Compound engine

A compound engine is an <a href="/facts/Engine/p0m7aXaW">engine</a> that has more than one stage for recovering energy from the same <a href="/facts/Working_fluid/GvHk1AMq">working fluid</a>, 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 <a href="/facts/Steam_engine/f7hN8vzm">steam engines</a> more efficient, the compounding of engines by use of several stages has also been used on <a href="/facts/Internal_combustion_engine/Ju4BXzj0">internal combustion engines</a> and continues to have niche markets there. 
The stages of a compound engine may be either of differing or of similar technologies, for example:

<ul><li>In a <a href="/facts/Turbo-compound_engine/qr0ImDUL">turbo-compound engine</a>, the <a href="/facts/Exhaust_gas/kLpq1eUX">exhaust gas</a> from the cylinders passes through a turbine, the two stages being dissimilar.</li>
<li>In a <a href="/facts/Compound_steam_locomotive/vGMtFWxg">compound steam locomotive</a>, the steam passes from the high-pressure cylinder or cylinders to the low-pressure cylinder or cylinders, the two stages being similar.</li>
<li>In a <a href="/facts/Triple-expansion/f7hN8vzm">triple-expansion</a> 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.</li></ul>
These examples and <a href="/facts/Compound_turbine/tsU6sC9t">compound turbines</a> are the main but not the only uses of compounding in engines, see below.

Compound engine open-in-new

Compound engine