Rotor dynamic layout of a multiple disc coupling applied in a turbo drive line

A newly designed drive line should be equipped with a multiple disc coupling between the turbine and the turbo compressor. For the design of this coupling, special attention must be paid to the rotor dynamic behavior of the complete drive line.

For this analysis, the rotor dynamic simulation software RODY was applied. This software was developed by ISMB in order to extend the functionality of NX I-DEAS by the influence of gyroscopic effects. Additionally, the rotation speed dependence of the stiffness and damping matrices of the bearings are considered, which in general are non-symmetric.

Frequency and damping maps of the speed dependent vibration modes are created as shown in the mid and bottom figure. Additionally, run-up curves for various excitation mechanisms are investigated. The complex mode shapes as well as the operating deflection shapes and the frequency response functions can be exported to NX
I-DEAS for animation and further analyses.

At first the turbine and the turbo compressor were considered as separate components. The equivalent rotor dynamic results obtained by the customers were exactly reproduced.

Subsequently, the coupling was integrated into the FEA model as shown in the top figure. It appeared that the coupling significantly influences the natural frequencies and especially the damping behavior of the complete drive line already far below its first bending-critical speed.

By a targeted optimization of the coupling spacer and its connection adapters, a coupling design was developed so that all transversal modes of the drive line with natural frequencies near the operation frequency range are sufficiently damped. Additionally no torsional natural frequency is located within the operating frequency range.