[Howard]

Originally Posted by wenxu

Hi,Howar,

That's not difficult to simulate gas mixture combustion with flameletFoam. If you want use SLF, then you can keep combustion model not changed. Just generate a new flamelet library with your gas mixtures instead of CH4 with the released version. Flamelet equations can be solved with cantera which in the released version or FlameMaster.

regards,
wenxu

Sorry, what is SLF?

[jsh331]

Originally Posted by wenxu

Now, i know how to manipulate multi-step reactions. But as far as i know, there is no multi-step combustion models built in OF.

1. laminar
2. PaSR---derived from laminar, can be used in turbulence.
3. diffusion,FSD,infinitelyFastChemistry, these three all derived from singleStepCombustion

If i want to implement muti-step reaction (combustion model which not only consider chemistry time but also turbulence mixing time), what should i derived the class? That's mean which class should i derived from?
Now i have compiled the EBU model succeed and i design i case to use this model. (i almost substitute the EBU model for the chemistry class. that's means when laminar calss calculate the reaction Rate R(Yi), then it will use the new class EBU to calculate the R(Yi). ) ANY ideas can give me? Thank you!!!!



best Regards,
wen

Hi Wen
Why do you say that Laminar and PaSR combustion models are not for multi-step combustion? Actually I have a problem simulating constant volume combustion using reactingFoam. My geometry is a box with ignition at the center and a 4 step mechanism of CH4 & air is implemented. It's filled with CH4 and air initially. Turbulence model is k-epsilon and I'm testing laminar and PaSR combustion model. It turns out that laminar works pretty good but PaSR doesn't work as what I expect. So could you pls help me figure out my problem?

Sihan

[flowAlways]

Hi Sehan,
You are correct, infact the Chalmers PaSR model is very similar to the successful EDC approach by Magnussen. It takes into account both the turbulent time scale and the chemical time scale while determining the reaction rate. The chemical timescale is determined by solving the reaction system’s ODEs fully coupled, and finding the characteristic time for that system. So it is meant to take into account a multi-step reaction mechanism.
You can find more about PaSR here
http://www.tfd.chalmers.se/~valeri/book-chapt7.pdf
http://powerlab.fsb.hr/ped/kturbo/op...olmPhD2008.pdf
http://web.ist.utl.pt/jose.neves.rod...2011-FINAL.pdf

In the PaSR model the reaction rate is determined as
reactionRate_PaSR = kappa*reactionRate_laminar
kappa ~ 1 when t_chemical >> t_mix so your results with laminar and PaSR will be similar only when the rate is kinetics controlled and not mixing controlled(that is when the flow is laminar and reactions are slow).

what is your reaction mechanism? Can you maybe send your case to me ?

[jsh331]

Originally Posted by flowAlways

Hi Sehan,
You are correct, infact the Chalmers PaSR model is very similar to the successful EDC approach by Magnussen. It takes into account both the turbulent time scale and the chemical time scale while determining the reaction rate. The chemical timescale is determined by solving the reaction system’s ODEs fully coupled, and finding the characteristic time for that system. So it is meant to take into account a multi-step reaction mechanism.
You can find more about PaSR here
http://www.tfd.chalmers.se/~valeri/book-chapt7.pdf
http://powerlab.fsb.hr/ped/kturbo/op...olmPhD2008.pdf
http://web.ist.utl.pt/jose.neves.rod...2011-FINAL.pdf

In the PaSR model the reaction rate is determined as
reactionRate_PaSR = kappa*reactionRate_laminar
kappa ~ 1 when t_chemical >> t_mix so your results with laminar and PaSR will be similar only when the rate is kinetics controlled and not mixing controlled(that is when the flow is laminar and reactions are slow).

what is your reaction mechanism? Can you maybe send your case to me ?

Hello Ali,

Thanks for your explanation. My problem is I keep adding energy, but the reaction rate is too small when I use PaSR model. Pls find my case in the attachment.

--Sihan

[Howard]

Originally Posted by wenxu

Now, i know how to manipulate multi-step reactions. But as far as i know, there is no multi-step combustion models built in OF.

1. laminar
2. PaSR---derived from laminar, can be used in turbulence.
3. diffusion,FSD,infinitelyFastChemistry, these three all derived from singleStepCombustion

If i want to implement muti-step reaction (combustion model which not only consider chemistry time but also turbulence mixing time), what should i derived the class? That's mean which class should i derived from?
Now i have compiled the EBU model succeed and i design i case to use this model. (i almost substitute the EBU model for the chemistry class. that's means when laminar calss calculate the reaction Rate R(Yi), then it will use the new class EBU to calculate the R(Yi). ) ANY ideas can give me? Thank you!!!!



best Regards,
wen

Hello, Friends. I am now trying to do combustion simulation in OpenFOAM, since I need to use multistep mechanism, I would like to ask which solver I can use? You mentioned before that this is no model for multistep mechanism? Thank you!

[Howard]

Originally Posted by jsh331

Hi Wen
Why do you say that Laminar and PaSR combustion models are not for multi-step combustion? Actually I have a problem simulating constant volume combustion using reactingFoam. My geometry is a box with ignition at the center and a 4 step mechanism of CH4 & air is implemented. It's filled with CH4 and air initially. Turbulence model is k-epsilon and I'm testing laminar and PaSR combustion model. It turns out that laminar works pretty good but PaSR doesn't work as what I expect. So could you pls help me figure out my problem?

Sihan

Hi, Sihan Jin. I also want to use multistep mechanism. I tried the PaSR model but it doesn't work. So I would like to ask how you solve your problem? Thank you!

[wenxu]

ReactingFoam maybe the choice for non-premixed flame. Just add reactions in the reaction dictionary.

Regards,
Wen

[Tom123]

Hi Shian,

May you upload your 4-step reaction mechanism of CH4? I try to find it. thank you.

Tom