The Research And Application Of Charged Atomization

Based on series fundamental experiments and theoretical analyses, the charged atomization is studied systematically and comprehensively in this thesis. The research involves charge mechanism, charged atomization mechanism, atomization characteristics of two-fluid spray nozzle, charge decay and droplet breakup. On the foundation of the research, high voltage electrostatic spraying locust-killing machine is developed. The research work is supported by high and new technology industrialization project from national development and reform commission.1. Charge mechanism is studied systematically and the impact of conductivity, voltage, droplet and viscosity on the charge-mass ratio is analyzed. Base on the simulation of electrostatic field induced by needle electrode and ring electrode, a new needles and ring combined electrode is designed. By studying the electrostatic field of combined electrode and space charge of droplets, the distribution of the inductive charge on the objects surface is presented.2. An experimental system of electrostatic atomization with contacted charging method is established. The flux characteristics and atomization model with different flux and voltage are studied. The flow structure of cone-jet model, and the influencing factors of jet break length, such as conductivity, voltage and viscosity, are investigated. Cone shape and its influencing factor are analyzed theoretically by getting electrostatic stress tensor according to electrostatic theory. The result indicated that lower voltage and higher voltage would make the cone angle greater. The analysis is validated by comparing with other researcher’s picture of cone jet.3. Based on linear unsteady theory, electrostatic theory, continuity equation and Euler differential equation, mathematic model of charged jet is established. By instability analysis, the dispersion equation is obtained.4. Two new two-fluid spray nozzles with different mixing model are designed. In the one nozzle, gas and liquid mixed directly, and in the other, gas is divided into many sections first, and then mixed with liquid. The flux characteristics, atomization characteristics, droplet velocity distribution and droplet diameter distribution are researched by experiment. The result shows that two-fluid nozzle in which gas and liquid mixed directly has bigger flux adjustable range and more uniform droplet diameter. The two nozzles share the same velocity distribution characteristics. The axial velocity is fastest in axle center, and gets slower in radial direction. The radial velocity is zero in axle center, and gets faster in radial direction. These works give a deep insight on two-fluid atomization mechanism.5. The droplet breakup caused by electrostatic force, air force and interfacial force is analyzed by comprehensive study on charged droplet coulombic fission, charge decay and droplet evaporation process for the first time, and the mathematic model of charged droplet breakup is established. The research indicates that large gas-liquid relative velocity and high temperature make critical charge-mass ration of charged droplet smaller. For some liquid such as diesel, droplet diameter gets smaller during evaporation, while charge decay very slowly, and then the charge-mass ratio turns higher. Once the charge-mass ration reach the critical, droplet breaks. The simulation on charged droplet breakup in high velocity gas flow indicates that with increasing of We, bag breakup, shear breakup and explosion breakup in turn.6. A high voltage electrostatic spraying locust-killing machine is developed by integrating electrostatic atomization technology, two-fluid atomization technology and axial gas flow assisted transport technology. By the performance experiments and locust killing experiments of the machine, the best locust killing pesticide and the most economic dosage is obtained. The results show droplet diameter distribution and deposition distribution with two peaks. The best locust-killing effect of the machine can reach 93% when the flux is 1.0L/min. The successful development of high voltage electrostatic spraying locust-killing machine gives the foundation to the design and improvement of good-sized plant protecting machine.