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

For Joe : CFD in a Wankel engine

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   September 7, 2007, 08:26
Default For Joe : CFD in a Wankel engine
  #1
amcfd
Guest
 
Posts: n/a
Hi Joe, I posted a message on the forum a few months ago for a problem with flow simulation in a Wankel engine. In your answer to me, you sais that you were setting up problems in which you considered flows in such a Wankel engine. Did you succed ? I've been working a lot on the leakage problem between the 3 chambers (dut to the fact that you can't close the volume when you're using dynamic meshing). I found some solutions, but none of them seemed to be really suitable. Now I'm working on only one wankel chamber to try to avoid leakage and close the volume.I was wondering if you've find a way to simulate the flow without inter-chamber leakage ?
  Reply With Quote

Old   September 7, 2007, 09:02
Default Re: For Joe : CFD in a Wankel engine
  #2
Joe
Guest
 
Posts: n/a
Like I said before you have to use an artificial, imposed momentum source near the rotor tips to force localised fluid quiescence.

You know where the rotor starts, you know how it moves with time ... so you know where the rotor tips are at any point in time. Ergo, you can define this localised momentum source to prevent inter-chamber leakage.
  Reply With Quote

Old   April 14, 2011, 07:36
Default
  #3
New Member
 
Pravin Gangwar
Join Date: Mar 2010
Location: Madrid, Spain
Posts: 7
Rep Power: 16
pravin.iitk is on a distinguished road
Hi, I am working on wankel engine too. I tried imposing momentum source but it not working. Its always backflowing in the adjacent chamber. On the contrary when I am setting up a similar problem but only with translation not rotation then its working. Do you have any idea what it could be? Please let me know. I can also provide you udf which I wrote for marking the cells for momentum source.

Thanks in advance
pravin.iitk is offline   Reply With Quote

Old   August 5, 2011, 14:44
Default
  #4
Member
 
Join Date: May 2010
Posts: 57
Rep Power: 15
Catthan is on a distinguished road
Hi to all and apologies for reviving an old thread, hoping that the original posters will be notified by email.

I am trying to model the gas circuit in a Wankel engine, not combustion or anything, just the compression and expansion of the working gas.

I cannot figure out the proper UDF to move the rotor CG along the eccentricity path and then rotate the rotor around its CG.

I have written a Define CG macro UDF containing the x and y velocity equations found in texts but it seems smth is wrong.

Can you please give me some guidance?

Best regards,
Thanos
Catthan is offline   Reply With Quote

Old   March 6, 2012, 10:22
Default
  #5
New Member
 
Torres
Join Date: Mar 2012
Posts: 9
Rep Power: 14
cz5224043 is on a distinguished road
Quote:
Originally Posted by Joe
;145186
Like I said before you have to use an artificial, imposed momentum source near the rotor tips to force localised fluid quiescence.

You know where the rotor starts, you know how it moves with time ... so you know where the rotor tips are at any point in time. Ergo, you can define this localised momentum source to prevent inter-chamber leakage.
Hi Joe,

Could you please explain some details about the method of importing momentum source to sort the gap leakage problem?
I am an undergrad and quite new about CFD, although I have successfully modelled the operation.

Many thanks
cz5224043 is offline   Reply With Quote

Old   March 6, 2012, 11:03
Default Udf
  #6
New Member
 
Pravin Gangwar
Join Date: Mar 2010
Location: Madrid, Spain
Posts: 7
Rep Power: 16
pravin.iitk is on a distinguished road
Quote:
Originally Posted by Catthan View Post
Hi to all and apologies for reviving an old thread, hoping that the original posters will be notified by email.

I am trying to model the gas circuit in a Wankel engine, not combustion or anything, just the compression and expansion of the working gas.

I cannot figure out the proper UDF to move the rotor CG along the eccentricity path and then rotate the rotor around its CG.

I have written a Define CG macro UDF containing the x and y velocity equations found in texts but it seems smth is wrong.

Can you please give me some guidance?

Best regards,
Thanos
Try to check initial CG position you have to give in fluent. Use this code it may help you

#include "udf.h"
#define r -0.0116 /*Eccentricity*/
#define k 57.2727 /*rad to degree*/
#define w 314.16 /*angular velocity in rad/sec*/

/* for grid motion */
DEFINE_CG_MOTION(rotor, dt, vel, omega,time, dtime)
{
real beta;

NV_S(vel, =, 0.0);
NV_S(omega, =, 0.0);

omega[2] = 314.16; /*angular velocity in rad/sec*/
beta = 942.48; /*angular velocity of rotor in rad/sec*/

vel[0] = -beta*r*sin(beta*time);
vel[1] = beta*r*cos(beta*time);
vel[2]= 0;

}
pravin.iitk is offline   Reply With Quote

Old   March 6, 2012, 11:10
Default Momentum sources
  #7
New Member
 
Pravin Gangwar
Join Date: Mar 2010
Location: Madrid, Spain
Posts: 7
Rep Power: 16
pravin.iitk is on a distinguished road
Quote:
Originally Posted by cz5224043 View Post
Hi Joe,

Could you please explain some details about the method of importing momentum source to sort the gap leakage problem?
I am an undergrad and quite new about CFD, although I have successfully modelled the operation.

Many thanks
What I did was to mark the cells at rotor tip while it rotating and use DEFINE_SOURCE to make those marked cells a source which makes relative velocity between rotor tip and marked cells zero.
pravin.iitk is offline   Reply With Quote

Old   March 7, 2012, 08:47
Default
  #8
New Member
 
Torres
Join Date: Mar 2012
Posts: 9
Rep Power: 14
cz5224043 is on a distinguished road
Quote:
Originally Posted by pravin.iitk View Post
What I did was to mark the cells at rotor tip while it rotating and use DEFINE_SOURCE to make those marked cells a source which makes relative velocity between rotor tip and marked cells zero.
Thank you so much for the information. I am stuck here for months and so frustrated.

Did your model eventually work in terms of sealing the chamers?

Have you still got the SOURCE UDF file? Could you please post it?
I'm sure it will be very helpful for me.

Thank you very much.
cz5224043 is offline   Reply With Quote

Old   March 8, 2012, 06:05
Default
  #9
New Member
 
Pravin Gangwar
Join Date: Mar 2010
Location: Madrid, Spain
Posts: 7
Rep Power: 16
pravin.iitk is on a distinguished road
Quote:
Originally Posted by cz5224043 View Post
Thank you so much for the information. I am stuck here for months and so frustrated.

Did your model eventually work in terms of sealing the chamers?

Have you still got the SOURCE UDF file? Could you please post it?
I'm sure it will be very helpful for me.

Thank you very much.
It was working well when pressure difference around the seal was less but when pressure diff was increasing it started leaking again so I had to manipulate the coefficient in the source term to increase when pressure difference is increasing.
I have that file somewhere in my external hard disk. I'll look for it and let you know.
pravin.iitk is offline   Reply With Quote

Old   March 8, 2012, 08:11
Default
  #10
New Member
 
Torres
Join Date: Mar 2012
Posts: 9
Rep Power: 14
cz5224043 is on a distinguished road
Quote:
Originally Posted by pravin.iitk View Post
It was working well when pressure difference around the seal was less but when pressure diff was increasing it started leaking again so I had to manipulate the coefficient in the source term to increase when pressure difference is increasing.
I have that file somewhere in my external hard disk. I'll look for it and let you know.
Hi Pravin,

Thanks a lot for your help.

I have another question here. How did you mark the cells around the tips in dynamic mesh(I tried yesterday while the marked cells became unmarked again after the rotor started rotating), Or did you change the orginal mesh to create new zones around the tips?
It'd be great and saving a lot of my time if you could please let me have a look at your case files. (My project is due in two weeks and my supervisor said, 'stop the leakage or fail'...)
cz5224043 is offline   Reply With Quote

Old   March 8, 2012, 08:18
Default
  #11
New Member
 
Pravin Gangwar
Join Date: Mar 2010
Location: Madrid, Spain
Posts: 7
Rep Power: 16
pravin.iitk is on a distinguished road
Quote:
Originally Posted by cz5224043 View Post
Hi Pravin,

Thanks a lot for your help.

I have another question here. How did you mark the cells around the tips in dynamic mesh(I tried yesterday while the marked cells became unmarked again after the rotor started rotating), Or did you change the orginal mesh to create new zones around the tips?
It'd be great and saving a lot of my time if you could please let me have a look at your case files. (My project is due in two weeks and my supervisor said, 'stop the leakage or fail'...)
you will have to make a loop in udf using "begin_c_loop(c,t) / end_c_loop(c,t)" and mark them in each time step.
pravin.iitk is offline   Reply With Quote

Old   March 8, 2012, 08:58
Default
  #12
New Member
 
Torres
Join Date: Mar 2012
Posts: 9
Rep Power: 14
cz5224043 is on a distinguished road
Quote:
Originally Posted by pravin.iitk View Post
you will have to make a loop in udf using "begin_c_loop(c,t) / end_c_loop(c,t)" and mark them in each time step.
That makes a lot of sense. I'll try to go through relevant sections in the Fluent UDF manual and see if I can figure it, but still want to see your UDF.

Thanks for being so helpful. I appreciate it.
cz5224043 is offline   Reply With Quote

Old   March 13, 2012, 08:32
Default
  #13
New Member
 
Torres
Join Date: Mar 2012
Posts: 9
Rep Power: 14
cz5224043 is on a distinguished road
Quote:
Originally Posted by pravin.iitk View Post
It was working well when pressure difference around the seal was less but when pressure diff was increasing it started leaking again so I had to manipulate the coefficient in the source term to increase when pressure difference is increasing.
I have that file somewhere in my external hard disk. I'll look for it and let you know.
Hi Pravin,

How are you? I have been trying to figure out the way to import the momentum source, however, no progress.
I really really need your help. If possible, can I have your email address? I will be very grateful.
Thank you very much.
cz5224043 is offline   Reply With Quote

Old   March 13, 2012, 09:53
Default
  #14
New Member
 
Pravin Gangwar
Join Date: Mar 2010
Location: Madrid, Spain
Posts: 7
Rep Power: 16
pravin.iitk is on a distinguished road
Quote:
Originally Posted by cz5224043 View Post
Hi Pravin,

How are you? I have been trying to figure out the way to import the momentum source, however, no progress.
I really really need your help. If possible, can I have your email address? I will be very grateful.
Thank you very much.
Actually port of my external is broken so I have to get it fixed only after tat I can send you momentum source file I wrote. By thet way I have one when it started working so I'll send you that one. my email address is pravin.gangwar@gmail.com
pravin.iitk is offline   Reply With Quote

Old   March 13, 2012, 10:02
Default
  #15
New Member
 
Torres
Join Date: Mar 2012
Posts: 9
Rep Power: 14
cz5224043 is on a distinguished road
Quote:
Originally Posted by pravin.iitk View Post
Actually port of my external is broken so I have to get it fixed only after tat I can send you momentum source file I wrote. By thet way I have one when it started working so I'll send you that one. my email address is pravin.gangwar@gmail.com
Thanks for the reply. I have sent you an email, please have a look.
cz5224043 is offline   Reply With Quote

Old   March 27, 2013, 05:40
Default
  #16
New Member
 
Aleksei
Join Date: Mar 2013
Posts: 2
Rep Power: 0
krispi90 is on a distinguished road
how to use udf set the seal in the engine wankel please
krispi90 is offline   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
CFD Design...The CFD Future John C. Chien Main CFD Forum 20 November 20, 2015 00:40
CFD model of diesel engine Suraj Chetry 08 Main CFD Forum 0 April 24, 2011 02:31
CFD and Engine design varun Main CFD Forum 3 June 29, 2005 17:52
CFD JOBS and Expected Salary.... Noel Harrison Main CFD Forum 11 November 22, 2000 08:15
ASME CFD Symposium, Atlanta, 22-26 July 2001 Chris R. Kleijn Main CFD Forum 0 August 1, 2000 11:07


All times are GMT -4. The time now is 12:01.