Learning Forum

[Paul-Adrian Oprea]

Hello. I'm a beginner in using CFX and I'm having some trouble with the stator-rotor interface in CFX for an axial turbine stage. After simulating, I obtain a sudden drop in Mach number at the inlet of the rotor. I have defined the interfaces between the stator, rotor and rotor outlet with their corresponding surfaces. I also tried the stage avg. velocity constraint, I also defined the connection at Connectivity in CFX-Pre but none of these solved the issue. I used TurboGrid for stator and rotor and then in CFX I used Turbo Mode. Any ideas? This problem also happens at the rotor-outlet interface as can be seen in the picture.

[rfblumen]

I would refer back to your velocity triangles for both the rotor inlet and rotor outlet to understand what you're seeing.  Based on the rotor inlet velocity triangle, the absolute frame velocity is larger than the relative frame velocity, hence a drop in Mach number going between the stationary frame to the rotating frame.

At the rotor exit, based on the rotor outlet velocity triangle, the absolute frame velocity is smaller than the relative frame velocity, hence a drop in Mach number going between the totating frame to the stationary frame.

You can best see this by plotting velocity vectors rather than Mach number.

[Tee Jia Zheng]

Hi I'm a beginner in using CFX and I'm having some trouble with the stator-rotor interface in CFX for an axial turbine. I have no idea why my stator and rotor will crash in CFX. Because of the geometry set in bladegen? If yes then which type of geometry. Thank you for helping me.