Experimental Study of Aerodynamic and Structural Damping in a Full-Scale Rotating Turbine

2001 ◽  
Author(s):  
Jason J. Kielb ◽  
Reza S. Abhari
Keyword(s):  
High Cycle Fatigue ◽  
Physical Nature ◽  
Forced Response ◽  
Vibration Modes ◽  
Cycle Fatigue ◽  
Structural Damping ◽  
Large Component ◽  
Blade Vibration ◽  
Aerodynamic Damping ◽  
Turbomachinery Blades

Damping in turbomachinery blades has been an important parameter in the study of forced response and high cycle fatigue, but because of its complexity the sources and physical nature of damping are still not fully understood. This is partly due to the lack of published experimental data and supporting analysis of real rotating components. This paper presents the results of a unique experimental method and data analysis study of multiple damping sources seen in actual turbine components operating at engine conditions. The contributions of both aerodynamic and structural damping for several different blade vibration modes, including bending and torsion, were determined. Results of the experiments indicated that aerodynamic damping was a large component of the total damping for all modes. A study of structural damping as a function of rotational speed was also included to show the effect of friction damping at the blade and disk attachment interface. To the best of the authors’ knowledge, the present paper is the first report of independent and simultaneous structural and aerodynamic damping measurement under engine-level rotational speeds.

Experimental Study of Aerodynamic and Structural Damping in a Full-Scale Rotating Turbine

2002 ◽  
Vol 125 (1) ◽  
pp. 102-112 ◽  
Author(s):  
J. J. Kielb ◽  
R. S. Abhari
Keyword(s):  
High Cycle Fatigue ◽  
Physical Nature ◽  
Forced Response ◽  
Vibration Modes ◽  
Cycle Fatigue ◽  
Structural Damping ◽  
Large Component ◽  
Blade Vibration ◽  
Aerodynamic Damping ◽  
Turbomachinery Blades

Damping in turbomachinery blades has been an important parameter in the study of forced response and high-cycle fatigue, but because of its complexity the sources and physical nature of damping are still not fully understood. This is partly due to the lack of published experimental data and supporting analysis of real rotating components. This paper presents the results of a unique experimental method and data analysis study of multiple damping sources seen in actual turbine components operating at engine conditions. The contributions of both aerodynamic and structural damping for several different blade vibration modes, including bending and torsion, were determined. Results of the experiments indicated that aerodynamic damping was a large component of the total damping for all modes. A study of structural damping as a function of rotational speed was also included to show the effect of friction damping at the blade and disk attachment interface. To the best of the authors’ knowledge, the present paper is the first report of independent and simultaneous structural and aerodynamic damping measurement under engine-level rotational speeds.

Aeroelastic Analysis of NREL Wind Turbine

2017 ◽  
Author(s):  
Yaozhi Lu ◽  
Fanzhou Zhao ◽  
Loic Salles ◽  
Mehdi Vahdati
Keyword(s):  
Numerical Model ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Gas Turbines ◽  
High Cycle Fatigue ◽  
Turbine Blades ◽  
Measured Data ◽  
Forced Response ◽  
Cycle Fatigue ◽  
Aeroelastic Analysis

The current development of wind turbines is moving toward larger and more flexible units, which can make them prone to fatigue damage induced by aeroelastic vibrations. The estimation of the total life of the composite components in a wind turbine requires the knowledge of both low and high cycle fatigue (LCF and HCF) data. The first aim of this study is to produce a validated numerical model, which can be used for aeroelastic analysis of wind turbines and is capable of estimating the LCF and HCF loads on the blade. The second aim of this work is to use the validated numerical model to assess the effects of extreme environmental conditions (such as high wind speeds) and rotor over-speed on low and high cycle fatigue. Numerical modelling of this project is carried out using the Computational Fluid Dynamics (CFD) & aeroelasticity code AU3D, which is written at Imperial College and developed over many years with the support from Rolls-Royce. This code has been validated extensively for unsteady aerodynamic and aeroelastic analysis of high-speed flows in gas turbines, yet, has not been used for low-speed flows around wind turbine blades. Therefore, in the first place the capability of this code for predicting steady and unsteady flows over wind turbines is studied. The test case used for this purpose is the Phase VI wind turbine from the National Renewable Energy Laboratory (NREL), which has extensive steady, unsteady and mechanical measured data. From the aerodynamic viewpoint of this study, AU3D results correlated well with the measured data for both steady and unsteady flow variables, which indicated that the code is capable of calculating the correct flow at low speeds for wind turbines. The aeroelastic results showed that increase in crosswind and shaft speed would result in an increase of unsteady loading on the blade which could decrease the lifespan of a wind turbine due to HCF. Shaft overspeed leads to significant increase in steady loading which affects the LCF behaviour. Moreover, the introduction of crosswind could result in significant dynamic vibration due to forced response at resonance.

Damping Behavior of Blades From Small Radial Turbines

2015 ◽  
Author(s):  
David Hemberger ◽  
Dietmar Filsinger ◽  
Hans-Jörg Bauer
Keyword(s):  
Numerical Analysis ◽  
Dynamic Properties ◽  
Forced Response ◽  
Operating Conditions ◽  
Fe Model ◽  
Structural Damping ◽  
Aerodynamic Damping ◽  
Damping Behavior ◽  
Aerodynamic Properties ◽  
Radial Turbines

Next to excitation forces and the dynamic properties of mistuned structures the damping behavior is a key feature to evaluate the dynamic turbine blade response and thus the HCF life of a bladed disk (blisk). Just as the determination of the mistuning properties and the assessment of the vibration excitation, the evaluation of damping is also subject to uncertainty especially considering the wide operating range of a small radial turbine of a turbocharger. Since the total damping is composed of material damping, structural damping and aerodynamic damping, which are affected by parameters, like the eigenform of the vibration, the magnitude of the vibration amplitude and aerodynamic properties, the total damping can be strongly dependent on the operating conditions. The study at hand provides results from investigations that allow estimating the contribution of aerodynamic damping on the total damping. Experimental and numerical analysis of radial turbines from turbochargers for vehicular engines with variable turbine inlet vanes were performed. Measurements under different environmental conditions such as at rest and during operation, as well as unsteady CFD calculations and, coupled flow and structural calculations were carried out. A change in total damping could be found depending on the density of the surrounding gas by vibration measurements in operation on the hot gas test bench. But it was also shown that the total damping is decisively influenced by the mistuning of the structure. On one side the structural damping is varied by the variation in mistuned blade vibration amplitudes and otherwise the aerodynamic damping is influenced by the different inter blade phase angles (IBPA ) due to the mistuning, which is a symptom of geometric differences and material inhomogeneity in the wheels. Finally, the estimated total damping values were utilized in forced response calculations using a mistuned FE-model of a real turbine and excitation forces from unsteady CFD calculation. The magnitudes of the measured vibration amplitudes were compared with results from numerical analysis to validate the numerical model with focus on the investigation about the total damping. The deviation between the results was ±10% for different eigenforms and excitation orders.

Prediction of Aerodynamically Induced Blade Vibrations in a Radial Turbine Rotor Using the Nonlinear Harmonic Approach

2018 ◽  
Author(s):  
Nikola Kovachev ◽  
Christian U. Waldherr ◽  
Jürgen F. Mayer ◽  
Damian M. Vogt
Keyword(s):  
Structural Model ◽  
Measurement Data ◽  
Turbine Rotor ◽  
Forced Response ◽  
Response Analysis ◽  
Blade Vibration ◽  
Computational Costs ◽  
Alternative Approach ◽  
Turbomachinery Blades ◽  
Predicted Values

Resonant response of turbomachinery blades can lead to high cycle fatigue (HCF) if the vibration amplitudes are excessive. Accurate and reliable simulations of the forced response phenomenon require detailed CFD and FE models that may consume immense computational costs. In the present study, an alternative approach is applied, which incorporates nonlinear harmonic (NLH) CFD simulations in a one-way fluid-structure interaction (FSI) workflow for the prediction of the forced response phenomenon at reduced computational costs. Five resonance crossings excited by the stator in a radial inflow turbocharger turbine are investigated and the aerodynamic excitation and damping are predicted using this approach. Blade vibration amplitudes are obtained from a subsequent forced response analysis combining the aerodynamic excitation with aerodynamic damping and a detailed structural model of the investigated turbine rotor. A comparison with tip timing measurement data shows that all predicted values lay within the range of the mistuned blade response underlining the high quality of the utilized workflow.

Smart Structures: Gas Turbine Engine Applications

2001 ◽  
Author(s):  
Sanford Fleeter ◽  
Patrick B. Lawless
Keyword(s):  
Gas Turbine ◽  
Smart Materials ◽  
High Cycle Fatigue ◽  
Smart Structures ◽  
Forced Response ◽  
Smart Structure ◽  
Turbine Engines ◽  
Cost Ratio ◽  
Gas Turbine Engines ◽  
Cycle Fatigue

Abstract This paper is directed at providing the smart structure technology community an introduction to aircraft gas turbine engines issues that might be addressed, i.e. smart/active propulsion systems. Specifically, in gas turbine engines, smart structures can (1) influence performance, stability, noise and high cycle fatigue by providing airfoil aerodynamic control, (2) alleviate or avoid high cycle fatigue due to flutter and forced response by introducing damping intra structures, and (3) provide health monitoring. However, the benefits-to-cost ratio of the added complexity of incorporating smart materials into gas turbine engines must be large as smart materials and actuator/control systems are not a simple solution to complex problems. The prime selling point of smart structure technology to current state-of-the-art gas turbine engines may be adaptability to age, mission, and the environment.

Aeromechanic Response of a Coupled Inlet-Fan Boundary Layer Ingesting Distortion-Tolerant Fan

2019 ◽  
Author(s):  
G. S. Heinlein ◽  
M. A. Bakhle ◽  
J. P. Chen
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Fluid Dynamic ◽  
Single Mode ◽  
Forced Response ◽  
Blade Vibration ◽  
Wind Tunnel Tests ◽  
Aerodynamic Damping ◽  
Insight Into ◽  
Tip Displacement

Abstract Boundary layer ingestion has significant potential to reduce fuel burn in aircraft engines. However, designing a fan that can operate in an environment of continuous distortion without aeromechanical failure is a critical challenge. Capturing the requisite aeromechanical flow features in a high-fidelity computational setting is necessary in validating satisfactory designs as well as determining possible regions for overall improvement. In the current work, a three-dimensional, time-accurate, Reynolds-averaged Navier-Stokes computational fluid dynamic code is utilized to study a distortion-tolerant fan coupled to a boundary layer ingesting inlet. The comparison between this coupled inlet-fan and a previous fan-only simulation will provide insight into the changes in aeromechanic response of the fan blades. Additionally, comparisons to previous wind tunnel tests are made to provide validation of inlet distortion as seen by the distortion-tolerant fan. A resonant crossing was also investigated for the 85% speed operational line condition to compare resonant response between the inlet-fan, fan-only, and experiment. A decrease in maximum tip displacement is observed in the forced response of the coupled inlet-fan compared to the fan-only simulation. The predicted maximum tip displacement was still below the upper limit on the range observed in the wind tunnel tests but matched well with the average tip displacement value of 27.6 mils. A single mode was chosen at the 100% speed condition to provide insight into the effects that the inlet duct has on fan stability. Near stall and near choke conditions were also simulated to observe how the changes of progressing along the speed line affects flutter stability prediction. The analysis shows the fan has low levels of aerodynamic damping at all the conditions tested. However, the coupled inlet-fan shows a decrease in the level of aerodynamic damping over what was observed with the fan-only simulation. Some of the blades experienced single cycles of negative aerodamping which indicate a possibility of increased blade vibration amplitude but were followed by positive aerodamping cycles. Work is continuing to understand possible sources to account for the differences observed between the two simulation cases as well as with the experiment.

Experimental and Numerical Investigation of Vibration Damping Using a Thin Layer Coating

2017 ◽  
Author(s):  
Imran Aziz ◽  
Sajjad Hussain ◽  
Wasim Tarar ◽  
Imran Akhtar
Keyword(s):  
Nickel Alloy ◽  
High Cycle Fatigue ◽  
Natural Frequencies ◽  
Damping Ratio ◽  
Rotating Machinery ◽  
Forced Response ◽  
Cycle Fatigue ◽  
Damping Characteristics ◽  
At Resonance ◽  
Vibration Shaker

High cycle fatigue (HCF) is the main cause of failure in rotating machinery especially in aircraft engines which results in the loss of human life as well as billions of dollars. More than 60 percent of aircraft accidents are related to High cycle fatigue. Major reason for HCF is vibratory stresses induced in the blades at resonance. Damping is needed to avoid vibratory stresses to reach the failure level. High speed rotating machinery has to pass through the resonance in order to reach the operational speed and chances of failure are high at resonance level. It is therefore required to suppress the vibrations at resonance level to avoid any damage to the structure. Application of coating to suppress vibrations is a current area of research. Various types of coatings have been studied recently. This includes plasma graded coatings, viscoelastic dampers, piezoelectric material damping, and magnetomechanical damping. In this research, the phenomenon of damping using a coating of nickel alloy on a steel beam is studied experimentally and numerically to reduce vibratory stresses by enhancing damping characteristics to avoid aircraft engine and rotating machinery failure. For this purpose, uncoated and nickel alloy coated steel beams are fabricated. The coating procedure was performed using plasma arc method. The beams were then mounted in a cantilevered position and bump and vibration shaker tests were conducted to determine the natural frequencies and mode shapes. One of the most important parameter to measure the damping of a system is the damping ratio. In order to determine the damping ratio, vibration analyzer mode was adjusted in time domain and beam was excited by using a hammer. The vibration analyzer showed the vibration decay as a function of time. Using that decay, damping ratio was calculated by using logarithmic decrement method. In order to investigate and compare the damping characteristics of un-coated and coated beams, forced response method was employed. In this method, beams were excited at 1st and 2nd bending mode natural frequencies using vibration shaker. Results were very encouraging and showed a significant improvement in damping characteristics. The experimental results were then endorsed by numerical results which were achieved by performing modal and forced response analysis using finite element analysis techniques.

Forced Response Analyses of Mistuned Radial Inflow Turbines

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Thomas Giersch ◽  
Peter Hönisch ◽  
Bernd Beirow ◽  
Arnold Kühhorn
Keyword(s):  
Numerical Method ◽  
Fluid Structure Interaction ◽  
Industrial Applications ◽  
Forced Response ◽  
Blade Vibration ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Aerodynamic Damping ◽  
Radial Turbine ◽  
Spiral Casing

Radial turbine wheels designed as blade integrated disks (blisk) are widely used in various industrial applications. However, related to the introduction of exhaust gas turbochargers in the field of small and medium sized engines, a sustainable demand for radial turbine wheels has come along. Despite those blisks being state of the art, a number of fundamental problems, mainly referring to fluid-structure-interaction and, therefore, to the vibration behavior, have been reported. Aiming to achieve an enhanced understanding of fluid-structure-interaction in radial turbine wheels, a numerical method, able to predict forced responses of mistuned blisks due to aerodynamic excitation, is presented. In a first step, the unsteady aerodynamic forcing is determined by modeling the spiral casing, the stator vanes, and the rotor blades of the entire turbine stage. In a second step, the aerodynamic damping induced by blade vibration is computed using a harmonic balance technique. The structure itself is represented by a reduced order model being extended by aerodynamic damping effects and aerodynamic forcings. Mistuning is introduced by adjusting the modal stiffness matrix based on results of blade by blade measurements that have been performed at rest. In order to verify the numerical method, the results are compared with strain-gauge data obtained during rig-tests. As a result, a measured low engine order excitation was found by modeling the spiral casing. Furthermore, a localization phenomenon due to frequency mistuning could be proven. The predicted amplitudes are close to the measured data.

Forced Response Analyses of Mistuned Radial Inflow Turbines

2012 ◽  
Author(s):  
Thomas Giersch ◽  
Peter Hönisch ◽  
Bernd Beirow ◽  
Arnold Kühhorn
Keyword(s):  
Numerical Method ◽  
Fluid Structure Interaction ◽  
Industrial Applications ◽  
Forced Response ◽  
Blade Vibration ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Aerodynamic Damping ◽  
Radial Turbine ◽  
Spiral Casing

Radial turbine wheels designed as blade integrated disks (blisk) are widely used in various industrial applications. However, related to the introduction of exhaust gas turbochargers in the field of small and medium sized engines a sustainable demand for radial turbine wheels has come along. Despite those blisks are state of the art, a number of fundamental problems, mainly referred to fluid-structure-interaction and therefore to the vibration behavior, have been reported. Aiming to achieve an enhanced understanding of fluid-structure-interaction in radial turbine wheels a numerical method, able to predict forced responses of mistuned blisks due to aerodynamic excitation, is presented. In a first step the unsteady aerodynamic forcing is determined by modeling the spiral casing, the stator vanes and the rotor blades of the entire turbine stage. In a second step the aerodynamic damping induced by blade vibration is computed using a harmonic balance technique. The structure itself is represented by a reduced order model being extended by aerodynamic damping effects and aerodynamic forcings. Mistuning is introduced by adjusting the modal stiffness matrix based on results of blade by blade measurements that have been performed at rest. In order to verify the numerical method, the results are compared with strain-gauge data obtained during rig-tests. As a result a measured low engine order excitation was found by modeling the spiral casing. Furthermore a localization phenomenon due to frequency mistuning could be proven. The predicted amplitudes are close to measured data.

Prediction of Aerodynamically Induced Blade Vibrations in a Radial Turbine Rotor Using the Nonlinear Harmonic Approach

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Nikola Kovachev ◽  
Christian U. Waldherr ◽  
Jürgen F. Mayer ◽  
Damian M. Vogt
Keyword(s):  
Structural Model ◽  
Measurement Data ◽  
Turbine Rotor ◽  
Forced Response ◽  
Response Analysis ◽  
Blade Vibration ◽  
Computational Costs ◽  
Alternative Approach ◽  
Turbomachinery Blades ◽  
Predicted Values

Resonant response of turbomachinery blades can lead to high cycle fatigue (HCF) if the vibration amplitudes are excessive. Accurate and reliable simulations of the forced response phenomenon require detailed CFD and FE models that may consume immense computational costs. In the present study, an alternative approach is applied, which incorporates nonlinear harmonic (NLH) CFD simulations in a one-way fluid–structure interaction (FSI) workflow for the prediction of the forced response phenomenon at reduced computational costs. Five resonance crossings excited by the stator in a radial inflow turbocharger turbine are investigated and the aerodynamic excitation and damping are predicted using this approach. Blade vibration amplitudes are obtained from a subsequent forced response analysis combining the aerodynamic excitation with aerodynamic damping and a detailed structural model of the investigated turbine rotor. A comparison with tip timing measurement data shows that all predicted values lay within the range of the mistuned blade response underlining the high quality of the utilized workflow.

Sign in / Sign up

Export Citation Format

Share Document