 thumb|cutaway of triple expansion compound steam engine, 1888 thumb|a robey horizontal 'cross-compound' steam engine: the smaller, high-pressure cylinder is on the left; the larger, low-pressure cylinder on the right a compound steam engine unit is a type of steam engine where steam is expanded in two or more stages. 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. 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. ==compound systems== there are many compound systems and configurations, but there are two basic types, according to how hp and lp piston strokes are phased and hence whether the hp exhaust is able to pass directly from hp to lp (woolf compounds) or whether pressure fluctuation necessitates an intermediate "buffer" space in the form of a steam chest or pipe known as a receiver (receiver compounds). in a single-expansion (or 'simple') steam engine, the high-pressure steam enters the cylinder through a cut-off valve (archaically known as a regulator). the piston moves down the cylinder, and when it is at about 25%â33% of its stroke, the cut-off valve shuts and the steam expands, pushing the piston to the end of its stroke, the exhaust valve opens and expels the depleted steam to the atmosphere, or to a condenser. as steam expands in a high-pressure engine, its temperature drops; because no heat is released from the system, this is known as adiabatic expansion and results in steam entering the cylinder at high temperature and leaving at low temperature. this causes a cycle of heating and coo
Compound_steam_engines History_of_the_steam_engine Steam_engines Steam_locomotive_technologies