The main fuel for SI engines is gasoline, which can be a combination of the numerous hydrocarbon components and is manufactured from crude petroleum.

Crude oil was first discovered in Pennsylvania in 1859, and so the gas line of merchandise generated from it developed along with the event of the IC engine.

It varies from 83% to 87% carbon and 11% to 14% hydrogen by weight.

One test of a fuel sample identified over 25,000 different hydrocarbon components.

The crude mixture which is taken from the underside is separated into component products by cracking and/or distillation using thermal or catalytic methods at a refinery.

Cracking is that the method of breaking large molecular components into more useful components of smaller relative molecular mass.

Preferential distillation is utilized to separate the mixtures into single components or smaller ranges of components.

Generally, the larger the mass of a component, the upper is it boiling temperature.

The component mixture of the refining process is utilized for several products, including: automobile gasoline fuel aircraft gasoline jet fuel home heating fuel industrial heating fuel lubrication oil asphalt alcohol rubber paint plastics explosives.

The availability and value of gasoline fuel, then, can be a result of a market competition with many other products.

This becomes more critical with the depletion of the earth’s crude reserves, which looms on the horizon.

In the us, two general classifications are identified: Pennsylvania crude and western crude.

Pennsylvania crude incorporates a high concentration of paraffins with little or no asphalt, while western crude has an asphalt base with little paraffin.

The petroleum from some petroleum fields within the Mideast is made of component mixtures that may be used immediately for IC engine fuel with little or no refining.

The various components of varied molecular weights will vaporize at different temperatures, small molecular weights boiling at coldness and greater molecular weights at higher temperature.

This makes a very desirable fuel.

A small percentage of components that vaporize (boil) at cold is required to assure the starting of a cold engine; fuel must vaporize before it can burn.

However, an excessive amount of of this front-end volatility can cause problems when the fuel vaporizes too quickly. Volumetric efficiency of the engine is reduced if fuel vapor replaces air too early within the intake system.

Another significant issue this can cause is stoppage, which occurs when fuel vaporizes within the fuel supply lines or within the carburetor within the new engine compartment.

When this happens, the availability of fuel is stop and so the engine stops.

A large percent of fuel should be vaporized at the standard intake system temperature during the short time of the intake process.

To maximize volumetric efficiency, variety of the fuel mustn’t vaporize until late into the compression stroke and even into the start of combustion.

If an excessive amount of this high-end volatility is included within the gasoline, however, variety of the fuel never gets vaporized and winds up as exhaust pollution or condenses on the cylinder walls and dilutes the grease.

One way that’s sometimes want to explain a gasoline is to use three temperatures: the temperature at which 10% is vaporized, at which 50% is vaporized, and at which 90% is vaporized.

The gasoline could therefore be classified as 57-81-103°C.

If different commercial brands of gasoline are compared, there’s found to be little difference within the volatility curves for a given season and site within the country.

There is usually a pair of 5°C shift down in temperature on the vaporization curve for winter gasoline compared with summer.

If gasoline is approximated as a single-component hydrocarbon fuel, it would have a molecular structure of about CSH15 and a corresponding mass of 111.

These are the values which will be utilized during this textbook.


A saturated hydrocarbon molecule will don’t have any double or triple carbon-to carbon bonds and might have a maximum number of hydrogen atoms.

An unsaturated molecule will have double or triple carbon-to-carbon bonds.

A number of varied families of hydrocarbon molecules are identified; a number of the more common ones are described.

Paraffins The paraffin family (sometimes called alkanes) are chain molecules with a carbon-hydrogen combination of CnH2n+ 2, n being any number.

The simplest member of this family, and thus the best of all stable hydrocarbon molecules, is methane (CH4).

Isobutane can also be called methylpropane-propane because it’s three carbon atoms within the most chain and one alkyl group, CH3, replacing one in every of the hydrogen atoms.

Molecules with no branches in their chain are sometimes called normal; thus, butane is usually called normal butane or n-butane.

Even though isobutane and n-butane have the identical statement, C4HlO, and almost identical molecular weights, they have different thermal and physical properties. this is often often true for any two chemical species that have different molecular structures, whether or not they have the identical formula.