An external combustion engine (EC engine) is a heat engine where an internal working fluid is heated, often from an external source, through the engine wall or a heat exchanger. The fluid then performs work during expansion and by acting on the mechanism of the engine provides usable motion and usable work. The fluid is then cooled (closed cycle) or dumped and cool fluid pulled in (open cycle). Burning fuel with an oxidizer, or any other heat source can supply the external heat, hence "external combustion". The internal fluid is quite often an inert gas. The fluid can be any liquid or more commonly, any gas, as well as mixtures. In the case of the steam engine, the fluid changes phases between liquid and gas. A heat engine is a physical or theoretical device that converts thermal energy to mechanical output. ... A fluid is defined as a substance that continually deforms (flows) under an applied shear stress regardless of the magnitude of the applied stress. ... An engine is something that produces an effect from a given input. ... A heat exchanger is a device built for efficient heat transfer from one fluid to another, whether the fluids are separated by a solid wall so that they never mix, or the fluids are directly contacted. ... A fluid is defined as a substance that continually deforms (flows) under an applied shear stress regardless of the magnitude of the applied stress. ... Look up work in Wiktionary, the free dictionary. ... Expansion can have several meanings, including: In physics: Expansion of space In computer hardware: an Expansion card In computer programming: In-line expansion In computer gaming: an expansion pack See also: Wikipedia:Requests for expansion This is a disambiguation page — a navigational aid which lists other pages that might... Look up mechanism in Wiktionary, the free dictionary. ... Burning may refer to any of the following: Combustion The use of a CD burner The Burning Man festival Burning-in of Photographic paper Immolation An insult (slang term) This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Fuel is any material that is capable of releasing energy when its chemical or physical structure is changed or converted. ... An oxidizing agent is a substance that oxidizes another substance in electrochemistry or redox chemical reactions in general. ... An inert gas is any gas that is not reactive under normal circumstances. ... A liquid will usually assume the shape of its container A liquid is one of the main states of matter. ... This article or section does not cite its references or sources. ... // The term steam engine may also refer to an entire railroad steam locomotive. ... Look up Phase in Wiktionary, the free dictionary Phase may refer to: Phase (matter), a physically distinctive form of a substance, such as the solid, liquid, and gaseous states of ordinary matter Phase (waves), the time position (or angle in the complex plane) within a cycle of a periodic waveform...

There are few if any limitations to the type of cycle that can be run in an EC engine, nor does it necessarily matter whether the cycle is open or closed. However, some cycles are more common as EC or IC engines. John Ericsson built an engine running on the diesel cycle as an external combustion engine with an open cycle. The Diesel cycle is the combustion process of a type of reciprocating internal combustion engine, in which the fuel is ignited by the heat generated in first compressing air in the combustion chamber, into which is then injected the fuel, as opposed to it being ignited by a spark plug...

EC engines require at least one heat exchanger and often have two, for supplying the heat into and removing the heat from the engine. The necessary temperature difference is then available to the engine. In contrast, IC engines have a heat exchanger, commonly called a cooling system, to keep the combustion chamber from overheating. Thus, the IC engine must remove heat as waste. A device called a regenerator in the EC engine saves some of that heat and is why it can be more efficient. The EC engine's heat transfer technology requires greater care during the engineering process than a cooling system. EC engines often have cooling systems, however, they may or may not be smaller than a corresponding IC engine's. A Stirling engine and generator set with 55 kW electrical output, for combined heat and power applications. ... Engineering is the design, analysis, and/or construction of works for practical purposes. ...

Since the combustion is external to the mechanism, they are much less particular about the type of fuel they burn. They also tend to be cleaner because the combustion is continuous and more easily regulated for temperature, oxidizers and fuel amount. If lower combustion temperatures and pressures are used it will create less exotic exhaust gases, such as nitrogen oxides (NO, NO₂ etc.).

Examples: A steam turbine is a good example of an external-combustion engine. Heat from a burning fuel/oxidizer mix, or from a nuclear reactor changes water in a device called a boiler to steam. Pipes carry the steam into the turbine, which has a series of bladed wheels attached to a shaft. The high-temperature steam expands as it rushes through the turbine and so pushes on the blades and causes them to turn the shaft. Steam leaving the turbine has a much lower temperature. The spinning shaft can drive an electric generator, move a ship's propeller, or do other useful work. A rotor of a modern steam turbine, used in a power plant A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into useful mechanical work. ... A boiler is a closed vessel in which water or other fluid is heated under pressure. ... It has been suggested that this article be split into articles entitled steam and water vapor, accessible from a disambiguation page. ... A Siemens steam turbine with the case opened. ...

Some other externally heated cycles are Stirling cycle, Ericsson Cycle, Papin and Brayton cycle. The Stirling engine is a type of hot air engine, invented in 1816 by the Rev. ... This article or section seems not to be written in the formal tone expected of an encyclopedia entry. ... The Brayton cycle is a cyclic process generally associated with the gas turbine. ...

See also

• steam engines
• Stirling engines
• internal combustion engine