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

Diffusion Flames with Flamelet model ,little question.

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

Reply
 
LinkBack Thread Tools Display Modes
Old   September 23, 2009, 10:00
Talking Diffusion Flames with Flamelet model ,little question.
  #1
Member
 
AdidaKK's Avatar
 
Mauricio Caamaño Flores
Join Date: May 2009
Location: Punta Arenas, Chile
Posts: 62
Rep Power: 8
AdidaKK is on a distinguished road
Send a message via MSN to AdidaKK
im studyn the theory of diffusion flames before and i understand thats one of the assumptions for the introduction of mixture fraction it is to decouples the diffusion flame computations in two problems:

1)Mixing problem : determine the field of the mixture fraction z(xi,t) as function of spatial coordinates xi and time t.

2)A flame structure problem: where the links between flame variables ( mass fraction Yk(z),T(z) ) and z are use to construct all flames variables.

in other words

z(xi,t)---->(scalar dissipation rate field)---->T(z) ; Yk(z)---->solution of the full problem T(xi,t) ; Yk(xj,t).


my question its , the flamelet model ,how its works with this? the libraries has wich information? , what its the 2 scalar equation who use flamelets?
i hope someone cane help me.

best regards
Mauricio

Last edited by AdidaKK; September 24, 2009 at 10:26.
AdidaKK is offline   Reply With Quote

Old   September 24, 2009, 10:26
Default
  #2
Member
 
AdidaKK's Avatar
 
Mauricio Caamaño Flores
Join Date: May 2009
Location: Punta Arenas, Chile
Posts: 62
Rep Power: 8
AdidaKK is on a distinguished road
Send a message via MSN to AdidaKK
XDD..the two scalar equations its Temperature and mas fraction in function of the mixture fraction.

but the libraries ,wich information contains?

and my last question,the flamelet model its a model based on finite rate chemistry(non equilibrium) but irreversible o reversible chemestry?
AdidaKK is offline   Reply With Quote

Old   October 17, 2009, 10:41
Default
  #3
New Member
 
Emre
Join Date: Oct 2009
Location: Ann Arbor, MI
Posts: 12
Rep Power: 7
esozer is on a distinguished road
In its basic form, you don't solve the species mass fraction equations or the energy equations

You solve: continuity, momentum, mixture fraction (Z) and mixture fraction variance (Zvar) equations.

Then you (typically) model the scalar dissipation rate (chi) using the mixture fraction variance and k and epsilon (or omega) assuming you are using RANS.

Flamelet table will work as:

Z, Zvar, Chi -> rho, mu, diffusivity (for Z), T, Yi

The last two are only needed for post processing.

Reversible reactions are OK. But with flamelet model, chemistry is assumed fast (not infinitely fast though)

Check out: Peters, N., “Turbulent Combustion”, Cambridge University Press, 2000.

Hope this answers your question.
__________________
Free CFD developer
www.freecfd.com
esozer is offline   Reply With Quote

Old   October 17, 2009, 10:47
Default
  #4
Member
 
AdidaKK's Avatar
 
Mauricio Caamaño Flores
Join Date: May 2009
Location: Punta Arenas, Chile
Posts: 62
Rep Power: 8
AdidaKK is on a distinguished road
Send a message via MSN to AdidaKK
thanksssssssss very veryyyyyy much for your help! ,one more thing ,can you visit the ansys cfx forum and see the two first post? both are mine with 2 little question about flamelet ,can you give me your opinion, please?

thankss very veryyy much for your answer
best regards
AdidaKK is offline   Reply With Quote

Old   October 17, 2009, 11:00
Default
  #5
New Member
 
Emre
Join Date: Oct 2009
Location: Ann Arbor, MI
Posts: 12
Rep Power: 7
esozer is on a distinguished road
I think I already answered those questions.

You solve: Z and Zvar equations
You model: chi

Yes, flamelet model is for finite rate but fast chemistry.

Flamelet table is usually a 3D loop-up table with Z,Zvar and Chi as independent variables and rho, mu, diffusivity, T, Y, .... (can contain more depending on implementation).

See the attached chart.

Note: flamelet model is not unique and many variations are there (to solve another equation for chi, etc...) What I am explaining is the most basic form.
Attached Images
File Type: jpg flamelet_model.jpg (34.6 KB, 32 views)
__________________
Free CFD developer
www.freecfd.com
esozer is offline   Reply With Quote

Old   October 17, 2009, 11:09
Default
  #6
Member
 
AdidaKK's Avatar
 
Mauricio Caamaño Flores
Join Date: May 2009
Location: Punta Arenas, Chile
Posts: 62
Rep Power: 8
AdidaKK is on a distinguished road
Send a message via MSN to AdidaKK
ohhhhhhh THANKKKKKKKKKKKKKKKKKKKKKKS VERY MUCH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! IM SO HAPPY RIGHT NOW!!!

last question..that image you attach..its from the book that you recommend me? peters "turbulent combustion" cambrige 2000?



THANKS VERY VERYYYYY MUCH AGAIN! now i can sleep!
AdidaKK is offline   Reply With Quote

Old   October 17, 2009, 11:27
Default
  #7
New Member
 
Emre
Join Date: Oct 2009
Location: Ann Arbor, MI
Posts: 12
Rep Power: 7
esozer is on a distinguished road
No problem. The image is not from the book. It's something I prepared myself.
__________________
Free CFD developer
www.freecfd.com
esozer is offline   Reply With Quote

Old   October 17, 2009, 11:34
Default
  #8
Member
 
AdidaKK's Avatar
 
Mauricio Caamaño Flores
Join Date: May 2009
Location: Punta Arenas, Chile
Posts: 62
Rep Power: 8
AdidaKK is on a distinguished road
Send a message via MSN to AdidaKK
ohh i see ,andd...thats material it is avaible for the public? or its secret property?
AdidaKK is offline   Reply With Quote

Old   October 17, 2009, 11:37
Default
  #9
New Member
 
Emre
Join Date: Oct 2009
Location: Ann Arbor, MI
Posts: 12
Rep Power: 7
esozer is on a distinguished road
It's from my dissertation which will be available in a few weeks
__________________
Free CFD developer
www.freecfd.com
esozer is offline   Reply With Quote

Old   October 17, 2009, 11:40
Default
  #10
Member
 
AdidaKK's Avatar
 
Mauricio Caamaño Flores
Join Date: May 2009
Location: Punta Arenas, Chile
Posts: 62
Rep Power: 8
AdidaKK is on a distinguished road
Send a message via MSN to AdidaKK
exellent ,do you will post here your presentation?
im gona be waiting ...exellent job
best regards
AdidaKK is offline   Reply With Quote

Old   November 3, 2009, 02:03
Default
  #11
Member
 
AdidaKK's Avatar
 
Mauricio Caamaño Flores
Join Date: May 2009
Location: Punta Arenas, Chile
Posts: 62
Rep Power: 8
AdidaKK is on a distinguished road
Send a message via MSN to AdidaKK
uhm...i read the theory modelling of ansys cfx ,and one of the assumptions for flamelet model its was lewis number equal to unity, my question is: the species heat capacities are equal and constant too? (Cpk=Cp)

thanks very much
AdidaKK is offline   Reply With Quote

Old   November 3, 2009, 03:01
Default
  #12
Member
 
AdidaKK's Avatar
 
Mauricio Caamaño Flores
Join Date: May 2009
Location: Punta Arenas, Chile
Posts: 62
Rep Power: 8
AdidaKK is on a distinguished road
Send a message via MSN to AdidaKK
ohh and one more, flamelet model its single step chemistry? or multi step?

thanks veryy much
AdidaKK 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
one question about the Spalart-Allmaras model? liuchen Main CFD Forum 0 March 15, 2007 01:29
A question about Monte Carlo model Forrest CFX 0 May 8, 2006 04:28
turbulence model question Jason Wei Main CFD Forum 1 May 6, 2003 00:45
Why Turbulence models are not universal. Senthil Main CFD Forum 4 July 5, 2000 04:34
Flamelet in CFX-TASCflow Karla Medina Main CFD Forum 4 February 25, 1999 16:00


All times are GMT -4. The time now is 22:25.