THE IMPACT OF VARIOUS OXIDIZERS ON THE OVERALL PERFORMACE OF A DIRECT FLAME SOLID OXIDE FUEL CELL

Open Access
Author:
Donadio, Nicholas Mark
Graduate Program:
Mechanical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 29, 2010
Committee Members:
  • Dr Yetter, Thesis Advisor
  • Richard A Yetter, Thesis Advisor
  • Jongguen Lee, Thesis Advisor
Keywords:
  • oxidizers
  • solid oxdie fuel cell
  • direct flame
Abstract:
The power output of a direct-flame solid oxide fuel cell (SOFC) was studied using hydrogen (H2) as the fuel for the flame and various oxidizers, which included oxygen (O2), nitrous oxide (N2O), nitric oxide (NO), and nitrogen dioxide (NO2). The fuel-rich diffusion flame, which is located only a few millimeters away from the anode side of the SOFC, is used to reform the fuel and heat the SOFC. On the cathode side, an oxidizing gas is either stagnant or forced to pass over the face. The SOFC used is a 20mm diameter button cell with a Ni-based anode, a Hionic electrolyte (which is a material specially made by Fuel Cell Materials), and a strontium-doped lanthanum manganite (LSM) cathode. Experiments were conducted to study the effects of different parameters of the flame as well as the oxidizers being used. The total flame gas flow rate and the equivalence ratio (ö) were tested using two different current collecting meshes for the cathode. It was found that when using a silver mesh, which has high electric conductivity, the SOFC preformed best at the highest flow velocities (1200 SCCM) and equivalence ratios (ö), which produced a power output of 38.13 mW/cm2. The SOFC was also tested to see how an impinging oxidizer affected the SOFC performance. Pure molecular oxygen was used as the oxidizer and produced the highest power density recorded when the equivalence ratio was the highest (72.64 mW/cm2 at ö=2.0). Other nontraditional oxidizers were tested and the results showed that the molecules with the largest oxygen-nitrogen ratios produced the highest power outputs at the optimal conditions. Thus the performance increased as the oxidizer gas was changed from N2O to NO to NO2. Although NO2 produced the largest power density of the three nitrogen oxides used (63.63 mW/cm2), performance degradation was observed during prolonged use.