ID 195

High speed microscopic imaging in the near-field of electrified biodiesel sprays

 

Abstract:

Charge injection atomization is a method of spray generation that has been tested in the past using electrically insulating liquids such as Diesel and vegetable oils. While the effect of inter-electrode geometry and hydrodynamic conditions on the overall spray structure and downstream droplet size has been studied by a number of groups, quantitative statistical descriptions of the near-field atomization zone in the context of the governing dimensionless groups is lacking in the literature. This paper presents high speed microscopic imaging of the near-field atomization zone of electrified fatty acid methyl ester fuels. An optically accessible plane electrode charge injection atomizer with an orifice diameter of 250um is used for the studies. As with previous work in highly viscous fuels, an electrospinning effect is noted at higher viscosities. Using high speed microscopic backlight imaging and in-house time-resolved image processing analysis, relationships between ligament size, liquid fragment volume, and the spray specific charge as a function of fuel properties are presented. Time dependent fluctuations in the primary break-up location are also analysed in the context of the liquid jet Reynolds number, electric Reynolds number and electrical Rayleigh number. The contribution demonstrates new quantitative insights into the primary atomization zone of electrified sprays.