Power machines
Energy is required to perform work
Originally, man had available only the force of his own muscles, but soon
learnt to use domestic animals to do work.
The oldest machines made the use of muscle power more effective.
Man exploited greater forces with the aid of machines driven by water or
wind. Increasing energy consumption led to the development of heatengines, which provided far more power.
Today we have at our disposal a great variety of engines fulfilling many
purposes.
Technically speaking, they are energy converters; historically, they have
revolutionized our lives.
Steam-power engines
In England at the end of the 17th century there was a growing need for
coal to produce iron and to heat the towns.
The search for a new, more powerful machine finally led to the invention of
the steam engine.
The essential parts of a steam engine are the cylinder and the piston
which moves inside it.
Steam, produced by firing coal in a boiler, is
conduced to the cylinder and provides a
driving force. The first "atmospheric" steam
engines were built in England at the beginning
of the 18th century.
More efficient steam turbines, internal
combustion engines and diesel engines were
invented and began to replace the steam
engine.
Precursors of Watt’s Steam Engine
Around 1650 Otto von Guericke experimented with vacuums and
discovered that the air – the atmospehre – exerts pressure.
Christian Huygens and, later, his assistant Denis Papin between 1674
and 1688 produced low pressure while experimenting with gunpowder
and made the air pressure perform work. In 1610 Papin succeeded in
constructing the first, although still imperfect, steam engine. Steam
production, reduced pressure and power stroke took place in one
cylinder.
Thomas Savery developed a steam
pump without a piston in 1698. The
steam pressure was produced in a
boiler. The low power output and high
fuel consumption of Papin’s and
Savery’s machines prevented them
from being put to practical use.
In 1711 Thomas Newcomen built the first steam engine that could be used. It
worked with atmospheric pressure. Steam and power cylinders were separate.
In 1765 John Smeaton improved the control mechanism and, thus, reduced
fuel consumption by one third. Newcomen’s steam engine drove nearly all
pumps in England’s mines and iron foundries until the end of the 18th century. It
was also exported to the Continent and to America.
Newcomen’s Piston-Operated Steam Engine
From 1712 onwards Thomas Newcomen built the
first piston-operated steam engines which could be
used for practical purposes. They were mainly
employed to pump pit water in mines.
Newcomen separated the steam generation from the
working cylinder. To generate the steam a spherical
boiler beneath the engine was used. The steams
flows into the cylinder and moves the piston
upwardly. Via a horizontal beam, the cartwright beam,
the pump rod is lowered. A counterweight supports
this movement. The actual work is done by the outer
air pressure. The steam in the cylinder is cooled and
condensed by injecting water. This generates a
partial vacuum. The higher outer pressure now
moves the piston downwards; via the cartwright beam
the pump rod is pulled upwards.
Watt's low-pressure Steam engine
The Scotsman, James Watt, tried to reduce the high coal consumption of
Newcomen's steam engine from 1764 onwards. Many experiments resulted in
an apparatus, patented in 1769, with the following innovations:
- heat insulation of the cylinder
- separate condenser to make cooling of the cylinder upon each stoke
unnecessary
- pumping out of the condensed water .
These improvements reduced fuel consumption by 60% and doubled the
engine's working speed. The first Watt engines produced only a to-and-fro and
not a rotary movement. From 1776 onwards thy worked as drainage pumps in
English mines and iron foundries. Watt made considerable efforts to transform
the to-and-fro movement of the piston into a rotary movement. The engine was
ready for building in 1781
Eisleben water raising machine, William Richards, Hettstedt, 1813
This engine was used until 1885 in Eisleben for pumping water out of a
copper mine. It is regarded as the oldest surviving steam engine in Germany.
The engine operates on Watt’s principle with low pressure. In one minute it can
raise about 2000 litres of waters from a depth of 40 meters.
Piston diameter: 930mm
Piston stroke: 2440 mm
Steam pressure: 1.7 bar
Piston stroke frequency: 12 p.m.
Ouput: 14.6kW (20HP)
James Watt’s industrial steam engine, Boulton & Watt, Soho, 1788
With this machine James Watt succeeded in making
the steam engine a universally applicable source
of power. The decisive innovations were: the engine
is double-acting, i.e. work is done both during the
upward and during the downward movement of the
piston. To transmit the rectilinear piston movement to
the beam, in 1784 Watt invented the parallelogram
linkage. To convert the beam motion to a rotary
motion Watt developed the sun-and-planet gear,
since patents prevented him from using the already
proven crank mechanism. For cooling the steam Watt
used injection condenser in which cold water is
squirted directly into the condenser .
Piston diameter: 475 mm
Piston drake: 1244 mm
Steam pressure: 1.5 bar
Number of revolutions: 48 rpm
Output: 9.5 kW (13HP)
Watt Trunk Boiler
This boiler was in operation from 1813 to about 1850 at
the Wimmelburg mine in Eisleben as steam generator
for the water raising machine. Trunk boilers, also
known as carriage boilers, were built for the first time in
1780 by James Watt. The boiler body is formed by
small hand-forged sheet metal pieces joined with rivets.
Attempts were made to seal the seams with lead,
hemp, tar and paper. To stop up remaining leaks on
starting up the boiler the feed water was mixed with
horse dung and bran. The boiler water passed from a
container located at a higher level by a gravity gradient
to the boiler. A float ensured the correct water level.
The firing was by hand by operating a slide in the flue.
In the middle of the 19th century trunk boilers ceased
to be of any significance on introduction of the water
tube boiler.
Original
Steam pressure: 1.3 bar
Weight: about 2,000 kg
The Steam Engine until the Mid-19th Century
James Watt’s patents lapsed in 1800. Thus, Watt’s engine could now be imitated and
improved everywhere. However, England continued to lead in the construction of steam
engines right up to the middle of the 19th century. The first steam engine outside England
either came from there or were illegal imitations. Independent steam engine construction
developed only gradually in Germany. Until about 1850 attempts were made to achieve a
high output and economic efficiency through:
- the use of gas iron instead of wood
- higher pressures
- various changes in construction
- experiments to replace the balancing lever
- multiple expansion of the steam
- replacement of the valves by slide valves.
The use of improved steam engines on ships and the building of the railway created new
traffic structures and opened up a new dimension of travel.
These are some examples of steam engines made outside England:
Factory Beam Steam
Engine,
Gutehoffnungshuette,
Sterkrade, 1835
Beam Steam Engine, Georg
Christian Freund, Berlin,
Germany, 1815
High-Pressure Steam
Engine with
Oscillating Cylinder,
1839
The Perfected Steam Engine
By about the middle of the 19th century the steam engine had become a familiar
sight. New scientific engineering methods, such as the exact understanding of
thermodynamic processes, governed its further development. About 1850
George H. Corliss succeeded in making the decisive step for reducing steam
consumption. His expansion control with cylindrical valve made it possible to
regulate the steam supply according to the particular engine load. At the end of
the eighteen sixties the Swiss company Maschinenfabrik Sulzer developed an
expansion steam engine with valve control.
The Americans Charles Porter and Horatio
Allen developed a high-speed steam engine.
From 1880 onwards these high-speed engines
became of great commercial importance,
because they were suitable for directly driving
electrical generators. In 1890 Wilhelm Schmidt
achieved a further increase in steam pressure by
superheating. The “hot steam” increased the
power output of steam engines by up to 30 %. By
about the turn of the century the development of
the steam engine could be considered
completed. In the first half of 19th century it was
gradually superseded by the internal combustion
engine, electric motor and steam turbine.
Maschinenbau Ferdinand Schichau, Elbing, 1883
This compact steam engine was a new development designed for warships. From 1884 to
1900 it drove the German torpedo boat "S1". The marine steam engine has 3 cylinders of
different sizes in which the steam is expanded in stages. It is first conducted into the smaller
high-pressure cylinder, then flows into the medium-pressure cylinder. In each case it does
work. The residual steam condenses in the copper surface condenser. Flat slide valves control
the steam inlet and outlet. For travelling astern the steam inlet direction can be reversed by
moving a lever over. The triple expansion engine is distinguished by its higher output, lower
coal consumption, lower construction weight and lower space requirement compared with
older marine engines. By 1885 it had been installed in all German torpedo boats.
High pressure
medium pressure
low pressure cylinder
Piston diameter
350mm
580 mm
840 mm
Piston stroke
400 mm
400 mm
400 mm
Steam pressure
12 bar
6 bar
1.4 bar
Speed
360 rpm
Power
750 kW (1000 HP)
Example of steam engines from the second half of 19th century:
Twin Compound Steam
Engine,
Maschinenbaugesellschaft
Karlsruhe, Karlsruhe, 1899
High-Speed Steam Engine
with Cock Control,
Dinglersche
Maschinenfabrik,
Zweibruecken, 1885
Superheated Steam
Tandem Engine,
Maschinenbau AG, form.
Beck und Henkel,
Kassel, 1894
Steam Motors
Steam motors are small usually fast-running piston steam engines. They were
used around 1900 to drive generators, compressors, pumps, hoisting equipment
and motor vehicles.
In 1949 the Spillingwerke manufactured this most modern form of the piston
steam engine. Today, small exhaust steam turbines of higher efficiency have
superseded the steam motor.
Depending on the number of cylinders and size steam motors delivered up to
750 kW. As regards their operating behavior they are very well suited as vehicle
engine, a change-speed gear not being necessary. So far, however, it has not
been possible to solve the problem of a cheap transportable steam generation
and the long start-up time.
Twin-Cylinder Steam Motor with Generator, Spilling Werke,
Hamburg, Germany, 1955
Spilling Werke, Hamburg, 1955
Orignial
High-pressure piston diameter: 145
mm
Low-pressure piston diameter: 205
mm
Piston stroke: 70 mm
Steam pressure: 18 and 6 bar
Speed: 1500 rpm
Output: 51 kW (70 PS)
For thousands of years men have to work without the help of
machines. But now we can not live without them...