Editing Engine (section)

==== 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 |access-date=2011-05-09 |archive-date=2018-06-27 |archive-url=https://web.archive.org/web/20180627202610/https://www.merriam-webster.com/dictionary/external%20combustion |url-status=live }}</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)|phases]] between liquid and gas.