Study on the equivalent stiffness of heavy-duty gas turbines composite rotor with curvic couplings & spindle tie-bolts

The difference between the composite rotor with curvic couplings & spindle tie-bolts and integrated one is contact interface. For the discontinuous of contact interface, equivalent stiffness deducted method of composite rotor with curvic couplings & spindle tie-bolts is not the same as integrated rotor. In this paper, the rotor was divided into continuous region and region affected by contact interface. And for the latter, the contact interface bear compression and spindle tie-bolts bear tension under bending moment. A method calculating the position of "neutral layer" and equivalent stiffness was obtained, the results were validated by the working process data of gas turbines. Some factors influencing the stiffness and dynamic characteristics of the rotor such as surface roughness, surface waviness and preload were evaluated. The results show that surface waviness has considerable effect on equivalent stiffness and dynamic characteristics, whereas surface roughness alone has minor effect on dynamic characteristics. The preload also affect equivalent stiffness to some extent, and the effect of preload is especially distinct when machining surface quality is poor, so the stiffness can be improved by increasing preload force. If mating surfaces are well grinded and there is no surface waviness, effect on stiffness of surface roughness can be ignored.