Abstract
The fundamental dynamics of a single rotor are very well understood, and extensively covered in the literature. However, many rotating machines such as aircraft engines consist of multiple shafts, which are often directly coupled by inter-shaft bearings. This paper aims to provide better insight into the underlying dynamics of such systems by analysing a simple but representative model of a rigid dual-rotor system. The modes and natural frequencies were computed numerically and it was found that the different modes could be classified by the following criteria: (i) relative phase of the motion of each rotor, (ii) whirl direction of the rotors, and (iii) presence of rotational or translational motion. The high-speed mode shapes could also be classified into (i) “static” modes with very low frequencies, (ii) “flat” modes which tend towards constant frequencies, and (iii) “precessional” modes which have a frequency which linearly increases with speed. A parameter study was performed in order to obtain a better understanding of the sensitivity of the modal properties. It was found that increasing the inter-shaft bearing stiffness can raise the natural frequencies of the modes at low speeds as well as the critical speeds, but has less influence at high speeds. The speed ratio influences the whirl direction of the modes and hence plays a crucial role in determining how each mode varies with speed. Since the speed ratio also controls the frequency of excitation from unbalances, it has a particularly profound effect on the critical speeds, and extra ones can arise. The importance of considering the dynamics of the complete system in the design of turbomachinery with multiple-shafts was highlighted.
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References
Friswell, M.I., Penny, J.E.T., Garvey, S.D., Lees, A.W.: Dynamics of Rotating Machines, 1st edn. Cambridge University Press, Cambridge (2010)
Muszynska, A.: Rotordynamics, 1st edn. CRC Press, Boca Raton (2005)
Childs, D.W.: A modal transient rotordynamic model for dual-rotor jet engine systems. J. Eng. Ind. 98, 876 (1976)
Glasgow, D.A., Nelson, H.D.: Stability analysis of rotor-bearing systems using component mode synthesis. J. Mech. Design 102, 352 (1980)
Gupta, K., Gupta, K.D., Athre, K.: Unbalance response of a dual rotor system: theory and experiment. J. Vib. Acoust. 115(4), 427 (1993)
Fang, H., Yang, B.: Modelling, synthesis and dynamic analysis of complex flexible rotor systems. J. Sound Vib. 211, 571–592 (1998)
Chiang, H.W.D., Hsu, C.N., Jeng, W., Tu, S.H., Li, W.C.: Turbomachinery dual rotor-bearing system analysis. In: Turbo Expo 2002, Parts A and B. ASME, vol. 4, pp. 803–810 (2002)
Ferraris, G., Maisonneuve, V., Lalanne, M.: Prediction of the dynamic behavior of non-symmetrical coaxial co- or counter-rotating rotors. J. Sound Vib. 195, 649–666 (1996)
Gupta, K., Kumar, R., Tiwari, M., Prakash, O.: Effect of rotary inertia and gyroscopic moments on dynamics of two spool aeroengine rotor. In: ASME 1993 International Gas Turbine and Aeroengine Congress and Exposition, Cincinnati, p. V002T12A010 (1993)
Ginsberg, J.H.: Mechanical and Structural Vibrations: Theory and Applications, 1st edn. Wiley, New York (2001)
D’Errico, J.: Consistently Sorted Eigenvalue and Eigenvector Sequences. http://uk.mathworks.com/matlabcentral/fileexchange/22885-eigenshuffle. [Online; Accessed: 19 Sept 2017]
Jei, Y.G., Lee, C.W.: Does curve veering occur in the eigenvalue problem of rotors? J. Vib. Acoust. 114, 32 (1992)
Acknowledgements
The authors gratefully acknowledge EPSRC and Rolls-Royce plc. for funding this work and granting permission for its publication.
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© 2019 The Society for Experimental Mechanics, Inc.
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Haslam, A.H., Schwingshackl, C.W., Rix, A.I.J. (2019). Analysis of the Dynamic Response of Coupled Coaxial Rotors. In: Di Maio, D. (eds) Rotating Machinery, Vibro-Acoustics & Laser Vibrometry, Volume 7. Conference Proceedings of the Society for Experimental Mechanics Series. Springer, Cham. https://doi.org/10.1007/978-3-319-74693-7_6
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DOI: https://doi.org/10.1007/978-3-319-74693-7_6
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