Dynamic scaling design strategy of discontinuous bolted rotor systems based on bidirectional parameter mapping

Rods fastened rotor system are widely used in heavy-duty gas turbines. The contact nonlinearity and discontinuity induced by bolted rotor structures, make it difficult to design a scaled rotor system accurately. Thus, a dynamic scaling design strategy for discontinuous bolted rotor systems is proposed in this paper. An improved continuous modeling method considering rods deformation based on equivalent material layer (EML) is introduced to reflect the weakening effect of the rotor stiffness with bolted structure, and the parameter mapping relationships between the continuous and the discontinuous structure are constructed. The scaling factors of each element of the rotor system are derived by the similarity theory. Through this approach, a discontinuous rotor system can be scaled, demonstrating a high level of consistency with the prototype in terms of natural frequencies, critical speeds as well as frequency response. In addition, modal experiments under different preloads and dynamic acceleration experiment are carried out to verify of the proposed modeling method for discontinuous rotor structures. The testing and simulation results prove that the introduced equivalent material layer reflects the contact effect of prototype accurately. Compared with the experimental results, the maximum deviation of the first two natural frequencies is 4.06%, and the maximum deviation of the critical speeds is 1.36%, demonstrating the potential of small size, low-cost scaled models for predicting the complex dynamic characteristics of the prototype rotor system. Overall, the proposed scaling design strategy provides practical guidance for the design and manufacture of the discontinuous scaled rotor systems, which has broad application in testing, fault prediction and dynamic design of prototypes.