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.

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.

Investigation of Flow Distortion Generated Forced Response of a Radial Turbine with Vaneless Volute

2020 ◽  
Vol 37 (2) ◽  
pp. 141-151
Author(s):  
Zhi Huang ◽  
Chaochen Ma ◽  
Hong Zhang
Keyword(s):  
Structural Model ◽  
Turbine Rotor ◽  
Forced Response ◽  
Superposition Method ◽  
Flow Distortion ◽  
Fourier Decomposition ◽  
Mode Superposition Method ◽  
Radial Turbine ◽  
Engine Order ◽  
Computational Structural Dynamics

AbstractFor a radial turbine with vaneless volute, the inflow of turbine rotor usually has a circumferential flow distortion due to the influence of the volute tongue. The rotating blades of the rotor are exposed to harmonic aerodynamic loads caused by the distortion, which may induce rotor resonance and lead to high cycle failures (HCF). To understand the forced response mechanism clearly, a numerical analysis was carried out based on a fluid structure interaction (FSI) method. The pressure functions were extracted from the results of a computational fluid dynamics (CFD) analysis by Fourier decomposition. The first three harmonic pressures were identified as the primary engine order (EO) excitations and imposed on the structural model for computational structural dynamics (CSD) simulation. The quantification and assessment of the rotor response were attained by mode superposition method. The simulation results are shown to be consistent with the predictions of Singh’s advanced frequency evaluation (SAFE) diagram.

A Resonance Tracking Algorithm for the Prediction of Turbine Forced Response With Friction Dampers

2000 ◽  
Author(s):  
C. Bréard ◽  
J. S. Green ◽  
M. Vahdati ◽  
M. Imregun
Keyword(s):  
Rotor Blade ◽  
Turbine Blades ◽  
Turbine Rotor ◽  
Forced Response ◽  
Rotor Blades ◽  
Test Case ◽  
Friction Damper ◽  
Blade Vibration ◽  
Frequency Shifts ◽  
Friction Dampers

This paper presents an iterative method for determining the resonant speed shift when non-linear friction dampers are included in turbine blade roots. Such a need arises when conducting response calculations for turbine blades where the unsteady aerodynamic excitation must be computed at the exact resonant speed of interest. The inclusion of friction dampers is known to raise the resonant frequencies by up to 20% from the standard assembly frequencies. The iterative procedure uses a viscous, time-accurate flow representation for determining the aerodynamic forcing, a look-up table for evaluating the aerodynamic boundary conditions at any speed, and a time-domain friction damping module for resonance tracking. The methodology was applied to an HP turbine rotor test case where the resonances of interest were due to the 1T and 2F blade modes under 40 engine-order excitation. The forced response computations were conducted using a multi-stage approach in order to avoid errors associated with “linking” single stage computations since the spacing between the two bladerows was relatively small. Three friction damper elements were used for each rotor blade. To improve the computational efficiency, the number of rotor blades was decreased by 2 to 90 in order to obtain a stator/rotor blade ratio of 4/9. However, the blade geometry was skewed in order to match the capacity (mass flow rate) of the components and the condition being analysed. Frequency shifts of 3.2% and 20.0% were predicted for the 1T/40EO and 2F/40EO resonances in about 3 iterations. The predicted frequency shifts and the dynamic behaviour of the friction dampers were found to be within the expected range. Furthermore, the measured and predicted blade vibration amplitudes showed a good agreement, indicating that the methodology can be applied to industrial problems.

Direct Prediction of the Effects of Mistuning on the Forced Response of Bladed Disks

1998 ◽  
Vol 120 (3) ◽  
pp. 626-634 ◽  
Author(s):  
M. P. Mignolet ◽  
W. Hu
Keyword(s):  
Structural Model ◽  
Order Approximation ◽  
Forced Response ◽  
Blade Vibration ◽  
First Order ◽  
Bladed Disk ◽  
Novel Approach ◽  
Error Terms ◽  
First Order Approximation

In this paper, a novel approach to determine reliable estimates of the moments of the steady-state resonant response of a randomly mistuned bladed disk is presented, and the use of these moments to accurately predict the corresponding distribution of the amplitude of blade vibration is described. The estimation of the moments of the response is accomplished first by relying on a “joint cumulant closure” strategy that expresses higher order moments in terms of lower order ones. A simple modeling of the error terms of these approximations is also suggested that allows the determination of an improved, or accelerated, estimate of the required moments. The evaluation of the distribution of the amplitude of blade response is then accomplished by matching the moments computed by the cumulant closure with those derived from a three-parameter model recently derived. A first order approximation of the moments obtained for a simple structural model of a bladed disk yields a new parameter that can be used as a measure of the localization of the forced response. Then, numerical results demonstrate that the method provides extremely accurate estimates of the moments for all levels of structural coupling which in turn lead to a description of the amplitude of blade response that closely matches simulation results. Finally, a comparison with existing perturbation techniques clearly shows the increased accuracy obtained with the proposed joint cumulant closure formulation.

Forced Response Analysis of a Radial Turbine With Different Modelling Methods

2019 ◽  
Author(s):  
Yang Gao ◽  
Mauricio Gutierrez Salas ◽  
Paul Petrie-Repar ◽  
Tobias Gezork
Keyword(s):  
Periodic Boundary ◽  
Computational Cost ◽  
Computational Effort ◽  
Forced Response ◽  
Response Analysis ◽  
Phase Lag ◽  
Blade Vibration ◽  
Radial Turbine ◽  
High Level ◽  
Key Aspects

Abstract Forced response analysis is a critical part in the radial turbine design process. It estimates the vibration mode and level due to aerodynamic excitations and then enables the analysis of high-cycle fatigue (HCF) to determine the life span of the turbine stage. Two key aspects of the forced response analysis are the determination of the aerodynamic forcing and damping which can be calculated from unsteady 3D computational fluid dynamics (CFD) simulations. These simulations are problematic due to the high level of complexity in the simulations (multi-row, full annular, tip gap, etc.) and the consequent high-computational cost. The aim of this paper is to investigate and compare different CFD methods applied to the forced response analysis of a radial turbine. Full annular simulations are performed for the prediction of the excitation force. This method is taken as the baseline and is usually the most time-consuming one. One method of reducing the computational effort is to use Phase-lag periodic boundary conditions. A further reduction can be obtained by using a frequency-based method called nonlinear harmonic. For the prediction of aero-damping, the Phase -lag periodic boundary condition method is also available. Moreover, a frequency-based method called harmonic balance can further accelerate the aero-damping calculation. In this paper, these CFD methods will be applied to the simulations of an open-geometry radial turbine with a vaned volute. A comparison of unsteady results from different methods will be presented. These unsteady results will also be implemented to a tuned forced response analysis in order to directly compare the corresponding maximum blade vibration amplitudes.

A Method for Forced Response Analysis of Mistuned Bladed Disks With Aerodynamic Effects Included

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
E. P. Petrov
Keyword(s):  
Gas Flow ◽  
Forced Response ◽  
Response Analysis ◽  
Bladed Disks ◽  
Blade Vibration ◽  
Disk Model ◽  
Mechanical Coupling ◽  
Bladed Disk ◽  
Flexible Disk ◽  
Function Matrix

A method has been developed for high-accuracy analysis of forced response levels for mistuned bladed disks vibrating in gas flow. Aerodynamic damping, the interaction of vibrating blades through gas flow, and the effects of structural and aerodynamic mistuning are included in the bladed disk model. The method is applicable to cases of high mechanical coupling of blade vibration through a flexible disk and, possibly shrouds, to cases with stiff disks and low mechanical coupling. The interaction of different families of bladed disk modes is included in the analysis providing the capability of analyzing bladed disks with pronounced frequency veering effects. The method allows the use of industrial-size sector models of bladed disks for analysis of forced response of a mistuned structure. The frequency response function matrix of a structurally mistuned bladed disk is derived with aerodynamic forces included. A new phenomenon of reducing bladed disk forced response by mistuning to levels that are several times lower than those of their tuned counterparts is revealed and explained.

A Method for Forced Response Analysis of Mistuned Bladed Discs With Aerodynamic Effects Included

2009 ◽  
Author(s):  
E. P. Petrov
Keyword(s):  
Gas Flow ◽  
High Accuracy ◽  
Forced Response ◽  
Response Analysis ◽  
Accuracy Analysis ◽  
Blade Vibration ◽  
Mechanical Coupling ◽  
Aerodynamic Damping ◽  
Disc Model ◽  
Function Matrix

A method has been developed for high-accuracy analysis of forced response levels for mistuned bladed discs vibrating in gas flow. Aerodynamic damping, the interaction of vibrating blades through gas flow and the effects of structural and aerodynamic mistuning are included in the bladed disc model. The method is applicable to cases of high mechanical coupling of blade vibration through a flexible disc and, possibly shrouds, and to cases with stiff discs and low mechanical coupling. The interaction of different families of bladed disc modes is included in the analysis providing the capability of analysing bladed discs with pronounced frequency veering effects. The method allows the use of industrial-size sector models of bladed discs for analysis of forced response of a mistuned structure. The frequency response function matrix of a structurally mistuned bladed disc is derived with aerodynamic forces included. A new phenomenon of reducing bladed disc forced response by mistuning to levels that are several times lower than those of their tuned counterparts is revealed and explained.

Consequences of Borescope Blending Repairs on Modern High Pressure Compressor Blisk Aeroelasticity

2019 ◽  
Vol 141 (2) ◽  
Author(s):  
Benjamin Hanschke ◽  
Arnold Kühhorn ◽  
Sven Schrape ◽  
Thomas Giersch
Keyword(s):  
High Pressure ◽  
Aerodynamic Force ◽  
Pressure Ratio ◽  
Forced Response ◽  
Response Analysis ◽  
Influence Coefficient ◽  
Blade Vibration ◽  
Aerodynamic Damping ◽  
High Pressure Compressor ◽  
Pressure Compressor

Objective of this paper is to analyze the consequences of borescope blending repairs on the aeroelastic behavior of a modern high pressure compressor (HPC) blisk. To investigate the blending consequences in terms of aerodynamic damping and forcing changes, a generic blending of a rotor blade is modeled. Steady-state flow parameters like total pressure ratio, polytropic efficiency, and the loss coefficient are compared. Furthermore, aerodynamic damping is computed utilizing the aerodynamic influence coefficient (AIC) approach for both geometries. Results are confirmed by single passage flutter (SPF) simulations for specific interblade phase angles (IBPA) of interest. Finally, a unidirectional forced response analysis for the nominal and the blended rotor is conducted to determine the aerodynamic force exciting the blade motion. The frequency content as well as the forcing amplitudes is obtained from Fourier transformation of the forcing signal. As a result of the present analysis, the change of the blade vibration amplitude is computed.

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.

scholarly journals Direct Prediction of the Effects of Mistuning on the Forced Response of Bladed Disks

1997 ◽  
Author(s):  
Marc P. Mignolet ◽  
Wei Hu
Keyword(s):  
Structural Model ◽  
Order Approximation ◽  
Forced Response ◽  
Blade Vibration ◽  
First Order ◽  
Bladed Disk ◽  
Novel Approach ◽  
Error Terms ◽  
First Order Approximation

In this paper, a novel approach to determine reliable estimates of the moments of the steady state resonant response of a randomly mistuned bladed disk is presented and the use of these moments to accurately predict the corresponding distribution of the amplitude of blade vibration is described. The estimation of the moments of the response is accomplished first by relying on a “joint cumulant closure” strategy that expresses higher order moments in terms of lower order ones. A simple modeling of the error terms of these approximations is also suggested that allows the determination of an improved, or accelerated, estimate of the required moments. The evaluation of the distribution of the amplitude of blade response is then accomplished by matching the moments computed by the cumulant closure with those derived from a three-parameter model recently derived. A first order approximation of the moments obtained for a simple structural model of a bladed disk yields a new parameter that can be used as a measure of the localization of the forced response. Then, numerical results demonstrate that the method provides extremely accurate estimates of the moments for all levels of structural coupling which in turn lead to a description of the amplitude of blade response that closely matches simulation results. Finally, a comparison with existing perturbation techniques clearly shows the increased accuracy obtained with the proposed joint cumulant closure formulation.

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