Experimental and Numerical Investigations of HPC Blisks With a Focus on Travelling Waves

2010 ◽  
Author(s):  
Ulrik Strehlau ◽  
Arnold Ku¨hhorn
Keyword(s):  
Travelling Waves ◽  
Pressure Ratio ◽  
Integrated Design ◽  
Standing Waves ◽  
Travelling Wave ◽  
Experimental Investigations ◽  
Fe Model ◽  
Mode Localization ◽  
Numerical Investigations ◽  
Aero Engines

The motivation for the usage and a further development of blade integrated disk (blisk) technology is driven by a rising demand for efficient, economical and environment-friendly aero engines. In contrast to conventional bladed disks with separated blade and disk design, blisks are either manufactured from solid or disk and blades are assembled by friction welding. Due to an optimized stress distribution, the integrated design leads to potentially higher maximum rotational speeds of the HP-shaft and thus to an improved pressure ratio. This fact offers the opportunity to reduce the number of blades or even to save whole compressor stages. In order that a significant mass-reduction is achieved, which is increased since heavy blade-disk connections of the conventional design are not necessary anymore. Apart from the advantages of the integrated design, the vibration behaviour of a real blisk is more sophisticated compared to the conventional bladed disk design. Due to the very low mechanical damping, effects like mode-localization and amplitude magnification can lead to high cycle fatigue problems of such complex structures. Extensive experimental and numerical investigations are carried out considering a real rotor-stage 1 blisk of the Rolls-Royce E3E/1 demonstrator-HPC. In order to identify “blade individual frequencies” and “blade individual damping”- values, a new patented blade by blade measurement method is used, that provides FRFs characterized by an unique resonance, as known from SDOF-systems. Based on the adjusted FE-model, numerical and experimental investigations of the vibration behaviour in the frequency range of splitted double eigenvalues are carried out. In doing so the expressions “travelling wave” and “standing waves” are commonly used to characterize the eigenmodes and forced modes of vibration respectively. The splitting of eigenvalues could be proved and a novel criterion to distinguish travelling and standing waves is introduced.

scholarly journals Approach to the numerical modelling of the chip temperatures in single grain scratching

2021 ◽  
Author(s):  
Thomas Bergs ◽  
Jannik Röttger ◽  
Sebastian Barth ◽  
Sebastian Prinz
Keyword(s):  
Experimental Validation ◽  
Numerical Models ◽  
Three Dimensional ◽  
Sufficient Accuracy ◽  
Experimental Investigations ◽  
Fe Model ◽  
Numerical Investigations ◽  
Physical Mechanisms ◽  
Fundamental Understanding ◽  
Single Grain

AbstractTo achieve a fundamental understanding of the physical mechanisms and the heat generation in the contact zone during grinding, a large number of experimental and numerical investigations have been carried out to analyse the interaction of single grain and workpiece. Existing numerical models of the interaction between grain and workpiece do not represent the reality and especially the influence of the three-dimensional grain geometry on the temperatures during single grain scratching with sufficient accuracy. An experimental validation of the simulated temperatures has not been carried out yet as there is no appropriate method to measure them in experimental investigations. In this study, a three-dimensional FE-model of the interaction between CBN-grain and workpiece (100Cr6) in the grinding process is presented. The model predicts the chip temperatures for real grain geometries to investigate the interactions between grain and workpiece. The experiments to validate the model were carried out using a ratio pyrometer.

scholarly journals Analysis of a Linear Model for Non-Synchronous Vibrations Near Stall

2021 ◽  
Vol 6 (3) ◽  
pp. 26
Author(s):  
Christoph Brandstetter ◽  
Sina Stapelfeldt
Keyword(s):  
Linear Model ◽  
Linear Models ◽  
Structural Vibration ◽  
Experimental Investigations ◽  
Vibration Modes ◽  
Critical Problem ◽  
Safety Critical ◽  
Unstable Vibration ◽  
Aero Engines ◽  
Lock In

Non-synchronous vibrations arising near the stall boundary of compressors are a recurring and potentially safety-critical problem in modern aero-engines. Recent numerical and experimental investigations have shown that these vibrations are caused by the lock-in of circumferentially convected aerodynamic disturbances and structural vibration modes, and that it is possible to predict unstable vibration modes using coupled linear models. This paper aims to further investigate non-synchronous vibrations by casting a reduced model for NSV in the frequency domain and analysing stability for a range of parameters. It is shown how, and why, under certain conditions linear models are able to capture a phenomenon, which has traditionally been associated with aerodynamic non-linearities. The formulation clearly highlights the differences between convective non-synchronous vibrations and flutter and identifies the modifications necessary to make quantitative predictions.

scholarly journals Experimental travelling waves identification in mechanical structures

2017 ◽  
Vol 24 (1) ◽  
pp. 152-167
Author(s):  
Izhak Bucher ◽  
Ran Gabai ◽  
Harel Plat ◽  
Amit Dolev ◽  
Eyal Setter
Keyword(s):  
Energy Flux ◽  
Power Flow ◽  
Reactive Power ◽  
Mechanical Energy ◽  
Travelling Waves ◽  
Electrical Power ◽  
Normal Modes ◽  
Standing Waves ◽  
Amplitude Curve ◽  
Physical Point

Vibrations are often represented as a sum of standing waves in space, i.e. normal modes of vibration. While this can be mathematically accurate, the representation as travelling waves can be compact and more appropriate from a physical point of view, in particular when the energy flux along the structure is meaningful. The quantification of travelling waves assists in computing the energy being transferred and propagated along a structure. It can provide local as well as global information about the structure through which the mechanical energy flows. Presented in this paper is a new method to quantify the fraction of mechanical power being transmitted in a vibration cycle at a specific direction in space using measured data. It is shown that the method can detect local defects causing slight non-uniformity of the energy flux. Equivalence is being made with the electrical power factor and electromagnetic standing waves ratio, commonly employed in such cases. Other methods to perform experiment based wave identification in one-dimension are compared with the power flow based identification. Including a signal processing approach that fits an ellipse to the complex amplitude curve and Hilbert transform for obtaining the local phase and amplitude. A new representation of the active and reactive power flow is developed and its relationship to standing waves ratio is demonstrated analytically and experimentally.

scholarly journals Existence and linearized stability of solitary waves for a quasilinear Benney system

2016 ◽  
Vol 146 (3) ◽  
pp. 547-564 ◽  
Author(s):  
João-Paulo Dias ◽  
Mário Figueira ◽  
Filipe Oliveira
Keyword(s):  
Solitary Wave ◽  
Solitary Waves ◽  
Compact Support ◽  
Travelling Waves ◽  
Standing Waves ◽  
Solitary Wave Solutions ◽  
Wave Solutions ◽  
Linearized Stability ◽  
Stability Of Solitary Waves ◽  
Image Position

We prove the existence of solitary wave solutions to the quasilinear Benney systemwhere , –1 < p < +∞ and a, γ > 0. We establish, in particular, the existence of travelling waves with speed arbitrarily large if p < 0 and arbitrarily close to 0 if . We also show the existence of standing waves in the case , with compact support if – 1 < p < 0. Finally, we obtain, under certain conditions, the linearized stability of such solutions.

Travelling Wave Control of Rotating Discs and Analysis of its Spillover Effect

1988 ◽  
Vol 202 (2) ◽  
pp. 119-127 ◽  
Author(s):  
C-S Kim ◽  
C-W Lee
Keyword(s):  
Travelling Waves ◽  
Spillover Effect ◽  
Polynomial Equation ◽  
Travelling Wave ◽  
Rotating Disc ◽  
System A ◽  
Finite Dimensional ◽  
Control Scheme ◽  
Actuator System ◽  
Wave Control

A modal control scheme for rotating disc systems is developed based upon the finite-dimensional sub-system model including a few lower backward travelling waves important to the disc response. For the single discrete sensor and actuator system, a polynomial equation, which determines the closed-loop system poles, is derived and the spillover effect is analysed, providing a sufficient condition for stability. Finally, simulation studies are performed to show the effectiveness of the travelling wave control scheme proposed.

TRAVELLING WAVES AND OSCILLATIONS IN SAL’NIKOV’S COMBUSTION REACTION IN A COMPRESSIBLE GAS

2015 ◽  
Vol 56 (3) ◽  
pp. 233-247 ◽  
Author(s):  
RHYS A. PAUL ◽  
LAWRENCE K. FORBES
Keyword(s):  
Asymptotic Solution ◽  
Multiple Scales ◽  
Travelling Waves ◽  
Method Of Lines ◽  
Travelling Wave ◽  
Reaction Scheme ◽  
Compressible Viscous Gas ◽  
The Method Of Lines ◽  
Temperature Waves ◽  
Parameter Values

We consider a two-step Sal’nikov reaction scheme occurring within a compressible viscous gas. The first step of the reaction may be either endothermic or exothermic, while the second step is strictly exothermic. Energy may also be lost from the system due to Newtonian cooling. An asymptotic solution for temperature perturbations of small amplitude is presented using the methods of strained coordinates and multiple scales, and a travelling wave solution with a sech-squared profile is derived. The method of lines is then used to approximate the full system with a set of ordinary differential equations, which are integrated numerically to track accurately the evolution of the reaction front. This numerical method is used to verify the asymptotic solution and investigate behaviours under different conditions. Using this method, temperature waves progressing as pulsatile fronts are detected at appropriate parameter values.

Influence of a Honeycomb Facing on the Flow Through a Stepped Labyrinth Seal

2000 ◽  
Vol 124 (1) ◽  
pp. 140-146 ◽  
Author(s):  
V. Schramm ◽  
K. Willenborg ◽  
S. Kim ◽  
S. Wittig
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Theoretical Work ◽  
Labyrinth Seal ◽  
Honeycomb Structure ◽  
Experimental Investigations ◽  
Labyrinth Seals ◽  
Numerical Predictions ◽  
Flow Through ◽  
Aero Engines

This paper reports numerical predictions and measurements of the flow field in a stepped labyrinth seal. The theoretical work and the experimental investigations were successfully combined to gain a comprehensive understanding of the flow patterns existing in such elements. In order to identify the influence of the honeycomb structure, a smooth stator as well as a seal configuration with a honeycomb facing mounted on the stator wall were investigated. The seal geometry is representative of typical three-step labyrinth seals of modern aero engines. The flow field was predicted using a commercial finite volume code with the standard k-ε turbulence model. The computational grid includes the basic seal geometry as well as the three-dimensional honeycomb structures.

A fast and accurate solution to optimal design of eddy-current PMCs with standard disc type

2021 ◽  
pp. 1-19
Author(s):  
Zheng rong Xia ◽  
Yong chen Pei ◽  
Dong xu Wang ◽  
Shun Wang
Keyword(s):  
Response Surface Methodology ◽  
Response Surface ◽  
Optimal Solution ◽  
Industrial Applications ◽  
Accurate Solution ◽  
Parameter Determination ◽  
Experimental Investigations ◽  
Fe Model ◽  
Contribution Rate ◽  
Standard Disc

Although permanent magnet couplings (PMCs) have been under research for many years and have found successful industrial applications, this is still a technology under development. Accurate parameter determination is of significance for performance analysis and critical decisions on PMC design. However, the determination can often lead to an unacceptable increase in computation, especially when finite elements (FE) are used. The study aims to develop an FE model that is used for the structural design of a standard-disc type PMC for optimal torque. For the quick and accurate design, an integration optimal solution of the response surface methodology (RSM) and the Taguchi’s method was proposed. To verify the simulation, a series of experimental investigations were conducted on a self-developed testing platform. Furthermore, for a minimum set of FE analyses (FEA), a quantitative indicator called contribution rate, which can reflect effect level of structure parameters on the torque, was given based on the Taguchi method. Apart from this, the orthogonal matrix was used for the reduction of the FE calculation. Based on the contribution rate, the response surface methodology was adopted for the optimal torque determination with no increase in the PM volume. According to the optimization results, a fitting formula, which considers the contribution rates of the optimization variables, was presented. The results suggest that the FE simulations agree very well with the experiments, and the fitting formula can be used in the PMC design.

Nonlinear travelling internal waves with piecewise-linear shear profiles

2018 ◽  
Vol 856 ◽  
pp. 984-1013 ◽  
Author(s):  
K. L. Oliveras ◽  
C. W. Curtis
Keyword(s):  
Piecewise Linear ◽  
Travelling Waves ◽  
Tangential Velocity ◽  
Travelling Wave ◽  
Numerical Continuation ◽  
Travelling Wave Solutions ◽  
Water Wave Problem ◽  
Two Fluids ◽  
Wave Solutions ◽  
Linear Shear

In this work, we study the nonlinear travelling waves in density stratified fluids with piecewise-linear shear currents. Beginning with the formulation of the water-wave problem due to Ablowitz et al. (J. Fluid Mech., vol. 562, 2006, pp. 313–343), we extend the work of Ashton & Fokas (J. Fluid Mech., vol. 689, 2011, pp. 129–148) and Haut & Ablowitz (J. Fluid Mech., vol. 631, 2009, pp. 375–396) to examine the interface between two fluids of differing densities and varying linear shear. We derive a systems of equations depending only on variables at the interface, and numerically solve for periodic travelling wave solutions using numerical continuation. Here, we consider only branches which bifurcate from solutions where there is no slip in the tangential velocity at the interface for the trivial flow. The spectral stability of these solutions is then determined using a numerical Fourier–Floquet technique. We find that the strength of the linear shear in each fluid impacts the stability of the corresponding travelling wave solutions. Specifically, opposing shears may amplify or suppress instabilities.

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.

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