Substantiation of the shape of a solid oxide fuel cell anode using the stress-strain and shape-dependent crack deceleration approaches

Abstract

Stress and strain distributions in the YSZ–NiO spheroidal shape anode-substrate for a solid oxide fuel cell (SOFC) under pressure of operating environment were calculated using the finite element analysis. The features were then compared with ones of the cylindrical shape anode. The radii ranges for the cylindrical and spheroidal (segments of a sphere) parts of the anode ensuring its improved deformation resistance and more uniform stress distribution were suggested. Based on the calculations, an anode of the cylindrical shape with top and bottom convex surfaces (a spheroidal shape anode), with the spheroid to cylinder radii ratio R / Rc in the range from 5 to 20 is suggested. Itsspecific volume V / Sc isin the range from 1 to 2.5 mm. The stressesin the most dangerous areas (i. e. along the axis and the closed-loop fixing) and maximum strain, caused by external gas pressure on the anode working surface, are decreased by 10–30 % and 20–40 % respectively as compared to an anode of the cylindrical shape of the same radius and volume features. This increases the lifetime of a solid oxide fuel cell. A three-dimensional curve of intersection of the surfaces of stress distribution in the anode along its axis and the closed-loop fixing was approximated which displays the values of balanced stresses depending on V / Vc and R / Rc parameters. Also, the advantage of the spheroid shaped SOFC anode-substrate over conventional flat one was substantiated using a shape-dependent crack deceleration approach.