Model updating and validation of a dual-rotor system

Finite element (FE) modeling of structures with three-dimensional (3D) solid elements is often used in order to improve the model fidelity. However, in some cases the model required is extremely complicated, for example the whole engine modeling (WEM) of an aero engine in the design process. A refined WEM including static casings and rotor systems may have a huge number of FE elements with tens of millions degrees of freedom. The dynamic analysis of such models is not only time consuming and expensive but difficult to implement even on the most high performance computers. A simplified one dimensional (1D) model of the rotor system that significantly reduces the size of the model is traditionally used instead of the 3D model, but the analysis precision of such models is generally very poor. In this paper, model updating and validation of the one-dimensional (1D) model of a dual rotor system is introduced using a refined three-dimensional (3D) solid model as a reference. The major errors of the simplified 1D model are determined by comparison of modeling errors between the 1D and 3D models, and the regions of the 1D model required to be updated are selected. Then, first-order based optimization is implemented to update the simplified 1D model using the data simulated from the refined 3D model so that its dynamic prediction agrees with those from the 3D model analysis. Finally, the updated 1D model of the dual rotor system is further used to predict the critical speeds and unbalanced responses. Comparison of the predicted results from the updated 1D model with those calculated from the refined 3D model, shows that the updated 1D model has good accuracy and high efficiency. Therefore, this 1D model can replace the 3D model of the dual rotor system in the WEM dynamic analysis and optimization in the design process to significantly reduce the modeling size and the expenses of computing cost and time.