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-   -   Need help on calculation of power coefficient for contra-rotating turbine (http://www.cfd-online.com/Forums/cfx/107726-need-help-calculation-power-coefficient-contra-rotating-turbine.html)

 altomos October 4, 2012 23:01

Need help on calculation of power coefficient for contra-rotating turbine

Dear all,

I am making a contra-rotating wind turbine using S822-S823 airfoil.

The turbine is designed for 10kW scale (rotor radius is 3.58m, wind speed is 10m/s)

This is my first work for 3D simulation of turbine, and I use BEM.

My problem is regardless of whatever I set up, meshing... the power coefficient is always unreasonable (please refer to my document here):

So, please guide me how to validate the performance of the turbine, or introduce me any reference that have detailed thoery, study about contra-rotating turbine and its performance analysis.

Thank you very much!

 ghorrocks October 5, 2012 07:08

This is an FAQ: http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F

In your case I see big separations off the blades. If this simulation is at the operating point of a well designed turbine you will not have separations. Something is generating massive separations in your simulation.

 altomos October 5, 2012 11:33

Quote:
 Originally Posted by ghorrocks (Post 385046) This is an FAQ: http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F In your case I see big separations off the blades. If this simulation is at the operating point of a well designed turbine you will not have separations. Something is generating massive separations in your simulation.
Thank you so much Mr, Ghorrocks. When you mention the "separation", you meant the flow pattern? This model I made from a software and has no relation to any actual turbine. It is kind of for study purpose.

By the way, I've checked my Cp calculation again. It's strangle that if I input the formula to CCL, calculated Cp is very low. But if I just extract the torque from blade and then calculate the Cp manually using the same formula, the result is reasonable (Cp = 0.2-0.4)

Anyway, because this is my very beginning of 3D model simulation and study (I used actuator disc method before), can you advice me for any reliable books, deep theory references about the contra-rotating turbine? So that I can create proper model?

 ghorrocks October 6, 2012 08:48

I do not know of any references for contra rotating turbines. Your application is quite specialised and outside my area of expertise.

 altomos October 6, 2012 14:26

Quote:
 Originally Posted by ghorrocks (Post 385200) I do not know of any references for contra rotating turbines. Your application is quite specialised and outside my area of expertise.
Oh, it's OK. Thank you so much for your advice. You've been helping me a lot, Sir.

 ghorrocks October 7, 2012 07:26

But you should be able to find lots on normal single rotor turbines, and if you can model them accurately you are just about there. So I would concentrate on single rotor turbines initially.

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