Critical condition for the transformation from Taylor cone to cone-jet

An energy method is proposed to investigate the critical transformation condition from a Taylor cone to a cone-jet. Based on the kinetic theorem, the system power allocation and the electrohydrodynamics stability are discussed. The numerical results indicate that the energy of the liquid cone tip experiences a maximum value during the transformation. With the proposed jetting energy, we give the critical transformation condition under which the derivative of jetting energy with respect to the surface area is greater than or equal to the energy required to form a unit of new liquid surface.

阵列式多管集成静电雾化试验分析

为了减小甚至消除多管集成静电雾化(multiplexed electrostatic atomization,MES)中相邻毛细管荷电射流间电场的相互作用,探索和优化MES雾化特性,通过设计错位毛细管阵列来扩大喷雾源间距,并在静电场中加介质来减小射流排斥作用,改善了电场均匀性。对不同介质作用下MES的雾化特性进行了试验研究,结果表明:介质作用下MES较无介质作用下全锥射流的雾化锥角增大,产生锥射流所需的电压及形成的电流增大,液滴粒径均匀性变差,液滴空间分布变均匀;且介质绝缘性越好,雾滴粒径越小,粒径分布越均匀;介质导电性越强,粒径均匀性越差,MES稳定性越好。所以通过扩大喷雾源间距和在静电场中插入介质能有效地改善喷雾源射流周围电场的均匀性,优化MES雾化特性。

Visualization on electrified micro-jet instability from Taylor cone in electrohydrodynamic atomization

The cone-jet in electrohydrodynamic atomization has been widely applied into numerous industrial fields owing to micro-sized drops with narrow distribution and high charge.The electrified jet emits from a single capillary sheathed with quartz tube is visualized versus operating parameters and physical properties,and breakup instabilities are also discussed.The range of operating parameters for a steady conejet broadens,as well as the minimum flow rate.Taylor cone angle decreases with an increase in flow rate,while increases as electric potential increasing.The jet breakup length decreases with an increase in flow rate and conductivity,while increases as electric potential increasing.The diffusion angle increases as flow rate increasing,while decrease as electric potential and conductivity increasing.Much clearer whipping instabilities are observed with an increase in“electro-Weber”number and conductivity.The completion in disturbance or/and suppression from axial and radial stresses,drag force dominates the variation.Meanwhile,for a large flow rate,the transition from varicose instabilities to whipping instabilities is found.The whipping instabilities are clearly observed for high conductivity due to much more free ions in liquid.For much higher conductivity,an intermittent electrified jet appears and shows an umbrella plume,and breakup length sharply shortens.

Investigation of Electrostatic Atomization and Its Application for the Synthesis of Fine Ceramic Powder

In the present study,electrostatic atomization(EA)behavior of several test liquids having much higher viscosities(1 400 mPa·s)than have previously been studied was investigated by spraying at a series of applied voltages and flow rates.The results showed that to obtain stable cone-jet mode spraying and hence gain better monodispersity of droplets,electrical conductivity,viscosity and surface tension of the liquid are important controlling factors.The stable cone-jet mode could be easily established for liquids having shear viscosities in the range from 80 to 1 400 mPa·s and surface tensions below 65 mN·m-1.In contrast,methylcellulose aqueous solutions with shear viscosities ranging from 10 to 540 mPa·s and moderate surface tensions(50~56 mN·m-1)generated more complicated spraying modes.However,fine TiO2 powder(a few micrometers in size)could be prepared using the EA method from its precursor solutions.

Preparation of TiO2 and SiC Films from Their Precursors Using Electrospraying

Titanium dioxide(TiO2) films were prepared by cone - jet mode electrospraying a titanium ethoxideprecursor solution onto a silicon substrate.The effects of spraying time,substrate temperature and aging on thesurface morphology of the films prepared were studied.Thin films obtained after spraying for 600 s were aged atroom temperature to form a porous TiO2 network with pores in the size range of 100 - 500 nm.Thicker filmswere prepared by spraying for 3 000 s,but these cracked on drying although it can be concluded that films pre-pared using a higher substrate temperature were denser.By this method,SiC coating was also prepared on anAl2O3 substrate using polysilane as a precursor.The result implies the potential of an industrial production ofdye sensitized solar cells by electrospraying technique.

A Review of Some Experimental Spray Methods for Marine Cloud Brightening

Marine Cloud Brightening (MCB), should it ever need to be deployed, envisions the formation of 1017salt Cloud Condensation Nuclei (CCN) per second coming from each of several thousand vessels deployed worldwide. The creation of this many nuclei on such a vast scale, from micron- or submicron-sized seawater droplets, preferably mono-disperse, poses a considerable engineering challenge. Various existing or experimental spray methods were investigated for feasibility, resulting in the identification of a few with promising results. Electro-spraying from Taylor cone-jets, using either silicon micromachined long capillaries or short capillary polymer substrates attached to a porous substrate, appears to have the best potential for implementation of all the methods that have been investigated so far.