Experimental Analysis of Microscopic Spray Properties of Nonstabilized Water-in-Gasoline Emulsions Using Shadowgraph Imaging

This is the authors' abstract. We don't add key points for this paper.

In this study, the atomization of gasoline, water, and nonstabilized water-in-gasoline emulsions injected via a multihole gasoline direct injection (GDI) injector was investigated using shadowgraph imaging. The investigations were conducted in a single spray plume of the injector mounted in a constant-volume chamber. The parameters varied were the injection pressure, the emulsion composition, and the measurement location. The comparison of emulsions of varying composition with the neat liquids revealed unexpected behavior. The Sauter mean diameter d32 of the emulsion spray exhibited only a marginal change when the water content was increased, although water and gasoline exhibited significant differences in surface tension, and the emulsion viscosity is expected to grow exponentially with increasing water fraction. Important findings are also presented for the variation of the measurement location within the spray plume. Axially, d32 increases with increasing distance from the injector, which is attributed to ongoing secondary break-up processes. Coherent structures and ligaments disintegrate into large droplets with progressing axial distance, which then disperse radially due to jet expansion, increasing d32 globally. Radially, d32 initially decreases because larger droplets remain closer to the axis due to higher inertia, while smaller droplets disperse throughout the entire spray. This initial decrease is followed by an increase until d32 reaches its maximum at the spray edge.