fuels basic

FUELS• PETRO CHEMICALS OR HYDRO CARBONS(HC)• GASOLINE IS A LIQUID OBTAINED FROM CRUDE OIL/MINERAL

OIL/ROCK OIL--ORGANIC COMPOUND • IT IS A DARK BROWN/ BLACK, FOUL SMELLING LIQUID• IT UNDERGOES NO OF REFINING PROCESSES IN THE

REFINERY. USUALLY FRACTIONAL DISTILLATION• HYDROCARBONS WITH MORE CARBON ATOMS HAVE HIGHER

BOILING POINT THAN THE ONE WITH FEWER CARBON ATOMS.

• HC WITH LOW BOILING POINT ARE COLLECTED AT THE TOP OF THE TOWER

FRACTIONAL DISTILLATION

FUELSFRACTIONS BOILING RANGE NO OF CARBON

ATOMSUSES

PETROLEUM GAS BELOW 40 1-4 FUEL COOKING/HEATING

PETROL 40-75 5-10 CARS

NAPTHA 75-150 7-14 PLASTICS, DETERGENT/FEED STOCK

KEROSENE/PARAFIN 160-250 11-16 AIRCRAFTS, COOKING

DIESEL OIL 250-300 16-20 CI ENGINES

LUBRICATING OIL 300-350 20-35 WAXES / POLISH

BITUMEN/ASPHALT ABOVE 350 MORE THAN 70 PAVING ROAD

PROPERTIES OF FUELS

• BOILING & MELTING POINT INCREASES AS MOLECULAR SIZE INCREASES

• DENSITY INCREASES AS MOLECULAR SIZE INCREASES• VISCOSITY INCREASES WITH MOLECULAR SIZE• LESS FLAMMABLE WITH INCREASE IN MOLECULAR

SIZE---SO ?• FUEL WITH LESS CARBON ATOMS IS MORE VOLATILE

& HEATING VALUE INCREASES BY PROPORTION OF HYDROGEN ATOMS .

FUELS• CRACKING IS PROCESS OF

BREAKING LARGE HC BY THERMAL & CATALYSTIC CRAKING

• REFORMATION- WHY? To improve anti knock qualities of fuels

• ISOMERISATION- SAME NO OF MOLECULAR FORMULA BUT DIFFERENT CHEMICAL STRUCTURES

FUELS

FUELS

• N2- 80 % , 02 -20 %• H2 IN HC FORMS H20 &

O2 FORMS CO2• BUT INCOMPLETE

COMBUSTION MAY RESULT IN SOME HC GO OUT TO FORM CO & NOX

• VOLATILITY• RESISTANCE TO SPARK

KNOCK OR DETONATION

• ANTI RUST • ANTI ICERS• DETERGENT-CLEAN

FUEL/CARBURETOR• DYE FOR COLOUR

AIR/FUEL

AIR/ FUEL

FUEL PROPERTIES • VOLATILITY : CRANK CASE

DILUTION, VAPOUR LOCK,STARTING ISSUES

• GUM DEPOSIT:IMPURITIES DUE STORAGE, CLOGS CARBURETOR, CARBON DEPOSITS

• SULPHUR: CORROSION, LOW IGNITION TEMP PROMOTING KNOCKS

• ANTIKNOCK: ABNORMAL COMBUSTION AFTER SPARK AT THE PLUG. HOW?

RESULTING IN HIGH PITCH METALLIC RAPPING NOISE CALLED PINGING.

• PREIGNITION:HOT SPOTS BEFORE SPARK PLUG. HOT EXHAUST VALVE,SPARK PLUG OR CARBON DEPOSITS

RUMBLE TO MILD DETONATION/ DULL THUD

SERVICE ISSUES, WRONG FUELS.DRIVER ISSUE? HOW?

COMBUSTION

COMBUSTION

COMBUSTION

COMBUSTION

COMBUSTION• IF T &P OF AF MIXTURE IS

RAISED HIGH ENOUGH,IT WILL SELF IGNITE WITHOUT A SPARK PLUG.IN SI ENGINES AUTO/PRE IGNITION IS NOT DESIREABLE .SPARK PLUG IGNITES AF MIXTURE AT PROPER TIME IN CYCLE.COMPRESSION RATIO GENERALLY 10:1 TO AVOID PREIGNITION

COMBUSTION• MECHANICAL FACTORS TO

CONTROL COMBUSTION• QUENCH AREA PREVENTS

LAST PART OF AF MIXTURE TO DETONATE.IT OCCURS AT END OF COMPRESSION STROKE.MIXTURE SQUEEZED TO PROMOTE TURBULENCE.

• HEMISPHERE SHAPE HAS A CENTRAL PLUG.FLAME TRAVELS A SHORT DISTANCE. NO END POCKETS

OCTANE NO• ENGINE DESIGN & COMPRESSION RATIO

DETERMINES THE OCTANE REQUIREMENT.• OCTANE MEASURES THE ANTIKNOCK

QUALITY OF FUEL• HIGHER OCTANE NO,THE MORE

RESISTANT THE GASOLINE IS TO KNOCK• 93 IS MORE RESISTANT THAN 89• GASOLINE THAT DETONATE IS LOW

OCTANE, & THAT RESISTS DETONATION IS HIGH OCTANE.

• HIGH COMPRESSION RATIO REQUIRES HIGH OCTANE NO.HIGH COMPRESSION IS DESIREABLE TO PRODUCE MORE POWER.BUT?

• VERY HIGH RATIOS MAY DETONATE .TEL IS NOW OBSOLETE

OCTANE NO• ORGANOMANGANESE &

ALCOHOLS SUBSTITUTES OF TEL.

• KNOCK OCCURS AT WOT WHEN ENGINE IS LOADED/GOING UPHILL

• SOLUTION- HIGH OCTANE(SLOW BURN) ,IGNITION TIMING ADVANCE----MEDIUM OCTANE RETARD IGNITION OR STARTING COMBUSTION LATER IN COMPRESSION STROKE.

OCTANE NO

DIESEL FUEL

• COMPRESS ONLY AIR ON THE COMPRESSION STROKE

• HEAT OF COMPRESSION IGNITES FUEL AS IT SPRAYS INTO THE ENGINE CYCLINDER

• HAS A HIGH COMPRESSION RATIO OF 16:1 TO 22:1

• CONTROLS ENGINE POWER AND SPEED ONLY BY THE AMOUNT OF FUEL SPRAYED INTO THE CYCLINDER.MORE FUEL EQUALS MORE POWER

DIESEL FUEL

FLASH POINT• OF A VOLITILE MATERIAL LOWEST

TEMP AT WHICH IT CAN VAPORIZE TO FORM AN IGNITABLE MIXTURE IN AIR.

• IT REQUIRES AN IGNITION SOURCE• AT FLASH POINT , THE VAPOURS

CEASE TO BURN WHEN SOURCE OF IGNITION IS REMOVED

• SI ENG, AF MIX IS HEATED ABOVE ITS FLASH POINT, THEN IGNITED BY SPARK PLUG.TO AVOID PREIGNITION, LOW FLASH & HIGHER AUTO IGNITION.

.IT DOES NOT REQUIRE AN IGNITION SOURCE

• TEMP AT WHICH VAPOURS CONTINUE TO BURN AFTER BEING IGNITED.( SEE NEXT SLIDES PLEASE)

SELF IGNITION

DIESEL FUEL• VOLATILITY: LESS THAN

PETROL BUT IT ALSO EMPHASIZES THAT IT HAS HIGHER HEATING VALUE.(LONG CHAIN)

• VISCOSITY:LESS OTHERWISE IT WOULD NOT BREAK INTO PARTICLES.SMALL PARTICLES BURN FAST.

• SULPHUR:EXCESSIVE CYLINDER WEAR/LUBRICATING OIL

• KNOCK: TIME OF INJECTION AND ACTUAL BURNING.IF LAG INCREASES , AMOUNT OF FUEL ACCUMULATED IS MORE,ABNORMAL AMOUNT OF ENERGY IS RELEASED, EXCESSIVE PRESSURE RISE AND AUDIBLE KNOCK.

• A GOOD CI ENGINE HAS SHORT IGN LAG.

• IGN LAG AFFECT STARTING,WARM UP, AND PRODUCES SMOKE

DIESEL FUEL• IMMEDIATELY AFTER INJECTION, THE

FUEL PARTIALLY EVAPORATES WITH A RESULTING CHILLING OF THE AIR IN THE IMMEDIATE VACINITY OF EACH FUEL PARTICLE.HOWEVER, THE EXTREME HEAT OF COMPRESSION RAPIDLY HEATS THE FUEL PARTICLES TO SELF IGNITION POINT AND COMBUSTION BEGINS.THE FUEL BURN AS THEY MIX IN THE AIR.THE SMALLEST PARTICLES BURN RAPIDLY BUT LARGER TAKES MORE TIME TO IGNITE BECAUSE HEAT MAY BE TRANSPORTED INTO THEM TO BRING THEM TO SELF IGNITION.COMBUSTION IS SLOWER AND PRESSURE RISE IS SMALL(CONSTANT)

CETANE NO• CETANE NO REF TO EASE

WITH WHICH FUEL IGNITES.• A HIGH CETANE NO IS FAST

BURNING AND IGNITES AT RELATIVELY LOW TEMP . & VICE VERSA

• PROCEDURE TO FIND CETANE IS SIMILAR TO OCTANE EXCEPT CETANE 100 & ALPHA METHYL NAPHTHALINE 15 ARE USED.

• GREATER THE REFINING DONE ON FUEL, THE LOWER IS ITS MOLECULAR WEIGHT ,LOWER IS ITS VISCOSITY ,AND GREATER IS ITS COST. SO CARS USES LIGHT OR SOME TIMES CALLED NO 2 DIESEL.OTHER TYPE IS USED IN MASSIVE HEATING UNITS.

• INVERSE RELATIONSHIP OF PETROL TO DIESEL

NUMERICAL

FUEL PROERTIES -TABLE