“Hot modes” of rotor vibrations and vibration reduction design for aero-engines

A concept of “hot modes” of aero-engines rotor was put forward to adapt to the design of rotor dynamics for variable speed operation of aero-engines. The “hot modes” were explained with two different models, and a procedure of rotor dynamics design under “hot modes” was developed. The ratios of critical speeds of rotor with elastic supports to those of the rotor with rigid supports were taken as design parameters for dynamic optimization of the rotor, which involved the influences of stiffness, mass of the rotor. Result shows that, when all “hot modes” are under the first mode of rotor with rigid supports, the critical speeds of the rotor should be lower than the first critical speed of the rotor with rigid supports. If the first “hot modes” under the first mode of rotor with rigid supports, and the second “hot modes” is between the first and the second modes of rotor with rigid supports, the second critical speed should be equal to the root mean square of the first and the second critical speeds of the rotor with rigid supports. Additionally, it is suggested that the residual imbalance should be kept orthogonal to the modes of the rotor with rigid supports.