Investigation on the Dynamic Response of a Wide-Chord Fan Blade Under Ground Vortex Ingestion

Abstract

This paper presents a computational study of the dynamic response of the fan blade owing to the excitations from the ingested ground vortex when the turbofan engine is operating on the ground or during the takeoff run. Firstly a numerical method consisting of static, modal and transient analyses is proposed to investigate the dynamic vibration characteristics of a fan blade model with pre-vibration. Modal analysis is conducted to find the critical speed of blade resonances, and the intersection of the fourth engine order and the second bending mode is identified for the study. Secondly, transient analyses of the vortex ingestion are carried out to investigate the resulting blade responses. Various parameters, including different ingestion timings, rotating speeds, ingestion positions and modes of pre-vibration are discussed. Results of dynamic displacement and stress illustrate that the effect of the ingested vortex is significant. Especially when the fan blade is working at the critical speed where engine orders intersect with the dynamic frequencies, the stress is amplified by 276.6% and the displacement is amplified by 156.7%. This paper demonstrates a preliminary method to connect the flow excitations of the ground-ingested vortex and the fan blade vibration characteristics, and provides a helpful reference to the further study of the fan blade vibration.