Numerical Simulation and Optimization Design for Magnetic Fluid Sealing Device
In this paper the principle of magnetic fluid seals is discussed. Based on the finite element software ANSYS, the magnetic field of magnetic fluid sealing device with three slots and four pole teeth is analyzed, and the size parameters of magnetic fluid sealing pole are optimized. The results show that the difference between the maximum and minimum intensity of magnetic field in the area near the shaft determine the sealing capacity of sealing device. The gap of seal should not be larger than 0.3mm. The optimized parameters which are provided for practical design can increase sealing capacity of sealing device as well as decrease the volume of sealing device.
Numerical Simulation and Experimental Validation of the Critical Pressure Value in Ferromagnetic Fluid Seals
Ferrofluids have various engineering applications, and one of them is magnetic fluid seals. Development for this design is a complex process, which requires knowledge about ferrofluid physical properties and magnetic field distribution inside the sealing gap. One of the most important parameters of ferromagnetic fluid seals is a critical pressure value. It is a pressure at which rapid leakage will occur. This publication presents the results of critical pressure value obtained from experimental studies and calculations based on numerical simulations. Shape of sealing stage, volume of ferrofluid, and volume of permanent magnet used in seal construction were taken into account. Experiments and calculations were performed for four ferrofluids differ in saturation magnetization, density, and zero magnetic field viscosity.
Intensification of Bubble Disintegration and Dispersion by Mechanical Stirring in Gas Injection Refining
Water model experiments were performed for establishing highly efficient gas injection refining processes. Mechanical stirring was applied to disintegrate the injected bubbles and to disperse them widely in the bath. The bubble disintegration and dispersion were investigated by changing rotation mode (direction of rotation), rotation speed, blade size of the impeller and gas flow rate. Forward rotation of the impeller induced a stable tangential flow and could not disperse bubbles in the bath due to formation of a vortex around the impeller shaft. The tangential flow could be suppressed by forward–interrupt rotation, which could reduce the vortex formation to some degree. However, forward–interrupt rotation could not disperse the bubbles widely in the bath. Forward–reverse rotation could prevent the vortex formation completely and create a strong shear stress field, which intensified the bubble disintegration and dispersion in the bath. Higher impeller rotation speed and larger blade length in forward–reverse rotation could enhance the bubble disintegration and make the dispersed bubbles smaller. The bubble dispersion zone became wider with larger blade length. The bubble size tended to be larger at higher gas flow rates. However, its dependence on the gas flow rate became smaller at higher impeller rotation speed.