Robust design optimization of the vibrating rotor-shaft system subjected to selected dynamic constraints

The commonly observed nowadays tendency to weight minimization of rotor-shafts of the rotating machinery leads to a decrease of shaft bending rigidity making a risk of dangerous stress concentrations and rubbing effects more probable. Thus, a determination of the optimal balance between reducing the rotor-shaft weight and assuring its admissible bending flexibility is a major goal of this study. The random nature of residual unbalances of the rotor-shaft as well as randomness of journal-bearing stiffness have been taken into account in the framework of robust design optimization. Such a formulation of the optimization problem leads to the optimal design that combines an acceptable structural weight with the robustness with respect to uncertainties of residual unbalances – the main source of bending vibrations causing the rubbing effects. The applied robust optimization technique is based on using Latin hypercubes in scatter analysis of the vibration response. The so-called optimal Latin hypercubes are used as experimental plans for building kriging approximations of the objective and constraint functions. The proposed method has been applied for the optimization of the typical single-span rotor-shaft of the 8-stage centrifugal compressor.

► Robust design optimization of the single-span rotor-shaft of the 8-stage centrifugal compressor.
► Determination of the optimal balance between the rotor-shaft weight and its bending stiffness.
► Accounting for the randomness of residual unbalances and journal-bearing stiffness coefficients.
► The optimization approach based on Latin hypercube sampling and kriging approximation technique.
► Structural model consisting of continuous viscoelastic macro-elements and discrete oscillators.