169 / 2021-03-31 17:00:35

Vibration Characteristics of a Dual Rotor-Blisk-Casing System with Blade Tip Rubbing Fault

dual rotor-blisk-casing system; blade tip rubbing; spring-beam-shell hybrid element; Craig-Bampton method; Lagrangian multiplier method

Rotor dynamics and Robotics

A fully flexible dynamic model of a dual rotor-blisk-casing system with a blade tip rubbing fault is established using the self-programmed spring-beam-shell hybrid element. Special attention is paid to deriving the gyroscopic matrices of a shaft beam element and a disk shell element, respectively. Besides, the penalty method is successfully applied to relate the drilling degree of freedoms to the in-plane components of displacements for a shell element. Then the Craig-Bampton method is utilized to establish the reduced system model step by step for higher efficiency on the premise of ensuring the model precision. Next, the rubbing response characteristics of the system under different rotating speeds, disk unbalances, and rubbing clearances are solved via the central difference method combined with the Lagrangian multiplier method. The results show that (1) when rubbing occurs, the frequency components in the high pressure (HP) compressor mainly include the low pressure (LP) and HP rotating frequencies, odd-multiple LP rotating frequency, and their combination frequencies, while those in the casing are mainly the even-multiple LP rotating frequencies and some side frequencies; (2) the degree of distortion of the axis orbit and phase diagram of the HP compressor can be an indicator characterizing the rubbing severity.