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A compound engine is an engine that has more than one stage for recovering energy from the same working fluid, with the exhaust from the first stage passing through the second stage, and in some cases then on to another subsequent stage or even stages. Originally invented as a means of making steam engines more efficient, the compounding of engines by use of several stages has also been used on internal combustion engines and continues to have niche markets there. The stages of a compound engine may be either of differing or of similar technologies, for example: * In a turbo-compound engine the exhaust gas from the cylinders passes through a turbine, the two stages being dissimilar. * In a compound steam locomotive the steam passes from the high pressure cylinder or cylinders to the low pressure cylinder or cylinders, the two stages being similar. * In a triple expansion steam engine the steam passes through three successive cylinders of increasing size and decreasing pressure. Such engines were the most common marine engines in the golden age of steam. These examples and compound turbines are the main but not the only uses of compounding in engines, see below. ==Terminology== A compound engine uses several stages to produce its output. Not all engines that use multiple stages are called ''compound engines''. In particular, if an engine uses a later stage purely to extract energy from the exhaust for some other purpose, and notably for turbo charging, is not called a ''compound engine''. Similarly, proposed engines that use a free piston engine to drive a turbine would not be called ''compound engines'', as only the second stage produces output power. However if a turbo compound engine is also supercharged by feeding some of the shaft power back to the supercharger, as in some aircraft engines, it is still a compound engine. Usage of the terms ''supercharged'' and ''turbosupercharged'' has varied with time, for example the makers of the Wright R-3350 Duplex-Cyclone compound engine described it at the time as ''turbosupercharged''. It is however a compound engine, and a similar engine produced today would be described as ''supercharged'' rather than ''turbocharged''. The term compounding is a little less restrictive than ''compound engine''. Large compound turbines are an application of compounding, as are the multiple rows of blades used in many gas turbines, but neither is normally referred to as a compound engine. The several sets of blades in a single turbine are perhaps better thought of as similar in principle to the uniflow steam engine than to compounding. Unlike the uniflow steam engine, which has found niche uses only, multiple row turbines have found enormous practical application. An engine that does not use compounding is referred to as a simple engine, particularly in the case of a steam locomotive, or more precisely as a simple expansion engine, particularly in the case of a marine steam engine. Note however that in the case of any steam engine, ''simple engine'' can also be used to mean one that does not use a condenser to generate negative pressure and so improve efficiency. Use of separate condensers for this purpose is one of the key features that distinguishes the Watt steam engine of 1765 from the Newcomen steam engine of 1712. No ambiguity arises in the case of a steam locomotive, as in a condensing steam locomotive the condenser is not there to increase efficiency, and may even reduce efficiency in order to conserve water and reduce emissions. So for example the Metropolitan Railway A Class is in every sense a ''simple'' locomotive despite its condensers, and the term ''simple engine'' applied to steam locomotives always in practice means one that does not use compounding, again irrespective of its use of condensers. The terms ''simple expansion locomotive'' and ''simple expansion engine'' are sometimes applied to locomotives to remove any possible confusion. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「A compound engine is an engine that has more than one stage for recovering energy from the same working fluid, with the exhaust from the first stage passing through the second stage, and in some cases then on to another subsequent stage or even stages. Originally invented as a means of making steam engines more efficient, the compounding of engines by use of several stages has also been used on internal combustion engines and continues to have niche markets there. The stages of a compound engine may be either of differing or of similar technologies, for example:* In a turbo-compound engine the exhaust gas from the cylinders passes through a turbine, the two stages being dissimilar.* In a compound steam locomotive the steam passes from the high pressure cylinder or cylinders to the low pressure cylinder or cylinders, the two stages being similar.* In a triple expansion steam engine the steam passes through three successive cylinders of increasing size and decreasing pressure. Such engines were the most common marine engines in the golden age of steam.These examples and compound turbines are the main but not the only uses of compounding in engines, see below.==Terminology==A compound engine uses several stages to produce its output.Not all engines that use multiple stages are called ''compound engines''. In particular, if an engine uses a later stage purely to extract energy from the exhaust for some other purpose, and notably for turbo charging, is not called a ''compound engine''. Similarly, proposed engines that use a free piston engine to drive a turbine would not be called ''compound engines'', as only the second stage produces output power.However if a turbo compound engine is also supercharged by feeding some of the shaft power back to the supercharger, as in some aircraft engines, it is still a compound engine. Usage of the terms ''supercharged'' and ''turbosupercharged'' has varied with time, for example the makers of the Wright R-3350 Duplex-Cyclone compound engine described it at the time as ''turbosupercharged''. It is however a compound engine, and a similar engine produced today would be described as ''supercharged'' rather than ''turbocharged''.The term compounding is a little less restrictive than ''compound engine''. Large compound turbines are an application of compounding, as are the multiple rows of blades used in many gas turbines, but neither is normally referred to as a compound engine. The several sets of blades in a single turbine are perhaps better thought of as similar in principle to the uniflow steam engine than to compounding. Unlike the uniflow steam engine, which has found niche uses only, multiple row turbines have found enormous practical application.An engine that does not use compounding is referred to as a simple engine, particularly in the case of a steam locomotive, or more precisely as a simple expansion engine, particularly in the case of a marine steam engine.Note however that in the case of any steam engine, ''simple engine'' can also be used to mean one that does not use a condenser to generate negative pressure and so improve efficiency. Use of separate condensers for this purpose is one of the key features that distinguishes the Watt steam engine of 1765 from the Newcomen steam engine of 1712.No ambiguity arises in the case of a steam locomotive, as in a condensing steam locomotive the condenser is not there to increase efficiency, and may even reduce efficiency in order to conserve water and reduce emissions. So for example the Metropolitan Railway A Class is in every sense a ''simple'' locomotive despite its condensers, and the term ''simple engine'' applied to steam locomotives always in practice means one that does not use compounding, again irrespective of its use of condensers. The terms ''simple expansion locomotive'' and ''simple expansion engine'' are sometimes applied to locomotives to remove any possible confusion.」の詳細全文を読む スポンサード リンク
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