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

high temperature in methane combustion

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

Like Tree2Likes
  • 1 Post By Ant
  • 1 Post By davedong

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   April 17, 2008, 01:23
Default high temperature in methane combustion
  #1
David
Guest
 
Posts: n/a
Hi there, Does anybody meet such problem? The temperature will be 3000K! or higher. According my knowledge, It is impossible.

Anyone have a similar case in FLUENT website? Thank you.

David
  Reply With Quote

Old   April 17, 2008, 01:57
Default Re: high temperature in methane combustion
  #2
Ant
Guest
 
Posts: n/a
Hi David,

The temperature predicted would depend upon the combustion model, reaction kinetics and specific heat polynomials.

Check the following:

1. Combustion model: The temperature predictions can be set right quickly by using the simplified PDF model. The flame shape would also be predicted well. The main constraint is that this model over predicts the flame stability.

2. Oxidant used: Are you using Air, pure oxygen or oxygen enriched air? If you are using pure oxygen or high concentration of oxygen as oxidant you should either use PDF model or add dissociation reactions to the reaction mechanism.

3. Reaction mechanism: Are you using single step or two step global reaction? Are you adding and dissociation reaction? The temperature would be over predicted if you use a single step chemistry.

4. Cp: Do not use constant values. Use polynomials. It has been seen that the polynomials for CH4 and N2 used in the fluent database are incorrect above 1100 K. You need to use CET89 polynomials of CH4 & N2.

I would not be able to tell you more details on reaction mechanism since we are working on similar lines. My suggestion is to use PDF model to give quick and reasonable predictions.

Regards, Ant
sahm likes this.
  Reply With Quote

Old   April 17, 2008, 02:25
Default Re: high temperature in methane combustion
  #3
David
Guest
 
Posts: n/a
Great Thanks Ant!
  Reply With Quote

Old   August 2, 2010, 03:37
Default
  #4
New Member
 
Dong Liang
Join Date: Jan 2010
Location: Shanghai, China
Posts: 12
Rep Power: 16
davedong is on a distinguished road
Quote:
Originally Posted by Ant
;150081
Hi David,

The temperature predicted would depend upon the combustion model, reaction kinetics and specific heat polynomials.

Check the following:

1. Combustion model: The temperature predictions can be set right quickly by using the simplified PDF model. The flame shape would also be predicted well. The main constraint is that this model over predicts the flame stability.

2. Oxidant used: Are you using Air, pure oxygen or oxygen enriched air? If you are using pure oxygen or high concentration of oxygen as oxidant you should either use PDF model or add dissociation reactions to the reaction mechanism.

3. Reaction mechanism: Are you using single step or two step global reaction? Are you adding and dissociation reaction? The temperature would be over predicted if you use a single step chemistry.

4. Cp: Do not use constant values. Use polynomials. It has been seen that the polynomials for CH4 and N2 used in the fluent database are incorrect above 1100 K. You need to use CET89 polynomials of CH4 & N2.

I would not be able to tell you more details on reaction mechanism since we are working on similar lines. My suggestion is to use PDF model to give quick and reasonable predictions.

Regards, Ant
I'm facing the same problem. well, it does well in the pdf-LES or pdf-RANS simulation. but the eddy-dissipation simulation is still odd with 2400 K or even more higher. i guess the reaction is too simple to describe the flame. right?
PS: i use single step methane-air to model sandia flame d.
Passenger94 likes this.
davedong is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
High temperature methane+air Peter FLUENT 5 January 26, 2009 19:04
Temperature drops in Methane combustion CPRL Siemens 0 July 24, 2007 13:56
High Combustion Temperature in the EBU model Mehdi Siemens 0 April 24, 2006 06:53
high temperature in methane combustion Özer AYDIN FLUENT 9 April 24, 2005 17:11
Methane+air temperature too high Stanislav Kraev FLUENT 5 June 3, 2004 11:54


All times are GMT -4. The time now is 14:43.