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Steam Power.docx

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Jack Leach

Steam Power Zahra Haidari ● Scientific knowledge does not automatically lead to invention – Turning a potentially good idea into a practical invention requires time, effort and money – There must be an economic incentive to justify bearing these costs Extremely important breakthrough. Some people spent A LOT of money and hoped to get profit back. Machinery is cheaper in England and therefore did not require much labour, reducing costs. The Science ● Galileo discovered that a suction pump could not raise water more than about 9 meters A suction pump creates a vacuum, partially fills the pump… and water gets pulled up. – A suction pump operates by creating a vacuum into which the water is drawn because, according to Aristotle, “nature abhors a vacuum” – The mystery was why the water stopped rising while a vacuum remained ● Galileo was interested in this issue and confused as well, so he suggested the question to his secretary, Evangelista Torricelli, and started working on an explanation. ● 1644: Torricelli inverted a tube full of mercury in a dish of mercury, and found that the column of mercury stabilized at a height of 76 centimeters – His apparatus was essentially a barometer – A barometer is still used for forecasting the weather. – He explained the result by arguing that the atmosphere had weight that pushed down on the mercury in the bowl, supporting the column of mercury – 1648: His hypothesis is confirmed by placing the barometer in a chamber from which the air is pumped. The column falls as the air is pumped out, and rises when the air is readmitted First steam operations operated from the force of the atmosphere. ● 1655: Otto van Guericke places two hemispheres together and pumps out the air. It takes 16 horses to separate them. Anything less than 15 horses would not. The atmosphere is pressing to hemispheres together and it’s extremely difficult to pull them apart. It takes work to undo the effect of the atmosphere. ● 1672: van Guericke uses a piston and cylinder to perform work. When air is pumped out of the cylinder, atmospheric pressure pushes the piston down, lifting a weight attached to the piston ● 1675: Dennis Papin creates a vacuum in a cylinder by filling it with steam, and then condensing the steam ● 1698: Thomas Savery makes first use of steam power —in a pump, not in an engine ● Savery's pump consists of a chamber connected to three valved pipes. A human operated it in order to control series of events. – Steam is let into the chamber at nearly atmospheric pressure – The outside of the chamber is cooled to condense the steam, creating a vacuum – A valve leading to the water to be pumped is opened, causing water to be drawn into the chamber until the chamber's pressure rises to atmospheric pressure – This valve is closed, and an exhaust valve is opened. Steam is let into the chamber, driving out the water and filling the chamber. Newcomen's Engine This is NOT a steam engine. The atmosphere is doing the work (its pressure). FINAL EXAM: How does it work? ● 1712: Newcomen's atmospheric engine makes the first practical use of steam ● It is an atmospheric engine because the steam does not drive the piston—atmospheric pressure does ● The beam pivots in the middle ● The left-hand side of the beam is connected to a water pump ● The cylinder of the pump fills with water when the lefthand side falls, and the water is carried upward when the left-hand side rises ● The engine rocks the beam ● The left-hand side of the beam is more heavily weighted, so it falls ● The piston in the engine cylinder is pulled upward, drawing steam into the cylinder until the pressures in A and B are equalized ● The steam inlet is closed, and cold water from the reservoir L is sprayed into the cylinder, condensing the steam ● The condensation of the steam creates a vacuum i
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