An Introduction to Combustion
Combustion is a chemical reaction between fuel and an oxidizer that releases light and energy as heat. Fuel is any substance that releases energy when it is oxidized and an oxidizer is any substance that contains oxygen and reacts with fuel. Combustion is a very powerful form of on energy production. For example, about 90 percent of the world's energy comes from the combustion of fossil fuels.
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The Facts
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Combustion reactions that occur in small fractions of available space are called rapid modes of combustion. These reactions may result in intermediates (such as glowing particles) and create different colors of a flame. Combustion reactions that occur at low temperatures and close to a catalytic surface are called slow modes of combustion.
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Uses
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The world needs energy for a variety of reasons, including transportation, heating, industrial processes and electricity generation. Combustion takes place in drying kilns, incinerators, boilers, refineries and industrial ovens. It can also be used to create energy from biomass (such as straw, organic waste and wood). Furthermore, fuels that create combustion are found in all three states of matter; as solids (coal, biomass, waste), liquids (oil and its derivatives) and gases (natural gas, hydrogen, and propane).
Internal Combustion Engine
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A common but important example of the combustion process is the internal combustion engine found in almost all cars today. The gasoline-powered engine takes air from the atmosphere and gasoline--hydrocarbon fuel--and releases chemical energy stored as heat through the process of combustion. About 20 percent of the released energy is used to move the vehicle and the rest is lost in the actual process, according to "Combustion Chemistry" at autoshop101.com.
Function
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The chemistry that takes place within the internal combustion engine is a great example of how combustion actually occurs. Gasoline that is burned by the engine is primarily made up of a variety of hydrocarbons (chemical compounds made from hydrogen atoms that bond to carbon atoms), according to autoshop101.com. Inside the engine, the hydrocarbons only burn when they are mixed with air. Once they are mixed with air, they typically react with oxygen and form water vapor (H20) and carbon dioxide (C02).
Emissions
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Ideally, the combustion process within a gasoline-powered vehicle results in a proper effect of heat and pressure within the cylinder and the emission of nitrogen (N2) is minimal. However, emissions are a very important consideration because carbon dioxide is an end product of the reaction. As the percentage of carbon dioxide in the air increases, more of our atmosphere acts as a greenhouse (retaining heat that would otherwise end up in space). This process is called global warming and it can have a devastating effect on the future of the planet.
References
- Photo Credit "Hell and Hollywood" is Copyrighted by Flickr user: www.ericcastro.biz (Eric Castro) under the Creative Commons Attribution license.
