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Steam Engines PRESENTED BY: TOAN LUONG (THL5045) AND TIANSHI FENG (TPF5081) Introduction A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The Development of Steam Engines Using boiling water to produce mechanical motion goes back over 2000 years, but early devices were not practical. The Spanish inventor Jerónimo de Ayanz y Beaumont patented in 1606 the first steam engine. In 1698 Thomas Savery patented a steam pump that used steam in direct contact with the water being pumped. Savery's steam pump used condensing steam to create a vacuum and draw water into a chamber, and then applied pressurized steam to further pump the water. The first commercial true steam engine using a piston was developed by Thomas Newcomen and was used in 1712 for pumping in a mine. Cont’d In 1781 James Watt patented a steam engine that produced continuous rotative motion. Watt's ten-horsepower engines enabled a wide range of manufacturing machinery to be powered. The engines could be sited anywhere that water and coal or wood fuel could be obtained. By 1883, engines that could provide 10,000 hp had become feasible. Steam engines could also be applied to vehicles such as traction engines and the railway locomotives. The stationary steam engine was a key component of the Industrial Revolution, allowing factories to locate where water power was unavailable. How it Works Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be used. The ideal thermodynamic cycle used to analyze this process is called the Rankine cycle. In the cycle, water is heated and transforms into steam within a boiler operating at a high pressure. When expanded through pistons or turbines, mechanical work is done. The reduced-pressure steam is then condensed and pumped back into the boiler. There are two vital components to a steam engine. The first component is the engine itself and the second component is the boiler. Components This diagram shows the major components of a piston steam engine. This sort of engine would be typical in a steam locomotive. The engine shown is a doubleacting steam engine because the valve allows high-pressure steam to act alternately on both faces of the piston. The following animation shows the engine in action. Cont’d The high-pressure steam for a steam engine comes from a boiler. The boiler's job is to apply heat to water to create steam. There are two approaches: fire tube and water tube. In the next two slides there will be two diagrams of the fire-tube and the water-tube boilers design. However, in a real boiler, things would be much more complicated because the goal of the boiler is to extract every possible bit of heat from the burning fuel to improve efficiency. Fire-tube Boilers A fire-tube boiler was more common in the 1800s. It consists of a tank of water perforated with pipes. The hot gases from a coal or wood fire run through the pipes to heat the water in the tank, as shown here: In a fire-tube boiler, the entire tank is under pressure, so if the tank bursts it creates a major explosion. Water-tube Boilers More common today are water-tube boilers, in which water runs through a rack of tubes that are positioned in the hot gases from the fire. The following simplified diagram shows you a typical layout for a water-tube boiler: Calculations Work: Force . Distance . cos Ø Efficiency = Energy Output from Work / energy input from burning Fuel. Thus, in order to increase efficiency, we need to minimize energy input while maximize energy output. Insights If we want to improve upon an existing type of engine such as the steam engine, we need to understand how efficiency works. Accordingly, we can then use the knowledge gained from efficiency to maximize the work output with a certain amount of energy input (in case of steam engine, heat) and therefore reduce waste. Sources: http://science.howstuffworks.com/transport/enginesequipment/steam.htm http://en.wikipedia.org/wiki/Steam_engine