CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > FLUENT

Combustion- eddy-dissipation-model

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   April 4, 2008, 16:16
Default Combustion- eddy-dissipation-model
  #1
joerg
Guest
 
Posts: n/a
Hej, I want to model combustion. I've set up the case with the eddy-dissipation-model. Turbulence modeling is covered by rke and enhanced wall-treatment. y_plus is around 1. The flow field converges (including the dpm-data). But the moment I enable the energy equation to be solved, the residuals for k and e become very large. Fluent detects divergence. Trying to lower the relaxation factors for turbulent quantities makes Fluent diverge in respect to temperature or causes a NAN-Error (it depends...) The temperature exceed the 5000K-limit as well. Has anyone experienced this before and could give me a hint, please? Regards! Joerg
  Reply With Quote

Old   April 5, 2008, 09:26
Default Re: Combustion- eddy-dissipation-model
  #2
ahlem
Guest
 
Posts: n/a
hi, you have to verify matierials properties .Can you specify what type of fuel you use? If you are using methane you can try to put the dilute approximation to constant.
  Reply With Quote

Old   April 5, 2008, 11:02
Default Re: Combustion- eddy-dissipation-model
  #3
joerg
Guest
 
Posts: n/a
I use liquid diesel (c10h22) as droplets. The dilute approx is set to be constant. The fuel mixture consists of gaseous diesel phase (fuel), o2 (oxidizer), n2. The reactants are co2 and h20. The stochiometric values of the reaction are specified correctly. Thanks for your input... I'll double-check the materials!
  Reply With Quote

Old   April 8, 2008, 17:30
Default convergence achieved but no evaporation
  #4
joerg
Guest
 
Posts: n/a
Hello all of you, I've managed to fix the divergence problem. But now there is no evaporation of the liquid phase. Combustion takes not place, therefore. Any hints would be very appreciated! Regards, joerg.
  Reply With Quote

Old   April 16, 2008, 17:02
Default Re: convergence achieved but no evaporation
  #5
Hitesh
Guest
 
Posts: n/a
try patch.........i.e add a energy source to your mesh........this will not affect your final solution........ hope it helps........
  Reply With Quote

Old   April 17, 2008, 17:43
Default Re: convergence achieved but no evaporation
  #6
joerg
Guest
 
Posts: n/a
I've patched the injection zone to 2000K already. Nothing happens... My next try was raising the temperature of the flow at the inlet a small value (4 Kelvin) above evaporation temperature. This doesn't help either. Hmm... I'm clueless... Any other help? Thank you! btw: Is it normal that the patched volume "disappears" after patching a certain value into this zone? Thanks for sharing your ideas, Hitesh! Regards, joerg.
  Reply With Quote

Old   December 10, 2012, 02:56
Default
  #7
New Member
 
Prakash Ghose
Join Date: Dec 2011
Posts: 29
Rep Power: 5
pghoseju is on a distinguished road
OK I will give you a suggestion. Surely you will get evaporation. Go to material and increase the value of binary diffusion of diesel droplet liquid from 3.66e-6 to 3.66e-4. then watch
pghoseju is offline   Reply With Quote

Old   December 17, 2012, 15:41
Default
  #8
New Member
 
Mina
Join Date: May 2012
Posts: 14
Rep Power: 5
kingpots is on a distinguished road
Are you using unsteady tracking and injection ? if yes try to increase the size of the time step
also the convection/diff. option will affect the evaporation (do not use it ) use only diffusion
kingpots is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Eddy Dissipation Model Enots CFX 11 August 12, 2011 04:11
Eddy Dissipation Model Fred CFX 5 May 4, 2010 11:08
EDDY DISSIPATION MODEL PID CFX 0 July 22, 2008 18:52
Eddy dissipation model ioana CFX 1 June 10, 2004 14:15
Eddy Dissipation Model Thomas Main CFD Forum 2 November 7, 2002 08:19


All times are GMT -4. The time now is 11:09.