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A Cornish engine is a type of steam engine developed in Cornwall, England, mainly for pumping water from a mine. It is a form of beam engine that uses steam at a higher pressure than the earlier engines designed by James Watt. The engines were also used for powering man engines to assist the underground miners' journeys to and from their working levels, for winching materials into and out of the mine and for powering the ore stamping machinery. ==The Cornish cycle== The Cornish cycle operates as follows.〔http://www.croftonbeamengines.org/page13.html〕 Starting from a condition during operation with the piston at the top of the cylinder, the cylinder below the piston full of steam from the previous stroke, the boiler at normal working pressure, and the condenser at normal working vacuum, # The inlet and exhaust valves are opened. Steam from the boiler enters the top of the cylinder above the piston, and the steam below the piston is drawn into the condenser creating a vacuum below the piston. The pressure difference between the steam at boiler pressure above the piston and the vacuum below it drives the piston down. # Part way down the stroke the inlet valve is closed. The steam above the piston then expands through the rest of the stroke. # At the bottom of the stroke the exhaust valve is closed and the equilibrium valve opened. The weight of the pump gear draws the piston up and, as the piston comes up, steam is transferred through the equilibrium pipe from above the piston to the bottom of the cylinder below the piston. # When the piston reaches the top of the cylinder the cycle is ready to repeat. The next stroke may occur immediately, or it may be delayed by a timing device such as a cataract. If it was not necessary for the engine to work at its maximum rate, reducing the rate of operation saved fuel. The engine is single-acting and the steam piston is pulled up by the weight of the pump piston and rodding. Steam may be supplied at a pressure of up to . 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cornish engine」の詳細全文を読む スポンサード リンク
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