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Atmospheric engine


The atmospheric engine was invented by Thomas Newcomen in 1712, often referred to simply as a Newcomen engine. The engine operated by condensing steam drawn into the cylinder, thereby creating a partial vacuum, thereby allowing the atmospheric pressure to push the piston into the cylinder. It was the first practical device to harness steam to produce mechanical work. Newcomen engines were used throughout Britain and Europe, principally to pump water out of mines. Hundreds were constructed through the 18th century.

James Watt's later engine design was an improved version of the Newcomen engine that roughly doubled fuel efficiency. Many atmospheric engines were converted to the Watt design, for a price based on a fraction of the savings in fuel. As a result, Watt is today better known than Newcomen in relation to the origin of the steam engine.

Prior to Newcomen a number of small steam devices of various sorts had been made, but most were essentially novelties. Around 1600 a number of experimenters used steam to power small fountains working like a coffee percolator. First a container was filled with water via a pipe, which extended through the top of the container to nearly the bottom. The bottom of the pipe would be submerged in the water, making the container airtight. The container was then heated to make the water boil. The steam generated pressurized the container, but the inner pipe, immersed at the bottom by liquid, and lacking an airtight seal at top, remained at a lower pressure; expanding steam forced the water at the bottom of the container into and up the pipe to spurt out of a nozzle on top. These devices had limited effectiveness but illustrated the principle's viability.

In 1662 Edward Somerset, second Marquess of Worcester, published a book containing several ideas he had been working on. One was for a steam-powered pump to supply water to fountains; the device alternately used a partial vacuum and steam pressure. Two containers were alternately filled with steam, then sprayed with cold water making the steam within condense; this produced a partial vacuum that would draw water through a pipe up from a well to the container. A fresh charge of steam under pressure then drove the water from the container up another pipe to a higher-level header before that steam condensed and the cycle repeated. By working the two containers alternately, the delivery rate to the header tank could be increased.


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