Dynamic Investigation on a Pelton Runner: FEM Calculation and Experimental Results

2007 ◽  
Author(s):  
Emanuel Pesatori ◽  
Giorgio Turozzi ◽  
Paolo Pennacchi ◽  
Alessandro Tosi
Keyword(s):  
High Performance ◽  
Natural Frequencies ◽  
Numerical Data ◽  
Point Of View ◽  
Normal Operation ◽  
Mode Shapes ◽  
Modal Behavior ◽  
Dynamic Investigation ◽  
Strong Dynamic ◽  
Structural Point

The dynamical phenomena involving a Pelton runner during normal operation are getting more and more of concern in the design of such kind of turbines. In fact, the increasing of the performance required by the market imposes runner designs that can become critical from a structural point of view. Each bucket is subjected to a certain number of impulses per revolution corresponding to the number of nozzles. This high frequency load could lead to a strong dynamic response of the runner if some kind of resonance takes place. For these reasons, an accurate modal analysis is to be performed before the runner realization, in order to avoid any crack arising during operation. This paper describes how a new, high performance profiled Pelton runner was modeled and dynamically calculated by FEM code ANSYS in order to obtain its natural frequencies and mode shapes. Subsequently, the modal behavior of the runner was experimentally investigated by means of an impulse test on field. The natural frequencies were got by examinating the FFT of the response and the mode shapes were reconstructed according to the stored signals of the accelerometers. The match between the experimental and numerical data was pretty good.

scholarly journals Localization of Increased Noise at Operating Speed of a Passenger Wagon

2021 ◽  
Vol 13 (2) ◽  
pp. 453
Author(s):  
Ján Ďungel ◽  
Peter Zvolenský ◽  
Juraj Grenčík ◽  
Lukáš Leštinský ◽  
Ján Krivda
Keyword(s):  
Natural Frequencies ◽  
Internal Noise ◽  
High Volume ◽  
Acoustic Properties ◽  
Normal Operation ◽  
Mode Shapes ◽  
Railway Transport ◽  
Noise Sources ◽  
Sound Fields ◽  
Real Picture

Noise generated by railway wagons in operation is produced by large numbers of noise sources. Although the railway transport is considered to be environmental friendly, especially in production of CO2 emissions, noise is one of problems that should be solved to keep the railway transport competitive and sustainable in future. In the EU, there is a strong permanent legislation pressure on interior and exterior noise reduction in railway transport. In the last years in Slovakia, besides modernization of existing passenger wagons fleet as a cheaper option of transport quality improvement, quite a number of coaches have been newly manufactured, too. The new design is usually aimed at increased speed, higher travel comfort, in which reduction of noise levels is expected. However, not always the new designs meet all expectations. Noise generation and propagation is a complex system and should be treated such from the beginning. There are possibilities to simulate the structural natural frequencies to predict vibrations and sound generated by these vibrations. However, the real picture about sound fields can be obtained only by practical measurements. Simulations of the wagon’s natural frequencies and mode shapes and measurements in real operation using a digital acoustic camera Soundcam have been done, which showed that for the calculated speeds the largest share of noise from the chassis was not radiated through the floor of the wagon, as was expected, but through the ceiling of the wagon. To improve the acoustic properties of the wagon at higher speed, it was proposed to use high-volume textile insulation in the ceiling of the wagon. The paper briefly presents modern research approaches in the search for ways to reduce internal noise in selected wagons used in normal operation on the Slovak railways.

Structural Dynamics and Load Analysis of Large Offshore Wind Turbines in Western Gulf of Mexico Shallow Water

2014 ◽  
Author(s):  
Ling Ling Yin ◽  
King Him Lo ◽  
Su Su Wang
Keyword(s):  
Gulf Of Mexico ◽  
Wind Turbine ◽  
Shallow Water ◽  
Structural Dynamics ◽  
Natural Frequencies ◽  
Offshore Wind ◽  
Normal Operation ◽  
Mode Shapes ◽  
Offshore Wind Turbine ◽  
Support Structure

In this paper, a study is conducted on wind and metocean loads and associated structural dynamics of a 13.2-MW large offshore wind turbine in Western Gulf of Mexico (GOM) shallow water. The offshore wind turbine considered includes a rotor with three 100-meter long blades and a mono-tower support structure. Natural frequencies and mode shapes of the blades and the mono-tower are determined first and used subsequently to establish a Campbell diagram for safe wind turbine operation. The results show that hydrodynamic added mass has little effect on the natural frequencies and mode shapes of the support structure but it introduces, in part, appreciable effects on loads carried by the turbine when the blades are pitched at wind speeds above the rated speed. Also determined, for normal operation and extreme metocean conditions (i.e., 100-year return hurricanes), are normal thrust on the wind rotor, blade-tip displacement, overturning moment and tower-top displacement sustained by the wind turbine.

A New Method for Dynamic Analysis of Pelton Runners Using CFD/FEM Interaction

2009 ◽  
Author(s):  
Massimiliano Sanvito ◽  
Luisa Coscarelli ◽  
Emanuel Pesatori ◽  
Giorgio Turozzi ◽  
Paolo Pennacchi
Keyword(s):  
Dynamic Response ◽  
Harmonic Analysis ◽  
Dynamic Behavior ◽  
High Frequency ◽  
Pressure Profile ◽  
Point Of View ◽  
New Method ◽  
Normal Operation ◽  
Impulse Load ◽  
Structural Point

The description of the dynamic behavior of a Pelton runner during normal operation is getting more and more of interest in the design of such kind of turbines. In fact, the aim to increase the performance imposes runner designs that can become critical from a structural point of view. Each bucket is subjected to a certain number of impulses per revolution corresponding to the number of nozzles. This high frequency load could lead to a great dynamic response of the runner if some kind of resonance takes place. For these reasons, a complex harmonic analysis is to be performed during the runner project, in order to avoid any crack arising during operation. This paper describes a new method to obtain the dynamic response due to the impulse load. A Pelton runner was modeled and simulated by using a FEM code (ANSYS) and a CFD (CFX) code in order to obtain its complete dynamic behavior. By using the CFD code the complete pressure profile was derived at any point of the bucket and at any time. Whilst by using the FEM code a complex harmonic analysis was computed. Combining the information of these two simulations the behavior of the stress versus time can be derived, theoretically at any point of the runner. The results of these analysis were compared with some experimental data giving a pretty good matching.

Structural Modification of a Pipe Under Harmonic Excitation Using an Hybrid Numerical/Experimental Method

2011 ◽  
Author(s):  
Charles Bodel
Keyword(s):  
Modal Analysis ◽  
Nuclear Power ◽  
Natural Frequencies ◽  
Harmonic Excitation ◽  
Experimental Modal Analysis ◽  
Point Of View ◽  
Mode Shapes ◽  
Design Stage ◽  
Centrifugal Pumps ◽  
Structural Dynamic

Vibrations generated by centrifugal pumps are difficult to predict at the design stage, for it is hardly possible to accurately determine the natural frequencies of pipes and to avoid coincidences with the blade pass frequency of the pump and its harmonics. One is often led to modify the existing structure, by adding stiffness, mass or damping. This paper illustrates this point on a pipe connected to a pump in a nuclear power plant operated by EDF (E´lectricite´ de France). In October 2010, abnormal vibrations were measured on a thin pipe at the outlet of a pump in a powerplant in France. The French nuclear regulatory commission asked EDF to perform a diagnosis and to define solutions within a few months. EDF/R&D division has used an original method developed in 2004 based on hybrid data, and called LMME-SDM (for Local Model Mode-shapes Expansion Structural Dynamic Modification). The main objective is to define a structure modification able to remove all natural frequencies close to the harmonic excitation. For the purpose of the study, we need a numerical model, which should be fairly correct from a static point of view, but which is not necessarily updated from a dynamic point of view, and an experimental modal analysis carried out under real conditions on the pipe. During the experimental modal analysis, a test of added mass has been carried out so that the method can be validated by comparing the predicted and the observed frequency. This method has already been used in industrial cases in former studies [3], however the study presented here has reached a higher level in complexity. Even if this method is able to give reasonable results compared to measurements, it is close to its limits.

Experimental and Numerical Analysis of Read/Write Head Suspension Dynamics for High-Performance Floppy Drive Systems

1990 ◽  
Vol 112 (1) ◽  
pp. 26-32 ◽  
Author(s):  
G. M. Frees ◽  
D. K. Miu
Keyword(s):  
Finite Element ◽  
Numerical Analysis ◽  
High Performance ◽  
Laser Doppler Vibrometer ◽  
Numerical Data ◽  
Floppy Disk ◽  
Element Model ◽  
Operating Conditions ◽  
Tracking Performance ◽  
Mode Shapes

Read/write head suspensions are critical components of high-performance floppy disk drives. Their dynamics affect head/media compliance, wear, and tracking performance. Vibration measurements are necessary in order to verify and adjust finite element models, to observe the influence of actual loading and operating conditions, and to study the effects of unmodeled components such as electrical wires and adhesives. A nonintrusive measurement technique using a Laser Doppler Vibrometer is utilized to measure the submicron vibrations. Excitation of the suspension is provided by a specially designed miniature air hammer and a piezoelectric transducer. Natural frequencies and mode shapes are extracted from the measurements and compared with numerical data from the finite element model. Research shows that boundary conditions are the most important parameters in the modeling of the suspension. A new design is proposed, using the verified model, to increase the tracking performance of the suspension. Synergy between experimentation and numerical analysis is emphasized.

The Frequency Veering Phenomena of the Beams of Cantilever Screen

2012 ◽  
Vol 226-228 ◽  
pp. 580-583 ◽  
Author(s):  
Ming Ming Li ◽  
Fang Zhen Song ◽  
Chuan Guang Ding
Keyword(s):  
Dynamic Characteristics ◽  
Stiffness Matrix ◽  
Natural Frequencies ◽  
Point Of View ◽  
Special Structure ◽  
Mode Shapes ◽  
Analysis Method ◽  
Hollow Beam ◽  
Coupling Stiffness ◽  
Regular Mode

The special structure of beams of cantilever screen has the advantages comparing with the traditional screen and special dynamic characteristics, such as the dynamic characteristics of frequency veering. The traditional analysis method of vibrating screen is not applicable to its dynamic analysis because of the special structure. By analysis and decomposition of stiffness matrix of beams of cantilever screen, the frequency veering phenomenon of the beam of cantilever screen was explained from the point of view of modal energy equation and the influence of sub-stiffness matrix of beams of cantilever screen on the frequency veering was analyzed. The analysis results showed that the sub-stiffness matrix of the hollow beam and sub-stiffness matrix of cantilever bars is the main reason for the segmentation of modal natural frequencies and the coupling stiffness between hollow beam and cantilever bars is the main reason for the concentration of modal natural frequencies and the formation of the regular mode shapes for cantilever bars group.

Identification of mechanical and damage parameters of composite laminates based on a CPAM method

2018 ◽  
Vol 37 (17) ◽  
pp. 1114-1128 ◽  
Author(s):  
Farshid Masoumi ◽  
Ahmad Ghasemi-Ghalebahman ◽  
Mohammad-Javad Kokabi
Keyword(s):  
Mechanical Properties ◽  
Numerical Solution ◽  
Composite Laminates ◽  
Natural Frequencies ◽  
Error Function ◽  
Numerical Data ◽  
Optimization Procedure ◽  
Composite Plates ◽  
Mode Shapes ◽  
Layer Width

A new method combining experimental and numerical data is proposed to simultaneously determine the mechanical properties and damage parameters in multilayered composite plates. Studied parameters are mechanical properties of each layer, width and length of delamination zone, location of damage’s center, and interface location of the damage. In this method, the PSO optimization procedure based on a CPAM algorithm uses vibration test data along with their corresponding numerical solution. Vibration data are the plates’ natural frequencies and mode shapes obtained in the modal laboratory. In order to efficiently investigate the studied parameters, the numerical solution is investigated by a commercial finite element package. The error function constitutes two parts, one part is included by the sum of the squared differences between experimental and numerical natural frequencies and the other is based on the mode shapes data. The mode shapes’ curvatures are also utilized to achieve high sensitivity to small faults. Moreover, by applying a Gaussian disorder model to the vibrational data, the sensitivity of the method is evaluated in the presence of unwanted noises. The results confirm the robustness of the proposed study for identifying both mechanical constants and damage parameters in composite plates.

Follower Effect of Internal Pressure on Modal Analysis of a Space Inflatable Structure

2015 ◽  
Vol 727-728 ◽  
pp. 578-582
Author(s):  
Fei Liu ◽  
Wei Liang He
Keyword(s):  
Finite Element ◽  
Modal Analysis ◽  
Natural Frequencies ◽  
Element Model ◽  
Mode Shapes ◽  
Fem Model ◽  
Configuration Change ◽  
Modal Behavior ◽  
Good Agreement ◽  
Inflatable Structure

The stress distribution and modal behavior of a space inflatable torus was investigated by nonlinear finite element numerical method. This paper focused on the effect of follower pressure on the modal analysis of the torus, including the effect of configuration change and follower pressure stiffness, and focused on validating the follower pressure stiffness FEM model and its applicability to modal analysis. Research shows that the changed configuration slightly increases the natural frequencies. The follower pressure stiffness significantly reduces the natural frequencies and changes mode shapes order. The modal results are in good agreement with the corresponding shell theory solutions, indicating that the finite element model of the follower pressure stiffness for the inflatable structure modal analysis in this paper is accurate enough and reasonable.

scholarly journals Experimental Measurements of the Natural Frequencies and Mode Shapes of Rotating Disk-Blades-Disk Assemblies from the Stationary Frame

2019 ◽  
Vol 9 (18) ◽  
pp. 3864
Author(s):  
Alexandre Presas ◽  
David Valentin ◽  
Carme Valero ◽  
Monica Egusquiza ◽  
Eduard Egusquiza
Keyword(s):  
Reference Frames ◽  
Natural Frequencies ◽  
Laser Doppler Vibrometer ◽  
Rotating Disk ◽  
Normal Operation ◽  
Mode Shapes ◽  
Experimental Measurements ◽  
Rotating Frame ◽  
Rotating Speed ◽  
Stationary Frame

Determining the natural frequencies and mode shapes of rotating turbomachinery components from both rotating and stationary reference frames is of paramount importance to avoid resonance problems that could affect the normal operation of the machine, or even cause critical damages in these components. Due to their similarity to real engineering cases, this topic has been experimentally analyzed in the past for disk-shaft assemblies and rotor disk-blades assemblies (bladed-disk or blisk). The same topic is less analyzed for disk-blades-disk assemblies, although such configurations are widely used in centrifugal closed impellers of compressors, hydraulic pumps, pump-turbines, and runners of high head Francis turbines. In this paper, experimental measurements, varying the rotating speed of a disk-blade-disk assembly and exciting the first natural frequencies of the rotating frame, have been performed. The rotating structure is excited and measured by means of PZT patches from the rotating frame and with a Laser Doppler Vibrometer (LDV). In order to interpret the experimental results obtained from the stationary frame, a method to decompose the diametrical mode shapes of the structure in simple diametrical components (which define the diametrical mode shapes of a simple disk) has been proposed. It is concluded that the resonant frequencies detected with a stationary sensor correspond to the ones predicted with the decomposition method. Finally, a means to obtain equivalent results with numerical simulation methods is shown.

Microendmill Dynamics Including the Actual Fluted Geometry and Setup Errors—Part II: Model Validation and Application

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Sinan Filiz ◽  
O. Burak Ozdoganlar
Keyword(s):  
Finite Element ◽  
Natural Frequencies ◽  
Laser Doppler Vibrometer ◽  
Mode Shapes ◽  
Fe Model ◽  
Dynamics Model ◽  
Free Boundary Conditions ◽  
Dynamic Excitation ◽  
Piezoelectric Elements ◽  
Modal Behavior

This paper presents a study to validate the microendmill dynamics model derived in Part I. A laser Doppler vibrometer system that is coupled with a microscope is used to measure the natural frequencies and mode shapes of nonrotating microendmills with different geometries. Free-free boundary conditions are obtained by suspending the microendmills using elastic bands. The dynamic excitation is delivered through miniature piezoelectric elements attached to the microendmill shanks. In each case, the model is compared to experimental results and solid-element finite-element (FE) models. To evaluate the model in the presence of rotational effects, the model is compared to an FE model. In most cases, the model was seen to capture the dynamic behavior of microendmills accurately. The validated model is used to investigate the effects of microendmill geometry, and radial and tilt runouts on the modal behavior of microendmills. Furthermore, possible geometric simplifications to fluted region are evaluated based on the accuracy of the predicted natural frequencies of the microendmills.

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