Theoretical And Experimental Study On Sealing Performance Of Magnetic Sealant In Split Device

This paper proposes a new type of split seal structure using magnetic sealant to overcome the difficulty in the disassembly and maintenance of the large sealing device.Two kinds of magnetic sealants with different saturation magnetization used for split seal structure are synthesized.The pressure resistance of the split sealing structure is studied through theoretical calculation,simulation and experimental verification to find the optimal split sealing structure.The specific work is divided into the following parts.First of all,the background and significance of magnetic sealant used in split seal structure are studied,and the advantages and disadvantages of the gasket seal,the sealant seal and the magnetic sealant seal are analyzed.The bottleneck of the split seal structure is analyzed,and the application of the magnetic sealant is studied.The current research status of magnetic fluid,magnetic fluid seal,and magnetic sealant are summarized at home and abroad.The results show that magnetic fluid sealing technology is very mature,the study of magnetic sealant is limited to the preparation and performance investation,and the study of magnetic sealant applying to the seal gap of split pole shoes.The magnetic sealant in the seal gap can be controlled by magnetic field,and the use of magnetic sealant in split seal has important economic and application value in large-scale seal device.Secondly,the magnetic sealants were prepared,and the saturation magnetization and shear modulus of the magnetic sealants were characterized.According to the basic theory of colloid and non Newtonian fluid,the continuity equation,mass conservation equation and motion equation of magnetic sealant are derived based on which the theoretical formula of the maximum shear force is derived.According to the basic theory of magnetic sealant,the magnetic pressure resistance of magnetic sealant is calculated.Combining the viscous and magnetic properties of magnetic sealant,the theoretical pressure resistance of the magnetic sealant in the seal gap of the split sealing device is derived.Next,the split valve seal is simulated:To accomplish the sealing between split pole shoes and the shaft,and the sealing between split sleeve and rubber sealing ring,magnetic field simulation were done in the two positions mentioned above.The results show that the theoretical seal pressure resistance of magnetic sealant in the seal gap is much greater than that of ordinary sealants,but lower than that of the full pole shoes.On this basis,the magnetic sealant is still used to seal and bond the split pole shoes.The number of pole tooth are kept constant,the thickness of the split pole shoes are reduced with two rounds of magnets are added,and the theoretical pressure resistance of the split shose is higher than that of full pole shoes.Besides,a new type of structure has been designed for the sealing of split sleeve,and magnetic sealant is used to seal the split sleeve.The width of the magnetic stripe and permanent magnet used in the sleeve gap have an effect on the the magnetic field intensity at the leak point of the sleeve.After theoretical analysis and calculation,we come to a conclusion that the viscous pressure resistance of the magnetic sealant is much higher than the magnetic pressure resistance.In the liquid state,the seal gap can be filled evenly by magnetic sealant under magnetic field,and the seal pressure resistance can be achieved when the magnetic sealant in the solid state.The magnetic field in horizontal direction is more suitable for the split sleeve seal,and the magnets contacting with the pole shose have no influence on the magnetic field at the gap of the split sleeve.The theoretical analysis and simulation of magnetic field provide reference for the design of split seal structure,performance evaluation of different sealing devices,and prediction of interfacial failure.Finally,the seal of the split device is experimentally studied:Full pole shoes and split pole shoes are used in the design of split seal device,respectively.And also,ordinary sealant and magnetic sealant are used to glue the split,respectively.And the split sealing device is designed and processed.An experimental research was studied with full pole shoes,of which the pressure resistance was used as a standard to study the pressure resistance of the split pole shoes.First,we use ordinary sealant to bond the split pole shoes,and its sealing pressure resistance is far lower than that of the full pole shoes.Then the magnetic sealant whose magnetic permeability is 3-5 times higher than that of ordinary sealant is used to bond the split pole shoes,and the sealing pressure resistance is much higher than that of ordinary sealant,but lower than that of a full pole shoes.To further solve the sealing problem of split shoes,the structure of split shoes have been optimized.The experimental sealing pressure resistance of the optimized structure is 0.3 atmospheres higher than that of full pole shoes.The experimental results are consistent with the simulation results and verifying the correctness of the theory.According to the experimental research on the split seal sleeve using ordinary sealant and magnetic sealant,when the pressure resistance is between 1 atmospheric pressure and 2.5 atmospheric pressure,the seal leakage rate of the split sleeve by the magnetic sealant is obviously lower than that of the ordinary sealant under the same conditions,and this phenomenon shows the superiority of the magnetic sealant.The theoretical calculation of the sealing pressure resistance of the split-type sealing device is carried out under the condition of the split-type pole piece.The calculation process considers the influence of the reluctance of the split-type pole piece.The magnetic field in the sealing clearance using the complete pole piece,the split type pole piece bonded by ordinary sealant,the split type pole piece bonded by the magnetic sealant,and the optimized split type pole piece bonded by the magnetic sealant are calculated,based on which the theoretical sealing pressure resistance is obtained.The simulation and experimental research on the sealing pressure resistance ability is carried out,the theoretical analysis results,the simulation calculation results and the experimental results have a good consistency,which verifies the correctness of the theoretical analysis.