Principle, MHD system, open cycle system, closed cycle system, design problems & developments, advantages, materials for MHD generators, magnetic field & super conductivity

1. DEPARTMENT OF CHEMICALENGINEERING
CHAPTER-12
“Magneto HydroDynamic
(MHD) Power
Generation”
PROF. DEVARSHI P. TADVI
ASSISTANT PROFESSOR
CHEMICAL ENGINEERING
DEPARTMENT
S S AGRAWAL INSTITUTE OF
ENGINEERING & TECHNOLOGY,
NAVSARI

2. Contents
• Introduction
• History
• Principle of MHD
• Various System of MHD
1. Open Cycle
2. Close Cycle
• Difference between Open Cycle And Close Cycle
• Advantages
• Limitations
• Problems And Development
• Future Porpose
• Conclusion

3. INTRODUCTION
• Magneto hydrodynamics (MHD)
(magneto fluid dynamics or hydro
magnetics) is the academic discipline
which studies the dynamics of
electrically conducting fluids.
• Examples of such fluids include
plasmas, liquid metals, and salt water.
• The word magneto hydro dynamics
(MHD) is derived from magneto-
meaning magnetic field, and hydro-
meaning liquid, and dynamics-
meaning movement.
• The field of MHD was initiated by
Hannes Alfvén, for which he received
the Nobel Prize in Physics in 1970
HannesAlfvén

4.  An MHD generator is a device for converting heat energy
of a fuel directly into electrical energy without a
conventional electric generator.
 It is a new system of electric power generation which is said to
be of high efficiency.
 Also it causes low pollution.
 Situated at Trichi in Tamil Nadu.
BARC (Bhabha Atomic Research Centre)
BHEL
Associated Cement Corporation(ACC)And
Russian Technologists

5. HISTORY OF MHD
 It was introduced by Michael
Faraday in 1832 in his Bakerian
Lecture.
 He carried out a experiment at
Waterloo Bridge in UK for
measuring the current, from the
flow of river Thames in Earth’s
Magnetic Field.
 Over the years then the first MHD-
Generator was built in 1959 in USA
 The first MHD power Plant was
constructed in USSR in 1970

6. PRINCIPLES OF MHD POWER GENERATION
• When an conductor moves across a magnetic field, a
voltage is induced in it which produces an electric current.
• This is the principle of the conventional generator where the
conductors consist of copperstrips.
• In MHD generator, the solid conductors are replaced by a
Gaseous conductor, an ionized gas. If such a gas is passed at a
high velocity through a powerful magnetic field, a current is
generated and can be extracted by placing electrodes in
suitable position in thestream.
• The principle can be explained as follows: An conductor
moving through a magnetic field experiences a retarding force
as well as an induced electric field and current
• The flow direction is right angles to the magnetic fields
direction. An electromotive force (or electric voltage) is
induced in the direction at right angles to both flow and field
directions.

7. • The conducting flow fluid is forced
between the plates with a kinetic energy
and pressure differential sufficient to over
come the magnetic induction force.
• An ionized gas is employed as the
conducting fluid.
• Ionization is produced either by
thermal means i.e. by an elevated
temperature or by seeding with
substance like cesium or potassium
vapors which ionizes at relatively
low temperatures.
• The atoms of seed element split off
electrons. The presence of the
negatively charged electrons makes the
gas an electrical conductor.
• The end view drawing illustrates the
construction of the flow channel.

8. VARIOUS MHD SYSTEMS
 The MHD systems are broadly classified into two types.
• OPEN CYCLE SYSTEM
• CLOSED CYCLE SYSTEM
1. Seeded inert gas system
2. Liquid metal system

9. OPEN CYCLE SYSTEM
• The fuel used maybe oil through an oil tank or gasified
coal through a coal gasification plant.
• The fuel (coal, oil or natural gas) is burnt in the combustor or
combustion chamber.
• The hot gases from combustor is then seeded with a
small amount of ionized alkali metal (cesium or potassium)
to increase the electrical conductivity of the gas.
• The seed material, generally potassium carbonate is injected
into the combustion chamber, the potassium is then ionized by the
hot combustion gases at temperature of roughly 2300 ˚C to 2700 ˚C.
• To attain such high temperatures, the compressed air is used to
burn the coal in the combustion chamber, must be adequate to at
least 1100 ˚C.
• The hot pressurized working fluid living in the combustor
flows through a convergent divergent nozzle. In passing through the
nozzle, the random motion energy of the molecules in the hot gas is
largely converted into directed, mass of energy. Thus , the gas
emerges from the nozzle and enters the MHD generator unit at a
high velocity.

10. CLOSED CYCLE SYSTEM
• Two general types of closed cycle MHD generators are
being investigated.
• Seeded Inert Gas System
• Liquid Metal System

11. 1. SEEDED INERT GAS SYSTEM
• In a closed cycle system the carrier gas
operates in the form of Brayton cycle. In a
closed cycle system the gas is compressed
and heat is supplied by the source, at
essentially constant pressure, the
compressed gas then expands in the MHD
generator, and its pressure and temperature
fall.
• After leaving this generator heat is removed
from the gas by a cooler, this is the heat
rejection stage of the cycle. Finally the gas
is recompressed and returned for reheating.

12. LIQUID METAL SYSTEM
• When a liquid metal provides the electrical
conductivity, it is called a liquid metal MHD
system.
• The carrier gas is pressurized and heated by passage
through a heat exchanger within combustion
chamber. The hot gas is then incorporated into the
liquid metal usually hot sodium or Lithium to form
the working fluid.
• The working fluid is introduced into the MHD
generator through a nozzle in the usual ways.
The carrier gas then provides the required high
direct velocity of the electrical conductor.

13. DIFFERENCE BETWEEN OPEN
AND CLOSED CYCLES
OPEN CYCLE SYSTEM
• Working fluid after generating
electrical energy is discharged to
the atmosphere through a stack.
• Operation of MHD generator is
done directly on combustion
products
• Temperature required is
about 2300˚C to 2700˚C
• More developed
CLOSED CYCLE SYSTEM
• Working fluid is recycled to the
heat sources and thus is used
again
• Helium or Argon(with
Cesium Seeding) is used as
the working fluid.
• Temperature required is
about 530˚C
• Less developed

14. • The conversion efficiency of a MHD system can be around
50% much higher compared to the most efficient steam
plants.
• Large amount of power is generated.
• It has no moving parts, so more reliable.
• The closed cycle system produces power, free of pollution.
• It has ability to reach the full power level as soon as started.
• The size of the plant is considerably smaller than
conventional fossil fuel plants.
ADVANTAGES

15. LIMITATIONS
• The metallic vapours are poor electrical conductors.
• High velocities cannot be obtained by expansion in the system
while it is much easier to achieve a high fluid velocity .
• employing a gas and a nozzle. This is because the liquids are
practically in compressible.
• The overall conversions efficiencies obtainable with liquid
metal system are quite below to that of plasma system.

16. • Laser power MHD Generators.
• Plasma physics applications.
• Power generation in space crafts.
• Hypersonic wind tunnel experiments.
• Defense applications.
APPLICATIONS

17. MHD DESIGN PROBLEMS AND DEVELOPMENTS
Problems Developments

18. FUTURE PROSPECTS
• It is estimated that by 2020, almost 70 % of the total
electricity generated in the world will be from MHD
generators.
• Research and development is widely being done on
MHD by different countries of the world.
• Nations involved:
1. USA
2. Former
3. USSR
4. Japan
5. India
6. Chin
7. Yugos
8. Avia
9. Austraia
10. Italy
11. Poland

19. REFERANCES
• http://www.wikipedia.org
• Faraday, M. (1832). "Experimental Researches in Electricity." First
Series, Philosophical Transactions of the Royal Society, pp. 125–162.
• Sutton, George W., and Sherman, Arthur (1965)
Engineering Magnetohydrodynamics, McGraw-Hill Book
Company, New York, OCLC 537669
• Popa, C. and Sritharan, S. S. (2003) "Fluid-magnetic splitting
methods for magneto-hydrodynamics" Mathematical Methods and
Models in Applied Sciences 13(6): pp. 893–917.
• Roberts, Paul H. (1967) An Introduction to Magnetohydrodynamics
Longmans Green, London, OCLC 489632043
• Rosa, Richard J. (1987) Magnetohydrodynamic Energy
Conversion (2nd edition) Hemisphere Publishing,
Washington, D.C., ISBN 0-89116-690-4

20. THANK YOU…
Life Is Not For Living It,
It’s Making It.