PRIME MOVERS AND POWER PLANT MACHINERY.
THREE GENERAL TYPES OF LIQUID-FUEL ENGINES.
According to the means used for atomizing the liquid fuels and igniting
them, there are two mechanically and thermodynamically distinct types of
engines. In one type the entire fuel charge is sprayed against a highly heated
surface in a chamber connected with the working cylinder. Contact with this
highly heated surface gasifies the fuel, which is ignited and burns with ex-
plosion-like rapidity. Engines of this type are properly termed "explosion oil
engines," or engines in which the fuel is burned at constant volume.
In engines of the other type the fuel to be converted is finely subdivided by
air, and in this act of atomization is injected directly into the engine cylinder,
where it is ignited automatically by the highly
heated air in the cylinder. The combustion is not
explosion like, but is prolonged as constant pres-
sure for the entire period during which the fuel
is injected into the cylinder. This type of engine
is universally known as the Diesel engine, being
named after the late Rudolph Diesel, of Munich,
Germany, its inventor. It is also termed a
"constant-pressure oil engine."
There is a third general type of engine, com-
bining features of the two types mentioned, in
which the fuel is burned at both constant volume
and constant pressure. Engines of this type are
known as Sabath4 engines.
According to whether an engine receives a
working impulse every other revolution of each
revolution, it is said to have a four-stroke cycle
or a two-stroke cycle. Either type of engine may
be a single acting or double acting, such con- FuUn 6.-Explosion oil en-
structions being wholly mechanical and influ- gine, four-stroke cycle.
encing in no manner the thermodynamic cycle of
an engine. All the three. general types of oil engines enumerated may be built
to work either on the four-stroke cycle or the two-stroke cycle and may be
either single or double acting.
EXPLOSION OIL ENGINES.
ENGINES WITH FOUR-STROKE CYCLE.
Figure 6 shows the elements of an explosion oil engine having a four-stroke
cycle. During the first stroke of the piston downward, which creates a partial
vacuum in the cylinder, atmospheric air is admitted through the air-admission
valve a into t1he cylinder. On the return stroke of the piston, valve a is closed,
and the air in the cylinder is compressed. Before the piston is at the inner
(upper) dead center, the fuel charge is sprayed by the fuel pump b into the
chamber c, known as a hot bulb or hot ball, which is kept at a dull, cherry-red
heat. As the piston reaches its inner (upper) center, the fuel is burned with
explosion-like rapidity, the temperature and pressure in the cylinder increase,
and the piston receives a power impulse, the gaseous mixture expanding during
the second downward stroke of the piston. On its return stroke the exhaust
valve d is opened and the piston sweeps the gaseous products before it and
through the valve d. The working cycle of four strokes is then repeated.
George, H. C. Surface Machinery and Methods for Oil-Well Pumping. Washington D.C.. UNT Digital Library. http://digital.library.unt.edu/ark:/67531/metadc12407/. Accessed September 16, 2014.