[vedravi]

Hello all,
I have been trying to work out with a methane+air one step chemistry reaction premixed model along a 2D pipe model. Can someone tell me how can we input in FLUENT
(i) the concentrations (%) of species i.e methane and oxygen(air), that are to be ignited using patching method
(ii) laminar flow conditions

Thank you

[sahm]

If I understand your question right, you want to input the concentrations,
When you're defining boundary conditions, there's one tab for species( for example velocity inlet boundary) that you define the mass ratios.
for laminar modeling, in define/viscosity you can do it.
You can find these in fluents manual, there's a lot of tutorials and manuals for fluent online.

[vedravi]

Hi Sahm,
Well I tried that by clicking the species tab in B.C's but for a premixed case I see that there is only "progress variable" available i.e c=0(unburnt) or c=1(burnt) and is not the same option as seen in species transport model wherein we have the option of giving the concentrations of species.

And secondly by going in the following way
define->viscous->laminar model
the FLUENT is not allowing for any transport model like combustion in my case. I see that all those options remain de-activated

Please help me with these issues
Thank you
-Ravi

[sahm]

In that case you're using the premixed combustion model which uses the progress variable to calculate where the combustion is happening. Temperature is also calculated based on this model. in that case you should define your species somewhere else( I don't exactly remember). Fluent only does this model with turbulent cases.
You should change your model to species transport model with volumetric reactions ( finite rate). Then you can define your combustion and viscosity in laminar model. Also you can define your species in boundary and initial condition. This model also works with non-premixed cases.(fluent manual section 11.2)

I`m working with laminar combustion right now, but I have a problem that nearly all of my flames are unstable and they move out of the domain. Do what you're trying to do, but please keep me updated .

[vedravi]

Well how can a laminar premixed model analyzed in FLUENT using 'specie-transport' MODEL when I see that the k and epsilon still remain in the initialization parameters?

[pbaranidaran]

Hi Ravi,

I am working on a very similar problem of a premixed combustion of methane and air. Have you made any progress?? Please help me on this. Thanks a ton.

[vedravi]

Well. I tried to use species-transport laminar viscous model and performed the planned task at that time. I am not sure of what help you are specifically looking for.

[pbaranidaran]

I have been trying to work with flame propagation in a premixed mixture of methane+air( stoichiometric ratio) in a closed chamber with intrusions. If i use species transport model with laminar finite rate, k-Eps I am getting results which are physically not sensible, like multiple flame fronts and temperature exceeding 7000 K etc. I don't know how to improve my results.

I am unable to use Premixed combustion model because I don't know how to give the concentrations in the chamber and how to give the value for C as the reaction mighnot be complete once it reaches the end of the chamber.

I hope I made sense.

[vedravi]

I am not sure of what is the reason for that. You may refer to the user guide to get any clue.
http://hpce.iitm.ac.in/website/Manua...ug/node692.htm
And try reducing the 'patched' temperature and other attempts (initially patching and once flame is ignited, remove patching after running few iterations etc.) I used to try different ways when I was working on Fluent. But its been a while and currently do not have access to it.

[sanjeetlimbu]

Dear sir

I am trying to use laminar flow calculation in fluent for n-heptane fuel mixture...
When i select the laminar scheme.... error is shown...and the partially premixed is unselected.

Pl tell if i can do laminar for combustion inside a compressed piston stroke... as i am getting wrong pressure plot for 2-epsilon ... in compression stroke for my rapid compression stroke

[sanjeetlimbu]

Please reply if you know how to set the pdf mixture for laminar case

I tried doing the K-epsilon,Non-adiabatic species model for combustion the temperature at compression end is less than expected 766K it is just 550K.
For same mixture composition the experimental is 776K

[student101]

Originally Posted by pbaranidaran

I have been trying to work with flame propagation in a premixed mixture of methane+air( stoichiometric ratio) in a closed chamber with intrusions. If i use species transport model with laminar finite rate, k-Eps I am getting results which are physically not sensible, like multiple flame fronts and temperature exceeding 7000 K etc. I don't know how to improve my results.

I am unable to use Premixed combustion model because I don't know how to give the concentrations in the chamber and how to give the value for C as the reaction mighnot be complete once it reaches the end of the chamber.

I hope I made sense.

Hi. I know its been quite some time but can i have your e-mail address to ask several questions?I am working on the same problems with you.thank you in advance.