Research On Structure Optimal Design And Experiment Of High-speed Magnetic Fluid Seal

In recent decades,the research of magnetic fluid applications under special working conditions including the study of high-speed magnetic fluid seals have become a priority.The centrifugal force on the magnetic fluid under high-speed conditions is very large,and the excessive centrifugal force makes it difficult to stabilize the magnetic fluid under the extreme teeth.At the same time,the frictional dissipation between the shaft and the magnetic fluid generates more heat at high-speed conditions,then the temperature of the structure rises rapidly,making the saturation magnetization strength and viscosity of the magnetic fluid to become lower further more leading to the seal performance worse.The excessive centrifugal force and temperature at high-speed conditions have become the urgent problems to be solved.To these two problems,the following studies were conducted in this paper:(1)A diester-based magnetic fluid suitable for high-speed sealing was selected,and its saturation magnetization strength was measured at room temperature and high temperature.A linear fit use to obtain the saturation magnetization strength of the magnetic fluid as a function of temperature.The viscosity of the magnetic fluid at different temperatures,magnetic field strengths and shear rates was measured by a rheometer,and the viscosity-temperature characteristics of the magnetic fluid were fitted by the Slotte equation.(2)The design of magnetic fluid sealing parts at high-speed conditions,mainly includes the design of rotating shaft,pole shoe,permanent magnet,bearing and housing structure.By comparing the performance of different materials and the pressure resistance of the structure,2Cr13 was chosen as the material for the shaft and the pole shoe,and Nd Fe B was chosen as the material for the permanent magnet.By comparing the different parameters of structural seal pressure resistance,the design plan of 0.2mm width and1.2mm pitch was chosen.The cooling water tank is machined on the pole shoe and coolant is introduced into the part to solve the temperature rise problem.Considering that both sides of the cooling water tank should be sealed with rubber rings,the axial dimension of the pole shoe was designed to be 29 mm.(3)Multi-physics field analysis was conducted on the designed structure,and the maximum magnetic flux density in the sealing gap was 1.8T,and the maximum axial magnetic field force on the magnetic fluid is 1.112108N/m3 and the maximum radial magnetic field force is 7.77107N/m3,and the maximum pressure resistance of the seal is502.34 k Pa through magnetic field analysis.The variation of magnetic fluid with increasing pressure for static seals and high-speed seals with rotational axis linear velocity up to 20m/s is obtained by flow field analysis.The effect of centrifugal force on the change of magnetic fluid film at high-speed conditions is observed,.The pressure resistance of the static seal of the structure is calculated to be 323.08 k Pa,and the pressure resistance at a rotating shaft line speed of 20m/s is 275.14 k Pa.The temperature change of the structure when different cooling water is passed into the cooling water tank is obtained by temperature field analysis.And the magnetic fluid temperature change with heat flow density is fitted,and the magnetic fluid viscosity-temperature characteristics and magnetic temperature characteristics are linked,and the pressure resistance equation of the magnetic fluid seal for high-speed conditions is modified.(4)For the first time,the coupled simulation and optimization design method of magnetic field and temperature field simulation module is proposed,which can automatically sample and calculate different structural parameter models to construct an agent model of magnetic fluid seal at high-speed condition,and optimize the design of magnetic fluid seal cooling water tank at high speed,and get the optimized scheme of tooth groove axial distance of 10 mm and radial distance of 9mm.The maximum pressure resistance of the structural static seal is 304.52 k Pa,the maximum pressure resistance of the structural seal is 180.02 k Pa at 20m/s of the shaft speed without cooling line speed,and the maximum pressure resistance of 275.15 k Pa at 20m/s of the shaft speed at 0℃.