Effect of strengthened road vibration on performance degradation of PEM fuel cell stack

• Improved long-term strengthened road vibration test of fuel cell stack is conducted.
• A fluctuating variation of polarization curves with a downward trend is observed.
• The performance of individual cell voltage uniformity becomes worse distinctly.
• The ohmic resistance obtained through AC impedance diagnosis increases by 5.36%.
• Rises of ohmic resistance and mass transfer loss are main causes of voltage decay.

The vehicular fuel cell stack is unavoidably impacted by the vibration and shock in the real-world due to the road unevenness. However, influences of vibration on fuel cell stack have yet to be investigated completely. In this paper, the performance of a fuel cell stack is experimentally studied in terms of gas-tightness, voltage degradation, AC impedance spectra, polarization curve and characteristic parameters in polarization curve through long-term strengthened road vibration tests, in order to investigate the influences of road-induced vibration on performance degradation of fuel cell stack. The vibration tests are carried out on a six-channel multi axial simulation table with the vibration excitation spectra originally derived from the strengthened road of the ground prove. During the vibration test, several kinds of performance test including gas-tightness test, AC impedance diagnosis and polarization curve test are conducted at regular intervals. After the vibration test, the gas leakage rate of anode reaches 1.73 times of the initial value. The open circuit voltage and rated voltage decreases by 0.90% and 3.58%, respectively. Meanwhile, the performance of individual cell voltage uniformity becomes worse distinctly. With the increase of vibration duration, the ohmic resistance obtained from AC impedance diagnosis ascends approximately linearly and presents a growth of 5.36% ultimately. An improved empirical fuel cell polarization curve model is adopted to fit the current–voltage data and estimate the characteristic parameters which decide the shape of polarization curve. It is noted that the limiting current density declines distinctly and the mass transfer loss increases mainly at the range of high current densities. The results indicate that the long-term strengthened road vibration condition exerts a significant influence on the durability of fuel cell stack.