Analysis of the Effect of Multirow and Multipassage Aerodynamic Interaction on the Forced Response Variation in a Compressor Configuration—Part II: Effects of Additional Structural Mistuning

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Johann Gross ◽  
Malte Krack ◽  
Harald Schoenenborn
Keyword(s):  
Epistemic Uncertainty ◽  
Three Dimensional ◽  
Forced Response ◽  
Fe Model ◽  
Aerodynamic Loading ◽  
Blade Row ◽  
Random Mistuning ◽  
Dynamic Forcing ◽  
Response Variation ◽  
Turbomachinery Design

The prediction of aerodynamic blade forcing is a very important topic in turbomachinery design. Usually, the wake from the upstream blade row and the potential field from the downstream blade row are considered as the main causes for excitation, which in conjunction with relative rotation of neighboring blade rows, give rise to dynamic forcing of the blades. In addition to those two mechanisms, the so-called Tyler–Sofrin (or scattered or spinning) modes, which refer to the acoustic interaction with blade rows further up- or downstream, may have a significant impact on blade forcing. In particular, they lead to considerable blade-to-blade variations of the aerodynamic loading. In Part I of the paper, a study of these effects is performed on the basis of a quasi-three-dimensional multirow and multipassage compressor configuration. Part II of the paper proposes a method to analyze the interaction of the aerodynamic forcing asymmetries with the already well-studied effects of random mistuning stemming from blade-to-blade variations of structural properties. Based on a finite element (FE) model of a sector, the equations governing the dynamic behavior of the entire bladed disk can be efficiently derived using substructuring techniques. The disk substructure is assumed as cyclically symmetric, while the blades exhibit structural mistuning and linear aeroelastic coupling. In order to avoid the costly multistage analysis, the variation of the aerodynamic loading is treated as an epistemic uncertainty, leading to a stochastic description of the annular force pattern. The effects of structural mistuning and stochastic aerodynamic forcing are first studied separately and then in a combined manner for a blisk of a research compressor without and with aeroelastic coupling.

Analysis of the Effect of Multi-Row and Multi-Passage Aerodynamic Interaction on the Forced Response Variation in a Compressor Configuration: Part 2 — Effects of Additional Structural Mistuning

2017 ◽  
Author(s):  
Johann Gross ◽  
Malte Krack ◽  
Harald Schoenenborn
Keyword(s):  
Epistemic Uncertainty ◽  
Element Model ◽  
Forced Response ◽  
Aerodynamic Loading ◽  
Multi Stage ◽  
Blade Row ◽  
Random Mistuning ◽  
Response Variation ◽  
Stage Analysis ◽  
Turbomachinery Design

The prediction of aerodynamic blade forcing is a very important topic in turbomachinery design. Usually, the wake from the upstream blade row and the potential field from the downstream blade row are considered as the main causes for excitation, which in conjunction with relative rotation of neighboring blade rows, give rise to dynamic forcing of the blades. In addition to those two mechanisms so-called Tyler-Sofrin (or scattered or spinning) modes, which refer to the acoustic interaction with blade rows further up- or downstream, may have a significant impact on blade forcing. In particular, they lead to considerable blade-to-blade variations of the aerodynamic loading. In part 1 of the paper a study of these effects is performed on the basis of a quasi 3D multi-row and multi-passage compressor configuration. Part 2 of the paper proposes a method to analyze the interaction of the aerodynamic forcing asymmetries with the already well-studied effects of random mistuning stemming from blade-to-blade variations of structural properties. Based on a finite element model of a sector, the equations governing the dynamic behavior of the entire bladed disk can be efficiently derived using substructuring techniques. The disk substructure is assumed as cyclically symmetric, while the blades exhibit structural mistuning and linear aeroelastic coupling. In order to avoid the costly multi-stage analysis, the variation of the aerodynamic loading is treated as an epistemic uncertainty, leading to a stochastic description of the annular force pattern. The effects of structural mistuning and stochastic aerodynamic forcing are first studied separately and then in a combined manner for a blisk of a research compressor without and with aeroelastic coupling.

Analysis of the Effect of Multirow and Multipassage Aerodynamic Interaction on the Forced Response Variation in a Compressor Configuration—Part I: Aerodynamic Excitation

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Harald Schoenenborn
Keyword(s):  
Three Dimensional ◽  
Forced Response ◽  
Frame Of Reference ◽  
Aerodynamic Damping ◽  
Aerodynamic Interaction ◽  
Blade Row ◽  
Random Mistuning ◽  
Compressor Map ◽  
Response Variation ◽  
Turbomachinery Design

The aeroelastic prediction of blade forcing is still a very important topic in turbomachinery design. Usually, the wake from an upstream airfoil and the potential field from a downstream airfoil are considered as the main disturbances. In recent years, it became evident that in addition to those two mechanisms, Tyler–Sofrin modes, also called scattered or spinning modes, may have a significant impact on blade forcing. It was recently shown in literature that in multirow configurations, not only the next but also the next but one blade row is very important as it may create a large circumferential forcing variation, which is fixed in the rotating frame of reference. In the present paper, a study of these effects is performed on the basis of a quasi three-dimensional (3D) multirow and multipassage compressor configuration. For the analysis, a harmonic balancing code, which was developed by DLR Cologne, is used for various setups and the results are compared to full-annulus unsteady calculations. It is shown that the effect of the circumferentially different blade excitation is mainly contributed by the Tyler–Sofrin modes and not to blade-to-blade variation in the steady flow field. The influence of various clocking positions, coupling schemes and number of harmonics onto the forcing is investigated. It is also shown that along a speed-line in the compressor map, the blade-to-blade forcing variation may change significantly. In addition, multirow flutter calculations are performed, showing the influence of the upstream and downstream blade row onto aerodynamic damping. The effect of these forcing variations onto random mistuning effects is investigated in the second part of the paper.

Analysis of the Effect of Multi-Row and Multi-Passage Aerodynamic Interaction on the Forced Response Variation in a Compressor Configuration: Part 1 — Aerodynamic Excitation

2017 ◽  
Author(s):  
Harald Schoenenborn
Keyword(s):  
Forced Response ◽  
Frame Of Reference ◽  
Rotating Frame ◽  
Aerodynamic Damping ◽  
Aerodynamic Interaction ◽  
Blade Row ◽  
Random Mistuning ◽  
Compressor Map ◽  
Response Variation ◽  
Turbomachinery Design

The aeroelastic prediction of blade forcing is still a very important topic in turbomachinery design. Usually, the wake from an upstream airfoil and the potential field from a downstream airfoil are considered as the main disturbances. In recent years, it became evident that in addition to those two mechanisms Tyler-Sofrin modes, also called scattered or spinning modes, may have a significant impact on blade forcing. In Schrape et al. [9] it was found that in multi-row configurations not only the next, but also the next but one blade row is very important as it may create a large circumferential forcing variation which is fixed in the rotating frame of reference. In the present paper a study of these effects is performed on the basis of a quasi 3D multi-row and multi-passage compressor configuration. For the analysis a harmonic balancing code, which was developed by DLR Cologne, is used for various setups and the results are compared to full-annulus unsteady calculations. It is shown that the effect of the circumferentially different blade excitation is mainly contributed by the Tyler-Sofrin modes and not to blade-to-blade variation in the steady flow field. The influence of various clocking positions, coupling schemes and number of harmonics onto the forcing is investigated. It is also shown that along a speed-line in the compressor map the blade-to-blade forcing variation may change significantly. In addition, multi-row flutter calculations are performed, showing the influence of the upstream and downstream blade row onto aerodynamic damping. The effect of these forcing variations onto random mistuning effects is investigated in the second part of the paper.

Forced Response Variation of Aerodynamically and Structurally Mistuned Turbo-Machinery Rotors

2006 ◽  
Author(s):  
I. Sladojevic´ ◽  
E. P. Petrov ◽  
M. Imregun ◽  
A. I. Sayma
Keyword(s):  
Three Dimensional ◽  
Forced Response ◽  
Navier Stokes ◽  
Fe Model ◽  
Frequency Shifts ◽  
Aero Engine ◽  
Different Types ◽  
Aerodynamic Parameters ◽  
Reynolds Averaged Navier Stokes ◽  
Response Variation

The paper presents the results of a study looking into changes in the forced response levels of bladed disc assemblies subject to both structural and aerodynamic mistuning. A whole annulus FE model, representative of a civil aero-engine fan with 26 blades was used in the calculations. The forced response of all blades of 1000 random mistuned patterns was calculated. The aerodynamic parameters, frequency shifts and damping, were calculated using a three-dimensional Reynolds-averaged Navier-Stokes aero-elasticity code. They were randomly varied for each mistuning pattern, with the assumption that the system would remain stable, i.e. flutter would not occur due to aerodynamic mistuning. The results show the variation of the forced response with different types of mistuning, with structural mistuning only, with aerodynamic mistuning only and with both structural and aerodynamic mistuning.

The exploitation of three-dimensional flow in turbomachinery design

1998 ◽  
Vol 213 (2) ◽  
pp. 125-137 ◽  
Author(s):  
J. D. Denton ◽  
L Xu
Keyword(s):  
Three Dimensional ◽  
Axial Flow ◽  
Field Calculation ◽  
3D Flow ◽  
Three Dimensional Flow ◽  
Approximate Methods ◽  
Blade Row ◽  
3D Effects ◽  
Flow Effects ◽  
Turbomachinery Design

Many of the phenomena involved in turbomachinery flow can be understood and predicted on a two-dimensional (2D) or quasi-three-dimensional (Q3D) basis, but some aspects of the flow must be considered as fully three-dimensional (3D) and cannot be understood or predicted by the Q3D approach. Probably the best known of these fully 3D effects is secondary flow, which can only be predicted by a fully 3D calculation which includes the vorticity at inlet to the blade row. It has long been recognized that blade sweep and lean also produce fully 3D effects and approximate methods of calculating these have been developed. However, the advent of fully 3D flow field calculation methods has made predictions of these complex effects much more readily available and accurate so that they are now being exploited in design. This paper will attempt to describe and discuss fully 3D flow effects with particular reference to their use to improve turbomachine performance. Although the discussion is restricted to axial flow machines, many of the phenomena discussed are equally applicable to mixed and radial flow turbines and compressors.

scholarly journals Novel Frame Model for Mistuning Analysis of Bladed Disk Systems

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Jie Yuan ◽  
Fabrizio Scarpa ◽  
Branislav Titurus ◽  
Giuliano Allegri ◽  
Sophoclis Patsias ◽  
...  
Keyword(s):  
Computational Cost ◽  
Three Dimensional ◽  
Maximum Amplitude ◽  
Forced Response ◽  
Full Scale ◽  
Fe Model ◽  
Response Dynamics ◽  
Frame Model ◽  
Bladed Disk ◽  
Beam Frame

The work investigates the application of a novel frame model to reduce computational cost of the mistuning analysis of bladed disk systems. A full-scale finite element (FE) model of the bladed disk is considered as benchmark. The frame configuration for a single blade is identified through structural identification via an optimization process. The individual blades are then assembled by three-dimensional (3D) springs, whose parameters are determined by means of a calibration process. The dynamics of the novel beam frame assembly is also compared to those obtained from three state-of-the-art FE-based reduced order models (ROMs), namely: a lumped parameter approach, a Timoshenko beam assembly, and component mode synthesis (CMS)-based techniques with free and fixed interfaces. The development of these classical ROMs to represent the bladed disk is also addressed in detail. A methodology to perform the mistuning analysis is then proposed and implemented. A comparison of the modal properties and forced response dynamics between the aforementioned ROMs and the full-scale FE model is presented. The case study considered in this paper demonstrates that the beam frame assembly can predict the variations of the blade amplitude factors, and the results are in agreement with full-scale FE model. The CMS-based ROMs underestimate the maximum amplitude factor, while the results obtained from beam frame assembly are generally conservative. The beam frame assembly is four times more computationally efficient than the CMS fixed-interface approach. This study proves that the beam frame assembly can efficiently predict the mistuning behavior of bladed disks when low-order modes are of interest.

A Multi Blade-Row Linearised Analysis Method for Flutter and Forced Response Predictions in Turbomachinery

2006 ◽  
Author(s):  
Gabriel Saiz ◽  
Mehmet Imregun ◽  
Abdulnaser I. Sayma
Keyword(s):  
Travelling Waves ◽  
Three Dimensional ◽  
Forced Response ◽  
Navier Stokes ◽  
Test Case ◽  
Test Cases ◽  
Simple Test ◽  
Analysis Method ◽  
Turbine Stage ◽  
Blade Row

A three-dimensional time-linearised unsteady Navier-Stokes solver is presented for the computation of multistage unsteady flow in turbomachinery. The objective is to address multistage aeroelastic effects for both flutter and forced response. Since the method is currently being developed, only forced response applications are studied in this paper. With this approach, travelling waves, known as spinning modes, are propagated across the multistage domain in order to take into account the interaction between the blade-rows. The method is first validated over two simple test cases for which analytical solutions were available. It is then tested on a turbine stage test case and multistage effects are evaluated from the contribution of one spinning mode included in the model. The results are compared with both time-linearised single-row and nonlinear multirow methods. Multi-row effects are shown not to be important in this case. However, the test case serves as a validation for the implementation of the methodology and further work will focus on the implementation of several spinning modes and the computations of forced response and flutter cases with several blade-rows.

Forcing Function Measurements and Predictions of a Transonic Vaneless Counter Rotating Turbine

2000 ◽  
Author(s):  
Matthew M. Weaver ◽  
Steven R. Manwaring ◽  
Reza S. Abhari ◽  
Michael G. Dunn ◽  
Michael J. Salay ◽  
...  
Keyword(s):  
High Pressure ◽  
Three Dimensional ◽  
Unsteady Aerodynamics ◽  
Forced Response ◽  
Physical Parameters ◽  
Outer Diameter ◽  
Detailed Knowledge ◽  
Unsteady Forces ◽  
Forcing Function ◽  
Blade Row

Reducing the vibratory stress due to the forced response excitation of turbomachinery blades is an important engineering challenge facing designers. Detailed knowledge of the unsteady forces, the damping within the system, and the structural stiffness is required to predict the vibrational response and hence the high cycle fatigue life of a component. This study is focused on understanding the physical parameters influencing the unsteady forces causing the blade excitation in a transonic vaneless counter-rotating turbine, consisting of a vane row, a High Pressure (HP) spool, and a Low Pressure (LP) spool. Time averaged and time resolved measurements of the unsteady surface pressures on the HP and LP rotor blades are presented for a full scale rotating rig, using the actual engine components. Measurements were made and analyses performed at three different engine corrected aerodynamic conditions and with reduced frequencies (based on half blade chord) of approximately 10 for the unsteady aerodynamics. By varying the high-pressure rotor exit Mach number (1.44, 1.20, 1.05), the effects of varying the shock excitation to the LP blade row was studied. Extensive comparisons with CFD codes were obtained to determine flow-modeling requirements for the flow regimes studied. Comparison shows that for steady loading on the LP blade, 2D, single blade row Euler solvers are sufficient to achieve engineering accuracies. For the 1st harmonic unsteady loading, this level of modeling is adequate in the mid and lower half of the blade, but in the outer diameter region, three-dimensional effects require 3D modeling. The inclusion of nonlinear/viscous modeling shows moderately improved predictions.

scholarly journals Numerical Analysis of the Perforated Steel Sheets Under Uni-Axial Tensile Force

Metals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 632 ◽  
Author(s):  
Ahmed M. Sayed
Keyword(s):  
Load Capacity ◽  
Tensile Force ◽  
Three Dimensional ◽  
Tensile Load ◽  
Experimental Tests ◽  
Strain Engineering ◽  
Uniaxial Tensile ◽  
Fe Model ◽  
Stress Strain ◽  
Steel Sheets

The perforated steel sheets have many uses, so they should be studied under the influence of the uniaxial tensile load. The presence of these holes in the steel sheets certainly affects the mechanical properties. This paper aims at studying the behavior of the stress-strain engineering relationships of the perforated steel sheets. To achieve this, the three-dimensional finite element (FE) model is mainly designed to investigate the effect of this condition. Experimental tests were carried out on solid specimens to be used in the test of model accuracy of the FE simulation. Simulation testing shows that the FE modeling revealed the ability to calculate the stress-strain engineering relationships of perforated steel sheets. It can be concluded that the effect of a perforated rhombus shape is greater than the others, and perforated square shape has no effect on the stress-strain engineering relationships. The efficiency of the perforated staggered or linearly distribution shapes with the actual net area on the applied loads has the opposite effect, as it reduces the load capacity for all types of perforated shapes. Despite the decrease in load capacity, it improves the properties of the steel sheets.

scholarly journals Through-Flow Analysis for Axial-Stage Design Including Streamline-Slope Effects

1993 ◽  
Author(s):  
Theodosios Korakianitis ◽  
Dequan Zou
Keyword(s):  
Mass Flow ◽  
Three Dimensional ◽  
Momentum Equation ◽  
Total Enthalpy ◽  
Streamline Curvature ◽  
Flow Balance ◽  
Through Flow ◽  
Blade Row ◽  
Iteration Loop ◽  
Predictor Corrector

This paper presents a new method to design (or analyze) subsonic or supersonic axial compressor and turbine stages and their three-dimensional velocity diagrams from hub to tip by solving the three-dimensional radial-momentum equation. Some previous methods (matrix through-flow based on the streamfunction approach) can not handle locally supersonic flows, and they are computationally intensive when they require the inversion of large matrices. Other previous methods (streamline curvature) require two nested iteration loops to provide a converged solution: an outside iteration loop for the mass-flow balance; and an inside iteration loop to solve the radial momentum equation at each flow station. The present method is of the streamline-curvature category. It still requires the iteration loop for the mass-flow balance, but the radial momentum equation at each flow station is solved using a one-pass numerical predictor-corrector technique, thus reducing the computational effort substantially. The method takes into account the axial slope of the streamlines. Main design characteristics such as the mass-flow rate, total properties at component inlet, hub-to-tip ratio at component inlet, total enthalpy change for each stage, and the expected efficiency of each streamline at each stage are inputs to the method. Other inputs are the radial position and axial velocity component at one surface of revolution through the axial stages. These can be provided for either the hub, or the mean, or the tip location of the blading. In addition the user specifies the azimuthal deflection of the flow from the axial direction at each radius (or as a function of radius) at each blade row inlet and outlet. By construction the method eliminates radial variations of total enthalpy (work) and entropy at each blade row inlet and outlet. In an alternative formulation enthalpy variations across radial positions at each axial station are included in the analysis. The remaining three-dimensional velocity diagrams from hub to tip, and the radial location of the remaining streamlines, are obtained by solving the momentum equation using a predictor-corrector method. Examples for one turbine and one compressor design are included.

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