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-   -   Simulation of surge and stall for Rotor 37 (https://www.cfd-online.com/Forums/cfx/115362-simulation-surge-stall-rotor-37-a.html)

Cedric March 28, 2013 23:32

Simulation of surge and stall for Rotor 37
 
Hi, dear friends~~
I'm doing a simulation of surge and stall for rotor 37 using the CFX , but I don't know how to set the boundary conditions,can anyone so kind to give me some advice?

Thanks in advance!

ghorrocks April 1, 2013 18:45

Have you read the best practices guide for turbomachinery? It is part of the CFX documentation.

Cedric April 17, 2013 21:57

Quote:

Originally Posted by ghorrocks (Post 417706)
Have you read the best practices guide for turbomachinery? It is part of the CFX documentation.

Yeah,I have read the Turbogrid Documentation on the Rotor37, but I think difficult part is to set the boundary conditions for Rotor37, and for the stage 37. I have tried to set set the Inlet flow rate and outlet static pressure, but the ANSYS CFX-pre always stopped abruptly, saying returning error code1.
Can you give me some advice?
Thank you very much.

ghorrocks April 18, 2013 06:16

Surge and stall are effects with complicated separated flow and you would expect difficult convergence with them. Have a look at the FAQs for hints on getting convergence. Also you are almost certainly not going to get a steady state simulation to converge. It will require a transient approach.

metaliat93 February 16, 2016 14:06

2 Attachment(s)
Quote:

Originally Posted by ghorrocks (Post 421483)
Surge and stall are effects with complicated separated flow and you would expect difficult convergence with them. Have a look at the FAQs for hints on getting convergence. Also you are almost certainly not going to get a steady state simulation to converge. It will require a transient approach.

I can not solve Rotor 37 correctly
Attachment 45223
Attachment 45224

turbo February 16, 2016 17:10

Quote:

Originally Posted by Cedric (Post 421379)
Yeah,I have read the Turbogrid Documentation on the Rotor37, but I think difficult part is to set the boundary conditions for Rotor37, and for the stage 37. I have tried to set set the Inlet flow rate and outlet static pressure, but the ANSYS CFX-pre always stopped abruptly, saying returning error code1.
Can you give me some advice?
Thank you very much.

Irrespective of surge/stall, your inlet BC is wrong. Use (Po,To,flow angle) at inlet and Ps at exit. Using inlet flow rate is only for an incompressible flow CFD.

turbo February 16, 2016 17:12

Quote:

Originally Posted by metaliat93 (Post 585497)
I can not solve Rotor 37 correctly
Attachment 45223
Attachment 45224

Your CFD looks wrong. CFX will predict quite close to test map, especially axial-flow compressors. Find out what went wrong.

metaliat93 February 17, 2016 06:45

Quote:

Originally Posted by turbo (Post 585548)
Your CFD looks wrong. CFX will predict quite close to test map, especially axial-flow compressors. Find out what went wrong.

I check all BC, I don't know where wrong

turbo February 17, 2016 22:13

Quote:

Originally Posted by metaliat93 (Post 585634)
I check all BC, I don't know where wrong

If your mesh, BC and solver settings are OK, then look into all the geometry including tip clearance.

metaliat93 February 18, 2016 03:18

5 Attachment(s)
Quote:

Originally Posted by turbo (Post 585777)
If your mesh, BC and solver settings are OK, then look into all the geometry including tip clearance.

My domaines: stator+rotor+stator
Attachment 45288

BC on inlet
Attachment 45289

BC on outlet
Attachment 45290
Pout = 105000 [Pa] then was veriable in serial solvering

Settings
Attachment 45292
Attachment 45291

turbo February 18, 2016 14:54

It looks you do not have rotor tip clearance, and then you are losing more trust in the prediction.
What interface models were you using on the two interfaces? You don't have to go with two stationary domains.

metaliat93 February 19, 2016 03:07

1 Attachment(s)
Quote:

Originally Posted by turbo (Post 585908)
It looks you do not have rotor tip clearance, and then you are losing more trust in the prediction.
What interface models were you using on the two interfaces? You don't have to go with two stationary domains.

Attachment 45312 this is settings on interface.
Why I don't must use two stationary domaine. I think that need to have domaine to remove influence outlet condition.
Shrout tip only give loss of parametrs.

turbo February 20, 2016 10:16

I assume you used the same stage interface upstream of rotor. No tip clearance simulation should predict even higher pressure ratio and efficiency than test. But yours did not. Where and how did you get the pressure ratio and efficiency on the curve? Only a single R1 is enough to simulate the rotor only case.

metaliat93 February 22, 2016 04:42

1 Attachment(s)
Quote:

Originally Posted by turbo (Post 586079)
I assume you used the same stage interface upstream of rotor. No tip clearance simulation should predict even higher pressure ratio and efficiency than test. But yours did not. Where and how did you get the pressure ratio and efficiency on the curve? Only a single R1 is enough to simulate the rotor only case.

I think that simulation without tip clearance must to get results higher that in exper, but you can see it lower. Of course I will solving with tip in a future, but Can not understant why get this results.
I use shot rotor domaine because want to get high results of effenciency, a long rotating gas channel raise length movements of gas, so it is raise gidravlic loss.
I get Pr Rt and EFF on boundary of rotor and stator domaines
Attachment 45360

turbo February 22, 2016 13:51

You should get mass-averaged PR and total absolute temperature at the same location where the test data were obtained. Even in R1 only domain you can set a non-rotating hub area as you want. Again you need to repeat the no-tip-clearance simulation until you get higher performance than test. Clearly your prediction will not be seen in any other CFDs.

metaliat93 February 24, 2016 16:29

5 Attachment(s)
Quote:

Originally Posted by turbo (Post 586327)
You should get mass-averaged PR and total absolute temperature at the same location where the test data were obtained. Even in R1 only domain you can set a non-rotating hub area as you want. Again you need to repeat the no-tip-clearance simulation until you get higher performance than test. Clearly your prediction will not be seen in any other CFDs.

Ok, understant you. Build without inlet and outlet stationar domaine, only rotating.
Attachment 45445
Attachment 45446
thats me setting on the inlet

Attachment 45447
setting of domaine

Solved with shroud tip (turn on doble precision)
Attachment 45448
RMS

Attachment 45449
eff politropic and isoentropic (lower that in exp)

metaliat93 February 24, 2016 16:31

1 Attachment(s)
Quote:

Originally Posted by turbo (Post 586327)
You should get mass-averaged PR and total absolute temperature at the same location where the test data were obtained. Even in R1 only domain you can set a non-rotating hub area as you want.

Attachment 45450
massflow at the outlet

turbo February 25, 2016 12:49

Inlet and outlet domains in Turbogrid will let you specify a non-rotating hub in CFX. Every residual needs to be less than 1.0e-5. You need to identify what was the hot tip clearance in the test and what position test map was measured at.

metaliat93 May 27, 2016 01:58

Quote:

Originally Posted by turbo (Post 586856)
Inlet and outlet domains in Turbogrid will let you specify a non-rotating hub in CFX. Every residual needs to be less than 1.0e-5. You need to identify what was the hot tip clearance in the test and what position test map was measured at.

again, I do all what you wrote before but, have not got a good results. Can you send in info about meridional position Rotor wheel Rotor 37?


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