Patent ID: 8445149

Claim:
A fuel cell system comprising: a diluting apparatus comprising: a first introducing pipe through which a fuel gas to be intermittently purged is introduced; a second introducing pipe which branches from an pipe assembly and through which an oxidizing off-gas is introduced as a diluting gas, wherein: a first portion of the oxidizing off-gas flows through the pipe assembly following a first flow path and is discharged from the pipe assembly, and a second portion of the oxidizing off-gas flows through the second introducing pipe following a second flow path; an inner space where the fuel gas is introduced from the first introducing pipe, the oxidizing off-gas is introduced from the second introducing pipe and both the fuel gas and the oxidizing off-gas are mixed and become a diluted gas; a third introducing pipe through which the diluted gas is discharged into the pipe assembly, wherein the inner space is connected to the pipe assembly via the second introducing pipe and the third introducing pipe in parallel; and a controller programmed to perform a series of calculation steps, the controller performing: a first calculation step for determining an introduced purged fuel gas quantity which is equal to a quantity of the fuel gas purged and introduced from the first introduction pipe; a second calculation step for determining a discharged fuel gas quantity which is equal to a quantity of the fuel gas to be discharged from the pipe assembly, the second calculation step comprising: determining a flow rate of the oxidizing-off gas which flows through the pipe assembly, determining a ventilation rate equal to a ratio of a quantity of a gas in the inner space that is ventilated based at least in part on the determined flow rate of the oxidizing off-gas which flows through the pipe assembly, and determining the discharged fuel gas quantity based at least in part on the determined ventilation rate; and a third calculation step for determining a current remaining fuel gas quantity in the inner space, based at least in part on the determined introduced purged fuel gas quantity and the determined discharged fuel gas quantity; wherein the controller controls at least one of a quantity of the fuel gas to be purged in a following purging operation and a timing of the following purging operation, both of which are controlled through a fuel gas purge valve based on the determined current remaining fuel gas quantity.