Gasoline Purity - OD16200010

Principles of Gasoline And Disesel Fuel Systems
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d. Fuel Distribution. When the fuel is not distributed evenly to all

cylinders, the engine will run unevenly and power output will decrease. To

ensure good distribution, the fuel must be vaporized completely and mixed

with air in the manifold before entering the combustion chamber.

Gasoline Purity

Petroleum contains many impurities that must be removed during the refining

process before gasoline suitable for automotive use is produced. At one

time, considerable corrosion was caused by the sulfur inherent in petroleum

products; however, modern refining processes have reduced it to almost

negligible amounts. Another problem was the tendency for the hydrocarbons

in the gasoline to oxidize into a sticky gum when exposed to air, resulting

in clogged carburetor passages, stuck valves, and other operational

difficulties. Chemicals that control gumming are now added to gasoline.

Dirt, grease, water, and various chemicals also must be removed to make

gasoline an acceptable fuel.

Deicing Agents

Moisture in gasoline tends to freeze in cold weather, causing clogged fuel

lines and carburetor idle ports. Deicing agents are added to gasoline which

mix with the moisture and act as an antifreeze to prevent freezing.

Antiknock Quality

a. Combustion. To understand what is meant by antiknock quality, let

us first review the process of combustion. When any substance burns, it is

actually uniting in rapid chemical reaction with oxygen (one of the

constituents of air). During this process, the molecules of the substance

and oxygen are set into very rapid motion and heat is produced. In the

combustion chamber of an engine cylinder, the gasoline vapor and oxygen in

the air are ignited and burn. They combine, and the molecules begin to move

about very rapidly as the high temperatures of combustion are reached. The

molecules, therefore, bombard the combustion chamber walls and the piston

head with a shower of fast moving molecules. It is actually this

bombardment that exerts the heavy push on the piston and forces it downward