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Proton Exchange Membrane (PEM) Fuel Cell (FC) presents itself as a promising technology in view of zero-tailpipe emission vehicles. In addition, the constant development of renewable energy sources will lead to an increase in green hydrogen availability, and thus completely eliminate emissions for devices that use H2 as an energy vector. However, PEM FCs are still far from being fully developed as a technology: thermal and water management are the main issues that researchers are studying through experiments and Computational Fluid Dynamics (CFD) simulations. For the numerical approach, H2O removal models often consider a simplified flat surface, but the microgeometry of the Gas Diffusion Layer (GDL) has a leading role in determining the critical dimension for droplet detachment and how much resistance the surface poses to water sliding. The aim of this paper is to investigate the influence of droplets number on a GDL.

In this work, a new tool is proposed and tested to investigate the early phase of spark ignition (SI) processes. The diagnostic tool is based on Spark-Induced Breakdown Spectroscopy (SIBS), a consolidated technique in which the plasma formed by spark generation between two electrodes is used as the excitation source for optical emission spectroscopy (OES). The spark discharge of a commercial ignition system was analyzed through OES to correlate the characteristic evolution of the discharge with the formation of reactive species inside the activated volume. Specifically, an open-source spectrum simulation program (Lifbase) together with the NIST database was used for defining relations between the ultraviolet emission bands of nitrogen first negative system (FNS_N2) in the glow phase for different plasma temperature and pressure values.

It is well known that ethanol can be used in spark-ignition (SI) engines as a pure fuel or blended with gasoline. High enthalpy of vaporization of alcohols can affect air-fuel mixture formation prior to ignition and may form thicker liquid films around the intake valves, on the cylinder wall and piston crown. These liquid films can result in mixture non-homogeneities inside the combustion chamber and hence strongly influence the cyclic variability of early combustion stages. Starting from these considerations, the paper reports an experimental study of the initial phases of the combustion process in a single cylinder SI engine fueled with commercial gasoline and anhydrous ethanol, as well as their blend (50%vol alcohol). The engine was optically accessible and equipped with the cylinder head of a commercial power unit for two-wheel applications, with the same geometrical specifications (bore, stroke, compression ratio).