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

Mrf-turbine blade with mrf

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

Reply
 
LinkBack Thread Tools Display Modes
Old   March 23, 2013, 21:40
Default Mrf-turbine blade with mrf
  #1
New Member
 
Sai
Join Date: Feb 2013
Posts: 7
Rep Power: 3
battersai is on a distinguished road
I am a Master's students in solid mechanics, conducting FSI on turbine blade.I am new to FLUENT.

I know the pressure at inlet (607428.1 pa) and pressure at outlet (249970.4 pa).The temperature at inlet is 1010K.

1)I used an arbitrary static pressure to initialise the solution.It was slightly lower that the total pressure. Is it ok?

2)I have used pressure inlet and outlet, periodic boundary zones, coupled the fluid and solid zones with a shadow wall to enable conjugate heat transfer, used ideal gas equations for air and got results for a stationary blade.I have also set proper interfaces between inlet passage and rotor, rotor and outlet passage.

The blade is rotating at 8000rpm. Can such high velocities be simulated, assuming I gradually increase the speed?

I am guessing that I should set the cellzone velocity in absolute +830rpm,wall shadow ( which has fluid as adjacent zone) as moving wall with a relative zero velocity and axis as rotation as +X. I guess I neednt care about the solid turbine zone at all in rotation.

3)Also, the flow suddenly accelerates to high velocities new outlet, I just need the pressure distribution and velocities near the turbine wall.So doesnt really matter.But if I am to avoid it, how ?

Kindly let me know if I am correct, attached are few pictures.

Thanks a ton in advance








Last edited by battersai; March 23, 2013 at 21:41. Reason: Image wasnt posted
battersai is offline   Reply With Quote

Old   March 25, 2013, 06:08
Default Reply to Sai
  #2
New Member
 
Gowrav Shenoy
Join Date: Feb 2013
Posts: 20
Rep Power: 3
Gowrav is on a distinguished road
Hi,
i will try to answer few.. Mayn't correct too.
asked 8000 rpm high or not.. Numerical Values doesn't make diff in simltn.. It may be high when considern yur design.
Since yu ve mentioned FSI- i hope yur talking about 1 way FSI, you are taking pressure and temperature on blades for the evaluation of stresses along with centrifugal.
If thats the case i feel solid body is not required in fluent.. (Just reduce no of elements). Also coupled wall BC is also not required. Yu can directly take temp/pressure on wall(blade) - to import into structural one.
Since its transient hope yur using sliding mesh, if steady state MRF,MPM will do..
Along with cell zones.. Motion to the mesh/reference need to be mentioned.
There s compressor example given in tutorial much relevant with yur case .. Have a look
Regards
Gowrav
Gowrav is offline   Reply With Quote

Old   March 25, 2013, 08:29
Default
  #3
Far
Super Moderator
 
Far's Avatar
 
Sijal Ahmed Memon (turboenginner@gmail.com)
Join Date: Mar 2009
Location: Islamabad Pakistan
Posts: 3,885
Blog Entries: 6
Rep Power: 37
Far will become famous soon enoughFar will become famous soon enough
Send a message via Skype™ to Far
Use 0 static pressure at oulet and see what happens? what is the operating pressure? I know there is option of average static pressure in newer version, use that option.
Far is offline   Reply With Quote

Old   March 25, 2013, 14:28
Default
  #4
Senior Member
 
Join Date: Apr 2009
Posts: 503
Rep Power: 11
stumpy is on a distinguished road
Need to know more about the FSI before suggestion a solution approach. 1-way? 2-way using System Coupling? Steady or transient? Thermal coupling or force/displacement coupling?
Are you planning on a sliding mesh approach in Fluent (do you care about transient interactions between the blade and stators) or is a mixing plane or frozen rotor approach suitable.
stumpy is offline   Reply With Quote

Old   March 25, 2013, 17:37
Default
  #5
New Member
 
Sai
Join Date: Feb 2013
Posts: 7
Rep Power: 3
battersai is on a distinguished road
Quote:
Originally Posted by Gowrav View Post
Hi,
i will try to answer few.. Mayn't correct too.
asked 8000 rpm high or not.. Numerical Values doesn't make diff in simltn.. It may be high when considern yur design.
Since yu ve mentioned FSI- i hope yur talking about 1 way FSI, you are taking pressure and temperature on blades for the evaluation of stresses along with centrifugal.
If thats the case i feel solid body is not required in fluent.. (Just reduce no of elements). Also coupled wall BC is also not required. Yu can directly take temp/pressure on wall(blade) - to import into structural one.
Since its transient hope yur using sliding mesh, if steady state MRF,MPM will do..
Along with cell zones.. Motion to the mesh/reference need to be mentioned.
There s compressor example given in tutorial much relevant with yur case .. Have a look
Regards
Gowrav
Thank you for your reply Gowrav.
8000rpm is the design speed of the JT8D jet engine, I took the geometry of the blade from JT8D, so took their operating conditions too.
The solid body is required since ANSYS does not allow surface temperature import, only volume temperature import is allowed, so am forced to simulate conjugate heat transfer. Yes, it is 1 way FSI
Its a steady state simulation, not taking transience into account.
I am just concerned about the rotation direction of the fluid. If +x is the axis, is -837 rpm the speed of moving fluid cell zone?
battersai is offline   Reply With Quote

Old   March 25, 2013, 17:38
Default
  #6
New Member
 
Sai
Join Date: Feb 2013
Posts: 7
Rep Power: 3
battersai is on a distinguished road
Quote:
Originally Posted by Far View Post
Use 0 static pressure at oulet and see what happens? what is the operating pressure? I know there is option of average static pressure in newer version, use that option.
Thanks far, for your reply.
Am using 0 operating pressure ( as in the tutorial) so I assume I should try 101325pa at the outlet?
battersai is offline   Reply With Quote

Old   March 25, 2013, 17:41
Default
  #7
New Member
 
Sai
Join Date: Feb 2013
Posts: 7
Rep Power: 3
battersai is on a distinguished road
Quote:
Originally Posted by stumpy View Post
Need to know more about the FSI before suggestion a solution approach. 1-way? 2-way using System Coupling? Steady or transient? Thermal coupling or force/displacement coupling?
Are you planning on a sliding mesh approach in Fluent (do you care about transient interactions between the blade and stators) or is a mixing plane or frozen rotor approach suitable.
Its a steady state, one way FSI, just need the temperature and pressure data for structural simulations. I am not worried about the stator-rotor interactions. I have aligned the inlet to give the flow a tangential velocity to avoid the presence of a stator. hope it is ok.

I am using force and thermal coupling. I am not using a sliding mesh, just MRF. If mixing planes are the interfaces which are created between stator and rotor, yes, I have created them as said in the tutorial.

Thanks for your reply,stumpy.
battersai is offline   Reply With Quote

Old   March 26, 2013, 02:10
Default
  #8
Far
Super Moderator
 
Far's Avatar
 
Sijal Ahmed Memon (turboenginner@gmail.com)
Join Date: Mar 2009
Location: Islamabad Pakistan
Posts: 3,885
Blog Entries: 6
Rep Power: 37
Far will become famous soon enoughFar will become famous soon enough
Send a message via Skype™ to Far
Use zero pressure at outlet and start with lower rpm. The procedure would be :

1. use 0 static pressure at outlet and 2000 RPM

2. Iterate few hundred iterations and increase RPM = 4000

3. Repeat step 4 and increase RPM to 6000 and finally 8000

4. Calculate outlet total pressure if it is lower then increase outlet static pressure.

PS: Use average static pressure if outlet boundary is placed less than 1.5 C downstream
Far is offline   Reply With Quote

Old   March 26, 2013, 17:52
Default
  #9
New Member
 
Sai
Join Date: Feb 2013
Posts: 7
Rep Power: 3
battersai is on a distinguished road
Quote:
Originally Posted by Far View Post
Use zero pressure at outlet and start with lower rpm. The procedure would be :

1. use 0 static pressure at outlet and 2000 RPM

2. Iterate few hundred iterations and increase RPM = 4000

3. Repeat step 4 and increase RPM to 6000 and finally 8000

4. Calculate outlet total pressure if it is lower then increase outlet static pressure.

PS: Use average static pressure if outlet boundary is placed less than 1.5 C downstream
Thanks far.
I completed that part already. Could you please tell me which is the sign of rotation I should give( positive or negative). The axis is +X and blade is rotating in the anti-clockwise direction in front view.
Also , in fluent tutorial for fan, the top wall has been specified as non-moving wall, do you know why ?
battersai is offline   Reply With Quote

Reply

Tags
conjugate heat transfer, mrfzones, rotor blade, turbine

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
Wind Turbine Blade rotation mmd_knr FLUENT 1 August 8, 2012 14:52
Sliding mesh vs MRF in axial turbine simulation Vito FLUENT 3 December 21, 2011 04:57
Calculating lift force of a wind turbine blade problem LittleBart CFX 4 June 29, 2011 02:33
force acting on gas turbine blade.... vvj Main CFD Forum 1 March 3, 2010 01:04
Flow study through Turbine Blade passage Subrata FLUENT 1 May 4, 2007 11:28


All times are GMT -4. The time now is 03:59.