scholarly journals Emergency Gate Vibration of the Pipe-Turbine Model

2000 ◽  
Vol 7 (1) ◽  
pp. 3-13 ◽  
Author(s):  
Andrej Predin ◽  
Roman Klasinc
Keyword(s):  
Data Transfer ◽  
Guide Vane ◽  
Natural Vibrations ◽  
Vibration Behavior ◽  
Kaplan Turbine ◽  
Gate Opening ◽  
Horizontal Shaft ◽  
Dynamic Similitude ◽  
The Moment ◽  
The Time Domain

The vibration behavior of an emergency gate situated on a horizontal-shaft Kaplan turbine is studied. The analysis and transfer of the dynamic movements of the gate are quite complex. In particular the behavior is examined of the emergency gate for the case when the power unit is disconnected from the system or there is a breakdown of the guide vane system at the moment when the maximal head and capacity are achieved. Experimental-numerical methods both in the time domain and in the frequency domain are employed. Natural vibrations characterize a first zone, corresponding to relatively small gate openings. As the gate opening increases, the vibration behavior of the gate becomes increasingly dependent on the swirl pulsations in the draft tube of the turbine. Finally, the data transfer from the model to the prototype by use of the dynamic similitude law is discussed.

scholarly journals The Influence of the Grid Density of Measurement Points on Damage Detection in an Isotropic Plate by the Use of Elastic Waves and Laser Scanning Doppler Vibrometry

Sensors ◽  
2021 ◽  
Vol 21 (21) ◽  
pp. 7394
Author(s):  
Łukasz Doliński ◽  
Marek Krawczuk ◽  
Magdalena Palacz ◽  
Wiktor Waszkowiak ◽  
Arkadiusz Żak
Keyword(s):  
Damage Detection ◽  
Elastic Waves ◽  
Laser Scanning ◽  
Diagnostic Methods ◽  
Mode Shapes ◽  
Engineering Practice ◽  
Natural Vibrations ◽  
Spectral Finite Element Method ◽  
The Time Domain ◽  
Spectral Finite Element

Damage detection in structural components, especially in mechanical engineering, is an important element of engineering practice. There are many methods of damage detection, in which changes in various parameters caused by the presence of damage are analysed. Recently, methods based on the analysis of changes in dynamic parameters of structures, that is, frequencies or mode shapes of natural vibrations, as well as changes in propagating elastic waves, have been developed at the highest rate. Diagnostic methods based on the elastic wave propagation phenomenon are becoming more and more popular, therefore it is worth focusing on the improvement of the efficiency of these methods. Hence, a question arises about whether it is possible to shorten the required measurement time without affecting the sensitivity of the diagnostic method used. This paper discusses the results of research carried out by the authors in this regard both numerically and experimentally. The numerical analysis has been carried out by the use of the Time-domain Spectral Finite Element Method (TD-SFEM), whereas the experimental part has been based on the measurement performed by 1-D Laser Doppler Scanning Vibrometery (LDSV).

A Straight-Forward Method of Moments Procedure to Solve the Time Domain Integral Equation Applicable to PEC Bodies via Triangular Patch Modeling

2020 ◽  
Vol 35 (8) ◽  
pp. 843-854
Author(s):  
Sadasiva Rao
Keyword(s):  
Method Of Moments ◽  
Time Domain ◽  
Moment Matrix ◽  
Triangular Patch ◽  
Gaussian Plane ◽  
Time Marching ◽  
Time Domain Integral Equation ◽  
Time Variables ◽  
The Moment ◽  
The Time Domain

In this work, a simple and straight-forward method of moments solution (MOM) procedure is presented to obtain the induced current distribution on an arbitrarily-shaped conducting body illuminated by a Gaussian plane wave directly in the time domain using a patch modeling approach. The method presented in this work, besides being stable, is also capable of handling multiple excitation pulses of varying frequency content incident from different directions in a trivial manner. The method utilizes standard Rao-Wilton-Glisson (RWG) functions and simple triangular functions for the space and time variables, respectively, for both expansion and testing. The method adopts conventional MOM and requires no further manipulation invariably needed in standard time-marching methods. The moment matrix generated via this scheme is a block-wise Toeplitz matrix and, hence, the solution is extremely efficient. The method is validated by comparing the results with the data obtained from the frequency domain solution. Several simple and complex numerical results are presented to validate the procedure.

scholarly journals A study of the strong ground motion of the Borrego Mountain, California, earthquake

1977 ◽  
Vol 67 (2) ◽  
pp. 315-330
Author(s):  
Thomas H. Heaton ◽  
Donald V. Helmberger
Keyword(s):  
Surface Wave ◽  
Half Space ◽  
Velocity Structure ◽  
Temporal Distribution ◽  
Trade Offs ◽  
Source Models ◽  
The Moment ◽  
The Time Domain ◽  
Fast Rise ◽  
Strong Ground

Abstract Several synthetic models are constructed to fit the first 40 sec of the transversely polarized displacement, as recorded at El Centro, of the April 9, 1968 Borrego Mountain earthquake. The modeling is done in the time domain using the response computed for a distributed set of point shear dislocations embedded in a layered half-space. The beginning 10 sec of the observed record is used to model the spatial and temporal distribution of faulting whereas the remaining portion is used to determine the upper crustal structure based on surface-wave periodicity. A natural depth criterion was provided by comparing the amplitude of the direct arrival with the surface-wave excitations. Trade-offs are found to exist between source models and velocity structure models. Within the framework of a layer over a half-space model, faulting of finite vertical extent is required, whereas the horizontal dimensions of faulting are not resolvable. A model which is also consistent with the teleseismic results of Burdick and Mellman indicates massive faulting near a depth of 9 km with a fast rise time producing a 10-cm displacement pulse of 1 sec duration at El Centro. The faulting appears to slow down approaching the surface. The moment is calculated to be approximately 7 ×1025 dyne-cm which is somewhat smaller than the moment found by Burdick and Mellman (1976).

scholarly journals Data Transfer Schemes in Rotorcraft Fluid-Structure Interaction Predictions

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Young H. You ◽  
Deokhwan Na ◽  
Sung N. Jung
Keyword(s):  
Data Exchange ◽  
Data Transfer ◽  
Successful Operation ◽  
Structure Interaction ◽  
Harmonic Control ◽  
Harmonic Filter ◽  
Higher Harmonic Control ◽  
Computational Structural Dynamics ◽  
The Time Domain ◽  
Coupling Algorithm

For a CFD (computation fluid dynamics)/CSD (computational structural dynamics) coupling, appropriate data exchange strategy is required for the successful operation of the coupling computation, due to fundamental differences between CFD and CSD analyses. This study aims at evaluating various data transfer schemes of a loose CFD/CSD coupling algorithm to validate the higher harmonic control aeroacoustic rotor test (HART) data in descending flight. Three different data transfer methods in relation to the time domain airloads are considered. The first (method 1) uses random data selection matched with the timewise resolution of the CSD analysis whereas the last (method 2) adopts a harmonic filter to the original signals in CFD and CSD analyses. The second (method 3) is a mixture of the two methods. All methods lead to convergent solutions after a few cycles of coupling iterations are marched. The final converged solutions for each of the data transfer methods are correlated with the measured HART data. It is found that both method 1 and method 2 exhibit nearly identical results on airloads and blade motions leading to excellent correlations with the measured data while the agreement is less satisfactory with method 3. The reason of the discrepancy is identified and discussed illustrating CFD-/CSD-coupled aeromechanics predictions.

scholarly journals An Indirect Measurement Methodology to Identify Load Fluctuations on Axial Turbine Runner Blades

Sensors ◽  
2020 ◽  
Vol 20 (24) ◽  
pp. 7220
Author(s):  
Arash Soltani Dehkharqani ◽  
Fredrik Engström ◽  
Jan-Olov Aidanpää ◽  
Michel J. Cervantes
Keyword(s):  
Guide Vane ◽  
Hydraulic Turbine ◽  
Indirect Measurement ◽  
Operating Conditions ◽  
Experimental Methodology ◽  
Unstable Flow ◽  
Pressure Transducers ◽  
Runner Blade ◽  
Kaplan Turbine ◽  
Turbine Runner

Smooth integration of intermittent energy sources, such as solar and wind power, into the electrical grid induces new operating conditions of the hydraulic turbine by increasing the off-design operations, start/stops, and load variations. Therefore, hydraulic turbines are subject to unstable flow conditions and unfavorable load fluctuations. Predicting load fluctuations on the runner using indirect measurements can allow for optimized operations of the turbine units, increase turbine refurbishment time intervals, and avoid structural failures in extreme cases. This paper investigates an experimental methodology to assess and predict the flow condition and load fluctuations on a Kaplan turbine runner at several steady-state operations by performing measurements on the shaft in the rotating and stationary frame of references. This unit is instrumented with several transducers such as miniature pressure transducers, strain gages, and proximity probes. The results show that for any propeller curve of a Kaplan turbine, the guide vane opening corresponding to the minimum pressure and strain fluctuations on the runner blade can be obtained by axial, torsion, and bending measurements on the shaft. Torsion measurements on the shaft could support index-testing in Kaplan turbines particularly for updating the cam-curve during the unit operation. Furthermore, a signature of every phenomenon observed on the runner blade signals, e.g., runner frequency, rotating vortex rope components, and rotor-stator interaction, is found in the data obtained from the shaft.

Some Applications of Spin Precession Methods to Problems in Materials Science

1980 ◽  
Vol 3 ◽  
Author(s):  
E. N. Kaufmann
Keyword(s):  
Materials Science ◽  
Spin Rotation ◽  
Spin Precession ◽  
Quantum Beats ◽  
Energy Splitting ◽  
Angular Correlations ◽  
Perturbed Angular Correlations ◽  
Energy Domain ◽  
The Moment ◽  
The Time Domain

ABSTRACTNuclear and electron resonance and the Mössbauer effect are techniques which observe the interaction of moments with fields directly in the energy domain. An energy splitting, however, also implies the precession of the moment in the field. When a means exists to determine the orientation of the moment then the precession can be observed in the time domain. The direction of radiation emitted in a nuclear, muonic or atomic decay is correlated to the direction of corresponding moments (spins) and can thus act as a detector of spin precession. In the language of nuclear, muonic and atomic physics, these methods are called perturbed angular correlations (PAC), muonic spin rotation, and quantum beats, respectively. Below, these methods will be illustrated by displaying some examples of the application of perturbed angular correlations to a variety of materials systems.

Repair of Damages that Occurred on the Welded Joints at the Body of Guide Vane Apparatus Vanes of the Vertical Kaplan Turbine

2019 ◽  
Vol 1153 ◽  
pp. 1-6
Author(s):  
Miodrag Arsić ◽  
Srđan M. Bošnjak ◽  
Vencislav Grabulov ◽  
Mladen Mladenović ◽  
Zoran Savić
Keyword(s):  
Power Plant ◽  
Welded Joints ◽  
Guide Vane ◽  
Cast Steel ◽  
Experimental Tests ◽  
The Body ◽  
Root Penetration ◽  
Hydro Power ◽  
Kaplan Turbine ◽  
Non Destructive

Vertical Kaplan turbines, with nominal power of 178 MW and manufactured in Russia, have been installed in 6 hydroelectric generating units of hydro power plant ’Djerdap 1’. Experimental tests were carried out by non-destructive methods in order to determine the turbine condition during the rehabilitation of the hydro power plant. Lack of root penetration was detected in V40 welded joints between upper and lower sleeves and bodies of guide vane apparatus vanes. Height of the lack of root penetration was in the range between 5 and 15 mm, while the allowable height of the lack of root penetration is 3 mm, according to the technical conditions. The upper sleeves were made of cast steel 25L (in accordance with GOST 977), while lower sleeves were made of steel forging St 25 (in accordance with standards GOST 1050 for chemical composition and GOST 8479 for forgings).Methodology for the repair of non-penetrated welded joints between the sleeves and body of the guide vane apparatus vane was composed taking into account the results of ultrasonic testing. By repair methodology it is necessary to, due to the structural solution and service function of guide vane apparatus vanes, specify a large number of details, consider them carefully and carry them out in order to improve safety, because if some of them get overlooked, underestimated or incorrectly perceived, significant problems in turbine operation may occur.This methodology refers solely to the repair of damaged welded joints between sleeves and bodies of guide vane apparatus vanes.

scholarly journals Numerical analysis of Darrieus vertical axis wind turbine using omni-direction guide vane

2021 ◽  
Vol 2054 (1) ◽  
pp. 012090
Author(s):  
K Sathiyamoorthy ◽  
N Nandha Sri Varma ◽  
M Showrinath
Keyword(s):  
Numerical Analysis ◽  
Performance Analysis ◽  
Guide Vane ◽  
Vertical Axis ◽  
Equation Model ◽  
Transient Simulation ◽  
Vertical Axis Wind Turbine ◽  
Operational Parameters ◽  
Air Velocity ◽  
The Moment

Abstract The performance of Darrieus turbine is studied in this paper with the attachment of ODGV to enhance its performance. The angles of guided vanes are chosen from the literature as α=20° beta=55°. According to this hypothesis the airfoil section of S1046 chosen for performance analysis. The K-ε SST 2 equation model is used for generating the moment for 5 blades turbine with the radius of 0.25m in the 2D configuration. The Chord length is chosen as 78mm and Air velocity is considered as 6m/s for the entire transient simulation. The study of performance and operational parameters have been done on turbine with presence and absence of ODGV.

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