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Premixed combustion -Laminar finite rate model

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Old   March 16, 2004, 17:39
Default Premixed combustion -Laminar finite rate model
  #1
Shankar
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To model pre-mixed combustion, has anybody used the laminar finite rate model?

I have a few questions about this. Id appreciate it very much if anybody could help me out on this.

Thanks and Regards, Shankar.
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Old   March 16, 2004, 18:10
Default Re: Premixed combustion -Laminar finite rate model
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cg
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What are your questions?
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Old   March 16, 2004, 18:19
Default Re: Premixed combustion -Laminar finite rate model
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Shankar
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Hi

What will be the unit of A when E is in j/kg mol and other values are in SI units? ( k= A T^n exp (-E/RT) )

If you used the default reactions from the FLUENT database, do you have any idea how A and E were calculated?

I also do not understand how the value of the rate exponent was set?

Most of the literature found have the units of A and E as cm3 mol s and kJ/mol. Did you define your own reactions?

Thanks, Shankar.
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Old   March 16, 2004, 23:03
Default Re: Premixed combustion -Laminar finite rate model
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cg
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> What will be the unit of A when E is in j/kg
: mol and other values are in SI units?

The units of A depend on the reaction: the Arrhenius reaction rate is governed by the product of the species concentrations to certain powers. So, the units of A are different for each reaction.

When converting from cgs units (eg CHEMKIN) to SI (eg Fluent), you can use

A(SI) = A(cgs) * 0.001^(sum_exp-1)

where sum_exo is the sum of the rate exponents

> If you used the default reactions from
: the FLUENT database, do you have any idea
: how A and E were calculated?

Most of these came from:

Westbrook, C.K. and Dryer F.L., (1981) "Simplified Reaction Mechanisms for the Oxidation of Hydrocarbon Fuels in Flames" CST, 27, pp.31-43

> Most of the literature found have the units
: of A and E as cm3 mol s and kJ/mol. Did you
: define your own reactions?

Fluent can import mechanisms in Chemkin format.
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Old   March 17, 2004, 16:32
Default Re: Premixed combustion -Laminar finite rate model
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Shankar
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Thanks for your reply. I will go through your references.

Shankar.
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