Aniinternalicombustionienginei(ICE) is a heat engine where the
combustion of a fuel occurs with an oxidizer (usually air) in a
combustion chamber that is an integral part of the working fluid flow
circuit. In an internal combustion engine the expansion of the
high-temperature and high-pressureigases producediby combustion apply
direct force to some component of the engine. The force is applied
typicallyito pistons, turbine blades, rotor or a nozzle. This force
moves the component over a distance, transforming chemical energy
into useful mechanical energy.
The
first commercially successful internal combustion engine was created
by Étienne Lenoir around 1859 and the first modern internal
combustion engine was created in 1876 by Nikolaus Otto.
The
term internal combustioniengine usually refers to an engine in which
combustion is intermittent, such as the more familiar four-stroke and
two-stroke piston engines, along with variants, such as the
six-stroke pistoniengine and the Wankel rotary engine. A second class
of internal combustion engines use continuous combustion: gas
turbines, jet engines and most rocket engines, each of which are
internal combustion engines on the same principle as previously
described.Firearms are also a form of internal combustion engine.
Internal
combustion engines are quite different from external combustion
engines, such as steam or Stirling engines, in which the energy is
delivered to a working fluid not consisting of, mixed with, or
contaminated by combustion products. Working fluids can be air, hot
water, pressurized water or even liquid sodium, heated in a boiler.
ICEs are usually powered by energy-dense fuels such as gasoline or
diesel, liquids derived from fossil fuels. While there are many
stationary applications, most ICEs are used in mobile applications
and are the dominant power supply for vehicles such as cars,
aircraft, and boats.
Typically
an ICE is fed with fossil fuels like natural gas or petroleum
products such as gasoline, diesel fuel or fuel oil. There's a growing
usage of renewable fuels like biodiesel for compression ignition
engines and bioethanol or methanol for spark ignition engines.
Hydrogen is sometimes used, and can be made from either fossil fuels
or renewable energy.
Reciprocating
piston engines are by far the most common power source for land and
water vehicles, including automobiles, motorcycles, ships and to a
lesser extent, locomotives (some are electrical but most use Diesel
engines). Rotary engines of the Wankel design are used in some
automobiles, aircraft and motorcycles.
ICEs
drive some of the large electric generators that power electrical
grids. They are found in the form of combustion turbines in combined
cycle power plants with a typical electrical output in the range of
100 MW to 1 GW. The high temperature exhaust is used to boil and
superheat water to run a steam turbine. Thus, the efficiency is
higher because more energy is extracted from the fuel than what could
be extracted by the combustion turbine alone. In combined cycle power
plants efficiencies in the range of 50% to 60% are typical. In a
smaller scale Diesel generators are used for backup power and for
providing electrical power to areas not connected to an electric
grid.
Small
engines (usually 2‐stroke gasoline engines) are a common power
source for lawnmowers, string trimmers, chain saws, leafblowers,
pressure washers, snowmobiles, jet skis, outboard motors, mopeds, and
motorcycles
Where
very high power-to-weight ratios are required, internal combustion
engines appear in the form of combustion turbines or Wankel engines.
Powered aircraft typically uses an ICE which may be a reciprocating
engine. Airplanes can instead use jet engines and helicopters can
instead employ turboshafts; both of which are types of turbines. In
addition to providing propulsion, airliners may employ a separate ICE
as an auxiliary power unit. Wankel engines are fitted to many
unmanned aerial vehicles.
The
Abbé Hautefeuille described in 1678, an engine for raising water, in
which the motive power was obtained by burning gunpowder in a
cylinder and cooling the remaining gases with water. The idea was
similar to that expressed in the early forms of the steam engine, but
Hautefeuille does not appear to have preformed any actual
experiments. The same idea was suggested by Huygens in 1680, but
experiments made by him and later by Denis Papinwere not attended by
success and were abandoned, though they are interesting as
representing the first actual attempts at the building of
internal-combustion engines.
A
long period of inaction followed. The discovery of the distillation
of gas from coal and the demonstration, by Murdock in 1792, of the
application of coal gas for lighting purposes roused new interest in
the subject. The introduction of the steam engine for commercial
purposes about this time was also a powerful incentive, though for
many decades the steam engine was too firmly intrenched and fitted
the existing conditions too well to afford much opportunity for
competition. About 1791 John Barber explained in a patent how a wheel
with vanes could be driven by the released pressure of an orifice
close to the vanes. In the century and a quarter that have elapsed
since that day, no economical gas turbine has been constructed.
The
first internal-combustion engine, according to our modern ideas, was
that of Robert Street, patented in England in 1794. In this the
bottom of a cylinder was heated by fire and a small quantity of tar
or turpentine was projected into the hot part of the cylinder,
forming a vapor. The rising of the piston sucked in a quantity of air
to form the explosion mixture and also flame for ignition. The cycle
was that which was used later by Lenoir in the first commercially
successful engine. About 1800 Phillippe Lebon patented in France an
engine using compressed air, compressed gas and electricity for
ignition. Some authorities believe that his early death retarded the
development of the internal-combustion engine half a century, as all
of the features mentioned are necessary to the highly efficient
engines of today, though they did not come into use for
three-quarters of a century after his death.
The
next engine to attain any considerable prominence was that of Samuel
Brown, who secured several patents in England about 1825. His engine
did not represent an advance, since the old ideas of Huygens were
employed instead of the advanced ideas of Street. The success of the
atmospheric steam engines was probably responsible for this. Brown's
engine consisted of a number of large chambers, in which the hot
gases produced by flame were cooled by the injection of water, thus
forming a partial vacuum. The working pistons, in cylinders adjacent
to the large chambers, were operated by atmospheric pressure, all
pistons being connected to the same crankshaft, as shown in Fig. 1.
Since the burning did not occur in the working cylinder, the engine
can scarcely be called an internal-combustion engine in the accepted
sense of the term. The inventor appears to have been a man of
considerable force, and a number of his engines were built for
pumping and for driving carriages and boats. In 1833, W. L. Wright
patented in England, the engine illustrated in Fig. 2. The gas and
air were supplied by separate pumps to a working cylinder. The charge
was contained in the spherical bulbs near the ends of the cylinder,
ignition occurring while the piston was at the end of the stroke. The
engine was double acting, water jacketed, with poppet exhaust valves
and a fly-ball governor. It represented a great advance in design and
was probably built, though no records of its performance are known to
exist.
In
1838 William Barnett patented in England an engine which was an
advance upon preceding types in that country. It compressed the gas
and air separately, igniting the mixture when the piston was at the
end of its stroke. The third engine described by this inventor is
shown in Fig. 3, and is interesting because it embodies several
features of the modern two-cycle engine. In the figure the piston is
supposed to be moving upward, compressing a mixture of gas and air.
Ignition occurs when the piston has reached its highest position, and
the piston driven down, expansion occurring until the piston passes
the exhaust port at the middle of the cylinder. During the latter
half of the stroke the pumps are forcing gas and air into space below
the piston, The compression being completed by the working piston and
an explosion occurring when the piston reaches its lowest position.
One of the interesting features of this engine was the use of spongy
platinum for ignition, though Barnett also devised an exceedingly
ingenious igniting cock of burning gas jets.
The
well known hot-tube method of ignition, which later became popular
and has only in comparatively recent times been supplanted by
electric ignition, was patented in America by Drake, and later, in
1855, by Newton, in England. The engine of Barsanti-Matteucci Engine,
patented in 1857, is interesting because it illustrates a type of
machine that was the first to achieve a real commercial success,
though that good fortune din not happen to its Italian inventors. It
is illustrated in Fig. 4. Gas and air were exploded under the piston,
which was driven upward, finally coming to a rest when all of the
work of the explosion had been done. The piston, descending under the
pressure of atmosphere, did the work. Lenoir, of France, patented in
1860, the first engine to attain considerable use. In general, it
resembled a double-acting steam engine, with a slide valve for the
admission and another for the exhaust. This engine was well
advertised and attained considerable use, though its economy was not
very good. It was deemed of sufficient merit, however, to secure
awards from the Exposition of London in 1862, of Paris in 1867, and
Vienna in 1873. The improvement on the Lenoir engine by Hugon brought
its inventor some prominence, but its success was short lived, as the
new Otto-Langen free-piston engine, which was exhibited at the Paris
Exposition in 1867, Carried all before it and held command of the
market for many years, during which time a large number were built.
The
Lenoir engine admitted gas and air for part of the stroke, after
which the explosion occurred and then an expansion. An indicator card
for this engine is shown in Fig. 5. All of these engines, it will be
noted, were non-compression engines. In 1860, Beau de Rochas stated
the conditions required for the efficiency of an internal-combustion
engine as follows:
1)
The greatest volume of the cylinder having a given surface of
periphery.
2)
Highest possible velocity of motion.
3)
Greatest possible expansion.
4)
Greatest possible pressure at commencement of the expansion.
Beau
de Rochas also described the four strokes, which makes the cycle of
what is known as the four-cycle engine.
To
the American the most interesting part of the development of
internal-combustion engines is that played by Brayton about 1872 to
1874. This engine is shown in Fig. 5. The Brayton engine was to some
extent the precursor of the present Diesel engine. The mixture of gas
and air burned at constant pressure and gave a card resembling
somewhat that of the steam engine. This engine was manufactured for a
while, but was not able to compete with the Otto-Langen free-piston
engine in economy. It was adapted for both gas and petroleum.
The
well-known Otto engine was invented by Dr. Nicholas Otto, of Germany,
and was patented in this country in 1877. It follows the cycle that
has been described by Beau de Rochas , now known as the four-cycle,
or sometimes as the Otto cycle. The engine was first known as the
Otto-Silent, to distinguish it from the free-piston engine, which was
rather noisy. It immediately established the internal-combustion
engine on a firm footing, and the engines of the four-cycle type sold
today show merely minor improvements. The sliding valve on 1876 has
been replaced by poppet valves, and the flame ignition has been
replaced by the electric spark. Otherwise, the Otto cycle of 1876 has
persisted and at this time thousands of them are being manufactured.
The
development of the Diesel engine for oil began about 1894. As has
been stated, this engine is similar to the Brayton. Air is compressed
to about 500 pounds pressure and oil is sprayed into this highly
compressed air. It burns spontaneously at nearly constant pressure,
which is followed by a long expansion. The extremely high temperature
of the air previous to the injection of the fuel, and the high
temperature maintained during this injection, together with the long
expansion, give the engine the highest efficiency of any thermal
motor. The development of the Diesel engine has been so recent that
it is not necessary to elaborate upon it. At this time, it is being
manufactured in all of the European countries and in America, and
there is a tendency on the part of many of the American manufacturers
who are bringing out new engines to adopt the features of the Diesel.
The gas turbine is as yet in the experimental stage. A number have
been built and are of course, extremely interesting. The success of
the steam turbine has encouraged many to believe that the gas turbine
will achieve similar success. Nothing of recent development can be
said to encourage this view. The difficulties in the way of
successful gas turbines are very great, and while some turbines have
been designed and run, none of them has shown an efficiency at all
comparable to that of ordinary four-cycle engines.
