17-05-2012, 05:18 PM
MHD and Applications to Thermofluids of Fusion Blankets
MHDandThermofluids-1-3-07.ppt (Size: 2.47 MB / Downloads: 79)
MHD basics
What is MHD ?
MHD applications
Magnetic fields
Electrically conducting fluids
MHD equations
Scaling parameters
Hartmann problem
MHD flow in a rectangular duct
MHD pressure drop
Electric insulation
Complex geometry / non-uniform B-field
Numerical simulation of MHD flows
What is MHD ?
MHD covers phenomena in electrically conducting fluids, where the velocity field V, and the magnetic field B are coupled.
Any movement of a conducting material in a magnetic field generates electric currents j, which in turn induces a magnetic field.
Each unit volume of liquid having j and B experiences MHD force j x B, known as the “Lorentz force”.
A few facts about MHD
Alfvén was the first to introduce the term “MAGNETOHYDRODYNAMICS”. He described astrophysical phenomena as an independent scientific discipline.
The official birth of incompressible fluid Magnetohydrodynamics is 1936-1937. Hartmann and Lazarus performed theoretical and experimental studies of MHD flows in ducts.
The most appropriate name for the phenomena would be “MagnetoFluidMechanics,” but the original name “Magnetohydrodynamics” is still generally used.
MHD applications, 1
Astrophysics (planetary magnetic field)
MHD pumps (1907)
MHD generators (1923)
MHD flow meters (1935)
Metallurgy (induction furnace and casting of Al and Fe)
Dispersion (granulation) of metals
Ship propulsion
Crystal growth
MHD flow control (reduction of turbulent drag)
Magnetic filtration and separation
Jet printers
Fusion reactors (blanket, divertor, limiter, FW)
MHD applications, 2
In some MHD applications, the electric current is applied to create MHD propulsion force.
An electric current is passed through seawater in the presence of an intense magnetic field. Functionally, the seawater is then the moving, conductive part of an electric motor, pushing the water out the back accelerates the vehicle.
The first working prototype, the Yamato 1, was completed in Japan in 1991.The ship was first successfully propelled 1992. Yamato 1 is propelled by two MHD thrusters that run without any moving parts.
In the 1990s, Mitsubishi built several prototypes of ships propelled by an MHD system. These ships were only able to reach speeds of 15km/h, despite higher projections.
Magnetic fields
Earth – 0.5 10-4 T
Sun – 10-4 T, up to 0.4 T at sunspots
Jupiter – 10-2 T (strongest planetary magnetic field in the solar system)
Permanent laboratory magnets with ~0.1 m gap – about 1-2 T
Electromagnets – 25-50 T
Fusion Reactor (ARIES RS) – 12 T
Experimental Fusion Reactor (NSTX) – 1.5 T