is a substance which participates easily with oxygen in a self-sustaning exothermic reaction and much has been studied ever since the engines have been in existance.

prinicipal constituents of fuel

Petroleum comes from two Greek words

is a mixture of many different hydrocarbons, with some sulphur and some impurities.

are stable, saturated compounds having the general chemical formula CnH2n+2.

The hydrocarbons which have the same chemical formula but different structural formula are known as

is a very smooth burning fuel in a SI engine and has been chosen as the standard for 100 octane gasoline

is a rather poor engine fuel and has a low octane rating.

are also straight chain compounds similar to paraffins but they are unsaturated as they contain one or more double bonds between the carbon atoms.Their general chemical formula is CnH2n

have a structure similar to that of the oelfins, but have two double bonds in the open-chainn sturcture,(CnH2n-2)

are saturated, stable compounds with a ring structure. general chemical formula is CnH2n

are unsaturated but stable ring compounds. The general chemical formula for this group is CnH2n-6.

is carried out in a tubular furnace with a tall steel fractionating column. The crude oil is pumped continuously through a heated pipe and flashed into the fractionating column.

is the process of breaking down the large and complex molecules into lighter and simpler compounds.

heavy carbons are subjected to high temperature and pressure. At high temperature, the kinetic energy of the molecules increases and as a result they move faster and strike harder. Thus, some of the chemical bonds holding the carbon atoms together break away the molecules split into lighter and smaller compounds.

lower pressure and temperature are required and the smaller molecules are found to be isomeric rather than normal hydrocarbons. This is desirable because the isomeric compounds have better anti-knock characteristics.

a cracking process with occurs in an atmoshpere of hydrogen. Certain unsaturated compunds pick up more hydrogen to become saturated, and the yield and quality of gasoline are increased.

the gases leaving the refinery processes may contain some heavier hydrocarbons in the vapour state, which may fall into the gasoline range. This process is used to recover these vapours. In this process the gases come into contact with a kerosene or light oil which absorbs the heavy hydrocarbon vapours. The vapours are then driven out from the oil by the heating. Finally, the vapours are cooled to obtain gasoline

is the process of combining the unsaturated products of one family (two or more olefinic molecules) to form heavier and stable compounds that have that have a high anti-knock rating.

is the process of combining light undesirable hydrocarbons of one chemical family with another family to form a larger molecule. An isoparaffin (usually isobutane) combines with an olefin (usually butene or propene) to form a larger isoparaffin (usually isooctane or isoheptane) that has a very high octane number.

is the process of changing the relative position of atoms within the molecule of a hydrocarbon without changing its molecular formula. It produces isomers of the original hydrocarbons.

is a process of joining together the ends of a straight chain molecule to form a ring compound of the napthene family.

is a process of joining together the ends of a straight chain molecule to foam an aromatic compound.

is used to convert low antiknock quality gasoline into high antiknock quality. It does not increase the total gasoline volume as in polymerization and alkylation.

is a process of mixing certain products to obtain a commercial product of desired quality. The products from various refinery processes are blended together to form liquid fuels with the proper physical characteristics to give high quality gasoline, fuel oil, kerosene, diesel fuel, etc. These liquid products are then put through the various finishing processes to reduce the sulphur and wax contents.

consists of a mixture of liquid hydrocarbons having four to ten carbon atoms, small amounts of lighter and heavier hydrocarbons, minute quantities of crude petroleum impurities such as sulphur and nitrogen.

is the next fraction heavier than gasoline. It is widely used in lamps, heaters, stoves and similar appliances. It may also be used in compression-ignition (CI) engines and gas turbines. Its specific gravity is between 0.78 to 0.85.

are petroleum fractions heavier than kerosence. These oils cover a wide range of specific gravity and a very wide distillation range. Their composition is controlled to make them suitable for use in various types of CI engines. The heating value of a typical diesel oil is 42,000 KJ/kg.

the range of specific gravity and the distillation range are similar to those of diesel oils. Their composition does not require accurate control as is required in the case of diesel oils. These fuels are used in continuous burners

these are made up in part from heavy distillation of petroleum and in part from residual oils that remain after distillation. These are used for lubricating purposes.

is a distillate of coal tar. It contains about 70% benzene (C6H6), 20% tolune (C7H8), 10% xylene (C8H10) and traces of sulphur compounds. It has a high antiknock characterisitc and can be blended with gasoline to be used as fuel in SI engines

is of organic origin and can be produced from a wide range of abundantly available raw materials. Ethanol (C2H5OH) can be produced by fermentation of carbohydrates which occur naturally and abundantly in some plants like sugarcane or from starchy materials like corn, potatoes, maize and barley. The starchy material is first converted into sugar which is then fermented by yeast.

is a very volatile fuel. It is used with other fuels to increase the volatility of the blend.

is the tendency of a liquid to evaporate at given conditions.

In the winter and cold climate, an air-vapor mixture of 13:1 is required for easy starting (in less than 10 revolutions). This ratio can be obtained in the engine by choking the carburettor and so restricting the inlet flow of air.

If the engine is started immediately after a hot shutdown, the amount of fuel vapours entering the intake manifold will be high, and the mixture formed in the combustion chamber will be too rich to ignite, it creates the problem of hot starting

is the restriction of the fuel supply to the engine caused by the excessively rapid formation of vapour in the fuel system of carburettor. The vapour will occupy a greater volume than the liquid and therefore the amount of fuel flow to the engine will be reduced causing low power to stoppage of the engine.

depends on the vapor pressure of the fuel at the storage temperature. It decreases the fuel economy and and the anti-knock quality of the fuel, since the lighter fractions have higher anti-knock properties.

is formed due to the vaporization of gasoline into the air containing water vapour.

Liquid gasoline that enters the cylinder has the tendency to reduce lubircation in the cylinder walls thus increasing friction between piston and culinder that could damage the engine. Engines using heavy fuels such as kerosene which is less volatile, may suffer from poor lubrication because of excessive dilution.

Certain typers of hydrocarbons present in gasoline may not evaporate.

High sulphur content in gasoline in the form of free sulphur, hydrogen sulfide and other sulphur compounds is undesirable because of the formation of SO3 whose combination with water vapour forms Sulfuric acid (H2SO4) , which is a very corrosive substance that may attack various parts of the engine, thus affecting engine performance and life.

Reactive hydrocarbons and impurities in the fuel have a tendency to oxidize and form viscour liquids and solids called gum.

are used to prevent the formation of gum deposits and to remove the exisitng deposits.

Detonation in SI engines causes a very rapid and uncontrolled burning of the fuel and air mixture in a cylinder, and this results in an abnormally rapid pressure rise.

ability of the fuel to ignite promptly after injection.

high volatility fuels are generally not used in CI engines but are common in SI engines.

this property of oil increases with the increase in the number of carbon atoms in it, while it decreases rapidly with the increase in temperature.

mass of a unit volume of a fluid to the mass volume of water at the same temperature (usually at 15.6 oC).

the fuel should not contain much sulphur, carbon residue and ash.

Sulphur trioxide (SO3) can be formed during the combustion process which attacks the lubricating oil on the cylinder walls to form resinous materials which harden to form varnish and carbon

when fuel is burned with limited oxygen, this is usually left. these increase the deposits in the combustion chamber and around the nozzle tips, thsu adversely affecting spray characteristics.

this content of a fuel is the solid material which remains after a complete combustion of the fuel. It is a measure of abrasviness of the products of combustion that could cause wear in the engine.

is measured by the cloud point and the pour point of the fuel. Cloud point refers to the temperature at which there is a presence of a wax cloud in the fuel, pour point is the lowest temperature at which the fuel tends to freeze or ceases to flow.

of the diesel fuel is measured by its flash point and fire point.

is the lowest temperature at which fuel will vaporize sufficiently to form a considerable mixture of fuel vapour and air above the fuel.

is the temperature at which enough vapours will rise to produce a continuous flame above the liquid fuel. The flame must sustain at least for five seconds.

is important because of the precisely fitted parts in the fuel pump and nozzle.

The practical measure of a fuel’s resistance to knock in SI engines

The higher the octane number (ON)

is a measure of the extent to which a gasoline is downgraded under severe conditions. The higher sensitivity indicates poor performance under severe conditions.

This differs from RON and MON. It can lie between the RON and MON

is a measure of the antiknock effectiveness.

is the most used methods for diesel fuels.

defined as the minimum temperature at which equal volumes of aniline (C6H5NH2) and lubricant oil are miscible, i.e. form a single phase upon mixing.

is a distillate fuel that is used commonly for burning in furnaces, boilers, stoves and lanterns to generate heat. It is a fraction obtained from petroleum distillation, either as a distillate or a residue at the oil refinery.

This is referred to as coal oil, stove oil and range oil. It’s a volatile distillate oil.

This is referred to as heating oil or bunker A.

This fuel is for low-viscosity burning, but it is less frequently used since the mid-20th century.

This is a commercial heating oil used for boilers/burners where pre-heaters and not installed.

This is an industrial heating oil which needs preheating to 77-104°C. This fuel is referred to as bunker B.

This is a residual oil which also needs preheating, however to 104-127 °C. This fuel is known as bunker C.

Fuels A, B, and C are respectively downgrading quality-classifications of fuel oil, characterized by their boiling points, carbon-chain lengths, and viscosities, all of which contribute to their value

MGO

MDO

IFO

MFO

a by-product of gas production from bituminous coal and also from coke-oven operations, is used as fuel for some diesel engines.

first developed by Rudolf Diesel during the infancy of the famous diesel engine. It requires a compression ratio of about 500 to 525 psi and the air injection pressure of about 1,000 psi.

slowly and utlimately replaced the air injection system. This is also known as mechanical, soild or hydraulic injection; is the widely used system for current engines.

developed by Vickers company in England, was the first satisfactory mechanical-injection system. It consists of a system of pipes which connect the high-pressure oil pump or pumps with the fuel or spray nozzle in each cylinder.

differs from the constant-pressure injection in both design and operation of the pumps and fuel injectors.

in this system the fuel oil is supplied through rotating distribution, to individual metering pumps and from there to the cylinders.

in this system, a Unit injector (UI) is used which is a high pressure integrated direct fuel injection system for diesel engines, combining the injector nozzle and the injection pump in a single component.