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...