Counter flow diffusion flame simulation using Fluent (Flame temperature too low)

upender · July 11, 2016, 04:57

I am trying to model a counter flow diffusion flame using ansys fluent with fuel/oxidiser as methane/air.
The problem is that the flame temperature(800 K) is much lower than what it should be(>1600 K).
I am using Non premixed combustion module with steady diffusion flamelet and adiabatic energy treatment since combustion is instantaneous process. I am using a standard 30 species chemkin reaction mechanism from standard mechanisms library.
My PDF table seems OK as The plots show a max temperature of 1800 K at a mean mixture fraction value of 0.1. The geometry is a simple cylinder with two inlets in the axial direction and outlet in radial direction(image).
The Dia of two inlets is 60mm and the gap=10mm.
Can any body explain why am I not getting the desired temperature? I would be happy to provide any further information if required.

https://postimg.org/image/on8od81jb/

diamondx · July 11, 2016, 07:05

what about radiation. Have you activated it ?
How do you ignite your flame. How about solving turbulence and flow equation first, then activate PDF for ignition...

upender · July 11, 2016, 07:24

Hi Ali,
Thanks for the reply. No, I have not activated the heat transfer and radiation modules. I am keeping it strictly adiabatic(Am I wrong?). I am using a 30 species chemkin mechanism to generate the flamelets. Then I generate the PDF table. Then I go for the boundary conditions. The mean mixture fraction for fuel inlet is 1 and the oxidizer inlet is 0. The velocities at both ends is 0.1m/s. I initialize the solution through all domains and run it for 200 iterations. It converges on 80th step.
If you think that something is wrong in my approach, please point me in the right direction. I have never used the combustion modules before.

Regards

diamondx · July 11, 2016, 20:00

Nothing looks, are you comparing it with experimental data ??

July 11, 2016, 04:57	Counter flow diffusion flame simulation using Fluent (Flame temperature too low)	#1
upender New Member upender singh Join Date: Jul 2014 Location: new delhi, india Posts: 11 Rep Power: 12	I am trying to model a counter flow diffusion flame using ansys fluent with fuel/oxidiser as methane/air. The problem is that the flame temperature(800 K) is much lower than what it should be(>1600 K). I am using Non premixed combustion module with steady diffusion flamelet and adiabatic energy treatment since combustion is instantaneous process. I am using a standard 30 species chemkin reaction mechanism from standard mechanisms library. My PDF table seems OK as The plots show a max temperature of 1800 K at a mean mixture fraction value of 0.1. The geometry is a simple cylinder with two inlets in the axial direction and outlet in radial direction(image). The Dia of two inlets is 60mm and the gap=10mm. Can any body explain why am I not getting the desired temperature? I would be happy to provide any further information if required. https://postimg.org/image/on8od81jb/

July 11, 2016, 07:05		#2
diamondx Super Moderator Ghazlani M. Ali Join Date: May 2011 Location: Tokyo, Japan Posts: 1,385 Blog Entries: 23 Rep Power: 29	what about radiation. Have you activated it ? How do you ignite your flame. How about solving turbulence and flow equation first, then activate PDF for ignition... __________________ Regards, New to ICEM CFD, try this document --> https://goo.gl/KAOIwm Ali

July 11, 2016, 20:00		#4
diamondx Super Moderator Ghazlani M. Ali Join Date: May 2011 Location: Tokyo, Japan Posts: 1,385 Blog Entries: 23 Rep Power: 29	Nothing looks, are you comparing it with experimental data ?? __________________ Regards, New to ICEM CFD, try this document --> https://goo.gl/KAOIwm Ali

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July 11, 2016, 07:24		#3
upender New Member upender singh Join Date: Jul 2014 Location: new delhi, india Posts: 11 Rep Power: 12	Hi Ali, Thanks for the reply. No, I have not activated the heat transfer and radiation modules. I am keeping it strictly adiabatic(Am I wrong?). I am using a 30 species chemkin mechanism to generate the flamelets. Then I generate the PDF table. Then I go for the boundary conditions. The mean mixture fraction for fuel inlet is 1 and the oxidizer inlet is 0. The velocities at both ends is 0.1m/s. I initialize the solution through all domains and run it for 200 iterations. It converges on 80th step. If you think that something is wrong in my approach, please point me in the right direction. I have never used the combustion modules before. Regards