Fuel composition effect on the electrostatically-driven atomization of bio-butanol containing engine fuel blends

Electrostatically assisted sprays of three fuel blends of bio-butanol, ethanol and heptane were studied experimentally. Mixture composition was selected such that electrical conductivity and surface tension were kept constant for all three mixtures. In this manner, the effect of fuel composition was investigated in a context that broadens the classical focus on the effective decrease of surface tension through the action of electrostatic fields. High-speed visualization was used in order to capture e-spray morphology. In addition, probability density functions of the e-spray droplet size and velocity were measured using Phase-Doppler Anemometry for a variety of flow rates and applied voltages. The dependence of droplet average diameter on both flow rate and applied electric field was highlighted. Polydisperse sprays were observed which was rationalized through the calculation of droplet Weber numbers that pointed to the possibility of a secondary droplet break-up.

► Sprays of alcohol-containing blends are amenable to electrostatic manipulation.
► Monodispersion is non-achievable for conditions pertaining to automotive applications.
► Electrical conductivity and surface tension do not determine fully the spray behavior.
► Non-dimensional analysis was performed to classify flow regimes for each blend.
► We numbers revealed the possibility of droplet secondary break-up.