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-   -   Pre-mixed combustion- Laminar finite rate model (https://www.cfd-online.com/Forums/fluent/33312-pre-mixed-combustion-laminar-finite-rate-model.html)

 Shankar March 25, 2004 19:21

Pre-mixed combustion- Laminar finite rate model

Hello all,

I am dealing with pre-mixed combustion in a closed chamber.After defining the chemical mechanism and activating all the reactions, I have a small zone in the centre of the chamber where I patch the temperature to be above the ignition temperature(which is equivalent to an electric spark).

The reaction mechanism is defined based on the literature available for this particular mixture of fuel.

But I am not getting convergence. Is there anything wrong with the way I am starting the reactions? I have floating operating pressure for this kind of premixed combustion inside a closed chamber.The geometry is simple(cube) and so are the boundary conditions.

I couldnt find this paper in our library, does anybody have this: Westbrook, C.K. and Dryer F.L., (1981) "Simplified Reaction Mechanisms for the Oxidation of Hydrocarbon Fuels in Flames" CST, 27, pp.31-43

Thanks and Regards, Shankar.

 cg March 25, 2004 20:51

Re: Pre-mixed combustion- Laminar finite rate mode

Use the coupled solver :)

 Shankar March 25, 2004 23:55

Re: Pre-mixed combustion- Laminar finite rate mode

Hi CG,

I am using coupled solver only.

I think thats the default option in FLUENT?

:(

 zxaar March 26, 2004 05:22

Re: Pre-mixed combustion- Laminar finite rate mode

i don't think coupled is default option in fluent. check again.

 Shankar March 26, 2004 18:24

Re: Pre-mixed combustion- Laminar finite rate mode

Thanks to both of you, 'coupled' is not the default option in FLUENT, but it seems like if I use 'coupled', I cannot use floating operating pressure?

Shankar.

 zxaar March 29, 2004 06:18

Re: Pre-mixed combustion- Laminar finite rate mode

one more thing i do have the paper u mentioned but there is a problem, i am in portugal and i left the paper in india, i only have the appendix here in which reaction mechanism is given, if you want that i can scan that and send you

 Shankar March 29, 2004 15:19

Re: Pre-mixed combustion- Laminar finite rate mode

Hi Zxaar,

That would be awesome if you could e-mail it to me.

Thanks, Shankar.

 Shankar March 30, 2004 20:37

Re: Pre-mixed combustion- Laminar finite rate mode

Using the coupled solver did not solve the problem. I get the following error: 'couldnt allocate the fine level co-efficient matrix'. Any idea whats wrong?

Shankar.

 zxaar March 31, 2004 05:18

Re: Pre-mixed combustion- Laminar finite rate mode

i also do have the same experience, but to my surprize for the same case and same boundary conditions sometimes it works without complaining, i have found similar case with edc, i mean i have same grid same boundary conditions and same chem mech file, in one case it runs without a prob, in other it gives me some failure. i am not able to sort it out.

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