External combustion engine
From Wikipedia, the free encyclopedia
An external combustion engine is a heat engine which burns fuel to heat a separate working fluid which then in turn performs work. Examples include steam engines and Stirling engines.
For the same power, external combustion engines are often less compact and heavier than internal combustion engines. This is because they contain a heat exchanger to heat the working fluid. However, they can be more efficient, and are much less particular about the type of fuel they burn. They also tend to be cleaner due to lower combustion temperatures and pressures which create less exotic exhaust gasses, such as nitrogen oxides (NO, NO2 etc.).
A steam turbine is a good example of an external-combustion engine. Heat from burning fuel or from a nuclear reactor changes water in 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. Externally heated cycles include the Stirling cycle, Ericsson Cycle and Brayton cycle.es:Motor de combustión externa it:Motore a combustione esterna he:מנוע בעירה חיצונית ja:外燃機関 ru:Двигатель внешнего сгорания sk:Motor s vonkajším spaľovaním tr:Dıştan yanmalı motor zh:外燃机
