The effect of aerodynamic asymmetries on turbomachinery flutter

Ekici, Kivanc; Kielb, Robert E.; Hall, Kenneth C.

doi:10.1016/j.jfluidstructs.2012.08.009

Cited by 28 publications

(13 citation statements)

References 25 publications

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“…This leads, again formally, to a block diagonalization of the aerodynamic matrix M aer0 in the TW basis: The mistuning of the aerodynamic forces is neglected in this analysis because it is typically of higher order; it is a small correction of the already small aerodynamic effects. Stronger airfoil modifications would be required to make aerodynamic mistuning relevant (as in the case of leading edge blending [23]), but this is not the situation considered here. And finally, the mistuning correction matrix A that contains all the mistuning terms is defined as: A = P H (AK j 2 AM) (A.15)…”

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confidence: 99%

Maximum mistuning amplification of the forced response vibration of turbomachinery rotors in the presence of aerodynamic damping

Martel

Sánchez-Álvarez

2017

Journal of Sound and Vibration

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Mistuning can dangerously increase the vibration amplitude of the forced response of a turbomachinery rotor. In the case of damping coming from aerodynamic effects the situation is more complicated because the magnitude of the damping changes for the different travelling wave modes of the system. This damping variability modifies the effect of mistuning, and it can even result in a reduction of the mistuned forced response amplitude below that of the tuned case (this is not possible in the usual case of constant material damping). In this paper the Asymptotic Mistuning Model (AMM) methodology is used to analyze this situation. The AMM is a reduced order model that is systematically derived from the mistuned bladed disk full model using a perturbative procedure based on the small size of the mistuning and the damping. The AMM allows to derive a very simple expression for an upper bound of the maximum amplification factor of the vibration amplitude that the system can experience (an extension of the well known Whitehead 1966 result to include the effect of non-uniform aerodamping). This new upper bound gives information on the mechanisms involved in the amplification/reduction of the mistuned response: (i) the number of modes participating in the response, and (ii) the ratio between the aerodamping of the directly forced mode and that of the of the rest of the modes. A FEM of a mistuned bladed disk is also used to verify the AMM predictions for several different forcing configurations, and both results show a very good quantitative agreement.

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confidence: 99%

Maximum mistuning amplification of the forced response vibration of turbomachinery rotors in the presence of aerodynamic damping

Martel

Sánchez-Álvarez

2017

Journal of Sound and Vibration

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“…16 The combined effect of collision and friction between contact surfaces of integral shrouds dissipates the vibration energy of the blades. 17 For a whole integral shroud blades system, the contact constraints between the adjacent integral shroud will affect the overall stiffness of the blades, resulting in changing the resonance frequency of the blade system. When the natural frequency of the entire blade system is not in the resonance zone, its vibration response can be effectively controlled.…”

Section: Introductionmentioning

confidence: 99%

Study on the collision dynamics of integral shroud blade for high-pressure turbine in different integral shroud clearance distance

Zhang

Wang

Qin

et al. 2021

Noise & Vibration Worldwide

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In steam turbine, turbine blades are prone to vibrate during operation, resulting in steam turbine accidents. The most common method for reducing the vibration of steam turbine blades is to design an integral shroud for blade which is termed as integral shroud blade. Most previous studies simplified straight integral blades into cantilever beam and used harmonic response analysis method to simulate the vibration response of blades. This method is suitable for simulating straight blade vibration under harmonic force conditions. For twisted blades, accurate results are hard to acquire and the specific collision process cannot be simulated. In order to observe the collision process on a microscopic scale and explore its collision damping mechanism, this study evaluated the collision process of twisted blades with different integral shroud clearance distance based on LS-DYNA software. The collision process for a two-blade system and a three-blade system with integral shroud clearance distance from 0.1 mm to 0.5 mm has been simulated. The results indicated that integral shroud clearance distance have opposite vibration damping effect when the blade under the condition of forced vibration and free vibration. For the two-blade system, the optimal integral shroud clearance distance is 0.4 mm for forced vibration condition and 0.1 mm for free vibration condition. For the three-blade system, the optimal integral shroud clearance distance is 0.1 mm for forced vibration condition and 0.5 mm for free vibration condition.

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“…At the corrected mass flow lower or higher than that at the design point, the efficiency variation was much less significant. More closely related to aeroelasticity, various researchers have found that the aerodynamic detuning typically enhanced flutter stability [18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Efficient Steady and Unsteady Flow Modeling for Arbitrarily Mis-Staggered Bladerow Under Influence of Inlet Distortion

Phan

2020

Volume 10A: Structures and Dynamics

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Accurate and efficient predictions of the steady and unsteady flow responses due to the blade-to-blade variation as well as due to the non-axisymmetric inlet distortion have been continually pursued. Computation of two problems concurrently has been rarely done in the past partly because of the need to perform whole annulus bladerow simulations, despite the advances in the current state-of-the-art methods with the phaseshift single passage simulations. The current work attempts to deal with this challenge by developing a new computational approach based on the principle of the multiscale method in the framework of a commercial solver (CFX). The methodology formulation relies on summation of the constituent source terms, each of which corresponds to a particular flow perturbation. The source term element corresponding to the blade-to-blade variation effect is linearly superimposed as in the classical Influence Coefficient Method. Only the relative positions between the reference blade and its neighbor matter in this method, thus enables an arbitrarily mis-staggered bladerow to be computed efficiently. In addition, the source term arisen due to the inlet distortion is calculated based on spatial Fourier transform. A key enabler is that the source term can be pre-computed using a small set of identical blade passages. The source term is then propagated to different spatial and temporal locations depending on the combination of the mis-staggering pattern and the inlet distortion. The multiscale treatment makes it possible to predict a high-resolution flow field effects on the base coarse mesh as if the fine mesh is solved, while achieving a computational gain. The source term summation method proposed in the current work has been validated using a uniformly staggered bladerow, and an arbitrarily mis-staggered bladerow in a clean inflow condition as well as that subject to an inlet distortion.

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The effect of aerodynamic asymmetries on turbomachinery flutter

Cited by 28 publications

References 25 publications

Maximum mistuning amplification of the forced response vibration of turbomachinery rotors in the presence of aerodynamic damping

Maximum mistuning amplification of the forced response vibration of turbomachinery rotors in the presence of aerodynamic damping

Study on the collision dynamics of integral shroud blade for high-pressure turbine in different integral shroud clearance distance

Efficient Steady and Unsteady Flow Modeling for Arbitrarily Mis-Staggered Bladerow Under Influence of Inlet Distortion

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