1. A fuel cell system comprising:
a fuel cell having an anode and a cathode, said cathode and said anode each having a flow path with an inflow and an outflow,
a gas source containing oxygen connected to said inflow of said cathode flow path,
a gas fuel source connected to said inflow of said anode flow path,
a control circuit operable upon shutdown of the fuel cell which increases the electrical load electrically connected between the anode and cathode by an amount sufficient to reduce the stoichiometric ratio of the oxygen to the fuel at the cathode to not more than one,
said control circuit thereafter operating a purge valve to flow the oxygen depleted cathode exhaust through the anode flow path.
2. The fuel cell as defined in claim 1 wherein said means for reducing the stoichiometric ratio comprises means for reducing gas flow through said cathode flow path.
3. The fuel cell as defined in claim 1 wherein said means for reducing the stoichiometric ratio comprises means for increasing the current load on the fuel cell.
4. The fuel cell as defined in claim 1 and comprising means for terminating gas fuel flow to said anode flow path upon fuel cell shutdown.
5. The fuel cell as defined in claim 4 wherein said means for terminating gas fuel flow to said anode flow path comprises a gas valve.
6. A method for shutting down a fuel cell of the type having an anode with an anode flow path connected to a source of fuel, a cathode with a cathode flow path connected to a gas source containing oxygen comprising the steps of:
reducing the stoichiometric ratio of the oxygen to the fuel at the cathode to less than or equal to one by increasing the electric load electrically connected between the anode and cathode to thereby deplete oxygen from a gas outflow from the cathode,
terminating gas fuel flow to the anode, and
fluidly connecting the oxygen depleted airflow from the cathode to the anode flow path to thereby purge the anode of fuel.
7. The method as defined in claim 6 wherein said reducing step comprises the step of reducing gas flow to the cathode flow path.
8. The method as defined in claim 6 wherein said reducing step comprises the step of increasing the electrical load on the fuel cell.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1-8. (canceled)
9. An axial flow machine comprising:
an asymmetrical air inlet; and
a compressor downstream from the asymmetrical air inlet, the compressor having an inlet guide baffle composed of guide vanes, at least some of the guide vanes of the inlet guide baffle having a vane profile andor an angle of attack deviating from other remaining guide vanes, a constant outflow angle being produced over an entire periphery by the inlet guide baffle.
10. The axial flow machine as recited in claim 9 wherein some or a plurality of further guide baffles downstream from the inlet guide baffle have at least some guide vanes having a vane profile andor an angle of attack deviating from the remaining guide vanes.
11. The axial flow machine as recited in claim 9 wherein individual guide vane groups formed by the at least some of the guide vanes have the vane profile andor angles of attack deviating from the other remaining guide vanes.
12. The axial flow machine as recited in claim 11 wherein the guide vanes of the inlet guide vane groups have vane profiles andor angles of attack that deviate from one another.
13. The axial flow machine as recited in claim 9 wherein all of the guide vanes are differently profiled andor have a different angle of attack.
14. The axial flow machine as recited in claim 9 wherein at least some of the guide vanes have an adjustable design.
15. The axial flow machine as recited in claim 9 wherein at least some of the guide vanes are formed on the inlet side of a fixed component and, on the outlet side, of a pivotable component.
16. The axial flow machine as recited in claim 14 further comprising one individual controller for some or all of the guide vanes having the adjustable design.
17. The axial flow machine as recited in claim 15 further comprising one individual controller for some or all of the guide vanes having the pivotable component.
18. An axial flow machine comprising:
an asymmetrical air inlet; and
a compressor downstream from the asymmetrical air inlet, the compressor having an inlet guide baffle composed of guide vanes, at least some of the guide vanes of the inlet guide baffle having a vane profile andor an angle of attack deviating from other remaining guide vanes to provide a more constant outflow angle over an entire periphery by the inlet guide baffle, the more constant outflow angle containing residual assymetries; and
the compressor further including a further guide baffle downstream from the inlet guide baffle, the further guide baffle having at least some guide vanes having a vane profile andor an angle of attack deviating from the remaining guide vanes of the further guide baffle to compensate for the residual assymetries.