| Proton exchange membrane fuel cell (PEMFC) was composed of the whole fluorine sulfonic acid membrane for electrolyte solid polymer, the high load amount Pt was the electric catalyst, and diffusion layer was formed in porous structure. The PFMFC in the course of operating the membrane will not conduct unless in the wetting state, so need to humidify for cell and increased membrane wetly. This text designed one cathode flow field, it comprised increased humidify channel. Water can vaporized from channel to diffusion layer, then through catalyst layer to humidifying the membrane. By combined the test data of the single cell and CFD (Computer Fluid Dynamics) software Fluent 6.0 mathematics simulation together, and analyzed the operation condition of the cell and the form of flow field impacted on performance of the cell. Utilized fuel cell module of fluent software went on research the cathode flow field which has increased humidify channel humidifying mechanism, At the same time, some of conclusions had been summarized as following:(1) The active area of PEMFC was 25 cm~2. Anode flow field and cathode flow field was single serpentine flow field. The operation pressures of the hydrogen and air were the atmosphere, working temperature was among 40 degrees Centigrade— 70 degrees Centigrade; The flow of hydrogen was 300sccm, and air discharge range was under 500sccm-2000sccm. Saturation humidifying terms rise working temperature can reduce to resistance and raise the performance of the cell. Under not reached the saturation humidifying condition, temperature raised can made the resistance of membrane increased, will not increased the performance of the cell. While adopting the air as the oxidant, the performance of the cell rises as the air flux increases, air stoichiometric flow ratio can't be smaller than 3 coefficient. Improved anode humidifying terms and cathode humidifying terms can raise cell performance, but changed anode than cathode it took heavy to influence.(2) Anode flow field being single serpentine flow field, cathode flow field as some form pin flow field, single serpentine flow field and multi serpentine flow field. Active area of PEMFC was 25cm~2;working temperature was 40 degrees Centigrade. The flow of hydrogen was 300sccm, and the flow of air was 1500sccm. Anode and cathode were saturation humidifying terms. When current density was 600mA/cm~2,the min O2 concentration increased 1.5% and max H2O concentration decreased 1.5% at the catalyst-GDL interface and the gas velocity at the middle of GDL was improved. Single cell test result showed that the voltage of this three flow fields increased 5%.(3) Anode flow field being multi serpentine flow field, cathode flow field was multi serpentine flow field which comprised increased humidify channel, The big channel of cathode flow field entered dry air , little channel entered liquid water which increased wet can keep cell run steadily. When current density was 600mA/cm2, the voltage of cell fluctuated between 0.50V~0.55V and resistance was among 0.060 ohom-cm2~0.065 ohom-cm2. Calculated simulation got cathode catalyst layer water distribute, increased wet channel corresponding catalyst layer range water concentration more than 0.85, water concentration of other parts is about 0.155. Increased wet channel can offer enough humidifying to the cathode. But we can get the O2 concentration distributed at the cathode catalyst layer and electric current density distributed at the middle of membrane, Cathode catalyst layers of whole regional oxygen distributed at gas channel corresponding range mainly, increased wet channel and spine corresponding catalysis layers of some oxygen contention zero basically, increased humidify channel and spine corresponding membrane electric current density zero basically too, the cell lost nearly half the active areas. Cathode flow filed adopted flow field comprised increase wet channel will sacrifice cell effective area while realizing humidifying. Result to reduce the operational efficiency of the whole cell. |
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