Vibration Mechanism Analysis and Structure Improvement of Engine Thin-walled Tail Nozzle

To solve the problem of local high frequency vibration during test and operation for thin-walled tail nozzles of aero-engine, on the basis of mechanical vibration theory and finite element method, the vibration characteristics of the thin-walled tail nozzle were analyzed by the three-dimensional finite element simulation method, the low-order natural frequency, vibration mode, and relative vibration stress were obtained. On the basis of the working speed and related exciting factors, through the analysis of frequency margin and the drawing of Campbell diagram, the cause of vibration resonance was found out. By considering the structure and loading characteristics of the thin-walled tail nozzle, several improvement schemes were proposed to increase the natural frequency and avoid the low-order harmful resonance. Through simulation calculation and comparative analysis, according to practical engineering experience and the limitation of overall aerodynamic performance, the local truncation scheme was obtained as the optimal improvement scheme. The analysis showed that, the proposed optimal plan is a very effective method to improve the low-order natural frequency, which could not only improve the low-order natural frequency effectively and without weight increasing, but also have little effect on the overall aerodynamic performance. The results could provide theoretical basis and technical guidance for the design and structural optimization of large-size thin-walled components of aero-engines.