| The behavior of droplets hitting substrate surfaces and spreading is widely used in manufacturing,such as inkjet printing,3D printing,spray and spraying.In the process of lithium battery membrane preparation by spraying method,the droplets are ejected from the nozzle under the action of dispersing disc,flown to the surface of the substrate,spread out and spread back to form the coating.Droplet diameter,impact velocity,viscosity,surface tension,etc.are important factors affecting droplet spreading characteristics,which have an important influence on the quality of lithium battery diaphragm.Therefore,it is necessary to explore the spreading characteristics of droplet impact substrate film.The specific research content of this paper is as follows:(1)Based on the principle of energy conservation,the mathematical model of droplet spreading in spraying process was established.The energy change of droplet from the dispersive disk to the completion of spreading was analyzed.By solving the energy conservation equation,the mathematical expressions of maximum spreading coefficient and final shrinking coefficient were obtained,and the influencing factors of spreading process were determined.(2)Taking the droplet impact velocity as the research object,the force of droplet flying in the air was analyzed,and the dynamic equation of droplet was established and solved.The velocity and displacement of the droplet during flight were obtained with time,and the influence of the rotation speed,diameter,vertical distance between the edge and the substrate,diameter,density and viscosity of the droplet on the droplet impact velocity was determined.(3)Based on lattice Boltzmann method,the simulation model of droplet spreading on substrate surface was established.The flow field during droplet spreading was analyzed,and the spreading coefficient,shrinkage coefficient,maximum spreading coefficient and final shrinking coefficient were taken as the research objectives.The influence laws of droplet diameter,impact velocity,viscosity,surface tension,impact Angle and substrate surface roughness on the spreading process were obtained.Aiming at the splash phenomenon of droplets in the simulation process,by changing the impact velocity of droplets,the velocity threshold of the breaking of Newtonian and non-Newtonian droplets under different diameters and the volume ratio of the broken droplets to the original droplets were obtained,and the mechanism of the spreading and splashing of droplets was clarified.(4)Spraying experiments were designed to explore the effects of different disc speed,feed amount,substrate type and impact Angle on the droplet spreading process.Through the data analysis of the experimental samples,the influence law of different process and material parameters on the average spread diameter of droplet was obtained,and the accuracy of the simulation results was verified. |
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