Modeling Cantilever Branch Structure of Aero-Engine Power Turbine and Analyzing Its Influence

Abstract

In the power turbine component of an aero-engine, there exists a unique cantilever branch structure, on which turbine disks are mounted. Due to the cantilever's characteristics, this structure exhibits a vibration of large amplitude; thus its characteristics need to be studied in detail.In this paper, the motion equations combining the structure and the shaft were deduced; then its vibration mode was given, and the criticl speed was computed; finally the unbalance response of an integrated rotor system was simulated.The calculation results are compared with the simulation results without considering the branch structure.Some key parameters' influences are studied thoroughly, e.g., the branch shaft's length, the flange's offset and the installation orientation. As the results show, the branch structure has a large influence on the vibration mode and critical speed of the rotor system, thus it should not be simplified and ignored in modelling; After adjusting the branch structure's parameters, the characteristics of a vibration mode do not change, and the effects of branch structural parameters on critical speed are closely related to the corresponding vibration mode; the bending stiffness and the critical speed of the rotor system both decreased with increasing branch shaft's length; if reducing the flange's offset and fabricating the branch structure reversely, a sharp increase in the unbalance response of the turbine disc will occur. In conclusion, the dynamical characteristics of the integrated rotor system can be optimized through reasonably designing the branch structure.