Learning Forum

[mhm.luthfi]

Hello, I have done an experiment related to the hydro turbine and I used rope brake dynamometer to measure stall torque by adding a load little by little thus decreasing the rotational speed. I want to validate this result in ansys fluent software by using report -> forces but my torque always increases every time I increase the RPM. How to get the right value of stall torque which is comparable with this experiment result?

 

Thank you for your help

Best regards,

Luthfi

[RK]

Hello, 

Go to reports > Moments and make sure the Moment Axis are in line with the rotation center and rotation axis. Another approach is writing a UDF. 

[mhm.luthfi]

Hello Mr. Rahul Kumar,

 

Thank you for your reply and suggestion. How can I set UDF for my case? I'm sorry because I am still new in ANSYS.

 

Best regards

[RK]

Hello, 

Please check the user's guide : Fluent Customization Manual (ansys.com)

[mhm.luthfi]

Thank you Sir,

 

By the way what is the difference between moment axis 1 and -1?

Is it related to the direction of moment (related to the rotation direction or right hand rule) or is it related to the action or reaction force (propeller -1 and turbine 1)?

[Karthik R]

Hello,

This is related to the direction - +ve axis or -ve axis. Please read the user's guide. It contains all these details.

Karthik

[mhm.luthfi]

Hello Sir, I have made sure that the center of moment axis is in line with the center of rotation axis. However, my result is still the same, the torque increased as the RPM increased Sir. Do you know what is other suggestion to get the inversely proportional relation between RPM and torque in ansys fluent Sir?

 

Thank you

[Karthik R]

Hello,

Do you know exactly when it should stall? Is this from an experiment or from literature? Are you absolutely sure that you are simulating the exact conditions? Also, what is your convergence like?

Karthik

[mhm.luthfi]

Hello Sir

 

In my case, based on the experiment I have conducted, the turbine will stop when the load in the rope brake dynamometer is around 1,4 kg with the reading of another scale around 0,2 kg. If this is converted to Torque, it's around 0,11 Nm. And from this experiment too, when the load is added gradually (thus the torque is increase gradually too), the rotation speed decreased. So the relation between RPM and torque in my case is always inversely proportional until the rotor cannot handle the load anymore. However, in my simulation, the torque is always increasing whenever the rotational speed is added to the input parameter.

 

I don't know how to model the torque that has the same manner like the experiment result.