A fuel supply control system and method for a fuel cell are disclosed. The system includes: a fuel cell configured to receive a fuel gas and an oxidation gas and generate electric power; a recirculation line configured to circulate gas containing the fuel gas and connected to a fuel electrode of the fuel cell; a discharge valve provided in the recirculation line and configured to allow the gas to be discharged to the outside when open; a discharge amount estimator configured to estimate a discharge amount of the discharged gas based on a supply amount of the fuel gas supplied to the recirculation line, a consumption amount of the fuel gas consumed in the fuel cell, and a change in the amount of the gas in the recirculation line; an offset calculator configured to calculate the discharge amount of the gas estimated by the discharge amount estimator with the discharge valve closed, as a discharge offset; and a controller configured to control opening/closing of the discharge valve.

A fuel cell system comprises: a gas-liquid separator separating exhaust gas of a fuel cell stack into a liquid component and a gas component and storing liquid water of the liquid component; a circulation pipe; a drain pipe discharging the liquid water; and a drain valve opening and closing the drain pipe. In an end scavenging process that is executed when operation of the fuel cell system is finished, the control unit opens the drain valve when a valve opening condition for the drain valve is satisfied. The valve opening condition is set such that an amount of the liquid water stored in the gas-liquid separator at the time the drain valve is opened in the end scavenging process is larger than an amount of the liquid water stored in the gas-liquid separator at the time the drain valve is opened during normal operation of the fuel cell system.

A system for estimating the amount of purge of a fuel cell is provided. The system includes a fuel cell that generates power by receiving hydrogen at an anode side and receives oxygen at a cathode side. A recirculation line is connected with the anode side of the fuel cell, and the gas included hydrogen therein is circulated in the recirculation line. A flow amount estimator estimates the flow amount of gas inside the recirculation line. A purge valve is positioned in the recirculation line and discharges the gas in the recirculation line to the outside when opened. A purge amount estimator estimates the amount of purge for each gas discharged through the purge valve by reflecting the flow amount of the gas estimated by the flow amount estimator.

A fuel cell system includes first and second fuel cells each generating electric power using fuel gas and oxidant gas, first and second fuel gas supply devices supplying the fuel gas, first and second circulation paths circulating the discharged fuel gas to the first and second fuel cells, a communication path communicated with the first and second circulation paths, an opening/closing device causing the first and second circulation path to be communicated or to be disconnected by opening/closing the communication path, and a controller configured to determine whether there is a possibility of flooding, and when determining that there is the possibility of flooding, suspend power generation of one of the first and second fuel cells while maintaining supply of the fuel gas, and cause the opening/closing device to make the first and second circulation paths be communicated with each other.

A device for diagnosing a valve failure of a fuel cell system is capable of accurately and quickly determining whether an integrated valve in a fuel cell system is operated abnormally, and preventing problems caused by the operation abnormality of the integrated valve.

Embodiments of systems and methods of operating a vehicle include operating at least one fuel cell stack, whereupon a heat exchanger therefor the at least one fuel cell stack counter-balances heat therefrom with heat rejected therefrom, and operating a water system to pump water from the at least one fuel cell stack into a water reservoir. Moreover, in response to high water levels in the water reservoir, the embodiments include increasing electrical energy loads on at least one battery operable to store electrical energy from the at least one fuel cell stack, operating the at least one fuel cell stack for higher output, whereupon the heat exchanger under-balances heat therefrom with heat rejected therefrom, and operating the water system to apply water from the water reservoir onto the heat exchanger, whereupon the heat exchanger restoratively counter-balances heat therefrom with heat rejected therefrom.

A fuel-cell hydrogen recycling system, comprising a fuel cell; a controller; a hydrogen recycling pipeline provided with a hydrogen circulating pump and a check valve; an air inlet pipeline and an air outlet pipeline connected to the fuel cell, respectively; a hydrogen inlet pipeline provided with a hydrogen inlet valve; and a hydrogen outlet pipeline provided with a hydrogen outlet valve, with the hydrogen recycling pipeline connected to the hydrogen inlet pipeline, wherein the system further comprises a gas-liquid separating reservoir, which comprises a reservoir positioned at its upper portion and a gas-liquid separator positioned at its lower portion communicated with each other vertically, the reservoir is connected to the hydrogen outlet pipeline and the hydrogen recycling pipeline, respectively, and the gas-liquid separator discharges exhaust water and redundant nitrogen through a exhaust pipeline that is provided with a ventilation valve.

An apparatus and a method for controlling a fuel electrode drain valve of a fuel cell system are disclosed. The apparatus includes: a hydrogen sensor that measures the concentration of hydrogen released by opening a fuel electrode drain valve, a first pressure sensor that measures the inlet pressure of the fuel electrode drain valve, a second pressure sensor that measures the outlet pressure of the fuel electrode drain valve; and a controller that controls the opening area of the fuel electrode drain valve to the maximum value when draining the condensate and controls the opening area of the fuel electrode drain valve based on the difference between the inlet pressure and the outlet pressure of the fuel electrode drain valve when purging the hydrogen.

A condensate water drain control system for fuel cells includes a fuel cell stack configured to generate electric power through chemical reaction, a fuel supply line configured to recirculate fuel discharged from the fuel cell stack together with fuel introduced from a fuel supply valve, a water trap located in the fuel supply line, the water trap being configured to collect condensate water discharged from the fuel cell stack, a drain valve configured to discharge the condensate water stored in the water trap to the outside when opened, and a drain controller configured to determine whether the fuel supply valve is controlled such that pressure in the fuel supply line is maintained before the drain valve is opened and to sense discharge of fuel from the fuel supply line through the drain valve upon determining that the pressure is maintained.

A fuel cell system includes a fuel cell stack, a reaction gas supply portion, and a control unit. The control unit performs two stages of purging that are a first purging and a second purging in which the flow rate of the reaction gas is smaller than the flow rate of the reaction gas of the first purging, and provides a purging standby time between the first purging and the second purging, and in a case in which an operation mode of the fuel cell stack when power generation of the fuel cell stack is stopped is a high output mode in which an output is higher than the output of a normal mode, the control unit makes a purging time longer than the purging time of the first purging that is performed in the normal mode.