ME300Lecture21

ME300Lecture21 - Lecture 21 Stoichiometry of Reactions...

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21.1 Lecture 21 : Stoichiometry of Reactions Objective: » Systems involving chemical reactions » Chemical composition changing during a process Combustion Process: » The rapid oxidation of combustible elements of fuel for energy release: Fuel + Oxidizer Exhaust Gases (Reactants) (Products) » Usually requires “ignition”
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21.2 Continue Combustion Process Fuels: » Major combustible chemical elements in common fuels: Carbon, Hydrogen, and Sulfur » Most common fuel : Hydrocarbons, C x H y » e.g., Substance chemical formula methane CH 4 propane C 3 H 8 octane C 8 H 18
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21.3 Continue Combustion Process Combustion Air (Oxidizer) » In most combustion processes, air provides the needed oxygen, although pure oxygen (O 2 ) would be best » Modeling of combustion air: Air only consists of 21% oxygen and 79% nitrogen on a molar basis (by volume) molar ratio of N 2 to O 2 = 3.76 1 mol O 2 + 3.76 mols N 2 = 4.76 mols air Air is considered on a dry basis (no moisture) Nitrogen is inert (does not participate in the reaction) Conservation of Mass » Mass of reactant elements = Mass of product elements
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