Liquid fuel aerosols with submicron droplets

We describe a methodology for producing aerosols of submicron-sized droplets for liquid fuels. The method of droplet formation is based on disintegration, by gas jets, of thin liquid films formed as bubbles on a liquid surface. Using compressed air and CO2, we atomized gasoline (95 RON), diesel, and 0.1-2 wt.% aqueous solutions of sodium alginate with dynamic viscosities up to 210 mPa·s as a model of a highly viscous fuel. The observed droplet volume distributions were bi-modal with two peaks between the droplet diameters 0.1-1 µm and 1-10 µm, and the respective volume and Sauter mean droplet diameters were substantially smaller than typically produced by other atomization methods. For most of the studied cases, 99% of droplets in the aerosols by number were smaller than 1 µm, and the arithmetic mean diameters were ~200 nm. The liquid flow rates were measured between a few hundreds of mg/min (for 2 wt.% sodium alginate solution) and O(10) g/min (for gasoline). The minimum air-to-liquid mass ratio was smaller (for gasoline) and near (for diesel) than the respective stoichiometric air-fuel ratios. Finally, we established the empirical dependence of the droplet diameter on the dimensionless number relating between the four process-governing forces: atomizing gas pressure, droplet inertia, and liquid viscosity and surface tension.