Experimental Investigation of the Phenomenology of AC-Driven Ethanol Electrosprays

Ethanol alternating current (AC)-manipulated electrosprays were investigated for a frequency range of 0.1-10 kHz; applied RMS voltages 3, 4, 5, and 6 kV RMS; and flowrates 5, 10, 15, 20, and 25 mL/h with the purpose of determining spray phenomenology as well as the differences with DC-manipulated e-sprays. Five dominant modes were observed, dripping, cone-jet, multijet, ramified-jet, and spindle mode, of which the ramified jet is specific to AC manipulation. The AC electrosprays demonstrated pulsating spray behavior, with hopping between modes for some cases. The conditions under which each mode appeared were determined in terms of electric bond matter and nondimensional flow rate. It was also shown that the frequency of the applied AC field could couple with the ohmic charge relaxation time in the liquid, as well as with the ionic charge injection time in a way that determined the cycling frequency of the electrosprays.