Examine individual changes

' {{about|a machine to convert energy into useful mechanical motion|other uses of engine|Engine (disambiguation)|other uses of motor|Motor (disambiguation)}} [[Image:Mercedes V6 DTM Rennmotor 1996.jpg|thumb|upright=1.2|A V6 [[internal combustion engine]] from a [[Mercedes-Benz|Mercedes car]]]] An '''engine''' or '''motor''' is a [[machine]] designed to convert [[energy]] into useful [[Motion (physics)|mechanical motion]].<ref>{{cite web|url=http://dictionary.reference.com/browse/motor |title=Motor |quote=a person or thing that imparts motion, esp. a contrivance, as a steam engine, that receives and modifies energy from some natural source in order to utilize it in driving machinery. |publisher=Dictionary.reference.com |date= |accessdate=2011-05-09}}</ref><ref>[http://dictionary.reference.com/browse/motor Dictionary.com: (World heritage)] "3. any device that converts another form of energy into mechanical energy so as to produce motion"</ref> [[Heat engine]]s, including [[internal combustion engine]]s and [[external combustion engine]]s (such as [[steam engine]]s) burn a [[fuel]] to create [[heat]], which then creates motion. [[Electric motor]]s convert electrical energy into [[machine (mechanical)|mechanical]] motion, [[pneumatic motor]]s use [[compressed air]] and others—such as [[clockwork motor]]s in [[wind-up toy]]s—use [[elastic energy]]. In biological systems, [[molecular motor]]s, like [[myosin]]s in [[muscle]]s, use [[chemical energy]] to create motion. ==Terminology== "Engine" was originally a term for any mechanical device that converts force into motion. Hence, pre-industrial weapons such as [[catapult]]s, [[trebuchet]]s and [[battering ram]]s were called "[[siege engine]]s". The word "gin," as in "[[cotton gin]]", is short for "engine." The word derives from [[Old French]] ''[[wikt:engin|engin]]'', from the [[Latin]] ''ingenium'', which is also the root of the word ''[[wikt:ingenious|ingenious]]''. Most mechanical devices invented during the [[industrial revolution]] were described as engines—the steam engine being a notable example. In modern usage, the term ''engine'' typically describes devices, like steam engines and internal combustion engines, that burn or otherwise consume fuel to perform [[mechanical work]] by exerting a [[torque]] or linear force to drive machinery that generates [[electricity]], [[pump]]s water, or [[gas compressor|compresses gas]]. In the context of propulsion systems, an air-breathing engine is one that uses atmospheric air to oxidise the fuel rather than supplying an independent oxidizer, as in a [[rocket]]. When the internal combustion engine was invented, the term "motor" was initially used to distinguish it from the steam engine—which was in wide use at the time, powering locomotives and other vehicles such as [[steamroller|steam rollers]]. "Motor" and "engine" later came to be used interchangeably in casual discourse. However, technically, the two words have different meanings. An ''[[wiktionary:engine|engine]]'' is a device that [[combustion|burns]] or otherwise consumes fuel, changing its chemical composition, whereas a motor is a device driven by electricity, which does not change the chemical composition of its energy source.<ref>"Engine", ''McGraw-Hill Concise Encyclopedia of Science and Technology'', Third Edition, Sybil P. Parker, ed. McGraw-Hill, Inc., 1994, p. 714.</ref> A heat engine may also serve as a ''[[wiktionary:prime mover|prime mover]]''—a component that transforms the flow or changes in pressure of a [[Fluid mechanics|fluid]] into [[mechanical energy]].<ref>"Prime mover", ''McGraw-Hill Concise Encyclopedia of Science and Technology'', Third Edition, Sybil P. Parker, ed. McGraw-Hill, Inc., 1994, p. 1498.</ref> An [[automobile]] powered by an internal combustion engine may make use of various motors and pumps, but ultimately all such devices derive their power from the engine. Another way of looking at it is that a motor receives power from an external source, and then converts it into mechanical energy, while an engine creates power from pressure (derived directly from the explosive force of combustion or other [[chemical]] reaction, or secondarily from the action of some such force on other substances such as air, water, or steam).<ref>{{cite book|last=Press|first=AIP, Associated|title=Stylebook and Briefing on Media Law|year=2007|publisher=Basic Books|location=New York|isbn=978-0-465-00489-8|pages=84|edition=42nd ed}}</ref> Devices converting heat energy into motion are commonly referred to simply as ''engines''.<ref>Collins English Dictionary -Retrieved September 03, 2012 from CollinsDictionary.com website:http://www.collinsdictionary.com/dictionary/english/Engine </ref> ==History== ===Antiquity=== [[Simple machine]]s, such as the [[mace (club)|club]] and [[oar]] (examples of the [[lever]]), are [[Prehistory|prehistoric]]. More complex engines using [[Manual labour|human power]], [[Working animals|animal power]], [[Water wheel|water power]], [[Windmill|wind power]] and even steam power date back to antiquity. Human power was focused by the use of simple engines, such as the [[Capstan (nautical)|capstan]], [[windlass] or e2e2e2r432fcgvgzszsdzsdttfy[[Treadwheel|treadmill]], and with [[rope]]s, [[pulley]]s, and [[block and tackle]] arrangements; this power was transmitted usually with the forces [[mechanical advantage|multiplied]] and the speed [[gear reduction|reduced]]. These were used in [[Crane (machine)|cranes]] and aboard [[ship]]s in [[Ancient Greece]], as well as in [[Mining|mine]]s, [[Pump|water pump]]s and [[siege engines]] in [[Ancient Rome]]. The writers of those times, including [[Vitruvius]], [[Frontinus]] and [[Pliny the Elder]], treat these engines as commonplace, so their invention may be more ancient. By the 1st century AD, [[cattle]] and [[horse]]s were used in [[Mill (grinding)|mill]]s, driving machines similar to those powered by humans in earlier times. According to [[Strabo]], a water powered mill was built in Kaberia of the [[Parthian Empire|kingdom of Mithridates]] during the 1st century BC. Use of [[water wheel]]s in mills spread throughout the [[Roman Empire]] over the next few centuries. Some were quite complex, with [[aqueduct (bridge)|aqueduct]]s, [[dam]]s, and [[sluice]]s to maintain and channel the water, along with systems of [[gears]], or toothed-wheels made of wood and metal to regulate the speed of rotation. More sophisticated small devices, such as the [[Antikythera Mechanism]] used complex trains of gears and dials to act as calendars or predict astronomical events. In a poem by [[Ausonius]] in the 4th century AD, he mentions a stone-cutting saw powered by water. [[Hero of Alexandria]] is credited with many such [[wind]] and [[steam]] powered machines in the 1st century AD, including the [[Aeolipile]] and the [[vending machine]], often these machines were associated with worship, such as animated altars and automated temple doors. ===Medieval=== Medieval Muslim engineers employed [[gear]]s in mills and water-raising machines, and used [[dam]]s as a source of water power to provide additional power to watermills and water-raising machines.<ref name=Hassan>[[Ahmad Y Hassan]], [http://www.history-science-technology.com/Articles/articles%2071.htm Transfer Of Islamic Technology To The West, Part II: Transmission Of Islamic Engineering]</ref> In the [[Islamic Golden Age|medieval Islamic world]], such advances made it possible to [[Mechanization|mechanize]] many industrial tasks previously carried out by [[manual labour]]. In 1206, [[al-Jazari]] employed a [[Crank (mechanism)|crank]]-[[conrod]] system for two of his water-raising machines. A rudimentary [[steam turbine]] device was described by [[Taqi al-Din Muhammad ibn Ma'ruf|Taqi al-Din]]<ref name=Hassan>[[Ahmad Y Hassan]] (1976). ''Taqi al-Din and Arabic Mechanical Engineering'', p. 34-35. Institute for the History of Arabic Science, [[University of Aleppo]].</ref> in 1551 and by [[Giovanni Branca]]<ref name= Giovanni>{{cite web|url=http://www.history.rochester.edu/steam/thurston/1878/Chapter1.html|title= University of Rochester, NY, '&#39;The growth of the steam engine'&#39; online history resource, chapter one|publisher=History.rochester.edu |date= |accessdate=2010-02-03}}</ref> in 1629.<ref>"''[http://books.google.com/books?id=Cv9LH4ckuEwC&pg=PA432&dq&hl=en#v=onepage&q=&f=false Power plant engineering]''". P. K. Nag (2002). [[Tata McGraw-Hill]]. p.432. ISBN 0-07-043599-5</ref> In the 13th century, the solid [[rocket motor]] was invented in China. Driven by gunpowder, this, the simplest form of internal combustion engine was unable to deliver sustained power, but was useful for propelling weaponry at high speeds towards enemies in battle and for [[fireworks]]. After invention, this innovation spread throughout Europe. ===Industrial Revolution=== [[Image:Boulton and Watt centrifugal governor-MJ.jpg|thumb|upright|Boulton & Watt engine of 1788]] The Watt steam engine was the first type of steam engine to make use of steam at a pressure just above [[atmospheric pressure|atmospheric]] to drive the piston helped by a partial vacuum. Improving on the design of the 1712 [[Newcomen steam engine]], the Watt steam engine, developed sporadically from 1763 to 1775, was a great step in the development of the steam engine. Offering a dramatic increase in [[fuel efficiency]], [[James Watt]]'s design became synonymous with steam engines, due in no small part to his business partner, [[Matthew Boulton]]. It enabled rapid development of efficient semi-automated factories on a previously unimaginable scale in places where waterpower was not available. Later development led to [[steam locomotive]]s and great expansion of [[Rail transport|railway transportation]]. As for internal combustion piston engines, these were tested in France in 1807 by [[de Rivaz]] and independently, by the [[Nicéphore Niépce|Niépce brothers]] . They were theoretically advanced by [[Nicolas Léonard Sadi Carnot|Carnot]] in 1824.{{citation needed|date=May 2011}} In 1853-57 [[Eugenio Barsanti]] and [[Felice Matteucci]] invented and patented an engine using the free-piston principle that was possibly the first 4-cycle engine.<ref>{{cite web|title=La documentazione essenziale per l'attribuzione della scoperta|url=http://www.barsantiematteucci.it/inglese/documentiStorici.html|quote= A later request was presented to the Patent Office of the Reign of Piedmont, under No. 700 of Volume VII of that Office. The text of this patent request is not available, only a photo of the table containing a drawing of the engine. This may have been either a new patent or an extension of a patent granted three days earlier, on 30 December 1857, at Turin.}}</ref> The [[Otto cycle]] in 1877 was capable of giving a far higher [[power to weight ratio]] than steam engines and worked much better for many transportation applications such as cars and aircraft. ===Automobiles=== The first commercially successful automobile, created by [[Karl Benz]], added to the interest in light and powerful engines. The lightweight petrol internal combustion engine, operating on a four-stroke Otto cycle, has been the most successful for light automobiles, while the more efficient [[Diesel engine]] is used for trucks and buses. However, in recent years, turbo Diesel engines have become increasingly popular, especially outside of the United States, even for quite small cars. ====Horizontally opposed pistons==== In 1896, Karl Benz was granted a patent for his design of the first engine with horizontally opposed pistons. His design created an engine in which the corresponding pistons move in horizontal cylinders and reach top dead center simultaneously, thus automatically balancing each other with respect to their individual momentum. Engines of this design are often referred to as flat engines because of their shape and lower profile. They are or were used in: the [[Volkswagen Beetle]], some Porsche and Subaru cars, many [[BMW]] and [[Honda]] [[motorcycle]]s, and [[aircraft engine]]s (for propeller driven aircraft), etc. ====Advancement==== Continuance of the use of the internal combustion engine for automobiles is partly due to the improvement of engine control systems (onboard computers providing engine management processes, and electronically controlled fuel injection). Forced air induction by turbocharging and supercharging have increased power outputs and engine efficiencies. Similar changes have been applied to smaller diesel engines giving them almost the same power characteristics as petrol engines. This is especially evident with the popularity of smaller diesel engine propelled cars in Europe. Larger diesel engines are still often used in trucks and heavy machinery, although they require special machining not available in most factories. Diesel engines produce lower [[hydrocarbon]] and [[CO2]] emissions, but greater [[Atmospheric particulate matter|particulate]] and [[NOx]] pollution, than gasoline engines.<ref name=Harrison2001>{{Citation |url= http://books.google.com/books?id=1kFbRYQUqcAC&pg=PA332#v=onepage&q&f=false |accessdate= February 20, 2012 |title= Pollution: Causes, Effects and Control |first= Roy M. |last= Harrison |edition=4th |publisher= [[Royal Society of Chemistry]] |year= 2001 |ISBN= 9780854046218 }}</ref> Diesel engines are also 40% more fuel efficient than comparable gasoline engines.<ref name=Harrison2001/> ====Increasing power==== The first half of the 20th century saw a trend to increasing engine power, particularly in the American models{{Clarify|reason=As opposed to what models?|date=June 2012}}. Design changes incorporated all known methods of raising engine capacity, including increasing the pressure in the cylinders to improve efficiency, increasing the size of the engine, and increasing the rate at which the engine produces work. The higher forces and pressures created by these changes created engine vibration and size problems that led to stiffer, more compact engines with V and opposed cylinder layouts replacing longer straight-line arrangements. ====Combustion efficiency==== The design principles favoured in Europe, because of economic and other restraints such as smaller and twistier roads, leant toward smaller cars and corresponding to the design principles that concentrated on increasing the combustion efficiency of smaller engines. This produced more economical engines with earlier four-cylinder designs rated at 40 horsepower (30&nbsp;kW) and six-cylinder designs rated as low as 80 horsepower (60&nbsp;kW), compared with the large volume V-8 American engines with power ratings in the range from 250 to 350&nbsp;hp, some even over 400&nbsp;hp (190 to 260&nbsp;kW).{{Clarify|reason=What time period is this paragraph about?|date=June 2012}}{{Citation needed|date=February 2010}} ====Engine configuration==== Earlier automobile engine development produced a much larger range of engines than is in common use today. Engines have ranged from 1- to 16-cylinder designs with corresponding differences in overall size, weight, [[engine displacement]], and cylinder [[Bore (engine)|bores]]. Four cylinders and power ratings from 19 to 120&nbsp;hp (14 to 90&nbsp;kW) were followed in a majority of the models. Several three-cylinder, two-stroke-cycle models were built while most engines had straight or in-line cylinders. There were several V-type models and horizontally opposed two- and four-cylinder makes too. Overhead [[camshaft]]s were frequently employed. The smaller engines were commonly air-cooled and located at the rear of the vehicle; compression ratios were relatively low. The 1970s and 1980s saw an increased interest in improved [[Fuel economy in automobiles|fuel economy]], which caused a return to smaller V-6 and four-cylinder layouts, with as many as five valves per cylinder to improve efficiency. The [[Bugatti Veyron]] 16.4 operates with a [[W16 engine]], meaning that two [[V8 engine|V8]] cylinder layouts are positioned next to each other to create the W&nbsp;shape sharing the same crankshaft. The largest internal combustion engine ever built is the [[Wärtsilä-Sulzer RTA96-C]], a 14-cylinder, 2-stroke turbocharged diesel engine that was designed to power the ''[[Emma Mærsk]]'', the largest container ship in the world. This engine weighs 2,300 tons, and when running at 102&nbsp;RPM produces 109,000&nbsp;bhp (80,080&nbsp;kW) consuming some 13.7 tons of fuel each hour. ==Heat engine== {{Main|heat engine}} ===Combustion engine=== Combustion engines are [[heat engine]]s driven by the heat of a [[combustion]] process. ====Internal combustion engine==== {{Main|Internal combustion engine}} [[File:4StrokeEngine Ortho 3D Small.gif|thumb|right|225px|Animation showing the four stages of the [[Four-stroke engine|four-stroke]] combustion engine cycle:<br />1. Induction ''(Fuel enters)''<br />2. Compression<br />3. Ignition ''(Fuel is burnt)''<br />4. Emission ''(Exhaust out)'']] The '''internal combustion engine''' is an engine in which the [[combustion]] of a fuel (generally, [[fossil fuel]]) occurs with an oxidizer (usually air) in a [[combustion chamber]]. In an internal combustion engine the expansion of the high [[temperature]] and high [[pressure]] gases, which are produced by the combustion, directly applies [[force]] to components of the engine, such as the [[piston]]s or [[turbine blade]]s or a [[propulsive nozzle|nozzle]], and by moving it over a distance, generates useful mechanical [[energy]].<ref name=r1 >{{cite web|first=Charles Lafayette |last=Proctor II |url=http://www.britannica.com/EBchecked/topic/290504/internal-combustion-engine |title=Internal Combustion engines |publisher=Encyclopædia Britannica Online |date= |accessdate=2011-05-09}}</ref><ref name=r2 >{{cite web|url=http://www.answers.com/topic/internal-combustion-engine?cat=technology |title=Internal combustion engine |publisher=Answers.com |date= |accessdate=2011-05-09}}</ref><ref name=r3 >{{cite web|url=http://inventors.about.com/gi/dynamic/offsite.htm?site=http://www.bartleby.com/65/in/intern-co.html |title=Columbia encyclopedia: Internal combustion engine |publisher=Inventors.about.com |date= |accessdate=2011-05-09}}</ref><ref name=r4 >{{cite web|url=http://www.infoplease.com/ce6/sci/A0825332.html |title=Internal-combustion engine |publisher=Infoplease.com |year=2007 |accessdate=2011-05-09}}</ref> ====External combustion engine==== {{Main|external combustion engine}} An '''external combustion engine''' (EC engine) is a [[heat engine]] where an internal working [[fluid]] is heated by combustion of an external source, through the engine wall or a [[heat exchanger]]. The [[fluid]] then, by expanding and acting on the [[Mechanism (engineering)|mechanism]] of the engine produces motion and usable [[Mechanical work|work]].<ref>{{cite web|url=http://www.merriam-webster.com/dictionary/external%20combustion |title=External combustion |publisher=Merriam-Webster Online Dictionary |date=2010-08-13 |accessdate=2011-05-09}}</ref> The fluid is then cooled, compressed and reused (closed cycle), or (less commonly) dumped, and cool fluid pulled in (open cycle air engine). "[[Combustion]]" refers to [[burning]] fuel with an [[oxidizer]], to supply the heat. Engines of similar (or even identical) configuration and operation may use a supply of heat from other sources such as nuclear, solar, geothermal or exothermic reactions not involving combustion; but are not then strictly classed as external combustion engines, but as external thermal engines. The working fluid can be a gas as in a [[Stirling engine]], or [[steam]] as in a steam engine or an organic liquid such as n-pentane in an [[Organic Rankine cycle]]. The fluid can be of any composition; gas is by far the most common, although even single-phase [[liquid]] is sometimes used. In the case of the steam engine, the fluid changes [[Phase (matter)|phase]]s between liquid and gas. ====Air-breathing combustion engines==== '''Air-breathing combustion engines''' are combustion engines that use the [[oxygen]] in atmospheric air to [[oxidise]] ('burn') the fuel, rather than carrying an [[oxidiser]], as in a [[rocket]]. Theoretically, this should result in a better [[specific impulse]] than for rocket engines. A continuous stream of air flows through the [[air-breathing engine]]. This air is compressed, mixed with fuel, ignited and expelled as the exhaust gas. ;Examples Typical air-breathing engines include: *[[Reciprocating engine]] *[[Steam engine]] *[[Gas turbine]] :[[airbreathing jet engine]] :[[Turboprop|Turbo-propeller engine]] *[[Pulse detonation engine]] *[[Pulse jet]] *[[Ramjet]] *[[Scramjet]] *[[Liquid air cycle engine]]/[[Reaction Engines SABRE]]. ====Environmental effects==== The operation of engines typically has a negative impact upon [[air quality]] and ambient [[noise pollution|sound levels]]. There has been a growing emphasis on the pollution producing features of automotive power systems. This has created new interest in alternate power sources and internal-combustion engine refinements. Though a few limited-production battery-powered electric vehicles have appeared, they have not proved competitive owing to costs and operating characteristics.{{Citation needed|date=November 2012}} In the 21st century the diesel engine has been increasing in popularity with automobile owners. However, the gasoline engine and the Diesel engine, with their new emission-control devices to improve emission performance, have not yet been significantly challenged.{{Citation needed|date=November 2012}} A number of manufacturers have introduced hybrid engines, mainly involving a small gasoline engine coupled with an electric motor and with a large battery bank, but these too have yet to make much of an inroad into the market shares of gasoline and Diesel engines. ====Air quality==== Exhaust from a spark ignition engine consists of the following: [[nitrogen]] 70 to 75% (by volume), [[water vapor]] 10 to 12%, [[carbon dioxide]] 10 to 13.5%, [[hydrogen]] 0.5 to 2%, [[oxygen]] 0.2 to 2%, [[carbon monoxide]]: 0.1 to 6%, unburnt [[hydrocarbons]] and partial [[oxidation]] products (e.g. [[aldehydes]]) 0.5 to 1%, [[nitrogen monoxide]] 0.01 to 0.4%, [[nitrous oxide]] <100 ppm, [[sulfur dioxide]] 15 to 60 ppm, traces of other compounds such as fuel additives and lubricants, also halogen and metallic compounds, and other particles.<ref>Paul Degobert, Society of Automotive Engineers (1995), ''Automobiles and Pollution''</ref> Carbon monoxide is highly toxic, and can cause [[carbon monoxide poisoning]], so it is important to avoid any build-up of the gas in a confined space. [[Catalytic converter]]s can reduce toxic emissions, but not completely eliminate them. Also, resulting greenhouse gas emissions, chiefly [[carbon dioxide]], from the widespread use of engines in the modern industrialized world is contributing to the global [[greenhouse effect]] – a primary concern regarding [[global warming]]. ===Noncombustive heat engines=== {{Main|heat engine}} Some engines convert heat from noncombustive processes into mechanical work, for example a nuclear power plant uses the heat from the nuclear reaction to produce steam and drive a steam engine, or a gas turbine in a rocket engine may be driven by decomposing [[hydrogen peroxide]]. Apart from the different energy source, the engine is often engineered much the same as an internal or external combustion engine. Another group of noncombustive engines includes [[thermoacoustic heat engine]]s (sometimes called "TA engines") which are thermoacoustic devices which use high-amplitude sound waves to pump heat from one place to another, or conversely use a heat difference to induce high-amplitude sound waves. In general, thermoacoustic engines can be divided into standing wave and travelling wave devices.<ref>{{cite book |url=http://www.scribd.com/doc/147785416/Experimental-Investigations-on-a-Standing-Wave-Thermoacoustic-Engine#fullscreen |first=Mahmoud |last=Emam |title=Experimental Investigations on a Standing-Wave Thermoacoustic Engine, M.Sc. Thesis, |publisher=Cairo University |location=Egypt |year=2013 |accessdate=2013-09-26}}</ref> ==Nonthermal chemically powered motor== Nonthermal motors usually are powered by a chemical reaction, but are not heat engines. Examples include: *[[Molecular motor]] - motors found in living things *[[Synthetic molecular motor]]. ==Electric motor== {{Main|electric motor|electric vehicle}} An '''electric motor''' uses [[electrical energy]] to produce [[mechanical energy]], usually through the interaction of [[magnetic fields]] and [[electrical conductor|current-carrying conductors]]. The reverse process, producing electrical energy from mechanical energy, is accomplished by a [[Electrical generator|generator]] or [[dynamo]]. [[Traction motor]]s used on vehicles often perform both tasks. Electric motors can be run as generators and vice versa, although this is not always practical. Electric motors are ubiquitous, being found in applications as diverse as industrial fans, blowers and pumps, machine tools, household appliances, [[power tools]], and [[hard drive|disk drives]]. They may be powered by direct current (for example a [[battery (electric)|battery]] powered portable device or motor vehicle), or by [[alternating current]] from a central electrical distribution grid. The smallest motors may be found in electric wristwatches. Medium-size motors of highly standardized dimensions and characteristics provide convenient mechanical power for industrial uses. The very largest electric motors are used for propulsion of large ships, and for such purposes as pipeline compressors, with ratings in the thousands of [[watt (unit)|kilowatt]]s. Electric motors may be classified by the source of electric power, by their internal construction, and by their application. The physical principle of production of mechanical force by the interactions of an electric current and a magnetic field was known as early as 1821. Electric motors of increasing efficiency were constructed throughout the 19th century, but commercial exploitation of electric motors on a large scale required efficient electrical generators and electrical distribution networks. To reduce the electric [[energy consumption]] from motors and their associated [[carbon footprint]]s, various regulatory authorities in many countries have introduced and implemented legislation to encourage the manufacture and use of higher efficiency electric motors. A well-designed motor can convert over 90% of its input energy into useful power for decades.<ref>"Motors". American Council for an Energy-Efficient Economy. http://www.aceee.org/topics/motors</ref> When the efficiency of a motor is raised by even a few percentage points, the savings, in [[kilowatt hour]]s (and therefore in cost), are enormous. The electrical energy efficiency of a typical industrial [[induction motor]] can be improved by: 1) reducing the electrical losses in the [[stator]] windings (e.g., by increasing the cross-sectional area of the [[Electrical conductor|conductor]], improving the [[Inductor|winding]] technique, and using materials with higher [[Electrical conductivity|electrical conductivities]], such as [[Copper in energy efficient motors|copper]]), 2) reducing the electrical losses in the [[Rotor (electric)|rotor]] coil or casting (e.g., by using materials with higher electrical conductivities, such as [[Copper in energy efficient motors|copper]]), 3) reducing magnetic losses by using better quality magnetic [[steel]], 4) improving the [[aerodynamic]]s of motors to reduce mechanical windage losses, 5) improving [[Bearing (mechanical)|bearings]] to reduce [[friction loss]]es, and 6) minimizing manufacturing [[Engineering tolerance|tolerances]]. ''For further discussion on this subject, see [[Premium efficiency]] and [[Copper in energy efficient motors]].)'' By convention, ''electric engine'' refers to a railroad [[electric locomotive]], rather than an electric motor. ==Physically powered motor== Some motors are powered by potential or kinetic energy, for example some [[funicular]]s, [[gravity plane]] and [[ropeway conveyor]]s have used the energy from moving water or rocks, and some clocks have a weight that falls under gravity. Other forms of potential energy include compressed gases (such as [[pneumatic motor]]s), springs ([[clockwork motor]]s) and [[Elastic band#Model use|elastic band]]s. Historic [[military]] [[siege engines]] included large [[catapult]]s, [[trebuchet]]s, and (to some extent) [[battering ram]]s were powered by potential energy. ===Pneumatic motor=== {{main|Pneumatic motor}} A '''pneumatic motor''' is a machine that converts potential energy in the form of [[compressed air]] into [[mechanical work]]. Pneumatic motors generally convert the compressed air to mechanical work though either linear or rotary motion. Linear motion can come from either a diaphragm or piston actuator, while rotary motion is supplied by either a vane type air motor or piston air motor. Pneumatic motors have found widespread success in the hand-held tool industry and continual attempts are being made to expand their use to the transportation industry. However, pneumatic motors must overcome efficiency deficiencies before being seen as a viable option in the transportation industry. ===Hydraulic motor=== {{main|Hydraulic motor }} A '''hydraulic motor''' is one that derives its power from a [[pressure|pressurized]] [[fluid]]. This type of engine can be used to move heavy loads or produce motion.<ref>{{cite web |url=http://reference.howstuffworks.com/hydraulic-engine-encyclopedia.htm |title=Howstuffworks "Engineering" |publisher=Reference.howstuffworks.com |date=2006-01-29 |accessdate=2011-05-09 }}</ref> ==Sound levels== In the case of sound levels, engine operation is of greatest impact with respect to mobile sources such as automobiles and trucks. Engine noise is a particularly large component of mobile source noise for vehicles operating at lower speeds, where aerodynamic and tire noise is less significant.<ref>{{cite journal|url=http://www.springerlink.com/content/x1707075n815g604/ |first=C. Michael |last=Hogan |title=Analysis of Highway Noise |journal=Journal of Water, Air, and Soil Pollution |volume=2 |issue=3 |pages=387–392 |date=September 1973 |publisher=Springer Verlag |issn=0049-6979 |accessdate=2011-05-09}}</ref> Petrol and diesel engines are fitted with [[muffler]]s (silencers) to reduce noise. ==Efficiency== {{Main|Engine efficiency}} Depending on the type of engine employed, different rates of efficiency are attained. ==Engines by use== Particularly notable kinds of engines include: *[[Aircraft engine]] *[[Automobile engine]] *[[Model engine]] *[[Motorcycle engine]] *[[Marine propulsion]] engines such as [[Outboard motor]] *[[Non-road engine]] is the term used to define engines that are not used by vehicles on roadways. *[[Railway locomotive]] engine *[[Spacecraft propulsion]] engines such as [[Rocket engine]] *[[Traction engine]] ==Engine speed== Engine speed is measured in [[revolutions per minute]] (RPM). Engines may be classified as low-speed, medium-speed or high-speed but these terms are inexact and depend on the type of engine being described. Generally, Diesel engines operate at lower speed compared to gasoline engines. ==See also== *[[Timeline of motor and engine technology]] *[[Timeline of heat engine technology]] *[[Electric motor]] *[[Engine cooling]] *[[Multifuel]] *[[Gasoline engine]] *[[Hesselman engine]] *[[HCCI|HCCI engine]] *[[Hot bulb engine]] *[[IRIS engine]] *[[Solid-state engine]] ==Notes== {{Reflist|30em}} ==References== {{Refbegin}} * J. G. Landels, ''Engineering in the Ancient World'', ISBN 0-520-04127-5 {{Refend}} ==External links== {{Commons category|Engines}} {{Wiktionary|engine}} {{Wiktionary|motor}} *{{US patent|194047}} *[http://www.animatedpiston.com Detailed Engine Animations] *[http://www.liveleak.com/view?i=73e_1192001762 Video from inside a four-stroke engine cylinder]. *[http://www.gbm.dk/gbm/Motor-e.htm Working 4-Stroke Engine - Animation] *[http://www.animatedengines.com Animated illustrations of various engines] * [http://www.popularmechanics.com/cars/news/industry/5-alternative-engine-architectures?click=main_sr 5 Ways to Redesign the Internal Combustion Engine] {{Heat engines|state=uncollapsed}} {{Thermodynamic cycles}} [[Category:Engine technology| ]] [[Category:Engines| ]]'