acetylene and o2 reaction not producing high temperature

Shamoon Jamshed · November 4, 2021, 13:33

Dear All enthusiasts

I am simulating a case of acetylene and O2. I am using Species transport model with k-epsilon model. I use the ideal gas for outer domain. The acety and O2 are entering at temperatures 288.15K while pressure as 2 and 5.8 atmosphere respectively. The mass flow inlets are 1.2e-4 kg/s for acetylene and 4e-5 kg/s for O2. I am following a paper who used EDMC which is available in species transport menu. So, when I start iterating, everything goes fine but when I see temperature, the temperature at the end of the torch rises to 2 degree only. Where am I doing wrong? please help.

Thanks

Shamoon Jamshed · November 5, 2021, 09:17

please reply , its a bit urgent

LoGaL · November 6, 2021, 09:51

Did you turn on a combustion model? You don’t mention it -.-

Shamoon Jamshed · November 6, 2021, 09:54

Of course I did, I used Species transport with Eddy dissipation concept model as a paper used it. And secondly I used Non-Premixed combustion. The second one diverged. I used Fuel c2h2 =1 and oxidizer =1 in the second one.

LoGaL · November 6, 2021, 12:48

For eddy dissipation model, are you patching the flame zone with combustion products to turn on the flame?

Shamoon Jamshed · November 6, 2021, 12:55

I did not get your point. How are we going to patch products? You mean in species transport? I have made a single zone modeling converging like nozzle geometry, then the outside air zone continued with the nozzle zone. Initially every thing is air which is modeled as ideal gas. Then mass flow inlets were specified for c2h2 and o2. Should I patch the torch region with products of combustion? I specified species in O2 inlet with O2 as 1. While in c2h2 inlet I specified species with c2h2 as 1. (in mole fraction)

Shamoon Jamshed · November 6, 2021, 12:59

please see the image for understanding

LoGaL · November 6, 2021, 13:32

Yes, once the flow without flame is reasonably converged, you patch the zone where the flame is supposed to be with some combustion products (so water and co2)
You see man, in reality you turn the flame on with a spark, in the CFD you do some other stuff to fire up everything.

Shamoon Jamshed · November 6, 2021, 14:13

thanks LoGaL, I do the thing and return back to you if problem persists. Thanks for your precious time

Shamoon Jamshed · November 14, 2021, 04:47

Dear Logal,

I am getting better results now with NPC model. The species transport model was predicting very low temperature (near 300K). However, the NPC model is not predicting correct heat flux (0.3 MW/m2). I am shring paper with you that I am following:

"*
*
Numerical Simulation of Oxy-Acetylene Testing Procedure of Ablative Materials for Re-Entry Space
Vehicles
F Marra, G Pulci, J Tirilló, C Bartuli and T Valente
2011 225: 32
Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials Design and Applications
DOI: 10.1177/14644207JMDA335
*
The online version of this article can be found at:
http://pil.sagepub.com/content/225/1/32
"
I hope you can help me in this regard.

November 4, 2021, 13:33	acetylene and o2 reaction not producing high temperature	#1
Shamoon Jamshed Senior Member Shamoon Jamshed Join Date: Apr 2009 Location: Karachi Posts: 381 Rep Power: 18	Dear All enthusiasts I am simulating a case of acetylene and O2. I am using Species transport model with k-epsilon model. I use the ideal gas for outer domain. The acety and O2 are entering at temperatures 288.15K while pressure as 2 and 5.8 atmosphere respectively. The mass flow inlets are 1.2e-4 kg/s for acetylene and 4e-5 kg/s for O2. I am following a paper who used EDMC which is available in species transport menu. So, when I start iterating, everything goes fine but when I see temperature, the temperature at the end of the torch rises to 2 degree only. Where am I doing wrong? please help. Thanks

November 5, 2021, 09:17		#2
Shamoon Jamshed Senior Member Shamoon Jamshed Join Date: Apr 2009 Location: Karachi Posts: 381 Rep Power: 18	please reply , its a bit urgent

November 6, 2021, 09:51		#3
LoGaL Senior Member Lorenzo Galieti Join Date: Mar 2018 Posts: 375 Rep Power: 12	Did you turn on a combustion model? You don’t mention it -.-

November 6, 2021, 09:54		#4
Shamoon Jamshed Senior Member Shamoon Jamshed Join Date: Apr 2009 Location: Karachi Posts: 381 Rep Power: 18	Of course I did, I used Species transport with Eddy dissipation concept model as a paper used it. And secondly I used Non-Premixed combustion. The second one diverged. I used Fuel c2h2 =1 and oxidizer =1 in the second one.

November 6, 2021, 12:48		#5
LoGaL Senior Member Lorenzo Galieti Join Date: Mar 2018 Posts: 375 Rep Power: 12	For eddy dissipation model, are you patching the flame zone with combustion products to turn on the flame?

November 6, 2021, 12:55		#6
Shamoon Jamshed Senior Member Shamoon Jamshed Join Date: Apr 2009 Location: Karachi Posts: 381 Rep Power: 18	I did not get your point. How are we going to patch products? You mean in species transport? I have made a single zone modeling converging like nozzle geometry, then the outside air zone continued with the nozzle zone. Initially every thing is air which is modeled as ideal gas. Then mass flow inlets were specified for c2h2 and o2. Should I patch the torch region with products of combustion? I specified species in O2 inlet with O2 as 1. While in c2h2 inlet I specified species with c2h2 as 1. (in mole fraction)

November 6, 2021, 13:32		#8
LoGaL Senior Member Lorenzo Galieti Join Date: Mar 2018 Posts: 375 Rep Power: 12	Yes, once the flow without flame is reasonably converged, you patch the zone where the flame is supposed to be with some combustion products (so water and co2) You see man, in reality you turn the flame on with a spark, in the CFD you do some other stuff to fire up everything.

November 6, 2021, 14:13		#9
Shamoon Jamshed Senior Member Shamoon Jamshed Join Date: Apr 2009 Location: Karachi Posts: 381 Rep Power: 18	thanks LoGaL, I do the thing and return back to you if problem persists. Thanks for your precious time

November 14, 2021, 04:47		#10
Shamoon Jamshed Senior Member Shamoon Jamshed Join Date: Apr 2009 Location: Karachi Posts: 381 Rep Power: 18	Dear Logal, I am getting better results now with NPC model. The species transport model was predicting very low temperature (near 300K). However, the NPC model is not predicting correct heat flux (0.3 MW/m2). I am shring paper with you that I am following: "* * Numerical Simulation of Oxy-Acetylene Testing Procedure of Ablative Materials for Re-Entry Space Vehicles F Marra, G Pulci, J Tirilló, C Bartuli and T Valente 2011 225: 32 Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials Design and Applications DOI: 10.1177/14644207JMDA335 * The online version of this article can be found at: http://pil.sagepub.com/content/225/1/32 " I hope you can help me in this regard.