Patent ID: 8026009

Claim:
A diluting mechanism for an exhaust fuel that dilutes the concentration of the exhaust fuel in a dilution chamber, where the exhaust fuel is exhausted from a fuel cell, the diluting mechanism comprising: a fuel inlet constructed to receive exhaust fuel from an anode exhaust of the fuel cell and transmit the received exhaust fuel to the dilution chamber; a diluent inlet provided for supplying a diluent to the dilution chamber; a diffusion flow path provided in the dilution chamber for mixing the exhaust fuel that is supplied from the fuel inlet with the diluent that is supplied from the diluent inlet; a fuel exhaust port for exhausting the diluted exhaust fuel out of the dilution chamber through the diffusion flow path; and a nozzle that narrows a flow path, provided at the fuel inlet, wherein the nozzle limits a supply quantity of the exhaust fuel to the dilution chamber before the exhaust fuel comes into contract with the diluent, and wherein when a diameter of the nozzle is d and a purge flow rate of the exhaust fuel that is exhausted from the fuel cell is Q, a relationship between the purge flow rate Q and the diameter d is set to meet formula: Q=πd 2 (2/(κ+1)) 1/(κ−1) ×{2/(κ+1)} 1/2 ρv/ 4 where κ is a specific heat ratio of the exhausted fuel, ρ is a density of the exhaust fuel at an upstream side of the nozzle, and v is the speed of sound.