Effects of fuel velocity in anode channel on power generation property of tubular solid oxide fuel cells using LaGaO₃ electrolyte film

The power generation properties of a solid oxide fuel cell (SOFC) were studied for various fuel velocities in the anode channel of a tubular solid oxide fuel cell. In order to achieve high power density at low temperatures, a tubular structure and LaGaO₃-based oxide thin film electrolyte on an anode substrate were adopted. It was found that the tubular SOFC showed a higher voltage at the fuel inlet side with higher fuel velocities. The fuel velocity was increased by inserting a cylindrical-shaped inner rod into the tubular cell. The cell potential was increased from 0.815 to 0.867 V when the rod was inserted at 0.2 A/cm² with a fuel utilization (U_f) of 70%. The impedance analysis suggested that the ohmic loss and diffusion overpotential decreased with increasing fuel velocity. Moreover, the effects of fuel velocity on the current distribution were analyzed by numerical simulation using the "FLUENT" code. The results indicated that the current density at the fuel inlet part increased as the fuel velocity became higher; thus, the current density distribution was dependent on fuel velocity. Higher fuel velocity seems to be effective in removing the water generated in the anode pores in the substrate due to its high fluid shear force. Hence, the hydrogen was easily diffused to the three-phase boundary at the fuel inlet part resulting in the improved current density.