ATOMIZATION, COMBUSTION, AND CONTROL OF CHARGED HYDROCARBON SPRAYS

Abstract

The atomization of electrically insulating liquid fuels has been investigated using the charge injection method with consideration of its usefulness as a spray combustion technique. This requires electrostatic spraying systems that atomize unadulterated commercial grades of fuel oil sufficiently finely while being able to operate robustly in the ionized combustion environment. As a natural consequence of the liquid charging mechanism, the atomization quality improves with flow rate because of the dual action of aerodynamic shear and the higher specific charge that can be achieved in the liquid jet. At moderate charging conditions, sprays of insulating liquids are similar to those of semiconducting liquids, with a core of larger drops surrounded by a sheath of much smaller companions. More highly charged sprays are more homogeneous, and stable combustion of kerosene and diesel oil has been achieved for the first time at practically useful flow rates. Flame stability improves with atomization quality and a stable flame seat is formed without the need for a pilot flame for an atomizer of 150-mm orifice diameter for a kerosene flow rate of 0.5 ml/s and a specific charge of 3.0 C/m3. Spray manipulation of both cold and combusting sprays using DC electric fields has been demonstrated, and the effectiveness of the technique suggests that optimization of the combustion process is possible by applying AC electric fields.