Steam engine

A model of a beam engine featuring James Watt's parallel linkage for double action.[1]
A mill engine from Stott Park Bobbin Mill, Cumbria, England
A steam locomotive from East Germany. This class of engine was built in 1942–1950 and operated until 1988.

A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force is transformed, by a connecting rod and flywheel, into rotational force for work. The term "steam engine" is generally applied only to reciprocating engines as just described, not to the steam turbine.

Steam engines are external combustion engines,[2] where the working fluid is separated from the combustion products. The ideal thermodynamic cycle used to analyze this process is called the Rankine cycle.

In general usage, the term steam engine can refer to either complete steam plants (including boilers etc.) such as railway steam locomotives and portable engines, or may refer to the piston or turbine machinery alone, as in the beam engine and stationary steam engine.

Steam-driven devices were known as early as the aeliopile in the first century AD, with a few other uses recorded in the 16th and 17th century. Thomas Savery's dewatering pump used steam pressure operating directly on water. The first commercially-successful engine that could transmit continuous power to a machine was developed in 1712 by Thomas Newcomen. James Watt made a critical improvement by removing spent steam to a separate vessel for condensation, greatly improving the amount of work obtained per unit of fuel consumed. By the 19th century, stationary steam engines powered the factories of the Industrial Revolution. Steam engines replaced sail for ships, and steam locomotives operated on the railways.

Reciprocating piston type steam engines were the dominant source of power until the early 20th century, when advances in the design of electric motors and internal combustion engines gradually resulted in the replacement of reciprocating (piston) steam engines in commercial usage. Steam turbines replaced reciprocating engines in power generation, due to lower cost, higher operating speed, and higher efficiency.[3]


Early experiments

The first recorded rudimentary steam-powered "engine" was the aeolipile described by Hero of Alexandria, a mathematician and engineer in Roman Egypt in the first century AD.[4] In the following centuries, the few steam-powered "engines" known were, like the aeolipile,[5] essentially experimental devices used by inventors to demonstrate the properties of steam. A rudimentary steam turbine device was described by Taqi al-Din[6] in Ottoman Egypt in 1551 and by Giovanni Branca[7] in Italy in 1629.[8] Jerónimo de Ayanz y Beaumont received patents in 1606 for 50 steam powered inventions, including a water pump for draining inundated mines.[9] Denis Papin, a Huguenot refugee, did some useful work on the steam digester in 1679, and first used a piston to raise weights in 1690.[10]

Pumping engines

The first commercial steam-powered device was a water pump, developed in 1698 by Thomas Savery.[11] It used condensing steam to create a vacuum which raised water from below and then used steam pressure to raise it higher. Small engines were effective though larger models were problematic. They had a limited lift height and were prone to boiler explosions. Savery's engine was used in mines, pumping stations and supplying water to water wheels that powered textile machinery.[12] Savery engine was of low cost. Bento de Moura Portugal introduced an improvement of Savery's construction "to render it capable of working itself", as described by John Smeaton in the Philosophical Transactions published in 1751.[13] It continued to be manufactured until the late 18th century.[14] One engine was still known to be operating in 1820.[15]

Piston steam engines

Jacob Leupold Steam engine 1720

The first commercially-successful engine that could transmit continuous power to a machine, was the atmospheric engine, invented by Thomas Newcomen around 1712.[16][17] It improved on Savery's steam pump, using a piston as proposed by Papin. Newcomen's engine was relatively inefficient, and mostly used for pumping water. It worked by creating a partial vacuum by condensing steam under a piston within a cylinder. It was employed for draining mine workings at depths hitherto impossible, and for providing reusable water for driving waterwheels at factories sited away from a suitable "head". Water that passed over the wheel was pumped up into a storage reservoir above the wheel.[18]

In 1720 Jacob Leupold described a two-cylinder high-pressure steam engine.[19] The invention was published in his major work "Theatri Machinarum Hydraulicarum".[20] The engine used two heavy pistons to provide motion to a water pump. Each piston was raised by the steam pressure and returned to its original position by gravity. The two pistons shared a common four way rotary valve connected directly to a steam boiler.

Early Watt pumping engine

The next major step occurred when James Watt developed (1763–1775) an improved version of Newcomen's engine, with a separate condenser. Boulton and Watt's early engines used half as much coal as John Smeaton's improved version of Newcomen's.[21] Newcomen's and Watt's early engines were "atmospheric". They were powered by air pressure pushing a piston into the partial vacuum generated by condensing steam, instead of the pressure of expanding steam. The engine cylinders had to be large because the only usable force acting on them was atmospheric pressure.[18][22]

Watt developed his engine further, modifying it to provide a rotary motion suitable for driving machinery. This enabled factories to be sited away from rivers, and accelerated the pace of the Industrial Revolution.[22][23][24]

High-pressure engines

The meaning of high pressure, together with an actual value above ambient, depends on the era in which the term was used. For early use of the term Van Reimsdijk[25] refers to steam being at a sufficiently high pressure that it could be exhausted to atmosphere without reliance on a vacuum to enable it to perform useful work. Ewing 1894, p. 22 states that Watt's condensing engines were known, at the time, as low pressure compared to high pressure, non-condensing engines of the same period.

Watt's patent prevented others from making high pressure and compound engines. Shortly after Watt's patent expired in 1800, Richard Trevithick and, separately, Oliver Evans in 1801[24][26] introduced engines using high-pressure steam; Trevithick obtained his high-pressure engine patent in 1802,[27] and Evans had made several working models before then.[28] These were much more powerful for a given cylinder size than previous engines and could be made small enough for transport applications. Thereafter, technological developments and improvements in manufacturing techniques (partly brought about by the adoption of the steam engine as a power source) resulted in the design of more efficient engines that could be smaller, faster, or more powerful, depending on the intended application.[18]

The Cornish engine was developed by Trevithick and others in the 1810s.[29] It was a compound cycle engine that used high-pressure steam expansively, then condensed the low-pressure steam, making it relatively efficient. The Cornish engine had irregular motion and torque though the cycle, limiting it mainly to pumping. Cornish engines were used in mines and for water supply until the late 19th century.[30]

Horizontal stationary engine

Early builders of stationary steam engines considered that horizontal cylinders would be subject to excessive wear. Their engines were therefore arranged with the piston axis vertical. In time the horizontal arrangement became more popular, allowing compact, but powerful engines to be fitted in smaller spaces.

The acme of the horizontal engine was the Corliss steam engine, patented in 1849, which was a four-valve counter flow engine with separate steam admission and exhaust valves and automatic variable steam cutoff. When Corliss was given the Rumford Medal, the committee said that "no one invention since Watt's time has so enhanced the efficiency of the steam engine".[31] In addition to using 30% less steam, it provided more uniform speed due to variable steam cut off, making it well suited to manufacturing, especially cotton spinning.[18][24]

Road vehicles

Steam powered road-locomotive from England

The first experimental road going steam powered vehicles were built in the late 18th century, but it was not until after Richard Trevithick had developed the use of high-pressure steam, around 1800, that mobile steam engines became a practical proposition. The first half of the 19th century saw great progress in steam vehicle design, and by the 1850s it was becoming viable to produce them on a commercial basis. This progress was dampened by legislation which limited or prohibited the use of steam powered vehicles on roads. Improvements in vehicle technology continued from the 1860s to the 1920s. Steam road vehicles were used for many applications. In the 20th century, the rapid development of internal combustion engine technology led to the demise of the steam engine as a source of propulsion of vehicles on a commercial basis, with relatively few remaining in use beyond the Second World War. Many of these vehicles were acquired by enthusiasts for preservation, and numerous examples are still in existence. In the 1960s the air pollution problems in California gave rise to a brief period of interest in developing and studying steam powered vehicles as a possible means of reducing the pollution. Apart from interest by steam enthusiasts, the occasional replica vehicle, and experimental technology no steam vehicles are in production at present.

Marine engines

A triple-expansion marine steam engine on the 1907 oceangoing tug Hercules

Near the end of the 19th century compound engines came into widespread use. Compound engines exhausted steam in to successively larger cylinders to accommodate the higher volumes at reduced pressures, giving improved efficiency. These stages were called expansions, with double- and triple-expansion engines being common, especially in shipping where efficiency was important to reduce the weight of coal carried.[18] Steam engines remained the dominant source of power until the early 20th century, when advances in the design of the steam turbine, electric motors and internal combustion engines gradually resulted in the replacement of reciprocating (piston) steam engines, with shipping in the 20th-century relying upon the steam turbine.[18][3]

Steam locomotives

Vintage image of steam train

As the development of steam engines progressed through the 18th century, various attempts were made to apply them to road and railway use.[32] In 1784, William Murdoch, a Scottish inventor, built a prototype steam road locomotive.[33] An early working model of a steam rail locomotive was designed and constructed by steamboat pioneer John Fitch in the United States probably during the 1780s or 1790s.[34] His steam locomotive used interior bladed wheels guided by rails or tracks.

The first full-scale working railway steam locomotive was built by Richard Trevithick in the United Kingdom and, on 21 February 1804, the world's first railway journey took place as Trevithick's unnamed steam locomotive hauled a train along the tramway from the Pen-y-darren ironworks, near Merthyr Tydfil to Abercynon in south Wales.[32][35][36] The design incorporated a number of important innovations that included using high-pressure steam which reduced the weight of the engine and increased its efficiency. Trevithick visited the Newcastle area later in 1804 and the colliery railways in north-east England became the leading centre for experimentation and development of steam locomotives.[37]

Trevithick continued his own experiments using a trio of locomotives, concluding with the Catch Me Who Can in 1808. Only four years later, the successful twin-cylinder locomotive Salamanca by Matthew Murray was used by the edge railed rack and pinion Middleton Railway.[38] In 1825 George Stephenson built the Locomotion for the Stockton and Darlington Railway. This was the first public steam railway in the world and then in 1829, he built The Rocket which was entered in and won the Rainhill Trials.[39] The Liverpool and Manchester Railway opened in 1830 making exclusive use of steam power for both passenger and freight trains.

Steam locomotives continued to be manufactured until the late twentieth century in places such as China and the former East Germany (where the DR Class 52.80 was produced).[40]

Steam turbines

The final major evolution of the steam engine design was the use of steam turbines starting in the late part of the 19th century. Steam turbines are generally more efficient than reciprocating piston type steam engines (for outputs above several hundred horsepower), have fewer moving parts, and provide rotary power directly instead of through a connecting rod system or similar means.[41] Steam turbines virtually replaced reciprocating engines in electricity generating stations early in the 20th century, where their efficiency, higher speed appropriate to generator service, and smooth rotation were advantages. Today most electric power is provided by steam turbines. In the United States 90% of the electric power is produced in this way using a variety of heat sources.[3] Steam turbines were extensively applied for propulsion of large ships throughout most of the 20th century.

Present development

Although the reciprocating steam engine is no longer in widespread commercial use, various companies are exploring or exploiting the potential of the engine as an alternative to internal combustion engines. The company Energiprojekt AB in Sweden has made progress in using modern materials for harnessing the power of steam. The efficiency of Energiprojekt's steam engine reaches some 27–30% on high-pressure engines. It is a single-step, 5-cylinder engine (no compound) with superheated steam and consumes approx. 4 kg (8.8 lb) of steam per kWh.[42][not in citation given]

Other Languages
Afrikaans: Stoomenjin
Alemannisch: Dampfmaschine
العربية: محرك بخاري
aragonés: Maquina de vapor
অসমীয়া: ভাপ ইঞ্জিন
azərbaycanca: Buxar maşını
Bân-lâm-gú: Cheng-khì ki-koan
башҡортса: Пар машинаһы
беларуская (тарашкевіца)‎: Парасілавая ўстаноўка
български: Парна машина
bosanski: Parna mašina
čeština: Parní stroj
Cymraeg: Peiriant ager
Deutsch: Dampfmaschine
eesti: Aurumasin
Ελληνικά: Ατμομηχανή
Esperanto: Vapormaŝino
euskara: Lurrun-makina
Gaeilge: Inneall gaile
Gàidhlig: Inneal-smùide
한국어: 증기기관
հայերեն: Շոգեմեքենա
हिन्दी: भाप का इंजन
hrvatski: Parni stroj
Bahasa Indonesia: Mesin uap
interlingua: Motor de vapor
íslenska: Gufuvél
italiano: Motore a vapore
ಕನ್ನಡ: ಉಗಿಯಂತ್ರ
қазақша: Бу машинасы
Kiswahili: Injini ya mvuke
Кыргызча: Буу машинасы
latviešu: Tvaika dzinējs
lietuvių: Garo mašina
magyar: Gőzgép
македонски: Парна машина
മലയാളം: ആവിയന്ത്രം
Bahasa Melayu: Enjin wap
монгол: Уурын машин
Nederlands: Stoommachine
नेपाल भाषा: स्टिम इन्जिन
日本語: 蒸気機関
norsk: Dampmaskin
norsk nynorsk: Dampmaskin
oʻzbekcha/ўзбекча: Bugʻ mashinasi
Patois: Stiim injin
português: Motor a vapor
română: Motor cu abur
Runa Simi: Wapsi kuyuchina
русиньскый: Парова машына
Simple English: Steam engine
slovenčina: Parný stroj
slovenščina: Parni stroj
српски / srpski: Парна машина
srpskohrvatski / српскохрватски: Parna mašina
suomi: Höyrykone
svenska: Ångmaskin
татарча/tatarça: Bu yörtkeçe (maşina)
Türkçe: Buhar makinesi
українська: Парова машина
ئۇيغۇرچە / Uyghurche: ھور ماشىنىسى
vepsän kel’: Purumašin
Tiếng Việt: Động cơ hơi nước
Võro: Aurumoodor
吴语: 蒸汽机
ייִדיש: דאמפמאטאר
粵語: 蒸氣機
中文: 蒸汽机