# Effect of Impact and Bearing Parameters on Bird Strike with Aero-Engine Fan Blades
## 5 Conclusions  
To investigate the effect of a bird's impact parameters on the aero-engine fan operation and blade damage, an SPH bird model based on a real mallard was used in this paper to simulate the process of bird impact. Six parameters (initial bird velocity, bird orientation, impact location, fan rotational speed, fan hub stiffness, and fan hub damping) have been considered in the simulation. Some conclusions are listed below:  
1. Decrease in impact height increases stress level and impact force. In other words, the impact on the blade root is more dangerous compared to the impact on the blade tip or the middle part. The bird strike causes plastic deformation in the blade, leading to an increase in the bearing force to values as high as 211 kN. The maximum bird impact force reaches a peak of 390 kN when the bird impacts the blade root.
2. The bird impact force, kinetic energy loss of the fan, bearing force, and stress distribution are easily influenced by the impact orientation. Furthermore, the maximum impact force and bearing forces are generated when the bird impacts the fan from the Z-45\({}^{\circ}\) orientation, the maximum force reaching 215 kN and the energy loss reaching 64.73 kJ. Therefore, it can be concluded that the orientation where the bird head is tilted 45\({}^{\circ}\) horizontally is the most damaging scenario for the bird strike.
3. The results show that the bird's initial velocity affects blade integrity, while the fan's rotational speed affects rotor stability. Increasing the bearing stiffness enhances the bearing force that can be provided (to values as high as 193 kN,) thus ensuring stable operation of the system in the bird strike event. The value of damping has little effect on the bird strike process.
4. It can be predicted that the change in the impact parameters will lead to an obvious variation of stresses, which may cause the stress concentrated area to undergo large deformation and even fracture. The damage to the engine varies greatly with different impact locations and orientations, and the results could guide the design of test conditions. With an understanding of the effects of impact and bearing parameters,  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Case** & **G** & **S1** & **S2** & **D1** & **D2** \\ \hline Initial bird kinetic energy (kJ) & 25.59 & 25.59 & 25.59 & 25.59 & 25.59 \\ End bird kinetic energy (kJ) & 82.75 & 82.92 & 82.99 & 82.90 & 82.91 \\ Kinetic energy gain (kJ) & 57.16 & 57.33 & 57.40 & 57.31 & 57.32 \\ \hline \hline \end{tabular}
\end{table}
Table 8: The change in the kinetic energy at different support stiffness and damping.  
the bird strike model can also be used to simulate flocking bird strikes to study bird strike scenarios closer to the actual situation.  
Conceptualization, B.W. and J.Z.; methodology, B.W., R.H. and J.L.; software, B.W. and G.Z.; validation, B.W., J.Z. and Z.L.; resources, R.H. and J.L.; data curation, J.L.; writing--original draft preparation, B.W.; writing--review and editing, R.H. and M.A.; supervision, Z.L.; project administration, J.Z.; and funding acquisition, G.Z. All authors have read and agreed to the published version of the manuscript.  
This work was supported by joint funds of the National Science Foundation of China and the Civil Aviation Administration Foundation of China (U1833108).  
Not applicable.  
The data presented in this paper are available on request from the corresponding author.  
The authors wish to especially acknowledge the contributions of [PERSON] of Tianjin University and [PERSON] of Midea Group.