CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

Partially Premixed Combustion

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   July 26, 2006, 09:57
Default At the risk of asking a really
  #1
rbw
New Member
 
Ramiro Brito Willmersdorf
Join Date: Mar 2009
Location: Recife, Pernambuco, Brasil
Posts: 15
Rep Power: 17
rbw is on a distinguished road
At the risk of asking a really silly question...
(Remember: as Homer Simpson used to say -- "There are no stupid questions, just stupid people")

What exactly is considered partially premixed combustion in OpenFoam? "Partially Premixed" sounds like "partially pregnant"

I'm asking this because I'd like to know to which kind of problems XiFoam is applicable.

(BTW: I know what are premixed and non-premixed combustion, but I was under the impression this was an either/or thing.)

Many thanks!
rbw is offline   Reply With Quote

Old   July 26, 2006, 10:39
Default Hi Ramiro, which kind of comb
  #2
Member
 
Tommaso Lucchini
Join Date: Mar 2009
Posts: 87
Rep Power: 17
lucchini is on a distinguished road
Hi Ramiro,
which kind of combustion problem would you like to simulate?
Bye
Tommaso
lucchini is offline   Reply With Quote

Old   July 26, 2006, 12:02
Default Hi Tommaso, Jet Fires, ie,
  #3
rbw
New Member
 
Ramiro Brito Willmersdorf
Join Date: Mar 2009
Location: Recife, Pernambuco, Brasil
Posts: 15
Rep Power: 17
rbw is on a distinguished road
Hi Tommaso,

Jet Fires, ie, (possibly very large) flames in an open environment, originated at a high speed gas leaks. Very non-premixed, I would think.
rbw is offline   Reply With Quote

Old   July 27, 2006, 03:25
Default I think it is partially-premix
  #4
Member
 
Tommaso Lucchini
Join Date: Mar 2009
Posts: 87
Rep Power: 17
lucchini is on a distinguished road
I think it is partially-premixed combustion, thus it might be better to use reactingFoam
bye
lucchini is offline   Reply With Quote

Old   July 27, 2006, 15:53
Default Well, there you are, that's wh
  #5
rbw
New Member
 
Ramiro Brito Willmersdorf
Join Date: Mar 2009
Location: Recife, Pernambuco, Brasil
Posts: 15
Rep Power: 17
rbw is on a distinguished road
Well, there you are, that's why I'm asking.

I thought (and to be honest, still do think) that since the fuel and air are coming in separate streams, this would be non-premixed combustion.

I also thought that for partially premixed combustion there could be less expensive (than solving the full chemistry) models implemented in OpenFOAM, based on flamelet libraries, pdf's, etc. That's why I was curious about XiFoam.

Why do you thing reactingFoam would be more adequate?
rbw is offline   Reply With Quote

Old   July 27, 2006, 16:01
Default Non-premixed combustion (almos
  #6
New Member
 
Jojo
Join Date: Mar 2009
Posts: 7
Rep Power: 17
jojo is on a distinguished road
Non-premixed combustion (almost) never exists.
jojo is offline   Reply With Quote

Old   July 27, 2006, 16:10
Default Of course I meant "Why do you
  #7
rbw
New Member
 
Ramiro Brito Willmersdorf
Join Date: Mar 2009
Location: Recife, Pernambuco, Brasil
Posts: 15
Rep Power: 17
rbw is on a distinguished road
Of course I meant "Why do you think"
rbw is offline   Reply With Quote

Old   July 27, 2006, 16:28
Default Hello Joan, Yes, I understa
  #8
rbw
New Member
 
Ramiro Brito Willmersdorf
Join Date: Mar 2009
Location: Recife, Pernambuco, Brasil
Posts: 15
Rep Power: 17
rbw is on a distinguished road
Hello Joan,

Yes, I understand that, in reality, really non-premixed combustion is almost impossible, except on very controlled laminar counterflow experimental setups.

However, I was under the impression that there are very different approaches to numerical modeling of combustion when the fuel and oxidant come to a combustion "chamber" already mixed in the same stream, or when they come in different streams and are mixed in the combustion "chamber" by the combustion process itself. I thought (and, at the risk of sounding really stubborn, still do ) that this was what was meant by "premixed" and "non-premixed" combustion in the numerical combustion literature.
rbw is offline   Reply With Quote

Old   July 27, 2006, 17:18
Default You are perfectly right. T
  #9
New Member
 
Jojo
Join Date: Mar 2009
Posts: 7
Rep Power: 17
jojo is on a distinguished road
You are perfectly right.

The reality is that non-premixed models are unable to predict correctly the most important part of the `non-premixed flame': the impact of the premixing occuring into the chamber on the flame. Simply because there is no place for premixing in their formalism which is strictly non-premixed. This is a matter of fundamental hypothesis. Not a weakness of the models by themselves.

As a consequence the point of maximum heat release, where the flame is lifted, as well as anchoring cannot be addressed with these models. The critical part of the physics is missed. This is why partially-premixed models have been proposed.
jojo is offline   Reply With Quote

Old   July 28, 2006, 07:54
Default OK! I think I see the point
  #10
rbw
New Member
 
Ramiro Brito Willmersdorf
Join Date: Mar 2009
Location: Recife, Pernambuco, Brasil
Posts: 15
Rep Power: 17
rbw is on a distinguished road
OK!

I think I see the point perfectly now!

Many thanks!
rbw is offline   Reply With Quote

Reply


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
XiFoam partially premix combustion tavasoly OpenFOAM Running, Solving & CFD 0 July 1, 2008 12:01
Partially Premixed Reaction Mechanism usker Siemens 0 October 30, 2007 04:03
Sawdust Combustion-Non-premixed Combustion Model Jessy FLUENT 1 June 19, 2007 11:59
Mixture fraction in Partially premixed combustion Viktor FLUENT 1 December 30, 2005 00:30
Partially premixed combustion paper. Repap. Main CFD Forum 4 July 3, 2004 10:26


All times are GMT -4. The time now is 14:04.