Parametric study of the aeroelastic response of mistuned bladed disks

The dynamic design of bladed disks consists in making sure that structural modes are not excited by the harmonics caused by engine speed (coincidences predicted after a Campbell diagram analysis). In practice, it is impossible to avoid every single coincidence over the whole operating range. An engine test is carried out at the end of the design cycle, in order to determine vibration levels. By means of this test and the validated FE model, the designer verifies frequency margins, and from this, is able to determine whether or not the bladed disk is likely to be at risk from vibration fatigue, otherwise known as High Cycle Fatigue (HCF). This analysis needs several FE calculations whose models have been updated in relation to component tests to measure stress distribution (use of strain gauges). One of the drawbacks of this type of measurement lies in the intrusive character of instrumentation used, which upsets the dynamic behavior of the blades in particular for high level modes. This document puts forward the application of non-intrusive, optical measurements, and highlights the accuracy that can be obtained by measuring mode shapes. Furthermore, this paper highlights the importance of defining levels of accuracy for measurements obtained, for example, in characterizing frequency scatterings for each blade individually, scatterings which are translated by an amplification of the structure aeroelastic response.

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Maximum Amplification of Blade Response Due to Mistuning: Localization and Mode Shapes Aspects of the Worst Disks

Volume 4: Turbo Expo 2002, Parts A and B ◽

10.1115/gt2002-30323 ◽

2002 ◽

Cited By ~ 4

Author(s):

Alejandro J. Rivas-Guerra ◽

Marc P. Mignolet

Keyword(s):

Parametric Study ◽

Resonant Mode ◽

Forced Response ◽

Mode Shapes ◽

Optimization Strategy ◽

Bladed Disks ◽

Worst Case ◽

Disk Model ◽

Engine Order ◽

Maximum Amplification

This paper focuses on the determination and study of the maximum amplification of the steady state forced response of bladed disks due to mistuning. First, an optimization strategy is proposed in which partially mistuned bladed disks are considered as physical approximations of the worst case disk and the mistuned properties are sought to maximize the response of a specific blade. This approach is exemplified on both a reduced order model of a blisk and a single-degree-of-freedom per blade disk model an extensive parametric study of which is conducted with respect to blade-to-blade coupling, damping, and engine order. A mode shape-based formulation of the amplification factor is then developed to clarify the findings of the parametric study in the strong coupling/small damping limit. In this process, the upper bound of Whitehead is recovered for all engine orders and number of blades and the conditions under which this limit is exactly achieved or closely approached are clarified. This process also uncovers a simple yet reliable approximation of the resonant mode shapes and natural frequencies of the worst disk.

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A Parametric Study on the Aeroelasticity of Flared Hinge Folding Wingtips

Aerospace ◽

10.3390/aerospace8080221 ◽

2021 ◽

Vol 8 (8) ◽

pp. 221

Author(s):

Rafic M. Ajaj ◽

Erick I. Saavedra Flores ◽

Mohammadreza Amoozgar ◽

Jonathan E. Cooper

Keyword(s):

Parametric Study ◽

Nonlinear Behavior ◽

Aerodynamic Load ◽

Aeroelastic Response ◽

Beam Elements ◽

Aeroelastic Analysis ◽

Aeroelastic Model ◽

Strip Theory ◽

Line Angle ◽

Tip Mass

This paper presents a parametric study on the aeroelasticity of cantilever wings equipped with Flared Hinge Folding Wingtips (FHFWTs). The finite element method is utilized to develop a computational, low-fidelity aeroelastic model. The wing structure is modelled using Euler–Bernoulli beam elements, and unsteady Theodorsen’s aerodynamic strip Theory is used for aerodynamic load predictions. The PK method is used to estimate the aeroelastic boundaries. The model is validated using three rectangular, cantilever wings whose properties are available in literature. Then, a rectangular, cantilever wing is used to study the effect of folding wingtips on the aeroelastic response and stability boundaries. Two scenarios are considered for the aeroelastic analysis. In the first scenario, the baseline, rectangular wing is split into inboard and outboard segments connected by a flared hinge that allows the outboard segment to fold. In the second scenario, a folding wingtip is added to the baseline wing. For both scenarios, the influence of fold angle, hinge-line angle (flare angle), hinge stiffness, tip mass and geometry are assessed. In addition, the load alleviation capability of FHFWT is evaluated when the wing encounters discrete (1-cosine) gusts. Finally, the hinge is assumed to exhibit cubic nonlinear behavior in torsion, and the effect of nonlinearity on the aeroelastic response is assessed and analyzed for three different cases.

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Maximum Amplification of Blade Response due to Mistuning: Localization and Mode Shape Aspects of the Worst Disks

Journal of Turbomachinery ◽

10.1115/1.1506958 ◽

2003 ◽

Vol 125 (3) ◽

pp. 442-454 ◽

Cited By ~ 32

Author(s):

Alejandro J. Rivas-Guerra ◽

Marc P. Mignolet

Keyword(s):

Mode Shape ◽

Parametric Study ◽

Resonant Mode ◽

Forced Response ◽

Mode Shapes ◽

Optimization Strategy ◽

Bladed Disks ◽

Worst Case ◽

Disk Model ◽

Maximum Amplification

This paper focuses on the determination and study of the maximum amplification of the steady state forced response of bladed disks due to mistuning. First, an optimization strategy is proposed in which partially mistuned bladed disks are considered as physical approximations of the worst case disk and the mistuned properties are sought to maximize the response of a specific blade. This approach is exemplified on both a reduced order model of a blisk and a single-degree-of-freedom per blade disk model an extensive parametric study of which is conducted with respect to blade-to-blade coupling, damping, and engine order. A mode shape-based formulation of the amplification factor is then developed to clarify the findings of the parametric study in the strong coupling/small damping limit. In this process, the upper bound of Whitehead is recovered for all engine orders and number of blades and the conditions under which this limit is exactly achieved or closely approached are clarified. This process also uncovers a simple yet reliable approximation of the resonant mode shapes and natural frequencies of the worst disk.

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Parametric Study of Photovoltaic Thermal Solar Collector Using An Improved Parallel Flow

Journal of Engineering Technology and Applied Physics ◽

10.33093/jetap.2020.2.1.4 ◽

2020 ◽

Vol 2 (1) ◽

pp. 19-24

Author(s):

Sakhr Mohammed Sultan ◽

Chih Ping Tso ◽

Ervina Efzan Mohd Noor ◽

Fadhel Mustafa Ibrahim ◽

Saqaff Ahmed Alkaff

Keyword(s):

Thermal Conductivity ◽

Energy Balance ◽

Parametric Study ◽

Solar Collector ◽

Parallel Flow ◽

Operating Conditions ◽

Balance Equations ◽

Conductivity Type ◽

Pv Module ◽

Sunny Weather

Photovoltaic Thermal Solar Collector (PVT) is a hybrid technology used to produce electricity and heat simultaneously. Current enhancements in PVT are to increase the electrical and thermal efficiencies. Many PVT factors such as type of absorber, thermal conductivity, type of PV module and operating conditions are important parameters that can control the PVT performance. In this paper, an analytical model, using energy balance equations, is studied for PVT with an improved parallel flow absorber. The performance is calculated for a typical sunny weather in Malaysia. It was found that the maximum electrical and thermal efficiencies are 12.9 % and 62.6 %, respectively. The maximum outlet water temperature is 59 oC.

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