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Old   January 3, 2011, 04:11
Question Temperature is too high
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I've got alternateSteadyReactingFoam running on H2-O2 combustion case, but the temperature range is too high, which is 1600-7900K.
It can't be so high, anyone has any ideas?
Or something wrong with gasThermo file?
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Old   January 3, 2011, 07:43
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Hi,

To get proper advice please post more details about your test case setup. The problem that you are mentioning is quite common and can arise due to various issues.

There is no specific fix for this problem.
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Old   January 4, 2011, 05:41
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OK, thank you.
I'll give the content of gasThermo file


// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
(
// Name Mole Weight
// Janaf
// Sutherland
C C 1 12.0112
200 5000 1000
2.60209 -0.000178708 9.08704e-08 -1.14993e-11 3.31084e-16 85421.5 4.19518
2.49858 8.08578e-05 -2.6977e-07 3.04073e-10 -1.10665e-13 85458.8 4.75346
1.67212e-06 170.672
O2 O2 1 12.0112
200 5000 1000
2.60209 -0.000178708 9.08704e-08 -1.14993e-11 3.31084e-16 85421.5 4.19518
2.49858 8.08578e-05 -2.6977e-07 3.04073e-10 -1.10665e-13 85458.8 4.75346
1.67212e-06 170.672
CO2 CO2 1 12.0112
200 5000 1000
2.60209 -0.000178708 9.08704e-08 -1.14993e-11 3.31084e-16 85421.5 4.19518
2.49858 8.08578e-05 -2.6977e-07 3.04073e-10 -1.10665e-13 85458.8 4.75346
1.67212e-06 170.672
N2 N2 1 12.0112
200 5000 1000
2.60209 -0.000178708 9.08704e-08 -1.14993e-11 3.31084e-16 85421.5 4.19518
2.49858 8.08578e-05 -2.6977e-07 3.04073e-10 -1.10665e-13 85458.8 4.75346
1.67212e-06 170.672
)
// ************************************************** *********************** //

Sorry about that I copy and past those numbers 3 times, because I don't know how to get those right numbers.
From Janaf table? I guess?
And I wonder what those numbers mean, it's not the same as those NASA numbers.
And I wonder the temperature is too high because of those wrong numbers, Cantera seems to read those numbers to compute the data, eh?
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Old   January 5, 2011, 06:38
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Hi,

Yes OF reads these numbers only to compute data. But if you are using JANAF data then it has limits of 200 and 5000K and computation should give an error if these limits are exceeded.

You may get JANAF data for may species in a file locate in the tutorials in combustion folder. I think that file is in dieselFoam. Its called "them.dat", and it has data for many species.

See if this solves your problem. There are other ways also to get that error. One more thing, I have never used the Cantera library in OF and I think that there might be some bugs in it, so do go through other posts regarding the cantera and check if you have taken care of all the mentioned issues or not.
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Old   January 5, 2011, 07:48
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Hi, Nakul, things seems stranger this afternoon.
I found that if I changed those numbers in gasThermo file, but the temperature remained unchanged.
And I come to know that : it seems this file doesn't affect the actual calculation process, and it doesn't affect the result. I don't know if it's true.
Now I have a new idea, I run the H2_O2 combustion in cantera without OpenFoam in Win32 OS to check the cantera input file.
I downloaded JANAF table 3rd Edtion last night, but today I found those numbers can't meet with those numbers in example gasThermo file, anything wrong?
PS: Do you have a email address or something like MSN?
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Old   January 6, 2011, 08:58
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Now I give you the rar file of my example case, but you need cantera.
CTI file seems OK, but temperature is too high, any one can test it and tell me the temperature range.
Attached Files
File Type: zip firstSample.zip (56.5 KB, 22 views)
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Old   January 7, 2011, 05:33
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Hi KT,

I had a look at the case. Thehre seems to be an issue with AR I was not able to sort out. But in general. Start with an inert mixture inside the domain (to prevent an initial "explosion"). Lower the URF-factors.

In the case I send you I used H2O as inert specie and it looks reasonable. You have to look on more detail why AR does not work.

Markus
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File Type: gz temperature-too-high-second.tar.gz (11.5 KB, 16 views)
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Old   January 7, 2011, 06:44
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Thank you, markusrehm.
I'ii try it ASAP.
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Old   January 7, 2011, 06:50
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Hi Newkid,

I don't have cantera as you said so I haven't run your case. But looking at its setup I can only advice the following:
Which of the two species data that you have specified - one in gasThermo and other in h2o2.cti is being used by cantera library for calculations. These numbers should have some effect on your temperature as these are used to calculate Cp and Cv.

The first two values in this data,ie, 200 and 1000/5000 are the min and max temperature limits. They should be 200 and 5000 for JANAF data unlike those mentioned in "h2o2.cti". (Atleast I have always seen Tmin and Tmax to be 200 and 5000K in standard JANAF tables).

As for what Markus said I have never heard before that making AR an inert specie gives rise to some problems. I would appreciate if you could please elaborate. Because involvement of AR in the reaction mechanism itself would take into account the necessary suppression of explosion. If this is actually a problem what would you say about N2?

You may keep trying and should post any new development here.

My email id is nakulthemaster@gmail.com
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Old   January 7, 2011, 07:38
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Hi, nakul, thank you for your suggestions.
I tried to use h20 as inert specie, and temperature dropped down by 3k, but still around 4000K +.
Now I have an idea, who can give me something on H2-O2 combustion?
I wonder if those numbers have inner relationships that I don't care?
What does initial "explosion" mean?
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Old   January 7, 2011, 09:36
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By explosion I mean:

Imagine you put H2 and O2 in a closed hot container: It will immediately ignite and become very hot and expand rapidely. So be very careful with your initial conditions when you do combustion (simulation or even experiment ).

Have also a look at the general advice for steady state combustion I posted some time ago
Cantera: Help me understand this error

Markus
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Old   January 7, 2011, 23:07
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Markus, thank you!
I'll try it ASAP!
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Old   January 8, 2011, 05:50
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Hi NewKid,

You may find details of H2-O2 combustion in any standard textbook on combustion like the one by S.R Turns.

I have also simulated H2-O2 combustion but I used reactingFOAM only and the data given in therm.dat that I mentioned. The simulation ran OK without temperature going too high and combustion was occurring. But I haven't obtained final results as yet.

If you are able to solve this problem do mention the solution here.
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Old   January 8, 2011, 21:38
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OK, nakul, if I have this issue worked out, I'll give more details on it!
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Old   January 10, 2011, 08:36
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Hi, Markus, I have several questions as following:
1.I saw a warning message like this :The thermophysical properties of CANTERA are currently not converted to OpenFOAM. Instead the properties from "/OpenFOAM/OpenFOAM-1.5-dev/applications/solvers/AlternateChemistry/Steady/firstSample/constant/gasThermo" are used This can lead to errors if the data is inconsistent with the Cantera-data". Dose it mean that I must use gasThermo file as thermophysical properties input?(ThanK Nakul, I've found the right data!) If I don't use it or write wrong data to it, what will happen? And what do those NASA data in cti file mean? Are they the same thing?(They don't seem to agree with each other!)
2.In chemistryProperties file, there are severals parameters like:
Cmix CMix [0 0 0 0 0 0 0] 1.;"
steadyChemistryDeltaT 1e-1;
recalcMax 5;
YOvershootThreshold 1.001;
kappaScaleThres 0.1;
minAbsDeltaY 1e-3;
absDeltaYThres 0.1;
relDeltaYThres 0.5;
relDeltaYCalcThres 0.5;
kappaScaleDelta 0.25;"
What do they mean? It seems that YOvershootThreshold related to temperature directly.
3.In chemistryProperties file, there are "chemistrySolver" and "turbulentReaction" parameters, but when I switched them off, Cantera still solve chemistry, why? How can I switch chemistry off for real?
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Old   January 10, 2011, 10:08
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Hi,

1) That question was answered here:
Cantera

2) Have a look at the readChemistryProperties.H of the steady solver e.g. here:

http://openfoam-extend.svn.sourcefor...ryProperties.H

3) The parameters "chemistrySolver" and "turbulentReaction" are only read if the OF chemistry library is used. To Switch chemistry off you can turn back to OF chemitry and use the mentioned parameters or add your own switch in alternateSteadyReactingFoam.C:

...

# include "chemistry.H"
// Pressure-velocity SIMPLE corrector
{
# include "UEqn.H"
if (yourChemistrySwitch){
# include "YEqn.H"
}
# include "hEqn.H"
# include "pEqn.H"
}
...

Markus

Last edited by markusrehm; January 10, 2011 at 10:24.
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Old   January 11, 2011, 21:50
Smile Thank you markusrehm,but...
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Thank you markusrehm!I wonder if you can send me successful and complete

H2-O2 combustion case files. My email is swust_lt@sina.com.
Thanks!





Quote:
Originally Posted by markusrehm View Post
Hi,

1) That question was answered here:
Cantera

2) Have a look at the readChemistryProperties.H of the steady solver e.g. here:

http://openfoam-extend.svn.sourcefor...ryProperties.H

3) The parameters "chemistrySolver" and "turbulentReaction" are only read if the OF chemistry library is used. To Switch chemistry off you can turn back to OF chemitry and use the mentioned parameters or add your own switch in alternateSteadyReactingFoam.C:

...

# include "chemistry.H"
// Pressure-velocity SIMPLE corrector
{
# include "UEqn.H"
if (yourChemistrySwitch){
# include "YEqn.H"
}
# include "hEqn.H"
# include "pEqn.H"
}
...

Markus
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Old   January 12, 2011, 00:49
Default Something out of my understanding
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Something out of my understanding happened.
As I set H2 and O2 composition percentage higher, and Ar lower, the temperature drops down.
And I set H2 0.07, O2 0.555, Ar 0.375, the temperature become about 2200K.
Initial value is H2 0.009, O2 0.026, Ar 0.925, and what's the unit of those numbers?
I am a new guy to chemistry and combustion,who can tell me what's going on?
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Old   January 12, 2011, 04:46
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Hi LT,

does the case I sent you not converge?

The unit is mass fraction (kg_species/kg_gas).

You should thoroughly study some books about combustion because the topic and also the solvers are not straight forward.

I suggest

@book{poinsot2005theoretical,
title={{Theoretical and numerical combustion}},
author={Poinsot, T. and Veynante, D.},
isbn={1930217102},
year={2005},
publisher={RT Edwards, Inc.}
}

@book{kee2003chemically,
title={{Chemically reacting flow: theory and practice}},
author={Kee, R.J. and Coltrin, M.E. and Glarborg, P.},
isbn={0471261793},
year={2003},
publisher={John Wiley and Sons}
}

Markus
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Old   January 12, 2011, 08:05
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Thank you, markusrehm.
I'll read them.
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