Frequency lock-in during vortex induced vibration of a rotating blade

Hoskoti, Lokanna; Misra, Anuradha; Sucheendran, Mahesh M.

doi:10.1016/j.jfluidstructs.2018.03.011

Cited by 31 publications

(3 citation statements)

References 29 publications

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“…In recent years, a large number of scholars have conducted in-depth studies on the flow characteristics of the last stage blades under small volume flow condition [10,11]. Qi et al [1] simulated the steam flow of the last two-stage blades under a low load condition and put forward the law that the height of flow separation varies with the volume flow.…”

Section: Introductionmentioning

confidence: 99%

Analysis on flow separation characteristics of last stage blade in steam turbine under small volume flow condition

et al. 2019

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The inlet steam flow of steam turbine is obviously reduced and even in the state of small volume flow when the thermal power unit is involved in peak load operation, which greatly influences the safety of steam turbine. The last stage flow field of steam turbine under small volume flow condition is calculated by the CFX to study the formation, development, influencing range, and the variation rule of the flow separation vortex cores. The results show that the flow separation vortices appear near last stage blade at 30% of the rated volume flow. With the decrease of volume flow, the flow separation vortices gradually spread to the root of blade. When the volume flow decreases to 8% of the rated volume flow, the flow separation vortices almost occupy the whole blade. The position of the flow separation vortex cores shifts from 72.7% of the relative blade height to 49.1%. The results of this paper lay a foundation for the safety analysis of the last stage blade in the steam turbine under the small volume flow condition.

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Section: Introductionmentioning

confidence: 99%

Analysis on flow separation characteristics of last stage blade in steam turbine under small volume flow condition

et al. 2019

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“…Hoskoti et al [46] studied the instability of the vortex induced vibrations for a blade. Gu et al [47] investigated the free vibration of the rotating cantilever pre-twisted panel with the geometric imperfection of the initial exponential function type.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear and dual-parameter chaotic vibrations of lumped parameter model in blisk under combined aerodynamic force and varying rotating speed

Zhang

et al. 2022

Nonlinear Dyn

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In this paper, the nonlinear and dual-parameter chaotic vibrations are investigated for the blisk structure with the lumped parameter model under combined the aerodynamic force and varying rotating speed. The varying rotating speed and aerodynamic force are respectively simplified to the parametric and external excitations. The nonlinear governing equations of motion for the rotating blisk are established by using Hamilton's principle.The free vibration and mode localization phenomena are studied for the tuning and mistuning blisks. Due to the mistuning, the periodic characteristics of the blisk structure are destroyed and uniform distribution of the energy is broken. It is found that there is a positive correlation between the mistuning variable and mode localization factor to exhibit the large vibration of the blisk in a certain region. The method of multiple scales is applied to derive four-dimensional averaged equations of the blisk under 1:1 internal and principal parametric resonances. The amplitude-frequency response curves of the blisk are studied, which illustrate the influence of different parameters on the bandwidth and vibration amplitudes of the blisk. Lyapunov exponent, bifurcation diagrams, phase portraits, waveforms and Poincare maps are depicted. The dual-parameter Lyapunov exponents and bifurcation diagrams of the blisk reveal the paths leading to the chaos. The influences of different parameters on the bifurcation and chaotic vibrations are analyzed. The numerical results demonstrate that the parametric and external excitations, rotating speed and damping determine the occurrence of the chaotic vibrations and paths leading to the chaotic vibrations in the blisk.

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“…Vortex shedding as a mechanism of premature failure has been reported in a wide range of structures [9]. For instance, structural damage has specifically been observed on stay vanes and runner blades of hydraulic turbines, and is often attributed to severe fatigue loading [10][11][12][13][14]. It is therefore of paramount importance to predict the vibration amplitude of hydrofoils under resonance conditions in order to avoid catastrophic failures and to estimate their life expectancy.…”

Section: Introductionmentioning

confidence: 99%

Understanding the Influence of Wake Cavitation on the Dynamic Response of Hydraulic Profiles under Lock-In Conditions

et al. 2021

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To accelerate the integration of fluctuating renewable energy technologies in the power systems, it is necessary to increase the flexibility of hydropower by operating turbines at off-design conditions. Unfortunately, this strategy causes deleterious flow phenomena such as von Kármán’s vortices at the wake of the vanes and/or blades. When their shedding frequency lies in the vicinity of a structure’s natural frequency, lock-in occurs and vibration amplitudes increase significantly. Moreover, if cavitation occurs at the centers of these vortices, the structure’s dynamic response will be modified. In order to understand this interaction and to avoid its negative consequences, the vibration behavior of a NACA 0009 hydrofoil under a torsional lock-in condition was numerically simulated for cavitation-free and cavitating-flow conditions. The results showed that the presence of vortex cavitation modified the formation and growth process of shed von Kármán vortices in the near-wake region which, in turn, caused an increase of the work performed by the hydrofoil deformation on the surrounding flow and a sharp decrease of the maximum vibration amplitude under resonance conditions.

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Frequency lock-in during vortex induced vibration of a rotating blade

Cited by 31 publications

References 29 publications

Analysis on flow separation characteristics of last stage blade in steam turbine under small volume flow condition

Analysis on flow separation characteristics of last stage blade in steam turbine under small volume flow condition

Nonlinear and dual-parameter chaotic vibrations of lumped parameter model in blisk under combined aerodynamic force and varying rotating speed

Understanding the Influence of Wake Cavitation on the Dynamic Response of Hydraulic Profiles under Lock-In Conditions

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