PRIMARY ATOMIZATION AND DROP SIZE CHARACTERISTICS OF AN ELECTROSTATIC DIELECTRIC LIQUID PULSED ATOMIZER

Primary atomization and drop size characteristics are presented for a fuel injector which has been modified to electrically charge dielectrics such as hydrocarbon liquids used in the transport industry. Global spray characteristics are discussed for a conventional low-pressure fuel injector with no electrostatic assistance alongside the electrostatically modified version, where the latter may also be referred to as a "fully pulsed charge injection atomizer" The atomizer is a novel device that consists of sealed high-voltage components retrofitted onto an existing fuel injector as described in Kourmatzis and Shrimpton, Journal of Electrostatics, vol. 69, pp. 157-167 (2012). Experiments conducted with continuous pulsed frequencies ranging from 1-20 Hz at average injection velocities of approximately 10 m/s up to an applied voltage of 4 kV reveal that supplying a pulsed electric charge on a pulsed flow successfully promotes primary atomization and dispersion. In addition to continuous pulsing, single voltage pulses have been applied to the fuel injector solenoid and high-voltage electrode, at pulse widths down to 5 ms. Localized jet breakup images have revealed the time taken for a small electrically charged dielectric liquid fuel packet to atomize into droplets over a range of voltages, and, as with previous work conducted for pulsed voltage steady flow systems, frequency has no measurable effect on the atomization characteristics of pulsed flow pulsed voltage systems. Particle digital image analysis was employed in order to determine the drop sizes produced by the electrostatically modified fuel injector, and, while atomization is poor at locations close to the breakup length, droplet sizes of half the orifice diameter may be achieved with only similar to 2 mW of electrical power.