International Combustion

By Staff
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The inherent complexity of the steam engine – with its attendant
furnace, boiler, pumps, coal bunkers, ash pans, and myriad other
adjuncts – and the necessity of employing a licensed engineer
full-time were defects obvious to users and manufacturers of steam
power. The constant threat of boiler explosion was a source of
anxiety to the general public too. As a result, inventors sought to
harness energy sources based on some completely different principle
– sources able at least to compete with steam, and ideally to
supplant it. When suited to the particular situation and where
available, water power was employed, and, to a far less extent,
wind. Both had topographical and geographical limitations that
excluded them from anything like universal use.

The most attractive alternative energy source was the explosive
power locked in such combustible substances as gunpowder, gas, and
a variety of liquid vapors. Systems were developed to burn such
fuels directly in the cylinder of an engine based loosely on the
steam engine, the pressure resulting from the combustion forcing a
piston out of the cylinder – a notion suggested, of course, by the
cannon. Throughout the 19th century a host of inventors struggled
to find better fuels, to develop means for introducing just

the right amount of fuel into the cylinder in a cycle that would
produce continuous motion, to discover the best way of igniting the
fuel at precisely the right moment, to control the explosive
violence of combustion, and to solve innumerable other problems
that stood in the way of a successful internal combustion

By the 1840’s several engines had been invented that burned
either illuminating (coal) gas or volatile liquids. They operated
poorly. Not until 1860 was one invented that became commercially
successful: a gas engine patented by J. J. E. Lenoir of Paris.
Hundreds of Lenoir engines were built in France and England for
light industrial applications. They were able to compete with steam
engines – even though the latter were far more efficient – because
they could be started instantly, they consumed no fuel when not
actually working, they occupied much less space, and they were free
from the danger of explosion.

It was not the Frenchman Lenoir, however, but the German
Nikolaus August Otto who solidified the position of internal
combustion as an important source of mechanical power. In 1867 an
engine designed by Otto and his associate Eugen Langen was shown at
the Paris Exposition. Tests revealed that its gas consumption was
about half that of the Lenoir engine and another competing

Although makers of steam engines and boilers scarcely had much
cause for alarm, by the time of the Centennial internal combustion
engines were being sold in considerable numbers. As at Paris nine
years earlier, three engines were shown at Philadelphia: one
French, one German and one American. The judges gave the Mignon
& Rouart ‘Noiseless Gas Motor’ a somewhat left-handed
award, praising its simplicity of construction, and declaring it
capable of rendering ‘good service in cases where economy of
gas is not of the first importance.’ To be taken more
seriously, though, were the other two engines. One was the Otto
& Langen, successful for nearly ten years and on the verge of
giving way to Otto’s four-stroke-cycle engine. The other was
the Brayton Engine, the first practical liquid-fueled internal
combustion engine. It was the dawn of an era.

Brayton Ready Motor or Hydrocarbon Engine

While the gas engine delivered its users from the encumbrances
of the steam engine, it was still, in large cities, tied to the gas
mains. Matters were even worse in isolated areas, where anyone
using a gas engine had to install a gas generator. This was as
massive and potentially dangerous as any steam boiler, and thereby
negated much of internal combustion’s advantage. Thus there was
a clear inducement to develop an internal combustion engine fueled
with combustible liquid. Several inventors came up with designs,
more or less successful, that burned the volatile petroleum
fractions in the range of what today we know as gasoline. But the
capricious behavior of such fuels did little to inspire confidence
in these machines.

In 1872 George Brayton of Exeter, New Hampshire, patented an
engine capable of burning the heavier, safer fractions in the
kerosene range, then in wide use as illuminants. This oil was
atomized and sprayed into the cylinder by a charge of compressed
air. When ignited, the charge of burning gas exerted a practically
constant pressure on the piston, much like the action in a steam
engine. This cycle of constant cylinder pressure came to be known
as the Brayton Cycle, and is that on which modern gas turbines

Brayton engines were built in a number of forms, and sold by
several firms under license. The chief selling point was safety and
convenience, their fuel economy being about midway between the
Lenoir and the Otto & Langen. The Centennial judges were
impressed, describing the Brayton engine as ‘a new system for
generating power, of great interest and promise, and which is so
far developed as to have attained a very satisfactory degree of
practical success.’ Since it could operate free of gas mains,
attempts were later made to propel boats and streetcars with
Brayton engines.

Otto & Langen Atmospheric Gas Engine

Nikolaus Otto achieved success by employing a concept that had
attracted inventors from the first. He did not explode a charge of
combustible fuel in the cylinder and harness the force of the
piston as it was driven out. Rather, as a means of fully utilizing
the expansion of the burning gasses within the cylinder, Otto
embraced the ‘atmospheric’ principle. Here, a gas-air
mixture, when ignited, drove a ‘free piston’ up a long
vertical cylinder, as far as the explosion would carry it, doing no
work on the upstroke. By the time the piston had reached the top of
the cylinder, the gasses below had cooled to the extent that a
partial vacuum was formed, into which the piston was then driven
with considerable force by the atmospheric pressure above plus its
own weight. These forces were harnessed, through a rack on the
piston rod that engaged a pinion on the drive shaft, which was
turned as the piston and rack descended.

The success of the Otto & Langen engine was due in large
part to the ingenuity of its mechanical details, especially the
slide valve that admitted a measured charge of gas and ignited it
from an open flame outside the valve, and the clutch mechanism that
not only allowed the piston to rise freely but also, in starting,
raised it slightly to draw in the initial charge. Combining the
inherent advantages of internal combustion with economy,
reliability and excellence of design, the engine sold well. N. A.
Otto & Co. of Cologne (later Gasmotorenfabrik Deutz) built more
than 5,000, and many others were produced by the English licensees,
Crossley Bros, of Manchester. The engine shown in 1876 is a
Crossley, of about one horsepower capacity.

‘Otto Silent’ Engine

Even while his ‘atmospheric’ engines were successfully
spreading the gospel of internal combustion power, Otto knew that
it should be possible to extract more of the theoretical energy in
the gas. This, obviously, would further improve the competitive
position of internal combustion vis-a-vis steam, particularly in
large-size engines where fuel economy was especially important.

In 1876, after fifteen years of experimentation-and just a bit
too late to exhibit at the Centennial-he finished and patented a
new engine. Its gas-air mixture was drawn into the cylinder, then
compressed by the piston impelled by the momentum of the flywheel,
and then ignited, driving the piston back again in a ‘power
stroke.’ In a final inward stroke of the piston, the burned
gasses were driven out of the cylinder or ‘exhausted.’
These four distinct processes, each occurring during one stroke of
the piston, gave to the engine the term,
‘four-stroke-cycle’ (since shortened to ‘four
cycle’). The key to the engine’s greater thermal efficiency
was the compression of the fuel mixture, which greatly increased
the force of the explosion.

The increase was sufficiently dramatic, in fact, that for the
first time internal combustion was placed on a soundly competitive
footing with steam. The Otto four-stroke engine was put immediately
into production, and shown publicly at the Paris Exposition of
1878. Its obvious merits drove from the market all engines of the
Lenoir and Otto & Langen types. An advantage nearly as
important as its economy was its mechanical simplicity compared to
the clattery Otto & Langen engine, although the slide valve and
open-flame ignition system of the ‘Otto Silent’ were
adapted from the Otto & Langen.

Licensees around the world built Otto engines for every
conceivable light service. The engine displayed in 1876 is an early
product of Schleic-her, Schumm & Co. of Philadelphia, the
American licensee. Built in 1882, it produced four horsepower at
160 rpm, and is virtually identical to the engines of the period
built by Gas motorenfabrik Deutz.

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