MAGNETO HYDRODYNAMIC PROPULSION
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Joined: Feb 2011
02-03-2011, 03:56 PM
AKHIL K DAS
RAJIV GANDHI INSTITUTE OF TECHNOLOGY.ppt (Size: 521.5 KB / Downloads: 213)
The magnetohydrodynamic propulsion is a new propulsion system which is used for propelling ships & submarines.
The magnetohydrodynamic, or MHD, propulsion has no moving parts like propeller, gear, shafts etc
Submarines fitted with it , cannot be detected easily
(as it is silent)
First proposed by W A Rice in 60’s in USA
He does experimental work on it using dc direct drive propulsion using battery driven magnets
Speed 1.5 knots against design goal was 1
Earlier research faded as efficiency achieved was marginal using available magnetic technologies
In 70’s research started using supermagnets in Japan
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 hull
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)
J is a current density vector of infinitesiml volume dv
B is a magnetic flux density vector
When J and B are constant over the entirevolume V (m3)
F = J X B X V (N)
Case study- “YAMANTO 1” Mhd ship
The first prototype based on mhd technology was ‘YAMANTO 1’
Made by mistubushi in 1990,weighing 184 tons, traveled at 15 km/hr
It uses a 4 tesla superconducting magnet
Electrodes are titanium with anode coating of DSA & cathode plated with platinum.
Electrode length 3.4m
Superconducting magnets are operated in persistent current mode during navigation
No onboard facilities for initial cooling
It had a shore support base
Initial Cooling,Magnetization & demagnetization are done there
It reduced the weight
Cooling of superconducting coil from room temperature to about 20K is done by passing G He
Cooling from 20K-4K is done by using
L He filling
L He filling was done by connecting L He reservoir to the L He filling port of the large He refrigerator on shore.
Magnetization & de magnetization
The persistent current switch (PCS) is of a thermal type ,turns OFF position when sending current and to the ON position when stop sending current to the PCS heater
For magnetization, the PCS is to be set at the OFF position
PCS is to be switched to the ON position when the current has reached the predetermined value
It is found by Bollard test
Ship moored to a quay by mooring lines fitted with tension meters.
electric current was sent between the electrodes and the generated pull force and pressure in the thruster duct were measured
Bollard pull force , Lorentz force and thrust force increase proportionally to increase of electrode current.
Texp is greater than Tcal
This is due to experimental error
Otherwise measured results agree with calculation
It has no moving parts (no motors, gears ,shafts) - QUIET OPERATION
high speed due to the absence of a cavitation limit
high efficiency due to the nearly direct conversion of electrical energy into KE
Less demand for fuel
These systems use high magnetic fields, which require the use of cryogenically cooled superconducting coils –increases cost
'Acoustic Signature' –electrolysis off sea water produces visible wake
MHD ships & Subs has a great future because of its silent and high speed performance
For its development more research on superconducting magnets and its subsystems are necessary