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-   -   Premixed combustion -Laminar finite rate model (http://www.cfd-online.com/Forums/fluent/33253-premixed-combustion-laminar-finite-rate-model.html)

 Shankar March 16, 2004 17:39

Premixed combustion -Laminar finite rate model

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.

 cg March 16, 2004 18:10

Re: Premixed combustion -Laminar finite rate model

 Shankar March 16, 2004 18:19

Re: Premixed combustion -Laminar finite rate model

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.

 cg March 16, 2004 23:03

Re: Premixed combustion -Laminar finite rate model

> 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