Dynamic response of a high speed flexible rotor due to sudden large unbalance

Abstract

Structure vibration response of rotor-bearing-case-installation section system caused by sudden unbalance load due to blade out of the high-speed flexible rotor has been the focus in the field of aero-engine development. This paper deals with the sudden unbalance response characteristics of a high-speed flexible rotor during a blade out event. To reveal the unbalance response influence of blade released mass and rotating speed, a flexible rotor-damping support-protection support system is constructed using LS-DYNA. This model consists of rotor, disk, single blade, protection support and damping support. The diameter of the disk is designed to be 196 mm and the mass of a released blade is 33 or 66 g with two different widths. It can be seen from the shearing stress results that the rotor shaft is twisted off at a weak key point. After single blade out, rubbing between rotor and protection support is classified as the following two stages. It is observed that as single blade released out, higher rotating speed and larger unbalance mass lead to more violent vibration and cause more severe impact force transmitted to bearing and installation section. They can also lead to less stay time during the first stage mentioned above. To verify the results of simulation, blade out tests are carried out on a high speed spin tester. Severe vibration happens on the support base in the course of shutting down, but rotor has no apparent damage in single blade out test with small mass and low speed. However single blade out event with larger mass and higher speed can cause more danger. Large and long-term unbalance on protection support-support base-protection ring-hanger makes the system vibrate severely and these can lead to break of the support base and twist of the rotor shaft. It can be concluded that the results of tests turn out to be agreed well with those of simulation analysis.