CarbonPartCombustLect27ME525SP2011

CarbonPartCombustLect27ME525SP2011 - ME 525: Combustion...

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School of Mechanical Engineering, Purdue University ME 525: Combustion Lecture 27: Carbon Particle Combustion Prof. Robert P. Lucht Room 87, Mechanical Engineering Building School of Mechanical Engineering Purdue University West Lafayette, Indiana Email: Lucht@purdue.edu Phone: 765-494-5623 April 19, 2011 1/30
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School of Mechanical Engineering, Purdue University Lecture Topics • Carbon surface reactions. • One-film model. • Two-film model. 2/30
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School of Mechanical Engineering, Purdue University Combusting Carbon Particle: Surface Reactions 1 () 2 ( ) 2 2 2 3 2 4 2 ( ) 2 22 2 sg g g g s gg g k CO C O k C O k CC O C O k CH O C OH   3/30
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School of Mechanical Engineering, Purdue University Combusting Carbon Particle: One-Film Model • Temperature and Species Profiles, One-Film Model 4/30
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School of Mechanical Engineering, Purdue University Combusting Carbon Particle: One-Film Model Assume: 1. Particle burns in quiescent, infinite medium containing O 2 and inert N 2 initially. 2. Burning process is quasi-steady. 3. Reaction 1 is dominant at the surface (not a good assumption). 4. Particle has uniform temperature, radiates as a gray body. 5. No diffusion of gas-phase species into particle. 6. Le = 1 in the gas phase 7. k g , c Pg , D g , g are constants evaluated at some mean temperature. 5/30
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School of Mechanical Engineering, Purdue University Combusting Carbon Particle: One-Film Model r s r  () 2 ( ) 2( ) 1 1 sI g I g kg C kg O kg CO  2, 2 2 1 32 /12 2.664 4 Oi I C CO I C I ii mm mr m      m   2 CO CO s m   net   2 O C m 6/30
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School of Mechanical Engineering, Purdue University Combusting Carbon Particle: One-Film Model • Following the same procedures as for the evaporating droplet we obtain:    2, , , 1/ 4l n n 1 n 1 OI OO s Cs s IO s Os I O m s Om s Y YY mr r Y Y B B Y       DD D 7/30
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School of Mechanical Engineering, Purdue University Combusting Carbon Particle: One-Film Model r s T s Y O2, T Y O2,s Y CO2,s • From a consideration of the chemical kinetics at the carbon particle surface we obtain:    2 12 2, 2 2 4 Cs C s CO s O s mix s us O mr k O M W xP Y P MW O RT  2 , 2 4 Cm i x O s Ou s Ck i n O s MW MW P k Y MW R T mK Y 8/30
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School of Mechanical Engineering, Purdue University Combusting Carbon Particle: One-Film Model, Diffusion and Kinetic Resistances • Burning of the carbon particle is controlled by the surface reaction rate and by the rate at which oxygen diffuses to the surface. To analyze these effects we develop expressions for the kinetic and diffusive resistances. Recall the expressions that we developed previously for the burning rate:   , 2, , 4l n 1 Cs O m OO s Om IO s mr B YY B Y   D 9/30
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School of Mechanical Engineering, Purdue University
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This note was uploaded on 12/27/2011 for the course ME 525 taught by Professor Lucth during the Fall '11 term at Purdue University-West Lafayette.

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CarbonPartCombustLect27ME525SP2011 - ME 525: Combustion...

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