Steam Engine: An engine worked by steam, typically one in which a sliding piston in a cylinder is moved by the expansive action of the steam generated in a boiler.
Steam engines come under the category of external combustion engines. Here the working and flowing fluid is different. What happens here is that water is boiled in a separate chamber using coal or any other source of energy to produce steam. This pressurized steam is then flown through the piston of the engine to produce mechanical work. After the steam expands, does the work and condenses, it is pulled back into the chamber where it is again converted to steam and the cycle goes on.
The first steam-powered machine was built in 1698 by the English military engineer Thomas Savery (c. 1650–1715). His invention, designed to pump water out of coal mines, was known as the Miner’s Friend. The machine, which had no moving parts, consisted of a simple boiler—a steam chamber whose valves were located on the surface—and a pipe leading to the water in the mine below.
Water was heated in the boiler chamber until its steam filled the chamber, forcing out any remaining water or air. The valves were then closed and cold water was sprayed over the chamber. This chilled and condensed the steam inside to form a vacuum. When the valves were reopened, the vacuum sucked up the water from the mine, and the process could then be repeated.