Chapter 5 Principles of Engine Operation, Two- and Four-Stroke Engines
87
The reason the lid hardly moved is that the
combustion force was not confi ned and directed
toward the lid. Instead, the force was exerted in
all directions, and much of the force was lost. If
the air-fuel mixture is sprayed inside a metal con-
tainer with a lid, the full force of combustion will
be directed against the lid when the mixture is
ignited. This will blow the lid high into the air. See
Figure 5-6.
Even though the burning air-fuel mixture is
confi ned by the container, once the lid starts to lift,
a large amount of the force escapes to the sides.
To eliminate this loss, a long, cylindrical container
may be used with the lid having a close, sliding
fi t. See Figure 5-6. With the fuel mixture slightly
compressed in the bottom of the container by the
weight of the lid, the fuel will burn and direct
most of the pressure against the lid as it travels up
through the container. When the lid reaches the
top, it will be traveling at a high rate of speed. The
expansion of the gas will be nearly complete and
little force will be lost, even after the lid clears the
container.
Goodheart-Willcox Publisher
Figure 5-4.
A—When atomized fuel is exposed to the surrounding
air, a large burning area is available. B—When the
atomized fuel is ignited, it will flash into flame almost
instantly.
Air
Vapor
A
B
Gasoline
Goodheart-Willcox Publisher
Figure 5-5.
A—Atomized fuel is sprayed under a metal lid. B—When the fuel is ignited, the lid moves a short distance.
String
Metal lid
A B
Gas and
air mixture
Goodheart-Willcox Publisher
Figure 5-6.
A—Mixture of fuel and air is sprayed into a container.
B—A lid is placed on top. C—The full force of
combustion is directed toward the base of the lid
when the mixture is ignited, and the lid is driven high
into the air.
A B C
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