Hydro Francis Runner Stability and Forced Response Calculations

2019 ◽  
Author(s):  
Charles Seeley ◽  
Sunil Patil ◽  
Andy Madden ◽  
Stuart Connell ◽  
Gwenael Hauet ◽  
...  
Keyword(s):  
Large Scale ◽  
Forced Response ◽  
Operating Conditions ◽  
Mode Shapes ◽  
Symmetric Model ◽  
Validation Data ◽  
Fea Model ◽  
Forcing Function ◽  
Cyclic Symmetric ◽  
Work Done

Abstract Hydroelectric power generation accounts for 7% of the total world electric energy production. Francis turbines are often employed in large-scale hydro projects and represent 60% of the total installed base. Outputs up to 800 MW are available and efficiencies of 95% are common. Cost, performance, and design cycle time are factors that continue to drive new designs as well as retrofits. This motivates the development of more sophisticated analysis tools to better assess runner performance earlier in the design phase. The focus of this paper is to demonstrate high fidelity and time-efficient runner damping and forced response calculations based on one-way fluid-structure interaction (FSI) using loosely coupled commercial finite element analysis (FEA) and computational fluid dynamics (CFD) codes. The runner damping is evaluated based on the work done by the fluid on the runner. The calculation of the work first involves determining the runner mode shapes and natural frequencies using a cyclic symmetric FEA model with structural elements to represent the runner hardware, and acoustic fluid elements to represent the mass loading effect of the fluid. The mode shapes are then used in a transient CFD calculation to determine the damping which represents the work done by the fluid on the runner. Positive damping represents stability from flutter perspective while negative damping represents unstable operating conditions. A transient CFD calculation was performed on a runner to obtain engine order forcing function from upstream stationary vanes. This unsteady forcing function was mapped to the FEA model. Care is taken to account for the proper inter-blade phase angle on the cyclic symmetric model. The hydraulic damping from flutter calculations was also provided as input to the forced response. The forced response is then determined using this equivalent proportional damping and modal superposition of the FEA model that includes both the structural and acoustic elements. Results of the developed analysis procedure are presented based on the Tokke runner, that has been the basis of several studies through the Norwegian HydroPower Center. Unique features of the workflow and modeling approaches are discussed in detail. Benefits and challenges for both the FEA model and the CFD model are discussed. The importance of the hydraulic damping, that is traditionally ignored in previous analysis is discussed as well. No validation data is available for the forced response, so this paper is focused on the methodology for the calculations.

Mixing in Large Scale Tanks: Part I — Flow Modeling of Turbulent Mixing Jets

2004 ◽  
Author(s):  
Si Young Lee ◽  
Robert A. Dimenna ◽  
Richard A. Leishear ◽  
David B. Stefanko
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Liquid Level ◽  
Computational Results ◽  
Validation Data ◽  
Flow Measurements ◽  
Three Dimensional Representation ◽  
Lower Elevation ◽  
Tank Geometry

Flow evolution models were developed to evaluate the performance of the new advanced design mixer pump (ADMP) for sludge mixing and removal operations in one of the large-scale Savannah River Site (SRS) waste tanks, Tank 18. This paper is the first in a series of four that describe the computational model and its validation, the experiment facility and the flow measurements used to provide the validation data, the extension of the computational results to real tank conditions through the use of existing sludge suspension data, and finally, the sludge removal results from actual Tank 18 operations using the new ADMP. A computational fluid dynamics (CFD) approach was used to simulate the sludge removal operations. The models employed a three-dimensional representation of the tank with a two-equation turbulence model, since this approach was verified by both test and literature data. The discharge of the ADMP was modeled as oppositely directed hydraulic jets submerged at the center of the 85-ft diameter tank, with pump suction taken from below. The calculations were based on prototypic tank geometry and nominal operating conditions. In the analysis, the magnitude of the local velocity was used as a measure of slurrying and suspension capability. The computational results showed that normal operations in Tank 18 with the ADMP mixer and a 70-in liquid level would provide adequate sludge removal in most regions of the tank. The exception was the region within about 1.2 ft of the tank wall, based on an historical minimum velocity required to suspend sludge. Sensitivity results showed that a higher tank liquid level and a lower elevation of pump nozzle would result in better performance in suspending and removing the sludge. These results were consistent with experimental observations.

Forced Response Analysis of a Transonic Fan

2012 ◽  
Author(s):  
Parthasarathy Vasanthakumar ◽  
Paul-Benjamin Ebel
Keyword(s):  
Finite Element ◽  
Flow Field ◽  
Forced Response ◽  
Navier Stokes ◽  
Response Analysis ◽  
Aerodynamic Damping ◽  
Forcing Function ◽  
Transonic Fan ◽  
Work Done ◽  
Highly Loaded

The forced response of turbomachinery blades is a primary source of high cycle fatigue (HCF) failure. This paper deals with the computational prediction of blade forced response of a transonic fan stage that consists of a highly loaded rotor along with a tandem stator. In the case of a transonic fan, the forced response of the rotor due to the downstream stator assumes significance because of the transonic flow field. The objective of the present work is to determine the forced response of the rotor induced as a result of the unsteady flow field due to the downstream stator vanes. Three dimensional, Navier-Stokes flow solver TRACE is used to numerically analyse the forced response of the fan. A total of 11 resonant crossings as identified in the Campbell diagram are examined and the corresponding modeshapes are obtained from finite element modal analysis. The interaction between fluid and structure is dealt with in a loosely coupled manner based on the assumption of linear aerodynamic damping. The aerodynamic forcing is obtained by a nonlinear unsteady Navier-Stokes computation and the aerodynamic damping is obtained by a time-linearized Navier-Stokes computation. The forced response solution is obtained by the energy method allowing calculations to be performed directly in physical space. Using the modal forcing and damping, the forced response amplitude can be directly computed at the resonance crossings. For forced response solution, the equilibrium amplitude is reached when the work done on the blade by the external forcing function is equal to the work done by the system damping (aerodynamic and structural) force. A comprehensive analysis of unsteady aerodynamic forces on the rotor blade surface as a result of forced response of a highly loaded transonic fan is carried out. In addition, the correspondence between the location of high stress zones identified from the finite element analysis and the regions of high modal force identified from the CFD analysis is also discussed.

Influence of Disc Modes and Sideband Excitations on the Mistuned Forced Response Behaviour of an Embedded Compressor Rotor

2021 ◽  
Author(s):  
Shreyas Hegde ◽  
Andrew Madden ◽  
Robert Kielb
Keyword(s):  
Computational Cost ◽  
Axial Compressor ◽  
Travelling Wave ◽  
Forced Response ◽  
Operating Conditions ◽  
Operating Condition ◽  
Compressor Rotor ◽  
Forcing Function ◽  
Highly Sensitive ◽  
The Individual

Abstract This paper focusses on predicting the mistuned forced response behavior of an embedded compressor rotor blade row in a 3.5 stage axial compressor. The authors in previous papers studied the multi-row influence on the forcing function for multiple operating conditions. For these investigations CFX was utilized to predict the forcing However, in the mistuned predictions a consistent underprediction of the amplification factor was noted A previous investigation by the authors [32] considered an isolated mode family. The current work considers the same configuration but looks at a non-isolated mode family which is in a frequency “veering” region. Also, since the mistuning code was formulated on the lines of the fundamental mistuning model (FMM) the model only included a single DOF per ND and hence modes in the veering region were not modeled. The current paper addresses both these shortcomings and talks about the influence of sideband travelling wave excitations at the HL operating condition (the details of the mistuned predictions at the PE operating condition can be found in [32]). The paper also talks in detail about the effect of modelling the disc modes individually using the FMM model as well as together using the component mistuning model (CMM) as present in ANSYS Mechanical. Key conclusions are: 1) The mistuned response tends to be amplified by all cases including the sideband excitations, 2) The coupled influence of including a disc mode in the FMM model and sideband excitations is dependent on the proximity of the mode to the blade alone frequency, 3) Although the CMM model predicts the peak of the response accurately, it does not offer any substantial advantage over the FMM model given the computational cost required for the CMM prediction. Also, the prediction is highly sensitive to the frequency of the individual modes that can differ between codes.

The Time-Variant Aerodynamic Response of a Stator Row Including the Effects of Airfoil Camber

1980 ◽  
Vol 102 (2) ◽  
pp. 334-342 ◽  
Author(s):  
S. Fleeter ◽  
W. A. Bennett ◽  
R. L. Jay
Keyword(s):  
Flat Plate ◽  
Pressure Difference ◽  
Large Scale ◽  
State Of The Art ◽  
Dynamic Pressure ◽  
Pressure Coefficient ◽  
Forced Response ◽  
Phase Lag ◽  
Forcing Function ◽  
Wide Range

An experimental investigation was conducted to quantitatively determine the validity and applicability of state-of-the-art transverse gust cascade analyses. This was accomplished by obtaining fundamental time-variant forced response data at realistic values of key parameters in a large-scale, low-speed, single-stage research compressor. The forcing function, the velocity defect created by the rotor blade wakes, was measured with a crossed hot-wire probe. The resulting time-variant aerodynamic response was measured by means of flush mounted high response pressure transducers on both flat plate and cambered airfoil stator vane rows over a wide range of incidence angles. These dynamic data were then analyzed to determine the chordwise variation of the unsteady pressure difference in terms of a dimensionless dynamic pressure coefficient and an aerodynamic phase lag referenced to a transverse gust at the leading edge of the vanes. These dimensionless pressure difference data were all correlated with predictions obtained from a state-of-the-art compressible transverse gust, flat plate cascade analysis. Correlation of the classical flat plate unsteady data with the predictions permitted the range of validity of the analysis to be assessed in terms of incidence angle. Correlation of the cambered vane unsteady data with those for the flat plate and with the predictions allowed the effects of airfoil camber as well as the applicability of the flat plate prediction to realistic cambered airfoils to be quantitatively determined.

Wake Induced Time-Variant Aerodynamics Including Rotor-Stator Axial Spacing Effects

1981 ◽  
Vol 103 (1) ◽  
pp. 59-66 ◽  
Author(s):  
S. Fleeter ◽  
R. L. Jay ◽  
W. A. Bennett
Keyword(s):  
Large Scale ◽  
Primary Source ◽  
Forced Response ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Experimental Program ◽  
Axial Distance ◽  
Spacing Effects ◽  
Spacing Ratio ◽  
Wide Range

The overall objective of this experimental program was to quantify the effects of rotor-stator axial spacing on the fundamental time-variant aerodynamics relevant to forced response in turbomachinery. This was accomplished in a large-scale, low-speed, single-stage research compressor which permitted two rotor-stator axial spacing ratios representative of those found in advanced design compressors to be investigated. At each value of the axial spacing ratio, the aerodynamically induced fluctuating surface pressure distributions on the downstream vane row, with the primary source of excitation being the upstream rotor wakes, were measured over a wide range of compressor operating conditions. The velocity fluctuations created by the passage of the rotor blades were measured in the nonrotating coordinate system. Data obtained described the variation of the rotor wake with both loading and axial distance from the rotor as parameters. These data also served as a reference in the analysis of the resulting time-variant pressure signals on the vane surfaces.

Sensitivity of Tuned Bladed Disk Response to Frequency Veering

2004 ◽  
Author(s):  
J. A. Kenyon ◽  
J. H. Griffin ◽  
N. E. Kim
Keyword(s):  
Forced Response ◽  
Mode Interaction ◽  
Mode Shapes ◽  
Disk Model ◽  
Bladed Disk ◽  
Modal Response ◽  
Generalized Force ◽  
Cyclic Symmetric ◽  
Fixed Reference ◽  
Interblade Phase Angle

A continuous method is presented for representing the mode interaction that occurs in frequency veering in terms of the nominal sector modes of a cyclic symmetric bladed disk model constrained at a fixed reference interblade phase angle. Using this method, the effect of frequency veering on the mode shapes can be considered in the context of the generalized forces exciting the system and the modal response of the bladed disk. It is shown that in a blade-dominated family of modes, the transfer of modal energy to the disk in the veering results in a lower generalized force exciting the mode as well as reduced response amplitude in the blade. For the disk-dominated modes, the sharing of modal energy with the blades can lead to the disk being excited by aerodynamic loading. These effects can have important implications for predicting and interpreting forced response in bladed disks. Numerical examples are provided to illustrate these concepts.

scholarly journals Analysis of Bifurcations in Multiharmonic Analysis of Nonlinear Forced Vibrations of Gas Turbine Engine Structures With Friction and Gaps

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
E. P. Petrov
Keyword(s):  
Gas Turbine ◽  
Large Scale ◽  
Parameter Variation ◽  
Forced Vibrations ◽  
Forced Response ◽  
Operating Conditions ◽  
Frequency Domain Method ◽  
Cubic Nonlinearity ◽  
Turbine Engine ◽  
Detection And Localization

An efficient frequency-domain method has been developed to analyze the forced response of large-scale nonlinear gas turbine structures with bifurcations. The method allows detection and localization of the design and operating conditions sets where bifurcations occur, calculation of tangents to the solution trajectory, and continuation of solutions under parameter variation for structures with bifurcations. The method is aimed at calculation of steady-state periodic solution, and multiharmonic representation of the variation of displacements in time is used. The possibility of bifurcations in realistic gas-turbine structures with friction contacts and with cubic nonlinearity has been shown.

High Fidelity Transient Forced Response Analysis of Mistuned Bladed Disks Under Complex Excitation and Variable Rotation Speeds

2020 ◽  
Author(s):  
Jing Tong ◽  
Chaoping Zang ◽  
Evgeny Petrov
Keyword(s):  
Large Scale ◽  
Rotation Speed ◽  
Dynamic Properties ◽  
Spectral Composition ◽  
Forced Response ◽  
Mode Shapes ◽  
Response Analysis ◽  
Bladed Disks ◽  
Bladed Disk ◽  
Amplitude Amplification

Abstract An effective method is developed for the efficient calculation of the transient vibration response for mistuned bladed disks under complex excitation and varying rotation speeds. The method uses the large-scale finite element modelling of the bladed disks allowing the accurate description of the dynamic properties of the mistuned bladed disks. The realistic distributions of the excitation forces are considered, which resulted in the multiharmonic excitation loads. The transient response calculation is based on the analytically derived expressions for the transient forced response and the effective method used for the model reduction. The effects of the varying rotation speed on the natural frequencies and mode shapes of the mistuned bladed disk and its effects on the amplitude and the spectral composition of the loading are allowed for. The different functions of the rotation speed variation can be analyzed. Numerical studies of the transient forced response and the amplitude amplification in mistuned bladed disks are performed when the resonance regimes are passed during gas-turbine engine acceleration or deceleration. The effects of different types of excitation force and mistuning on transient amplitude amplification are illustrated by a large number of the computational results and comparative analysis. These results and analysis of transient forced response are shown on an example of a realistic mistuned bladed disk.

An Analysis System for Blade Forced Response

1993 ◽  
Vol 115 (4) ◽  
pp. 762-770 ◽  
Author(s):  
Hsiao-Wei D. Chiang ◽  
R. E. Kielb
Keyword(s):  
Unsteady Aerodynamics ◽  
Forced Response ◽  
Design Tool ◽  
Mode Shapes ◽  
Solution Technique ◽  
Campbell Diagram ◽  
Inlet Distortion ◽  
Forcing Function ◽  
Strip Theory ◽  
Analysis System

A frequent cause of turbomachinery blade failure is excessive resonant response. The most common excitation source is the nonuniform flow field generated by inlet distortion, wakes and/or pressure disturbances from adjacent blade rows. The standard method for dealing with this problem is to avoid resonant conditions using a Campbell diagram. Unfortunately, it is impossible to avoid all resonant conditions. Therefore, judgments based on past experience are used to determine the acceptability of the blade design. A new analysis system has been developed to predict blade forced response. The system provides a design tool, over and above the standard Campbell diagram approach, for predicting potential forced response problems. The incoming excitation sources are modeled using a semi-empirical rotor wake/vortex model for wake excitation, measured data for inlet distortion, and a quasi-three-dimensional Euler code for pressure disturbances. Using these aerodynamic stimuli, and the blade’s natural frequencies and mode shapes from a finite element model, the unsteady aerodynamic modal forces and the aerodynamic damping are calculated. A modal response solution is then performed. This system has been applied to current engine designs. A recent investigation involved fan blade response due to inlet distortion. An aero mechanical test had been run with two different distortion screens. The resulting distortion entering the fan was measured. With this as input data, the predicted response agreed almost exactly with the measured response. In another application, the response of the LPT blades of a counterrotating supersonic turbine was determined. In this case the blades were excited by both a wake and a shock wave. The shock response was predicted to be three times larger than that of the wake. Thus, the system identified a new forcing function mechanism for supersonic turbines. This paper provides a basic description of the system, which includes: (1) models for the wake excitation, inlet distortion, and pressure disturbance; (2) a kernel function solution technique for unsteady aerodynamics; and (3) a modal aeroelastic solution using strip theory. Also, results of the two applications are presented.

Sensitivity of Tuned Bladed Disk Response to Frequency Veering

2004 ◽  
Vol 127 (4) ◽  
pp. 835-842 ◽  
Author(s):  
J. A. Kenyon ◽  
J. H. Griffin ◽  
N. E. Kim
Keyword(s):  
Forced Response ◽  
Mode Interaction ◽  
Mode Shapes ◽  
Disk Model ◽  
Bladed Disk ◽  
Aerodynamic Loading ◽  
Modal Response ◽  
Generalized Force ◽  
Cyclic Symmetric ◽  
Interblade Phase Angle

A continuous method is presented for representing the mode interaction that occurs in frequency veering in terms of the nominal sector modes of a cyclic symmetric bladed disk model constrained at a reference interblade phase angle. Using this method, the effect of frequency veering on the mode shapes can be considered in the context of the generalized forces exciting the system and the modal response of the bladed disk. It is shown that in a blade-dominated family of modes, the transfer of modal energy to the disk in the veering results in a lower generalized force exciting the mode as well as reduced response amplitude in the blade. For the disk-dominated modes, the sharing of modal energy with the blades can lead to the disk being excited by aerodynamic loading. These effects can have important implications for predicting and interpreting forced response in bladed disks. Numerical examples are provided to illustrate these concepts.

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