DropletCombustLect26ME525SP2011

# DropletCombustLect26ME525SP2011 - ME 525: Combustion...

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School of Mechanical Engineering, Purdue University ME 525: Combustion Lecture 26: Droplet Evaporation and Burning II Prof. Robert P. Lucht Room 87, Mechanical Engineering Building School of Mechanical Engineering Purdue University West Lafayette, Indiana Email: [email protected] Phone: 765-494-5623 Thursday, April 14, 2011

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School of Mechanical Engineering, Purdue University Lecture Topics • Model for droplet evaporation and burning. • Evaluation of model constants. • Correction factors.
School of Mechanical Engineering, Purdue University Combusting Droplet: Combined Evaporation and Burning

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School of Mechanical Engineering, Purdue University Combusting Droplet: Combined Evaporation and Burning
School of Mechanical Engineering, Purdue University Combusting Droplet: Combined Evaporation and Burning Assume: 1. Droplet is surrounded by a spherical flame in a quiescent, infinite medium 2. Quasi-steady process (droplet radius changes slowly in time) 3. Fuel is single-component, no dissolved gases in droplet (including product gases), no other condensed phases 4. Droplet temperature is uniform: T d is slightly less than T boil 5. Pressure is uniform and constant.

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School of Mechanical Engineering, Purdue University Combusting Droplet: Combined Evaporation and Burning Assume also: 6 . Le = 1 Z = Z F = Z T 7. k g , c Pg , and g are constants evaluated at some mean temperature 8. One step reaction, three species: fuel, product, oxidizer 9. Radiation heat transfer is neglected 10. Buoyancy is neglected 11. At the droplet surface, P F,s = P vap (T s )
School of Mechanical Engineering, Purdue University Combusting Droplet: Combined Evaporation and Burning In this problem analysis: Knowns: Unknowns: , ,, 1 so x rT Y   , , , FF sff s sb o i l mY Tr T we assume T T r f r s T s T f Y ox, T Y F,s

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School of Mechanical Engineering, Purdue University Combusting Droplet: Gas Phase Conservation Equations r>r s Mass Conservation: r s   2 2 v4 F r mr m r const     Assume no dissolved products in the droplet. Outer Region r f r Inner Region Products form a stagnant film in the inner region r s < r < r f
School of Mechanical Engineering, Purdue University Combusting Droplet: Species Conservation, Inner Region r s < r < r f Species Conservation   AA A B A B A B A mY m YY m m Y     DD Let species A be the fuel and species B be the product: Pr 0 A FF F B mmY m Y mm  D

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School of Mechanical Engineering, Purdue University Combusting Droplet: Species Conservation, Inner Region r s < r < r f r r s r f Inner Region Outer Region In spherical coordinates, this becomes: 2 41 F F FF F F F F dY dY mY m Y m dr dr md Y m rY d r      DD D Apply boundary conditions:      , 0 Fs F s s Ff Yr Y T
School of Mechanical Engineering, Purdue University Combusting Droplet: Species

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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.

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DropletCombustLect26ME525SP2011 - ME 525: Combustion...

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