• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.7
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• pp.591-598
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• 2011

This paper presents dynamic analysis of FCEV(fuel cell electric vehicle) turbo blower. To analyze the dynamic characteristics of turbo blower, FEA(finite element analysis) and experimental test are performed. Evaluations of stress safety for rotor sleeve and impeller due to rotational force and shrink fit are performed. Rotor dynamic analysis is conducted by Campbell diagram and structure vibration analyses are performed using FEA and experimental test. Through these results, noise sources of turbo blower are verified.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.6
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• pp.484-489
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• 2003

The paper represents stability of a rotor system with the squeeze film damper (SFD) using an electromagnet. The electromagnet is installed in the inner damper of the SFD. The proposed SFD has basically the property of a conventional SFD and variable damping property according to variation of the applied electric current. Therefore, when the applied current Is controlled, the whirling vibration of the rotor system can be effectively reduced in a wide operational speed range. In the present work, the performance of the SFD was experimentally investigated according to changing the magnetic field strength. As the applied current increased, damping ratios increased, while whirling amplitudes greatly reduced.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.3
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• pp.172-179
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• 2003

Linear matrix Inequality based $H_\infty$ robust controller is designed to control the motion of a 4-axis unbalanced rigid asymmetric rotor supported and controlled by two active magnetic bearings in this paper. To this end, the equations of motion of the system are derived via Hamilton's variational principle and transformed to a state-space form for the standard $H_\infty$ control problem. LMI-based controller, which does not require additional assumptions beyond the usual stabilizability and detectability assumptions, is designed based upon the pole place weighting function and loopshaping technique. The obtained results are compared with those reported in the available literature and the efficiency of the proposed LMI-based $H_\infty$ control is revealed.

• Ocean Systems Engineering
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• v.14 no.2
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• pp.141-156
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• 2024

The turbine system converts the kinetic energy of water flow to electricity by rotating the rotor in a restricted waterway between the seabed and free surface. A turbine system's immersion depth and rotation direction are significantly critical in the turbine's performance along with the shape of the rotor. This study has investigated the hydrodynamic performance of the Savonius hydrokinetic turbine (SHT) according to the immersion depth and rotation direction using computational fluid dynamics (CFD) simulations. The instantaneous torque, torque coefficient, and power coefficients are calculated for the immersion ratios Z/D ranging [0.25, 3.0] and both clockwise (CW) and counterclockwise (CCW) rotations. A flow visualization around the rotor is shown to clarify the correlation between the turbine's performance and the flow field. The CFD simulations show that the CCW rotation produces a higher power at shallow immersion, while the CW rotation performs better at deeper immersion. The immersion ratio should be greater than the minimum of Z/D=1.0 to obtain the maximum power production regardless of the rotation direction.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.433-434
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• 2012

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.811-812
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• 2009

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.491-492
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• 2009

• The KSFM Journal of Fluid Machinery
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• v.16 no.3
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• pp.32-38
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• 2013

This paper deals with the study on the rotordynamic and experimental analysis of turbine-generator system connected with a magnetic coupling. Although magnetic coupling has been used to torque transmission of chemical processing pump rotating at under 3,600rpm, magnetic coupling in this study is applied to high-speed turbine-generator system using a working fluid that is refrigerant such as ammonia or R-124a. Results of rotordynamic design analysis are as follows. The first, shaft diameter nearest to outer hub of magnetic coupling has a big effect on the $1^{st}$ critical speed of generator rotor. The second, if the $1^{st}$ critical speeds of turbine rotor and generator rotor have enough to separation margin in comparison to rated speed, the $1^{st}$ critical speed of turbine-magnetic coupling-generator rotor train has enough to separation margin regardless of connection stiffness of magnetic coupling. The analytical FE model is guaranteed by impact test on the prototype and condition monitoring such as measurements of vibration and bearing temperature is also performed.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.5
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• pp.544-551
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• 2013

Recently high speed mixer, which is mixing, grinding, dispersion for liquid-liquid material, has been widely used several industries such as food, cosmetics, pharmaceuticals, fine chemicals, electronic material. This high speed mixer has a core element part called particle separation device. Particle separation device, which makes mixed liquid and liquid material using shear forces from a rotor and a stator, is a decisive factor in the distributed parts. In this study, we examined the velocity distribution of the two models of particle separation device using computation fluid dynamics, so that we were able to see the difference of the velocity distribution according to the shape. Also, by experiment, we observed that the use of rotor-screen type is deemed more suitable in case of accurately considering the effect of improving of the dispersibility through the circulation of the future.

• International Journal of Aeronautical and Space Sciences
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• v.10 no.2
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• pp.95-105
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• 2009

The flow fields around the HARTII rotor were numerically investigated using a viscous flow solver on adaptive unstructured meshes. An overset mesh and a deforming mesh technique were used to handle the blade motion including blade deflection, which was obtain from the HARTII experimental data. A solution-adaptive mesh refinement technique was also used to capture the rotor wake effectively. Comparison of the sectional normal force and pitching moment at 87% radial station between the two cases, with and without the blade deflection, showed that the blade loading is significantly affected by blade torsion. It was found that as the mesh was refined, the strength of tip vortex is better preserved, and the magnitude of high frequency blade loading, caused by blade-vortex interaction (BVI), is further magnified. It was also found that a proper time step size, which corresponds to the cell size, should be used to predict unsteady solutions accurately. In general, the numerical results in terms of the unsteady blade loading and the rotor wake show good agreement with the experimental data.