ABSTRACT
Rotating flexible shafts carrying multiple flexible bladed discs are the core component of gas turbines. Due to the ever more flexible nature of shafts and discs in modern applications, dynamic coupling of shafts and discs is becoming more common. Traditional analysis assumptions of rigid discs on flexible shafts, and flexible discs on rigid shafts, are no longer valid, and a combined analysis is needed. It is well known that disc/blade zero and one Nodal Diameter (ND) modes can couple with shaft axial and bending modes respectively, but a previous work by the authors has shown that a third coupling behaviour between shaft bending and disc 0ND modes exists in the presence of an asymmetric axial-radial bearing supporting structure.
This paper investigates the previous findings in a much more realistic configuration, adding a flexible bladed disc with variable stagger angle to the analysis. The results show that, in the presence of an axial-radial coupled bearing support on the shaft, both shaft axial and bending modes can combine with blade 0ND and 1ND modes into “fully coupled” modes involving all these vibrating patterns. In addition, the blade stagger angle can lead to a further coupling behaviour of these new “fully coupled” modes with shaft torsion.
