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Pre-mixed combustion- Laminar finite rate model

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Old   March 25, 2004, 19:21
Default Pre-mixed combustion- Laminar finite rate model
  #1
Shankar
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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.

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Old   March 25, 2004, 20:51
Default Re: Pre-mixed combustion- Laminar finite rate mode
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cg
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Use the coupled solver
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Old   March 25, 2004, 23:55
Default Re: Pre-mixed combustion- Laminar finite rate mode
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Shankar
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Hi CG,

I am using coupled solver only.

I think thats the default option in FLUENT?

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Old   March 26, 2004, 05:22
Default Re: Pre-mixed combustion- Laminar finite rate mode
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zxaar
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i don't think coupled is default option in fluent. check again.
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Old   March 26, 2004, 18:24
Default Re: Pre-mixed combustion- Laminar finite rate mode
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Shankar
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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.
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Old   March 29, 2004, 06:18
Default Re: Pre-mixed combustion- Laminar finite rate mode
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zxaar
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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
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Old   March 29, 2004, 15:19
Default Re: Pre-mixed combustion- Laminar finite rate mode
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Shankar
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Hi Zxaar,

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

Thanks, Shankar.
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Old   March 30, 2004, 20:37
Default Re: Pre-mixed combustion- Laminar finite rate mode
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Shankar
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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.
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Old   March 31, 2004, 05:18
Default Re: Pre-mixed combustion- Laminar finite rate mode
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zxaar
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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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