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Where to set fuel for XiFOAM

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Old   February 1, 2017, 17:45
Default Where to set fuel for XiFOAM
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Shuai Yuan
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Hello everyone,

I am wondering whether XiFOAM does not deal with chemical reaction mechanism? I assume that XiFOAM only require the property of fuel, product and the stoichiometric ratio, which ignore the detailed chemical reaction mechanism. Am I correct?

I am confused that in the tutorial case set up, the thermophysicalproperties has only one species but why there are three species' laminar flame speeds in combustionProperties. Can anyone explain this for me?

Thanks!!
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Old   February 1, 2017, 17:57
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Oskar
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Hello sy2516.

Xifoam could run with three different mixture models:
HomogeneousMixture,
InhomogeneousMixture,
veryInhomogeneousMixture.

Xifoam tutorial use homogeneousMixture so you only need to specify properties of reactants as a mixture and burn products as a mixture.

In InhomogenousMixture You need to specify oxidant and fuel properties separately (burn products still as a mixture).

In veryInhomogeneousMixture You need to specify all species of reactants and burn products.


You are right that there is no chemical mechanism.

It is because combustiuonProperties file is more universal. I mean combustion properties are something different that thermophysical properties. combustionProperties file belongs to xiFoam where guilders coefficient for propane, methane and isoOctane are define. thermophysicalProperties belongs to janaf thermochemical model.
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Old   February 1, 2017, 18:19
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Thank you for your reply.

I am still confused that if the fuel is propane, why there are laminar flame speed of propane, methane and iso-octane in the combustionProperties file?

Besides, I compared the tutorial case for OpenFOAM 1.7.x and OpenFOAM 4.0. I found that in OpenFOAM 1.7.x, it specify the reactants, oxidant, fuel, products and burnt products. I am not sure whether the n_moles of reactants includes the fuel and oxidant? I assume the n_moles is the mole number. Is it correct? In OpenFOAM 4.0, the tutorial only includes reactant and product, however, the product is not the burnt products in tutorial of OpenFOAM 1.7.x. That makes me totally confused...
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Old   February 1, 2017, 19:33
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It is done just so You can easier switch between those three fuels. openFoam does not store guilders coefficient inside its code. Guilders coefficients are stored in combustionProperties file.

My only experience comes from engineFoam solver (where combustion model is xiFoam).
I think if You use inhomogeneousMixture nMoels should be 1 because solver use stoichiometricAirFuelMassRatio to calculate moles of mixture.
If You use homogeneousMixture there is no stoichiometricAirFuelMassRatio. Then nMoles should be ("stoichiometric-Air-Fuel-Mole-Ratio" + 1). It is numbers of moles of mixture corresponding to 1 mole of fuel.
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Old   February 1, 2017, 19:37
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Thank you!

I found the answer in the following link and I would like to share it with you.

Janaf coefficient for gaz mixture + nMoles ?
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