5310 Combustion Introduction Lecture 16

5310 Combustion Introduction Lecture 16 - MAE 5310...

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MAE 5310: COMBUSTION FUNDAMENTALS Introduction to Laminar Flames Laminar Premixed Flames and Diffusion Flames Molecular Diffusion Mechanical and Aerospace Engineering Department Florida Institute of Technology D. R. Kirk
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COMBUSTION MODES AND FLAME TYPES Combustion can occur in flame mode Premixed flames Diffusion (non-premixed) flames Combustion can occur in non-flame mode What is a flame? A flame is a self-sustaining propagation of a localized combustion zone at subsonic velocities Flame must be localized: flame occupies only a small portion of combustible mixture at any one time (in contrast to a reaction which occurs uniformly throughout a vessel) A discrete combustion wave that travels subsonically is called a deflagration Combustion wave may be also travel at supersonic velocities, called detonation Fundamental propagation mechanism is different in deflagrations and detonations Laminar vs. Turbulent Flames: both have same type of physical process and many turbulent flame theories are based on an underlying laminar flame structure
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LAMINAR PREMIXED FLAMES Fuel and oxidizer mixed at molecular level prior to occurrence of any significant chemical reaction Air Fuel
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DIFFUSION FLAMES Reactants are initially separated, and reaction occurs only at interface between fuel and oxidizer (mixing and reaction taking place) Diffusion applies strictly to molecular diffusion of chemical species In turbulent diffusion flames, turbulent convection mixes fuel and air macroscopically, then molecular mixing completes the process so that chemical reactions can take place Orange Blue Full range of φ throughout reaction zone
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LOOK AGAIN AT BUNSEN BURNER Fuel-rich pre-mixed inner flame
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This note was uploaded on 02/11/2012 for the course MAE 5310 taught by Professor Danielkirk during the Fall '09 term at FIT.

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5310 Combustion Introduction Lecture 16 - MAE 5310...

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