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

Too high maximum gas temperature

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   October 1, 2001, 12:48
Default Too high maximum gas temperature
  #1
Ossi
Guest
 
Posts: n/a
Hi,

I have observed that in many times the maximum gas temperatures in my diesel engine simulations are extremely high, close to 4000K !! And almost always they are more than 3000K during the most intense phase of combustion. I think the adiabatic gas temperature in diesel conditions is somewhere around 3200K or something like that. Consequently, everything above that is too high. Also I have seen that in KIVA simulations the maximum gas temperatures are below 3000K in the same cases the maximum temperatures in STAR-CD are above 3200 K (?)

Has anybody else observed similar kind of behavior ?
  Reply With Quote

Old   October 4, 2001, 16:35
Default Re: Too high maximum gas temperature
  #2
Ossi
Guest
 
Posts: n/a
I might add that I have been using Eddy Break Up- type of combustion model, and that with the RNG turbulence model the maximum gas temperatures are higher than with the std k-e model. But even with the std k-e model, the maximum gas temperatures seem to be sometimes too high.
  Reply With Quote

Old   October 8, 2001, 09:20
Default Re: Too high maximum gas temperature
  #3
yang
Guest
 
Posts: n/a
Yes,I also meet the same problem when I use EBU model for propane combustion,the max. temperature is above 300 that I expect.I think following can be consider. 1,rebuild the mesh. 2,using high order discrete try to do and tell me the resluts.

/Yang

  Reply With Quote

Old   October 8, 2001, 11:36
Default Re: Too high maximum gas temperature
  #4
Ossi
Guest
 
Posts: n/a
I am using good quality grid now, and MARS scheme for momentum, turbulence, and density. I use GAMMA for the enthalpy and scalars. I am not sure this effect (too high maximum gas temperature) comes from the discretization; I think a more likely source is the ignition model used. Depending on the ignition model, different cps for the gas phase are used.

When I use the Shell ignition model, the maximum gas temperatures are in many cases close to 4000K (only during a very short moment but still) but if I do not use Shell (but the other alternative to ignite a mixture) the maximum gas temperatures are much, much lower! This is what I just recently discovered. This may be due to the cps used with and without the Shell model, or due to the implementation of the Shell model (?)

What ignition model are you using ?
  Reply With Quote

Old   October 11, 2001, 06:13
Default Re: Too high maximum gas temperature
  #5
yang
Guest
 
Posts: n/a
It is interested conclusion. According my experience, Peak temperature before convergence maybe very high because the heat transfer is smallMy ignition model is the simplest one.I just set the begin iteration.but I set very low fraction.I will try to adjust this. /yang
  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
Maximum temperature at each axial location Eric FLUENT 0 March 14, 2009 07:30
the maximum value of granular temperature haijj FLUENT 0 August 25, 2008 06:02
Allowable maximum temperature Atit Koonsrisuk CFX 0 January 27, 2004 02:16
Why temperature is so high? Albert FLUENT 2 June 22, 2003 12:28
Urgent help needed in finding maximum temperature. Deadly FLUENT 3 September 3, 2002 09:43


All times are GMT -4. The time now is 11:55.