Experimental Study On The Premixed Two-fluid Electrostatic Atomizer

Two-fluid electrostatic atomization is widely used in industrial and agricultural fields such as spray printing,agricultural plant protection,industrial dust removal and biofilm preparation due to its low energy consumption,high deposition rate of spray target and strong controllability.The droplet entrainment behavior is commonly observed in the charging process of conventional induction electrostatic spray nozzle.Especially in high humidity environment,the high pressure electrode surface is more likely to roll water mist and cause discharge breakdown,which is not conducive to the safe and stable operation of the spray system.It limits the popularization and application of electrostatic atomization technology in the high humidity closed environment such as desulfurization tower.Therefore,based on the theory of charged multiphase flow,a premixed air-blast electrostatic nozzle,which can effectively prevent electrode breakdown,is designed,and its spray characteristics,charge performance,fragmentation mode and flow field structure are studied.The main research work is as follows:1.A premixed air-blast electrostatic nozzle and spray system were designed by charging method of air-discharge ionization and liquid mist mixing.The nozzle electrode is arranged inside the nozzle,and has two stage mixing chamber.The charged ionic air is mixed with the broken liquid mist in the two stage mixing chamber,and the liquid is charged inside the nozzle.It avoids the problem that the electrode is exposed to the external easy roll water absorption and the discharge breakdown.It provides a technical reference for the design of the electrostatic spray system in the high humidity complex smoke environment.2.According to the designed nozzle and spray system,laser particle size analyzer and CCD camera were used to study the spray characteristics such as spray particle size and atomization cone angle.The internal flow characteristics and external characteristics were linked to study the external flow pattern corresponding to different gas-liquid ratio(GLR),and the experimental study on the charging performance was carried out.The experimental results show that the gas-liquid ratio has a significant effect on the spray characteristics.The droplet size decreases exponentially with the increase of gas-liquid ratio,and the atomization cone angle increases first and then decreases with the increase of gas-liquid ratio.With the increase of charging voltage,the charge to mass ratio of spray increases gradually,and the dispersion and spatial distribution uniformity of spray are obviously improved.The relationship between Reynolds number(Re)and dimensionless diameter is studied by dimensional analysis method.The results show that the relationship between Reynolds number and dimensionless diameter is linear.3.Considering the important factors of spray characteristics,suc h as velocity attenuation,flow field and vorticity distribution of spray flow field,the flow field of nozzle with different gas liquid ratio(GLR)and different voltage is obtained by using PIV.The flow field structure of the nozzle is analyzed,and the influence of different outlet structure of nozzle on spray flow field is compared.The results show that with the increase of gas-liquid ratio,the high velocity area of droplet group increases in the core area of spray,and extends from upstream to downstream in the spray flow field.Meanwhile,the turbulence degree of spray field increases gradually,and the spray cluster decreases gradually,and more vortices with small scale and high divergence are derived.With the increase of charging voltage,there are differences in the flow field in different regions of the spray flow field.The core area of the spray is weak with the change of voltage,but the disturbance level at the edge of the liquid bundle is more obvious,showing that the streamline becomes c haotic and produces more small scale vortices.When the outlet structure of the nozzle is flat,the spray is more coherent and has a longer penetration distance.When the outlet structure is cone groove,the atomization cone angle is larger and the turbule nce of the flow field is more intense.