An Assembly Method for the Multistage Rotor of An Aero-Engine Based on the Dual Objective Synchronous Optimization for the Coaxality and Unbalance

Abstract

The assembly quality of an aero-engine directly determines its stability in high-speed operation. The coaxiality and unbalance out of tolerance caused by improper assembly may give rise to complicated vibration faults. To meet the requirements of the dual objective and reduce the test cost, it is necessary to predict the optimal assembly angles of the rotors at each stage during pre-assembly. In this study, we proposed an assembly optimization method for a multistage rotor of an aero-engine. Firstly, we developed a coordinate transmission model to calculate the coordinates of any point in the rotors at each stage during the assembly processes of a multistage rotor. Moreover, we proposed two different pieces of assembly optimization data for the coaxiality and unbalance, and established a dual objective evaluation function of that. Furthermore, we used the genetic algorithm to solve the optimal assembly angles of the rotors at each stage. Finally, the Monte Carlo simulation technique was used to investigate the effects of the geometric measured errors of each rotor on the proposed genetic algorithm. The simulation results show that the process of the dual objective optimization had good convergence, and the obtained optimal assembly angles of each rotor were not affected by the geometric measured errors. In addition, the dual objective optimization can ensure that both the coaxiality and unbalance can approach their respective optimal values to the most extent, and the experimental results also verified this conclusion. Therefore, the assembly optimization method proposed in this study can be used to guide the assembly processes of the multistage rotor of an aero-engine to achieve synchronous optimization for the coaxality and unbalance.

A Vibration Suppression Method for the Multistage Rotor of an Aero-Engine Based on Assembly Optimization

“…where C n refers to the coordinate vector of the geometric center of the assembly rabbet of the rotor at the nth stage after assembly. J Cn is the intersection point between the axis of rotation and the normal plane passing through C n , and its solution principle is the same as that of Equation (25). θ Cn-1 is the angle between the vertical vector from C n to the axis of rotation and the vertical vector from E 1 to the axis of rotation, which can be obtained by Equation (30) as follows:…”

“…To solve this problem, Chen et al [24] introduced the calibrated angles of screw holes into the error transfer model and proposed a reverse assembly method, which decomposed the assembly process of adjacent rotors into three steps: alignment, rotation, and translation. Chen et al [25] further transformed the continuous variables of the assembly angles of each rotor into the discrete variables composed of assembly screw holes and obtained the corresponding optimal relationship of the screw holes directly without secondary calculation. The influence of the geometric measurement errors on the stability of assembly optimization was also investigated by the Monte Carlo method.…”