What is "steam engine"

Steam engine \Steam" en"gine\ ([e^]n"j[i^]n). An engine moved by steam. Note: In its most common forms its essential parts are a piston, a cylinder, and a valve gear. The piston works in the cylinder, to which steam is admitted by the action of the valve gear, and communicates motion to the machinery to be actuated. Steam engines are thus classified:

1. According to the way the steam is used or applied, as condensing, noncondensing, compound, double-acting, single-acting, triple-expansion, etc.

2. According to the motion of the piston, as reciprocating, rotary, etc.

3. According to the motion imparted by the engine, as rotative and nonrotative.

4. According to the arrangement of the engine, as stationary, portable, and semiportable engines, horizontal and vertical engines, beam engine, oscillating engine, direct-acting and back-acting engines, etc.

5. According to their uses, as portable, marine, locomotive, pumping, blowing, winding, and stationary engines, the latter term referring to factory engines, etc., and not technically to pumping or blowing engines. Locomotive and portable engines are usually high-pressure, noncondensing, rotative, and direct-acting. Marine engines are high or low pressure, rotative, and generally condensing, double-acting, and compound. Paddle engines are generally beam, side-lever, oscillating, or direct-acting. Screw engines are generally direct-acting, back-acting, or oscillating. Stationary engines belong to various classes, but are generally rotative. A horizontal or inclined stationary steam engine is called a left-hand or a right-hand engine when the crank shaft and driving pulley are on the left-hand side, or the right-hand side, respectively, of the engine, to a person looking at them from the cylinder, and is said to run forward or backward when the crank traverses the upward half, or lower half, respectively, of its path, while the piston rod makes its stroke outward from the cylinder. A marine engine, or the engine of a locomotive, is said to run forward when its motion is such as would propel the vessel or the locomotive forward. Steam engines are further classified as double-cylinder, disk, semicylinder, trunk engines, etc. Machines, such as cranes, hammers, etc., of which the steam engine forms a part, are called steam cranes, steam hammers, etc. See Illustration in Appendix.

   Back-acting steam engine, or Back-action steam engine, a steam engine in which the motion is transmitted backward from the crosshead to a crank which is between the crosshead and the cylinder, or beyond the cylinder.

   Portable steam engine, a steam engine combined with, and attached to, a boiler which is mounted on wheels so as to admit of easy transportation; -- used for driving machinery in the field, as thrashing machines, draining pumps, etc.

   Semiportable steam engine, a steam engine combined with, and attached to, a steam boiler, but not mounted on wheels.

n. 1 A piston engine driven by steam (as contrasted, for example, with a steam turbine). 2 Any heat engine that uses steam as its primary working fluid to do mechanical work. 3 (context British English) A steam locomotive.

n. external-combustion engine in which heat is used to raise steam which either turns a turbine or forces a piston to move up and down in a cylinder

A steam engine is a heat engine that performs mechanical work using steam as its working fluid.

Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be used. The ideal thermodynamic cycle used to analyze this process is called the Rankine cycle. In the cycle, water is heated and transforms into steam within a boiler operating at a high pressure. When expanded through pistons or turbines, mechanical work is done. The reduced-pressure steam is then condensed and pumped back into the boiler.

In general usage, the term steam engine can refer to either the integrated steam plants (including boilers etc.) such as railway steam locomotives and portable engines, or may refer to the piston or turbine machinery alone, as in the beam engine and stationary steam engine. Specialized devices such as steam hammers and steam pile drivers are dependent on the steam pressure supplied from a separate boiler.

Using boiling water to produce mechanical motion goes back over 2000 years, but early devices were not practical. The Spanish inventor Jerónimo de Ayanz y Beaumont obtained the first patent for a steam engine in 1606. In 1698 Thomas Savery patented a steam pump that used steam in direct contact with the water being pumped. Savery's steam pump used condensing steam to create a vacuum and draw water into a chamber, and then applied pressurized steam to further pump the water. Thomas Newcomen's atmospheric engine was the first commercial true steam engine using a piston, and was used in 1712 for pumping in a mine.

In 1781 James Watt patented a steam engine that produced continuous rotary motion. Watt's ten- horsepower engines enabled a wide range of manufacturing machinery to be powered. The engines could be sited anywhere that water and coal or wood fuel could be obtained. By 1883, engines that could provide 10,000 hp had become feasible. The stationary steam engine was a key component of the Industrial Revolution, allowing factories to locate where water power was unavailable. The atmospheric engines of Newcomen and Watt were large compared to the amount of power they produced, but high pressure steam engines were light enough to be applied to vehicles such as traction engines and the railway locomotives.

Reciprocating piston type steam engines remained the dominant source of power until the early 20th century, when advances in the design of electric motors and internal combustion engines gradually resulted in the replacement of reciprocating (piston) steam engines in commercial usage, and the ascendancy of steam turbines in power generation. Considering that the great majority of worldwide electric generation is produced by turbine type steam engines, the "steam age" is continuing with energy levels far beyond those of the turn of the 19th century.