The Investigation On Electrostatic Atomization Mechanism And Spray Characteristics Of Biodiesel

Biodiesel is now under the spotlight because of the power performance close to that of diesel and superior emission performance, whose high combustion efficiency has been concerned widely in the field of thermal machinery. Combustion efficiency and emission of pollutants are closely related with atomization quality. Atomization characteristics and flow field of spray that researchers are committed to improving, are considered to be the emphases of spray combustion. Comparing with high pressure atomization, electrostatic atomization has great advantages in improving spray characteristics and controlling flow field. Electrostatic spray combustion possesses high academic values and good prospect of application in the field of thermal machinery. New ideas for exploiting efficient combustion technology of alternative fuels and thermal mechanical would be given for researching electrostatic atomization.Theoretical analysis of charged situations for single fuel droplet under different temperature is conducted firstly and the pattern of charge to mass ratio change with time is obtained. Results indicate that the evaporation can promote the fragmentation of charged droplets, which provides the basis for the research of charged breakup mechanism of biodiesel under coupled multi-field. Deformation and motion of charged droplet for biodiesel are observed and investigated. It is concluded that the satellite droplet of biodiesel move along the axial of capillary while satellite droplet of water have additional radial motion because of the differences in conductivity. Microscopic characteristics of cone-jet are analyzed by using high-speed digital camera. Experimental results show the features of cone-jet of biodiesel, which is different with that of water. The effect of charge attenuation mechanism on spray pattern is analyzed based on charged spray of micro jet. Experiment study on charge and spray characteristics of electrostatic spray for jet flow are made by using high-speed video, microscope system and PDA. All the experimental investigation indicates the advantages of electrostatic spray in improving atomization quality and enhancing the turbulence intensity at the edge of the jet. The flow field including the velocity field, vorticity and streamline under different charged mode is measured and analyzed based on PIV. The flow field of biodiesel and water is compared and studied. Experimental results show electrostatic can alter velocity field and increase vorticity and entrainment area. These would be helpful to improving the performance of the energy exchange and enhancing the performance of heat and mass transfer, respectively. The flow field of contacted charging mode and the induction charge of ring electrode is significantly different because their charging mechanism is completely different. The research of the thesis provides references for further study of charged spray combustion.