A comparative study of coupled and decoupled fan flutter prediction methods under variation of mass ratio and blade stiffness

Chahine, Christopher; Verstraete, Tom; He, L.

doi:10.1016/j.jfluidstructs.2018.12.009

Cited by 24 publications

(11 citation statements)

References 19 publications

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“…The first one consists in neglecting the impact of the flow on the structure dynamics for the evaluation of aerodynamic forces due to vibrations, while the second one consists in a strong aeroelastic coupling. The approach to be used depends on the case, as the flow may have some impact on the structure dynamics [11]. Even if the second approach may be more precise, it may be computationally expensive to apply, as the first one already gives good insights on the flutter stability while lowering the computationnal costs.…”

Section: Aeroelastic Modelmentioning

confidence: 99%

“…Usually, a linear approach of the structure is sufficient to assess the fan stage aeroelastic stability. Two approaches may be used to do so, as well explained in [11] : the first one consists in neglecting the effects of aerodynamics on the fan stage dynamics and then to assess stability by studying aeroelastic stability of the structural modes of the fan with harmonic motion ; the second one consists in using strong coupling (partitionned or monolithic approaches) to take into account the effects of the fluid onto the structure dynamics. However, if it is sufficient to consider a linear structure to assess stability limits, it is possible to find stable solutions of the aeroelastic system beyond the stability limits predicted with a linear structure by taking into account nonlinear effects.…”

Section: Introductionmentioning

confidence: 99%

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Investigation of a Methodology for Describing Fan Blade Flutter Limitations Induced by Non-Linear Friction at Blade Roots

Ombret¹,

Pret²,

Dugeai³

et al. 2021

Proceedings of the 8th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COM

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Fan Blade Flutter is an aeroelastic instability which may occur during the operation of a jet engine, depending on the working conditions of the fan stage. It finds its origins in some various mechanisms, including the impact of the environment of the fan stage, which may play an important role in the stability limits due to acoustic effects. If not properly taken into account, flutter can lead to an anticipated ruin of the fan stage as the fluid keeps on giving energy to the structure. However, nonlinear phenomena may appear at some high vibratory amplitude of the blades, resulting in energy dissipation of the aeroelastic system. Blade roots friction is an example of such a case : by dry-friction dissipation at blade roots, a limitation of the vibratory amplitude may be reached, the so-called Limit Cycle Oscillations (LCO), within the unstable regions of the operating domain predicted with a usual linear structural modelling. By taking these nonlinear effects into account, it is then possible to define more precisely the stability limits of the fan stage. In this paper, we describe a methodology to predict LCO induced by blade roots friction, including acoustic effects on stability. First, assuming a linear behaviour of the structure, the stability limits of the fan stage are described using the cyclic symmetry hypothesis and Computational Fluid Dynamics (CFD). Acoustics effects are taken into account by including the fan inlet environment in the numerical model. Then, a nonlinear structural model of the blade is used to compute nonlinear complex modes in order to check for the presence of a LCO. To do so, a reduced model of the fluid response to the blade movement is used. To sum up, this work intends to establish a methodology to be used in an industrial context for the analysis of the nonlinear stability of the fan stage, including LCO phenomena. COMPDYN 2021 8 th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering M. Papadrakakis, M. Fragiadakis (eds.

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Section: Aeroelastic Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Investigation of a Methodology for Describing Fan Blade Flutter Limitations Induced by Non-Linear Friction at Blade Roots

Ombret¹,

Pret²,

Dugeai³

et al. 2021

Proceedings of the 8th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COM

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“…Chahine et al [9] studied the transonic fan rotor at various combinations of mass ratio and stiffness using both decoupled and fully-coupled methods. They found that these two methods are in good agreement over a large range of structural condition.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Structurally and Aerodynamically Mistuned Oscillating Cascade Using Fully Coupled Method

Phan

2021

Journal of Engineering for Gas Turbines and Power

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There seems to be a lack of clear and systematic understanding of physical behaviour and mechanisms of mistuned bladerows, particularly in the context of the aerodynamic mistuning versus the structural (frequency) mistuning. A high-fidelity fully-coupled method is desirable to investigate the vibration characteristics of aeroelasticity problems with strong fluid-structure interaction effects, as well as blade mistuning effects. In the present work, the direct nonlinear time-domain fully-coupled method is adopted to investigate the dynamics mechanism of a mistuned oscillating cascade. The main objectives are two-folds, firstly to elucidate the basic vibration characteristics of a mistuned bladerow, and secondly to examine the aeroelastic effects of mistuning. Three conditions of interest are considered: a) the structural mistuning only, b) the aerodynamic mistuning only, and c) a combination of the two. The present results show that firstly a mistuned configuration tends to vibrate with the same frequency and a predominantly constant inter-blade phase-angle. Vibration amplitudes of the blades vary significantly with a strong mode localization effect for the structural mistuning. For the concurrent structural-aerodynamic mistuning, the localization is stronger than in the standalone structural mistuning case. Secondly, a monotonic increase of the aeroelastic stability with the structural mistuning magnitude is observed. On the other hand, the aerodynamically mistuned cascade shows a stabilizing effect with a small amount of mistuning but exhibits a destabilizing effect with a large mistuning. Furthermore... see paper for the full abstract

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“…However, the cost of performing a single time-accurate aero-elastic computation is still excessive, making adjoint optimization a very demanding task. In the attempt to circumvent this issue, reduced order models for aero-elastic turbomachinery computations have been proposed [3,4,5,6,7], the vast majority of them being based on the so-called energy method [8]. This method enables flutter and forced response analysis with engineering accuracy by means of unsteady fluid-dynamic simulations.…”

Section: Introductionmentioning

confidence: 99%

Adjoint-Based Aeroelastic Design Optimization Using a Harmonic Balance Method

Anand¹,

Rubino²,

Colonna³

et al. 2021

Preprint

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Turbomachinery blades characterized by highly-loaded, slender profiles and operating under unsteady flow may suffer from aeroelastic shortcomings, like forced response and flutter. One of the ways to mitigate these aeroelastic effects is to redesign the blade profiles, so as to increase aero-damping and decrease aero-forcing. Design optimization based on high-fidelity aeroelastic analysis methods is a formidable task due to the inherent computational cost. This work presents an adjoint-based aeroelastic shape-optimization framework based on reduced order methods for flow analysis and forced response computation. The flow analysis is carried out through a multi-frequency fullyturbulent harmonic balance method, while the forced response is computed by means of the energy method. The capability of the design framework is demonstrated by optimizing two candidate cascades, namely, i) a transonic compressor cascade and, ii) a supersonic impulse turbine rotor operating with toluene as working fluid, initially designed by means of the method of waves. The outcomes of the optimization show significant improvements in terms of forced-response in both cases as a consequence of aero-damping enhancement.

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A comparative study of coupled and decoupled fan flutter prediction methods under variation of mass ratio and blade stiffness

Cited by 24 publications

References 19 publications

Investigation of a Methodology for Describing Fan Blade Flutter Limitations Induced by Non-Linear Friction at Blade Roots

Investigation of a Methodology for Describing Fan Blade Flutter Limitations Induced by Non-Linear Friction at Blade Roots

Investigation of Structurally and Aerodynamically Mistuned Oscillating Cascade Using Fully Coupled Method

Adjoint-Based Aeroelastic Design Optimization Using a Harmonic Balance Method

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