Operating Cycles

The sequences of operation of a Packard diesel engine compared with those of a 4-stroke cycle gasoline engine are illustrated in figure 21.

Brief Analysis of Action in a Four-Cycle Gasoline Engine

Mixture of air and
gasoline enters
cylinder from
carburetor.		Mixture is compressed
into smaller volume
by piston moving
upward.		An electric spark
ignites the compressed
mixture causing it
to explode.		Combustion heat
increases the cylinder
pressure forcing
piston downward.		Momentum carries
piston upward
which pushes burnt
gases out through
the exhaust valve.

Similar Action in the Packard-Diesel Aircraft Engine

Atmospheric air only,
enters cylinder
through single valve.		Air is so greatly
compressed by upward
moving piston that
it reaches
temperature of
1000° F.		Just before piston
is at dead center
fuel oil is sprayed
into cylinder and
spontaneously ignited.		Power of this
explosion is passed
to crankshaft
in conventional manner.		Piston forces out
burnt gases through
same single valve
which is cooled
by inrush of new
air as cycle repeats.