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 capil...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.展开更多
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 ...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.展开更多
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 c...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.展开更多
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 ...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.展开更多
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 m...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.展开更多
以G往关于电喷雾过程仿真研究对象多局限于低电导率液体,而电喷雾推力器使用的工质主要为高电导率离子液体,推力器工作时,离子液体在强电场作用下形成锥形,并在末端发射出锥形等离子体荷电喷雾。但离子液体受空间电荷、液体内部电流及...以G往关于电喷雾过程仿真研究对象多局限于低电导率液体,而电喷雾推力器使用的工质主要为高电导率离子液体,推力器工作时,离子液体在强电场作用下形成锥形,并在末端发射出锥形等离子体荷电喷雾。但离子液体受空间电荷、液体内部电流及液面电流的影响较大,电流体力学过程更为复杂,相关仿真研究极为匮乏。本文通过加入未简化的电荷守恒方程,考虑空间电荷及电流对锥射流形成与演化的影响,并耦合高斯定律和Navier-Stokes(N-S)方程求解流场及电荷分布,使用volume of fluid(VOF:流体体积)方法追踪液-气界面的变化,对高电导率液体的电喷雾锥射流形成过程开展了仿真研究。本次仿真工作以庚烷为工质模拟了锥射流形成与演化过程,得到电荷、电势和流场的分布,并与未考虑空间电荷的理想电介质模型进行对比。仿真结果表明,在低电导率情况下,本文模型与理想电介质模型的结果相近;高电导率情况下,本文模型得到的结果与相关实验更加吻合。展开更多
为合理选择微型荷电喷雾燃烧器的结构设计和工作参数,基于新设计的微型毛细管电极–环形电极–网格双电极荷电喷雾燃烧器,开展液体燃料乙醇雾化实验研究,得出了稳定的锥–射流雾化工作模式。基于该工作模式,对双电极产生的电场强度进行...为合理选择微型荷电喷雾燃烧器的结构设计和工作参数,基于新设计的微型毛细管电极–环形电极–网格双电极荷电喷雾燃烧器,开展液体燃料乙醇雾化实验研究,得出了稳定的锥–射流雾化工作模式。基于该工作模式,对双电极产生的电场强度进行理论计算,采用数值模拟的方法对流场和电场的耦合场进行分析求解,运用乙醇–空气两相流水平集方法模拟乙醇的流动。在体积流量为1 m L/h、毛细管电压4.19 k V、环形电极电压1 k V时得到了稳定的锥–射流、毛细管附近场强分布和两相流的速度场。经过理论计算得出了乙醇产生雾化的最小体积流量。研究表明:轴向场强和径向场强在锥射流内部均逐渐增大,在锥射流界面达到最大值后逐渐减小。由于射流的外侧速度矢量出现漩涡并沿分界面的切面方向运动,促进了锥射流的形成。当环形电极电压一定时,高于最小体积流量的乙醇在适合的毛细管电压下可得到稳定的锥射流。展开更多
基金National Natural Science Foundation of China(52076105)Natural Science Foundation of Jiangsu Province(BK20171301)。
文摘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.
基金supported by the National Basic Research Program of China(Grant No.2013CB733004)
文摘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.
文摘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.
文摘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.
基金supported by the Science Foun-dation of Educational Commission and Provincial Key Laboratory Program of Liaoning Province of China(Grant No.2008593 and CL-200902)~~
文摘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.
文摘以G往关于电喷雾过程仿真研究对象多局限于低电导率液体,而电喷雾推力器使用的工质主要为高电导率离子液体,推力器工作时,离子液体在强电场作用下形成锥形,并在末端发射出锥形等离子体荷电喷雾。但离子液体受空间电荷、液体内部电流及液面电流的影响较大,电流体力学过程更为复杂,相关仿真研究极为匮乏。本文通过加入未简化的电荷守恒方程,考虑空间电荷及电流对锥射流形成与演化的影响,并耦合高斯定律和Navier-Stokes(N-S)方程求解流场及电荷分布,使用volume of fluid(VOF:流体体积)方法追踪液-气界面的变化,对高电导率液体的电喷雾锥射流形成过程开展了仿真研究。本次仿真工作以庚烷为工质模拟了锥射流形成与演化过程,得到电荷、电势和流场的分布,并与未考虑空间电荷的理想电介质模型进行对比。仿真结果表明,在低电导率情况下,本文模型与理想电介质模型的结果相近;高电导率情况下,本文模型得到的结果与相关实验更加吻合。
文摘为合理选择微型荷电喷雾燃烧器的结构设计和工作参数,基于新设计的微型毛细管电极–环形电极–网格双电极荷电喷雾燃烧器,开展液体燃料乙醇雾化实验研究,得出了稳定的锥–射流雾化工作模式。基于该工作模式,对双电极产生的电场强度进行理论计算,采用数值模拟的方法对流场和电场的耦合场进行分析求解,运用乙醇–空气两相流水平集方法模拟乙醇的流动。在体积流量为1 m L/h、毛细管电压4.19 k V、环形电极电压1 k V时得到了稳定的锥–射流、毛细管附近场强分布和两相流的速度场。经过理论计算得出了乙醇产生雾化的最小体积流量。研究表明:轴向场强和径向场强在锥射流内部均逐渐增大,在锥射流界面达到最大值后逐渐减小。由于射流的外侧速度矢量出现漩涡并沿分界面的切面方向运动,促进了锥射流的形成。当环形电极电压一定时,高于最小体积流量的乙醇在适合的毛细管电压下可得到稳定的锥射流。
