Numerische Modellierung der thermomechanischen Fluid-Struktur-Interaktion im SOFC-Stack
Jülich / Forschungszentrum Jülich GmbH, Zentralbibliothek, Verlag (2016) [Dissertation / PhD Thesis]
Page(s): 1 Online-Ressource (iii, 165 Seiten) : Illustrationen, Diagramme
Abstract Solid oxide fuel cells (SOFC) are suitable for on-board electricity generation as Auxiliary Power Unit (APU) to support the electric power supply in heavy-duty vehicles. For these applications fuel cell stack must be made of thin-walled components in order to satisfy the requirements of a lightweight structure. This necessity is accompanied with material, process and design difficulties that must be solved in order to achieve a successful application. Due to the high operating temperatures, the com-bination of different materials in the SOFC is limited, as the Thermo-mechanical properties of the used materials must match. Thermal stresses may arise in a structure as a result of preventing its deformation. This can be caused either by mechanical constraints, or material inhomogeneity, or non-uniform temperature distribution. Also temperature-dependent material properties can induce additional spatial dependency of the mate-rial parameters due to the existence of a temperature gradient. The objective of this work is to develop a three-dimensional model for the numerical fluid dynamics and thermo-mechanical analysis of a solid oxide fuel cell stack based on computer aided simulations. The entire model consists of two discretized single models which are numerically coupled. A coupled fluid-dynamic model is used to determine the three-dimensional temperature distribution in the stack under real process conditions. The obtained temperature profiles are transmitted as a thermal load to be applied on the structural finite element model to compute the three-dimensional distribution of the stresses and deformations induced in the fuel cell stack components. Thus, the model enables the investigation of sustainability and serviceability of the structural elements to ensure a reliable opera-tion of the stack. To carry out the simulation analysis several modules of the software package AN-SYS are utilized. The model describes a two-cell stack and is suitable for predicting the thermomechanical behavior of the stack structure used in applications like on-board electric power generation. In the analysis the ge-ometric details of fuel cell stack components as well as the real physical behavior of their materials are taken into account. To describe the nonlinear temperature and time-dependent material behavior, ap-propriate mathematical material models are set up. The Model parameters are determined using ex-perimental data. The model validation is performed by comparing the computational results with the experimentally obtained data. Using the developed simulation model, detailed computational analysis can be performed in order to determine the effects of the physical material properties and to investigate the process boundary conditions and the geometrical design parameters on the induced thermal stresses. Furthermore, based on optimization analysis, the model allows the modification of the influencing parameters in order to improve the function of the SOFC-Stack and reduce the thermal stresses.