This invention relates to drawing the oxidant into a fuel cell by means of a pump, thereby eliminating the need for an inlet manifold, and encasing the fuel cell to permit the purging of leak and effluent hydrogen from the anode.
Fuel cells are being used to provide electricity as the primary source of power for operating vehicles. Typically, polymer electrolyte membrane (PEM) fuel cells are used in vehicles. However, for efficient passenger vehicles, the spatial power density is important. Any leakage of fuel reactant can impair the environment within the vehicle and threaten the safety of passengers.
In commonly owned U.S. patent application Ser. No. 09/265,139, filed Mar. 8, 1999, a fuel cell stack has blowers at the exhaust of the oxidant flow fields to draw air into the air inlet manifold and through the oxidant flow fields of the stack. Valves allow recycling a portion of the oxygen-depleted air through a recycling channel to the air inlet manifold. The recycling channel encompasses the area external of the fuel manifolds so the recycling air flow will sweep any gas leaking through the fuel manifold seals back to the air inlet manifold, thence to be consumed at the cathodes of the cells. However, the re-introduction of oxygen-depleted air necessitates an increase in air utilization which in turn requires more air flow, a higher pressure drop across the oxidant flow fields, and an attendant increase in parasitic power required. The fuel cell stack of said application requires both an air inlet manifold and an air outlet manifold.
Objects of the invention include reducing the size of a fuel cell power plant, such as for use in a vehicle; providing a fuel cell power plant configured to lower a vehicle center of gravity; reducing the effects of leakage of fuel reactant in the surrounding environment and within the vehicle; combusting spent fuel and leaked fuel; combusting leaked fuel without use of oxygen-depleted air; and improved operation of a fuel cell suitable for use as the main source of power in a vehicle.
According to the present invention, the oxidant reactant gas of a fuel cell is drawn into the fuel cell by means of a pump at the reactant gas outlet, thereby eliminating the need for an oxidant reactant gas inlet manifold. According to the invention further, the fuel cell is totally encased, so that any hydrogen leaks will be mixed with air within the casing, drawn into the fresh fuel cell air supply, and consumed by catalytic reaction on the cathode catalyst of the fuel cell. In accordance with the invention further, the fuel reactant exhaust, or venting from fuel recycling apparatus, may be vented directly into the case, so that all of the unspent fuel will mix with the incoming air and be consumed by catalytic reaction on the cathode catalyst. Or, the unspent fuel exhaust, or venting from fuel recycling apparatus, may be diluted with the oxidant exhaust before venting to the atmosphere.
The invention reduces the size of a fuel cell suitable for use in an electric automobile, and reduces the concentration of or eliminates unspent fuel vented into the environment, and eliminates hydrogen leaks into the vehicle. The invention allows a low center of gravity configuration for a vehicle.
Other objects, features and advantages of the present invention will become more apparent in the light of the following detailed description of exemplary embodiments thereof, as illustrated in the accompanying drawing.