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

How to ignite the premixed flame?

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

Reply
 
LinkBack Thread Tools Display Modes
Old   June 28, 2007, 23:58
Default How to ignite the premixed flame?
  #1
Harry
Guest
 
Posts: n/a
Hi! My simulation is the methane-air mixture premixed flame in a closed tube. After the mixture filled in the tube, the eletric spark activated. But I do not konw how to actualize the ignition process. Is it the same like fluent, by a specified region of high temperature? If so, this condition will be set up in ICEM or CFX? I am a freshhand. Any suggestions will be appreciated! Thanks!
  Reply With Quote

Old   June 29, 2007, 03:48
Default Re: How to ignite the premixed flame?
  #2
Gert-Jan
Guest
 
Posts: n/a
Add an low initial concentration of the products.

Gert-Jan
  Reply With Quote

Old   June 29, 2007, 17:43
Default Re: How to ignite the premixed flame?
  #3
Joey2007
Guest
 
Posts: n/a
If I remind correctly there is an ignition model for BVM in 11
  Reply With Quote

Old   July 2, 2007, 07:19
Default Re: How to ignite the premixed flame?
  #4
harry
Guest
 
Posts: n/a
hi, Gert-Jan

If I add the products in the combustion chamber, can I get the ignition and flame propagating process? They are two important parts of my research.

Thanks!

  Reply With Quote

Old   July 2, 2007, 07:31
Default Re: How to ignite the premixed flame?
  #5
Astrid
Guest
 
Posts: n/a
You get ignition. Flame propagation process? In a time dependent simulation, yes I think so.

Gert-Jan

  Reply With Quote

Old   July 2, 2007, 11:02
Default Re: How to ignite the premixed flame?
  #6
harry
Guest
 
Posts: n/a
I have added the products in the tube, but there is no reaction. Is there anything more I should do? Or would you please send me a similar case for reference?

Thanks a lot!

Harry
  Reply With Quote

Old   July 2, 2007, 12:50
Default Re: How to ignite the premixed flame?
  #7
Gert-Jan
Guest
 
Posts: n/a
I don't have a reference case. Neither do I have an easy suggestion. Could you ask your local representative?

Gert-Jan
  Reply With Quote

Old   July 2, 2007, 14:50
Default Re: How to ignite the premixed flame?
  #8
popi
Guest
 
Posts: n/a
hi Harry

I'm also trying to ignite a mixture in order to simulate a combustion chamber. I don't know how to solve my problem. However i have ignite my mixture by creating a Source Point. This source is described by an expresion of energy during some time. This creates a high temperature point, so the ignition starts. This could help you...maybe... By the way, I search for help. I'm able to ignite the mixture, but I cannot initialize the mixture how i would like. WHY???? I'm trying to ignite a H2-AIR mixture...
  Reply With Quote

Old   July 2, 2007, 22:15
Default Re: How to ignite the premixed flame?
  #9
harry
Guest
 
Posts: n/a
hi,Popi

would you please describe how to create the soure point for ignition in detail?

Thanks for your help.
  Reply With Quote

Old   July 3, 2007, 14:42
Default Re: How to ignite the premixed flame?
  #10
popi
Guest
 
Posts: n/a
Hi Harry,

First of all, I'm using CFX 10. If you're using this version of the software, there is a Flow Object (Create Menu) called SOurce Point. I just have to specified the LOCATION and the ENERGY TOTAL SOURCE(Power) (sometimes also available, energy flux). At this point I write a CEL expression that specifies ; the total energy source, spark duration time, and a STEP function to express when ignition starts and when finishes.

If you want more information please tell me. If you want, i can send you the energy CEL expression...

Ignition starts but it's more difficult to reach a good combustion model; a simulation where the flame doesn't extinct...

Please tell me if it went OK
  Reply With Quote

Old   July 4, 2007, 02:33
Default Re: How to ignite the premixed flame?
  #11
Joey2007
Guest
 
Posts: n/a
Be careful!

- BVM: the flame progation is describbed by reaction progress. There is no direct coupling with the energy equation. You can not ignite by heat release.

- EDM: the flame propagation is describbed by species equqtion. The source term is not influenced by the temperature! You can not ignite by heat release.

- Finite rate chemistry. Here it is possible. However this approach is not adequate for turbulent combustion.

  Reply With Quote

Old   July 4, 2007, 15:32
Default Re: How to ignite the premixed flame?
  #12
popi
Guest
 
Posts: n/a
Hello joey

So if I'm trying to simulate a spark with a SOURCE POINT in cfx10, only the Finite rate chemistry model is valid????? I didn't know it. I'm trying to simulate a Hydrogen Air combustion in a combustion chamber......really difficult, but could be an approximate result to do the ignition spark with a source point and using Finite rate chemistry????

Otherwise...what can I do?? I'm realizing that it's very difficult to simulate this so... an approximate solution could help me in my problem.

THANKS A LOT
  Reply With Quote

Old   July 9, 2007, 18:29
Default Re: How to ignite the premixed flame?
  #13
Joey2007
Guest
 
Posts: n/a
Hi, I had much work the last week.

You can not ignite the BVM and the EDM model by a heat source or a temperature initialisation with high temperature. Have a look at the basic equations of both models. For example the BVM: its source term is proportional to the gradient of the reaction progress. It does not ´feel´ energy sources. You have do to something with the reaction progress either by initialisation or by source term in the reaction progress equation.

Similiar for EDM. BTW: This things come from the standard models the documented in the literature (in case of bvm the Zimont model). They are not specific for cfx.

  Reply With Quote

Old   April 14, 2009, 08:45
Default Hi Popi
  #14
New Member
 
xulixian
Join Date: Apr 2009
Posts: 4
Rep Power: 7
xulixian is on a distinguished road
Quote:
Originally Posted by popi
;82406
hi Harry

I'm also trying to ignite a mixture in order to simulate a combustion chamber. I don't know how to solve my problem. However i have ignite my mixture by creating a Source Point. This source is described by an expresion of energy during some time. This creates a high temperature point, so the ignition starts. This could help you...maybe... By the way, I search for help. I'm able to ignite the mixture, but I cannot initialize the mixture how i would like. WHY???? I'm trying to ignite a H2-AIR mixture...
I am now working on a simulation of H2/air mixture in a micro tube, I got similar problerms as you met before, I hope to get some help from you. I don't know how to contact you, my email is l.xu@utwente.nl , Hope to get your reply.

regards, Lixian
xulixian is offline   Reply With Quote

Old   April 16, 2009, 16:52
Default
  #15
Senior Member
 
Join Date: Mar 2009
Location: Europe
Posts: 168
Rep Power: 7
joey2007 is on a distinguished road
This thread is quite old. As far as BVM is concerned meanwhile is a spark iginition model available. Furtheron the support told me that in 12.0 there will also a auto ignition model available.
joey2007 is offline   Reply With Quote

Old   September 7, 2009, 14:35
Default hi every one
  #16
New Member
 
shah samip
Join Date: Aug 2009
Posts: 6
Rep Power: 7
shahsamipp is on a distinguished road
hi....friends
i m also doing work on premixed combn.......of a CH4/air.......
i m trying to finding out a flammability of the mixture.....
4 that i m using ASTM std.......
as per that if the ignited flame is reached at top of a 1.8 m
(50 cm dia) long cylinder the mixture is flammable else not.......
m using BVM 4 this.......
but i m bit confused to define a boundary condn........
at the top of the tube is closed and the mixture is ignited 4m bottom........
this is giving me a domain overflow error...........
how to solve this.........
thanks .......
regards
samip shah
shahsamipp 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
Unable to ignite flame Eshwar FLUENT 0 July 20, 2011 08:38
Detailed chemistry premixed VS diffusion H2 flame fireman FLUENT 1 May 27, 2011 09:22
ignition of premixed flame tilman FLUENT 6 June 25, 2009 05:40
premixed flame modeling problem peiyong wang CFX 1 July 18, 2008 13:02
Premixed flame. Interested. Main CFD Forum 2 June 24, 2005 07:32


All times are GMT -4. The time now is 13:11.