Bird strikes are one major accident for aircraft engines and can inflict heavy casualties and economic losses. In this study, a smoothed particle hydrodynamics (SPH) mallard model has been used to simulate bird impact to rotary aero-engine fan blades. The simulations were performed using the finite element method (FEM) at LS-DYNA. The reliability of the material model and numerical method was verified by comparing the numerical results withWilberk’s experimental results. The effects of impact and bearing parameters, including bird impact location, bird impact orientation, initial bird velocity, fan rotational speeds, stiffness of the bearing, and the damping of the bearing on the bird impact to aero-engine fan blade are studied and discussed. The results show that both the impact location and bird orientation have significant effects on the bird strike results. Bird impact to blade roots is the most dangerous scenario causing the impact force to reach 390 kN. The most dangerous orientation is the case where the bird’s head is tilted 45° horizontally, which leads to huge fan kinetic energy loss as high as 64.73 kJ. The bird’s initial velocity affects blade deformations. The von Mises stress during the bird strike process can reach 1238 MPa for an initial bird velocity of 225 m/s. The fan’s rotational speed and the bearing stiffness affect the rotor stability significantly. The value of bearing damping has little effect on the bird strike process. This paper gives an idea of how to evaluate the strength of fan blades in the design period.

To study the influence of bird impact position and impact posture on the transient response of a fan blade, a smooth particle hydrodynamics (SPH) mallard model established by CT scanning was used to simulate the process of a real bird strikes a high-speed rotating fan with five different impact positions and fifteen different impact attitudes according to the relative speed principle. The effect of impact position and attitude on the transient stress and displacement of the fan blade was obtained. Results show that during the impact process, stress concentration is likely to occur in the blade root and the leading edge, these areas are most susceptible to damage and deformation, and the anterior root has greater stress than the posterior root, which is more likely to be damaged. The impact force on the blade and the stress at the blade root and the leading edge are the largest when the bird strikes the 2/6 blade height position. In the Y-135°, Y-270°, Y-315°, Z-135° and Z-315° impact postures, the equivalent stress of the anterior root is the largest. In the Z-135 impact posture, the equivalent stress of the posterior root is the largest, and the displacement of the leading edge is the largest in the Y-270° impact posture. The results of this study have reference value for the design of anti-bird impact and airworthiness evaluation of fan blades in aero-engine.

To study the effect of a bird striking engine fan on the rotor system, a low-pressure rotor system dynamic model based on a real aero-engine structure was established. Dynamic equations were derived considering the case of the bird strike force which transferred to the rotor system. The bird strike force was obtained from the bird strike process simulation in LS-DYNA, where a smoothed particle hydrodynamics (SPH) mallard model was constructed using a computed tomog-raphy (CT) scanner, and finite element method (FEM) was used to simulate the bird strike on an actual fan model. The dynamic equations were solved using the Newmark-β method. The effect of rotational speeds on the rotor system dynamics after bird strike was investigated and discussed. Results show that the maximum bird impact force can reach 104 kN at 3772 r/min. Impact time is only 0.06 s, but the bird strike on fan blades lead to a transient shock on the rotor system. Under the action of transient shocks, the rotor system displacement in the horizontal and vertical directions increase sharply, and the closer the mass point is to the fan, the more it is affected; the vibration amplitude at the fan will increase 15 times within 0.1 s of the bird strike and will gradually decrease with the effect of damping. The dynamics of the rotor system changes from a stable single periodic motion to a complex irregular quasi-periodic motion after a bird strike, and the strike force excites the first-order vibrational mode of the rotor system. This phenomenon occurs at all speeds when bird strikes occur. Bird strikes will cause resonance in the rotor system, which may cause damage to the engine. It was also seen that the bird strike force, and hence the effects on the rotor system, increases as the engine rotational speed increases; the peak force is larger and the number of peaks has increased. The impact force at 3772 r/min is 99.5 kN higher than at 836 r/min, and three additional peaks emerged. This effect is more reflected in the amplitude, and the overall vibration characteristics do not change. Combining the bird strike with the rotor dynamics calculation, the dynamic response of the aero-engine rotor system to bird strike is studied at different flight stages, which is of guiding significance for power evaluation of aero engines after bird strike.

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.