蒸汽机---从古老的往复式蒸汽机火车-到-蒸汽轮机.ppt

Steam Engines Nathan Firesheets History of Steam Engine Inventors used experimental devices, such as the rudimentary steam turbine device described by Taqi al-Din in 1551 and Giovanni Branca in 1629, to demonstrate the properties of steam. The first practical steam-powered engine was a water pump, developed in 1698 by Thomas Savery. It proved only to have a limited lift height and was prone to boiler explosions, but it still received some use for mines and pumping stations. The first commercially successful engine, the atmospheric engine, invented by Thomas Newcomen did not appear until 1712. Newcomens engine was relatively inefficient, and in most cases was only used for pumping water. History of Steam Engine James Watt developed an improved version of Newcomens engine between 1763 and 1775 which used 75% less coal than Newcomens, and was hence much cheaper to run. Watt proceeded to develop his engine further, modifying it to provide a rotary motion suitable for driving factory machinery. Early engines were atmospheric, meaning that they were powered by the vacuum generated by condensing steam instead of the pressure of expanding steam. Cylinders had to be large, as the only usable force acting on them was atmospheric pressure. Steam was only used to compensate for the atmosphere allowing the piston to move back to its starting position. Even if pressured steam had been available, it could not do any work (push) against the chain connecting the piston to the beam. Early Watt Steam pumping engine. History of Steam Engines Around 1800, Richard Trevithick introduced engines using high-pressure steam. These were much more powerful than previous engines and could be made small enough for transport applications. Thereafter, technological developments and improvements in manufacturing techniques (partly brought about by the adoption of the steam engine as a power source) resulted in the design of more efficient engines that could be smaller, faster, or more powerfu