Optimizing Instrumentation When Measuring Jet Engine Blade Vibration

1992 ◽  
Vol 114 (2) ◽  
pp. 217-221 ◽  
Author(s):  
J. H. Griffin
Keyword(s):  
Analytical Model ◽  
Blade Vibration ◽  
Alternative Strategies ◽  
Jet Engine ◽  
Bladed Disk ◽  
Statistical Variations ◽  
Engine Blade ◽  
System Frequency

An analytical model of bladed disk vibration is used to calculate the statistical variations in blade amplitudes that can occur in mistuned turbomachinery blading. The results provide a basis for evaluating alternative strategies for instrumenting the stage. This approach is illustrated by applying it to an unshrouded fan stage. It is found for this stage that the best strategy is to instrument blades that have frequencies near the tuned system frequency. A procedure is proposed for establishing how gages should be allocated from stage to stage throughout the engine.

scholarly journals Optimizing Instrumentation When Measuring Jet Engine Blade Vibration

1991 ◽  
Author(s):  
J. H. Griffin
Keyword(s):  
Analytical Model ◽  
Blade Vibration ◽  
Alternative Strategies ◽  
Jet Engine ◽  
Bladed Disk ◽  
Statistical Variations ◽  
Engine Blade ◽  
System Frequency

An analytical model of bladed disk vibration is used to calculate the statistical variations in blade amplitudes that can occur in mistuned turbomachinery blading. The results provide a basis for evaluating alternative strategies for instrumenting the stage. This approach is illustrated by applying it to an unshrouded fan stage. It is found for this stage that the best strategy is to instrument blades that have frequencies near the tuned system frequency. A procedure is proposed for establishing how gages should be allocated from stage to stage throughout the engine.

Vibrations of Bladed-Disk Assemblies—A Selected Survey (Survey Paper)

1984 ◽  
Vol 106 (2) ◽  
pp. 165-168 ◽  
Author(s):  
A. V. Srinivasan
Keyword(s):  
Experimental Research ◽  
Recent Progress ◽  
Blade Vibration ◽  
Jet Engine ◽  
General Review ◽  
Survey Paper ◽  
Bladed Disk ◽  
The Many ◽  
Made In

The progress made in the decade 1973–1983 in the area of vibration of jet engine blades is surveyed. The purpose of the survey is to provide a general review of recent progress and the limited number of references cited can be used to reach the many other important publications in this area. Both structural and aerodynamic aspects of blade vibration are discussed, although the emphasis is on the former. The areas of future analytical and experimental research needed to continue to influence the design of these components are outlined.

scholarly journals Improved Reliability of Bladed Disks due to Friction Dampers

1997 ◽  
Author(s):  
Walter Sextro ◽  
Karl Popp ◽  
Ivo Wolter
Keyword(s):  
Dry Friction ◽  
Three Dimensional ◽  
Line Contact ◽  
Two Dimensional ◽  
Centrifugal Forces ◽  
Friction Damper ◽  
Blade Vibration ◽  
Friction Dampers ◽  
Bladed Disk ◽  
Bladed Disk Assembly

Friction dampers are installed underneath the blade platforms to improve the reliability. Because of centrifugal forces the dampers are pressed onto the platforms. Due to dry friction and the relative motion between blades and dampers, energy is dissipated, which results in a reduction of blade vibration amplitudes. The geometry of the contact is in many cases like a Hertzian line contact. A three-dimensional motion of the blades results in a two-dimensional motion of one contact line of the friction dampers in the contact plane. An experiment with one friction damper between two blades is used to verify the two-dimensional contact model including microslip. By optimizing the friction dampers masses, the best damping effects are obtained. Finally, different methods are shown to calculate the envelope of a three-dimensional response of a detuned bladed disk assembly (V84.3-4th-stage turbine blade) with friction dampers.

scholarly journals Mistuning Effects on the Nonlinear Friction Saturation of Flutter Vibration Amplitude

2020 ◽  
Author(s):  
Carlos Martel ◽  
Salvador Rodríguez
Keyword(s):  
Vibration Amplitude ◽  
Gas Flow ◽  
Travelling Waves ◽  
Computational Cost ◽  
Travelling Wave ◽  
Nonlinear Friction ◽  
Blade Vibration ◽  
Bladed Disk ◽  
Spring System ◽  
Mass Spring

Abstract The blade vibration level of an aerodynamically unstable rotor is a quantity of crucial importance to correctly estimate the blade fatigue life. This amplitude is the result of the balance between the energy pumped into the blades by the gas flow, and the nonlinear dissipation at the blade-disk contact interfaces. In a tuned configuration, the blade displacements can be described as a travelling wave consisting of one fundamental nodal diameter and frequency and its higher harmonics, and the problem can be reduced to the computation of a time periodic solution in just one sector. This simplification is no longer valid for a mistuned bladed disk. The resulting nonlinear vibration of the mistuned system is a combination of several travelling waves with different number of nodal diameters, coupled through mistuning. In this case, the complete bladed disk has to be considered, which requires an extremely high computational cost, and, for this reason, reduced order models (ROM) are required to analyze this situation. In this work, we use a 3 DOF/sector mass-spring system to describe the nonlinear friction saturation of the flutter vibration amplitude of a realistic mistuned bladed disk. The convergence of the solution of the mass-spring system is still quite slow because of the presence of many unstable modes with very similar growth rates. In order to speed-up the simulations a simpler asymptotic ROM is derived from the mass-spring model, which allows for much faster integration times. The simulations of the asymptotic ROM are compared with the measurements obtained in the European project FUTURE, where an aerodynamically unstable LPT rotor was tested with different intentional mistuning patterns.

Monocarbide Characterization In Nickel-Base Mc Aligned Eutectics

1981 ◽  
Vol 12 ◽  
Author(s):  
M.R. Jackson ◽  
M.F.X. Gigliotti ◽  
S.W. Yang ◽  
J.L. Walter
Keyword(s):  
Chemical Analysis ◽  
Lattice Parameter ◽  
Lattice Parameters ◽  
Quantitative Chemical Analysis ◽  
Eutectic Alloys ◽  
Free Energies ◽  
Jet Engine ◽  
Engine Blade ◽  
Nickel Base ◽  
Quantitative Chemical

ABSTRACTIn the aligned Ni-MC eutectic alloys being developed for jet engine blade applications, the fibers are considered to be Tac, Tic, etc. In fact, these fibers will contain Cr, Mo, W and possibly other elements as substitutions for the “M” constituent, and often will not be stoichiometric. Quantitative chemical analysis of fibers is difficult because of their size. However, lattice parameter measurements can be used to learn much a out the carbide chemistry and stoichiometry. Results will be described in detail for fibers extracted from simple Ni-TaC, Ni,Cr-TaC and Ni,Cr,AI-Tac systems. In addition, experiments on mixed (Ta,V)C and (Ta,Ti)C carbides will be discussed. Carbide lattice parameters can be understood in terms of the free energies of formation of the various carbides.

Recent Blade Vibration Techniques

1967 ◽  
Vol 89 (3) ◽  
pp. 437-444 ◽  
Author(s):  
E. K. Armstrong
Keyword(s):  
Service Life ◽  
Fatigue Properties ◽  
Compressor Blades ◽  
Blade Vibration ◽  
Jet Engine ◽  
Vibration Data ◽  
Intake Flow

The methods which have been used recently to predict the amplitudes of vibration of compressor blades are explained. Examples for resonances with maldistributions in the intake flow and downstream blockages are given. Two techniques of obtaining blade vibration data from the HP shaft of a two-shaft jet engine are described. By comparing the measured amplitudes with the fatigue properties of blading, a parameter has been established which is used in assessing the seriousness of a vibration when considering its service life.

Numerical Investigations of Localized Vibrations of Mistuned Blade Integrated Disks (Blisks)

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
T. Klauke ◽  
A. Kühhorn ◽  
B. Beirow ◽  
M. Golze
Keyword(s):  
Strain Energy ◽  
Vibration Modes ◽  
Blade Vibration ◽  
Nodal Diameter ◽  
Mode Localization ◽  
Bladed Disk ◽  
High Pressure Compressor ◽  
Localized Vibrations ◽  
Pressure Compressor ◽  
Higher Sensitivity

Blade-to-blade variations of bladed disk assemblies result in local zoning of vibration modes as well as amplitude magnifications, which primarily reduces the high cycle fatigue life of aeroengines. Criteria were introduced to determine the level of these mode localization effects depending on various parameters of a real high pressure compressor blisk rotor. The investigations show that blade vibration modes with lower interblade coupling, e.g., torsion modes or modes with high numbers of nodal diameter lines, have a significantly higher sensitivity to blade mistuning, which can be characterized by the higher percentage of blades on the total blisk strain energy.

Alternate Mistuning of Turbine Bladings Coupled by Underplatform Dampers

2012 ◽  
Author(s):  
S. Tatzko ◽  
L. Panning-von Scheidt ◽  
J. Wallaschek ◽  
A. Kayser
Keyword(s):  
Turbine Blades ◽  
Steady State Solution ◽  
Computational Effort ◽  
Forced Response ◽  
Nonlinear Coupling ◽  
Cyclic Symmetry ◽  
Periodic Excitation ◽  
Blade Vibration ◽  
Mode Localization ◽  
Bladed Disk

In turbo machinery design it is important to avoid vibrations that can destroy the turbine in the last resort. The rotating structure is exposed to periodic excitation forces. Two main types of periodic excitation can be distinguished. Flutter is the effect when mass flow forces couple with a natural vibration mode. The result is a negative damping coefficient and amplitudes will rise up to malfunction of the structure. The engine order excitation is a periodic excitation where the force signal is directly related to the speed of the rotor. A forced response calculation gives information about the blade vibration. Nonlinear coupling, i.e. friction coupling, between blades is used to increase damping of the bladed disk. Dynamic analysis of turbine blades with nonlinear coupling is a complex task and computer simulations are inevitable. Various techniques have been developed to reduce computational effort. The cyclic symmetry approach assumes each blade around the disk to be identical. Thus only one sector of the disk is sufficient to compute the steady state solution of the whole turbine blading. However, it has been observed that mistuning of blades reduces the flutter instability. On the other hand statistical mistuning can lead to dangerously high forced response amplitudes due to mode localization. A compromise is intentional mistuning. The simplest approach is alternate mistuning with every other blade exhibiting identical mechanical properties. This work explains in detail how a turbine bladed disk can be modeled when alternate mistuning is applied intentionally. Cyclic symmetry is used and each sector comprises two blades. This untypical choice of the sector size has significant impact on results of a cyclic modal analysis. Simulation results show the influence of alternate mistuned turbine bladings which are coupled by underplatform damper elements.

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.

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