Quantitative analysis of trapezoid baffle block sloping angles on oxygen transport and performance of proton exchange membrane fuel cell

Increasing the power density of proton exchange membrane (PEM) fuel cell without extra cost through flow channel design is an effective method to achieve cost and compact requirement of its commercialization for vehicles. PEM fuel cell power or current density is mainly limited by oxygen transport to the reacting sites in the cathode porous electrode. Inserting baffle blocks in the flow channel of PEM fuel cell can effectively enhance the oxygen transport and fuel cell performance. However, existing researches on the structure design of baffle blocks are still insufficient, especially for the design of baffle block sloping angles. In this study, the influence of the trapezoid baffle block sloping angles on the convective and diffusive oxygen transport and performance of PEM fuel cell is quantitatively investigated using a three-dimensional numerical model. The results indicate that larger leading angle of the baffle block leads to a higher gas velocity component in the vertical direction, hence enhances the convective oxygen transport effect; but it reduces the convection area, as well as the oxygen delivery efficiency in the channel. Larger trailing angle of the baffle block induces the back-flow phenomenon at the rear of the baffle block, which causes the loss of gas pressure and worse oxygen transport. Both the baffle block sloping angles are carefully designed, and it demonstrates that the trapezoid baffle blocks with both the leading and trailing sloping angles of 45 degrees show the best oxygen transport and fuel cell performance.