute cathode gas with oxidant bypassing the fuel cell.

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Fuel cell system with a hydrogen concentration sensor that maintains accurate hydrogen measurement over long-term use. The system reduces impurities in the gas passage containing the sensor, measures hydrogen concentration, and corrects the sensor reference point based on the measured value. This compensates for any drift in the sensor accuracy due to impurities. The impurities are reduced by discharging anode off-gas with a valve while supplying hydrogen, or by circulating anode off-gas back to the hydrogen supply.

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