Application of similarity theory in modeling the output characteristics of proton exchange membrane fuel cell

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

“…In this section, numerical simulations for two scenarios are conducted to validate the correctness of the projection diagram. Readers may refer to our previous study 29 for more details about the governing equations, source terms, boundary conditions, parameters, and validation of the numerical model. In the two scenarios, the activation criteria of the projection polarization curves take 2.0 and 4/3 times compared with the original dimensionless polarization curve, respectively.…”

“…The similarity criteria shown in eqs 1 – 3 and 8 are derived from the closed partial differential equations and boundary conditions governing PEMFC multi-physics process. 29 The voltage boundary condition is standardized as one while the normalization voltage is relative to the output voltage. 29 The dimensionless current density represents the output characteristic of the PEMFC system.…”

“… 29 The voltage boundary condition is standardized as one while the normalization voltage is relative to the output voltage. 29 The dimensionless current density represents the output characteristic of the PEMFC system. Therefore, the correlation between the output and input criteria of PEMFC can be expressed as eq 9 …”

“…However, due to the complex coupled characteristics, there are few similarity analysis studies focusing on the general correlation between the polarization curve and input parameters, which has more direct significance to PEMFC commercialization. Bai et al derived seven kinds of input criteria and proposed a dimensionless polarization curve based on a basic multi-physics coupled mathematical model, the three-dimensional single-phase isothermal model, using similarity analysis. Among the input criteria, four criteria relative to the activation loss (eq ), ohmic loss (eq ), diffusion mass transfer loss (eq ), and convection mass transfer loss (eq ) are of significance to the dimensionless polarization curve, and the dimensionless voltage and dimensionless current density output criteria are shown in eqs and , respectively. A c t = R T α italicnF η normalt O h m = H normalO normal2 A normals J 0 , normalC ρ normalO normal2 L normalt 2 M normalO c normalc , ref normalm σ η normalt where η t (V) is the total overpotential calculated by subtracting output cell voltage from the open circuit voltage V oc .…”

“…Above all, revealing the effect of the activation criterion on the polarization curve in detail is one of the major challenges for further general correlation investigation between the output and input criteria in PEMFCs. In this study, a projection diagram is proposed to predict the polarization curve under variation of activation criterion based on the criteria in eqs 1 – 4 , 6 , and 7 , 29 partially resolving the above-referred general correlation investigation issue. The rest of this paper is organized as follows.…”