The analysis of interfacial thermal stresses of solid oxide fuel cell applied for submarine power

Ghassemi

Env Prog and Sustain Energy

2020

Converting chemical energy into electricity is done by an electrochemical device known as a fuel cell. Thermal stress is caused by high operating temperature, between 700 and 1,000 C, of solid oxide fuel cell (SOFC). Thermal stress is the main cause of crack initiation and crack propagation. This phenomenon may cause gas leakage, structure instability and cease operation of the SOFC before its lifetime. The aim of this study is to present a method that predicts the initiation of cracks in an anisotropic porous planar SOFC. The coupled governing nonlinear differential equations are solved numerically as for heat transfer, fluid flow, mass transfer, mass continuity, and momentum. An in-house computer code which is based on computational fluid dynamics, computational structural mechanics and extended finite element method is utilized and developed. This code, according to Darcy and Navier-Stokes thermofluid model, determines the temperature and stress distribution. The results show that the highest thermal stress occurs at the upper corners of cathode and at the lower corners of the anode. The maximum temperature occurs at the middle of the electrolyte cathode and electrolyte anode, while the maximum pressure occurs at the middle of the upper and lower section of the anode and cathode. In addition, the thickness of the cathode electrode at the left side is increased by 1.5%. Finally, the crack initiation occurs at the left side between the upper and lower corners of the cathode.

“…Substituting Equations (20) and (21) into Equation (19) gives the displacement equations in terms of Young's modulus as follows, respectively 28 :…”

Section: Navier Equationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Numerical study of detecting crack initiation in a planar solid oxide fuel cell

Ghassemi

Env Prog and Sustain Energy

2020

“…Due to the change of temperature and mismatching mechanical properties, multiple stresses exist within the cell, and delamination and transgranular fracture are the two main failure modes of the cell. Xie et al took the interfacial layer into account in their thermomechanical model. They analyzed the interfacial thermal stresses between the electrodes and the electrolyte and found that anode's interface stress level is higher than that of cathode's interface.…”

Section: Introductionmentioning

confidence: 99%

Effect of interface morphology on the residual stress distribution in solid oxide fuel cell

Cao

et al. 2020

Int J Energy Res

Summary Solid oxide fuel cell directly and efficiently converts chemical energy to electrical energy. However, the necessity for high operating temperatures can result in mechanical failure. Fuel cell is a multilayer system and its stress distribution is greatly affected by the interface morphology. In this work, cosine interfaces with different amplitudes are used to approximate the fluctuation of actual interface. The effects of interface morphology on stress state, energy release rate of crack and creep behavior have been investigated. The results show that if the interface is planar, the residual normal stress component is zero on the interface, while the nonplanarity of interface can cause the normal stress Sn and shear stress St on the interface. When the amplitude is relatively small, the max values of Sn and St on the interfaces vary linearly with increasing amplitudes in both anode and cathode. Above a certain value, nonlinearity of the interface becomes important. Max tensile Sn always occurs at the peak of convex interface, but the position of max compressive Sn varies. Max shear stress is prone to occur at 1/4 of the wavelength at small amplitude and moves towards 1/2 of the wavelength when the amplitude increases. Fracture mechanics analysis shows that the surface crack possibly penetrates into the anode function layer and then is constrained by the stiff electrolyte. On the other hand, the horizontal crack likely penetrates into the electrolyte layer when the interface is not planar. Creep analysis shows that 11 800 hours of continuous operation at high temperature cannot remove stress undulation introduced by nor‐planar interface but can make max value of Sn and St decrease around 30%.

“…If the mechanical performance of a battery pack casing cannot meet the requirements of real application, it may result in the short circuit even explosion or more severe accidents . Therefore, the mechanical performance of a battery pack casing is significant for batteries, electric vehicles, and road safety . In addition, lightweight is also considered as an objective which is necessary for less volume consumption and more extended driving range.…”

Section: Introductionmentioning

confidence: 99%

Multi‐objective optimization of lithium‐ion battery pack casing for electric vehicles: Key role of materials design and their influence

et al. 2019

The battery box is the structure that comprises the battery cells and its casing. It is designed to fix and protect the battery module. During the actual driving, there exists stress and resonance on a battery pack and its outer casing due to external vibration and shock. The safety of an electric vehicle largely depends on the mechanical characteristics of its battery pack. Besides, a lighter weight electric vehicle has a longer driving range, which makes it much more popular in vehicle market. In this paper, a comprehensive design procedure based on multi-objective optimization and experiments is applied to compare the maximum equivalent stress and resonance frequency on a battery pack casing with different materials (DC01 steel, aluminum 6061, copper C22000, and carbon nanotube [CNT]) under bumpy road, sharp turns, and sudden braking conditions to obtain the best material. Moreover, CNT is proved to be the best material considering all the performance standards. Response surface optimization design method is adopted to get an optimal design of the battery pack casing. Optimization results conclude that the maximum equivalent stress can be reduced from 3.9243 to 3.2363 MPa, and the six-order resonance frequency can be increased from 722.65 to 788.71 Hz. Experiments are carried to validate the mechanical performance of the optimal design; the deviation between the simulation and experimental results is within the tolerance.