Zhi Li Zhang

The Experimental Study of the Magnetic Fluid Damper Based on the Principle of Second-Order Buoyancy

Two different structure of dampers based on the principle of second-order buoyancy were designed in this paper. In order to verify the reduction of the vibration, a test rig was set up. On the test rig, the reduction effect of two different dampers was studied by adjusting the amount of the magnetic fluid. The experiment results indicate the relationship between the damping effect of magnetic fluid damper and the amount of magnetic fluid and this analysis result is benefit to the design of the dampers.

Study on Magnetic Fluid Static Seal of Large Gap

Researchers have been studying the magnetic fluid seal of small gap in the past. In order to meet the static seal requirements of large gap in aviation, aerospace, metallurgy, and so on. We set up the experimental rig of magnetic fluid static seal and designed the static seal of magnetic fluid. In the experimental rig, we studied the static seal of magnetic fluid and obtained the relationships among the burst pressure and the amount of injection of magnetic fluid, seal gap, temperature and magnetization in the experimental rig. In theory, we calculated the distribution of magnetic field under the seal gap and reasoned sustained pressure and temperature and calculated the burst pressure in different gaps and different saturation magnetization. We analyzed the experimental and theoretical results in detail. The theoretical analysis and tests indicated that magnetic fluid seal of large gap and large diameter can sustain a definite pressure and meet the requirements of practical problems.

Structure Design of Magnetic Fluid Static Seal at Large Diameter Flange

In order to meet the requirements of the static seal at large diameter in chemical industry, aerospace industry and military industry, we designed a magnetic fluid static seal at large diameter flange and set up a test rig. We studied the effect of magnetic fluid static seal on the test rig. Finally, we obtained the relationship between the anti-pressure capacity and the number of the seal stages. We also calculated the distribution of the magnetic field in the seal gap and the anti-pressure capacity in theory. The theoretical analysis and the experiment result indicate that the design of the magnetic fluid static seal at large diameter flange is feasible and can be used to meet the practical problems.

Nanostructure of a Glass-Like Carbon Characterized by X-Ray Diffraction and Electron Energy Loss Spectroscopy

In our present study, phenolic resins heated at different temperatures from 600 oC to 3000 oC were analysised in terms of phase structure and chemical structure using X-ray diffraction and high resolution transmission electron microscopy equipped with an electron energy loss spectrometer (EELS). It is shown that materials appear to be amorphous with many micro-pores surrounded by crystalline graphite layers; the formation of the pore is due to the gas evolution reaction. Using the intensities of peaks in EELS CK-ionization edge which arise from transition of an atomic 1s electron to the π* and σ* antibonding band-like states, the percentage of sp2-bonded carbon have been analyzed and the results reveal notable differences with heat treatment temperature.

Theoretical analysis and experimental study on breakaway torque of large-diameter magnetic liquid seal at low temperature

The existing researches of the magnetic liquid rotation seal have been mainly oriented to the seal at normal temperature and the seal with the smaller shaft diameter less than 100 mm. However, the large-diameter magnetic liquid rotation seal at low temperature has not been reported both in theory and in application up to now. A key factor restricting the application of the large-diameter magnetic liquid rotation seal at low temperature is the high breakaway torque. In this paper, the factors that influence the breakaway torque including the number of seal stages, the injected quantity of magnetic liquid and the standing time at normal temperature are studied. Two kinds of magnetic liquid with variable content of large particles are prepared first, and a seal feedthrough with 140 mm shaft diameter is used in the experiments. All experiments are carried out in a low temperature chamber with a temperature range from 200°C to −100°C. Different numbers of seal stages are tested under the same condition to study the relation between the breakaway torque and the number of seal stages. Variable quantity of magnetic liquid is injected in the seal gap to get the relation curve of the breakaway torque and the injecting quantity of magnetic liquid. In the experiment for studying the relation between the breakaway torque and the standing time at the normal temperature, the seal feedtrough is laid at normal temperature for different period of time before it is put in the low temperature chamber. The experimental results show that the breakaway torque is proportional to the number of seal stages, the injected quantity of magnetic liquid and the standing time at the normal temperature. Meanwhile, the experimental results are analyzed and the torque formula of magnetic liquid rotation seal at low temperature is deduced from the Navier-Stokes equation on the base of the model of magnetic liquid rotation seal. The presented research can make wider application of the magnetic liquid seal in general. And the large-diameter magnetic liquid rotation seal at low temperature designed by using present research results are to be used in some special fields, such as the military field, etc.

Preparation and Characterization of Diesel Fuel-Based Magnetic Fluids

Among different types of magnetic fluids, diesel fuel-based magnetic fluids have a high application value because of low viscosity, low volatile and cheap carrier liquid. In this paper, Fe3O4 nanomagnetic particles were prepared, optional technological conditions were determined. It was that concentration of the reactors was 0.6mol/L, reaction temperature was 70°C and reaction time was 1h. Then it was found that the appropriate coating time for surfactant was 4 hours. The particles prepared under this process had the high saturation magnetization and preferable dispersibility. Finally by ultrasonic oscillating combined with mechanical raking, diesel fuel-based Fe3O4 magnetic fluids were prepared.

Study on Magnetic Liquids Properties for Sensor Design

The physical properties of magnetic liquids are theoretically analyzed in this paper, such as the effect of the magnetic volume force on the free surface of magnetic liquids, the density spectrum of the magnetic liquids based on horizontal component of the magnetic volume force, the first order levitation principle and the second order levitation principle, the magneto-electric principle of magnetic liquids, the fluidity of magnetic liquids used as magnetic core and the fluxgate effect of magnetic liquids. Some methods to study the properties of magnetic liquids were provided by the authors, and the effects of the magnetic volume force on the free surface of magnetic liquids and the second order levitation effect were experimentally studied in this paper. The analysis methods that provided in this paper may be applied to the design of new sensors.

Study on the Structure of the Magnetic Fluid Damper

Magnetic fluid damper is a kind of shock absorber which based on the principle of second-order buoyancy of magnetic fluid. In this paper, the structure of magnetic fluid damper is analyzed firstly, and then a variety of structural parameters on the damping effect are tested. Focusing on the different gasket angles in the damper, we found that gasket angles play a key role in the damper to influence on the damping effect. A corresponding model is put forward to analyze the inherent reasons.

Preparation and Photo-Catalysis Properties of Fe3O4/TiO2 Nanocomposite

As a Kind of Most Common Used Photocatalyst, TiO2 Nanomaterials Existing Disadvantages on Low Light Energy Utilization in Visible Light Range and Difficulty on Recycle. in Our Study, Different Proportions of Fe3+ and Fe2+ Ion Were Doped with Nano-Ti02 Particles in Structure of Rutile Type through Method of Chemical Precipitation. the Result Showed that Nano-Composites Formed by TiO2 Coexist with Fe3O4, with the Average Size of the Composite Particles Nearly 20 Nm. the Photo-Catalyst Performances of the Composite Have Improved Largely, and so the Relatively Optimized Preparation Conditions Were Presented.

Effects of Magnetic Fluid on Magnetic Fluid Damper

A magnetic fluid damper which based on the principle of second-order buoyancy of magnetic liquid has been presented. During the process of damping, besides the elastic deformation of magnetic liquid adsorbed by permanent magnet, the main ways of energy dissipation are the friction functions, which include the friction between magnets and magnetic liquid, magnetic fluid and magnetic fluid and magnetic fluid and the shell of the damper. In order to investigate influence of magnetic fluid on damping effect, a series of experiments under different magnetic fluid with related parameters including magnetic fluid volume and saturation magnetization are carried out. It is found that both volume and saturation magnetization of magnetic fluid have optimal value on the damping effect of the damper.