compound engine

A compound engine is a type of engine, often a steam engine, designed to minimize energy losses. It achieves this by expanding the working fluid, such as steam, in two distinct stages. First, the fluid expands in a high-pressure cylinder. Then, it moves to a low-pressure cylinder for further expansion before being exhausted, often into a condenser. This process allows for a higher overall expansion ratio compared to a simple engine, where expansion occurs in a single phase. In aeronautics, a compound engine can also refer to a complex propulsive system involving a reciprocating engine, a gas turbine, and a compressor working together.12