Internal combustion engine

The invention: The most common type of engine in automobiles
and many other vehicles, the internal combusion engine is characterized
by the fact that it burns its liquid fuelly internally—in
contrast to engines, such as the steam engine, that burn fuel in external
furnaces.
The people behind the invention:
Sir Harry Ralph Ricardo (1885-1974), an English engineer
Oliver Thornycroft (1885-1956), an engineer and works manager
Sir David Randall Pye (1886-1960), an engineer and
administrator
Sir Robert Waley Cohen (1877-1952), a scientist and industrialist
The Internal Combustion Engine: 1900-1916
By the beginning of the twentieth century, internal combustion
engines were almost everywhere. City streets in Berlin, London,
and New York were filled with automobile and truck traffic; gasoline-
and diesel-powered boat engines were replacing sails; stationary
steam engines for electrical generation were being edged out by
internal combustion engines. Even aircraft use was at hand: To
progress from theWright brothers’ first manned flight in 1903 to the
fighting planes ofWorldWar I took only a little more than a decade.
The internal combustion engines of the time, however, were
primitive in design. They were heavy (10 to 15 pounds per output
horsepower, as opposed to 1 to 2 pounds today), slow (typically
1,000 or fewer revolutions per minute or less, as opposed to 2,000 to
5,000 today), and extremely inefficient in extracting the energy content
of their fuel. These were not major drawbacks for stationary applications,
or even for road traffic that rarely went faster than 30 or
40 miles per hour, but the advent of military aircraft and tanks demanded
that engines be made more efficient.Engine and Fuel Design
Harry Ricardo, son of an architect and grandson (on his mother’s
side) of an engineer, was a central figure in the necessary redesign of
internal combustion engines. As a schoolboy, he built a coal-fired
steam engine for his bicycle, and at Cambridge University he produced
a single-cylinder gasoline motorcycle, incorporating many of
his own ideas, which won a fuel-economy competition when it traveled
almost 40 miles on a quart of gasoline. He also began development
of a two-cycle engine called the “Dolphin,” which later was
produced for use in fishing boats and automobiles. In fact, in 1911,
Ricardo took his new bride on their honeymoon trip in a Dolphinpowered
car.
The impetus that led to major engine research came in 1916
when Ricardo was an engineer in his family’s firm. The British
government asked for newly designed tank engines, which had to
operate in the dirt and mud of battle, at a tilt of up to 35 degrees,
and could not give off telltale clouds of blue oil smoke. Ricardo
solved the problem with a special piston design and with air circulation
around the carburetor and within the engine to keep the oil
cool.
Design work on the tank engines turned Ricardo into a fullfledged
research engineer. In 1917, he founded his own company,
and a remarkable series of discoveries quickly followed. He investigated
the problem of detonation of the fuel-air mixture in the internal
combustion cylinder. The mixture is supposed to be ignited
by the spark plug at the top of the compression stroke, with a controlled
flame front spreading at a rate about equal to the speed of
the piston head as it moves downward in the power stroke. Some
fuels, however, detonated (ignited spontaneously throughout the
entire fuel-air mixture) as a result of the compression itself, causing
loss of fuel efficiency and damage to the engine.
With the cooperation of RobertWaley Cohen of Shell Petroleum,
Ricardo evaluated chemical mixtures of fuels and found that paraffins
(such as n-heptane, the current low-octane standard) detonated
readily, but aromatics such as toluene were nearly immune to detonation.
He established a “toluene number” rating to describe the
tendency of various fuels to detonate; this number was replaced in the 1920’s by the “octane number” devised by Thomas Midgley at
the Delco laboratories in Dayton, Ohio.
The fuel work was carried out in an experimental engine designed
by Ricardo that allowed direct observation of the flame front
as it spread and permitted changes in compression ratio while the
engine was running. Three principles emerged from the investigation:
the fuel-air mixture should be admitted with as much turbulence
as possible, for thorough mixing and efficient combustion; the
spark plug should be centrally located to prevent distant pockets of
the mixture from detonating before the flame front reaches them;
and the mixture should be kept as cool as possible to prevent detonation.
These principles were then applied in the first truly efficient sidevalve
(“L-head”) engine—that is, an engine with the valves in a
chamber at the side of the cylinder, in the engine block, rather than
overhead, in the engine head. Ricardo patented this design, and after
winning a patent dispute in court in 1932, he received royalties
or consulting fees for it from engine manufacturers all over the
world.Impact
The side-valve engine was the workhorse design for automobile
and marine engines until after World War II. With its valves actuated
directly by a camshaft in the crankcase, it is simple, rugged,
and easy to manufacture. Overhead valves with overhead camshafts
are the standard in automobile engines today, but the sidevalve
engine is still found in marine applications and in small engines
for lawn mowers, home generator systems, and the like. In its
widespread use and its decades of employment, the side-valve engine
represents a scientific and technological breakthrough in the
twentieth century.
Ricardo and his colleagues, Oliver Thornycroft and D. R. Pye,
went on to create other engine designs—notably, the sleeve-valve
aircraft engine that was the basic pattern for most of the great British
planes of World War II and early versions of the aircraft jet engine.
For his technical advances and service to the government, Ricardo
was elected a Fellow of the Royal Society in 1929, and he was
knighted in 1948.