The document summarizes thermal ionization in MHD generators. An MHD generator directly converts heat energy to electrical energy using a hot ionized gas and magnetic fields, without needing a conventional electric generator. It consists of a combustion chamber that ionizes a working fluid at high temperatures, and a generator chamber containing magnets and electrodes. The ionized gas enters the generator chamber and its motion through the magnetic field generates a current perpendicular to both fields that is conducted through the electrodes to an external load. MHD generators have efficiencies around 50-60% and no moving parts, but require very high operating temperatures around 2000-2400°K.

1. Thermal ionization in MHD
generator
PRAVEEN KR. KUSHWAH
ROLL NO.-104074
S.NO.-105

2. INTRODUCTION
 The word Magneto Hydrodynamics (MHD) is derived as magneto- means magnetic field, and
hydro- means fluid and dynamics- means movement.
 The field of MHD was initiated by Hannes Alfven, for which he received the Nobel Prize in
Physics in 1970.
 An MHD generator is a device used for converting heat energy of a fuel directly into
electrical energy without a conventional electric generator.
 In this system, the hot ionized gaseous conductor (working fluid) is passed into the high
magnetic field and there by the current is produced. By placing suitable electrodes
(Anode and cathode) inside the chamber, the output load is taken through the external
circuit.

3.  MHD generator consist of a Combustion chamber and generator
chamber.
 The fluid conductor is passed into the combustion chamber where
they are ionized at very high temperature.
 There is a nozzle through which the ionized gas pass into the
generator chamber.
 The generator chamber consist of powerful magnet and a
number of oppositely located electrode pair is inserted in the
channel to conduct the electrical current generated to an
external load.
 Both combustion chamber and generator chamber are surrounded
by a heat resistance material and water cooler.
Construction

4. S
N
combustion
Chamber VIonized Gas
Working
fluid
Water cooler
Thermal resistance sealing
Magnet
Stream out
Load
output
Nozzle
Electrode
Inlet

5. Working
 The gaseous (fluid) conductor is passed into the combustion chamber through
inlet.
 By using a fuel like oil (or) natural gas (or) coal, the fluid conductor is heated
to a plasma state and hence it is ionized.
 The temperature in the combustion chamber is around 2000°K to 2400°K.
 The heat generated in the combustion chamber removes the outermost
electrons in the fluid conductor.
 Therefore, the gas particle acquires the charge

6. Working contd..
 The charged gas particles with high velocity enters into the generator
chamber via nozzle.
 The positive and negative charge moves to corresponding electrodes
(anode and Cathode) and constitute the current.
 In generator chamber, based principles of Faraday’s law, the high velocity
ionized conducting gas particles experience the magnetic filed at right
angles to their motion of direction and hence the potential (current) is
produced.
 The direction of current (Potential) is perpendicular to both the
direction of moving gas particle and to the magnetic field.

7. Working contd..
• The diagram shows the direction of
charged particle, magnetic field and the
current produced
• All three field are perpendicular to each
other

8. Working contd..
 The electrodes are connected to an external circuit to get a load output.
 The current produced in the MHD generator are direct current (DC)
 This DC current can be converted into alternative current (AC) using an
inverter attached with the external circuit.
 In MHD generator, the seeding materials such as potassium and cesium
are used to reduce the ionization temperature.
 These seeds are mixed with fuel material such as natural gas and coal.

9. Working contd..
 The overall efficiency of MHD generators are about 50 to 60 %.
 The electrode are made generally using high temperature ceramic
materials such as carbides (SiC, ZrC, MbC), bromides (ZrB2, TiB2,
LaB2) and silicides (WS and MOSi2 ).

10. Advantages, Disadvantages and Applications
Advantages:-
 The efficiency of MHD can be around 50 % as compared to 40% for the most
efficient steam plants. Still higher thermal efficiencies(60-65%) are expected
in future.
 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 it is started.
 The size of the plant is considerably small then conventional fossil fuel plants.

11. Advantages contd..
 Capital cost of MHD plants will be competitive than conventional steam plants.
 Direct conversion of heat into electricity permits to eliminate the gas turbine or
both the boiler and the turbine, so the energy losses are minimized.
 These system permit better fuel utilization.
 It is possible to utilize MHD for peak power generation and emergency services.

12. Disadvantages:-
 They need high pure superconductor.
 Working temperature is very high as about 2000°K to 2400°K.
 The loss of power if very high.
 The components get high corrosion due to high working
temperature.

13. Application:-
 The MHD generators are used to power submarines and
aircrafts.
 Electrical power production for domestic applications
 They can be used as power plants in industry and
uninterrupted power supply system

15. REFERENCES:-
Non-Conventional Energy Sources By G.D. Rai
http://www.mpoweruk.com/mhd_generator.htm