Ciwen Sha

Experimental Study on Alternating Magnetic Field Magnetohydrodynamic Pump

An experimental apparatus to investigate AC MHD pump was established, which mainly consists of a rotary permanent magnet with 4 poles an annular channel, a motor, a shaft and a platform. The magnet generates a field similar to sinusoid with the maximum of 0.9 T in the channel when it is rotated up by the motor to simulate an AC magnetic field. This moving magnetic field acts on the conductive fluid in the channel, and produces an electromagnetic force to move the fluid in the same direction as that of the magnet rotating. Experiments were carried out to investigate the performance of the pump. Flow velocity in the annular channel was measured for different conductivities and rotating speeds of the magnet. The results show that the flow rate and pressure increase as the magnetic field strength, fluid conductivity and frequency of the magnetic field increase.

Analytical study on flow process of floating-oil recovery device from oil-contaminated seawater by MHD method

A new method of recovering maritime oil-spill based on electromagnetic force, the so-called MHD oil-spill recovery method was proposed in the IEECAS. The operating process of MHD channel was described in this article. Numerical study was carried out using a two-dimensional water-air two-phase model and the VOF method. The agreement between the numerical and the experimental results was reached.

Progress of the MHD ship propulsion project in China

A small project for developing superconducting MHD ship propulsion is included in Chinas State High Technology Development Program. The project goal is to construct a MHD model ship with a 5T superconducting helical thruster. A 1.0 ton model ship with 3.5 m length, 0.85 m width was driven by the 5 T, 270 A superconducting helical thruster in a 25 m long, 2.75 m wide and 2.0 m deep salt-water test tank to achieve 0.61/spl sim/0.68 m/s velocity, the measured driving force is 40/spl sim/45 N. A suggestion to extend this project for another 2 years has been approved. The progress of the project is reported.

PERFORMANCE ANALYSES OF HELICAL MHD THRUSTER IN 14 TESLA

The performance characteristics of the helical MHD thruster at the magnetic field of 14T are studied with a simplified analysis model. In this model, the MHD active section is treated as the outspreaded linear duct considering the distribution of current density and Lorentz force on the radial distance between the electrodes, that usually was not considered in the previous works. An equivalent friction coefficient is defined to describe the hydraulic loss in the MHD active section, the value of which is modified by experiments. The flow guide and rectifier are simplified to the contraction and expansion. The design analysis of the thruster shows that the best helical loop number (climb angle) exists to get the peak value of the thruster efficiency in the helical MHD thruster in the given condition, and a larger efficiency can be maintained over a wide range of climb angle in longer active length. For the joint experiment thruster, the optimized climb angle is 16 degrees. The performance analysis of the thruster shows a good agreement between the calculation results and experimental data. The electromagnetic efficiency increases with the magnetic field, and decreases as the electric current density increases. The thruster efficiency peaks at a certain point and then falls down as the load factor increases. And the peak value of the thruster efficiency in the experiment was about 13% in the load factor of 2.6. The analysis shows that the higher thruster efficiency can be obtained if the out loop has smaller loss coefficient.

Permanent Magnet Type Eddy Current Heater Based on Cylindrical Halbach Array for Reducing Oil's Viscosity

The eddy current, Joule heat and input electrical power of a permanent magnet type eddy current heater based on cylindrical Halbach arrays to reduce the viscosity of crude oil in oil wells were analysed and studied by means of a three-dimensional finite-element method. The results show that when Halbach arrays generate a 0.9 T sinusoidal static field and the annulus conductor is copper, the Joule heat is about 575 W/m for a relative translational motion of 0.5 m/s in direction. The thermal efficiency of the heater is about 77.6%.

End effect of liquid metal magnetohydrodynamic generator in wave energy direct conversion system

The influence of end effect on electromotive force, induced magnetic field and flow loss of the reciprocating liquid metal magnetohydrodynamic (LMMHD) generator was investigated. The 3D numerical simulation was done firstly, then the electromagnetic and flow performances predicted from quasi-2D and 3D analyses were compared and three end influence coefficients quantifying end effect were defined. Factors influencing end effect were analyzed and new method to suppress the end effect was proposed in the end. The study shows that the end gradient of the external magnetic field and end leakage current are main causes of the end effect in the LMMHD generator. The velocity in MHD channel and end gradient of the applied magnetic field are two key factors affecting the end effect greatly. The integration of insulating vane and low end gradient of the applied magnetic field can effectively suppress the end current and decrease energy losses.

Design Study on a Large Force Superconducting Linear Driver

A tubular superconducting linear driver with a conduction-cooled opposite-poles solenoid superconducting magnet and a DC resistive coil that can generate a large axial force was presented in this paper. Design and analysis of a demonstration tubular superconducting linear driver were conducted. The results show that the tubular superconducting linear driver is able to generate an axial force of 10 kN with stroke of 0.25 m.

Analytical Study on End Effect of Liquid Metal MHD Generator

End effect causes much energy loss in MHD power generator duo to the external magnetic field in the end region of the effective MHD channel. It is effective to lessen the end loss using a tapered magnetic field and a tapered flow channel outside the electrode. An analysis in theory has been given first, and then some numerical simulations have been carried out. The results show that even without a uniform magnetic field in all channels, the influence of end effect has been weakened greatly with no return-path current and little eddy current when using a trapezoidal magnetic field and a trapezoidal geometry of flow channel.

Superconducting Linear Driver Electromagnetic Underwater Launching System

An electromagnetic underwater launching system with superconducting linear driver is presented in the paper. Design and analysis of a demonstration system were conducted. The system has an opposite-poles solenoid superconducting magnet with a warm bore diameter of 200 mm and the maximum radial field component of 0.85 T. It is expected to generate a desired axial force with the maximum of 10 kN and eject an object of 105 kg with the launching speeds of 5.9 m/s in 0.5 seconds.

Bio-fluid flow in a rectangular duct under the action of a traveling wave magnetic field

The laminar, incompressible, three-dimensional, viscous unsteady blood flow in a straight rectangular duct was numerically studied under the action of a sinusoidal traveling wave magnetic field. The mathematical model was based on magnetohydrodynamics and numerical results were obtained using a finite volume method. The magnetohydrodynamic characteristics with consideration of wall effect and skin effect were investigated. The results show that the blood flow is appreciably influenced by the application of the traveling magnetic field. The wall effect and skin effect reduce the eddy current greatly and thus lower the effective electromagnetic force and pressure head largely when the flow rate is constant.