A steam engine is a heat engine of external combustion that converts the energy of water vapor into mechanical work of reciprocating piston motion, and then into rotational motion of the shaft. In a broader sense, a engine is any external combustion engine that converts energy into mechanical work.
The first engine built in the XVII century Papen and was represented by a cylinder with a piston, which was raised by the action of and lowered the pressure of the atmosphere after the condensation of exhaust steam. On the same principle were built in 1705 vacuum machines Severi and Newcomen . Significant improvements in the vacuum steam engine were made by James watt in 1769. Further significant improvements to the engine (the use of high-pressure instead of vacuum) were made by the American Oliver Evans in 1786 and the Englishman Richard to drive the engine needed a boiler. Expanding steam puts pressure on the piston or on the blades of the steam turbine, the movement of which is transmitted to other mechanical parts.
The operating principle , the bearing flywheel , which serves to reduce the unevenness of the shaft rotation. The eccentric sitting on the main shaft, by means of eccentric thrust drives the spool , controlling the inlet of steam in the cylinder cavity. Steam from the cylinder is released into the atmosphere or enters the condenser. To maintain a constant number of revolutions of the shaft at a changing load, machines are equipped with a centrifugal regulator 9, automatically changing the cross section of the passage e machine (throttle control, shown in the figure), or the moment of filling cutoff (quantitative control).
The piston forms one or two cavities of variable volume, in which the processes of compression and expansion are performed, by the curves of the pressure dependence on the volume.
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