[lucchini]

Hi Atsushi,

coldEngineFoam can be used for cold flow simulations without combustion.

For all people interested in internal combustion engine simulations in OpenFOAM, please have a look to the web-site www.openfoamworkshop.org, where you can find some more informations.

Bye

Tommaso

Thank you, Tommaso!

Atsushi

Dear all,

I want to simulate HCCI/PCCI engine.
What case is suitable for modeling?

I want to simulate...

1)Fuel and air are pre-mixed
2)No ignition, no injection.
3)The model shape is simple cylinder.
4)calculate from -180deg. to 180deg.
5)Chemistry ON

Any help will be welcome.
Thank you.

Atsushi

Hello all,

I am trying to run a test case using Xifoam but am confused with the different parameters such as Xi,Su...Could anybody post a reference to XiFoam.
There has been a link given in previous posts but it does not work.
Eagerly waiting for a reply...

Thanks
Mayank.

[david_h]

Mayank,

The following two articles are available on citeseer:

H.G. Weller, 1993, The Development of a New Flame Area Combustion Model Using Conditional Averaging, Thermo-Fluids Section Report TF/9307

H.G. Weller, G. Tabor, A.D. Gosman, 1998, Application of a Flame-Wrinkling LES Combustion Model to a Turbulent Mixing Layer

C. Fureby, has also authored and co-authored several articles in the last few years in
Combustion and Flame, the Proceeding of
the Combustion Institute and the AIAA

Dave

[grtabor]

Mayank, Dave,

You might also be interested in

"Large Eddy Simulation of Premixed Turbulent Combustion using Xi Flame Surface Wrinkling Model", G.Tabor and H.G.Weller; Flow Turbulence and Combustion 72#1 pp.1-27 (2004)

Gavin

[tsencic]

How is it possible that the O2 concentration is increasing after the end of the combustion?

I am using dieselEngineFoam, with the standard, simple CHEM.INP:
ELEMENTS
H O C N AR
END
SPECIE
C7H16 O2 N2 CO2 H2O
END
REACTIONS
C7H16 + 11O2 => 7CO2 + 8H2O 5.00E+8 0.0 15780.0! 1
FORD / C7H16 0.25 /
FORD / O2 1.5 /
END

I output the O2 concentration with
<< sum(Y[1]*mesh.V())/sum(mesh.V()) << tab

So there is no backword reaction specified, but after the end of combustion, from CA 60 to 180 the O2 concentration rises from 0.133 to 0.1372.
Tomislav

[niklas]

maybe because Y goes up because rho is decrease due to higher temperature.

Y is massfraction, not molefraction, replace volume with mass.

Hi!!

the dieselSpray class has a liquid length penetration function that we can use.

dieselSpray.liquidPenetration(prc)

if there are multi holes injection or split injection , Can I use this function?

regards.

hello!

I simulate spray using dieselFoam.

I'm assuming split injection.and I want to check a value of spray penetration.

dieselSpray.liquidPenetration(0,1.0)
....first injection
dieselSpray.liquidPenetration(1,1.0)
....second injection

I got the same penetration value of first and second injection.

What wrong ? How to use liquidPenetrationFunction?

Please teach me. someone help!

thanks.

[nsp82]

Hello,

I have simulated a couple of cases using enginefoam with default combustion settings. But the p-theta data suggests that the initial rate of combustion is extremely low. Varying the start of ignition point has also not changed the results by much. Ofcourse, i am using a totally different (and bigger) mesh for my computations.
here is my p-theta sample.

http://enginesei.blogspot.com/2007/1...amp-theta.html

Can someone tell me how to increase the rate of combustion in enginefoam?

[mabinty]

Hi!

I am actually trying the Xoodles for a combustion (fire) in a simple 2D geometry but I have a problem to understand the parameter b. I read the comments in this forum (I also get a negative b and a combustion progress greater 100%). b=1 means "unburnt", b=0 "completely burnt"; but what is burnt/unburnt? what happens in between and why must b have unity as initial value in the domain? Does b=1 as initial value means that the whole domain is filled with fuel?

Thanx in advance for any comment!!
Mabinty

[grtabor]

XiFoam and Xoodles are premixed combustion codes, where a mixture of fuel and oxidiser burns to produce combustion products. We have an indicator function b which takes the value 1 where the gas is unburnt, 0 where it is burnt; the assumption is that the rection is effectively instantaneous, so the value jumps from 1 to 0 at the flame front. b=1 wuld give the whole domain filled with fuel and oxidiser. However when you perform a simulation you are not computing b but a filtered/averaged quantity, btilde. The filtering process smooths out the transition somewhat - you can show this mathematically - and the numerics disperses it a bit further. Hence the values between 0 and 1 don't really mean anything physical; they are just a function of the numerics and turbulence modelling. However this does make the problem _soluble_ as sudden jumps are not very easy to compute.

Further details here (if I can blow my own trumpet): Tabor, G.R. and Weller, H.G. (2004): Large Eddy Simulation of Premixed Turbulent Combustion using Xi Flame Surface Wrinkling Model, Flow, Turbulence and Combustion, 72#1, pp 1 - 27

Gavin

[mabinty]

Thank you Gavin!

As I still have some questions concerning the b-Xi model I ll try to get the mentioned article.

But still, why does Xoodles demand b=1 for the initial field:

--> FOAM FATAL ERROR : Mass fraction for single component mixture must be unity
Please correct field: b (Ydefault)

It doesn t seem realistic to me to have a domain filled with fuel and oxidiser when I want to simulate a simple combustion (fire) inside a room for example. With b=1 in the whole domain at t=0s of course I get something like an explosion when ignition occurs.

>>XiFoam and Xoodles are premixed combustion codes, where a mixture of fuel and oxidiser burns to produce combustion products.<<

As always a mixture of fuel and oxidiser is introduced to the domain, is it possible to extinct the fire (e.g. closed domain without outlet, where after a certain time the air-O2 is used)?

Furthermore, I tried to look up the code to see if radiation is treated by Xoodles. But I couldn t find something; the energy transport equation seems not to have a source term taking radiation into account. Does Xoodles include radiation? If yes, how?

Thanx in advance!
Mabinty

[mabinty]

No comments??

Maybe on this:

Now I extended my 2D geometry (based on pitzDaily), which worked somehow, to 3D. The problem now is, that every time I enable an ignition Foam gives me a floating point error (see below), always after the first time step. If I switch the ignition off, the calculation runs to the end. I checked the discussion forum for that kind of error, and also tried to adjust different parameters like the time step deltaT, boundary conditions, ignition parameters, flame speed correlation, SuModel (even though I honestly don t know what the latter two mean) and I refined the mesh; but every time I get the same error. Can somebody give me a hint please?

I thank you for any advice!
Mabinty

************************************************** ********

Starting time loop

Time = 0.005

Courant Number mean: 0 max: 0.1
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG: Solving for k, Initial residual = 1, Final residual = 4.18177e-07, No Iterations 1
bounding k, min: -6.63991e-11 max: 9.52645e-07 average: 1.3608e-08
DILUPBiCG: Solving for Ux, Initial residual = 1, Final residual = 8.27731e-07, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 1, Final residual = 1.76743e-08, No Iterations 1
DILUPBiCG: Solving for Uz, Initial residual = 1, Final residual = 9.01432e-07, No Iterations 1
Max St-Courant Number = 0.0972901
Igniting cell 5205 state : 1 1 0.135 1e-15
DILUPBiCG: Solving for b, Initial residual = 1, Final residual = 1.15317e-06, No Iterations 1
min(b) = 0.913381
#0 Foam::error::printStack(Foam:stream&) in "/home/E202/aa/OpenFOAM/OpenFOAM-1.4.1/lib/linuxGccDPOpt/libOpenFOAM.so"
#1 Foam::sigFpe::sigFpeHandler(int) in "/home/E202/aa/OpenFOAM/OpenFOAM-1.4.1/lib/linuxGccDPOpt/libOpenFOAM.so"
#2 Uninterpreted: [0x110420]
#3 Foam::divide(Foam::Field<double>&, Foam::UList<double> const&, Foam::UList<double> const&) in "/home/E202/aa/OpenFOAM/OpenFOAM-1.4.1/lib/linuxGccDPOpt/libOpenFOAM.so"
#4 void Foam::divide<foam::fvpatchfield,>(Foam::GeometricF ield<double,>&, Foam::GeometricField<double,> const&, Foam::GeometricField<double,> const&) in "/home/E202/aa/OpenFOAM/OpenFOAM-1.4.1/applications/bin/linuxGccDPOpt/Xoodles"
#5 Foam::tmp<foam::geometricfield<double,> > Foam::operator/<foam::fvpatchfield,>(Foam::tmp<foam::geometricfie ld<double,> > const&, Foam::tmp<foam::geometricfield<double,> > const&) in "/home/E202/aa/OpenFOAM/OpenFOAM-1.4.1/applications/bin/linuxGccDPOpt/Xoodles"
#6 main in "/home/E202/aa/OpenFOAM/OpenFOAM-1.4.1/applications/bin/linuxGccDPOpt/Xoodles"
#7 __libc_start_main in "/lib/libc.so.6"
#8 Foam::regIOobject::readIfModified() in "/home/E202/aa/OpenFOAM/OpenFOAM-1.4.1/applications/bin/linuxGccDPOpt/Xoodles"
Floating point exception

[david_h]

Mabinty,

I also have not seen anything in the Xoodles source code to indicate that the solver includes a radiation model.

As for your instabilities, have you tried changing the "ignitionSite" parameters ? For example increasing the duration and/or the diameter.

Dave

[mabinty]

Dave,

>> I also have not seen anything in the Xoodles source code to indicate that the solver includes a radiation model.

Is there any solver in OF treating radiation?

>> As for your instabilities, have you tried changing the "ignitionSite" parameters ? For example increasing the duration and/or the diameter.

Yes, i did; specially the variation of ignition start showed me that it s the ignition causing the problem. The error occurs every first time step after the ignition start (e.g. start=1s, with deltaT=0.005, does the error come at Time=1.005s). Honestly I have no idea at what to look again ...

Mabinty

[mabinty]

Hi!

Finally I was not able to run my case with an ignition. So I tried to provoque a self-ignition of the fuel by increasing the fuelInlet temperature to 900 K (self-ignition temperature of propane = 705 K); but the results do not show a combustion as b remains 1 during the whole simulation. Only the flow of a hot gas into a cold domain can be observed. What am I doing wrong here?

I appreciate every comment! Thanks in advance,
Mabinty

[tavasoly]

relaxation factors in xifoam not exist. according the user guide it not needed for unsteady solver. is it true? in fluent relaxation is used for unsteady.

[tavasoly]

Hi everybody.
I model simple bunsen falme with pilot by xifoam solver of openfoam 1.4.1. but tempreture in some cell (in premixed core) is lower than 300k and finaly it aborted by out of janafthermo error.
I do anything such as low curant number(co=0.1) , finner mesh, chaneg tolerance, increese piso corection, channg discretization scheme,... but is not benefit and abort by that error.
Can someone help me?
if anyone havw a case by this solver please send me.
Thanks a lot.