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-   -   change equivalenceRatio (http://www.cfd-online.com/Forums/openfoam-solving/79448-change-equivalenceratio.html)

sobhanEK August 24, 2010 09:08

change equivalenceRatio
 
Hi everyone.
I want to change equivalenceRatio in XiFoam.
I changed equivalenceRatio in combustionProperties file.
if I should change thermophysicalProperties datas?
Please someone help me.
Thanks.

rflats October 25, 2010 15:32

You can use adiabaticFlameT, which is in $FOAM_APP/utilities/thermophysical directory.

remir July 27, 2014 04:29

Hi, I know it's been a while since your post, but I was asking myself the same question : is changing the equivalence ratio parameter in combustionProperties enough, or should we change the Cp coeff in thermophysicalProperties as well?

As we can see in the XiFoam test case PitzDaily, with propane for fuel and air for oxydant, the thermophysicalProperties directory looks like this:

CASE 1

reactants
specie, thermodynamics, transport
products
specie, thermodynamics, transport

For the reactants, the molWeight coeff is equal to 29.4649, which corresponds to a 4% propane 96% air mixture, equivalence ratio of 1.

On the other hand, I found another type of directory, in which the following can be found:

CASE 2

fuel
specie, thermodynamics, transport
oxidant
specie, thermodynamics, transport
reactants
specie, thermodynamics, transport
products
specie, thermodynamics, transport
burntProducts
specie, thermodynamics, transport


For the reactants, the molWeight coeff is now 29.48 (4.1% propane 95.9% air). This is quite similar, but I must say that the results I obtain with the Pitz and Daily case are different in term of temperature for these two cases.

In the first one, the temperature (ER=1) is about 2300K
In the second one, same conditions, 1700K.

In both cases anyway, changing the equivalence ratio in the combustionProperties directory doesn't seem to affect the maximum temperature of the flow, but the recirculation length. (Someone had the same issue?)

I'm starting to think that the parameter "equivalence ratio" in combustion properties is only here to compute the GuldersCoeffs of the mixture air+fuel, and not the thermodynamic properties of this mixture. Indeed, I don't see how OpenFoam could calculate the Cp of the mixture if the only thing I give in thermophysicalProperties is the reactants and products thermo coeff for a specified equivalence ratio, as seen in the case 1. Again, I suspect I'm totally wrong on this, and blind regarding this matter, so if you get more info, please help me :)


I would be really interested in finding more about this solver (where is the temperature calculated exactly for example?), and in the different directories in general.


Best,

Remir

Howard March 19, 2015 06:08

Quote:

Originally Posted by remir (Post 503303)
Hi, I know it's been a while since your post, but I was asking myself the same question : is changing the equivalence ratio parameter in combustionProperties enough, or should we change the Cp coeff in thermophysicalProperties as well?

As we can see in the XiFoam test case PitzDaily, with propane for fuel and air for oxydant, the thermophysicalProperties directory looks like this:

CASE 1

reactants
specie, thermodynamics, transport
products
specie, thermodynamics, transport

For the reactants, the molWeight coeff is equal to 29.4649, which corresponds to a 4% propane 96% air mixture, equivalence ratio of 1.

On the other hand, I found another type of directory, in which the following can be found:

CASE 2

fuel
specie, thermodynamics, transport
oxidant
specie, thermodynamics, transport
reactants
specie, thermodynamics, transport
products
specie, thermodynamics, transport
burntProducts
specie, thermodynamics, transport


For the reactants, the molWeight coeff is now 29.48 (4.1% propane 95.9% air). This is quite similar, but I must say that the results I obtain with the Pitz and Daily case are different in term of temperature for these two cases.

In the first one, the temperature (ER=1) is about 2300K
In the second one, same conditions, 1700K.

In both cases anyway, changing the equivalence ratio in the combustionProperties directory doesn't seem to affect the maximum temperature of the flow, but the recirculation length. (Someone had the same issue?)

I'm starting to think that the parameter "equivalence ratio" in combustion properties is only here to compute the GuldersCoeffs of the mixture air+fuel, and not the thermodynamic properties of this mixture. Indeed, I don't see how OpenFoam could calculate the Cp of the mixture if the only thing I give in thermophysicalProperties is the reactants and products thermo coeff for a specified equivalence ratio, as seen in the case 1. Again, I suspect I'm totally wrong on this, and blind regarding this matter, so if you get more info, please help me :)


I would be really interested in finding more about this solver (where is the temperature calculated exactly for example?), and in the different directories in general.


Best,

Remir

Hi, have you solved this problem? If as you mentioned to change the thermoproperties can is to change the equivalence ratio, then the EQ in 'combustionproperties' should be set according to thermoproperties?

remir March 19, 2015 09:38

Hi,

I assume I was right on this, you should indeed set the equivalence ratio to match your thermo properties, and vice versa.

It would be good to hear it from someone more experienced than me, though :p

Purushottam More October 23, 2015 01:52

zimont model for mixture
 
HI,
I am a newer in premixed combustion. When I use the FLUENT to modeling, I am confusing about the premixed combustion using Zimout model in FLUENT. I can't find where can I specify the mixture(methane-air) equivalence ratio or about the mixture materials.
Anyone knows how to solve it ? Please help me. Thanks in advance! This question is confusing me several days!
Best regards!


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