Balancing of flexible rotors without trial weights based on finite element modal analysis

With the continuous improvement of aviation engine performance, the engine rotor’s working speed is above the first critical speed, and some small engine rotor’s operating speed exceeds the second critical speed, thus most of the aircraft engine rotor is now flexible rotor. The primary goal of this research is to provide a new method without trial weights for flexible rotor balancing, which is based on the traditional modal balancing method and combines the dynamic characteristics of the rotor, such as the model shape, obtained by using finite element analysis software, the critical speed, the modal damping ratio, and so on. To demonstrate the validity and accuracy of the new method, two experiments are carried out. One is on a four-disk simply supported structure rotor experiment, which is balanced by using three balancing planes. After balancing the amplitude of the rotor through the first critical speed is reduced 80%. The other is on a turboshaft engine power turbine rotor which had been balanced quite well. The initial amplitude of the turboshaft engine power turbine rotor is 0.05 mm when it rotates at low speed, and the maximum amplitude is just 0.12 mm when it rotates at the first critical speed. After balancing the amplitude of the rotor through the first critical speed is reduced to 0.06 mm. The results of the experiments indicate that the new without trial weights method is a significant effective method for the flexible rotor dynamic balancing, and it will be widely used to balance the engine rotor.