Molecular Simulation Of The Influence Of Agiag On The Migration And Aggregation Of Water Molecules At The Oil-Paper Interface

Macroscopic experiments have found that aging has a significant effect on the distribution and migration of moisture between oil papers,but the microscopic mechanism of this phenomenon is still unclear.For this reason,based on molecular simulation technology,this paper has carried out research on the influence of aging on the migration and aggregation of water molecules at the oil-paper interface.A molecular model of the oil-paper composite medium with a weight of 105 atoms was established.The furfural content and the small molecule acid content were used as the aging indicators of the oil-paper insulation medium.The furfural content in the cellulose was set as 10%for severe aging and 5%for furfural as moderate aging.The small molecule acid content of 2%is severe aging,and the small molecule acid content of 1%is moderate aging.The heating process from 20℃ to 80℃ is simulated,and the mutual binding energy,radial distribution function,and radial distribution function of water molecules in the model are calculated.The characteristic parameters such as diffusion coefficient,free volume,and number of hydrogen bonds are analyzed.The mechanism of the effect of aging on the migration and aggregation of water molecules at the oil-paper interface is analyzed.Finally,in order to increase the calculation speed and lay the foundation for larger-scale calculation research,a meso-scale model of cellulose and insulating oil was established through the coarse-grained method,which was compared with the macroscopic and microscopic models to verify their equivalence.The research results show that the increase of furfural and small molecule acid content in cellulose will increase the binding energy of water molecules and cellulose,and increase the diffusion coefficient of water molecules in cellulose.Under the interface effect of insulating oil,the diffusion coefficient of water molecules in the normal direction of the interface decreases.Coupled with the restriction of the electric field force,the free volume of the oil-paper interface area decreases and the number of hydrogen bonds increases,which increases the possibility of liquid water.When the furfural content in cellulose is 10%,the peak value of the radial distribution function in the interface zone increases by 39.2%,the free volume fraction decreases by 5.5%,and the number of hydrogen bonds increases by 67.8%;when the content of small molecular acids in cellulose is 2%,In the interface zone,the peak value of the radial distribution function increased by 77.7%,the free volume fraction decreased by 5.1%,and the number of hydrogen bonds increased by 70.1%.The difference between the simulation results of the established mesoscopic model and the all-atom microscopic model is less than 10%,Operation time is reduced to 1/1200 of the original,and the simulation scale is expanded by 10 times.