Study On Atomization Of Liquid Jets In A High Voltage Electrostatic Field And Its Application

Improving the effects of liquids jets atomization with a high voltage electrostatic field is a new technology in recently years. Liquid medium can be charged by various ways after passing through the nozzle to form charged fog drops groups based on the high-voltage technique. It is widely used in electrostatic spraying, electrostatic printing, pollution research, meteorological experiment, pesticide spraying and stock of the nuclear reactor. The liquid can be micronized effectively using liquid jets technology in a high voltage electrostatic field. It can reduce the size of the fog drop; increase the uniformity and the efficiency of aggradations of the fog drops. The advantage is more and more outstanding in saving the materials, elevating the used efficiency of the liquid and reducing the environment pollution. So it is a necessary investigative new task, which has an important theoretical significance and practical application value.According to initiative researches of electrostatic atomization technology at home and abroad in this thesis, based on electrostatics theory and corona discharge mechanism, the experiments of charged liquid jets is researched and the related simulation models is established. Applying numerical solution, atomization mechanism of charged liquid jets is represented deeply in a high voltage electrostatic field from experimental study, numerical simulation and calculation, which provides an important reference for a large-scale industrial use of charged liquid jets. Atomizing spraying experiment and mathematical model in the electrostatic oiler are studied and their key technologies for increasing the effects of atomizing spraying are also essential discussed in the thesis. It is a very important significance that develops a new type of electrostatic oiler and energy-efficient electrostatic spraying equipments and extends the existing theories of high-voltage electrostatic field and jets. The main studies and creative points of the thesis are followed:①Charged mechanism and atomization procedure of liquid jets in a high voltage electrostatic field are theoretical analyzed, jet length, atomizing angle and liquid droplets particle size distribution are main factors for describing charged liquid jets. Jet area, transient area and atomization area are proposed for charged liquid jets in a high voltage electrostatic field and the movement of every area is discussed, which deepens the parenchyma for atomization of charged liquid jets. Based on electrostatics theory, charged ways of liquid droplets in a high voltage electrostatic field is discussed. At the same time, computational method of carrying capacity and theoretic critical electrical strength for breaking of liquid droplets is calculated.②Charged liquid droplets equation of motion is determined in a high-voltage electrostatic field by means of studying its stress, and its maximum theoretic velocity is deduced from the equation. According to the primary total energy principle, the theoretic mathematical model of charged liquid droplets divided is determined for dividing two or more once, which can provide the rationale as liquid droplets of liquid jets dividing more and more.③The process and phenomenon of atomization are experimental researched fully and systematically for different charged liquid jets. The equipment is self-designed and assembled in a high voltage electrostatic field. Under the same environment, atomization process for the different liquid medium of kerosene, emulsifier, alcohol and diesel oil are studied form macroscopic view (the jet length and the atomizing angle) and microscopic view (the concentration distribution and the particle size of liquid droplets). Finally, the regular pattern of atomization is summarized for different liquid jets in a high voltage electrostatic field.④According to analyzing the properties of negative corona discharge for the needle-plate electrodes, the simplified model between the nozzle and the grounded electrode is established in a high-voltage electrostatic field. Variations of the electric field intensity is analyzed in depth for absolute air dielectric and liquid dielectrics contained in air dielectric based on the finite element method of numeric computation and simulation software in an electromagnetic field. It will supply important references for getting the best effects of charged liquid jets atomization and controlling the movement of charged liquid droplets in a high-voltage electrostatic field.⑤Based on the physical model and mathematical model of charged liquid jets, the dispersion equations of inviscid liquid jets in an electrostatic field are established according to Lagrange equation under the generalized coordinate. Combining different liquid medium, the effects of electrical Euler number, electrode spacing and jet radius on axisymmetric modes and non-axisymmetric modes of charged liquid jets are studied, which reveals the essence of instability of charged liquid jets.⑥A finite difference technique is coupled with a computational fluid dynamic code to solve Poisson's equation and the Navier-Stokes equations at the electrostatic fluid-flow interface. The simulation of a two-dimensional electrified liquid jet is analyzed based on the solving method of CFD. So it will offer a significant basic theory for the research in depth of numerical simulation of charged liquid jets.⑦Spray quality is decided by oil atomization in electrostatic oiler. The main factors of atomizing quality for oil are obtained by the experiment of oil atomization in electrostatic oiler. Using MATLAB program to calculate and solve experimental data of the jet length, the atomizing angle and the oil-line interval for spraying atomization in electrostatic oiler, the regression mathematical model that reflects three results and the voltage, the distance of blade and steel plate are inductive calculated individually by making use of multiple regression method. Finally, dynamic simulation of atomizing spraying process is realized based on the established mathematical model.⑧Improvements are done based on electrostatic oiler have researched and designed according to the theory of electrostatic spraying. The charged device of oil drops in the electrostatic oiler is studied in depth. Based on combing the theory and the experiment, the key technology for improving the spray quality of electrostatic oiler is gained. It will provide crucial references for developing and manufacturing a new generation electrostatic oiler that is efficient, energy-saved and environment protected.