Thermomechanical Modelling. of High Temperature Fuel Cells. 21/Sep/2012 Dr. Murat Peksen,

Transkript

1 Mitglied der Helmholtz-Gemeinschaft Thermomechanical Modelling of High Temperature Fuel Cells 21/Sep/2012 Dr. Murat Peksen, Scientific Leader, Lecturer Forschungszentrum Jülich GmbH, Germany FH Aachen, University of Applied Sciences, Germany 3D Fuel Cell System Analysis -Jülich Institute of Energy and Climate Research Electrochemical Process Engineering/SOFC Modelling

2 Thermomechanical Modelling of High Temperature Fuel Cells Syllabus Introduction What is thermomechanics? Thermomechanically induced strain and stress Thermomechanical modelling aspects Thermomechanical material properties and behaviour Geometrical approximations Thermomechanical issues in fuel cell systems Case study- Thermomechanical modelling of a solid oxide fuel cell stack. Concluding remarks Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-2

3 Thermomechanical Modelling of High Temperature Fuel Cells Introduction What is thermomechanics? Thermomechanically induced strain and stress Thermomechanical modelling aspects Thermomechanical material properties and behaviour Geometrical approximations Thermomechanical issues in fuel cell systems Case study- Thermomechanical modelling of a solid oxide fuel cell stack. Concluding remarks Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-3

4 Rivet heater and rivets Road pothole Potholes Petrol gauge Soil and railway Glaze firing Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-4

5 Thermomechanical Modelling of High Temperature Fuel Cells Introduction What is thermomechanics? Thermomechanically induced strain and stress Thermomechanical modelling aspects Thermomechanical material properties and behaviour Geometrical approximations Thermomechanical issues in fuel cell systems Case study- Thermomechanical modelling of a solid oxide fuel cell stack. Concluding remarks Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-5

6 Simple Strain-Stress Problem A brass rod is stress-free at room temperature (22 C) It is heated up, but prevented from elongation At what T does the stress reach -150MPa? Lrod Troom Heated L Strain (ε) due to T causes a stress (σ) that depends on the modulus of elasticity (E): thermal L Lo ( T To) 10 5 MPa 20 x 10-6 /C E( thermal) E ( T To ) -150MPa Constraint! L=0, stress i.e., σ occurs Answer: 97C 22C General Stress-Strain Curves for Various Materials Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-6

7 Thermomechanical Modelling of High Temperature Fuel Cells Introduction What is thermomechanics? Thermomechanically induced strain and stress Thermomechanical modelling aspects Thermomechanical material properties and behaviour Geometrical approximations Thermomechanical issues in fuel cell systems Case study- Thermomechanical modelling of a solid oxide fuel cell stack. Concluding remarks Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-7

8 Decide the target of the problem and desired output Determine the employed computer geometry Set the applied load Decide on the physics that must be included Description of the material behaviour Analysis type Solution and Post-processing-Validating Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-8

9 Thermomechanical Modelling of High Temperature Fuel Cells Introduction What is thermomechanics? Thermomechanically induced strain and stress Thermomechanical modelling aspects Thermomechanical material properties and behaviour Geometrical approximations Thermomechanical issues in fuel cell systems Case study- Thermomechanical modelling of a solid oxide fuel cell stack. Concluding remarks Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-9

10 CTE x 10 6 [ K -1 ] Cr5FeY interconnect 8YSZ electrolyte SSZ electrolyte P/M FeCr ITM alloy I/M Fe-22Cr-(Mn,Zr,La) Thermal expansion coefficient and Young s modulus of steel sample Heat capacity Thermal conductivity Young s modulus Thermal expansion coefficient Strength Temperature [ o C ] CTE of different SOFC-relevant materials Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-10

11 Linear elastic Rate independent plastic Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-11

12 Thermomechanical Modelling of High Temperature Fuel Cells Introduction What is thermomechanics? Thermomechanically induced strain and stress Thermomechanical modelling aspects Thermomechanical material properties and behaviour Geometrical approximations Thermomechanical issues in fuel cell systems Case study- Thermomechanical modelling of a solid oxide fuel cell stack. Concluding remarks Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-12

13 Simplifying the problem Geometry and Material nonlinear Geometry linear Material non-linear Geometry non-linear Material linear Complexity of the analysis Geometry and Material linear Shape Material type Support-Constraints Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-13

14 Displacement 3D approach 3D quarter Compression load test 2D approach 2D quarter CFD Solution Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-14

15 Thermomechanical Modelling of High Temperature Fuel Cells Introduction What is thermomechanics? Thermomechanically induced strain and stress Thermomechanical modelling aspects Thermomechanical material properties and behaviour Geometrical approximations Thermomechanical issues in fuel cell systems Case study- Thermomechanical modelling of a solid oxide fuel cell stack. Concluding remarks Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-15

16 Leackage and Failure!!! Manufacturing Non-uniform heat generation Internal reforming Malflow distribution Thermal cycling Flow rates; % concentrations Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-16

17 Thermomechanical Modelling of High Temperature Fuel Cells Introduction What is thermomechanics? Thermomechanically induced strain and stress Thermomechanical modelling aspects Thermomechanical material properties and behaviour Geometrical approximations Thermomechanical issues in fuel cell systems Case study- Thermomechanical modelling of a solid oxide fuel cell stack. Concluding remarks Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-17

18 Idealised Model Employed Model fuel in air out fuel in Solid body temperature! Input for structural analysis CFD analysis Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-18

19 Accurate Approximation Limited Approximation!!! Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-19

20 Mechanical Load Thermal load transfer on FEM Mesh Frictionless support Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-20

21 σmax= manifolds & Outer regions! What is the source??? Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-21

22 Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-22

23 Thermomechanical Modelling of High Temperature Fuel Cells Introduction What is thermomechanics? Thermomechanically induced strain and stress Thermomechanical modelling aspects Thermomechanical material properties and behaviour Geometrical approximations Thermomechanical issues in fuel cell systems Case study- Thermomechanical modelling of a solid oxide fuel cell stack. Concluding remarks Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-23

24 Thermomechanical Modelling of High Temperature Fuel Cells Thermomechanics is a discipline practiced to improve the quality and understanding of coupled thermal and mechanical load related issues. Fuel cell systems are a core investigation area in thermomechanics. Many well-established modelling approaches can be adopted for fuel cell structures and materials. Modelling of thermomechanics in fuel cell systems is a very challenging task due to: Complex materials and geometries (high non-linearity and sophisticated structures) Highly coupled multiphysics (requires expertise in many fields) Difficulties in testing (is very limited and prohibitive) 3D thermomechanical modelling exemplifies how intensely computer aided analysis may be applied in fuel cell systems. Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-24

25 Thermomechanical Modelling of High Temperature Fuel Cells Thank You for Your Attention! A modern vitruvian man Institut für Energie- und Klimaforschung Elektrochemische Verfahrenstechnik (IEK-3) 1-25