Mechanical foam breaking - a physical model for impact effects with high speed rotors

1997 ◽  
Vol 20 (2) ◽  
pp. 76-84 ◽  
Author(s):  
Stefan Gutwald ◽  
Alfons Mersmann
Keyword(s):  
Physical Model ◽  
High Speed ◽  
Mechanical Foam

A Solid-State On-Load Tap Changer for the Power Transformers of 10—0.4 kV Distribution Networks

Vestnik MEI ◽  
2020 ◽  
Vol 6 (6) ◽  
pp. 82-90
Author(s):  
Dmitriy I. Panfilov ◽  
◽  
Mikhail G. Astashev ◽  
Aleksandr V. Gorchakov ◽  
◽  
...  
Keyword(s):  
Solid State ◽  
Physical Model ◽  
High Speed ◽  
Power Transformer ◽  
Voltage Control ◽  
Power Transformers ◽  
Control Algorithms ◽  
Load Voltage ◽  
Tap Changer ◽  
Load Tap Changer

The specific features relating to voltage control of power transformers at distribution network transformer substations are considered. An approach to implementing high-speed on-load voltage control of serially produced 10/0.4 kV power transformers by using a solid-state on-load tap changer (SOLTC) is presented. An example of the SOLTC circuit solution on the basis of thyristor switches is given. On-load voltage control algorithms for power transformers equipped with SOLTC that ensure high reliability and high-speed operation are proposed. The SOLTC performance and the operability of the suggested voltage control algorithms were studied by simulation in the Matlab/Simulink environment and by experiments on the SOLTC physical model. The structure and peculiarities of the used simulation Matlab model are described. The SOLTC physical model design and its parameters are presented. The results obtained from the simulating the SOLTC operation on the Matlab model and from the experiments on the SOLTS physical model jointly with a power transformer under different loads and with using different control algorithms are given. An analysis of the experimental study results has shown the soundness of the adopted technical solutions. It has been demonstrated that the use of an SOLTC ensures high-speed voltage control, high efficiency and reliability of its operation, and arcless switching of the power transformer regulating taps without load voltage and current interruption. By using the SOLTC operation algorithms it is possible to perform individual phase voltage regulation in a three-phase 0.4 kV distribution network. The possibility of integrating SOLTC control and diagnostic facilities into the structure of modern digital substations based on the digital interface according to the IEC 61850 standard is noted.

Dynamic Response of the Vertical Rotor System to Base Excitation

2008 ◽  
Author(s):  
Jianli Zuo ◽  
Jianjun Wu ◽  
Ping Li ◽  
Shenjian Su
Keyword(s):  
Dynamic Response ◽  
Physical Model ◽  
High Speed ◽  
Lagrange Equation ◽  
Rotor System ◽  
Operating Speed ◽  
Base Excitation ◽  
Rotating Machine ◽  
Vertical Rotor ◽  
Rotary Speed

The physical model of a high-speed vertical rotating machine was taken as the example. The motion differential equations of the rotor system were established by the Lagrange equation and numerically solved by the Wilson-θ method. The whirling characteristics of the rotor excited by the base’s harmonic motions have been analyzed. The whirling directions are different between the rotor’s upper and lower ends. And the whirling characteristics of the rotor vary with the frequency of the base’s motion. Besides, there exists such a region of the rotor’s rotary speed, in which the whirling characteristics and amplitudes of the rotor system are relatively steady, so the aseismic tests at a certain lower speed can be done to examine the aseismic capability of the rotor system at operating speed.

Pantograph-Catenary Model Simulation Based on DSPACE

2012 ◽  
Vol 256-259 ◽  
pp. 2967-2970
Author(s):  
Shuai Lin ◽  
Zhi Qiang Ju
Keyword(s):  
Real Time ◽  
Physical Model ◽  
High Speed ◽  
Model Simulation ◽  
The State ◽  
Rail Transit ◽  
High Speed Rail ◽  
Simulation Based ◽  
Primary Means ◽  
The City

With the city subway and high speed rail opened, development of rail transit pays more and more people's attention. And the pantograph is the primary means of train running at high speed to get power. Using Simulink and dSPACE in combination, real-time captures the pantograph and catenary's motion. According to the state of the pantograph’s motion, analyses physical model, so as to achieve the purpose of independent manufacturing pantograph pantograph.

Opercular jetting during fast-starts by flatfishes

1997 ◽  
Vol 200 (8) ◽  
pp. 1179-1188
Author(s):  
E Brainerd ◽  
B Page ◽  
F Fish
Keyword(s):  
Physical Model ◽  
High Speed ◽  
Adhesion Force ◽  
The Body ◽  
Total Force ◽  
Ocean Bottom ◽  
Blind Side ◽  
Pseudopleuronectes Americanus ◽  
Fast Start ◽  
Coherent Jet

When attacked by predators, flatfishes perform fast-starts that result in a rapid take-off from the ocean bottom on which they lie. High-speed video recordings of the blind side of flatfishes indicate that they expel a coherent jet of water from the blind-side opercular valve during take-off. Buccal pressure recordings in winter flounder (Pseudopleuronectes americanus) show that a buccal pressure pulse begins 0­20 ms before the beginning of the fast-start and has a range of mean magnitudes for three individuals of 1.6­10.7 kPa. We hypothesize that one function of the opercular jet in flatfishes may be to reduce the effects of Stefan adhesion. Stefan adhesion occurs as the fish lifts its head up rapidly from the ocean bottom, when water must flow into the space forming beneath the fish. Water viscosity opposes this rapid shear, and a suction pressure develops under the fish, making it more difficult for the fish to escape from the bottom. To estimate the magnitude of Stefan adhesion, we simulated fast-starts using a physical model in which a dead flounder was pulled upwards with an acceleration of 95 m s-2. Results from the physical model indicate that up to 35 % of the total force required to lift the head at 20 ms into the start can be attributed to Stefan adhesion. Despite this large adhesion force, previous work has shown that live flatfish do not show improved fast-start performance when Stefan adhesion has been eliminated by starting the fish from an open wire grid. Thus, live fishes are likely to be using behavioral mechanisms to reduce the adhesion force. Both the timing and location along the body of the opercular jet indicate that it is ideally suited to attenuate the effects of Stefan adhesion. Propping the body up on the median fins may also reduce adhesion by increasing the initial distance between the fish and the ocean floor.

Stator Whirl With Rotors in Bearing Clearance

1967 ◽  
Vol 89 (3) ◽  
pp. 381-389 ◽  
Author(s):  
F. F. Ehrich ◽  
J. J. O’Connor
Keyword(s):  
Physical Model ◽  
High Speed ◽  
Degrees Of Freedom ◽  
Contact Point ◽  
Analog Computer ◽  
Vibration Response ◽  
Stable Operation ◽  
Bearing Clearance ◽  
Bearing Contact ◽  
Acceleration And Deceleration

In order to identify and assess the effects of stator dynamics on vibration of high speed rotating machinery, a physical model with two degrees of freedom (one for the rotor and one for the stator) has been defined. Assuming that vibratory motion, as excited by rotor unbalance, is synchronous and axisymmetric, the analysis is linear and straightforward. The calculated vibration response reveals and quantifies some new and important phenomena which are a function of the level of bearing clearance (as related to unbalance level) and of the relative values of the rotor and stator natural frequencies. In particular, the following phenomena are noted: 1. As in simpler models, bearing clearance results in a reduction in system critical speed and can result in a “rightward leaning” critical peak causing hysteresis in response on acceleration and deceleration. 2. In certain ranges of parameters, two vibration modes are possible at high supercritical rotational speeds. One, termed stator whirl, results in stator amplitudes proportional to bearing clearance which are much larger than would be expected with very tight or very loose bearings. 3. Amplitude jump phenomena are very often experienced at a rotational speed equal to stator natural frequency. 4. Hysteresis phenomena, opposite in direction to that associated with a right-leaning critical peak, can be experienced on the subcritical side of the critical peak. 5. Disconnected from the main vibration response curve, branches of stable operation are evident and are hypothesized to be realizable if the system is subjected to momentary disturbances. The results have been verified by an analog computer simulation of the same system, and the effects of component damping and friction at the bearing contact point have been evaluated. Some regimes of asynchronous nonaxisymmetric motion in the analog computer model have been sensed, even though the physical model is axisymmetric.

The Finite Element Analysis of the Floor Damper of High Speed Train

2015 ◽  
Vol 740 ◽  
pp. 142-145
Author(s):  
Dong Zhe Wang ◽  
Jian Min Ge ◽  
Xian Kui Zeng ◽  
Zong Ting Zhang ◽  
Chong Lv
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Physical Model ◽  
Correction Factor ◽  
High Speed ◽  
Vertical Deformation ◽  
High Speed Train ◽  
Element Analysis ◽  
Model Experiments ◽  
The Finite Element Analysis

In this paper, based on the honeycomb floor damper of high-speed train, the finite element analysis was carried out on the floor damper, and we compared the experimental results with the physical model experiments. The results show that: when correction factor γ = 0.5, there is the minimum incremental error of vertical deformation, and the value of the damper parameters is the best at this time.

Patterns of Fracture Initiation in Metallic Materials with a Heterogeneous Structure under Dynamic Cyclic Loading

2020 ◽  
Vol 989 ◽  
pp. 127-132
Author(s):  
Oleg V. Kudryakov ◽  
Valery N. Varavka ◽  
Igor S. Morozkin
Keyword(s):  
Cyclic Loading ◽  
Physical Model ◽  
High Speed ◽  
Erosive Wear ◽  
Fracture Initiation ◽  
Heterogeneous Structure ◽  
Structural Morphology ◽  
Nucleation Stage ◽  
The Moment ◽  
Instrumental Methods

The process of nucleation of fatigue defects in metal alloys with different structural morphology is considered. A physical model was built, calculation expressions were presented, a numerical experiment was performed to determine the moment of nucleation of the critical-size defect in Fe-based alloys during high-speed droplet impacts. The physical model is based on the theory of dislocations. It is shown that the determining factor in the process of wear nucleation under dynamic cyclic loading has a structural factor. Depending on the structure and properties of the material, as well as on the nature of the loads, the critical fatigue defect develops in the form of cracks, pores or microcraters. Comparative data of calculations and bench tests for droplet impingement erosion were presented. The contribution of the nucleation stage during the incubation period of erosive wear of the materials studied was evaluated. Due to the fact that rigorous instrumental methods for determining the duration of the nucleation stage are absent, the usage of the proposed analytical model is recommended for this purpose.

scholarly journals Optimisation of Temperature Fields of Microsystems with Self-Organising Neural Nets

2003 ◽  
Vol 26 (3) ◽  
pp. 141-149
Author(s):  
P. Bratek ◽  
A. Kos
Keyword(s):  
Physical Model ◽  
Heuristic Algorithm ◽  
High Speed ◽  
Vlsi Circuits ◽  
Neural Nets ◽  
Temperature Fields ◽  
Neural Net ◽  
Thermal Phenomena ◽  
System Designs ◽  
Statistical Results

Thermal modelling and optimisation of parameter distributed systems is a rather time-consuming process. In this paper the problem of optimisation of temperature fields of VLSI circuits and systems is attacked by a selforganising neural net. The net directly solves the task generated by a heuristic algorithm. No physical model of thermal phenomena is used. The proposed method is simple. Some examples and statistical results are presented. The proposed method is addressed mostly to large, high-speed system designs.

Sign in / Sign up

Export Citation Format

Share Document