diesel power plant from slide share

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Diesel Power Plant olarLounge

Nishkam Dhiman

Asst Prof : Electrical and Electronics Engineering

Chitkara University, Punjab



Introduction• Diesel power plants produce power in the range of 2 to 50 MW,

are used as central stations for supply authorities and work.

• They are used as standby sets for continuity of supply such as

hospitals, telephone echanges, radio stations, cine!a theatresand industries.

• They are suitable for !obile power generation and widely used inrailways and ships.

• "sed as #eak $oad #lants, Mobile #lants, %tand &y "nits,'!ergency #lants, %tarting %tations, (entral %tations, )ndustrieswhere power re*uire!ent is s!all 500kW.



• +dantages of Diesel power plant -• )t can respond to arying loads without any difficulty.

• )t occupies less space.

• or the sa!e capacity diesel power plant is co!pact and s!aller than a ther!alpower plant.

• Diesel power plants are !ore efficient than stea! power plants in the range of/50 MW capacity.

• Disadantages of Diesel power plant -• igh operating cost.

• igh !aintenance and lubrication cost.

• The capacity of a diesel plant is li!ited. They cannot be constructed in largesi1es.

• )n a diesel plant noise is a serious proble!.

• Diesel power plants cannot supply oer loads continuously where as stea!power plants can work under 25 oerload continuously.



Heat Engine: any type of engine or device

that derives heat energy from combustion offuel and converts to mechanical energy.

• In an Internal combustion engine, combustion takesplace within working uid of the engine, thus uid

gets contaminated with combustion products.

• Petrol engine is an eample of internal combustionengine, where the working uid is a miture of airand fuel .

• In an Eternal combustion engine, working uid getsenergy using boilers by burning fossil fuels or anyother fuel, thus the working uid does not come incontact with combustion products.

• !team engine is an eample of eternal combustionengine, where the working uid is steam.



"lassi#cation of I" Engines.

$. %ccording to cycle of operation

• &wo !troke Engine

• 'our !troke Engine

(. %ccording to cycle of combustion

• )tto "ycle Engine*combustion at constant volume+

• iesel "ycle Engine*combustion at constant pressure+

• ual "ombustion or semi - diesel cycle engine.

. %ccording to arrangement of "ylinder.

• Hori/ontal Engine• 0ertical Engine

• 01&ype Engine

• 2adial Engine



3. %ccording to their 4ses

• !tationary Engine

• Portable Engine

• 5arine Engine

• %utomobile Engine

• %ero Engine

6. %ccording to fuel employed and method of fuel supply to theengine.

• )il Engine

• Petrol Engine

• 7as Engine

8. %ccording to method of ignition

• !park ignition

• "ompression ignition



9. %ccording to speed of the engine

• ow speed

• 5edium !peed

• High !peed;. %ccording to method of cooling

• %ir "ooled

• <ater "ooled

=. %ccording to number of cylinders

• !ingle cylinder

• 5ulti "ylinder



%ir "ooled I" Engine



&erms 2elating to I" Engine



'our !troke iesel "ycle Engine



$.!uction !toke: <ith the movement of piston from &" to >",inlet valve opens and air at atmospheric pressure is drawn insidethe engine.*61$+

2. "ompression stroke: It raises pressure to about 6kg?cm(. andtemp 8@@deg ". piston moves from >" to &"*$1(+

. Epansion or <orking !troke: 'uel inAection starts at or nearend of compression stroke. 'uel starts burning at constantpressure. *(1+ High air temperature caused by compressionignites fuel. >urning miture epands, pushing piston down onworking stroke. %t fuel supply is cut. Hot gases epand to point

3 *13+3. Ehaust stroke: &he piston moves from >" to &" and ehaustgases escape to atmosphere through ehaust valve. <hen pistonreaches &" ehaust valve closes and cycle is complete.



P0 diagram of four stroke engine.



&wo !troke Engine

• $ike the four3stroke engine, the two3stroke engine !ust go through the

sa!e four eents- intake, co!pression, power, and ehaust. &ut a two3

stroke engine re*uires only two strokes of the piston to co!plete one full

cycle4crankshaft. igure shows Two %troke #etrol 'ngine, in Deisel 'ngine

there is no spark plug.



• % two stroke engine has a cylinder connected to the closedcrank chamber "". uring upward stroke of the piston 5, thegases in are compressed and at the same time fresh airenters the crank chamber through the valve 0.

• <hen the piston moves downward, 0 closes and air in the ""is compressed.

• &he piston is moving upward and is compressing the air whichhas previously been supplied to and before it reaches the &" the fuel inAector supplies fuel to the engine cylinder.Ignition takes place due to high temp and pressure.

• &hese gases epand and piston then travel downward andnear the end of stroke it uncover the ehaust port.

• Eercise: iBerence between &wo !troke Engine and 'our!troke Engine.



Essential "omponents of iesel

Power Plant



1. Diesel engine :iesel engine is a compression ignition*"I+ engine. It is the main componentwhich develops the reCuired power.

2. Air intake system :

&he air reCuired for the combustion of fuel inside the diesel engine cylinder isdrawn through the air #lter. &he purpose of the #lter is to remove dust from the

incoming air. &he dry #lter may be made of felt, wood or cloth.In wet #lter, oil bath is used. In this the air passes over a bath of oil where thedust particles get coated on the oil.

3. Exhaust System:

&he purpose of ehaust system is to discharge the engine cylinder ehaust tothe atmosphere.

4. Fuel supply system:'uel from the storage tank is pumped through a #lter into a smaller tank calledall day tank. &his tank supplies the daily reCuirements of the diesel engine.

&he all day tank is placed high so that the fuel ows to the engine under gravitywith suDcient pressure.



5. Starting system:

•iesel engine used in diesel power plants is not self starting. &he engine is started from cold condition with the help of anair compressor.

6. Lubriating System:

• &his circuit includes lubricating oil tank, oil pump and oilcooler.

• &he purpose of the lubrication system is to reduce the wearof the engine moving parts. Part of the cylinder such aspiston, shafts, valves must be lubricated.

•ubrication also helps to cool the engine.

• In the lubrication system the oil is pumped from thelubricating oil tank through the oil cooler where the oil iscooled by the cold water entering the engine.

• &he hot oil after cooling the moving parts return to thelubricating oil tank



!. "##ling System

• &he temperature of the burning fuel inside the enginecylinder is in the order of (96@deg "elsius. In order tolower this temperature water is circulated around the

engine.• &he water envelopes*water Aacket+ the engine. &heheat from the cylinder, piston, combustion chamberetc., is carried by the circulating water.

• &he hot water leaving the Aacket is passed through the

heat echanger• &he heat from the heat echanger is carried away bythe raw water circulated through the heat echangerand is cooled in the cooling system.



)peration of a diesel Power Plant

• <hen diesel alternator set is put in parallel HuntingF or PhaseswingingF may be produced due to resonance unless care is takenby manufacturer.

• &his condition occurs due to the resonance between periodicdisturbing forces of the engine and natural freCuency of the

system.• &he engine forces result from uneven turning moment on the

engine crank, which are corrected by ywheel.

• Hunting results from the tendency of each set trying to pull otherinto synchronism.

• &o ensure most economical operation of diesel engines of diBerentsi/es working in parallel and sharing load it is necessary that theyshould carry the same percentage of their full load capacity a allthe times as the fuel consumption would be lowest in thiscondition.



F#r $##% &er'#rmane #' %iesel

p#(er plant• $. Gecessary to maintain the cooling temp withinprescribed limits.

• (. ubricating system should work eBectively andreCuired temp and pressure should be maintained.

• . &he engine should be periodically run even whennot reCuired, should not stand idle for more than 9days.

• 3. %ir #lters, oil #lters and fuel #lters should be

periodically serviced.• 6. Periodic checking of engine compression and

#ring pressure and ehaust temp.



"ombustion Phenomenon in ".I.Engine

• In ".I. engine combustion occurs by the hightemperature produced by the compression ofair, it is an auto ignition. 5inimum compressionratio reCuired is $(.

• &he eDciency of the cycle increases with highervalues of compression ratio but maimumpressure in cylinder also increases.

• Gormal compression ratio lies in range $3 to $9,but may go upto (.

• %ir fuel ratio lie between $; and (6. in "I and $3in !I.



&)ASES *+ ".* E+$*+E ",-/S0*,+:

• *gniti#n %elay peri#%

• &eri#% #' rapi% #r un#ntr#lle%#mbusti#n

• &eri#% #' #ntr#lle% #mbusti#n

• A'ter burning



Ignition elay

• &he ignition delay in a diesel engine isde#ned as the time interval between thestart of inAection and the start of

combustion. &his delay period consists of *a+ physical delay, wherein atomi/ation,vapori/ation and miing of air fuel occur and

*b+ of chemical delay attributed to pre1

combustion reactions.• Physical and chemical delays occur

simultaneously.



• ue to the delay period the pressure reachedduring second stage will depend up on theduration of delay period.

• &he longer delay will cause rough running andmay cause %iesel kn#k .

• elay period should be as sh#rt as possibleboth for the sake of smooth running and in orderto maintain control over the pressure changes.

• >ut , some delay period should be necessaryother wise the droplets would not disappear inthe air for complete combustion.



PE2I) )' 2%PI )2 4G")G&2)E ")5>4!&I)G

• It is the second stage of combustion in ".Iengine.

• &his period is counted from end of the delay

period to the point of maimum pressure onthe indicator diagram.

• &he rise of pressure is rapid because duringthe delay period the droplets of fuel have had

time to spread themselves over a wide areaand they have fresh air all around them.

• %bout $? of heat is evolved during this period



PE2I) )' ")G&2)E ")5>4!&I)G

• %t the end of the second stage ofcombustion , the temperature andpressure are so high that the fuel

droplets inAected in third stage burnalmost as they enter and any furtherpressure rise can be controlled by

inAection rate .• &he heat evolved at the end of the

compression is about 9@ to ;@

percent.



%'&E2 >42GIG7

• &he combustion continues even after thefuel inAection is over , because of poordistribution of particles

• &his burning may be continue in theepansion stroke up to 9@ to ;@*deg+ ofcrank revolution from &".

• &he total heat evolved by the entirecombustion process is =6 to =9 to 6of heat goes as un burnt fuel in ehaust.



elay Period

• It is the time immediately following inAection of the fuelduring which the ignition process is being initiated andpressure does not rise beyond the value it would have due othe compression of the air.

• &he delay period etend for about $deg ", movement ofthe crank.

• elay period depends upon following:

• &emperature and pressure in the cylinder at time ofinAection.

• Gature of the fuel miture strength.• Presence of residual gases.

• 2ate of fuel inAection.

• It should be as short as possible



iesel Jnock

• If the delay period of ".I. engine islong a large amount of fuel will beinAected and accumulated in he

chamber. &he auto ignition of thislarge amount of fuel may cause highrate of pressure rise and high

maimum pressure which may causeknocking in the diesel engine.



"etane Gumber

• "etane rating of a diesel fuel is the measure of its ability to autoignite Cuickly when it is inAected into the compressed and heated airin he engine.

• 2eference miture of cetane*"$8H3+*high ignitability+ and alphamethyl napthalene*"$$H$@+*low ignitability+ are used, The mixture is

made by volume and ignitability of the test fuel is quoted as the percentage of cetane in the reference mixture which has sameignitability.

• 'or higher speed engines: cetane number is 6@

• 'or medium speed engines: cetane number is 3@

• 'or slow speed engines: cetane number is @

• "etane number eBect the following :

• Ehaust emissions: more if ".G is less

• Goise: 5ore if ".G is less

• !tart ability of diesel engine: lessens if ".G. is less



!upercharging

• &he purpose of supercharging is to raise the volumetric eDciencyabove that value which can be obtained by normal aspiration.

• &he engine is an air pump, increasing the air consumptionpermits greater Cuantity of fuel to be added, and results ingreater potential output.

• &he power output is almost directly prop. &o the air consumption.• &hree methods to increase the air consumption are

• $. Increasing the piston displacement: leads to more si/e andweight, cooling problems

• (. 2unning the engine at higher speeds leads to mechanical wear

and tear.• . Increasing the density of the charge, so that greater mass of

charge is introduced in same volume. K<idely 4sedL



• &he apparatus used to increase the air density is calledsuperharger. It is similar to a compressor*centrifugal

type+, which provides greater mass of charge with samepiston displacement.

• &he supercharger produces following eBects:$. Provides better miing of air fuel miture due to

turbulent eBect of supercharger.

(. &he temperature of charge is raised as it is compressed,

resulting in higher temperature within the cylinder, so

better vapori/ation of fuel, but dec in density of charge.. Power reCuired to run the supercharger is obtained from

engine



EBects of !upercharging

• &he Power output is high thannaturally aspirated engine.

• &he mechanical eDciencies arebetter than naturally aspiratedengines.

• It has higher speci#c fuel

consumption that naturally aspiratedengines.



Performance of I.". Engines

$. Power and 5echanical EDciency

(. EBective Pressure and &orCue

. 0olumetric EDciency

3. !peci#c )utput

6. 'uel %ir12atio

8. !peci#c 'uel "onsumption

9. &hermal EDciency and Heat >alance;. Ehaust !moke and Emissions



Power and 5echanical EDciency

i+ Indicted Power: &he total powerdeveloped by the consumption of fuelin the combustion chamber is called

indicated power.



• ii+ >rake Power*>.P.+ &he power developed by engineat the output shaft is called brake power.

• &he diBerence between I.P. and >.P. is called frictionalpower, '.P.

• '.P. M I.P. - >.P.• &he ratio of >.P. to I.P. is called mechanical eDciency.

• N mech .&. *.&.



EBective Pressure and &orCue

• It is de#ned as the average pressure actingover piston throughout a power stroke.

• If mean eBective pressure is based on brakepower*>P+ then it is referred to as brake mean

eBective pressure*>mep+.

• If it is based on indicated power*IP+ it is calledindicated mean eBective pressure*Imep+.

• 'riction mean eBective power is the diBerence of

Imep and >mep.

• 5ean eBective power is the true indication of therelative performance of diBerent engines.



!peci#c output

• It is de#ned as break output per unitof piston displacement.

•p

mb

is mean eBective pressure.Higher the speed higher is thespeci#c output.



0olumetric EDciency

• It is the ratio of the actual volume of the chargedrawn in during the suction stroke to the sweptvolume of the piston.

• &he amount of air taken inside the cylinder is

dependent on the volumetric eDciency of anengine and hence puts a limit on the amount of fuelwhich can be eDciently burned and the poweroutput.

• &he value of volumetric eDciency of a normalengine lies between 9@ to ;@ percent, but forengines with forced induction it may be more than$@@ percent.



%ir 'uel 2atio

• It is the ratio of mass of fuel to mass of airin miture. It eBects the phenomenon ofcombustion and used for determining

ame propagation velocity, the heatreleased in combustion chamber.



!peci#c 'uel "onsumption

• It is de#ned as the amount of fuelconsumed for each unit of brake power perhour it indicates the eDciency with which

the engine develops the power from fuel.it is used to compare performance ofdiBerent engines.



&hermal EDciency and Heat >alance

• It is the ratio of output to that of energy input in the form of fuel.

• )eat alane Sheet: &he performance of an engine is generally given byheat balance sheet.

• Heat !upplied by 'uelM mf "

• mf M mass used per min in kg, "M calori#c value of fuel

• Heat absorbed by I.P. M heat eCivalent of I.P.*per min+ M I.P. 8@ kQ• Heat taken away by cooling waterM mwcpw*t(1t$+, mw M mass of coolng

water per minute, cpwMspeci#c heat of water.

• Heat taken away by ehaust gases M mecpg*te1tr+, meM mass of ehaustgases*kg?min+, cpgMmean speci#c heat at constant pressure



Ehaust !moke and Emissions

• !moke is an indication of incompletecombustion. It limits the output of anengine if the air pollution control is the

consideration.• !peci#c <eight

• It is de#ned as the weight of the engine inkg for each >.H.P. eveloped.

diesel power plant from slide share

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