A fuel cell system includes: a fuel cell; an anode gas supply flow path for supplying an anode gas to the fuel cell; an anode gas discharge flow path for discharging an anode off gas from the fuel cell; an anode gas circulation flow path for connecting the anode gas supply flow path and the anode gas discharge flow path to each other; a circulation device provided on the anode gas circulation flow path and serving for supplying the anode off gas to the anode gas supply flow path; and a controller. When liquid water is residing in the circulation device, the controller controls a circulation flow rate of the circulation device to discharge the liquid water residing in the circulation device. The controller restricts an increasing rate of the circulation flow rate of the circulation device if it is decided that a quantity of the liquid water residing in the circulation device is equal to or more than a specified value.

A fuel cell system is disclosed, which includes an anode recirculation loop having a fuel cell stack for generating power, a flowmeter, a current sensor and a processor. The flowmeter is configured for measuring a fuel flow rate provided into the anode recirculation loop. The current sensor is configured for measuring a current drawn from the fuel cell stack. The processor is configured for determining a steam to carbon ratio in the anode recirculation loop based on the measured fuel flow rate and the measured current. The fuel cell system further includes a temperature sensor for measuring a temperature in the anode recirculation loop. The process is configured for determining the steam to carbon ration further based on the measured temperature. A method for operating the fuel cell system and a fuel cell power plant are also disclosed.

A fuel cell control method includes calculating an amount of water in a humidifier using a production amount of water at a cathode of a fuel cell, a discharge amount of saturated vapor and a discharge amount of water at an anode, judging whether or not a vehicle is in a driving state using state information of the vehicle, judging humidity of air in the fuel cell stack upon judging that the vehicle is in the driving state, increasing RPM of an air blower and activating the air blower when the amount of water is greater than a first threshold and a second condition is satisfied, if first conditions are satisfied, and activating a heater when the amount of water is greater than a second threshold, if the first conditions are not satisfied.

Various embodiments of the present application are directed to methods of measuring a mass flow rate of at least one exhaust gas constituent in an exhaust gas of a fuel cell. In one example embodiment, the method includes the steps of measuring a volumetric flow rate of the exhaust gas; using a gas sensor to determine a concentration of the at least one exhaust gas constituent, and calculating the mass flow rate of the exhaust gas constituent using the volumetric flow rate of the exhaust gas and the determine concentration of the at least one exhaust gas constituent.

A fuel cell system includes an anode configured to output an anode exhaust stream comprising hydrogen, carbon dioxide, and water; and a membrane dryer configured to receive the anode exhaust stream, remove water from the anode exhaust stream, and output a membrane dryer outlet stream. The membrane dryer includes a first chamber configured to receive the anode exhaust stream; a second chamber configured to receive a purge gas; and a semi-permeable membrane separating the first chamber and the second chamber. The semi-permeable membrane is configured to allow water to diffuse therethrough, thereby removing water from the anode exhaust stream. The membrane dryer may further be configured to remove hydrogen from the anode exhaust stream.

A method for controlling a fuel cell vehicle is provided. The method includes setting a target purge degree of an anode gas and a target opening degree of an air pressure control valve and determining whether a fuel cell stack is in a power generation stop state. When the fuel cell stack is in the power generation stop state, when the anode gas is purged from the anode based on the target purge degree and the target opening degree, whether hydrogen in the anode gas will flow backwards to a stack enclosure is determined. When the hydrogen flows backwards, at least one of the target purge degree and the target opening degree to a level at which the backflow of the hydrogen is prevented is modified, and the anode gas from the anode based on the modified target purge degree and the modified target opening degree is purged.

In a case that activation is implemented on a fuel cell, a variable voltage is applied to a membrane electrode assembly while a first gas is supplied to an anode and a second gas is supplied to a cathode. Thereafter, while a constant voltage is applied to the membrane electrode assembly, liquid water is generated at the anode or the cathode. Alternatively, the membrane electrode assembly is made to generate electricity. During the generation of electricity, liquid water is generated at the anode or the cathode.

A fuel cell vehicle is equipped with a fuel cell system including a gas liquid separation unit for separating gas and liquid and discharging the separated liquid. The fuel cell vehicle includes an acceleration sensor for detecting information regarding acceleration, and a control unit for estimating the discharge state of the liquid from the gas liquid separation unit based on the information regarding acceleration. Based on acceleration applied to the liquid in the gas liquid separation unit, the control unit can estimate whether the liquid is discharged from the gas liquid separation unit or the liquid is not discharged and remains as the remaining liquid in the gas liquid separation unit.

Methods and systems are described for optimizing water discharge in fuel cell vehicles. The system includes a fuel cell stack, a blower for purging water from the fuel cell stack and a controller. The controller detects that an ambient temperature satisfies a threshold temperature. The controller determines the fuel cell vehicle is approaching a stopping location. The controller calculates a water discharge time prediction necessary to purge excess water from the fuel cell stack while the fuel cell vehicle is operating in response to detecting that the ambient temperature satisfies the threshold temperature and the fuel cell vehicle is approaching the stopping location. The water discharge time prediction is calculated based on the blower operating while the fuel cell stack is in at least one of an idle state and a stopped state as the fuel cell vehicle approaches the stopping location.

A system and method of controlling water imbalance in an electrochemical cell is provided. The method includes determining a present water imbalance in the electrochemical cell by summing a water.sub.in and a water.sub.created less a water.sub.out. Water.sub.in represents an amount of water introduced into the electrochemical cell by an oxidant feed gas; water.sub.created represents an amount of water created by the electrochemical cell from the electrochemical reaction; and water.sub.out represents an amount of water discharged from the electrochemical cell by an oxidant exhaust gas. The method includes tracking a cumulative water imbalance during operation of the electrochemical cell by repeatedly determining the present water imbalance and continuing to sum the results during operation. And, the method also includes adjusting a flow rate of the oxidant feed gas entering the electrochemical cell based on the cumulative water imbalance.