A fuel cell system (100) includes a hydrogen supply valve (33) that controls a supply of the anode gas into an anode system, a purge valve (36) that discharges an off-gas from the anode system, a pressure detecting unit (34) configured to measure a pressure inside the anode system, and a purge flow rate estimating unit (4) configured to estimate a purge flow rate of the off-gas discharged from the anode system through the purge valve (36) based on a pressure decrease in a purge valve open state and a pressure decrease in a purge valve close state when an anode gas supply into the anode system stops.

A fuel cell system includes: a fuel cell generating electricity when being supplied with anode gas and cathode gas; a supply channel through which the anode gas to be supplied to the fuel cell flows; a discharge channel through which anode-off gas discharged from the fuel cell flows; a discharge valve provided on the discharge channel and opened to discharge the anode-off gas; and a control section controlling opening/closing of the discharge valve. The control section calculates a valve open time of the discharge valve corresponding to a target value of a discharge amount of the anode-off gas by using an aperture ratio of the discharge channel and the target value, and closes the discharge valve based on the valve open time, the aperture ratio of the discharge channel being calculated from a first discharge amount of the anode-off gas, which is discharged by opening of the discharge valve.

Disclosed is a method of detecting an abnormality in a first pressure sensor or a second pressure sensor of a fuel cell system including the upstream-side first pressure sensor and the downstream-side second pressure sensor provided in a fuel supply flow passage configured to connect a fuel cell and a fuel supply source, a pressure reducing valve, a first shutoff valve, and a second shutoff valve. The first shutoff valve is closed to shut off supply of fuel from the fuel supply source. a pressure on an upstream side and a pressure on a downstream side of the pressure reducing valve is decreased to he equal to or less than a pressure regulation lower limit value. The second shutoff valve is closed and detection pressure values of the first pressure sensor and the second pressure sensor are compared with each other.

A purging circuit for purging an anodic compartment of a cell of a fuel cell, this circuit including: a capacity, forming a related volume at least equal to 500 ml, for containing and homogenising a recovery gas, including an inlet and an outlet; a first nonreturn valve to prevent the recovery gas from returning through the outlet and allowing gas to flow from the first outlet to an inlet of the compartment; a second nonreturn valve to prevent gas from being discharged from the capacity through the inlet; a pressure sensor able to measure the pressure of a fluid present in the circuit; a valve controlling the flow of a supply gas to and from the compartment as a function of data of the sensor and allowing gas to flow from the first nonreturn valve to the inlet of the compartment.

When a temperature measured by a temperature measurer is below a specified temperature, a controller of a fuel cell system activates a fuel-gas-concentration increasing mechanism by using electric power of a secondary battery, and executes a fuel-gas-concentration increasing process for increasing the fuel gas concentration toward a first target concentration. When the fuel gas concentration reaches equal to or more than a second target concentration lower than the first target concentration, the controller starts power generation by a fuel cell to activate the fuel-gas-concentration increasing mechanism by using electric power from the fuel cell, and executes the fuel-gas-concentration increasing process until the fuel gas concentration reaches the first target concentration or more.

A fuel cell system includes a fuel cell, a fuel gas supply line, an oxidizing agent gas supply line, a fuel gas discharge line, and a reformer provided in the fuel gas supply line. A first circulating line circulates the fuel gas from the fuel gas discharge line to an upstream side of the reformer in the fuel gas supply line as a first circulating gas. The circulation device is provided in the fuel gas supply line, and suctions the first circulating gas by using the flow of the fuel gas flowing through the fuel gas supply line as a driving flow. A second circulating line circulates the fuel gas from a downstream side of the circulation device in the fuel gas supply line or the fuel gas discharge line to the upstream side of the circulation device in the fuel gas supply line as a second circulating gas.

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 reforming element for a molten carbonate fuel cell stack and corresponding methods are provided that can reduce or minimize temperature differences within the fuel cell stack when operating the fuel cell stack with enhanced CO.sub.2 utilization. The reforming element can include at least one surface with a reforming catalyst deposited on the surface. A difference between the minimum and maximum reforming catalyst density and/or activity on a first portion of the at least one surface can be 20% to 75%, with the highest catalyst densities and/or activities being in proximity to the side of the fuel cell stack corresponding to at least one of the anode inlet and the cathode inlet.

The invention relates to a method for checking at least two sensors within an anode path (4) of a fuel cell system (1), having the steps of shutting down the fuel cell system (1); closing the shut-off valve (32) and the purge valve (41); opening an internal valve (34); detecting the pressure values by means of at least two sensors (50, 51, 52, 53, 54) within the anode path; checking whether the pressure values of the at least two sensors (50, 51, 52, 53, 54) differ.

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.