CFD Online Logo CFD Online URL
Home > Forums > FLUENT

Combustion problem

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

LinkBack Thread Tools Display Modes
Old   April 23, 2013, 03:44
Exclamation Combustion problem
New Member
Alok Deshpande
Join Date: Oct 2010
Posts: 10
Rep Power: 9 is on a distinguished road
Hi All,

I am solving a flameless combustion problem with the following BC's,

V_air = 7.53 m/s, T_air = 955 K
V_ch4 = 24.34 m/s, T_ch4 = 300 K

Flue gases recirculates in the combustion chamber and exits from the exit located above the air/fuel inlet, thus giving finite turbulence-chemistry interaction. I am using Eddy Dissipation Concept (EDC) under Species Transport model.

Now the problem is, while solving the problem in unsteady case, combustion does not occur (as the peak temperature after 15-20 sec is still of order 957 K). Do I need to provide any ignition method?

Such problem occurred when I was simulating a benchmark problem on combustion. Using the Species Transport Model, steady state simulations showed the combustion (but overpredicted the temperatures) but unsteady simulations did not show any combustion.

Please somebody tell me what might be going wrong.. I need to submit my dissertation in 10-15 days..

Alok is offline   Reply With Quote

Old   April 23, 2013, 08:09
James Willie
Join Date: Mar 2009
Posts: 80
Rep Power: 10
jwillie2000 is on a distinguished road
What was your time step size in the simulation? Plus i would suggest you do a steady run and then switch from it to unsteady. You surely have to ignite the mixture to get the flame. It does not affect the converged solution since the fuel you add is little and it burns out in a short time. About the time step u have to ensure that the time step u are choosing is less than or of the order of the chemical time scale. U can estimate it by taking the smallest cell in your grid and using the mean flow velocity in it that cell and ratio of the cell size to the mean flow velocity would give you an idea of the time step size u can use. Jimmy
jwillie2000 is offline   Reply With Quote

Old   April 23, 2013, 08:41
New Member
Alok Deshpande
Join Date: Oct 2010
Posts: 10
Rep Power: 9 is on a distinguished road
Hi Jimmy,

Thank you for your suggestion. I will check the timestep. Flow and chemistry timescales are similar in this case. I will choose the timestep accordingly.

Can I choose the ignition location and time arbitrarily? What could be the energy of ignition, default would do?


Alok is offline   Reply With Quote


combustion, edc

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
hel (turbulent viscosity ratio limited) for supersonic combustion problem omar.2002bh FLUENT 2 September 5, 2012 11:04
Problem using EDM for combustion nakul FLUENT 1 August 11, 2011 05:01
A problem with combustion Luk Main CFD Forum 1 April 28, 2008 09:55
Combustion problem rupal CFX 0 April 21, 2008 05:29
problem in incomplete nonpremixed combustion muro FLUENT 0 September 28, 2007 06:54

All times are GMT -4. The time now is 13:55.