Maximum Temperature limited

malfrienz · July 11, 2013, 22:27

Hi all,
I'm conducting an analysis on a combustor. I first started the run with no reaction and the converged properly. After i turn on the reaction (combustion using std. eddy break up model in gaseous phase), the energy residual increases and the zone where reaction is said to take place shoots and is limited to the max allowable temperature.
So, I want to know, could it be because of the mesh (i had no problem when ran without chemical reactions) or is it just not converged yet? Also is there anyway to improve the convergence?
(I tried playing with the under relaxation factor: no use).

Thanks.

siara817 · July 12, 2013, 04:41

Are you waiting until it gets converged very well?
Have you tried iterations by first order and then change to second order?

malfrienz · July 15, 2013, 01:32

Yes first started with first order, and once it converged I switched to second order and once the second order converged, i turned on the reaction.

I actually have an equation, for which i converted toluene into another heavy compound (C20H18O10). So what i suspect is that, the temperature shoot up might me because of the difference in properties like heat of formation, specific heat. But i am not able to change the heat of formation for the species.

is there anyway to change the heat of formation?

siara817 · July 15, 2013, 07:57

I do not know about the formation heat. But, have you considered the air as an ideal gas?

July 11, 2013, 22:27	Maximum Temperature limited	#1
malfrienz New Member malu Join Date: Jun 2013 Posts: 8 Rep Power: 13	Hi all, I'm conducting an analysis on a combustor. I first started the run with no reaction and the converged properly. After i turn on the reaction (combustion using std. eddy break up model in gaseous phase), the energy residual increases and the zone where reaction is said to take place shoots and is limited to the max allowable temperature. So, I want to know, could it be because of the mesh (i had no problem when ran without chemical reactions) or is it just not converged yet? Also is there anyway to improve the convergence? (I tried playing with the under relaxation factor: no use). Thanks.

July 12, 2013, 04:41		#2
siara817 Senior Member siamak rahimi ardkapan Join Date: Jul 2010 Location: Copenhagen, Denmark Posts: 220 Rep Power: 18	Are you waiting until it gets converged very well? Have you tried iterations by first order and then change to second order? __________________ Good luck Siamak

July 15, 2013, 07:57		#4
siara817 Senior Member siamak rahimi ardkapan Join Date: Jul 2010 Location: Copenhagen, Denmark Posts: 220 Rep Power: 18	I do not know about the formation heat. But, have you considered the air as an ideal gas? __________________ Good luck Siamak

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July 15, 2013, 01:32		#3
malfrienz New Member malu Join Date: Jun 2013 Posts: 8 Rep Power: 13	Yes first started with first order, and once it converged I switched to second order and once the second order converged, i turned on the reaction. I actually have an equation, for which i converted toluene into another heavy compound (C20H18O10). So what i suspect is that, the temperature shoot up might me because of the difference in properties like heat of formation, specific heat. But i am not able to change the heat of formation for the species. is there anyway to change the heat of formation?