Investigation On The Breakup And Dispersion Characteristics Of Charged Micro Jet In Liquid-liquid System

As a kind of renewable energy,biodiesel is a great substitute for petrochemical diesel,which has attracted wide attention in the development and application of new energy in our country.However,a large amount of nitrogen oxides are emitted when biodiesel is burned,which results in increased air pollution.Some studies have shown that emulsifying biodiesel can solve this problem.Compared with traditional mechanical stirring,ultrasonic emulsification and other technologies,electrostatic breaking and dispersing has the advantages of high efficiency,low energy consumption and strong dispersibility.It can effectively atomize the discrete phase liquid and enhance the emulsification effect.In order to prepare biodiesel emulsion with liquid-liquid electrostatic dispersion method,this paper proposes the core problem of exploring the breakup and dispersion characteristics of discrete phase liquid in continuous phase liquid.Therefore,a relevant visual experiment system was designed,and the main research is as follows:1.The pressure changes of discrete phase and continuous phase liquid under electric field disturbance was investigated,and according to the liquid-liquid interface stress balance,the relevant dispersion equation was established.By analyzing the influence of the charged voltage on the instability of the interfacial wave,the mechanism of liquid-liquid electrostatic atomization is deepened.Using high-speed camera technology,the morphology characteristics of charged water in biodiesel were observed,and three breakup modes of drop,swing drop and cone-swing jet were defined.With the increasing of charged voltage,the droplet diameter of discrete phase liquid decrease sharply at first and then change slowly.The breakup length of the discrete phase liquid jet under different working conditions grows with the increasing of flow to a peak value,and then reduces.Through the above experiments,the biodiesel emulsion was prepared under the working conditions with small particle size and strong dispersion,and it was found that the longest stable time of the emulsion can reach 33 h,which has certain application value.2.By using PIV technology,the internal flow behavior of the charged discrete phase liquid in the liquid-liquid system was explored,and the internal velocity distribution characteristics of the axisymmetric wave and non-axisymmetric wave jets were analyzed.In the drop mode,it was found that when the flow rate was increased,the double vortex circulation movement appeared in the droplet.The external electric field enhances the internal vortex strength and flow velocity of the droplet.Increasing the electric field strength can strengthen the heat and mass transfer between the liquid and liquid phases.3.Ethanol with a water content of 20% was selected as the discrete phase liquid to analyze its electrostatic breakup and dispersion behavior in biodiesel.According to the interface features of charged aqueous ethanol in biodiesel and the interface wave theory,five kinds of breakup modes were proposed,including droplet,swing droplet,mixed wave-filament,non-axisymmetric waveform-filament and non-axisymmetric waveform-membrane-filament.The evolution process of the aqueous ethanol liquid bridge and liquid filament at different moments under the action of electric field was analyzed,which reveals the behavior of the discrete phase liquid breakup in each mode.The aqueous ethanol-biodiesel emulsion prepared in laboratory is more stable than water-biodiesel emulsion made with the same operating parameters,so it is more suitable for industrial applications.