A Study of Nonlinear Vibrations in a Frictionally-Damped Turbine Bladed Disc With Comprehensive Modelling of Aerodynamic Effects

2012 ◽  
Author(s):  
E. P. Petrov ◽  
Z.-I. Zachariadis ◽  
A. Beretta ◽  
R. Elliott
Keyword(s):  
Gas Flow ◽  
Aerodynamic Characteristics ◽  
Forced Response ◽  
New Method ◽  
Mode Shapes ◽  
Response Analysis ◽  
Resonance Frequencies ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Effects

A new effective method for comprehensive modelling of gas flow effects on vibration of nonlinear vibration of bladed discs has been developed for a case when effect of the gas flow on the mode shapes is significant. The method separates completely the structural dynamics calculations from the significantly more computationally expensive computational fluid dynamics (CFD) calculations while provides the high accuracy of modelling for aerodynamic effects. A comprehensive analysis of the forced response using the new method has been performed for a realistic turbine bladed disc with root-disc joints, tip and underplatform dampers. The full chain of aerodynamic and structural calculations are performed: (i) determination of boundary conditions for CFD; (ii) CFD analysis; (iii) calculation of the aerodynamic characteristics required by the new method; (iv) nonlinear forced response analysis using the MAIM. The efficiency of the friction damping devices has been studied and compared for several resonance frequencies and engine orders. Advantages of the method for aerodynamic effect modelling have been demonstrated.

A Study of Nonlinear Vibrations in a Frictionally Damped Turbine Bladed Disk With Comprehensive Modeling of Aerodynamic Effects

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
E. P. Petrov ◽  
Z.-I. Zachariadis ◽  
A. Beretta ◽  
R. Elliott
Keyword(s):  
Gas Flow ◽  
Aerodynamic Characteristics ◽  
Forced Response ◽  
New Method ◽  
Mode Shapes ◽  
Response Analysis ◽  
Influence Matrix ◽  
Bladed Disk ◽  
Resonance Frequencies ◽  
Comprehensive Modeling

A new effective method for comprehensive modeling of gas flow effects on vibration of nonlinear vibration of bladed disks has been developed for a case when the effect of the gas flow on the mode shapes is significant. The method separates completely the structural dynamics calculations from the significantly more computationally expensive computational fluid dynamics (CFD) calculations while providing the high accuracy of modeling for aerodynamic effects. A comprehensive analysis of the forced response using the new method has been performed for a realistic turbine bladed disk with root-disk joints, tip, and under-platform dampers. The full chain of aerodynamic and structural calculations are performed: (i) determination of boundary conditions for CFD, (ii) CFD analysis, (iii) calculation of the aerodynamic characteristics required by the new method, and (iv) nonlinear forced response analysis using the modal aerodynamic influence matrix (MAIM). The efficiency of the friction damping devices has been studied and compared for several resonance frequencies and engine orders. Advantages of the method for aerodynamic effect modeling have been demonstrated.

Forced Response of Mistuned Bladed Discs in Gas Flow: A Comparative Study of Predictions and Full-Scale Experimental Results

2009 ◽  
Author(s):  
Evgeny Petrov ◽  
Luca Di Mare ◽  
Holger Hennings ◽  
Robert Elliott
Keyword(s):  
Data Exchange ◽  
Gas Flow ◽  
Numerical Study ◽  
Forced Response ◽  
Full Scale ◽  
Response Analysis ◽  
Test Rig ◽  
Good Correspondence ◽  
Resonance Frequencies ◽  
Underplatform Damper

An integrated experimental-numerical study of forced response for a mistuned bladed disc has been performed. A full chain for the predictive forced response analysis has been developed including data exchange between the CFD code and a code for the prediction of the nonlinear forced response for a bladed disc. The experimental measurements are performed at a full-scale single stage test rig with excitation by aerodynamic forces from gas flow. Numerical modelling approaches and the test rig setup are discussed. Comparison of experimentally measured and predicted values of blade resonance frequencies and response levels for a mistuned bladed disc without dampers is performed. A good correspondence between frequencies at which individual blades have maximum response levels is achieved. The effects of structural damping and underplatform damper parameters on amplitudes and resonance frequencies of the bladed disc are explored. It is shown that the underplatform damper significantly reduces scatters in values of the individual blade frequencies and maximum forced response levels.

Forced Response of Mistuned Bladed Disks in Gas Flow: A Comparative Study of Predictions and Full-Scale Experimental Results

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Evgeny Petrov ◽  
Luca Di Mare ◽  
Holger Hennings ◽  
Robert Elliott
Keyword(s):  
Data Exchange ◽  
Gas Flow ◽  
Numerical Study ◽  
Forced Response ◽  
Full Scale ◽  
Response Analysis ◽  
Test Rig ◽  
Bladed Disk ◽  
Resonance Frequencies ◽  
Underplatform Damper

An integrated experimental-numerical study of forced response for a mistuned bladed disk has been performed. A full chain for the predictive forced response analysis has been developed including data exchange between the computational fluid dynamics code and a code for the prediction of the nonlinear forced response for a bladed disk. The experimental measurements are performed at a full-scale single stage test rig with excitation by aerodynamic forces from gas flow. The numerical modeling approaches and the test rig setup are discussed. Comparison of experimentally measured and predicted values of blade resonance frequencies and response levels for a mistuned bladed disk without dampers is performed. A good correspondence between frequencies at which individual blades have maximum response levels is achieved. The effects of structural damping and underplatform damper parameters on amplitudes and resonance frequencies of the bladed disk are explored. It is shown that the underplatform damper significantly reduces scatters in values of the individual blade frequencies and maximum forced response levels.

scholarly journals Forced Response Analysis of High-Mode Vibrations for Mistuned Bladed Discs With Effective Reduced-Order Models

2015 ◽  
Author(s):  
Yongliang Duan ◽  
Chaoping Zang ◽  
E. P. Petrov
Keyword(s):  
High Frequency ◽  
Dynamic Properties ◽  
Forced Response ◽  
High Mode ◽  
Mode Shapes ◽  
Response Analysis ◽  
Computationally Efficient ◽  
Accurate Analysis ◽  
Reduced Order ◽  
Model Reduction Technique

This paper is focused on the analysis of effects of mistuning on the forced response of gas-turbine bladed discs vibrating in the frequency ranges corresponding to higher modes. For high modes the blade aerofoils are deformed during vibrations and the blade mode shapes differ significantly from beam mode shapes. A model reduction technique is developed for the computationally efficient and accurate analysis of forced response for bladed discs vibrating in high frequency ranges. High-fidelity finite element models of a tuned bladed disc sector are used to provide primary information about dynamic properties of a bladed disc and the blade mistuning is modelled by specially defined mistuning matrices. The forced response displacement and stress amplitude levels are studied for high frequency ranges. The effects of different types of mistuning are examined and the existence of high amplifications of mistuned forced response levels is shown for high-mode vibrations: in some cases, the resonance peak response of a tuned structure can be lower than out-of-resonance amplitudes of its mistuned counterpart.

A Case Study of the Unsteady Response of a Hingeless Helicopter Rotor Blade

2019 ◽  
Author(s):  
Pratik Sarker ◽  
Uttam K. Chakravarty
Keyword(s):  
Mathematical Model ◽  
Steady State ◽  
Rotor Blade ◽  
Degrees Of Freedom ◽  
Forced Response ◽  
Helicopter Rotor ◽  
Mode Shapes ◽  
Response Analysis ◽  
Steady State Condition ◽  
Helicopter Rotor Blade

Abstract The helicopter is an essential means of transport for numerous tasks including carrying passengers and equipment, providing air medical services, firefighting, and other military and civil tasks. While in operation, the nature of the unsteady aerodynamic environment surrounding the rotor blades gives rise to a significant amount of vibration to the helicopter. In this study, the unsteady forced response of the Bo 105 hingeless helicopter rotor blade is investigated at the forward flight in terms of the coupled flapping, lead-lag, and torsional deformations. The mathematical model for the steady-state response of the rotor blade is modified to include the unsteady airfoil behavior by using the Theodorsen’s lift deficiency function for three degrees of freedom of motion. The nonlinear mathematical model is solved by the generalized method of lines in terms of the time-varying deflections of the rotor blade. The unsteady airloads are found to create larger deformations compared to that of the steady-state condition for a given advance ratio. The azimuth locations of the peak loadings also vary with different degrees of freedom. The first three natural frequencies and mode shapes of the rotor blade are presented. The model for the forced response analysis is validated by finite element results.

The Re-Evaluation of the AVR Melt-Wire Experiment Using Modern Methods With Specific Focus on Bounding the Bypass Flow Effects

2008 ◽  
Author(s):  
Carel F. Viljoen ◽  
Sonat Sen ◽  
Frederik Reitsma ◽  
Onno Ubbink ◽  
Peter Pohl ◽  
...  
Keyword(s):  
Gas Flow ◽  
Coupled System ◽  
Pebble Bed ◽  
Pebble Bed Reactor ◽  
Control Rod ◽  
Melting Temperatures ◽  
The Core ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Effects ◽  
The Many

The AVR (Arbeitsgemeinschaft Versuchsreaktor) is a pebble bed type helium cooled graphite moderated high temperature reactor that operated in Germany for 21 years and was closed down in December 1988 [1]. The AVR melt-wire experiments [2], where graphite spheres with melt-wires of different melting temperatures were introduced into the core, indicate that measured pebble temperatures significantly exceeded temperatures calculated with the models used at the time [3]. These discrepancies are often attributed to the special design features of the AVR, in particular the control rod noses protruding into the core, and to inherent features of the pebble bed reactor. In order to reduce the uncertainty in design and safety calculations the PBMR Company is re-evaluating the AVR melt-wire experiments with updated models and tools. 3-D neutronics thermal-hydraulics analyses are performed utilizing a coupled VSOP99-STAR-CD calculation. In the coupled system VSOP99 [4] provides power profiles on a geometrical mesh to STAR-CD [5] while STAR-CD provides the fuel, moderator and solid structure temperatures to VSOP99. The different fuel histories and flow variations can be modelled with VSOP99 (although this is not yet included in the model) while the computational fluid dynamics (CFD) code, STAR-CD, adds higher-order thermal and gas flow modelling capabilities. This coupling therefore ensures that the correct thermal feedback to the neutronics is included. Of the many possible explanations for the higher-than-expected melt-wire temperatures, flow bypassing the pebble core was identified as potentially the largest contributor and was thus selected as the first topic to study. This paper reports the bounding effects of bypass flows on the gas temperatures in the top of the reactor. It also presents preliminary comparisons between measured temperatures above the core ceiling structure and calculated temperatures. Results to date confirm the importance of correctly modelling the bypass flows. Plans on future model improvements and other effects to be studied with the coupled VSOP99-STAR-CD tool are also included.

Vibration Analysis of Shrouded Turbine Blades for a 30 MW Gas Turbine

2013 ◽  
Author(s):  
Ryoji Tamai ◽  
Ryozo Tanaka ◽  
Yoshichika Sato ◽  
Karsten Kusterer ◽  
Gang Lin ◽  
...  
Keyword(s):  
Contact Force ◽  
Vibration Analysis ◽  
Turbine Blades ◽  
Forced Response ◽  
Experimental Results ◽  
Mode Shapes ◽  
Contact Friction ◽  
The Real ◽  
Bladed Disk ◽  
Resonance Frequencies

Turbine blades are subjected to high static and dynamic loads. In order to reduce the vibration amplitude means of friction damping devices have been developed, e.g. damping wires, interblade friction dampers and shrouds. This paper presents both numerical and experimental results for investigating the dynamical behavior of shrouded turbine blades. The studies are focused on the lowest family of the bladed disk. The aspect of experimental studies, the effect of the shroud contact force on the resonance frequency of the blade was examined by using the simplified blade test stand. Based on the result of the simplified blade studies, the shroud contact force of the real blade was determined in order to stabilize the resonance frequencies of the bladed disk system. The resonance frequencies and mode shapes of the real bladed disk assembly were measured in no rotation and room temperature condition. Finally, the dynamic strains were measured in the actual engine operations by using a telemetry system. The aspect of analytical studies, a non-linear vibration analysis code named DATES was applied to predict vibration behavior of a shrouded blade model which includes contact friction surfaces. The DATES code is a forced response analysis code that employs a 3-dimensional friction contact model. The Harmonic Balance Method (HBM) is applied to solve resulting nonlinear equations of motion in frequency domain. The simulated results show a good agreement with the experimental results.

Prediction of Low-Engine-Order Excitation Due to a Nonsymmetrical Nozzle Ring in a Radial Turbine by Means of the Nonlinear Harmonic Approach

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Nikola Kovachev ◽  
Tobias R. Müller ◽  
Christian U. Waldherr ◽  
Damian M. Vogt
Keyword(s):  
Computational Cost ◽  
Forced Response ◽  
Response Analysis ◽  
Cfd Models ◽  
Engine Order ◽  
Throat Width ◽  
Time Marching ◽  
Computational Fluid Dynamics Cfd ◽  
Manufacturing Tolerances ◽  
Nozzle Guide

Abstract Low engine order (LEO) excitation in a turbomachine stage can be induced by nonuniform inflow conditions, manufacturing tolerances, or in-service wear. LEOs are known to excite significant forced response vibration amplitudes that can easily cause high cycle fatigue failure of blades. The accurate prediction of LEO excitation usually requires high-fidelity computational fluid dynamics (CFD) models of the full annulus of the machine due to the loss of symmetry leading to excessive computational cost. Previous investigation showed that the aerodynamic excitation stemming from the blade-passing-frequency in a vaned radial inflow turbine can be accurately predicted by using the nonlinear harmonic (NLH) method at highly reduced computational costs. In the current paper, the feasibility of the NLH method for the prediction of LEO excitation due to geometrical asymmetries is investigated for the same test object. An exact digital replica of the nozzle guide ring is created using measured throat width data. NLH simulations resolving different combinations of frequencies and a time-marching calculation are conducted with the new model involving this digital replica. The results show that a NLH model including small number of certain frequencies is able to predict the occurring LEO excitation sufficiently accurate. By comparing results from subsequent forced response analysis with measured vibration amplitudes, a satisfactory agreement was found confirming this conclusion.

Practical Use of Unsteady CFD and FEM Forced Response Calculation in the Design of Axial Turbocharger Turbines

2005 ◽  
Author(s):  
D. Filsinger ◽  
Ch. Frank ◽  
O. Scha¨fer
Keyword(s):  
Turbine Blade ◽  
Complete Information ◽  
Forced Response ◽  
Mode Shapes ◽  
Simple Type ◽  
Reference Case ◽  
Pulse Charging ◽  
Bending Mode ◽  
Blade Vibrations ◽  
Computational Fluid Dynamics Cfd

One of the challenges in the design of rotating machinery is the issue of vibrations. The structure, no matter if talking about compressors or turbines, is subject to various sources of excitation that lead to vibrations under resonance conditions. This paper deals with the question of turbine blade vibrations. It describes practical examples of the implementation of unsteady computational fluid dynamics (CFD) and forced response calculation by means of finite element methods (FEM) applied to the design and development procedure of axial turbocharger turbines. The four examples deal with various questions which rise at different stages in the development process of turbines. One example concerns to the expected excitation of the rotor due to the stator. It demonstrates the advantages of using CFD in the prediction of this kind of excitation. Another one deals with an engine application, for which the influence of the inlet housing on the blade excitation had to be assessed. Both examples rely on the comparison of calculated excitation to the corresponding experimental strain gauge measurement for a reference case. This reference case can be used for calibration. A further case study concerns to blade vibrations in pulse charging systems. It was the intention not only to determine a spatial resolution of the excitation, but also to calculate true stresses by means of forced response calculations with FEM. In this example first bending mode shapes of the turbine blade of a rather simple type were investigated. Higher, more complex mode shapes were also investigated to prove the method. In this example, dynamic stresses were also estimated, using calculated excitation as input for forced response calculations. The results show that the use of modern numerical methods reduces cost and required time in the design of axial turbocharger turbines. They help to substantially reduce the experimental effort, while even more complete information concerning excitation and response of the structure is made available for the designer.

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