Oxydant temperature with combustion module

[arti]

Hello,
I'm using "Code_Saturne version 8.0.2-patch-0062aaaf8".

The question concerns the gas combustion module, an infinitely rapid chemical diffusion flame.
In my case, I have one gas inlet and two Oxydant inlets.
The two Oxydant inlets have different temperatures: inlet_air_1 = 400 K and inlet_air_2 = 600 K.
In the GUI, it's not possible to define two different temperatures.

I tried:

- defining a volume zone in the inlet_air_1 pipe and applying a thermal source term to this zone. The thermal source is enthalpy (temperature not available). The calculation can be run. By viewing the results in Paravis, I can see the enthalpy production, but the air temperature in the pipe doesn't increase. The enthalpy source term does not affect the flow temperature.
I tried the same approach with the standard Eulerian single-phase module, and it works (enthalpy and temperature are linked).

- Modified the setup.xml file without success.

Questions:
- Is it possible to define two different temperatures for the Oxydant ?
- If so, how? (Perhaps it's possible in the cs_user_boundary_conditions-gas_3ptchem.f90 file?, but my first attemps are unsuccessful )

Thanks!

[Yvan Fournier]

Hello,

Looking at the code, it seems that it is only possible to define multiple temperatures for premixed flames (Libby-Williams and EBU). For 3-point chemistry, the hinfue value is global to the model (which seems to be an unnecessary limitation, probably due to the initial coding rather that a real reason, bu I need to check with the combustion specialists).

For that model, temperature should be computed from enthalpy, so it is surprising that it does not increase also, though It may be useful to check the code for this.

Best regards,

Yvan

[arti]

Hello,

Thank you Yvan. I am interested by the answer of the combustion specialistes.

In attached file the case with thermal source. It is possible that I did a mistake with the use of thermal source and enthalpy ...
The model is only for testing. The real case have very more complexe 3D.

Thanks !

[arti]

Hello,
Does anyone have any ideas why the thermal source isn't working?
316 downloads. Someone has probably tried running the case...
Thanks very much.

[Yvan Fournier]

Hello,

I ran your case, and happened on a crash related to CoolProp usage, which was incompatible with an enthalpy-based thermal model.

I fixed the issue in the master, v9.0, and v8.0 branches, but do not recommend using a variable viscosity with combustion models, as I am not sure this is handled correctly (though it probably only makes a minor difference).

I a surprised that it ran in you case though.

Also, I am not sure I see the effect of your source term, but both temperature and enthalpy seem non-constant, so things would seem OK. Running it under a debugger, it is applied. But yous source term is 1e6 watts/m3, for a zone with volume 0.00049872, so that would add about 500 watts total, with a velocity in the 10m/s range for a domain of length 0.5. If I am not mistaken, it means you have about 20 flow passes in 1 second, so about 500/20 = 25 joules due to the source term in the domain at a given time.

Best regards,

Yvan