History of the Steam Engine
The first steam-powered machine was built in 1698 by the English military
engineer Thomas Savery (c. 1650-1715). His invention, designed to pump
water out of coal mines, was known as the Miner's Friend. The machine,
which had no moving parts, consisted of a simple boiler - a steam chamber
whose valves were located on the surface - and a pipe leading to the water in
the mine below. Water was heated in the boiler chamber until its steam filled
the chamber, forcing out any remaining water or air. The valves were then
closed and cold water was sprayed over the chamber. This chilled and
condensed the steam inside to form a vacuum. When the valves were
reopened, the vacuum sucked up the water from the mine, and the process
could then be repeated.
A few years later, an English engineer named Thomas Newcomen improved
the steam pump. He increased efficiency by setting a moving piston inside a
cylinder, a technique still in use today. A cylinder - a long, thin, closed
chamber separate from the boiler - replaced the large, open boiler chamber.
A piston - a sliding piece that fits in the cylinder - was used to create motion
instead of a vacuum. Steam filled the cylinder from an open valve. When
filled, the cylinder was sprayed with water, causing the steam inside to
condense into water and create a partial vacuum. The pressure of the outside
air then forced the piston down, producing a power stroke. The piston was
connected to a beam, which was connected to a water pump at the bottom of
the mine by a pump-rod. Through these connections, the movement of the
piston caused the water pump to suck up the water.
The most important improvement in steam engine design was brought about
by the Scottish engineer James Watt. He set out to improve the performance
of Newcomen's engine and by 1769 had arrived at the conclusion: if the
steam were condensed separately from the cylinder, the cylinder could
always be kept hot. That year he introduced the design of a steam engine that
had a separate condenser and sealed cylinders. Since this kept the heating
and cooling processes separate, his machine could work constantly, without
any long pause at each cycle to reheat the cylinder. Watt's refined steam
engine design
used one-third less fuel than a comparable Newcomen engine.
Over the next 15 years, Watt continued to improve his engine and made
three significant additions. He introduced the centrifugal governor, a device
that could control steam output and engine speed. He made the engine
double-acting by allowing steam to enter alternately on either side of the
piston. This allowed the engine to work rapidly and deliver power on the
downward and upward piston stroke. Most important, he attached a flywheel
to the engine.
Flywheels allow the engine to run more smoothly by creating a more
constant load, and they convert the conventional back-and-forth power
stroke into a circular (rotary) motion that can be adapted more readily to
power machinery. By 1790, Watt's improved steam engine offered a
powerful, reliable power source that could be located almost anywhere. It
was used to pump bellows for blast furnaces, to power huge hammers for
shaping and strengthening forged metals, and to turn machinery at textile
mills. More than anything, it was Watt's steam engine that speeded up the
Industrial Revolution both in England and the rest of the world.
Steam was successfully adapted to powerboats in 1802 and railways in 1829.
Later, some of the first automobiles were powered by steam. In the 1880s,
the English engineer Charles A. Parsons produced the first steam turbine, a
new steam technology that was more efficient and which enabled the steam
engine to evolve into a highly sophisticated and powerful engine that
propelled huge ships and ran turbogenerators that supplied electricity.
Once the dominant power source, steam engines eventually declined in
popularity as other power sources became available. Although there were
more than 60,000 steam cars made in the United States between 1897 and
1927, the steam engine eventually gave way to the internal combustion
engine as a power source for vehicles.
