Dynamics of a Power Collector With Friction Dampers

1976 ◽  
Vol 98 (1) ◽  
pp. 306-311 ◽  
Author(s):  
K. Yoshida ◽  
T. Shimogo
Keyword(s):  
Contact Force ◽  
Coulomb Friction ◽  
High Speed ◽  
Equivalent Linearization ◽  
Friction Damper ◽  
Friction Forces ◽  
Friction Dampers ◽  
Force Variation ◽  
Optimal Values ◽  
The Mean

Using the friction damper, the construction of power collector for a very high-speed railway will be considerably simplified. In this paper, the power collector with friction dampers is considered, and its dynamic characteristics are analyzed by the equivalent linearization technique. The main purpose of this paper is to investigate the effects of Coulomb friction forces on the mean squared value of contact force variation between a contactor and a rigid collecting rail with a randomly wavy surface. A numerical example is presented, and the optimal values of Coulomb friction forces which minimize the probability that the contact force becomes negative are found as a result.

Computer Evaluation of Controlled Pantographs for Current Collection From Simple Catenary Overhead Equipment at High Speed

1983 ◽  
Vol 105 (4) ◽  
pp. 287-294 ◽  
Author(s):  
T. Vinayagalingam
Keyword(s):  
Contact Force ◽  
High Speed ◽  
Overhead Line ◽  
Combined System ◽  
Current Collection ◽  
Constant Height ◽  
Force Profile ◽  
Force Variation ◽  
Computer Simulation Technique

A digital computer simulation technique is used to study the effects of changing pantograph characteristics upon the quality of current collection from simple catenary overhead equipment at high speed. In particular, the likely benefits to be derived by the use of controlled pantographs are assessed. Pantograph performance is judged on the basis of contact force variation and displacement responses of pantograph and contact wire. These studies have shown that the dynamic displacements of the combined system are determined primarily by the overhead line parameters rather than by the pantograph. At higher speeds droppers in the vicinity of the pantograph slacken and this is seen to influence significantly the contact force profile. On a “constant height” overhead line, the proposed “frame compensated” and “panhead inertia compensated” pantographs do not show any marked improvement in the quality of current collection.

Active Control of a High-Speed Pantograph

1997 ◽  
Vol 119 (1) ◽  
pp. 1-4 ◽  
Author(s):  
D. N. O’Connor ◽  
S. D. Eppinger ◽  
W. P. Seering ◽  
D. N. Wormley
Keyword(s):  
Dynamic Model ◽  
Active Control ◽  
Contact Force ◽  
High Speed ◽  
High Speed Train ◽  
Single Measurement ◽  
Force Variation ◽  
Catenary System ◽  
And Performance ◽  
And Control

The design and performance of an active controller for a pantograph which collects current for a high-speed train are considered. A dynamic model of the pantograph/catenary system is described and control objectives are established. A design which incorporates a frame-actuated controller and requires only a single measurement is described. Over an array of train speeds, the contact force variation with the actively controlled pantograph is 50 percent less than for the equivalent passive pantograph system.

Dynamics of a High-Speed Sliding Power Collector in Consideration of Sliding Friction

1978 ◽  
Vol 100 (2) ◽  
pp. 242-250
Author(s):  
K. Yoshida ◽  
T. Shimogo
Keyword(s):  
High Speed ◽  
Sliding Friction ◽  
Contact Stiffness ◽  
Equivalent Linearization ◽  
High Speed Railway ◽  
Sliding Direction ◽  
Contact Points ◽  
Force Variation ◽  
Digital Simulations ◽  
Very High

Considering the sliding friction force produced between a contactor and a rigid collecting rail with a randomly wavy surface, the paper deals with the dynamics of a sliding power collector for a very-high-speed railway. An analytical model is formulated, which has two contact points and takes into account the pitching of a contactor, the stiffness of the sliding direction in a contactor support system, and the nonlinearity of the contact stiffness between a contactor and a rail. Mainly, the influences of the sliding friction and the contact stiffness on the dynamic characteristics, i.e., the contact force variation, the probability of contact break, etc., are investigated. The equivalent linearization technique is applied in the analysis. To verify the analytical results, digital simulations are carried out by preparing the artificial collecting rail wave.

An Integrated Approach for Friction Damper Design

1990 ◽  
Vol 112 (2) ◽  
pp. 175-182 ◽  
Author(s):  
T. M. Cameron ◽  
J. H. Griffin ◽  
R. E. Kielb ◽  
T. M. Hoosac
Keyword(s):  
Optimal Design ◽  
High Speed ◽  
Design Procedure ◽  
Single Mode ◽  
Design Parameters ◽  
Bench Test ◽  
Friction Damper ◽  
Friction Dampers ◽  
Damper Design ◽  
Blade Model

A procedure is outlined for determining the optimal design of friction dampers for high-speed turbomachinery blading. The procedure includes: An integration of bench test results with finite-element analysis and a single-mode blade model to ensure accuracy of the analytical model and improve reliability of the friction damper design; an extension of the single-mode blade model to predict the engine behavior of friction dampers; and a new way of viewing analytical and experimental results in terms of a damper performance curve to determine optimal design parameters, when the levels of excitation and damping in the system are unknown. Unique experiments are performed on a test disk in order to demonstrate and verify the accuracy of the design procedure.

Friction Damper for Fatigue Damage Mitigation in Steel Jacket Platforms

2008 ◽  
Author(s):  
A. A. Golafshani ◽  
A. Gholizad
Keyword(s):  
Nonlinear Behavior ◽  
Ocean Waves ◽  
Realistic Model ◽  
Offshore Platforms ◽  
Friction Damper ◽  
Friction Dampers ◽  
Optimal Values ◽  
Hysteretic Dampers ◽  
Wave Induced ◽  
Random Nature

The performance of friction dampers to mitigate the wave induced vibrations in jacket type offshore platforms has been investigated in this study. Due to the random nature of ocean waves, a full stochastic analysis method has been intended to evaluate the response of the structures utilized with these devices and also a stochastic linearization technique has been used to take the nonlinear behavior of these hysteretic dampers into account. At last, the developed mathematic formulation has been practiced to evaluate the response of a realistic model and to find out the optimal values for the adjustive parameters of the friction dampers to dissipate the wave induced vibrations of the platform.

Effect of Design Changes in Railway Catenary-Pantograph Systems on Power Collection at High Speed

1968 ◽  
Vol 90 (4) ◽  
pp. 680-689
Author(s):  
R. T. Gray ◽  
S. Levy ◽  
J. A. Bain ◽  
E. J. Leclerc
Keyword(s):  
Contact Force ◽  
High Speed ◽  
Operating Conditions ◽  
Department Of Transportation ◽  
High Speeds ◽  
Design Changes ◽  
Force Variation ◽  
Suitable System ◽  
The U.S

Using a GE-635 computer program developed for the U.S. Department of Transportation, a study has been made of the effect of changes in the catenary-pantograph system on the quality of power collection at high speeds. The study explored the effect of: (a) Sag between towers, (b) pantograph spacing, (c) stiffness of the tower support, (d) damping and stiffness of the pantograph, (e) stiffness of the contact spring, (f) dropper stiffness, (g) dropper spacing. It was found that all of these have a significant effect on the constancy of the contact force between catenary and pantograph. By proper choice of system constants, the contact force variation can be substantially reduced. A basis is provided for selecting suitable system constants for a given range of operating conditions.

The Dynamics of High-Speed Sliding Power Collection Systems for Electrically Propelled Vehicles

1974 ◽  
Vol 96 (2) ◽  
pp. 158-162
Author(s):  
J. A. Bain
Keyword(s):  
Surface Roughness ◽  
Contact Force ◽  
High Speed ◽  
Reference Case ◽  
The Third ◽  
Measured Sample ◽  
Force Variation ◽  
Random Irregularity

A method is presented for estimating the contact force variation between a collector brush and a rigid third rail when the third rail has a surface with random irregularity. Results are obtained for a reference case where the third rail roughness is estimated from the roughness of other known surfaces. The surface roughness of an actual commercial third rail is measured and the results are used to estimate the performance of a collector on the measured sample at 300 mph. Conclusions are drawn about the feasibility of power collection at 300 mph.

Articulatory Behavior Pre and Post Full-Mouth Tooth Extraction and Alveoloplasty

1980 ◽  
Vol 23 (3) ◽  
pp. 630-645 ◽  
Author(s):  
Gerald Zimmermann ◽  
J.A. Scott Kelso ◽  
Larry Lander
Keyword(s):  
Control Subject ◽  
High Speed ◽  
Tooth Extraction ◽  
Kinematic Parameters ◽  
Experimental Conditions ◽  
Mean Values ◽  
Articulatory Movements ◽  
The Mean ◽  
Experimental Subjects ◽  
Normal Speech

High speed cinefluorography was used to track articulatory movements preceding and following full-mouth tooth extraction and alveoloplasty in two subjects. Films also were made of a control subject on two separate days. The purpose of the study was to determine the effects of dramatically altering the structural dimensions of the oral cavity on the kinematic parameters of speech. The results showed that the experimental subjects performed differently pre and postoperatively though the changes were in different directions for the two subjects. Differences in both means and variabilities of kinematic parameters were larger between days for the experimental (operated) subjects than for the control subject. The results for the Control subject also showed significant differences in the mean values of kinematic variables between days though these day-to-day differences could not account for the effects found pre- and postoperatively. The results of the kinematic analysis, particularly the finding that transition time was most stable over the experimental conditions for the operated subjects, are used to speculate about the coordination of normal speech.

scholarly journals The influence of solar wind on extratropical cyclones – Part 1: Wilcox effect revisited

2009 ◽  
Vol 27 (1) ◽  
pp. 1-30 ◽  
Author(s):  
P. Prikryl ◽  
V. Rušin ◽  
M. Rybanský
Keyword(s):  
Time Series ◽  
Solar Wind ◽  
Northern Hemisphere ◽  
High Speed ◽  
Coronal Holes ◽  
Extratropical Cyclones ◽  
Sector Boundary ◽  
Speed Solar Wind ◽  
The Mean ◽  
High Speed Solar Wind

Abstract. A sun-weather correlation, namely the link between solar magnetic sector boundary passage (SBP) by the Earth and upper-level tropospheric vorticity area index (VAI), that was found by Wilcox et al. (1974) and shown to be statistically significant by Hines and Halevy (1977) is revisited. A minimum in the VAI one day after SBP followed by an increase a few days later was observed. Using the ECMWF ERA-40 re-analysis dataset for the original period from 1963 to 1973 and extending it to 2002, we have verified what has become known as the "Wilcox effect" for the Northern as well as the Southern Hemisphere winters. The effect persists through years of high and low volcanic aerosol loading except for the Northern Hemisphere at 500 mb, when the VAI minimum is weak during the low aerosol years after 1973, particularly for sector boundaries associated with south-to-north reversals of the interplanetary magnetic field (IMF) BZ component. The "disappearance" of the Wilcox effect was found previously by Tinsley et al. (1994) who suggested that enhanced stratospheric volcanic aerosols and changes in air-earth current density are necessary conditions for the effect. The present results indicate that the Wilcox effect does not require high aerosol loading to be detected. The results are corroborated by a correlation with coronal holes where the fast solar wind originates. Ground-based measurements of the green coronal emission line (Fe XIV, 530.3 nm) are used in the superposed epoch analysis keyed by the times of sector boundary passage to show a one-to-one correspondence between the mean VAI variations and coronal holes. The VAI is modulated by high-speed solar wind streams with a delay of 1–2 days. The Fourier spectra of VAI time series show peaks at periods similar to those found in the solar corona and solar wind time series. In the modulation of VAI by solar wind the IMF BZ seems to control the phase of the Wilcox effect and the depth of the VAI minimum. The mean VAI response to SBP associated with the north-to-south reversal of BZ is leading by up to 2 days the mean VAI response to SBP associated with the south-to-north reversal of BZ. For the latter, less geoeffective events, the VAI minimum deepens (with the above exception of the Northern Hemisphere low-aerosol 500-mb VAI) and the VAI maximum is delayed. The phase shift between the mean VAI responses obtained for these two subsets of SBP events may explain the reduced amplitude of the overall Wilcox effect. In a companion paper, Prikryl et al. (2009) propose a new mechanism to explain the Wilcox effect, namely that solar-wind-generated auroral atmospheric gravity waves (AGWs) influence the growth of extratropical cyclones. It is also observed that severe extratropical storms, explosive cyclogenesis and significant sea level pressure deepenings of extratropical storms tend to occur within a few days of the arrival of high-speed solar wind. These observations are discussed in the context of the proposed AGW mechanism as well as the previously suggested atmospheric electrical current (AEC) model (Tinsley et al., 1994), which requires the presence of stratospheric aerosols for a significant (Wilcox) effect.

scholarly journals Modeling the Excess Velocity of Low-Viscous Taylor Droplets in Square Microchannels

Fluids ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 162 ◽  
Author(s):  
Thorben Helmers ◽  
Philip Kemper ◽  
Jorg Thöming ◽  
Ulrich Mießner
Keyword(s):  
High Speed ◽  
Process Intensification ◽  
Continuous Phase ◽  
Channel Cross Section ◽  
Optimization Approach ◽  
Mean Flow ◽  
Bypass Flow ◽  
Wall Film ◽  
Proposed Model ◽  
The Mean

Microscopic multiphase flows have gained broad interest due to their capability to transfer processes into new operational windows and achieving significant process intensification. However, the hydrodynamic behavior of Taylor droplets is not yet entirely understood. In this work, we introduce a model to determine the excess velocity of Taylor droplets in square microchannels. This velocity difference between the droplet and the total superficial velocity of the flow has a direct influence on the droplet residence time and is linked to the pressure drop. Since the droplet does not occupy the entire channel cross-section, it enables the continuous phase to bypass the droplet through the corners. A consideration of the continuity equation generally relates the excess velocity to the mean flow velocity. We base the quantification of the bypass flow on a correlation for the droplet cap deformation from its static shape. The cap deformation reveals the forces of the flowing liquids exerted onto the interface and allows estimating the local driving pressure gradient for the bypass flow. The characterizing parameters are identified as the bypass length, the wall film thickness, the viscosity ratio between both phases and the C a number. The proposed model is adapted with a stochastic, metaheuristic optimization approach based on genetic algorithms. In addition, our model was successfully verified with high-speed camera measurements and published empirical data.

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