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Semi-Analytical Model for High-Speed Rotor Whirl Prediction: An Assumed Modes Formulation for an Axisymmetric Rotor With Non-Uniform Properties

Chatterjee, R and Patel, A and Kumar, N and Kumar, P (2022) Semi-Analytical Model for High-Speed Rotor Whirl Prediction: An Assumed Modes Formulation for an Axisymmetric Rotor With Non-Uniform Properties. In: ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition, GT 2022, 13 - 17 June 2022, Rotterdam.

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Official URL: https://doi.org/10.1115/GT2022-82632


Most fully analytical treatments of rotor whirl are restricted to very simple rotor geometries, and have limited use while studying real-world rotors. Analysis of more complex rotors is routinely carried out in Finite Element software such as Ansys, but this is less effective at generating fundamental insights to inform the design process. This paper is motivated by the ongoing development of a Supercritical-CO2 turbine rotor, and illustrates a rotor model of intermediate complexity. Such a model, given the relative novelty of the turbine design task stemming from the very high rotational speeds required, will improve confidence in rotordynamic simulations and is expected to help with any future troubleshooting. The approach used is to consider the rotor's rigidity and inertia to vary along its length as functions of spatial coordinate x, and obtain predictions of whirl speeds through a Lagrangian formulation with assumed modes. This method can accommodate axisymmetric rotors with variation in cross-section or material properties, or both. It is first demonstrated on a simple and analytically tractable rotor geometry. Then, it is applied to a simplified version of the turbine rotor, whose properties' x-dependence is approximated by curves fit to a small number of datapoints obtained from simpler (non-rotordynamic) simulations. Keywords: Flexible rotor whirl; Campbell diagram; polynomial interpolation; semi-analytical method; Lagrangian, assumed modes. Copyright © 2022 by ASME.

Item Type: Conference Paper
Publication: Proceedings of the ASME Turbo Expo
Publisher: American Society of Mechanical Engineers (ASME)
Additional Information: The copyright for this article belongs to American Society of Mechanical Engineers (ASME).
Keywords: Turbine components, Analytical treatment; Assumed modes; Axi-symmetric rotors; High-speed rotors; Non-uniform; Property; Rotors dynamics; Semi-analytical model; Simple++; Turbine rotor, Lagrange multipliers
Department/Centre: Division of Mechanical Sciences > Mechanical Engineering
Date Deposited: 05 Jan 2023 06:51
Last Modified: 05 Jan 2023 06:51
URI: https://eprints.iisc.ac.in/id/eprint/78741

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