A fuel cell failure diagnostic apparatus is provided. The apparatus includes a water-level sensor that senses a water-level of water generated at an anode side of a fuel cell stack and stored in a water trap and a drain valve for the drain control of the generated water. A drain valve position sensor senses a position of the drain valve. A controller detects a failure situation by performing failure diagnosis based on the sensing information generated from the water-level sensor and the drain valve position sensor, and performs a corresponding control depending upon the failure situation.

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.

A method of diagnosing level sensor failure in a fuel cell water trap, the method may include: determining whether a water level of a level sensor is changed in a fuel cell water trap, adding an amount of charge according to an operating time and comparing the added amount of charge with a preset threshold amount of charge, according to the result of the forcibly opening a drain valve according to determining whether a channel voltage of a specific channel is abnormal as the result of the comparison, and diagnosing a failure of the level sensor according to determining whether the channel voltage of the specific cell is recovered as a normal state when the drain valve is opened.

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 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.

Various systems and methods disclosed herein may include a fuel cell system that may dynamically respond to changes in steam concentration in the fuel cell system. The fuel cell system may include a fuel cell stack that produces an anode exhaust stream, an anode recycle blower that receives the anode exhaust stream and outputs an anode recycle stream, and a humidity sensor configured to measure the steam concentration of the anode recycle stream. The fuel cell system may also include a master controller configured to receive steam concentration measurement from the humidity sensor and control the operation of the anode recycle blower and/or other components based on the steam concentration measurement.

A fuel cell system includes: a fuel cell that generates electricity using a fuel gas and an oxidant gas; a fuel gas supply path through which a fuel gas to be supplied to an anode of the fuel cell flows; a recycle gas path through which an anode off-gas emitted from the anode of the fuel cell is returned to the fuel gas supply path; a water reservoir that holds water separated from the anode off-gas flowing through the recycle gas path; a drainage path through which water stored in the water reservoir is drained; a valve provided on the drainage path; and a controller that determines, on the basis of a history of a flow rate of the anode off-gas, a length of time for which the valve continues to be opened for draining the water stored in the water reservoir.

A fuel cell system comprises a fuel cell, coolant, a gas-liquid separator, a gas-liquid discharge valve, and a controller. The controller includes an exhaust speed acquisition unit configured to obtain an exhaust speed A of anode off gas discharged from the gas-liquid discharge valve, a threshold speed setting unit configured to set an exhaust speed B, serving as a threshold speed, based on an exhaust speed A1 obtained in a warmed-up state in which temperature of the coolant is equal to or higher than predetermined temperature, and a gas-liquid discharge valve normality determination unit configured to compare an exhaust speed A2, obtained at the time after the exhaust speed B is set by the threshold speed setting unit and when environmental temperature is below zero, with the set threshold speed so as to perform a normal valve opening determination to determine whether the gas-liquid discharge valve opens normally.

The invention relates to a method of determining water accumulation in and or removal from a fuel cell, the method comprising circulating fuel gas in the anode side of the fuel cell for producing electric energy in a fuel cell process, providing at least two purge pulses from the fuel circulation, analyzing the composition and/or volume of purged gas of said at least two gas purge pulses for determining the amount of water accumulation in and/or removal from the fuel cell.

A method for determining a humidity condition in a fuel cell system includes steps of: detecting an amount of water in a container that receives water discharged from a fuel cell stack, and determining a humidity condition in the fuel cell stack, based on the amount of water detected. As a result, the actual humidity condition in the fuel cell stack may be accurately determined even when humidification performance is degraded over operating time of the fuel cell system.