Projection Diagram for Determining Polarization Curves under Variation of Activation Criterion Using Similarity Theory.

Revealing the correlation between polarization curve and input parameters is a highly concerned topic in proton exchange membrane fuel cell (PEMFC) research. Till now, three-dimensional (3D) numerical models have been the most comprehensive methods to predict the polarization curve under variational conditions. However, due to the diversity and complexity of the parameters involved, an immense numerical or experimental burden is required to obtain the above-referred correlation based on 3D numerical model. Application of the similarity theory is considered as a promising breakthrough in PEMFC research to obtain generalized and compact laws. Activation criterion, a relative magnitude of the effect of temperature on electrochemical reaction rate versus the effect of activation overpotential, is the most important criterion on the PEMFC performance. Revealing its impact on the dimensionless polarization curve in the aspects of slope, intercept, and curvature is one of the major challenges for further investigation. Herein, a projection diagram is proposed to determine polarization curves under variation of activation criterion using similarity theory based on a series of results with other criteria variation. As a validation of the concept, two scenarios are exhibited by numerical approach. Results suggest that the maximum relative deviation of polarization curves predicted by the projection diagram is 0.14%, which reaches a high accuracy. The projection diagram reveals the reason why the activation criterion has a comprehensive and complex impact on the dimensionless polarization curve.