Mhd Final

PROJECT NO. 1

MAGNETOHYDRO DYNAMIC GENERATORS

GROUP MEMEBERS Avn Cdt Sgt Umer 066940 Avn Cdt Sohaib 066933 Nust Cdt Hassan 060901

CONTRIBUTIONS

SEQUENCE OF PRESENTATION HISTORY THEORY OF MHD GENERATORS INTRODUCTION TO MHD GENERATORS TYPES OF MHD GENERATORS DESIGN SIZING ONLINE MARKET RESEARCH(BOTH LOCAL AND

INTERNATIONAL) PRICING.

SUITABLE APPLICATIONS BOTH IN AND OUT OF

AVIATION INDUSTRY. FEASIBILTY REPORT COST BENEFIT ANALYSIS CONCLUSION REFERENCES BOOKS AVAILABLE IN LIBRARY

HISTORY It was Faraday who recognized in 1831 that

one could employ a fluid conductor as the working substance in a power generator. Thus giving the concept of MHD generator. The first practical MHD power research was funded in the 1938 in the U.S. in Pittsburg, Pennsylvania laboratories, headed by Bela Karlovitz. In the United States, operation of a 32 MW alcohol-fueled generator with run times up to three minutes was achieved in 1965

HISTORY In 1966 IAEA (International Atomic Energy

Agency) started funding MHD projects as it anticipated that nuclear reactors could use MHDs exhaust to supply the high temperature required for fission. In the Soviet Union tests on a 75 MW (25 MW from MHD and 50 MW from steam) pilot plant burning natural gas began in 1971 In 1976 as it became clear that MHDs couldn’t be used in Nuclear Reactor IAEA withdrew its support. Resulting in a huge setback for MHD research.

HISTORY In 2004 a combined MHD and Steam plant was

established in Tennessee, USA which could produce 300MW.

PRINCIPLE OF ELECTRICITY GENERATION

According to faraday’s law, when an

electrical conductor is moved so as to cut lines of magnetic induction, the charged particles in the conductor experience a force in a direction mutually perpendicular to the B field and to the velocity of the conductor. The negative charges tend to move in one direction, and the positive charges in the opposite direction. This induced electric field, or motional emf, provides the basis for converting mechanical energy into electrical energy.

In commonly used generators…………

In the case of hydroelectric generators, the energy required

to maintain the rotation of turbine is supplied by the gravitational motion of river water. While in Turbo generators, a high-speed flow of steam or other gas moves the turbine. The heat source required to produce the high-speed gas flow may be supplied by the combustion of a fossil fuel or by a nuclear reactor (either fission or possibly fusion).

However in an MHD generator……..  We don’t have any moving parts. In this generator instead of a moving metal conductor (armature) we have a fast flowing conducting fluid. (mostly an ionized gas) A current is induced in the conducting fluid due to the cutting of magnetic flux by the fast flowing conducting fluid. The current then passes through the electrodes in the channel wall to an external

How gases are made electrically conductive?  Raising the gas to a very high temperature.

By adding a small amount

of easily ionized substance. This process is called seeding. (e.g. iodine-125, potassium ionization seed)

Raising the gas to a very high temperature

A seeder used to ionize gas.

Schematic Diagram of a combined MHD and Steam

Explanation First the air enters into a compressor from

where it enters the low temperature air heater. Next the air after passing through the high temperature heater enters the combustion chamber where it is seeded so that it’ll ionize. The ionized high speed gas then passes through the MHD and a DC power is generated. The high temperature gas exiting from the MHD is fed into the Steam generator where it drives the turbine to generate AC power.

TYPES OF MHDS

OTHER SHAPES OF MHD GENERATOR

DESIGN Important Design Characteristics: The

need to obtain sufficient electrical conductivity. The need to produce high magnetic field. The need to obtain permanent duct walls. The need to provide long lived electrode.

THE NEED TO OBTAIN SUFFICIENT ELECTRICAL The

electrical conductivity increases by ionizing a low density gas.

In order to increase the

electrical conductivity above 10 mhos/m* we need to increase the temperature. This high temperature is obtained from the burning of fossil fuel while the exit temperature of the nuclear *mhos is the unit of electrical conductance now Siemens is used instead. plant gases isn’t sufficient.

THE NEED TO OBTAIN SUFFICIENT ELECTRICAL

It has been suggested that the use of certain

solid particles in the gas like carbon can increase electrical conductivity as they emit electrons.

THE NEED TO PRODUCE HIGH MAGNETIC FIELD.

The large magnets required for the MHD

generator are the most expensive part of the MHD generator. Permanent magnets are generally not used as they are weak and bulky. Superconducting magnets are preferred as they have high magnetic field strength of up to 6weber/m2 and current densities of up to 200 Mega amps/m2. e.g Niobium Zirconium. In electromagnets the number of windings over the magnetic material is increased to increase the magnetic field.

THE NEED TO OBTAIN PERMANENT DUCT WALLS

The high temperature ionized gas mixed with seeds

of alkali metal produce a very corrosive environment. Therefore such a material is required which can withstand corrosion and remain an electric insulator at these high temperatures. And is also a thermal insulator. MgO and Strontium zirconate, which are commonly used as refractory materials could only run for 1 hour before being corroded. New materials such as Yttrium and Zirconium dioxide are now used which can stand upto a

THE NEED TO PROVIDE LONG LIVED ELECTRODE

Electrodes serve as a contact with the working

fluid As the ionized gas is at a very high temperature it is necessary that the electrode should be able to withstand this high temperature. A material should be selected which doesn’t form a layer of oxide on the outer surface which will reduce its conductivity. Tungsten is commonly used.

SIZING

MHDs vary in size with

the smallest generating about 20W. The largest built in Tennessee, US uses a 40ton superconducting magnet capable of generating MHD electricity of 250 MW capacity followed by a conventional 300 MW steam turbine generator powered by the exiting hot gases.

PICTURES OF A JAPANESE MHD CAPABLE OF

ONLINE MARKET RESEARCH INTERNATIONAL: MHD

Generators are still going through research phase. Therefore, at present, there is no demand for MHDs as governments and industries prefer to install other types of generators (e.g. diesel or gas ) as they are low in cost and high in efficiency. Moreover, no company is directly associated with production of MHD generators and most of the research and development is made by University professors and students.

ONLINE MARKET RESEARCH Universities that have significantly contributed in the research of MHDs are:  University

of Tennessee Space Institute  Princeton University  University of Bologna, Italy  University of Alabama  The Institute of Electrical Engineering in the Academica Sinica, Beijing An MHD generator made by students of university of Bologna. A student of UTSI working on MHD generator.

ONLINE MARKET RESEARCH LOCAL: Locally no major research on MHDs is in

progress in Pakistan. Although students of some local universities like COMSAT and University of Peshawar have done some research on MHDs their work is merely theoretical and no practical MHD generator has been made in Pakistan to date.

PRICING As

MHD generator is still under experimentation therefore no data regarding its cost was available. Experimental costs usually exceed the production cost and therefore these costs haven’t been quoted.

APPLICATIONS BOTH IN AND OUT OF AVIATION INDUSTRY

 The basic mechanism behind aircraft

propulsion is the emission of high velocity gas from the aircraft nozzle. which produces the thrust.  According to new research a supersonic aircraft can use a MHD generator and ramjet engine configuration connected in series to produce high velocity exhaust.  The supersonic MHD generator and ramjet engine configuration increase the power output and improve the operating efficiency of the electrical generating system.

A diffuser system is also proposed which is in fluid

communication with the supersonic MHD generator and the ramjet engine for collecting bypass plasma gas to be used for heating a second radiant boiler adapted for powering a steam turbine generator. However, the main obstacle in the use of MHDs is the requirement of huge magnets which would considerably increase the weight of the aircraft which is undesirable. At the other hand, electromagnets can’t be used as the power required to produce such a large amount of electricity can’t be generated on flight.

Future prospects In submarines, low speed

MHD generators using liquid metals would be nearly silent, eliminating a source of tell-tale mechanism noise. “Yomoto”: a boat built by

Mitsubishi powered solely by MHD propulsion YOMATO Can travel at up to 15 km/hr

USE IN SPACE INDUSTRY In

spacecraft and unattended locations, low-speed metallic MHD generators have been proposed as highly reliable generators, linked to solar or nuclear heat sources. Studies are being conducted on an innovative space power system that combines a uranium tetrafluoride (UF4) ultrahightemperature vapor core reactor (UTVR) and a disk magnetohydrodynamic (MHD) generator to generate power (hundreds of MWe power level for a few thousand seconds which can

USE IN SPACE INDUSTRY This allows for operation on a direct, closed-

Rankine-type cycle and leads to space power systems with high efficiency (≈20%) and small radiator size.

COST BENEFIT ANALYSIS BENEFITS: MHD generators can operate at high temperatures without moving parts. Thus reducing loss in power due to friction. MHD exhaust of a plasma MHD generator is a flame, still able to heat the boilers of a steam power plant. Reduction in fuel cost. Conservation of natural resources.

COST BENEFIT ANALYSIS COST: MHD generators have not been employed for large scale mass energy conversion because other techniques with comparable efficiency have a lower investment and operating cost. A certain amount of electricity is required to maintain sustained magnetic field over 1 T. which increases the cost.

COST BENEFIT ANALYSIS COSTS: Because of the high temperatures, the walls of the channel must be constructed from an exceedingly heat-resistant substance such as yttrium* oxide or zirconium* dioxide to retard oxidation. These materials are extremely expensive. Similarly, the electrodes must be both conductive and heat-resistant at high temperatures, making tungsten* a common choice rather than copper which is much cheaper. * Yttrium $4000/kg. Zirconium $150/kg , Chromium carbide (Cr3C2 ) $90/kg Tungsten $25 / kg Copper $2.93 / kg .

COST BENEFIT ANALYSIS

However……. The exhaust of an MHD generator is almost as

hot as the flame of a conventional steam boiler. By routing its exhaust gases into a boiler to make steam, MHD and a steam Rankine cycle (combined cycle) can produce electricity with an estimated efficiency of up to 60% experimental value), compared to the 40 percent of a typical coal plant.

Optimum performance of MHD Studies show that the generator with contoured disk walls achieves higher performance than the generator with straight disk walls because of improved flow behavior. The optimal magnetic field on duct-shaped MHD generators is a sort of saddle shape. An optimum theoretical temperature between 2500 to 4000K is suggested for higher efficiency. A disk type MHD generator is known to have a higher efficiency than other types.

CONCLUSION Although

MHD generator are environment friendly However, their low efficiency combined with high cost and low power capacity make it an unfavorable option compared to other methods of power production. In the coming years, as long as fossil fuels, are available MHD Generators are not feasible for power production. MHD Projects need desperate funding if they have to compete with other renewable source power generators like wind, solar or

REFERENCES www.utsi.edu/news/News_2005 www.answers.com www.wikipedia.en www.es.titech.ac.jp/yamasaki www.daimler.com www.itsf.org  www.mhdonline.sal.lv www.sciencelinks.jp www.cv.nrao.edu www.bookrags.com www.ieee.org/papers

BOOKS AVAILABLE IN LIBRARRY Magneto hydrodynamics by T G Cowlings MHD Generation of electric power by R.A.

Coombe Magneto hydrodynamics by P.C. Kendall Engineering aspects of engineering by Gordon & Breach. Magneto hydrodynamics; historical evolution and trends. S. Molokov Engineering thermodynamics by J.B Jones

FOLLOWING ARTICLES ARE

PATENTED AVAILABLE

MHD Technology for Scramjet Control The Constant-Mach-number MHD generator On a Perspective of MHD Technology in Aerospace

Applications Parametric study of potential early commercial mhd power plants Investigation of a Mach 3 Cold Air MHD Channel Solar-powered liquid-metal MHD power systems Magneto hydrodynamic Power Extraction from Cold Hypersonic Air with External Ionizers