Abstract
The thermal deformation of a flexible rotor system in a high-temperature environment causes changes in the inherent and vibration characteristics. A theoretical model of the flexible rotor was established based on the theory of thermal deformation, the assumed mode method, and the Lagrangian principle. The mode natural frequencies and shapes were explored in detail when the temperature of different nickel-based alloy rotor blades increased gradually (from 0 to 1200°C). The changes in the unstable speed points as the temperature gradually increased were studied based on the rotation speed–frequency diagram. In addition, experimental methods were performed. Mode and steady-state speed tests in a supported state were conducted. Mode experiments were completed on a five-blade rotor test rig with a thermal insulation device, and the acceleration frequency-domain signal showed that the natural frequency decreased with increasing temperature. Through steady-state speed experiments, it was found that the position of the unstable speed points moved forward, and the displacement amplitude increased after local heating.
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