الفهرس 
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Abstract
This thesis is aimed at analyzing electrospraying in simple -jet mode of a pesticide - solution issued from the nozzle of a capillary of the spray - system. The analysis includes the formation of a jet charged by conduction at low applied voltages (below corona onset) and by corona discharge at voltages higher than the corona-onset value. The electric field distribution in the space between the charged jet and the target is calculated at voltages below and above the corona onset value.
Mathematical modeling of electrostatic pesticide spray calls for calculating the electric field due to the applied voltage through the inter-electrode spacing between the jet and the grounded target plate to be sprayed. The jet is considered a conductive extension of the capillary. The charge simulation technique (C.S.T) is applied for calculating the electric field in the space between electrodes. The capillary and jet are simulated by a point charge located at the center of the hemispherical cap of the jet, and a set of semi-infinite line charges extending along the axis of both the jet and the capillary.
The disintegration of the jet into droplets is assessed to determine the jet length and radius as well as the charge and radius of droplets. The current-voltage characteristic of the spray system is calculated and checked experimentally. The agreement between the calculated and measured currents in the spray system at the same applied voltage is satisfactory.
The thesis is organized into six chapters.
Chapter 1 is the introductory chapter, which includes the motivation for the present study and description of thesis organization into chapters with some details on the contents of each chapter.
Chapter 2 reports a thorough review of the literature dealing with the atomization process and the most important mechanisms of charging the liquid droplets, being the first stage of the electrostatic spraying process. This is in addition to a summary of previously published work related to electrostatic spraying.
Chapter 3 presents the proposed method of analysis for electrospraying in simple -jet mode along with the experimental setup to validate the theoretical finding. The analysis includes the formation of a jet charged by conduction at low applied voltages (below corona onset voltage) and by corona discharge at voltages higher than the corona-onset value. The disintegration of the jet into droplets is assessed to determine the jet length and radius as well as the charge and radius of droplets. The electric field distribution in the space between the charged jet and the target is calculated at voltages below and above the corona onset value. The flow of the charged droplets and the corona ions is calculated to calculate the current-voltage characteristics of the jet-target gap.
Chapter 4 presents the experimental set-up and measuring technique. It introduces detailed description of the high-voltage DC power supply and the precautions made to ensure that the corona discharge takes place at the jet only. Also, the experimental techniques to measure the corona onset voltage and the current-voltage characteristics of the discharge in the jet-to-target gaps at different applied voltages are explained.
Chapter 5 presents the obtained results and their discussion to shows how the calculated electric field using the charge simulation technique influences the jet length, droplet radius, droplet charge and concentrations of droplets around jet head at applied voltages below the corona onset value and for different value of liquid flow rate and capillary to target spacing. The dependency of the calculated DC corona onset voltage in the jet-to-target gap on the liquid flow rate and gap spacing is checked against those measured experimentally.
The results include also the effect of the applied electric field on the charged droplets and the space charge including corona ions in the space between the jet and the target to be sprayed. This is in addition to the measured current – voltage characteristics of DC coronas in the jet-to-target gap for different value of flow rate and gap spacing which agree reasonably with the calculated ones.
Chapter 6 summarizes the main conclusions that can be extracted from the present work and list some recommendations for future studies.