Investigation of Vibration Characteristics of Titanium Wide-Chord Fan Blade
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ORIGINAL PAPER
Investigation of Vibration Characteristics of Titanium Wide‑Chord Fan Blade Zhonglin Wang1 · Yong Chen1,2,3 · Hua Ouyang1,2,3 · Anjenq Wang1,2,3 Received: 19 September 2018 / Revised: 17 April 2019 / Accepted: 20 April 2019 © Krishtel eMaging Solutions Private Limited 2019
Abstract Introduction The vibration characteristics of a wide-chord fan blade affect the safety, reliability, and operability of highbypass ratio turbofan engines. Objectives In this study, the vibration characteristics of a fan blade were investigated using numerical and experimental methods. Methods First, the natural frequencies and mode shapes were obtained and verified. Then, the rotating speed and frequency margins were employed to analyze the stability of the blade. The critical crossings in the Campbell diagram were indicated and evaluated. Next, the strain energy density index and weaklink were used to evaluate the dangerous locations for the highcycle fatigue characteristics of the blade. Finally, single- and multi-axis random-excitation tests were performed. Results Results indicated that low-order bending modes were dominant under circumferential- and axial-direction excitations, while the torsional mode response was higher under radial-direction excitation. The weaklinks for different excitation directions exhibited different characteristics. Conclusions This work presents a comprehensive understanding of the fan-blade vibration and response characteristics. Keywords Wide-chord fan blade · Vibration characteristics · Resonance margin · Weaklink · Multi-axis excitation
Introduction Since the first turbofan engine was developed in the 1960s, the fan-blade design has been updated through many generations to satisfy the increasing demand for performance and economy. Currently, the most widely used fan blades are wide-chord fan blades, including solid metallic, hollow metallic, and composite blades. As the gold standard in aviation, CFM56-7B engines with 24 solid titanium wide-chord fan blades have the best-selling record. Although CFM56 engines have run for hundreds of thousands of hours and their airworthiness has been certified, accidents caused by
* Yong Chen [email protected] 1
School of Mechanical Engineering, Shanghai Jiao Tong University, No. 800 Dongchuan Rd, Shanghai 200240, China
2
Engineering Research Center of Gas Turbine and Civil Aero Engine, Ministry of Education, Shanghai 200240, China
3
Collaborative Innovation Center for Advanced Aero-Engine, Beijing 100191, China
fan-blade failure occurred in 2016 and 2018. Thus, fan-blade vibration is a critical challenge for the safety of engines. Because the turbofan engine is a complicated and integrated system, excitations causing fan-blade vibration arise from various sources. The fan blades are at the front of the engine, and the excitations that come from the inlet are determined by the operating conditions and ambient environment. The aerodynamic excitations include the crosswind, ground vortex, turbulences from the wings and fusela
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