Numerical study on vibration stress of rotating fan blade under aerodynamic load at critical speed

Abstract

The vibration stress caused by resonance is the main cause of failure in aircraft engine blades. The study investigated the vibration stress of a single-stage fan blade influenced by the interaction of aerodynamic and structural behavior at multiple critical speeds. A numerically based analysis through the interfacing of computational fluid dynamics and finite element modeling analysis, referred to as fluid–structure interaction was performed. A three-dimensional finite element model of the blade which was verified by modal test was established to carry out response analysis when blade resonates. A single flow channel model of the blade was constructed to simulate the aerodynamic pressure loads that result in vibration of the fan blades. The Campbell diagram was introduced to determine the critical conditions of the blade. The results show that resonance phenomenon appears for several times between 2000 and 3600 r/min, and further analyses of the blade mode shape as well as dynamic stress at these speeds indicate that vibration stress at critical speed is obviously higher than those at the adjacent speeds. But there is no positive correlation between the peak stress and critical speed, while it is determined by the comprehensive action of critical speed, vibration mode and synchronous excitation. The peak stress distribution is closely linked to the mode shape of the blade, and it always appears at the leading edge and changes along the blade height. It also illustrates that the leading edge of the blade is most prone to vibration fatigue.