Page 206 - 05. Subyek Teknik Mesin - Automobile Mechanical and Electrical Systems Automotive Technology Vehicle Maintenance and Repair (Vehicle Maintenance Repr Nv2) by Tom Denton

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190 Automobile mechanical and electrical systems

Figure 2.222 New diesel injection system

Carbon
dioxide

Fuel
Engine Water
Air

Nitrogen

Carbon
dioxide

Water
Fuel Nitrogen

Carbon
Engine
monoxide
Air Hydro-
carbons
Nitrogen
oxides
Particulate

Figure 2.223 Ideal (upper) and incomplete (lower) combustion

vehicles, the quantities of hydrogen and carbon in the fuel and the oxygen
content of the air should be chemically correct to allow a complete chemical
Key fact change during combustion. The chemical formula for clean combustion is
All fuel delivery systems have CH 2O 2 CO 2 2H 2 O, or hydrocarbon plus oxygen results in carbon dioxide
4
to supply a quantity of fuel that and water.
matches the amount of oxygen that For complete and clean combustion ( Fig. 2.223 ), the ratio of air to fuel should be
is in the air entering the engine.
as close as possible to the stoichiometric value. This is where λ (lambda) equals
one. This is a ratio of 14.7:1 by mass of air to fuel. In petrol engines, the optimum
for clean combustion is for these quantities to be delivered accurately to each
cylinder in the engine.