Molecular Dynamics Simulation Of The Electrospray From Nanopores

The use of nano-nozzles makes electrostatic spraying more promising in micro-nano satellite thrusters,fiber manufacturing,mass spectrometry,drug design and other fields.However,the micro-mechanism of nano-electrostatic spraying,the factors affecting the starting voltage and the mechanism of pure ion spraying are not clear.For these problems,it is necessary to study the physical process of fluid spraying in nano-electrostatic spraying system.In this paper,the basic phenomena and mechanism of electrostatic injection at nanoscale are studied by molecular dynamics method.The main research contents are as follows:?1?Phenomenon and mechanism of nano-electrospary of sodium chloride conductive liquid.Ion distribution polarization is caused by external voltage,which makes the polarization potential strengthen the potential drop of the orifice and make the orifice produce high field strength.When the electric field force overcomes the surface tension,electrostatic spraying occurs.At the same time,a circular spraying mode is formed:the Taylor cone is formed;the second:the cone is unstable;the third:the jet is generated.The ions affect the hydrogen bond structure of the Taylor cone,and the fractured region of the jet is located in the weak region of the cone-top hydrogen bond grid.The fragmentation of the Taylor cone and the shape of the Taylor cone have a concentration dependence of the conductivity.?2?Analysis of factors affecting the starting voltage.It is found that the longer the orifice,the smaller the pore size,the larger the field strength of the orifice,and the lower the starting voltage.The appearance of the nozzle hole hardly affects the starting voltage;the starting voltage of the hydrophilic material is lower than that of the hydrophobic material,the more hydrophobic the material,the higher the starting voltage,and the starting voltage of the hydrophilic material does not change with the hydrophilicity;When the wall of the nozzle hole is charged,the concentration of the counter ion in the hole rises,which lowers the starting voltage of the ion opposite to the charged property of the wall,and causes the starting voltage of the positive and negative ions to be different;the temperature rise reduces the surface tension of the liquid,and the lower the starting voltage is caused.?3?Modeling and reliability studies of ionic liquid BMIMPF₆.Based on the CHARMM force field,the model and force field of the ionic liquid BMIMPF₆ were constructed.The reliability of the model was verified by studying the basic statistical physical properties,density,volume change rate,radial distribution,coordination number,diffusion coefficient and conductivity of the BMIPF₆ model.?4?Study on the characteristics of electrospary of ionic liquid BMIMPF6.BMIMPF6generates an ion beam during electrospraying.We can control the generation of pure ion injection by increasing the applied voltage,reducing the aperture and increasing the temperature.When pure ion injection occurs,the injection speed will increase sharply.Finally,the speed,ion current,thrust,specific impulse and efficiency produced by pure ion injection are calculated,we find the charge-to-mass ratio and efficiency of pure ion injection are effectively improved.