Guide vane Pitch change

vortexrope · January 7, 2022, 08:35

Hi,

I am using cfx to model the flow through a Francis turbine model. To be able to transition from best efficiency point to part load i need to impart a motion to the guide vanes so that at guide vane inlet passage is adjusted as desired. How can I implement this pitch change in time?

Opaque · January 7, 2022, 11:34

When you say "pitch change" you refer angle of the vane relative to the rotor, correct? The spacing between the vanes is still the same (number of vanes per 360)

What are you interested on?
1 - Stationary behavior at angle2?
2 - The transient behavior while moving from angle1 to angle2?

Those are two very different goals, and different challenge levels for the simulation.

1 - Just mesh the distributor with vanes at a different angle, re-import that mesh, and run your simulation the same as before for different speeds (narrow range anyways for a Francis runner, correct?). You built a map with your results and you will find the best efficiency point
2 - That is more complex since you need to rotate the vane using mesh motion (which has its own challenges), and you need to run in transient (more computationally demanding).

Did I make any sense above?

vortexrope · January 8, 2022, 06:56

Many thanks for the reply.

Second one is exactly what I wish to do. I want to change the angle of each of the circumferentially arranged guide vanes, say by 4 degrees. This should happen in course of a transient simulation to achieve a change in flow rate through the turbine while the turbine rpm is held constant.

Could you post some resource on how to do this?

January 7, 2022, 08:35	Guide vane Pitch change	#1
vortexrope New Member Faiz Azhar Masoodi Join Date: Apr 2021 Posts: 3 Rep Power: 5	Hi, I am using cfx to model the flow through a Francis turbine model. To be able to transition from best efficiency point to part load i need to impart a motion to the guide vanes so that at guide vane inlet passage is adjusted as desired. How can I implement this pitch change in time?

January 7, 2022, 11:34		#2
Opaque Senior Member Join Date: Jun 2009 Posts: 1,891 Rep Power: 33	When you say "pitch change" you refer angle of the vane relative to the rotor, correct? The spacing between the vanes is still the same (number of vanes per 360) What are you interested on? 1 - Stationary behavior at angle2? 2 - The transient behavior while moving from angle1 to angle2? Those are two very different goals, and different challenge levels for the simulation. 1 - Just mesh the distributor with vanes at a different angle, re-import that mesh, and run your simulation the same as before for different speeds (narrow range anyways for a Francis runner, correct?). You built a map with your results and you will find the best efficiency point 2 - That is more complex since you need to rotate the vane using mesh motion (which has its own challenges), and you need to run in transient (more computationally demanding). Did I make any sense above? __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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January 8, 2022, 06:56		#3
vortexrope New Member Faiz Azhar Masoodi Join Date: Apr 2021 Posts: 3 Rep Power: 5	Many thanks for the reply. Second one is exactly what I wish to do. I want to change the angle of each of the circumferentially arranged guide vanes, say by 4 degrees. This should happen in course of a transient simulation to achieve a change in flow rate through the turbine while the turbine rpm is held constant. Could you post some resource on how to do this?