PPT 2 NOT FOR USE

7/31/2019 PPT 2 NOT FOR USE

1/22

PREPARED BY:

PRASHANT S. PATEL

M.E(ELECTRICAL 1st SEM)

ROLL NO:- 26

MAGNETO HYDRO DYNAMIC

SYSTEMS


2/22

CONTENTS:

INTRODUCTION

PRINCIPLE

BASIC CONCEPT

COMPONENTS OF MHD SYSTEM POWER DEVELOPED IN MHD SYSTEM

ADVANTAGES

LIMITATIONS

ITS FUTURE PROSPECTS


3/22


4/22


5/22


6/22

PRINCIPLE:

MHD generator works on Faradays laws ofelectromagnetic induction.

When a conductor moves in a magnetic fieldsuch that it cuts the field,emf is induced in theconductor.Current flows if the circuit iscomplete.

In MHD generator,conducting gas is usedinstead of solid conductor.


7/22

PRINCIPLE OF MHD POWER

GENERATION

When an electric conductor moves across a magnetic field, avoltage is induced in it which produces an electric current.

This is the principle of the conventional generatorwhere theconductors consist of copper strips.

In MHD generator, the solid conductors are replaced by agaseous conductor; an ionized gas. If such a gas is passed at ahigh velocity through a powerful magnetic field, a current isgenerated and can extracted by placing electrodes in a suitableposition in the stream.

The principle can be explained as follows. An electric conductormoving through a magnetic field experiences a retarding force aswell as an induced electric field and current.


8/22

PRINCIPLE OF MHD POWER

GENERATION


9/22

The electromagnetic induction principle is not limited to solidconductors. The movement of a conducting fluid through amagnetic field can also generate electrical energy.

when a fluid is used for the energy conversion technique , it iscalled the MAGNATO HYDRODYNAMIC (MHD) ,energyconversion.

If the flow directionis right angles to the magnetic field direction ,an electromotive force (or electric voltage ) is induced in thedirection at right angles to both flow & field directions, as shown inthe next slide


10/22

The conducting flow fluid is forced between the plates with akinetic energy & pressure differential sufficient to overcome themagnetic induction force Find.

The end view drawing illustrates the construction of the flowchannel.

An ionized gas is employed as the conducting fluid.

Ionization is produced either by thermal means i.e. by anelevated temperature or by seeding with substance like cesium orpotassium vapours which ionize at relatively low temperatures.

The atoms of seed element split off electrons. The presence ofthe negatively charged electrons makes the carrier gas anelectrical conductor


11/22

Thus the MHD systems can be classified broadly as

follows :

1) Open Cycle System.

2) Close Cycle System.

a) Seeded Inert Gas system

b) Liquid Metal System.


12/22

OPEN CYCLE SYSTEM :


13/22

Fuel used may be oil through an oil tank orgasified coal througha coal gasification plant.

The fuel ( coal, oil or natural gas) is burnt in the combustororcombustion chamber.

The hot gases from combustor is then seeded with a smallamount of an ionized alkali metal(cesium orpotassium) toincrease 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 hotcombustion gases at temperature of roughly( 2300-2700c)


14/22

To attain such high temperatures, the compressed airused to burn the coal in the combustion chamber, mustbe adequate to at least 1100c. A lower preheattemperature would be adequate if the air whereenriched in oxygen. An alternative is to usecompressed oxygen alone for combustion of fuel, littleor no preheating is then required. The additional costof the oxygen might be balanced by saving on thepreheater.

The hot pressurized working fluid living the combustorflows through the a convergent divergent nozzle. Inpassing through the nozzle, the random motion energyof the molecules in the hot gas is largely converted into

directed, mass of energy. Thus, the gas emerges fromthe nozzle and enters the MHD generator units at ahigh velocity.


15/22

The MHD generator is divergent channelmade of a heatresistantalloy with external water cooling. The hot gas expands throughthe rocket like generator surrounded by power full magnet. Duringmotion of the gas the +ve andve ions move to the electrodesand constitute an electric current.

The arrangement of the electrode connections is determined bythe need to reduce losses arising from the Hall effect. By thiseffect, the magnetic field acts on the MHD-generated current andproduces a voltage in flow direction of the working fluid ratherthan at right angles to it.


16/22

CLOSED CYCLE SYSTEM :


17/22

Two general types of closed cycle MHD generators arebeing investigated.

1. electrical conductivity is maintain in the working fluid byionization of a seed material, as in open cycle system

2. a liquid metal provides the conductivity.

The carrier is usually a chemical inter gas, all though aliquid carrier is been used with a liquid metal conductor.The working fluid is circulated in a closed loop and isheated by the combustion gases using a heat exchanger.

Hence the heat sources and the working fluid areindependent. The working fluid is helium or argon withcesium seeding


18/22

Because the combustion system is separate from the working

fluid, so also are the ash and flue gases. Hence, the problem ofextracting the seed material from flyash does not arise. The fuelgases are used to preheat the incoming combustion air and thentreated for fly ash and Sulfur dioxide removal, if necessary priorto discharge through a stack to the atmosphere.

The loop in the centre is the MHD loop. The hot argon gas isseedingwith cesium and resulting working fluid is passedthrough the MHD generator at high speed. The dc power out ofMHD generator is converted in ac by the inverter and is then fedinto the grid.


19/22

ADVANTAGES OF MHD SYSTEMS

1) The conversion efficiency of an MHD system can be around 50 percent as compared to less then 40 per cent for the most efficientsteam plants. Still higher thermal efficiencies(60-65%) are expectedin future, with the improvements in experience and technology.

2)

3) Large amount of power is generated.

4) It has no moving parts, so more reliable.

5)

6) The closed cycle system produces power free of pollution.

7) It has ability to reach the full power level as soon as started.

8) The size of the plant (m2/kW) is considerably smaller thenconventional fossil fuel plants.


20/22

APPLICATION:-

Power generation in space craft.

Hypersonic wind tunnel experiments.

Defense application.


21/22

CONCLUSION:- The MHD power generation is in advanced stage

today and closer to commercial utilizationsignificant progress has been made indevelopment of all critical component and sub

system technologies coal burning MHD combinedsteam power plant promise significant economicand environmental advantages compared to othercoal burning power generate technologies. It willnot be long before the technological problem of

MHD generate are overcome and MHD powergeneration transform itself from non-conventionalto conventional energy sources.


22/22

REFERENCE :

NON-CONVENTIONAL ENERGY SOURCES BYG.D.RAI

Documents

PPT 2 NOT FOR USE