撞击位置与风扇转速对鸟撞过程的影响

Abstract

Bird impact on fan blades poses a serious threat to the operational safety of aircraft engines.In this study, a real bird model of mallard duck was developed using the smooth particle hydrodynamics method based on a CT scan of a mallard duck.The accuracy of the real bird model was verified by comparing the simulation results of the impact on a plate of real bird model and simplified traditional bird model with the results of Wilbeck's tests.The transient impact responses of bird body and fan blade as the bird was striking a static and a rotating fan blade were comparatively analyzed.To study the effect of fan rotational speed on the bird-impact process, 836r/min, 1984r/min, 3344r/min, and 3772r/min were selected as fan rotational speed.To study the effects of impact location on the bird-impact process, 1/6, 2/6, 3/6, 4/6 and 5/6 of the blade height were selected as impact locations.The results show that blade rotation has a direct impact on the number of bird block cuts, the mass of a single bird block, and the number of impacted blades.Without considering the blade rotation conditions, the contact force, blade root stress, and blade leading edge stress are significantly lower than that when the blade rotation conditions are considered, which makes the prediction of blade stress and damage conservative and inadequate for use in the design of blade strength.Therefore, the blade rotation motion should be considered in the study of bird impact.The interaction mode between the bird and blade at 836r/min speed obviously differs from that at other rotational speeds.The kinetic energy of the bird decreases at a rotational speed of 836r/min, and increases at other rotational speeds, and the increment of the kinetic energy of the bird increases with increases in rotational speed.The leading-edge peak stress at 836r/min is greater than that at 1984r/min;at other rotational speeds, the peak stress of the leading edge increases with increases in the rotational speed.The contact force and blade root stress increase with increases in the rotational speed.With increases in the impact height, the contact force, kinetic-energy increment of the bird body, peak stress of the blade root, kinetic energy of the bird body, and the stress on the leading edge of blade all increase first and then decrease under the combined action of the relative velocity of the impact point and twist angle of the blade.The peak stress of the leading edge and the increment of the kinetic energy of the bird are greatest when impact occurs at 3/6 blade height, and the peak stress of the blade root and the contact force are greatest when impact occurs at 4/6 blade height.