Turbofan Engine Blade Vibration Model Analysis and Design Parameters Effects

The bending vibration and torsion vibration of Titanium blade are considered to build the stiffness matrix and mass matrix. The natural frequency is obtained by solving characteristic equation. By vibration mode experiment we discover that bending vibration occupies the largest proportion in the first 10 vibration modes. All modes are evenly distributed in the frequency domain. The increment of frequency with order is 200-300 Hz. The low frequency vibration is verified to be most important for blade response by stimulated vibration frequency response analysis, including first and second bending vibration and first torsion vibration. By sensitivity analysis we discover that stiffness effect low order vibration more and initial twisted angle has the bigger effect on first three orders modal frequency. The effects of initial twisted angle and chord length on blade vibration character are studied with the finite element method. The results show that frequency of first 3 vibration modes goes down with the increase of twisted angle and chord length ratio. Finally, when initial twisted angle is over 60° and chord length ratio is above 0.75, the effect of vibration factor on blade design can be basically avoided, and the aerodynamics demand can be satisfied.