Numerical Simulation of Thermal Stress in Solid Oxide Fuel Cells with Functional Gradient Anode

doi:10.15541/jim20240117

Abstract

Abstract:

Material property differences among components of solid oxide fuel cell (SOFC) lead to excessive stresses during cell fabrication and operation, among which functional gradient material electrodes have attracted attention for their ability to reduce residual and thermal stresses in SOFC. But so far, there is rare study on SOFC with functional gradient anode using numerical simulation of thermal stress. In this study, a multi-physics field coupling model of SOFC with complete structure was established by COMSOL Multiphysics 6.0. Based on multi-physics field coupling model and numerical simulation of the residual stresses and thermal stresses in SOFC, four different distribution curves were employed to characterize the component distribution of anode materials. The results show that the tensile stress of anode can be significantly reduced by using functional gradient material during fabrication at different temperatures, especially at room temperature. Compared with non-gradient distribution, the maximum tensile stress of the anode is reduced by 47.69% before reduction and 35.74% after reduction by using quadratic curve distribution. During the operation process, the heat generated by the electrochemical reaction and the convective heat transfer of gas leads to the temperature difference between inlet and outlet, resulting in significant stress concentration at inlet and outlet of the metal frame as well as at contact surface between rib and electrode. Functional gradient materials can significantly reduce the maximum stress on the anode, metal frame and electrolyte, which is particularly obvious when using quadratic curve distribution. Therefore, this research has potential theoretical significance and engineering value for designing and fabricating SOFCs.

Key words: solid oxide fuel cell, functional gradient material, multi-physics field coupling, thermal stress

CLC Number:

TK91

XUE Dingxi, YI Bingyao, LI Guojun, MA Shuai, LIU Keqin. Numerical Simulation of Thermal Stress in Solid Oxide Fuel Cells with Functional Gradient Anode[J]. Journal of Inorganic Materials, 2024, 39(11): 1189-1196.

Figures/Tables 14

Fig. 1 Geometric model of the fuel cell

Table 1 Geometric parameters of the model

Parameter	Value/mm	Description
L×W×H	40×40×4.59	Length, width and height of the SOFC model
h_ASL	0.48	Thickness of anode support layer
h_AFL	0.02	Thickness of anode functional layer
h_EL	0.02	Thickness of electrolyte
h_CFL	0.02	Thickness of cathode functional layer
h_CCCL	0.05	Thickness of cathode current collecting layer
H_ch	1	Height of gas channel
W_ch	6	Width of gas channel

Fig. 2 Distribution functions of functional gradient materials in anode

Table 2 Material parameters of the model[10, 13-17]

Material	T/K	E/MPa	$\nu $	$\alpha $/(×10^–6, K^–1).
NiO	298	220	0.32	11.70
	1073	220	0.32	14.10
Ni	298	210	0.30	12.48
	1073	171	0.30	16.90
LSM	298	41.3	0.28	11.42
	1073	48.3	0.28	12.70
8YSZ	298	206	0.31	8.37
	1073	145	0.31	10.50
Frame	298	216	0.30	10.06
	1073	92	0.30	11.87

Fig. 3 Effect of Ni volume fraction on TPB density

Fig. 4 Distribution of residual stress in electrolyte based on model

Fig. 5 Polarization curves of simulation and experiment[20]

Fig. 6 Schematic of SOFC sintering process

Fig. 7 First principal stresses of anode in different preparation processes (a) NiO-1373 K; (b) NiO-298 K; (c) Ni-1173 K; (d) Ni-298 K

Fig. 8 Maximum residual stresses in (a) anode, (b) cathode and (c) electrolyte Horizontal coordinates correspond to the sintering steps in Fig. 6

Fig. 9 Temperature distribution of the cell during operation

Fig. 10 Stress distribution in the metal frame of the cell during operation

Fig. 11 First principal stress at the anode interface along y axis

Fig. 12 Maximum residual stresses in SOFC under different gradient conditions (a) Maximum stresses in metal frame and anode; (b) Maximum stresses in cathode and electrolyte

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