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Model Enthusiasts - WHAT IS STEAM?
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WHAT IS STEAM? |
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What is a Steam Engine?
Definition:
steam engine:
machine for converting heat energy into mechanical energy using steam
as a medium, or working fluid. When water is converted into steam it
expands, its volume increasing about 1,600 times. The force produced by
the conversion is the basis of all steam engines. Steam engines operate
by having superheated steam force a piston to reciprocate, or move back
and forth, in a cylinder.
The piston is attached by a connecting rod to
a crankshaft that converts the back-and-forth motion of the piston to
rotary motion for driving machinery. A flywheel attached to the
crankshaft makes the rotary motion smooth and steady. The typical steam
engine has an inlet valve at each end of the cylinder. Steam is
admitted through one inlet valve, forcing the piston to move to the
other end of the cylinder.
This steam then exits through an exhaust
valve. Steam from the other inlet valve then pushes the piston back to
its original position, and the cycle starts again. In a single-cylinder
steam engine the exhaust steam is usually expelled directly into the
atmosphere. A compounded steam engine has several cylinders, which the
steam passes through successively until, leaving the last cylinder, it
is condensed into water and returned to the boiler.
From the Greek
inventor Heron of Alexandria to the Englishmen Thomas Newcomen and John
Cawley, many persons contributed to the work of harnessing steam.
However, James Watt's steam engine, patented in 1769, provided the
first practical solution. Earlier engines depended on atmospheric
pressure to push the piston into the cylinder, where a vacuum was
created by sudden cooling of its steam content. Watt's use of a
separate condenser resulted in a 75% saving in fuel. It also made
possible the use of steam pressure to move the piston in both
directions.
Watt's continuing efforts produced a governor, a mercury
steam gauge, and a crank-flywheel mechanism, all of which prepared the
steam engine for a major role in the Industrial Revolution. Sailing
vessels gave way to steamboats, and stagecoaches yielded to railroad
trains as the steam engine was perfected. Transmitted by belts, ropes,
shafts, pulleys, and gears, the energy from steam engines drove
machines in factories and mills.
Now, however, steam engines have been
replaced in most applications by more economical and efficient devices,
e.g., the steam turbine turbine, rotary engine that uses a continuous
stream of fluid (gas or liquid) to turn a shaft that can drive
machinery. A water, or hydraulic, turbine is used to drive electric
generators in hydroelectric power stations. The first such station was
built in Wisconsin in 1882. In a hydraulic turbine falling water
strikes a series of blades or buckets attached around a shaft, causing
the shaft to rotate, this motion in turn being used to drive the rotor
of an electric generator, the electric motor, and the
internal-combustion engine, including the diesel engine.
They are still
sufficiently economical to be used in industries where steam is
necessary for some purpose in addition to that of driving an engine
Now you are an expert too and so back
to the models!
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