عنوان مقاله [English]
The sprays produced by an induction two-fluid nozzle are utilized to study the attraction and deposition patterns of charged liquid droplets on earthed metal targets. The targets used have different geometries, including rectangular, triangular and circular flat plates, in addition to two spherical metal objects. The flat targets have adapted to study the interactive role of sharp corner points and edges on a target, while the spherical targets mainly possess smooth surfaces without any geometrical discontinuity. It is theoretically shown that the spray relative deposition on a target is proportional to the ratio of the target induced current to the spray electric current. This finding has led to the design of an experimental setup capable of measuring the aforementioned electric currents simultaneously with variations in the nozzle characteristic parameters, and is also employed to investigate the attraction and deposition phenomena in the target proximity. The experimental setup used to have a two-fluid nozzle operation, also consisting of three major parts, including compressed air, liquid feed and high voltage lines, which also provided a basis for the control and monitoring of the running parameters. The results show that although the vertical distance between the spray and the targets has no effect on the nozzle hydraulic performance, a decrease in the distance relatively improves the spray charging efficiency, further to inducing a higher rate of electric charge on a target surface. The target geometry, in addition to enhancing the spray charging, has a significant effect on the target induced current when there are sharp points and edges on the target surface. This role confirms the creation of an intense electric field in the target proximity, which induces a higher rate of electric charge on the target surface, in addition to moderately affecting the spray charging mechanism upstream within the nozzle. The pictures taken of the charged sprays clearly show an attractive pattern of charged drops established in the vicinity of a target, demonstrating the creation of a wrap around feature, whereas the uncharged sprays have no interaction with the target. This pattern also approves the dominance of the attractive electric force field on the spray aerodynamic driving force within the target vicinity, illustrating the advantageous role of charged sprays over uncharged sprays where the spray deposition enhancement is a main goal.