Learning Forum

[Propanotriol]

Dear all,

I am trying to model a furnace where different reactants react with oxygen (combustion). The reactions are not at all complex. I am using a CHEMKIN mechanism:

ELEMENTS C O S H N

END

SPECIES

COS O2 CO2 SO2 H2S H2O C2H6S CO C4H8O S N2

END

REACTIONS

COS+1.5O2=CO2+SO2 1E6 0   0

H2S+1.5O2=H2O+SO2 1E6 0   0

C2H6S+4.5O2=2CO2+3H2O+SO2 1E6 0   0

CO+0.5O2=CO2 1E6 0   0

C4H8O+5.5O2=4CO2+4H2O 1E6 0   0

S+O2=SO2 1E6 0   0

END

Since I do not know the Ahrrenius coefficients for the kinetics, I decided to model the reactions as instantaneous and fast (0 activation energy and high value for A).

The thermodynamic database is correct and constructed from the "Third Millennium Ideal Gas and Condensed Phase Thermochemical Database for Combustion with Updates from Active Thermochemical Tables" by Burcat and Ruscic.

All the set-up is correct and as it should be. The simulation evolves correctly, no divergence at all and convergence of different controls such as mass conservation, energy etc. are also good.

HOWEVER, the reaction involving C2H6S and C4H8O do not work. This is, they are not consumed at all. And yes, there is enough oxygen in the system. I don't understand why all the other 4 mechanisms do work and the reactants are correctly consumed (inexistent at the outlet) while for these two, I recover exactly the same ammount that I introduce into the system.

[Rahul Kumar]

Hello,
Please make sure the stoic. coefficients and the rate exponents are defined right. These are the parameters that would affect the consumption of the species.

[Propanotriol]

Hello,

Since I do not have all the coefficients, I used the same for all the reactions, as


So, they are well defined and Fluent do import them correctly.
All the reactions work correctly, except reactions 3 and 5.

Thank you for the help.

[Rahul Kumar]

Can you try varying the values for 3 and 5?

[Propanotriol]

I did, I increased k several orders of magnitude for reaction 3 and 5 and still not working.