Improvement of the vibration performance of rod-fastened rotor by multioptimization on the distribution of original bending and unbalance

Manufacturing errors of disks, namely, parallelism error and mass imbalance, cause complex bending and unbalance of rod-fastened rotor (RFR) after assembly, which act as original excitations and increase vibration. A method was introduced in this study to improve the vibration performance of an RFR. The method optimized the distribution of bending and unbalance and offered an improved assembly scheme. As a basic step, the quantitative relation of RFR bending and assembly angles of disks with parallelism errors was established. On this basis, dimensionless bending was proposed to evaluate the integral bending of an RFR. With respect to the unbalance of the RFR, the balance principle of rigid rotor was applied, that is, small equivalent reaction forces were considered better. The dynamic model of an RFR supported by elliptic bearings was established by using finite element method. Optimizations on the bending and unbalance were then performed individually, and related vibration responses of the RFR system were investigated. Results of single optimization on bending and unbalance proved the effectiveness in reducing the vibration responses of the RFR system. Moreover, results revealed that the bending and unbalance induced mainly the vibration of first order, which explained the difficulty to distinguish each other in actual balance of an RFR. Finally, the multioptimization on the bending and unbalance was performed, which greatly decreased the vibration responses of the RFR system. Optimizations on bending and unbalance in this study were independent with supporting conditions, which gave them a better application and provided a new way to improve the dynamic performance before assembly.