The effect of fuel gas mixtures and air flow rates on electrical properties of solid oxide fuel cell

Fuel Cells are one of the most efficient and environmentally friendly devices for electricity generation, which are developing rapidly and are already in the early stages of commercialization. Solid Oxide Fuel Cells (SOFC) areone of the most promising their types due to the highest efficiency, fuel flexibility (H2, CnHm, CO etc.) and no needs in platinum group catalysts. The performance of SOFC is affected by various polarization losses, which aredependant on selected materials, their structure and SOFC operation parameters. Over the last decade, much attention is given to the study of SOFC’s electrochemical properties at different operating regimes: temperatures, fuels, fuel and oxidantflow rates etc. The work is devoted to studying the influence of the model fuel (5% H2—Ar) and air (oxidant) flow rates on electrical properties of Solid Oxide Fuel Cellat 800 °C to determine the best combination of gas flow rates, which provide the maximum values of specific electric power. The fuel (0,35 l/min) and oxidant (1 l/min)flow rates was found as the optimal operation regime of fuel and air supply for the SOFC tested. The highest electrical densityto be ensured by the model fuel was determined as 34 mW/cm2. The amount / flow rate of oxidant and fuel gases supplied to the fuel cell does not correspond to the ratio of the reagents of the chemical reaction of oxidation of the fuel. This difference is explained by the fact that the SOFC effectiveness of fuel and oxidant utilization depends not only from to the properties structure and materials of each components: anode, cathode, electrolyte, but also from concentration of fuel and oxidant in model fuel or air, which also creates a barrier for oxidant and fuel molecules to reach the reaction zone. Keywords: Solid Oxide Fuel Cell, electrical properties, fuelgasmixtures, hydrogen, oxidant.

SUPERFACT: A Model Fuel for Studying the Evolution of the Microstructure of Spent Nuclear Fuel during Storage/Disposal

The transmutation of minor actinides (in particular, Np and Am), which are among the main contributors to spent fuel α-radiotoxicity, was studied in the SUPERFACT irradiation. Several types of transmutation UO2-based fuels were produced, differing by their minor actinide content (241Am, 237Np, Pu), and irradiated in the Phénix fast reactor. Due to the high content in rather short-lived alpha-decaying actinides, both the archive, but also the irradiated fuels, cumulated an alpha dose during a laboratory time scale, which is comparable to that of standard LWR fuels during centuries/millenaries of storage. Transmission Electron Microscopy was performed to assess the evolution of the microstructure of the SUPERFACT archive and irradiated fuel. This was compared to conventional irradiated spent fuel (i.e., after years of storage) and to other 238Pu-doped UO2 for which the equivalent storage time would span over centuries. It could be shown that the microstructure of these fluorites does not degrade significantly from low to very high alpha-damage doses, and that helium bubbles precipitate.

Estimation of the turbulent Schmidt number in a model gas turbine combustor

This article presents the estimation of turbulent Schmidt number in a model gas turbine combustor. Different gases are used as the model fuel while maintaining the mass flow rate. The simplest closure models for Reynolds stress and turbulent flux are considered. The anisotropy of turbulent viscosity is demonstrated.