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A steam engine is an External Combustion Heat Engine that makes use of the Thermal Energy that exists in Steam , converting it to Mechanical Work . Steam engines were used as the Prime Mover in Pump s, Locomotive s, Steam Ship s and Steam Tractor s, and were essential to the Industrial Revolution . Steam Turbine s, technically a type of steam engine, are still widely used for generating Electricity , but older types have been almost entirely replaced by Internal Combustion engines and Electric Motor s. A steam engine requires a Boiler to boil Water to produce steam. The expansion—or contraction—of steam exerts force upon a piston or turbine blade, whose Motion can be harnessed for the work of turning wheels or driving other machinery. One of the advantages of the steam engine is that any Heat source can be used to raise steam in the boiler; but the most common is a Fire fueled by Wood , Coal or Oil or the utilisation of the heat energy generated in a Nuclear Reactor . INVENTION AND DEVELOPMENT The first recorded steam device, the ''aeolipile'' , was invented by Hero Of Alexandria , a Greek , in the 1st Century AD, but used only as a toy. .]]In 1663 , Edward Somerset, 2nd Marquess Of Worcester published designs for, and may have installed, a steam-powered engine for pumping water at Vauxhall House. In about 1687 the French physicist Denis Papin , with the help of Gottfried Leibniz , built a working model of a steam engine and a paddle steam boat. Papin is also credited with a number of significant devices such as the Safety Valve . Sir Samuel Morland also developed ideas for a steam engine during the same period and built a number of steam-engine pumps for King Louis XIV of France in the 1680s . Early industrial steam engines were designed by Thomas Savery (the "fire-engine", 1698 ) but it was Thomas Newcomen and his "atmospheric-engine" of 1712 that demonstrated the first operational and practical industrial engine. Together, Newcomen and Savery developed a Beam Engine that worked on the atmospheric, or Vacuum , principle. The first industrial applications of the vacuum engines were in the pumping of water from deep mineshafts. In mineshaft pumps the reciprocating beam was connected to an operating rod that descended the shaft to a pump chamber. The oscillations of the operating rod are transferred to a pump piston that moves the water, through check valves, to the top of the shaft. Early Newcomen engines operated so slowly that the valves were manually opened and closed by an attendant. An improvement was the replacement of manual operation of the valves with an operation derived from the motion of the engine itself, by lengths of rope known as "''potter cord''" (legend has it that this was first done in 1713 by a boy, Humphrey Potter, charged with opening the valves; when he grew bored he set up ropes to automate the process. {Link without Title} ) Humphrey Gainsborough produced a model Condensing steam engine in the 1760s , which he showed to James Watt of Glasgow Green , Scotland . In 1769 Watt patented the first significant improvements to the Newcomen type vacuum engine that made it much more fuel efficient. Watt's leap was to separate the condensing phase of the vacuum engine into a separate chamber, while keeping the piston and cylinder at the temperature of the steam. Watt, together with his business partner Matthew Boulton , developed these patents into the Watt Steam Engine in Birmingham , England. The increased efficiency of the Watt engine finally led to the general acceptance and use of steam power in industry. Additionally, unlike the Newcomen engine, the Watt engine operated smoothly enough to be connected to a drive shaft—via Sun And Planet Gear s—to provide rotary power. In early steam engines the piston is usually connected to a balanced beam, rather than directly to a Connecting Rod , and these engines are therefore known as beam engines. (350 KPa ).]] The next improvement in efficiency came with the American Oliver Evans and the Briton Richard Trevithick 's use of high pressure steam. Trevithick built successful industrial high pressure single-acting engines known as Cornish Engine s. However with increased pressure came much danger as engines and boilers were now likely to fail mechanically by a violent outwards explosion, and there were many early disasters. The most important refinement to the high pressure engine at this point was the safety valve, which releases excess pressure. Reliable and safe operation came only with a great deal of experience and codification of construction, operating, and maintenance procedures. Nicolas-Joseph Cugnot demonstrated the first functional self-propelled steam vehicle, his "fardier" (steam wagon), in 1769. Arguably, this was the first Automobile . While not generally successful as a transportation device, the self-propelled steam Tractor proved very useful as a self mobile power source to drive other farm machinery such as Grain Threshers or hay Baler s. In 1802 William Symington built the "first practical steamboat", and in 1807 Robert Fulton used the Watt steam engine to power the first commercially successful Steamboat . On February 21 , 1804 at the Pen-y-Darren Ironworks in Wales , the first self-propelled Railway steam engine or steam locomotive, built by Richard Trevithick, was demonstrated. RECIPROCATING ENGINES Reciprocating engines use the action of steam to move a piston in a sealed chamber. The reciprocal action of the piston can be translated via a mechanical linkage into rotary work. Vacuum engines Early steam engines, such as Newcomen's "atmospheric" and Watt's "condensing" engines, worked on the vacuum principle and are thus known as vacuum engines. Such engines operate by admitting low pressure steam into an operating chamber and closing the inlet valve. The steam is then cooled, the resultant water vapor condensing to a smaller volume than the steam, creating a vacuum in the chamber. Atmospheric Pressure , operating on the opposite side of a piston, pushes the piston to the bottom of the chamber. The piston is connected to a large beam and counterweight, the weight of which returns the piston to the top of the chamber; the low pressure steam is insufficient to move the piston upwards alone. The reciprocating action of the beam can be harnessed to do mechanical work. In the Newcomen engine cooling water is sprayed directly into the working chamber but in the Watt engine there is a separate condensing chamber, connected to the working chamber by a valve. The inefficiency of the Newcomen engine lay in the repeated and wasteful heating and cooling of the working chamber. By removing the condensing phase of the action to a separate chamber this was greatly reduced and the efficiency of the engine was greatly increased. Vacuum engines are severely limited in their efficiency but are relatively safe since the steam is at very low pressure and structural failure of the engine will be by inward collapse rather than an outward explosion. Their power is limited by the ambient air pressure, the displacement of the working chamber, the combustion and evaporation rates and—where present—the condenser capacity. The maximum theoretical efficiency is limited by the relatively low boiling point of water at near atmospheric pressure (100 °C , 212 °F ). High pressure engines |
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