Investigation of the autorotation stability of a turbofan engine with a detached fan blade

Sergey Filipkovskij, Valentin Chigrin, Alexandr Soboliev, Yevgeny Vasilevskij, Nikolay Topal, Larisa Filipkovska

Abstract


One of the requirements for the aircraft being designed is the ability to continue flying and landing if one engine fails. One of the calculated cases of engine failure is the separation of the fan blade. This phenomenon causes large vibrations in both the engine itself and the aircraft structure. A calculation model and method for studying engine oscillations with damage in the form of blade separation have been developed. Numerical studies of the oscillations of the engine suspended on a pylon were conducted. The operation of an engine with an unbalance of the fan after switching off during the transition to autorotation is considered. Numerical simulation was performed using the ANSYS Workbench package. The front supports of the rotors are ball bearings installed in the elastic elements of the "squirrel cage". Ball bearings are modeled as a rigid hinge. There are two thin-walled shells, which are intermediate power elements outside the elastic element. With an increase in the imbalance of the fan rotor, the gap in the oil damper closes, the damper housing sits on the shells, switching on their rigidity to work. Thus the support stiffness characteristic is bilinear. The stiffness coefficients of the elastic element "squirrel cage" and the shells of the front support are determined by numerical simulation. The fan rotor is modeled as a rigid body on bearings. The motor stator is modeled by a rigid body on an elastic suspension. The pylon and elements of the elastic suspension of the engine are modeled by beams of variable section, working simultaneously in tension, torsion, and bending. Numerical analysis of the transient oscillations of the D-436-148FM engine mounted on the pylon of the AN-178 aircraft was performed. The amplitude-frequency response of oscillations is obtained in the frequency range below the fan speed in the cruising mode. The stability of engine oscillations at a resonant frequency close to the autorotation frequency has been studied. The results of the numerical simulation are presented in the form of diagrams. Orbits of the centers of gravity of the fan rotor and the motor casing in the resonant mode are constructed. Poincaré mappings of oscillations of the same points of the structure are also constructed.

Keywords


engine; rotor damage; unbalance; vibration; numerical simulation; autorotation

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References


Certification Specifications and Acceptable Means of Compliance for Large Aeroplanes CS-25. Amendment 14. 19 December 2013. 919 p. Available at: https://www.easa.europa.eu/sites/default/files/dfu/CS-25%20Amendment%2014.pdf. (accessed 11.03.2023).

Luo, G., Ma, C., Chen, W., Liu, L. & Zhao, Z. Transient Analysis and Safety Assessment of Turbofan Engine Structures during Bird Ingestion. International Journal of Aerospace Engineering, 2020, vol. 2020, Article ID 7404587, pp. 1–17. DOI: 10.1155/2020/7404587.

Badshah, S., Naeem, A., Rafique, A., Haq, I. & Malik, S. Numerical study on the critical frequency response of jet engine rotors for blade-off conditions against bird strike. Applied Sciences, 2019, vol. 9, iss. 24, article no. 5568, pp. 55-68. DOI: 10.3390/app9245568.

Zhoua, Y., Suna, Y. & Huang, T. Impact responses of slender composite plates for bird-strike testing of fan blades. Latin American Journal of Solids and Structures, 2019, vol. 16, iss. 09, pp. 1-12. DOI: 10.1590/1679-78255809.

Wu, B., Lin, J., Xie, A., Wang, N., Zhang, G., Zhang, J. & Dai, H. Flocking Bird Strikes on Engine Fan Blades and Their Effect on Rotor System: A Numerical Simulation. Aerospace, 2022, vol. 9, iss. 2, article no. 90. pp. 1-19. DOI: 10.3390/aerospace9020090.

Mirabbashi, A., Mazidi, A. & Jalili, M. Analytical and experimental flutter analysis of a typical wing section carrying a flexibly mounted unbalanced engine. Int. J. Struct. Stab. Dyn. 2019, vol. 19, iss. 02, pp. 1–32. DOI: 10.1142/S0219455419500135.

Armendáriza, I., Olarreaa, J. & García-Martínez, J. Engine to wing structural design under critical loads caused by a propeller blade loss. Engineering Structures, 2018, vol. 158, pp. 155-163. DOI: 10.1016/j.engstruct.2017.12.025.

Zafari, E.,·Jalili, M. & Mazidi A. Nonlinear forced vibration analysis of aircraft wings with rotating unbalanced mass of the propeller system. J. Braz. Soc. Mech. Sci., 2020, vol. 42, iss. 218, pp. 1-21. DOI: 10.1007/s40430-020-02297-3.

Martin, C., Quinn, D., Murphy, A., Robinson, T., Thompson, K., Kirkland, F., Cottney, D., Fox, R., Gaskell, J., O'Doherty-Jennings, J. & Martin, C. Understanding Influence of Powerplant Component Connection Strategies on Aircraft Engine Structural Deformations. Journal of Aircraft, 2021, vol. 58, iss. 5, pp. 1083-1093. DOI: 10.2514/1.C036275.

Genta, G. Dynamics of rotating systems. 1st edn. Springer-Verlag, NY, USA, 2005. 674 p.

Muszynska, A. Rotordynamicx. 1st edn. CRC Press, Boca Raton, FL, USA, 2005. 1085 p.

Filipkovskii, S. Joint effect of imbalance and supports vibration on the rotor nonlinear oscillations of an aircraft device. International Journal of Vehicle Structures and Systems. 2017, vol. 9, iss. 5, pp. 288-295. DOI: 10.4273/ijvss.9.5.05.




DOI: https://doi.org/10.32620/aktt.2023.4sup1.02