Editing Internal combustion engine

The '''internal combustion engine''' is a [[heat engine]] in which [[combustion]] occurs in a confined space called a combustion chamber. Combustion of a [[fuel]] creates high [[temperature]]/[[pressure]] gases, which are permitted to expand. The expanding gases are used to directly move a piston, turbine blades, rotor(s), or the [[engine]] itself thus doing useful work.

==Characterstics==
Internal combustion engines can be powered by any [[fuel]] that can be combined with an "[[oxidizer]]" in the chamber.

By way of contrast, an [[external combustion engine]] such as a [[steam engine]] does work when the combustion process heats a separate working fluid, such as water or steam, which then in turn does work.

[[Jet engine]]s, most [[rocket]]s and many [[gas turbine]]s are strictly classed as internal combustion engines, but the term ''internal combustion engine'' is also used to refer specifically to [[reciprocating engine]]s, [[Wankel engine]]s and similar designs in which combustion is intermittent. Today, i

, ''internal combustion engine'' is abbreviated to the acronym [[ICE]].
[[Image:4-Stroke-Engine.gif|framed|right|[[Four-stroke cycle]] (or Otto cycle)]]

== History ==

=== Non-compression ===
Leonardo da Vinci [http://en.wikipedia.org/wiki/Leonardo_da_Vinci] , in 1509, and Christiaan Huygens [http://en.wikipedia.org/wiki/Christiaan_Huygens], in 1673, described constant pressure engines. (Leonardo's description may not imply that the idea was original with him or that it was actually constructed.)

The internal combustion indirect or suction principle may not meet the deffinition of an engine, becuase the process does not repeat.

Early internal-combustion engines were used to power farm equipment.

English inventor Sir Samuel Morland [http://en.wikipedia.org/wiki/Samuel_Morland] used gunpowder [http://en.wikipedia.org/wiki/Gunpowder] to drive water pumps in the 17th century. In 1794, [[Robert Street]] built a compression-less engine whose principle of operation would dominate for nearly a century.

The first internal combustion engine to be Applied industrially was patented by Samual Brown in 1823. It was based on what Hardenberg calls the "Leonardo cycle", which, as this name implies, was already out of date at that time. Just as today, early major funding, in an area where standards had not yet been established, went to the best showmen sooner than to the best workers.
The Italians Eugenio Barsanti [http://en.wikipedia.org/wiki/Eugenio_Barsanti] and Felice Matteucci [http://en.wikipedia.org/wiki/Felice_Matteucci] patented the first working, efficient internal combustion engine in 1854 in London (pt. Num. 1072) but did not get into production with it. It was similar in concept to the successful Otto Langen indirect engine, but not so well worked out in detail.

In 1860, Etienne Lenoir [http://en.wikipedia.org/wiki/Etienne_Lenoir] (1822 - 1900) produced a gas-fired internal combustion engine not dissimilar in appearance to a [[steam]] [[beam engine]]. This closely resembled a horizontal double acting steam engine, with cylinders, pistons, connecting-rods and fly wheel in which the gas essentially took the place of the steam. This was the first internal combustion engine to be produced in numbers.
The American Samuel Morey [http://en.wikipedia.org/wiki/Samuel_Morey] received a patent on April 1, 1826 for a "Gas Or [[Vapor Engine]]".

His first (1862) engine with compression having shocked itself apart, Nikolaus Otto [http://en.wikipedia.org/wiki/Nikolaus_Otto] designed an indirect acting free piston compression-less engine whose greater efficiency won the support of Langen and then most of the market, which at that time, was mostly for small stationary engines fueled by lighting gas. In 1870 in Vienna Siegfried Marcus [http://en.wikipedia.org/wiki/Siegfried_Marcus] put the first mobile gasoline engine on a handcart.

=== Compression ===
The most significant distinction between modern internal combustion engines and the early designs is the use of compression and in particular of in-cylinder compression. The [[thermodynamic]] theory of idealized heat engines was established by Nicolas Léonard Sadi Carnot [http://en.wikipedia.org/wiki/Nicolas_L%C3%A9onard_Sadi_Carnot] in France in 1824. This scientifically established the need for compression to increase the difference between the upper and lower working temperatures, but it is not clear that engine designers were aware of this before compression was already commonly used. In fact it may have mislead designers who attempted to emulate the Carnot cycle in ways that were not useful.

The first recorded suggestion of in-cylinder compression was a patent granted to William Barnet (English) in 1838. He apparently did not realize its advantages, but his cycle would have been a great advance if sufficiently developed.

Otto working with Gottlieb Daimler [http://en.wikipedia.org/wiki/Gottlieb_Daimler] and Wilhelm Maybach [http://en.wikipedia.org/wiki/Wilhelm_Maybach] in the 1870s developed a practical [[four-stroke cycle]] (Otto cycle) engine. The German courts, however, did not hold his patent to cover all in-cylinder compression engines or even the four stroke cycle, and after this decision in-cylinder compression became universal.

==Applications==

Internal combustion engines are most commonly used for mobile propulsion systems. In mobile scenarios internal combustion is advantageous, since it can provide high power to weight ratios together with excellent fuel energy-density. These engines have appeared in almost all [[Automobile|cars]], [[motorbike]]s, many [[boat]]s, and in a wide variety of [[aircraft]] and [[locomotive]]s. Where very high power is required, such as [[jet aircraft]], [[helicopter]]s and large ships, they appear mostly in the form of [[gas turbines]]. They are also used for [[electric generator]]s and by industry.

For low power mobile and many non-mobile applications an [[electric motor]] is a competitive alternative. In the future, electric motors may also become competitive for most mobile applications. However, the high cost, weight, and poor energy density of [[Lead-acid battery|PbA]] and even [[Nickel metal hydride battery|NiMH]] [[battery (electricity)|batteries]] and lack of affordable on board electric generators such as [[fuel cell]]s has largely restricted their use to specialist applications. However recent battery advancements in lightweight [[Lithium ion battery|Li-ion]] and [[Lithium ion polymer battery|Li-poly]] chemistries are bringing safety, power density, lifespan, and cost to within acceptable or even desirable levels. For example recently [[battery electric vehicle]]s began to demonstrated 300 miles of range on Lithium, now improved power makes them appealing for [[plug-in hybrid electric vehicle]]s whose electric range is less critical having internal combustion for ''unlimited'' range.

==Operation==
All '''internal combustion engines''' depend on the [[exothermic]] chemical process of [[combustion]]: the reaction of a [[fuel]], typically with air, although other oxidisers such as [[nitrous oxide]] may be employed. Also see stoichiometry [http://en.wikipedia.org/wiki/Stoichiometry] .

The most common fuels in use today are made up of [[hydrocarbon]]s and are derived from [[petroleum]]. These include the fuels known as [[diesel]], [[gasoline]] and [[liquified petroleum gas]]. Most internal combustion engines designed for gasoline can run on [[natural gas]] or liquified petroleum gases without modifications except for the fuel delivery components. Liquid and gaseous [[biofuel]]s of adequate formulation can also be used.

Some have theorized that in the future [[hydrogen]] might [[Hydrogen economy|replace such fuels]]. Furthermore, with the introduction of hydrogen [[fuel cell]] technology, the use of internal combustion engines may be phased out. The advantage of hydrogen is that its combustion produces only [[water]]. This is unlike the combustion of hydrocarbons, which also produces [[carbon dioxide]], a major cause of [[global warming]], as well as [[carbon monoxide]], resulting from incomplete combustion. The big disadvantage of hydrogen in many situations is [[Hydrogen economy#Storage|its storage]]. Liquid hydrogen has extremely low density- 14 times lower than water and requires extensive insulation, whilst gaseous hydrogen requires very heavy tankage. While hydrogen is light and therefore has a higher specific energy, the volumetric efficiency is still roughly five times lower than petrol. This is why hydrogen must be compressed if there is to be a useful amount of stored energy.

All internal combustion engines must have a means of [[ignition system|ignition]] to promote combustion. Most engines use either an [[spark plug|electrical]] or a [[compression heating ignition]] system. Electrical ignition systems generally rely on a [[lead-acid battery]] and an [[induction coil]] to provide a high voltage electrical spark to ignite the air-fuel mix in the engine's cylinders. This battery can be recharged during operation using an ''[[alternator]]'' driven by the engine. Compression heating ignition systems ([[Diesel engine]]s and [[HCCI]] engines) rely on the heat created in the air by compression in the engine's cylinders to ignite the fuel.

Once successfully ignited and burnt, the combustion products (hot [[gas]]es) have more available energy than the original compressed fuel/air mixture (which had higher [[chemical energy]]). The available energy is manifested as high [[temperature]] and [[pressure]] which can be translated into [[work]] by the engine. In a reciprocating engine, the high pressure product gases inside the cylinders drive the engine's pistons.

Once the available energy has been removed the remaining hot gases are vented (often by opening a [[poppet valve|valve]] or exposing the exhaust outlet) and this allows the piston to return to its previous position (Top Dead Center - TDC). The piston can then proceed to the next phase of its cycle (which varies between engines). Any [[heat]] not translated into work is a waste product and is removed from the engine either by an air or liquid cooling system.

==Parts==
[[Image:180px-Four_stroke_cycle_compression.jpg|thumb|An illustration of several key components in a typical [[four-stroke cycle|four-stroke]] engine]]

The parts of an engine vary depending on the engine's type. For a [[four-stroke cycle|four-stroke]] engine, key parts of the engine include the [[crankshaft]] (purple), one or more [[camshaft]]s (red and blue) and [[poppet valve|valves]]. For a [[two-stroke cycle|two-stroke]] engine, there may simply be an exhaust outlet and fuel inlet instead of a valve system. In both types of engines, there are one or more cylinders (grey and green) and for each cylinder there is a [[spark plug]] (darker-grey), a [[piston]] (yellow) and a [[crank (mechanism)|crank]] (purple). A single sweep of the cylinder by the piston in an upward or downward motion is known as a stroke and the downward stroke that occurs directly after the air-fuel mix in the cylinder is ignited is known as a power stroke.

A [[Wankel engine]] has a triangular rotor that orbits in an [[epitroichoid]]al (figure 8 shape) chamber around an eccentric shaft. The four phases of operation (intake, compression, power, exhaust) take place in separate locations, instead of one single location as in a reciprocating engine.

A [[Bourke Engine]] uses a pair of pistons integrated to a [[Scotch Yoke]] that transmits reciprocating force through a specially designed bearing assembly to turn a crank mechanism. Intake, compression, power, and exhaust all occur in each stroke of this yoke.

==Classification==
There is a wide range of internal combustion engines corresponding to their many varied applications. Likewise there is a wide range of ways to classify internal-combustion engines, some of which are listed below.

Although the terms sometimes cause confusion, there is no real difference between an "engine" and a "motor." At one time, the word "engine" (from Latin [http://en.wikipedia.org/wiki/Latin] , via Old French [http://en.wikipedia.org/wiki/Old_French] , ''ingenium'', "ability") meant any piece of [[machinery]]. A "motor" (from Latin ''motor'', "mover") is any machine that produces mechanical [[Power (physics)|power]]. Traditionally, [[electric motor]]s are not referred to as "engines," but combusion engines are often referred to as "motors."

===Principles of operation===

[[Reciprocating engine|Reciprocating]]:
* [[two-stroke cycle|Two-stroke engine]]
* [[four-stroke cycle|Four-stroke engine]]
* [[Sleeve valve|Sleeve valve four-stroke]]
* [[Bourke Engine]]

[[Pistonless rotary engine|Rotary]]:

*Demonstrated:
** Wankel engine [http://en.wikipedia.org/wiki/Wankel_engine]
*Proposed:
** orbital engine [http://en.wikipedia.org/wiki/Orbital_engine]
** quasiturbine [http://en.wikipedia.org/wiki/Quasiturbine]

Continuous combustion:
* [[gas turbine]]
* [[jet engine]]
* [[rocket engine]]

===Engine cycle===
Engines based on the [[two-stroke cycle]] use two strokes (one up, one down) for every power stroke. Since there are no dedicated intake or exhaust strokes, alternative methods must be used to [[scavenge]] the cylinders. The most common method in spark-ignition two-strokes is to use the downward motion of the piston to pressurize fresh [[charge]] in the [[crankcase]], which is then blown through the cylinder through ports in the cylinder walls. Spark-ignition two-strokes are small and light (for their power output), and mechanically very simple. Common applications include [[snowmobile]]s, [[lawnmower]]s, [[chain saw]]s, [[jet ski]]s, [[moped]]s, [[outboard motor]]s and some [[motorcycle]]s. Unfortunately, they are also generally louder, less efficient, and far more polluting than their four-stroke counterparts, and they do not scale well to larger sizes. Interestingly, the largest compression-ignition engines are two-strokes, and are used in some locomotives and large ships. These engines use [[forced induction]] to scavenge the cylinders.

Engines based on the [[four-stroke cycle]] or Otto cycle have one power stroke for every four strokes (up-down-up-down) and are used in cars, larger [[boat]]s and many light [[aircraft]]. They are generally quieter, more efficient and larger than their two-stroke counterparts. There are a number of variations of these cycles, most notably the [[Atkinson cycle|Atkinson]] and [[Miller cycle|Miller]] cycles. Most truck and automotive Diesel engines use a four-stroke cycle, but with a compression heating ignition system it is possible to talk separately about a [[diesel cycle]]. The [[Wankel engine]] operates with the same separation of phases as the four-stroke engine (but with no piston strokes, would more properly be called a four-phase engine), since the phases occur in separate locations in the engine; however like a two-stroke piston engine, it provides one power 'stroke' per revolution per rotor, giving it similar space and weight efficiency. The [[Bourke cycle]]'s combustion phase more closely approximates [[constant volume combustion]] than either four stroke or two stroke cycles do. It also uses less moving parts, hence needs to overcome less [[friction]] than the other two reciprocating types have to. In addition, its greater [[expansion ratio]] also means more of the heat from its combustion phase is utilized than is used by either four stroke or two stroke cycles.

===Fuel and oxidizer types===
Fuels used include [[gasoline]] (British term: petrol), [[Liquified Petroleum Gas]], [[Vapourized Petroleum Gas]], [[Compressed Natural Gas]], [[hydrogen]], [[diesel fuel]], [[JP18]] (jet fuel), [[landfill gas]], [[biodiesel]], [[peanut oil]], [[ethanol]], [[methanol]] (methyl or wood alcohol). Even fluidised metal powders and explosives have seen some use. Engines that use gases for fuel are called gas engines and those that use liquid hydrocarbons are called oil engines. However, gasoline engines are unfortunately also often colloquially refered to as 'gas engines'.

The main limitations on fuels are that the fuel must be easily transportable through the [[fuel system]] to the [[combustion chamber]], and that the fuel release sufficient [[energy]] in the form of [[heat]] upon [[combustion]] to make use of the engine practical.

The oxidiser is typically air, and has the advantage of not being stored within the vehicle, increasing the power-to-weight ratio. Air can, however, be compressed and carried aboard a vehicle. Some submarines are designed to carry pure [[oxygen]] or [[hydrogen peroxide]] to make them air-independent. Some race cars carry [[nitrous oxide]] as oxidizer. Other chemicals such as chlorine or fluorine have seen experimental use; but mostly are impractical.

[[Diesel engines]] are generally heavier, noisier and more powerful at lower speeds than [[gasoline engine]]s. They are also more fuel-efficient in most circumstances and are used in heavy road-vehicles, some automobiles (increasingly more so for their increased fuel-efficiency over [[gasoline engine]]s), ships and some [[locomotive]]s and light [[aircraft]]. Gasoline engines are used in most other road-vehicles including most cars, [[motorcycle]]s and [[moped]]s. Note that in [[Europe]], sophisticated diesel-engined cars have become quite prevalent since the 1990s, representing around 40% of the market. Both gasoline and diesel engines produce significant emissions. There are also engines that run on [[hydrogen car|hydrogen]], [[methanol]], [[ethanol]], [[liquefied petroleum gas]] (LPG) and [[biodiesel]]. [[Paraffin]] and [[Tractor vaporising oil]] (TVO) engines are no longer seen.

===Cylinders===
Internal combustion engines can contain any number of cylinders with numbers between one and twelve being common, though as many as 28 have been used. Having more cylinders in a engine yields two potential benefits: First. the engine can have a larger displacement with smaller individual reciprocating masses (that is, the mass of each piston can be less) thus making a smoother running engine (since the engine tends to vibrate as a result of the pistons moving up and down). Second, with a greater displacement and more pistons, more fuel can be combusted and there can be more combustion events (that is, more power strokes) in a given period of time, meaning that such an engine can generate more torque than a similar engine with fewer cylinders. The down side to having more pistons is that, over all, the engine will tend to weigh more and tend to generate more internal friction as the greater number of pistons rub against the inside of their cylinders. This tends to decrease fuel efficiency and rob the engine of some of its power. For high performance gasoline engines using current materials and technology (such as the engines found in modern automobiles), there seems to be a break point around 10 or 12 cylinders, after which addition of cylinders becomes an overall detriment to performance and efficiency, although exceptions such as the W-16 engine from [[Volkswagen]] exist.

*Most car engines have four to eight cylinders, with some high performance cars having ten, twelve, or even sixteen, and some very small cars and trucks having two or three. In previous years some quite large cars, such as the [[DKW]] and [[Saab 92]], had two cylinder, two stroke engines.

*[[Radial engine|Radial]] [[aircraft]] engines, now obsolete, had from five to 28 cylinders. A row contains an odd number of cylinders, so an even number indicates a two- or four-row engine.
*[[Motor cycle]]s commonly have from one to four cylinders, with a few high performance models having six.
*[[Snowmobile]]s usually have two cylinders. Some larger (not necessarily high-performance, but also touring machines) have four.
*Small portable appliances such as [[chainsaw]]s, generators and domestic [[lawn mower]]s most commonly have one cylinder, although two-cylinder chainsaws exist.

===Ignition system===
Internal combustion engines can be classified by their [[ignition system]]. Today most engines use an [[spark plug|electrical]] or [[compression heating ignition|compression heating]] system for ignition. However [[outside flame ignitor|outside flame]] and [[hot-tube ignitor|hot-tube]] systems have been used historically. [[Nikola Tesla]] gained one of the first patents on the mechanical ignition system with {{US patent|609250}}, "''Electrical Igniter for Gas Engines''", on 16 August 1898.

===Fuel systems===
Often for simpler reciprocating engines a [[carburetor]] is used to supply fuel into the cylinder. However, exact control of the correct amount of fuel supplied to the engine is impossible.

Larger gasoline engines such as used in cars have mostly moved to [[Fuel injection]] systems. LPG engines use a mix of [[Fuel injection]] systems and closed loop [[carburetor]]s. [[Diesel engines]] always use [[fuel injection]].

Other internal combustion engines like [[Jet engines]] use burners, and rocket engines use various different ideas including impinging jets, gas/liquid shear, preburners and many other ideas.

===Engine configuration===
Internal combustion engines can be classified by their [[engine configuration|configuration]] which affects their physical size and smoothness (with smoother engines producing less [[vibration]]). Common configurations include the [[straight engine|straight or inline configuration]], the more compact [[V engine|V configuration]] and the wider but smoother [[flat engine|flat or boxer configuration]]. Aircraft engines can also adopt a [[radial engine|radial configuration]] which allows more effective cooling. More unusual configurations, such as "[[H engine|H]]", "[[U engine|U]]", "X", or "[[W engine|W]]" have also been used.

Multiple-crankshaft configurations do not necessarily need a cylinder head at all, but can instead have a piston at each end of the cylinder, called an [[opposed piston]] design. This design was used in the [[Junkers Jumo 205]] diesel aircraft engine, using two crankshafts, one at either end of a single bank of cylinders, and most remarkably in the [[Napier Deltic]] diesel engines, which used three crankshafts to serve three banks of double-ended cylinders arranged in an equilateral triangle with the crankshafts at the corners. It was also used in single-bank locomotive engines, and continues to be used for marine engines, both for propulsion and for auxiliary generators. The [[Gnome Rotary]] engine, used in several early aircraft, had a stationary crankshaft and a bank of radially arranged cylinders rotating around it.

===Engine capacity===
An engine's capacity is the [[engine displacement|displacement]] or [[swept volume]] by the pistons of the engine. It is generally measured in [[litre]]s or cubic inches for larger engines and [[cubic centimetre]]s (abbreviated to cc's) for smaller engines. Engines with greater capacities are usually more powerful and provide greater torque at lower rpms but also consume more fuel.

Apart from designing an engine with more cylinders, there are two ways to increase an engine's capacity. The first is to lengthen the stroke and the second is to increase the piston's diameter. In either case, it may be necessary to make further adjustments to the fuel intake of the engine to ensure optimal performance.

An engine's quoted capacity can be more a matter of marketing than of engineering. The Morris Minor 1000, the Morris 1100, and the Austin-Healey Sprite Mark II all had engines of the same stroke and bore according to their specifications, and were from the same maker. However the engine capacities were quoted as 1000cc, 1100cc and 1098cc respectively in the sales literature and on the vehicle badges.

===Engine pollution===
Generally internal combustion engines, particularly reciprocating internal combustion engines, produce moderately high pollution levels, due to incomplete combustion of carbonaceous fuel, leading to carbon monoxide and some soot along with oxides of nitrogen & sulphur and some unburnt hydrocarbons depending on the operating conditions and the fuel/air ratio.

Diesel engines produce a wide range of pollutants including aerosols of many small particles that are believed to penetrate deeply into human lungs.

* Many fuels contain [[sulfur]] leading to [[sulfur oxide]]s (SOx) in the exhaust, promoting acid rain.
* The high temperature of combustion creates greater proportions of [[nitrogen oxide]]s (NOx), demonstrated to be hazardous to both plant and animal health.
* Net carbon dioxide production is not a necessary feature of engines, but since most engines are run from fossil fuels this usually occurs. If engines are run from biomass, then no net carbon dioxide is produced as the growing plants absorb as much, or more carbon dioxide while growing.
* Hydrogen engines need only produce water, but when air is used as the oxidizer nitrogen oxides are also produced.

==Bibliography==
*Singer, Charles Joseph; Raper, Richard, ''A history of technology : The Internal Combustion Engine'', edited by Charles Singer ... [et al.], Clarendon Press, 1954-1978. pp.&nbsp;157–176 [http://proxy.bib.uottawa.ca:2398/cgi/t/text/pageviewer-idx?c=acls&cc=acls&idno=heb02191.0005.001&q1=bicycle&frm=frameset&seq=5]

*Hardenberg, Horst O., ''The Middle Ages of the Internal combustion Engine'', Society of Automotive Engineers (SAE), 1999

==External links==
{{Commons|Category:Internal combustion engine}}
*[http://auto.howstuffworks.com/engine3.htm How Internal Combustion Works] - with animation

{{enWP|Internal combustion engine}}
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