Dynamic behaviour of high- bypass- ratio turbofan carbon fiber-reinforced plastic blade ubder unsteady airloads

The dynamic behavior of vibrating blades of an advanced high- bypass- ratio turbojet engine wide-chord fan under unsteady air loads has been researched. Unsteady air loads occur because of the flow around the impeller situated in the air inlet in the case of strong crosswind. These loads affect the blade dynamic behavior and could lead to increasing of the blade vibration amplitude and the stress in the blades. Blade dynamic behavior is investigated on the basis of 3D high-level gas-dynamic and finite-element models. The gas-dynamic model takes into account unsteady viscous 3D air flows. The strength model takes into account geometrical non-linearity and anisotropy of the composite material. The Cobra software package developed at CIAM and based on Godunov’s method is used for aerodynamic research and obtaining unsteady aerodynamic loads. The ANSYS package of finite-element analysis is used to solve the mechanical problem. The paper deals with both forced vibrations of a blade under given cyclic aerodynamic loads and vibrations with account for the fluid-structure interaction (FSI) of the structure and the flow of titanium and carbon-fiber-reinforced blades. The results of investigations have been compared. The differences between the results of solving the task of forced vibrations and vibrations with FSI, as well as the differences between the results obtained for blades of the same configuration but made of different materials are presented.