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.

Asynchronous Dynamic Coefficients of a Three Lobe Air Bearing

2007 ◽  
Author(s):  
Rafael O. Ruiz ◽  
Marcelo H. Di Liscia ◽  
Luis Medina ◽  
Sergio Di´az
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 non-synchronous 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 multi frequency excitation is applied at each rotating speed up to 11000rpm allowing the non-synchronous characterization of the air film. The experimental procedure requires two linearly independent excitation sets. Thus, vertical and horizontal one-dimensional multi-frequency 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 non-synchronous rotordynamics coefficients of the bearing is presented in three dimensional maps.

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.

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.

Reynolds Number Effects on the Performance Characteristic of a Small Regenerative Pump

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Shin-Hyoung Kang ◽  
Su-Hyun Ryu
Keyword(s):  
Reynolds Number ◽  
Three Dimensional ◽  
Internal Flow ◽  
Reynolds Numbers ◽  
Maximum Efficiency ◽  
Three Dimensional Flow ◽  
One Dimensional ◽  
Rotating Speed ◽  
Dimensional Modeling ◽  
Reynolds Number Effects

This paper studies the effect of the Reynolds number on the performance characteristics of a small regenerative pump. Since regenerative pumps have low specific speeds, they are usually applicable to small devices such as micropumps. As the operating Reynolds number decreases, nondimensional similarity parameters such as flow and head coefficients and efficiency become dependent on the Reynolds number. In this study, the Reynolds number based on the impeller diameter and rotating speed varied between 5.52×103 and 1.33×106. Complex three-dimensional flow structures of internal flow vary with the Reynolds numbers. The coefficients of the loss models are obtained by using the calculated through flows in the impeller. The estimated performances obtained by using one-dimensional modeling agreed reasonably well with the numerically calculated performances. The maximum values of flow and head coefficients depended on the Reynolds number when it is smaller than 2.65×105. The critical value of the Reynolds number for loss coefficient and maximum efficiency variations with Reynolds number was 1.0×105.

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