problem in combustion-eddy dissipation model?

sooraj546 · September 24, 2018, 03:07

I have done a very simple combustion of a fuel mixture using the following CH4, O2, H2, H2O, CO, CO2, N2 and C2H6 as the fuel+ air with 21% o2.

I have calculated the amount of o2 required for complete combustion (above fuel mixture composition given so calculated accordingly) and supplied it, so temperature and every thing is coming fine but when excess amount of O2 is supplied the the temperature increases further consuming all the O2 eg if i supply 20 % excess o2 it should reflect in exhaust unconsumed rt but its not happening, rather a huge temperature increase is happening compared to the stoichiometric one.

Kindly help me out guys , why is this happening ???

THANKS A LOT IN ADVANCE........

biond8 · September 28, 2018, 12:38

On the guide You can read the mass fraction is set to 0.01 by fluent default, so the ignition starts before!

sooraj546 · September 29, 2018, 00:40

Thanks a lot for that reply
but my major problem is even though I am supplying oxygen above it’s stoichiometrically required amount for complete combustion , still all the excess oxygen is some how consumed and the temp is increasing drastically as well . O2 Is completely absent in exhaust.
Why is it so ...?
Secondly, if I adjust the mass fraction at exhaust to be the excess amount of o2 supplied ......will that do fine but how to do it..... I have already tried defining the mass fraction of o2 at the outlet in boundary conditions section but no use.........
What to guys?
KINDLY HELP ME OUT..... thanks for ur help in advance

September 24, 2018, 03:07	problem in combustion-eddy dissipation model?	#1
sooraj546 Member Join Date: Apr 2017 Location: india Posts: 96 Rep Power: 9	I have done a very simple combustion of a fuel mixture using the following CH4, O2, H2, H2O, CO, CO2, N2 and C2H6 as the fuel+ air with 21% o2. I have calculated the amount of o2 required for complete combustion (above fuel mixture composition given so calculated accordingly) and supplied it, so temperature and every thing is coming fine but when excess amount of O2 is supplied the the temperature increases further consuming all the O2 eg if i supply 20 % excess o2 it should reflect in exhaust unconsumed rt but its not happening, rather a huge temperature increase is happening compared to the stoichiometric one. Kindly help me out guys , why is this happening ??? THANKS A LOT IN ADVANCE........

September 28, 2018, 12:38	problem in combustion-eddy dissipation model?	#2
biond8 New Member Laura Join Date: Jul 2018 Posts: 14 Rep Power: 7	On the guide You can read the mass fraction is set to 0.01 by fluent default, so the ignition starts before!

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September 29, 2018, 00:40		#3
sooraj546 Member Join Date: Apr 2017 Location: india Posts: 96 Rep Power: 9	Thanks a lot for that reply but my major problem is even though I am supplying oxygen above it’s stoichiometrically required amount for complete combustion , still all the excess oxygen is some how consumed and the temp is increasing drastically as well . O2 Is completely absent in exhaust. Why is it so ...? Secondly, if I adjust the mass fraction at exhaust to be the excess amount of o2 supplied ......will that do fine but how to do it..... I have already tried defining the mass fraction of o2 at the outlet in boundary conditions section but no use......... What to guys? KINDLY HELP ME OUT..... thanks for ur help in advance