Steam Engine Term paper
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The steam engine is a machine used for converting heat energy into mechanical energy,
using steam as the conversion medium. When water is boiled into steam its volume increases
about 1,600 times, producing a force that can be used to move a piston back and forth in a
cylinder. The piston is attached to a crankshaft that converts the piston's back-and-forth motion
into rotary motion for driving machinery. From the Greek inventor hero of Alexandria to the
Englishman Thomas Newcomen, many persons contributed to the work of harnessing steam.
However, James Watt's steam engine, patented 1769 offered the first practical solution by
providing a separate chamber for condensing the steam and by using steam pressure to move the
piston in both directions. These and other improvements by Watt prepared the steam engine for a
major role in manufacturing and transportation during the Industrial Revolution. Today steam
engines have been largely replaced by more efficient devices, for example, the steam turbine, the
electric motor, the international combustion.
Since the early 1900s, steam turbines have replaced most steam engines in large
electric-power plants (see ). Turbines are more efficient and more powerful than steam engines.
In most areas, steam locomotives have been supplanted by more reliable and economical
diesel-electric locomotives. Early steam automobiles have been superseded by cars powered by
lightweight, convenient, and more powerful gasoline and diesel engines. Because of all this,
steam engines today generally are regarded as museum pieces. Nonetheless, the invention of the
steam engine played a major role in the Industrial Revolution by creating a society less
dependent on animal power, waterwheels, and windmills
In 1690 the first steam piston engine was developed by French physicist Denis Papin for
pumping water. In this crude device a small amount of water was placed in a single cylinder over
a fire. As the water evaporated, the steam pressure forced a piston upward. The heat source was
then removed, allowing the steam to cool and condense. This created a partial vacuum (a
pressure below that of the atmosphere). Because the air located above the piston was at a higher
pressure (at atmospheric pressure), it would force the piston downward, performing work. More
practical devices powered by steam were the steam pump--patented in 1698 by the English
engineer Thomas Savery--and the so-called atmospheric steam engine--first built in 1712 by
Thomas Newcomen and John Calley. In the Newcomen engine, steam generated in a boiler was
fed into a cylinder located directly above the boiler. A piston was pulled to the top of the
cylinder by a counterweight. After the cylinder was filled with steam, water was injected into it,
causing the steam to condense. This reduced the pressure inside the cylinder and allowed the
outside air to push the piston back down. A chain-beam lever linkage was connected to a pump
rod, which lifted the pump plunger as the piston moved downward. Some modified Newcomen
engines were in service as late as 1800.
The Scottish instrument maker James Watt noticed that use of the same chamber for
alternating hot steam and cold condensate resulted in poor fuel utilization. In 1765 he devised a
separate water-cooled condenser chamber. It was equipped with a pump to maintain a partial
vacuum and periodically steam was fed from the cylinder through a valve. Watt and his business
partner, Matthew Boulton, sold these engines on the basis that one third of the fuel savings be
paid to them. The fuel costs for the Watt and Boulton engines were 75 percent less than those for
a similar Newcomen engine. Among Watt's many other improvements was the crankshaft, which
was used to produce rotating power; the use of double-acting pistons, by which steam was fed
alternately into the top and bottom sections of the piston-cylinder assembly to nearly double the
power output of a given engine; a governor, which regulated the flow of steam to the engine; and
the flywheel, which smoothed out the jerky action of the cylinders. Watt also recognized that
using high-pressure steam in the engine would be more economical than using steam at external
atmospheric pressure. Due to limitations in boiler design, however, his engines never operated at
high pressures.
Engines were further improved after the development of boilers that could operate at
higher pressures. By the end of the 18th century, two types of high-pressure boilers were in use:
water-tube boilers and fire-tube boilers. Their shells were made of iron plates fastened together
with rivets. In water-tube boilers, water was heated in coiled or vertical tubes that ran through
the fire chamber and received heat from the hot combustion gases. The steam would collect at
the top of the boilers. These boilers were the precursors of modern power-plant boilers. In
fire-tube boilers, the water was maintained in the lower portion of a large shell. The shell was
traversed by large pipes through which the combustion products passed from the fire grates to
the stack. Again, the steam collected at the top.
With improved boiler design, the British engineer Richard Trevithick built a
noncondensing steam-driven carriage in 1801 and the first steam locomotive in 1803, though its
boiler later exploded. In 1829 George Stephenson built his successful Rocket locomotive. It
contributed to the rapid expansion of railroads in Great Britain and, later, in other countries.
Steam propulsion of ships was tried successfully in 1787 by the American John Fitch,
who placed a steamboat on the Delaware River. In 1807 the American Robert Fulton built a
side-wheel paddle steamer called the Clermont. Equipped with a Watt and Boulton engine,
Fulton's Clermont, which was more economically successful than Fitch's endeavors, traveled
from New York City to Albany, ushering in the age of steamships.
At about the same time, noncondensing engines were also being developed by the
American inventor Oliver Evans. Largely due to Evans' initiative, high-pressure steam was
adopted in the United States much more readily than in Europe, though sometimes with
disastrous results. A large number of boiler explosions plagued river shipping in the United
States throughout much of the early 1900s.
The British inventor Arthur Woolf recognized that more power could be obtained from a
stationary engine by compounding--that is, by expanding the steam only partially in the first
cylinder and then further, to below atmospheric pressure in a second cylinder before passing it to
the condenser. As steam pressures continued to increase, such compound engines eventually
changed from double- to triple- and quadruple-compounding. The most famous engine of the
19th century was the twin-cylinder Corliss engine presented by George Corliss at the 1876
Centennial Exhibition in Philadelphia. Its cylinders were 40 inches (102 centimeters) in
diameter. Its stroke, the maximum distance of piston travel, was 10 feet (3 meters) and its
flywheel was 30 feet (9 meters) in diameter. Turning at 36 revolutions per minute, the Corliss
engine delivered 1,400 horsepower (1,044 kilowatts) to drive the 8,000 machines in Machinery
Hall. Within a decade a marine engine delivering more than 10,000 horsepower (7,460
kilowatts) had been built. Steam-engine development continued actively for another 50 years.
In 1897 the first automobiles to be driven successfully by noncondensing, steam-driven
engines were built by Francis E. and Freelan O. Stanley in Newton, Mass. (see ). These
steam-driven cars were more powerful than the first gasoline-driven vehicles. They eventually
used boiler pressures of up to 1,000 pounds per square inch (6,895 kilopascals). Although
condensers had been added by 1915, steam-driven automobiles were to face their demise shortly
thereafter, largely due to the engine's enormous weight, low efficiency, and constant need of
attention.
Before the advent of small electric motors, steam engines powered most manufacturing plants. A
single, centrally located engine delivered power to machines by means of shafts, pulleys, and
belts. Farms in the United States used steam-powered tractors. Self-propelled steam-driven
threshing machines moved from farm to farm during the harvesting season until they were
replaced by gasoline- or diesel-driven units.
Steam engines eventually became too large, heavy, and slow to meet the steadily increasing
demand for more power from a single unit. Following the successful design...
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