An accurate low order model (mean value model) that captures main water transport mechanisms through the components of a PEM fuel cell was developed. Fast simulation time was achieved through a lumped approach in modeling the space-dependent phenomena. Evaporation and capillarity were assumed to be the predominant mechanisms of water flow through the gas diffusion media. The innovative features of the model are not only to simulate the water transport inside the porous media with relative simplicity, but also to simulate the water transport at the interface between the gas diffusion layer and gas flow channel. In order to preserve a light computational burden, the complex air flow-droplet interaction was modeled with several simplifying assumptions, and with the support of measured data. The physics that characterizes the single droplet-air flow interaction was analyzed with an experimental apparatus constructed to study the droplet growth and detachment process. Furthermore, the experimental findings were exploited to feed the numerical model with the missing theoretical information, and empirical submodels to guarantee accuracy. Thanks to the followed fast computational time of the mean value approach, the model is suitable for fuel cell design and optimization, as well as diagnosis and control strategies development studies.

This paper incorporates a methanol reformer model with a proton exchange membrane (PEM) fuel cell system model for automotive applications. The reformer model and fuel cell system model have been integrated into a vehicle performance simulator that determines fuel economy and other performance features. Fuel cell vehicle fuel economy using on-board methanol reforming is compared with fuel economy using direct-hydrogen fueling. The overall performance using reforming is significantly less than in a direct-hydrogen fuel cell vehicle.

This paper describes a proton exchange membrane (PEM) fuel cell system model for automotive applications that includes an air compressor, cooling system, and other auxiliaries. The fuel cell system model has been integrated into a vehicle performance simulator that determines fuel economy and allows consideration of control strategies. Significant fuel cell system efficiency improvements may be possible through control of the air compressor and other auxiliaries. Fuel cell system efficiency results are presented for two limiting air compressor cases: ideal control and no control. Extension of the present analysis to hybrid configurations consisting of a fuel cell system and battery is currently under study.

The work described in this paper focuses on experiments to quantify the initial fuel mixing and gross fuel distribution in the cylinder during the intake stroke and its relationship to the large-scale convective flow field. The experiments were carried out in a water analog engine simulation rig, and, hence, limited to the intake stroke. The same engine head configuration was used for the three-dimensional PTV flow field and the PLIF fuel concentration measurements. High-speed CCD cameras were used to record the time evolution of the dye convection and mixing with a 1/4 deg of crank angle resolution (and were also used for the three-dimensional PTV measurements). The captured sequences of images were digitally processed to correct for background light non-uniformity and other spurious effects. The results are finely resolved evolution of the dye concentration maps in the center tumble plane. The three-dimensional PTV measurements show that the flow is characterized by a strong tumble, as well as pairs of cross-tumble, counter-rotating eddies. The results clearly show the advection of a fuel-rich zone along the wall opposite to the intake valves and later along the piston crown. It also shows that strong out-of-plane motions further contribute to the cross-stream mixing to result in a relatively uniform concentration at BDC, albeit slightly stratified by the lean fluid entering the cylinder later in the intake stroke. In addition to obtaining phase-averaged concentration maps at various crank angles throughout the intake stroke, the same data set is processed for a large number of cycle to extract spatial statistics of the cycle-to-cycle variability and spatial non-uniformity of the concentration maps. The combination of the three-dimensional PTV and PLIF measurements provides a very detailed understanding of the advective mixing properties of the intake-generated flow field. [S0742-4795(00)00103-4]