scholarly journals Applications of Permanent Maglev Bearing in Heart Pumps and Turbine Machine

2011 ◽  
Vol 2011 ◽  
pp. 1-4 ◽  
Author(s):  
Kun-Xi Qian ◽  
Teng Jing ◽  
Hao Wang
Keyword(s):  
Stable Equilibrium ◽  
Dynamic Equilibrium ◽  
Critical Value ◽  
Magnetic Bearing ◽  
Static State ◽  
Rotating Speed ◽  
Moving Body ◽  
Radial Pump ◽  
Earnshaw's Theorem ◽  
Fast Rotating

Earnshaw's theorem (1839) stated that no stationary object made of magnets in a fixed configuration can be held in stable equilibrium by any combination of static magnetic or gravitational forces. What will happen by a moving body like a rotating passive magnetic levitator? Nobody has given an answer until now. The author applied a self-made passive magnetic bearing to radial pump and turbine machine and found that if the rotating speed could be higher than a critical value, 3250 rpm for a pump and 1800 rpm for a turbine, the rotors would be disaffiliated from stators and keep the rotation stable. It seems that the fast rotating levitator has a so-called “Gyroeffect” which makes the passive maglev rotator stable. These results have extended Earnshaw's theorem from static to dynamic equilibrium. In static state or by a speed lower than critical value, the passive maglev rotator cannot keep rotation stable; if the rotating speed is higher than critical speed, the passive magnetic levitator will have Gyroeffect and thereby stabilize its rotation.

Route Chart to Stabilizing Permanent Maglev Rotator

2013 ◽  
Vol 785-786 ◽  
pp. 1586-1589
Author(s):  
Kun Xi Qian ◽  
Teng Jing
Keyword(s):  
Stable Equilibrium ◽  
Magnetic Bearing ◽  
Dynamic State ◽  
Static State ◽  
Rotating Speed ◽  
Bearing Force

Permanent maglev has been since long recognized to be unstable because of Earnshaw's theory, which theoretically proved that permanent maglev can not achieve stable equilibrium in static state. How about that in dynamic state, for example, about a rotator, nobody has given an answer until now actually. A permanent maglev pump and a permanent maglev turbine have been developed, by using a patented permanent magnetic bearing developed by the author. Experiments demonstrated, there is a critic speed either in the pump or in the turbine, under which the rotors in the pump and the turbine have a maximal eccentricity being possible to reach the gap between the rotor and the stator. That means the rotors have contact with the stators occasionally, and thus the rotor is not suspended. In case the rotating speed is higher than this critic speed, the rotors' eccentricity will be remarkably smaller than the gap between the rotor and the stator, that is to say the rotor is stably levitated. Further investigation exhibtes that at the critic speed a so-called gyro-effect is generated which stabilizes the rotor, just like a gyro standing over a ball, if the rotating speed is large enough it can be stable over the ball. The critic speed, essentially to be minimal stable speed of the rotor, depends on the rotating inertia of the rotor and the bearing force, the larger the inertia and the larger the force, the lower the critic speed. Conclusively, a route chart to stabilization of permanent maglev rotator has been clear: in static state, permanent maglev is unstable (Earnshaw's theory); as the rotating speed gradually increases but not up to a critic speed, the permanent maglev rotator is also unstable; in case that the speed equals or is larger than this critic speed, the permanent maglev rotator is suspended stably because of gyro-effect; the critic speed is affected by rotating inertia of the rotor and the bearing force, by larger inertia and larger bearing force, the critic speed will be smaller.

Comparison of three-pole AMB and HMB for magnetic suspended molecular pump

2018 ◽  
Vol 32 (34n36) ◽  
pp. 1840074
Author(s):  
Jintao Ju ◽  
Xiaobin Liu ◽  
Zegang Xu ◽  
Chao Gu ◽  
Yilin Liu
Keyword(s):  
Power Loss ◽  
High Vacuum ◽  
Three Dimensional ◽  
Radial Force ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Active Magnetic Bearing ◽  
Rotating Speed ◽  
Characteristics Analysis ◽  
Current Characteristics

Molecular pumps have been widely used in the vacuum metallurgy, coating, semiconductor manufacturing and many other fields in which the high vacuum, ultra-clean environment is needed. The application of magnetic bearings can bring many advantages for molecular pump, such as eliminating the friction, decreasing the power loss, lowering the maintenance costs, and increasing the rotating speed and service life. Besides, the magnetic bearings can fundamentally solve the vacuum chamber pollution problem which is caused by the backflow of lubrication oil steam. The three-pole magnetic bearings are the simplest structure of radial magnetic bearings and can be driven by three-phase converter which has the advantages of low costs, small volume and low power loss. In this paper, the performance of the three-pole active magnetic bearing (AMB) and hybrid magnetic bearing (HMB) are compared based on radial force–current characteristics analysis. Firstly, the mathematical model of three-pole AMB and HMB is built by equivalent magnetic circuit model, and the radial force–current characteristics are analyzed. Then, simulation by the three-dimensional (3D) finite element method (FEM) is performed. Finally, the experiment is conducted. The FEM results are consistent with the analytical results, showing that the nonlinearity and coupling of three-pole HMB are lower than three-pole AMB. The reason of causing nonlinearity and coupling is also discussed.

Experimental Measurement of a Three Lobe Air Bearing Rotordynamic Coefficients

2006 ◽  
Author(s):  
Rafael O. Ruiz ◽  
Marcelo H. Di Liscia ◽  
Sergio Di´az ◽  
Luis Medina
Keyword(s):  
Reynolds Equation ◽  
Ideal Gas ◽  
Magnetic Bearing ◽  
Experimental Results ◽  
Rotating Speed ◽  
Rotordynamic Coefficients ◽  
Fluid Film Bearings ◽  
Bearing Force ◽  
Air Film ◽  
Gas Journal Bearing

This work presents direct experimental measurements of air film rotordynamic coefficients on a three lobe bearing. The test rig uses two magnetic bearing actuators to impose desired test orbits to the journal. Tests are conducted at several rotating speeds up to 12,000rpm. Journal whirling excitation is independent of the rotating speed, thus allowing asynchronous excitations. One-dimensional orbits in the horizontal and vertical axes are applied as excitations at each rotating speed. The experimental results show the behavior of the rotordynamic coefficients of the air film bearing under synchronous and asynchronous excitation. The synchronous experimental results are compared to numerical estimation of the bearing force coefficients through solution of the isotropic ideal gas journal bearing Reynolds equation coupled with the pressure drop through the feeding holes. The results of this work prove the suitability of the rig to identify both the synchronous and nonsynchronous response of air fluid film bearings.

Controlling Journal Bearing Instability Using Active Magnetic Bearings

2007 ◽  
Author(s):  
A. El-Shafei ◽  
A. S. Dimitri
Keyword(s):  
Journal Bearing ◽  
Magnetic Bearing ◽  
Journal Bearings ◽  
Active Magnetic Bearing ◽  
Rotating Speed ◽  
Damping Characteristics ◽  
Oil Whip ◽  
Novel Approach ◽  
Oil Whirl ◽  
Load Carrying

Journal Bearings are excellent bearings due to their large load carrying capacity and favorable damping characteristics. However, Journal bearings are known to be prone to instabilities. The oil whirl and oil whip instabilities limit the rotor maximum rotating speed. In this paper, a novel approach is used to control the Journal bearing (JB) instability. An Active Magnetic Bearing (AMB) is used to overcome the JB instability and to increase its range of operation. The concept is quite simple: rather than using the AMB as a load carrying element, the AMB is used as a controller only, resulting in a much smaller and more efficient AMB. The load carrying is done by the Journal bearings, exploiting their excellent load carrying capabilities, and the JB instability is overcome with the AMB. This results in a combined AMB/JB that exploits the advantages of each device, and eliminates the deficiencies of each bearing. Different controllers for the AMB to control the JB instability are examined and compared theoretically and numerically. The possibility of collocating the JB and the AMB is also examined. The results illustrate the effectiveness of the concept.

Study on a Dynamical Model of Plankton in Lake Environment

2013 ◽  
Vol 830 ◽  
pp. 384-387
Author(s):  
Xi Yun Wang ◽  
Shu Yan Cao ◽  
Dong Guo Li
Keyword(s):  
Periodic Solution ◽  
Qualitative Analysis ◽  
Numerical Simulations ◽  
Boundary Point ◽  
Stable Equilibrium ◽  
Dynamic Equilibrium ◽  
Static Equilibrium ◽  
Dynamical Model ◽  
New Model ◽  
Globally Stable

To study the changes of biomass of plankton and algae in lake environment, a new model was purposed. We applied the methods of qualitative analysis and numerical simulations. The main results were that there was a periodic solution, a globally stable equilibrium in this model under specific conditions, respectively. In conclusion, as increases of rate c, on which plankton are swallowed, there is a static equilibrium, a dynamic equilibrium, and then the equilibrium disappear, and at last the boundary point is globally stable, which means that plankton become extinct.

Nonlinear Vibration in a Vertical Rigid Rotor Supported by the Magnetic Bearing: Case Considering the Delays of Both Electric Current and Magnetic Flux

2007 ◽  
Author(s):  
Tsuyoshi Inoue ◽  
Motoki Sugiyama ◽  
Yasuhiko Sugawara ◽  
Yukio Ishida
Keyword(s):  
Magnetic Flux ◽  
Electric Current ◽  
Magnetic Force ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Nonlinear Phenomena ◽  
Control Force ◽  
Rigid Rotor ◽  
Rotating Speed ◽  
First Order

Active magnetic bearing (AMB) becomes to be widely used in various kinds of rotating machinery. However, as the magnetic force is nonlinear, nonlinear phenomena may occur when the rotating speed becomes higher and delay of control force increases. In this paper, the magnetic force is modeled by considering both the second order delay of the electric current and the first order delay of the magnetic flux, and the AMB force is represented by a power series function of the electric current and shaft displacement. The nonlinear theoretical analysis of the vertical rigid rotor supported by AMB is demonstrated. The effects of the delays and other AMB parameters on the nonlinear phenomena are clarified theoretically and experimentally.

scholarly journals Nestedness-Based Measurement of Evolutionarily Stable Equilibrium of Global Production System

Entropy ◽  
2021 ◽  
Vol 23 (8) ◽  
pp. 1077
Author(s):  
Jiaqi Ren ◽  
Lizhi Xing ◽  
Yu Han ◽  
Xianlei Dong
Keyword(s):  
Economic System ◽  
Value Chain ◽  
Production System ◽  
Stable Equilibrium ◽  
Dynamic Equilibrium ◽  
Analytical Framework ◽  
Biological Species ◽  
System Stability ◽  
Trade Network ◽  
Industrial Sectors

A nested structure is a structural feature that is conducive to system stability formed by the coevolution of biological species in mutualistic ecosystems The coopetition relationship and value flow between industrial sectors in the global value chain are similar to the mutualistic ecosystem in nature. That is, the global economic system is always changing to form one dynamic equilibrium after another. In this paper, a nestedness-based analytical framework is used to define the generalist and specialist sectors for the purpose of analyzing the changes in the global supply pattern. We study why the global economic system can reach a stable equilibrium, what the role of different sectors play in the steady status, and how to enhance the stability of the global economic system. In detail, the domestic trade network, export trade network and import trade network of each country are extracted. Then, an econometric model is designed to analyze how the microstructure of the production system affects a country’s macroeconomic performance.

scholarly journals The movement and forces of spinning solution in the nozzle during high-speed centrifugal spinning

2019 ◽  
Vol 14 ◽  
pp. 155892501982820 ◽  
Author(s):  
Yaoshuai Duan ◽  
Zhiming Zhang ◽  
Binbin Lu ◽  
Boya Chen ◽  
Zilong Lai
Keyword(s):  
Rotational Speed ◽  
High Speed ◽  
Large Scale ◽  
Production Efficiency ◽  
Critical Value ◽  
Parametric Model ◽  
Rotating Speed ◽  
Centrifugal Spinning ◽  
Novel Method

High-speed centrifugal spinning is a novel method to fabricate nanofiber. It has the potential to fabricate nanofiber on a large scale because its production efficiency is much greater than traditional methods. Nozzle is an important part of high-speed centrifugal spinning equipment because its length, shape, and diameter all will affect the morphology and quality of nanofiber. It is useful to study the movement and forces of spinning solution in the nozzle. In this article, the principle and equipment structure of high-speed centrifugal spinning are briefly introduced at first. Then the movement and forces of spinning solution are analyzed by establishing parametric model at nozzle. It can be found that the spinning solution is ejected from nozzle when the rotating speed reaches a critical value. The critical rotating speed is inversely proportional to the radius of nozzle and directly proportional to the viscosity of spinning solution. There are several nozzle structures proposed and compared for nozzle optimization. Finally, the effects of nozzle parameters, concentration of spinning solution, and rotational speed on the morphology of nanofiber are verified by high-speed centrifugal spinning experiments. It lays the foundation for optimizing spinning equipment.

Asynchronous Dynamic Coefficients of a Three-Lobe Air Bearing

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
Rafael O. Ruiz ◽  
Marcelo H. Di Liscia ◽  
Luis U. Medina ◽  
Sergio E. Díaz
Keyword(s):  
Three Dimensional ◽  
Ideal Gas ◽  
Magnetic Bearing ◽  
Air Bearing ◽  
One Dimensional ◽  
Rotating Speed ◽  
Dynamic Coefficients ◽  
Numerical Predictions ◽  
Air Film

The study of dynamic whirl behavior of air bearings is fundamental for an adequate rotordynamic analysis and future validation of numerical predictions. This work shows the dynamic response of the air film on a three-lobe bearing under asynchronous whirl motion. One-dimensional multifrequency orbits are used to characterize the bearing rotordynamic coefficients. The test rig uses two magnetic bearing actuators to impose any given orbits to the journal. The dynamic forces are measured on the test bearing housing by three load cells. Journal whirling excitation is independent of the rotating speed, thus allowing asynchronous excitations. The multifrequency excitation is applied at each rotating speed up to 11,000rpm, allowing the asynchronous characterization of the air film. The experimental procedure requires two linearly independent excitation sets. Thus, vertical and horizontal one-dimensional multifrequency orbits are applied as perturbations. Results show the synchronous and asynchronous dynamic coefficients of the air bearing. Asynchronous experimental results are compared to numerical estimation of the bearing force coefficients through solution of the isotropic ideal gas journal bearing Reynolds equation. Numerical dynamic coefficients are obtained as the effective coefficient values of the bearing when subject to a given orbit. A full characterization of the asynchronous rotordynamics coefficients of the bearing is presented in three-dimensional maps.

Hopf Bifurcation and Stability Analysis for a Predator-Prey Model with Delays

2013 ◽  
Vol 850-851 ◽  
pp. 901-904
Author(s):  
Hong Bing Chen ◽  
Li Mei Wang
Keyword(s):  
Stability Analysis ◽  
Hopf Bifurcation ◽  
Equilibrium Point ◽  
Stable Equilibrium ◽  
Critical Value ◽  
Stable Equilibrium Point ◽  
Predator Prey ◽  
Predator Prey Model ◽  
Necessary And Sufficient ◽  
Bifurcation And Stability

In this paper, a predatorprey model with discrete and distributed delays is investigated. The necessary and sufficient of the stable equilibrium point for this model is studied. Further, analyzed the associated characteristic equation. And, it is found that Hopf bifurcation occurs when τ crosses some critical value. Last, an example showed the feasibility of results.

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