A computationally efficient model toward real-time monitoring of automotive polymer electrolyte membrane (PEM) fuel cell stacks is developed. Computational efficiency is achieved by spatio-temporal decoupling of the problem, developing a new reduced-order model for water balance across the membrane electrode assembly (MEA), and defining a new variable for cathode catalyst utilization that captures the trade-off between proton and mass transport limitations without additional computational cost. Together, these considerations result in the model calculations to be carried out more than an order of magnitude faster than real time. Moreover, a new iterative scheme allows for simulation of counter-flow operation and makes the model flexible for different flow configurations. The proposed model is validated with a wide range of experimental performance measurements from two different fuel cells. Finally, simulation case studies are presented to demonstrate the prediction capabilities of the model.

The objective of this work is to establish the design principles for a proton exchange membrane fuel cell in automotive applications. In this work, the macro-scale analysis was considered to create the overall design principle. A combination of experiments and numerical simulations were carried out and the results analyzed to enhance understanding of the behavior of the large-scale 300-cm 2 proton exchange membrane fuel cell under automotive operations. A three-dimensional computational fluid dynamicsbased methodology was used to predict such as the current and temperature distributions of this design as a function of anode relative humidity. The effect of flow direction and the cooling pattern on this design was also taken into account to enhance the understanding for this selected flow-field design. The predictions show that the gas flow and cooling directions are important dependent variables that can impact the overall performance and local distributions. As the increased number of power generators utilizing fossil fuel energy increases in many applications, the necessity for alternatives to the internal-combustion engine become even more obvious. Automakers and industrial developers are investigating many ways to significantly reduce emissions for stationary and transportation applications, Proton Exchange Membrane Fuel Cells (PEMFCs) are now widely seen as a possibility. Distributions in reactant species concentration in a PEMFC cause distributions in local current density, temperature and water over the area of a PEMFC. These can lead to locally negative effects such as excessive hydration or dehydration in the PEMFC thus causing stresses in effective regions of the fuel cell. Changing operating conditions and design parameters including their properties inside PEMFC system such as flow field configurations, gas diffusion layer (GDL), and membrane electrode assembly (MEA) could vary uniformity in distribution and impact the fuel cell performance and durability. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] The inherent non-linearity of the equations governing PEMFC performance on a three-dimensional level requires iterative solution techniques. Solving a full three-dimensional CFD model for the flow channel and diffusion layers of a PEMFC shows important interactions of porous media and flow-field design that affect distributions of current, temperature, and species transport as discussed in numerous literature for the past ten years. This type of model lends itself well to investigating the physics inside full-scale PEMFCs. 1,2,6,10,23,24 In this work, three-dimensional (3D) CFD simulations of PEMFC were performed for a full size single cell with 300 cm 2 active area. An ultimate purpose of this study was to establish a model-based engineering capability to design the PEMFC for targeted applications. For this time, robustness of the fuel cell performance was investigated with various operating conditions which can impact the water management problems in the PEMFC. 25,26 Especially, relative hu...

The morphologies of a ternary blend of nylon 66 and polystyrene in a polypropylene matrix with and without compatibilization by an ionomer resin (for nylon 66) and a styrene-block-ethylene-co-butylene-block-styrene (SEBS) copolymer (for polystyrene) were investigated by transmission electron microscopy (TEM) of stained thin sections. The morphology found with the two compatibilizers (a five-component mixture) was essentially that of the binary blends of nylon 66/polypropylene and of polystyrene/polypropylene with their respective compatibilizers, indicating no gross interference between the two compatibilization systems. However, several interactions were discerned: 1) an association of the polystyrene with the nylon in the compatibilized blends (partial wetting), 2) a presence of larger particles when both compatibilizers were added to the binary blends, and 3) a possible synergism, in which less of each compatibilizer was needed when they were both present. POLYM. ENG. SCI., 46:385-398, 2006.

The Izod impact strength and tensile elongation‐to‐break were measured for blends of nylon 66 and polystyrene in a polypropylene matrix with and without compatibilization by an ionomer resin (for nylon 66) and a styrene‐block‐ethylene‐co‐butylene‐block‐styrene copolymer (for polystyrene). With 20% nylon 66 and 20% polystyrene, about 5% of each compatibilizer was optimal. When used together for the ternary blend, there seemed to be little gross interference (or synergism) between the compatibilizers. A comparison between binary blends suggests that what interaction does exists may be synergistic. Polym. Eng. Sci. 44:1800–1809, 2004. © 2004 Society of Plastics Engineers.