Compound steam engine

For compound steam locomotives, see Compound locomotive.

Double-acting triple-expansion marine engine
High-pressure steam (red) passes through three stages, exhausting as low-pressure steam (blue) to the condenser
Cutaway of triple expansion compound steam engine, 1888
Robey horizontal cross-compound steam engine
small high-pressure cylinder (left) and large low-pressure cylinder (right)

A compound steam engine unit is a type of steam engine where steam is expanded in two or more stages.[1][2] A typical arrangement for a compound engine is that the steam is first expanded in a high-pressure (HP) cylinder, then having given up heat and losing pressure, it exhausts directly into one or more larger-volume low-pressure (LP) cylinders. Multiple-expansion engines employ additional cylinders, of progressively lower pressure, to extract further energy from the steam.[3]

Invented in 1781, this technique was first employed on a Cornish beam engine in 1804. Around 1850, compound engines were first introduced into Lancashire textile mills.

  1. ^ van Riemsdijk, John (1970), "The Compound locomotive, Parts 1, 2, 3", Transactions of the Newcomen Society (2)
  2. ^ Van Riemsdijk 1994, pp. 4–9.
  3. ^ Hills (1989), p. 147.