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SHEIKH SHAHIR MUHAMMAD AFIFUL ISLAM   TITLE:

KEM120702 Requirement of Fuels Quality for CI(diesel) Engine

INTRODUCTION

 A compression-ignition engine or commonly known as a diesel engine is an internal

combustion engine in which used a higher compression of the fuel to ignite the fuel

rather than using spark plug (spark ignition). Air is compressed adiabatically with a

compression ratio typically between 15 and 20. his compression raises the

temperature to the ignition temperature of the fuel mi!ture which is formed by in"ecting

fuel once the air is compressed.

FUEL CHARACTERIZATION

he fuel used in a compression ignition (#$) engine is diesel% which is a type of 

hydrocarbon. &or hydrocarbons to 'ualify as a fuel for the engine% they should possess

certain 'ualities to be the ideal fuel for these engines.

i. nocking characteristics heoretically as soon as diesel fuel is in"ected into the

cylinder% it starts burning. *ut in practical situations this ne+er happens as there is

always a time lag between the in"ection of the fuel and burning of the fuel. As the

duration of ignition lag increases% the amounts of fuel get accumulated in the cylinder 

head will also increased. ,hen the fuel is finally burnt% e!cessi+ely large amounts of 

energy is released% which produces e!tremely high pressure inside the engine. his

causes the knocking sound inside the engine. hus the engines should ha+e a short

ignition lag so that the energy is produced uniformly inside the engine and there is

no abnormal sound. he knocking capacity of the fuel is measured in terms of 

cetane rating of the fuel. $t should ha+e a cetane number high enough to a+oidknocking of engine.

ii. A$ gra+ity enerally% there is a /-5 decrease in the thermal energy content of 

fuel for e+ery 10 degree increase in A$ gra+ity. his decrease in energy content will

result in roughly the same percentage decrease in engine power. se of fuels with

higher A$ gra+ity will also result in higher fuel consumption. $t is recommendation to

include a ma!imum A$ gra+ity is based on our understanding of customer needs to

maintain engine power% while minimiing fuel consumption.

iii. 3olatility of the fuel horough mi!ing of the fuel and air when fuel is in"ected in the

cylinder head ensures uniform burning of the fuel. he fuel should be +olatile in

nature within the operating temperature range of the cylinder head so that it gets

con+erted into a gaseous state and mi!es thoroughly with compressed air.

i+. 4tarting characteristics of the fuel he smooth starting of the +ehicle depends

greatly on the fuel used for the +ehicle. &or easy starting of the +ehicle it is important

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that the fuel has good +olatility so that it mi!es with the air uniformly and it readily

forms intothe combustible mi!ture. $n a particular diesel engine% higher cetane fuels will ha+e

shorter ignition delay periods than lower cetane fuels which in turn will lead to faster 

starting of the +ehicle.

+. 4moke produced by the fuel and its odor iesel e!haust is a comple! mi!ture of 

thousands of gases and soot that contains more than 60 to!ic air contaminants.

hese include suspected cancer-causing substances% such as benene% arsenic and

formaldehyde. $t also contains other harmful pollutants% including nitrogen o!ides. As

we breathe% the to!ic gases and small particles of diesel e!haust are drawn into the

lungs and are small enough to penetrate deep into the lungs% where they contribute

to a range of health problems. 4o the e!haust gases produced from the fuel should

not ha+e too much smoke and odor.

+i. 3iscosity of the fuel 3iscosity affects in"ector lubrication and fuel atomiation. &uels

with low +iscosity may not pro+ide sufficient lubrication for the precision fit of fuel

in"ection pumps or in"ector plungers resulting in leakage or increased wear. &uels

which do not meet +iscosity re'uirements can lead to performance complaints. &uel

atomiation is also affected by fuel +iscosity. iesel fuels with high +iscosity tend to

form larger droplets on in"ection which can cause poor combustion and increased

e!haust smoke and emissions. 4o the fuel should ha+e enough +iscosity so that it

can easily flow through the fuel system and the strainer at the lowest working

temperatures.

+ii. etergency All diesel fuels which do not contain detergents ha+e a tendency to form

carbon deposits on fuel in"ectors. $t has generally been found that low sulfur fuelsand thermally unstable fuels ha+e a greater tendency to form these deposits.

etergent additi+es will pre+ent carbon deposits% which interfere with fueling and fuel

spray patterns% from forming. irty in"ectors will in+ariability gi+e rise to higher smoke

le+els in all e'uipment and in some e'uipment can limit power by restricting fuel

flow.

+iii. 7ubricity 7ubricity describes the ability of a fluid to minimie friction and damage

between surfaces in relati+e motion under loaded conditions. iesel fuel in"ection

e'uipment relies on the lubricating properties of the fuel. 7ack of fuel lubricity can

shortened the life of engine components such as fuel in"ection pumps and unitin"ectors.

CONCLUSION

*ecause of the uni'ue combination of power% performance% energy efficiency% reliability

and low-emissions% diesel engines are the undisputed workhorse of the global economy%

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SHEIKH SHAHIR MUHAMMAD AFIFUL ISLAM   TITLE:

KEM120702 Requirement of Fuels Quality for CI(diesel) Engine

powering almost all super-sectors including agriculture% construction% transportation%

mining and many more.