Study On The Seal Performance Of Magnetic Fluid Applied In Stirred Reactor Rotating Axis

As a new type of seal method, magnetic fluid seal takes the advantages of zero-leakage, non-abrasion, long life and self-lubrication, it can be widely used in the conditions of low pressure, rotation seal and dust prevention. While, the stirred reactor rotating axis seal is difficult to lubricate, and requires high-quality seal, the magnetic fluid seal is just a proper seal method for stirred reactor rotating axis.The orthogonal experiments are applied in the thesis, the magnetic fluid is acquired by the heating alcohol and water method, and a better precipitating reaction condition is listed:the mixed fluid is ex-heated, the reaction time is 20 minutes, the reaction temperature is 60℃, the dropping rate of sodium hydroxide is 0.075ml per second. The better surface active coating reaction condition is listed:the dropping rate of sodium oleate is 0.05ml per second; the reaction temperature is 75℃, and the pH value is 4. The magnetic fluid acquired has a good quality and can satisfy the requirement of seal.According to the present research results, the factors which influence the magnetic fluid seal most are seal gap and intensity of magnetic filed, and the later one is chosen as the research subject in this thesis; this thesis analyzes the magnetic field deeply. As per the axisymmetric model of magnetic field, the three dimensional model can be simplified to the two-dimension model. The thesis uses the finite element method to analyze the ring-shaped permanent magnetic field from the aspect of electromagnetism, also sets up the model with the software of COMSOL Multiphysics and calculates the magnetic field. Meanwhile, the thesis compares the magnetic intensity created by several shapes of magnetic teeth; finds out the relationship between the magnetic field and the different-shape teeth, as well as the seal performance. Then, according to the magnetic fluid seal calculation formula, the thesis analyzes the different performance of different-shapes magnetic teeth, and the result shows the 60 degree teeth has the best seal performance.The thesis also does research in the free boundary of magnetic fluid in seal conditions.In the condition of static seal, for the magnetic fluid has very small relative permeability, and its boundary can be considered submitted to the isomagnetic line, and can be fixed as per the volume of the magnetic fluid injected. While in the condition of dynamic seal, the magnetic fluid is stressed by centrifugal force, its high pressure boundary is assumed not changed, but its low pressure boundary shrikes, the boundary can be acquired by step changing interation method, and the result is consistent with the theory analysis.Summarily, this thesis uses the finite element method to analyze the magnetic field created by ring-shaped permanent magnet, compares the seal performances of different-shape teeth, and also calculates the low pressure boundary change both in static and dynamic seal. The conclusions got in the thesis are meaningful to the seal failure judgment.