Mode identification of a rotating disk

“…In this case the disk was excited from the stationary frame. Ahn [9] could determine the mode shape of the rotating disk using two stationary sensors. He measured the phase difference between the signals of two proximity probes for this purpose.…”

Section: Introductionmentioning

confidence: 99%

Feasibility of Using PZT Actuators to Study the Dynamic Behavior of a Rotating Disk due to Rotor-Stator Interaction

Presas

Egusquiza

Valero

et al. 2014

Sensors

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In this paper, PZT actuators are used to study the dynamic behavior of a rotating disk structure due to rotor-stator interaction excitation. The disk is studied with two different surrounding fluids—air and water. The study has been performed analytically and validated experimentally. For the theoretical analysis, the natural frequencies and the associated mode shapes of the rotating disk in air and water are obtained with the Kirchhoff-Love thin plate theory coupled with the interaction with the surrounding fluid. A model for the Rotor Stator Interaction that occurs in many rotating disk-like parts of turbomachinery such as compressors, hydraulic runners or alternators is presented. The dynamic behavior of the rotating disk due to this excitation is deduced. For the experimental analysis a test rig has been developed. It consists of a stainless steel disk (r = 198 mm and h = 8 mm) connected to a variable speed motor. Excitation and response are measured from the rotating system. For the rotating excitation four piezoelectric patches have been used. Calibrating the piezoelectric patches in amplitude and phase, different rotating excitation patterns are applied on the rotating disk in air and in water. Results show the feasibility of using PZT to control the response of the disk due to a rotor-stator interaction.

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“…Modal analysis only deals with independent modes, 85 greatly simplifying the problem to solve. Ahn & Mote (1998) analytically studied the steady-state modal response of an excited rotating disk, and identified the modes linked to forward and backward travelling waves, along with their associated frequencies. Renshaw et al (1994) identified the ratio of the fluid and plate densities to be one of the main influencing parameters: mode split 90 arises when the structure interacts with dense fluids such as water.…”

Section: Introductionmentioning

confidence: 99%

Modal analysis of a spinning disk in a dense fluid as a model for high head hydraulic turbines

Louyot

Nennemann

Monette

et al. 2020

Journal of Fluids and Structures

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In high head Francis turbines and pump-turbines in particular, Rotor Stator Interaction (RSI) is an unavoidable source of excitation that needs to be predicted accurately. Precise knowledge of turbine dynamic characteristics, notably the variation of the rotor natural frequencies with rotation speed and added mass of the surrounding water, is essential to assess potential resonance and resulting amplification of vibrations. In these machines, the disk-like structures of the runner crown and band as well as the head cover and bottom ring give rise to the emergence of diametrical modes and a mode split phenomenon for which no efficient prediction method exists to date. Fully coupled Fluid-Structure Interaction (FSI) methods are too computationally expensive; hence, we seek a simplified modelling tool for the design and the expected-life prediction of these turbines.We present the development of both an analytical modal analysis based on the assumed mode approach and potential flow theory, and a modal force Computational Fluid Dynamics (CFD) approach for rotating disks in dense fluid. Both methods accurately predict the natural frequency split as well as the natural frequency drift within 7.9% of the values measured experimentally. The analytical model explains how mode split and drift are respectively caused by linear and quadratic dependence of the added mass with relative circumferential velocity between flexural waves and fluid rotation.

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Mode identification of a rotating disk

Cited by 20 publications

References 5 publications

Estimation of Nonconservative Aerodynamic Pressure Leading to Flutter of Spinning Disks

Estimation of Nonconservative Aerodynamic Pressure Leading to Flutter of Spinning Disks

Feasibility of Using PZT Actuators to Study the Dynamic Behavior of a Rotating Disk due to Rotor-Stator Interaction

Modal analysis of a spinning disk in a dense fluid as a model for high head hydraulic turbines

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