Reduction of blade vibration stress by vane asymmetry in a high-pressure turbine

In the field of turbomachinery, forced vibrations induced by unsteady aerodynamic forces on blades have a significant impact on fatigue life. Asymmetric vane is an effective design approach to reduce unsteady excitation forces of downstream blades. However, experimental studies indicate that the classical numerical prediction methods for the vibration reduction factor of asymmetric vane need further development and refinement. This paper investigates a 2.5-stage high-pressure turbine, originally designed with uniform inlet guide vanes, where the first-stage rotor blades experienced flow-induced vibration failures during experiments. To address this issue, seven asymmetric vane designs were proposed, including three practical non-uniform vane spacing schemes and four exploratory non-uniform vane camber angle schemes. The time-marching method was used to calculate the full-wheel unsteady flow field and obtain unsteady aerodynamic loads. The modal force method was then employed to compute the vibration stress of the downstream bladed disk excited by the wake. The results demonstrate that asymmetric vane designs can disperse a single resonance point into multiple adjacent resonance points, thereby reducing vibration stress. In the non-uniform vane spacing schemes, the optimal design reduced vibration stress by 47.8% with minimal aerodynamic performance change. In the non-uniform vane camber angle schemes, reducing the camber angle of half vanes effectively lowered the vibration stress of the downstream rotor blades while incurring small aerodynamic performance loss.