PRINCIPLES GASOLINE/DIESEL FUEL SYSTEMS - OD1620 - LESSON 1/TASK 1
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.
3.
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.
4.
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.
5.
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
on the power stroke.
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