Research On Characteristics Of Non-newtonian Magnetic Fluids Seals Of Liquid Environment

Due to its advantages of long life,no leakage and easy maintenance,non-Newtonian magnetic fluid seal has become an ideal sealing form for some liquid media.However,improper design will affect the operation stability and service life.In this paper,the failure mechanism,sealing performance and influencing factors of non-Newtonian magnetic fluid seal in liquid phase environment(hereinafter referred to as NNMFSL)are systematically and deeply studied by the method of combining magneto-thermal-flow coupling numerical simulation and experimental study.The level set equation was introduced to accurately describe the topological changes of liquid-magnetic two-phase interface,and a multi-field numerical analysis model of magnetic field,temperature field and liquid-magnetic two-phase flow was established.The distributions of magnetic field,temperature field,velocity field and pressure field of NNMFSL were simulated.The failure mechanism of the NNMFSL was analyzed,and the interface stability between the non-Newtonian magnetic fluid and the sealed liquid and its influencing factors were investigated.The analysis results show that when the axial magnetic force of non-Newtonian magnetic fluid is weakened,it cannot continue to exist in the seal gap,forming a leakage channel and resulting in seal failure.The stability of the liquid-magnetic two-phase interface can be increased by the use of non-Newtonian magnetic fluids with high viscosity.Based on the magneto-thermal-flow coupling analysis model,the influences of rotating speed,magneto-hydraulic filling rate,seal gap and pole teeth width on the pressure resistance value and non-Newtonian magnetic fluid temperature of NNMFSL were simulated and analyzed.The results show that the temperature of the non-Newtonian magnetic fluid increases and the pressure resistance decreases with the increase of the rotating speed.The pressure resistance of the seal can be improved by increasing the filling rate or the width of the pole teeth.The influences of rotating speed,magneto-hydraulic filling rate,seal gap and pole teeth width on the pressure resistance value and non-Newtonian magnetic fluid temperature were analyzed by orthogonal optimization method,and the optimal operating conditions and structural parameters range of the seal structure were obtained.A NNMFSL device was developed,a seal test rig was built,and static and dynamic seal tests were carried out.Five kinds of non-Newtonian magnetic fluids were prepared by mixed rolling method,and the influence of non-Newtonian magnetic fluids properties on sealing performance was analyzed.The effects of rotating speed and sealing gap on the pressure resistance and non-Newtonian magnetic fluids temperature were analyzed.The experimental values were in good agreement with the simulated values,which verified the accuracy of the magneto-thermal-flow coupling numerical analysis model.The research on the performance of NNMFSL in this paper provides a new calculation idea and method for NNMFSL two-phase flow,reveals the mechanism of differential pressure failure of NNMFSL,and provides guidance for the structure optimization and performance improvement of NNMFSL,and further promotes its engineering application and promotion.