2. MHD propulsion thruster
ABSTRACT
The Magneto Hydro Dynamic (MHD) propulsion thruster is designed to use magneto
hydrodynamic force generated by sending electric current through a magnetic field created in
sea water by superconducting magnets. The principle of MHD propulsion is to apply the
Fleming's left hand rule of electromagnetics to sea water directly .In this propulsion system
magnetic field is created in sea water by magnets fixed on a hul1. When electric current is sent to
sea water at right angles to the magnetic field, and electromagnetic force (Lorentz force) acts on
sea water in the direction perpendicular to both the direction of magnetic field and that of electric
current. Propu1sion force is gained as a reaction force of this Lorentz force.
3. MHD propulsion thruster
INTRODUCTION
MHD
Magneto hydrodynamics involves magnetic fields (magneto) and fluids (hydro) that conduct
electricity and interact (dynamics).MHD technology is based on a fundamental law of
electromagnetism: When a magnetic field and an electric current intersect in a liquid, their
repulsive intersection propels the liquid in a direction perpendicular to both the field and the
current. Hannes Alfven was the first to introduce the term âMHDâ.
4. MHD propulsion thruster
Thruster
The Magneto Hydro Dynamic (MHD) propulsion thruster is designed to use magneto
hydrodynamic force generated by sending electric current through a magnetic field created in
sea water by superconducting magnets. The principle of MHD propulsion is to apply the
Fleming's left hand rule of electromagnetics to sea water directly .In this propulsion system
magnetic field is created in sea water by magnets fixed on a hul1. When electric current is sent to
sea water at right angles to the magnetic field, and electromagnetic force (Lorentz force) acts on
sea water in the direction perpendicular to both the direction of magnetic field and that of electric
current. Propu1sion force is gained as a reaction force of this Lorentz force.
.
The Lorentz force F (N) which is the source of thrust force T is given by the formula
F = J X B dv (N)
Here J is a current density vector of infinitesiml volume dv and B is a magnetic flux
density vector of the same. When J and B are constant over the entirevolume V (m3) of the
working part where magnetic fie1d and electric current interact, can be expressed by the
fol1owing formula
F = J X B X V (N)
6. MHD propulsion thruster
Thruster Systems
The magnetohydrodynamic (MHD) thruster system for ships with superconducting
electromagnets has been recognized as its potentially attractive performance. Namely, it does not
need any rotating part like conventional propellers or water jet propulsions, and therefore may
be less affected by cavitations, which would be suitable propulsion means for high speed ships
and for ships as specially required silent operation. However, it is still considered that the MHD
thruster system has various kind of difficult problems to be resolved before it could reach
the level of practical use. The problems may be classified into two categories, which are the
technology specifically concerning physical phenomena of superconductors and practical
technique which examines possibility for designing and constructing MHD thruster systems.
This investigation concerns with the later kind of problems. It is considered that MHD thrusters
can be designed
7. MHD propulsion thruster
Thruster types
Inner ducting type âA thruster duct is Installed in the lower hull of a SWATH, which
Accelerates seawater for generating thrust force. Two saddle type superconducting coils and
electrodes Installed in the duct generate electromagnetic fields.
8. MHD propulsion thruster
Annular ducting type âSuperconducting Magnets are composed of several segments which are
installed surrounding the lower hull of a SWATH .The magnets and electrodes form an annular
ducting surrounding the lower hull ,Which generate electromagnetic fields .
9. MHD propulsion thruster
Pod mount type âTwo pods of thrusters are installed at both sides of the lower hull of a
SWATH Type ship .Their configuration is similar to a inner Ducting type thruster.
10. MHD propulsion thruster
YAMATO 1
"YAMATO 1" is the first superconducting electro-magneto hydrodynamic (MHD)
propulsion ship in the world. This ship was developed by Mitsubishi Corporation. The ship was
designed to be propelled by directly using magneto hydrodynamic force generated by sending
electric current through a magnetic field created in seawater by superconducting magnets.
"YAMATO 1" is a ship built for the purpose of verifying possibilities of actualizing
superconducting MHD propulsion ships. A committee named Super conducting MHD
Propulsion Ship R&D Committee was organized by the Ship & Ocean Foundation and had and
operation as compared with conventional propulsion systems...
11. MHD propulsion thruster
GENERAL ARRANGEMENT OF YOMATO 1
In place of a propeller or paddle wheel, Yamato 1 uses jets of water produced by a magneto
hydrodynamic (MHD) propulsion system. Inside each thruster, the seawater flows into six
identical tubes, arranged in a circle like a cluster of rocket engines. The ten inch diameter
tubes are individually wrapped in saddle shaped superconducting magnetic coils made of
niobium titanium alloy filaments packed into wires with copper cores and shells. Liquid
helium cools the coils to â452.13°F, just a few degrees above absolute zero, keeping them in
a superconducting state in which they have almost no resistance to electricity. Electricity
flowing through the coils generates powerful magnetic fields within the thruster tubes. When
an electric current is passed between a pair of electrodes inside each tube, seawater is
forcefully ejected from the tubes, jetting the [craft] forward.
16. MHD propulsion thruster
Outline of propulsion system
The propulsion systems are composed of superconducting magnets, persistent current switches,
helium refrigerator units, seawater pipes electrodes, etc. and each one set of these systems is
arranged on the port and starboard sides of the ship respectively. The superconducting magnets
are of a six-linked ring construction with six saddle type superconducting coils being arranged on
a concentric circle in a helium vessel. The leakage of magnetic field around magnets are made
small as much as possible by mutually combining magnetic fluxes of each coil. The seawater
pipes are blow passages of seawater through the hull and are subjected to seawater pressure and
electromagnetic force. Furthermore, the seawater pipes are required to be with a good insulating
character against electricity in order to hold electrodes and bus bars for sending electric current.
For these reasons, the seawater pipes are made of epoxy resin GFRP.
Outline of shore support base
Because the superconducting magnets are to be operated in a persistent current
mode during navigation, no facilities are required onboard for initial cooling of
the superconducting MHD propulsion system from room temperature to the liquid
helium temperature and for magnetization and demagnetization. Therefore, these
facilities are installed ashore and it has been planned to reduce the weight of
"YAMATO 1'' and to simplify the propu1sion system onboard.
17. MHD propulsion thruster
Advantages
âą The thruster contains no moving part in propulsion system
âą It works on MHD technology
âą It can be used for making ships and sub marines
âą It is pollution free
âą It produces no noise ,so it is used for warfare
18. MHD propulsion thruster
Conclusion
The Magneto Hydro Dynamic (MHD) propulsion thruster is designed to use magneto
hydrodynamic force generated by sending electric current through a magnetic field created in sea
water by superconducting magnets. When electric current is sent to sea water at right angles to
the magnetic field, and electromagnetic force (Lorentz force) acts on sea water in the direction
perpendicular to both the direction of magnetic field and that of electric current. Propulsion force
is gained as a reaction force of this Lorentz force.MHD propulsion is very advantageous as
it consists of no moving parts and it is pollution free. In the near future this propulsion device
will be used over the conventional propulsion devices.
