Research On The Friction Torque Of Magnetic Fluid Rotary Seal

The electro-optical pod is an important part for military aircraft to detect,identify and aim targets.In order to prevent external impurities such as water vapor and dust from entering its interior,it is necessary to apply dynamic seal to its rotating shaft.In general,the dynamic sealing mode of electro-optical pod shafting is rubber ring sealing,but this mode has many problems,such as large friction torque,low rotation precision and poor sealing performance.Magnetic fluid rotary seal is a kind of dynamic seal which has the advantages of zero leakage,long service time and high reliability,and which is suitable for the rotating shaft seal of electro-optical pod.In view of the large friction torque of magnetic fluid seal at low temperature and other problems,theoretical,numerical simulation and experimental research are carried out in this thesis.The major work is described as follows:(1)The magnetic dipole model is established.By analyzing the magnetic potential energy of the magnetic dipole pair and the magnetic force between the magnetic dipoles,the mechanism of the magnetic particles agglomerating into chains in the magnetic fluid under the action of magnetic field is expounded.Based on the force analysis of the magnetic dipole chain,the reason of the friction torque of the magnetic fluid rotary seal is explained,and the formula of the micro friction torque of the magnetic liquid is established.(2)The rheological properties of MF01 and MF02 magnetic fluids are measured by the Anton Paar MCR302 rheometer,the viscosity of which decrease with the increase of shear rate,whereas aggrandize with the increase of the strength of the magnetic field.In addition,the magnetization curves of magnetic fluids are measured by the HH-15 vibration sample magnetometer.The concentration distribution of the magnetic fluid is not uniform and the saturation magnetization intensity is different in the non-uniform magnetic field.(3)According to the working condition of electro-optical pod and the characteristics of magnetic fluid,two kinds of magnetic fluid rotating seal structure schemes are proposed,which are single pole structure and double pole structure.The simulation analysis of magnetic field is completed by software COMSOL Multiphysics,and the theoretical pressure value of the two schemes are calculated,and the single pole structure scheme of magnetic fluid rotary seal is determined,and the design and selection of the pole boots,permanent magnets,rotating shaft,magnetic ring,shell and other parts are completed.(4)The low temperature friction torque experiment of magnetic fluid rotating seal is completed by using the high and low temperature alternating humidity and heat test chamber.The effects of temperature,number of turning turns,standing time and type of magnetic fluid on the friction torque of magnetic fluid rotary seal are studied.The relationship between the friction torque of the magnetic fluid rotary seal and the temperature is fitted by the curve,and the relationship between the friction torque of the magnetic fluid rotary seal and the standing time is established.(5)The friction torque test platform of magnetic fluid rotary seal is established,and the dynamic seal is carried out at a speed of 120 rpm..The pressure resistance and friction torque of the magnetic fluid rotary seal increase with the increase of the injection amount of magnetic fluid.When the maximum pressure resistance value is reached,the pressure resistance no longer increases with the increase of the injection amount,but the friction torque continues to increase with the increase of the injection amount.In addition,when the magnetic fluid seal is broken,the pressure will continue to drop.When the pressure in the sealing chamber drops to about 30 k Pa,the sealing ability of the magnetic fluid will recover,and the friction torque generated by the magnetic fluid will also decrease accordingly.There are 67 figures,16 tables,90 references in this paper.