Field balancing of flexible rotors without trial runs using the Numerical Assembly Technique

The balancing of flexible rotor-bearing systems throughout multiple critical speeds is one of the most challenging tasks in rotor dynamics. The disadvantage of conventional balancing methods is that they require multiple trial
runs, which are costly and time-consuming. Therefore, flexible rotor balancing methods based on the Numerical Assembly Technique (NAT) have been proposed in recent years, which substitute the measurement of influence coefficients with simulations. The advantages of NAT are that it leads to analytical solutions and is very computationally efficient.
The work aims to validate and improve the utility of NAT for the field balancing of flexible rotors. Therefore, a NAT simulation is used to balance the first two modes of a test bed without trial runs. The internal damping is included with a viscoelastic material model using fractional time derivatives. The mode shapes, eigenvalues and unbalance responses are measured and compared to values calculated with NAT, to show the accuracy of the simulation. The system is successfully balanced using influence coefficients calculated with NAT and a significant reduction of the vibration amplitude is achieved.