View source for External combustion engine

{{Redirect|External combustion|the album|External Combustion}}
{{Short description|Type of reciprocating heat engine}}
[[File:Stirling Engine.jpg|thumb|Model [[Stirling engine]], with external heat from a [[spirit lamp]] (bottom right) applied to the outside of the glass displacer cylinder.]]
[[File:Newcomen atmospheric engine animation.gif|thumb|upright|[[Newcomen engine|Newcomen's engine]], a precursor of the [[steam engine]], with the boiler heated from beneath]]
[[File:Cutaway steam locomotive.jpg|thumb|Sectioned [[steam locomotive]]. Although the fire is within an enclosed [[firebox (steam engine)|firebox]], this is still an ''external'' combustion engine, as the [[exhaust gas]] and the steam working fluid are kept separate.]]
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An '''external combustion engine''' ('''EC engine''') is a [[Reciprocating engine|reciprocating]] [[heat engine]] where a [[working fluid]], contained internally, is heated by combustion in 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>[http://www.merriam-webster.com/dictionary/external%20combustion external combustion - Definition from the Merriam-Webster Online Dictionary]</ref> The fluid is then dumped (open cycle), or cooled, compressed and reused (closed cycle). 
In these types of engines, the combustion is primarily used as a heat source, and the engine can work equally well with other types of heat sources.

==Combustion==
"[[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; they are not then strictly classed as external combustion engines, but as external thermal engines.

==Working fluid==
The working fluid can be of any composition and the system may be single-phase (liquid only or gas only) or dual-phase (liquid/gas).

===Single phase===
[[Gas]] is used in a [[Stirling engine]]. Single-phase [[liquid]] may sometimes be used.{{clarify|date=February 2012}}

===Dual phase===
Dual-phase external combustion engines use a [[Phase (matter)|phase]] transition to convert temperature to usable work, for example from liquid to (generally much larger) gas.  This type of engine follows variants of the [[Rankine cycle]].  [[Steam engine]]s are a common example of dual-phase engines.  Another example is engines that use the [[Organic Rankine cycle]].

==See also==
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*[[Organic Rankine cycle]]
*[[Steam engine]]s
*[[Stirling engine]]s
*[[Swing-piston engine|Trochilic engine]]
*[[Internal combustion engine]] (ICE)
*[[Nuclear power]]
*[[Solar thermal rocket]] (an externally heated rocket)
*[[Naptha engine]], a variant of the steam engine, using a petroleum liquid as both fuel and working fluid.
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==References==
{{Reflist}}

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[[Category:Engines]]
[[Category:External combustion engines| ]]