Mistuning Identification Approach With Focus on High-Speed Centrifugal Compressors

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Robby Weber ◽  
Arnold Kühhorn
Keyword(s):  
Experimental Data ◽  
High Speed ◽  
Common Knowledge ◽  
Optical Measurements ◽  
Fe Model ◽  
Blade Vibration ◽  
Mode Localization ◽  
Characteristic Quantity ◽  
Calculation Results ◽  
Geometric Deviations

Blade vibrations are one of the main cost drivers in turbomachinery. Computational blade vibration analysis facilitates an enormous potential to increase the productivity in the design of bladed components. Increasing computing power as well as improved modeling and simulation methods leads to comprehensive calculation results. This allows for a more precise prediction and assessment of experimental data. Usually, in the field of turbomachinery, identical blades are assumed to lower the required computational resources. However, mistuning is unavoidable, since small deviations due to the manufacturing process will lead to slightly different blade behavior. Potential effects such as mode localization and amplification can be treated statistically and have been thoroughly studied in the past. Since then, several reduced order models (ROMs) have been invented in order to calculate the maximum vibration amplitude of a fleet of mistuned blisks. Most commonly, mistuning is thereby modeled by small material deviations from blade to blade, e.g., Young's modulus or density. Nowadays, it is common knowledge that the level of manufacturing imperfection (referred as level of mistuning) significantly influences mode localization as well as vibration amplification effects. Optical measurements of the geometric deviations of manufactured blades and converting to a high-fidelity finite element (FE) model make huge progress. However, to the knowledge of the authors, there is no reliable method that derives a characteristic quantity from the geometric mistuning, that fits into the mentioned statistically approaches. Therefore, experimental data are needed to quantify the level of mistuning. Several approaches, which isolate blade individual parameters, are used to identify the dynamic behavior of axial compressors and turbines. These methods can be applied to medium-speed centrifugal turbine wheels but tend to fail to evaluate high-speed compressor with splitter blades. This paper briefly presents the original approach and discusses the reasons for failure. Thereafter, a new approach is proposed. Finally, the level of mistuning and important quantities to perform a statistical evaluation of a high-speed compressor is shown.

Mistuning Identification Approach With Focus on High-Speed Centrifugal Compressors

2018 ◽  
Author(s):  
Robby Weber ◽  
Arnold Kühhorn
Keyword(s):  
Experimental Data ◽  
High Speed ◽  
Common Knowledge ◽  
Element Model ◽  
Optical Measurements ◽  
Blade Vibration ◽  
Mode Localization ◽  
Characteristic Quantity ◽  
Calculation Results ◽  
Geometric Deviations

Blade vibrations are one of the main cost drivers in turbo-machinery. Computational blade vibration analysis facilitates an enormous potential to increase the productivity in the design of bladed components. Increasing computing power as well as improved modeling and simulation methods lead to comprehensive calculation results. This allows for a more precise prediction and assessment of experimental data. Usually, in the field of turbomachinery, identical blades are assumed to lower the required computational resources. However, mistuning is unavoidable, since small deviations due to the manufacturing process will lead to slightly different blade behavior. Potential effects such as mode localization and amplification can be treated statistically and have been thoroughly studied in the past. Since then, several reduced order models (ROMs) have been invented in order to calculate the maximum vibration amplitude of a fleet of mistuned blisks. Most commonly, mistuning is thereby modeled by small material deviations from blade to blade, e.g. Young’s modulus or density. Nowadays, it is common knowledge that the level of manufacturing imperfection (referred as level of mistuning) significantly influence mode localization as well as vibration amplification effects. Optical measurements of the geometric deviations of manufactured blades and converting to a high-fidelity finite element model make huge progress. However, to the knowledge of the authors, there is no reliable method, that derives a characteristic quantity from the geometric mistuning, that fits into the mentioned statistically approaches. Therefore, experimental data is needed to quantify the level of mistuning. Several approaches, which isolate blade individual parameters, are used to identify the dynamic behavior of axial compressors and turbines. These methods can be applied to medium-speed centrifugal turbine wheels but tend to fail to evaluate high-speed compressor with splitter blades. This paper briefly presents the original approach and discusses the reasons for failure. Thereafter, a new approach is proposed. Finally the level of mistuning and important quantities to perform a statistical evaluation of a high-speed compressor is shown.

Mistuning Modeling and its Validation for Small Turbine Wheels

2013 ◽  
Author(s):  
David Hemberger ◽  
Dietmar Filsinger ◽  
Hans-Jörg Bauer
Keyword(s):  
Amplification Factor ◽  
Numerical Models ◽  
Lower Sensitivity ◽  
Fe Model ◽  
Mode Localization ◽  
Geometric Deviations ◽  
Probabilistic Study ◽  
Calculated Amplitude ◽  
Amplitude Amplification ◽  
The Ideal

The production of bladed structures, e.g. turbine and compressor wheels, is a subject of statistical scatter. The blades are designed to be identical but differ due to small manufacturing tolerances. This so called mistuning can lead to increased vibration amplitudes compared to the ideal tuned case. The object of this study is to create and validate numerical models to evaluate such mistuning effects of turbine wheels for automotive turbocharger applications. As a basis for the numerical analysis vibration measurements under stand-still conditions were carried out by using a laser surface velocimeter (LSV). The scope of this investigation was to identify the mistuning properties of the turbine wheels namely the frequency deviation from the ideal, cyclic symmetrical tuned system. Experimental modal analyses as well as blade by blade measurements were performed. Moreover 3D scanning techniques were employed to determine geometric deviations. Numerical FE models and a simplified multi degree of freedom model (EBM) were created to reproduce the measured mistuning effects. The prediction of mode localization and the calculated amplitude amplification were evaluated. The best results were obtained with a FE model that employs individual sectorial stiffnesses. The results also indicate that the major contribution to mistuning is made by material inhomogeneities and not by geometric deviations from ideal dimensions. With the adjusted FE model a probabilistic study has been performed to investigate the influence of the mistuning on the amplitude amplification factor. It has been found that at a certain level of mistuning the amplification factor remains constant or slightly decreases. By introducing intentional mistuning a lower sensitivity as well as a decrease of the amplitude amplification could be achieved.

Measurement Procedure of Ring Motion with the Use of Highspeed Camera During Electromagnetic Expansion

2012 ◽  
Vol 19 (4) ◽  
pp. 797-804 ◽  
Author(s):  
Jacek Janiszewski
Keyword(s):  
Experimental Data ◽  
Flow Stress ◽  
Plastic Flow ◽  
High Speed ◽  
Optical Measurement ◽  
Measurement Procedure ◽  
Expansion Process ◽  
Calculation Results ◽  
Plastic Flow Stress ◽  
Ring Material

Abstract An optical measurement method of radial displacement of a ring sample during its expansion with velocity of the order 172 m/s and estimation technique of plastic flow stress of a ring material on basis of the obtained experimental data are presented in the work. To measure the ring motion during the expansion process, the Phantom v12 digital high-speed camera was applied, whereas the specialized TEMA Automotive software was used to analyze the obtained movies. Application of the above-mentioned tools and the developed measuring procedure of the ring motion recording allowed to obtain reliable experimental data and calculation results of plastic flow stress of a copper ring with satisfactory accuracy.

Finite Element Modeling of Aortic Tissue Using High Speed Experimental Data

2005 ◽  
Author(s):  
Muralikrishna Maddali ◽  
Chirag S. Shah ◽  
King H. Yang
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
High Speed ◽  
Material Model ◽  
Traumatic Rupture ◽  
Aortic Tissue ◽  
Model Parameters ◽  
Fe Model ◽  
Rubber Material ◽  
Material Constants

Traumatic rupture of the aorta (TRA) is responsible for 10% to 20% of motor vehicle fatalities [1]. Both finite element (FE) modeling and experimental investigations have enhanced our understanding of the injury mechanisms associated with TRA. Because accurate material properties are essential for the development of correct and authoritative FE model predictions, the objective of the current study was to identify a suitable material model and model parameters for aorta tissue that can be incorporated into FE aorta models for studying TRA. An Ogden rubber material (Type 77B in LS-DYNA 970) was used to simulate a series of high speed uniaxial experiments reported by Mohan [2] using a dumbbell shaped FE model representing human aortic tissue. Material constants were obtained by fitting model simulation results against experimentally obtained corridors. The sensitivity of the Ogden rubber material model was examined by altering constants G and alpha (α) and monitoring model behavior. One single set of material constants (α = 25.3, G = 0.02 GPa, and μ = 0.6000E-06 GPa) was found to fit uniaxial data at strain rates of approximately 100 s−1 for both younger and older aortic tissue specimens. Until a better material model is derived and other experimental data are obtained, it is recommended that the Ogden material model and associated constants derived from the current study be used to represent aorta tissue properties when using FE methods to investigate mechanisms of TRA.

Experimental and Numerical Analysis of Geometrical Induced Mistuning

2015 ◽  
Author(s):  
Frederik Popig ◽  
Peter Hönisch ◽  
Arnold Kühhorn
Keyword(s):  
Vibration Analysis ◽  
Optical Measurement ◽  
Measurement Data ◽  
Point Of View ◽  
Optical Measurements ◽  
Experimental Point ◽  
Fe Model ◽  
Mode Localization ◽  
Blisk Blade ◽  
The Impact

The application of high pressure compressor (HPC) rotors manufactured as blisk (Blade Integrated Disk) is ever-expanding in modern jet engine designs. Despite the major advantages of less mass and higher efficiency, the most challenging problem is lower mechanical damping due to the loss of damping between blades root’s and the disk. Mistuning is induced by material inhomogeneities, manufacturing tolerances or wear during use and leads to amplitude magnification and mode localization. From the experimental point of view mistuning can be evaluated via experimental vibration analysis in terms of frequency deviations. Furthermore optical measurements can be evaluated in terms of geometrical deviations between the real and designed geometry. From the structural point of view a mistuned blisk model can be obtained by morphing the nodes of the geometrical tuned FE model or by performing blade individual stiffness mistuning due to modification of Young’s modulus. The following work is focused on the numerical prediction of mistuned blisk vibrations. Therefore, the research blisk of the 4 stage research compressor, manufactured as job-production, is analyzed. For this research blisk optical measurement data as well as experimentally obtained frequency patterns are available. In a first part mistuning identification in terms of experimental vibration analysis and Proper Orthogonal Decomposition of the geometrical deviations is presented. In a second part mistuning modeling in terms of stiffness mistuning and geometrical mistuning is applied to the tuned FE-model and the numerical results are evaluated against experimental data regarding accuracy. Furthermore, the impact of geometrical deviations on mistuning is analyzed.

scholarly journals Tip-Timing Measurements and Numerical Analysis of Last-Stage Steam Turbine Mistuned Bladed Disc During Run-Down

2019 ◽  
Vol 8 (3) ◽  
pp. 409-415 ◽  
Author(s):  
Romuald Rzadkowski ◽  
Leszek Kubitz ◽  
Michał Maziarz ◽  
Pawel Troka ◽  
Krzysztof Dominiczak ◽  
...  
Keyword(s):  
Steam Turbine ◽  
Natural Frequencies ◽  
Timing Analysis ◽  
Mode Shapes ◽  
Fe Model ◽  
Blade Vibration ◽  
Nodal Diameter ◽  
Mode Localization ◽  
Numerical Studies ◽  
Last Stage

Abstract Background This paper presents the experimental and numerical studies of last-stage low-pressure (LP) mistuned steam turbine bladed discs during run-down. Methods The natural frequencies and mode shapes of the turbine bladed disc were calculated using an FE model. The influence of the shaft on the modal properties, such as natural frequencies and mode shapes, was considered. The tip-timing method was used to find the mistuned bladed disc modes and frequencies. Conclusions The experimental results from the tip-timing analysis show that the mistuning in combination with shaft coupling suppresses pure nodal diameter type blade vibrations associated with the fundamental mode shape of a cantilevered blade. Vibration modes emerge when even a single blade is vibrating due to the well-known mode localization caused by mistuning. The numerical results confirm this.

Evolving one-dimensional transient jet modeling by integrating jet breakup physics

2017 ◽  
Vol 18 (9) ◽  
pp. 909-929 ◽  
Author(s):  
Nicholas Neal ◽  
David Rothamer
Keyword(s):  
Experimental Data ◽  
High Speed ◽  
Volume Fraction ◽  
Liquid Core ◽  
Optical Measurements ◽  
Gas Jet ◽  
One Dimensional ◽  
Transient Nature ◽  
Radial Profiles ◽  
Ambient Gas

High-speed optical measurements of unsteady liquid fuel jets under engine-like conditions have shown that the initial penetration of the jets does not follow the behavior predicted by previously introduced one-dimensional jet models based on gas-jet principles. The experimental data indicate that the transient jet penetration velocity is initially controlled by the jet exit velocity, transitioning to gas-jet like mixing-dominated penetration further downstream. This behavior is consistent with the common description of high-pressure fuel jets as containing a liquid core surrounded by entrained gas and fuel droplets. In this paper, a new one-dimensional modeling methodology is introduced that couples the transport equations for the evolution of the liquid core of the jet and the surrounding sheath of droplets resulting from breakup. This allows for the penetration of the jet to be initially governed by the liquid core, which is relatively unaffected by the ambient gas, transitioning to spray penetration dominated by the entrained ambient gas. The model also provides a defined jet centerline velocity, which allows for the shape of the radial profiles of fuel velocity and fuel volume fraction to be solved for directly, without the need for a steady-jet assumption, as was used in previous one-dimensional models. This change removes the need for a constant momentum flux assumption, improving the transient nature of the model. The results of the model are validated against the aforementioned optical transient jet measurements. The model and all associated experimental data have been made available for use at rothamer.erc.wisc.edu/dlp .

scholarly journals Blade Vibrations of a High Speed Compressor Blisk-Rotor: Numerical Resonance Tuning and Optical Measurements

1996 ◽  
Author(s):  
J. Frischbier ◽  
G. Schulze ◽  
M. Zielinski ◽  
G. Ziller ◽  
C. Blaha ◽  
...  
Keyword(s):  
Rotor Blade ◽  
High Speed ◽  
Mechanical Design ◽  
Optimization Technique ◽  
Optical Measurements ◽  
Vibration Measurement ◽  
Blade Vibration ◽  
Transonic Compressor ◽  
Resonance Tuning ◽  
Blade Vibrations

A major challenge during the design process of a modern low aspect ratio high speed axial compressor is to find rotor blade geometries that meet both, aerodynamic and mechanical requirements. This paper deals with the mechanical design of a transonic compressor blade. In order to meet the mechanical requirements in a short development time, new methods were used: A numerical optimization tool and an optical blade vibration measurement method: The numerical resonance tuning took advantage of a semi-automatic optimization technique, based on a Finite Element vibration anlysis tool. The intention was to find a geometry which has no critical resonances (with fundamental engine orders) within the operation range. To verify the calculated blade natural frequencies and eigen-values standard shaker tests using a laser holography system were carried out. Blades under g-load in the running compressor were investigated with an in-house developed vibration measurement system. This system is able to measure frequencies and amplitudes of the rotor blade vibrations without blade instrumentation but small optical probes, mounted in the compressor casing. The measured resonance points are in good agreement with the predictions. All amplitudes are far below the blade fatigue limits.

Refined thermal calculation of the locomotive heat engine collector

2020 ◽  
pp. 56-58
Author(s):  
P.V. Gubarev ◽  
D.V. Glazunov ◽  
V.G. Ruban ◽  
A.S. Shapshal
Keyword(s):  
Experimental Data ◽  
Electric Motor ◽  
Heat Balance ◽  
Thermal Imaging ◽  
Heat Engine ◽  
Thermal Calculation ◽  
Calculation Results ◽  
Cooling Air ◽  
The Heat Balance ◽  
Traction Electric Motor

The thermal calculation of the locomotive traction engine collector is proposed. The equations of the heat balance of its elements are obtained taking into account the cooling air. The calculation results and experimental data of thermal imaging control are presented. Keywords: traction electric motor, collector, thermal calculation, thermal imaging control. [email protected]

Dynamic Analysis of DVG 850 High-Speed Machining Center

2012 ◽  
Vol 487 ◽  
pp. 203-207
Author(s):  
Gong Xue Zhang ◽  
Xiao Kai Shen
Keyword(s):  
High Speed ◽  
Simulation Analysis ◽  
Response Analysis ◽  
Improved Method ◽  
Analysis Software ◽  
Element Analysis ◽  
Harmonic Response ◽  
Machining Center ◽  
Calculation Results ◽  
Harmonic Response Analysis

Purpose, with the application of workbench finite element analysis software, get the analysis results of DVG 850 high-speed vertical machining center via the modal analysis and harmonic response analysis. Use the calculation results for reference, put forward the improved method, and prove the credibility of the simulation analysis by testing DVG 850 prototype.

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