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

spray injection

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   January 8, 2009, 06:55
Default spray injection
  #1
Johannes P.
Guest
 
Posts: n/a
Hey!!

I wanna simulate an injection of fuel(Dodecane(L)) into a high pressure cell. I wanna have a look to the length of the injected fuel jet and to the diameter and velocity of the fuel droplets.

So, the problem is that the length of the jet is still constant. Doesn't matter if the pressure in the cell is initialized to 1e+5Pa or to 1000e+5Pa. So, what's wrong with my simulation?

Maybe you've an idea;-) Thanks a lot.

Johannes
  Reply With Quote

Old   January 8, 2009, 08:39
Default Re: spray injection
  #2
James
Guest
 
Posts: n/a
You don't say which code. Is momentum coupling turned on ?
  Reply With Quote

Old   January 8, 2009, 10:59
Default Re: spray injection
  #3
Johannes P.
Guest
 
Posts: n/a
Hey! what do you mean with "code"? It's an Lagrangian Multi-Phase spray injection with atomization.The Atomization model is the "Huh-Model", the "MPI-2" is the nozzle model. Heat, Mass and Momentum Transfer are Standard with 0 for mass coef. and 1 for the slip factor. there is one inlet and one pressure boundary created. I wanna simulate pressures between 1e+05 and 100e+05Pa. That I can see how the pressure influences the length of my jet and the velocity and diameter of my parcels.

Thank you very much, johannes

  Reply With Quote

Old   January 8, 2009, 11:23
Default Re: spray injection
  #4
Johannes P.
Guest
 
Posts: n/a
ah, ok, it's the code of version 3.26

sorry, don't have the best english ;-)
  Reply With Quote

Old   January 8, 2009, 13:39
Default Re: spray injection
  #5
Pauli
Guest
 
Posts: n/a
Sounds like your doing a bunch right. But something is definitely wrong. You should get liquid length changing with pressure. (I did.)

Don't use the MPI nozzles unless you have the appropriate licenses. They appear to work but give strange results. Use the default nozzle.

Are you using variable properties? You should.

Are you sure you are getting the pressure you expect? Are you running compressible or incompressible? Do you have the correct reference pressure for your pressure boundary? Where is your reference cell. I suspect this is where your problem lies.
  Reply With Quote

Old   January 9, 2009, 13:54
Default Re: spray injection
  #6
James
Guest
 
Posts: n/a
Do you see the influence of the spray on the fluid ?
  Reply With Quote

Old   January 9, 2009, 14:27
Default Re: spray injection
  #7
Pauli
Guest
 
Posts: n/a
Yes I have momentum transfer from the liquid to the gas. Maximum gas velocities are a fraction of maximum liquid velocity. The exact value is grid dependent. I've seen values between 1/3 & 1/2.
  Reply With Quote

Old   January 14, 2009, 05:43
Default Re: spray injection
  #8
Johannes P.
Guest
 
Posts: n/a
Hey, thank you very much for your answers!

I'm a student and i'm working at the university one day a week.So, sorry for the late answer, but i'm just at the working place once a week.

Yeah,somthing is wrong...but don't know what

Ok, for the next calculation i will use the standard nozzle model. but i guess that the university has the appropriate licenses for MPI model.

With variable properties you mean the molecular properties of the fluid inside the pressure cell, or? But you're right, i use constant ones.

I'm pretty sure that i get the right pressure, cause i made a pressure plot and i get the pressure i initialized.

For my calculation, the vapor and the liquid phase are incompressible.

What's the correct pressure for my pressure boundary? My reference cell is a cell inside my volume...

So, hope you can help me...

have a nice day and thaks a lot for your answers.

Best regards,

Johannes

  Reply With Quote

Old   January 14, 2009, 09:38
Default Re: spray injection
  #9
James
Guest
 
Posts: n/a
If you have a pressure boundary then it overrides the pressure cell location but its value is relative to the pressure reference value.

All other things being equal if you only have one pressure boundary then STAR typically initializes best if you make the pressure reference value the same value as the desired value for the boundary and make the boundary value 0.
  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
Urgent help needed with spray injection nick Siemens 14 June 29, 2008 19:48
Spray Injection usker Siemens 2 April 6, 2007 01:41
spray injection mmacrb FLUENT 0 January 10, 2007 05:57
water injection into air (not spray) bioman66 CFX 1 July 11, 2006 07:34
spray injection. Moon Siemens 2 May 6, 2003 02:06


All times are GMT -4. The time now is 12:27.