Finite element analysis of the containment system
The analyzed fuel cell containment system is composed by stacks of elements placed inside a casing provided with four manifolds: inlet and outlet anode side and inlet and outlet cathode side.
The anode side manifolds are anchored to the stack casing by means of fasteners installed on brackets located on the horizontal sides of each manifold. The anchoring system has the function to ensure the suitable gasket load during the whole operating cycle.
The fuel elements are kept in the proper position by a lower and an upper plate, which ensure the suitable compression load by means of a proper elastic system. The working temperatures reach such a level (above 600°C) to get the austenitic stainless steel working in the creep regime. The internal pressure are so low (of some mbar as order of magnitude) that the equipment is not subject to the requirements of the pressure equipment directive.
The state of stress has been analyzed with a set of finite element models of all structural items prepared with Ansys.
The qualification was performed checking the resulting state of stress with the requirements of the ASME Boiler and Pressure Vessel Code, either regarding the failure modes governed by the primary and secondary stresses, or regarding the creep-fatigue interaction.
The applied loads are: the temperature gradient in the horizontal direction between the inlet and outlet anode side manifolds and between the inlet and outlet cathode side manifolds; the seating loads transferred by the fasteners and by the elastic systems; the loads applied by the connected external piping .
A view of the adopted finite element models, the applied loads and the resulting stress maps are shown in the following pages:
1) Model of the anode side manifold
2) Model of the anode side cover
3) Model of the cathode side cover (see);
4) Model of the closing plates and stiffening system (see);
5) Model of the service piping (see).