Electrostatic atomization of hydrocarbon fuels and bio-alcohols for engine applications

Electrostatically assisted sprays of butanol were established and compared with the ones of fuels of automotive interest, namely ethanol and heptane. First, electrospray phenomenology was investigated through high-speed visualization for a variety of conditions. Then, spray structure was studied through droplet size and velocity measurements, using Phase Doppler Anemometry, for a wide range of flow rates and applied voltages. Particular emphasis was placed on the determination of the dependence of droplet size and velocity on mass flow rate and applied electric field. Visualization and measurements of droplet size and speed revealed an unstable and polydisperse electrospray behavior for most conditions. Several factors were identified as responsible for this unstable behavior and were investigated experimentally for the butanol case. These included: oscillations of e-spray menisci, droplet disruption due to Coulombic fission and secondary droplet break-up because of high Weber numbers.