Research on the Mechanism of Vibration Response Difference of Turbine Frame

Abstract During the test run of a typical dual rotors aero-engine, there are obvious differences in the high-pressure fundamental frequencies at different measuring points in the circumferential direction on the outer casing of the turbine frame. Therefore, based on the mechanical model of vibration energy transfer of turbine frame, this paper carried out a mechanism study on the change rule of vibration response of frame with geometric mutation, interface connections and pull rod connection, in order to reveal the root cause of the difference of high pressure fundamental frequencies. The results show that: Due to the gap between the bearing outer ring and the bearing seat, the rotational inertia excitation of the rotor has multi frequency/impact excitation characteristics, which make the transmission of vibration energy directional. Because the plate frame is skew, tangential stiffness component exists, resulting in a certain difference in the transmission of vibration energy on the pull rod. And the pretension of the pull rod will change with the operational condition, leading to further exacerbation of the vibration difference. This ultimately reason led to a significant difference in the HP fundamental frequency.