Low Charge Density Electrostatic Atomization

A detailed analysis of the conditions required for low charge density spray development is presented. It is shown that in addition to the requirement that spray droplet size exceed 10 ¿m, it is also necessary that a criterion which relates fluid viscosity to density and surface tension be satisfied. For typical hydrocarbon liquids, this criterion is met when the viscosity is less than about 250 mPa·s. The basic descriptive equations for low charge density spraying are derived and their implications discussed. A characteristic voltage for spray development is defined. This permits the establishment of general limits for all electrostatic spray device terminal behavior. The analysis reveals that when an electrostatic spray system enters the low charge density regime, it exhibits a behavioral pattern that is similar to a first-order phase transition. The nature and basis of this behavior are not understood and should be the subject of a future theoretical study.