Electrohydrodynamic atomization two-phase flow regime map for liquid hydrocarbon under pulsed electric fields with co-gas flow

The electrohydrodynamic atomization (EHDA) process has been used in various industrial processes, usually with a dc voltage applied to the electrodes or with induction charging by dc high voltage downstream of atomization nozzles. A pulsed high voltage has also been applied to the EHDA electrode in a liquid–liquid system in order to achieve spark free EHDA. EHDA in confined spaces often requires a co-current gas flow and liquid droplet flow. EHDA in a gas–liquid two-phase system, under applied pulse high voltages with a co-current gas flow, was considered experimentally in this investigation. A two-phase flow regime map was presented for decane and diesel fuel as the working liquids. The pulse high voltage was applied using an ignition-coil type pulse power supply with a hollow atomization electrode, where the charging power to the coil is provided by a 30 V dc power supply. The sheath gas flow was parallel to the liquid flow direction (co-current flow). Experiments were conducted for applied charging voltages from 0 to 25 V (with maximum pulse voltages of 0–27 kV); decane flow rates of 2, 4 and 6 mL/min; air co-current flow rates of 0.45, 2.2 and 4.4 L/min; and applied pulse repetition rates of 100–400 Hz. Experiments were also conducted for dc applied high voltages from 0 to 35 kV with decane flow rate from 2 to 6 mL/min to provide a reference. Experimental results show that droplet flow, liquid column with droplet flow, liquid column and partial atomization, and full atomization flow patterns are present. The two-phase flow regime maps for pulse operation is different from those for dc operation, and have shown a significant dependence on the frequency of the pulses or the pulse repetition rate.