• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.354-357
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• 2001

The developed method is proposed to identify rotor dynamic parameters. The method known imbalance vector, which renders over-determined linear system equation. The solution of the system equation can be obtained using least square method. The sensitivity analysis is performed to extract optimized solution, which is considered to be insensitive to inherent measurement errors. As an alternative approach to identify the parameters of bearings and rotor, adding a known imbalance to the rotor produces another equation set to make the system equations over-determined and linearly independent.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.672-675
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• 1997

This paper presents the identification of rotor dynamic parameters. The solution of the system equation can be obtained using least square method. The sensitivity analysis is performed to extract optimized solution, which is considered to be insensitive to inherent measurement errors. The cosine and sine term of orbit shapes can be obtained by experiment the orbit analysis at a different speed after doing orbit analysis at an arbitrary selected speed. This values measured time domain used to search the stiffness and damping coefficients of rotor bearing.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.220-226
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• 2002

A general solution method is presented to obtain the unbalance response orbit from the finite element based equations of motion of a gear-coupled two-shaft rotor-bearing system. Particularly, are proposed the analytical solutions of major and minor axis radii of the orbit. The method has been applied to analyze the unbalance response of a 800 refrigeration-ton turbo-chiller rotor-bearing system, having a bull-pinion speed increasing gear. The bumps of unbalance responses have been observed at the first torsional natural frequency due to the coupling of lateral and torsional dynamics by the gear meshing. Further, the proposed analytical solutions have been validated with results obtained by a full numerical approach.

• Journal of Aerospace System Engineering
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• v.9 no.1
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• pp.1-6
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• 2015

A critical speed analysis of oxidizer pump was peformed for a 7 ton class liquid rocket engine as the third stage engine of the Korea Space Launch Vehicle II. Based on the previously developed experimental 30 ton class turbopump and presently developing 75 ton class turbopump for the first and second stage rocket engine of Korea Space Launch Vehicle II, a layout and configuration of the 7 ton class turbopump rotor assembly are determined. A ball bearing stiffness analysis and rotordynamic analysis are performed for both of the bearing unloaded condition and loaded condition. Structural flexibility of the oxidizer pump casing is also included to predict critical speeds. From the numerical analysis, it is confirmed that the rotor system acquires sufficient separate margin of critical speed as a sub-critical rotor even though decrease of critical speed due to the casing structural flexibility.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.3
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• pp.112-119
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• 2003

This paper presents the identification of rotor dynamic parameters. The solution of the system equation can be obtained using least square method. The sensitivity analysis is performed to extract optimized solution, which is considered to be insensitive to inherent measurement errors. The cosine and sine term of orbit shapes can be obtain ed through the by experiment of the orbit analysis at a different speed after doing orbit analysis at an arbitrary selected speed. This values measured time domain are used to search the stiffness and damping coefficients of rotor bearing.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.8
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• pp.717-726
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• 2010

For the application into a 1 kWh flywheel energy storage system(FESS), this paper presents the design scheme of radial and axial hybrid magnetic bearings which use bias fluxes generated by permanent magnets. In particular, the axial hybrid magnetic bearing is newly proposed in this paper, in which a permanent magnet is arranged in axial direction so that it can support the rotor weight as well as provide a bias flux for axial magnetic bearing. Such hybrid magnetic bearings consume very low power, compared with conventional electromagnetic bearings. In this paper, to stably support a 140 kg flywheel rotor without contact, design process is explained in detail, and magnetic circuit analysis and three-dimensional finite element analysis are carried out to determine the design parameters and predict the performance of the magnetic bearings.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.9
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• pp.847-852
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• 2007

Design aspects of a bearing casing system of a power plant are mainly focused on the strength and weight of itself to have a more stable system. Since the rotor speed often passes through the critical speed region when the operation begins, the relation between the rotating frequency of the rotor and natural frequency of the casing is very important for a prevention of resonance. However, harmonic components above the rotating frequency have often been overlooked the design for the resonance avoidance. In this paper, it is revealed that resonance vibration is generated when the natural frequency of a bearing casing is close to the one of harmonics of basic rotating frequency(1x), and as a consequence, sensing qualify of seismoprobes attached to the bearing casing structure can be seriously damaged. In order to reduce the resonance vibration, some stiffeners are added to the casing structures. Significant reduction in the magnitude of vibration corresponding to 2x harmonic of basic rotating frequency is observed from both FE analysis and experiment.

• The KSFM Journal of Fluid Machinery
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• v.14 no.5
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• pp.69-74
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• 2011

This paper deals with the detail rotordynamic analysis for the vertical rotor system as development of vertical sea water lift pump for FPSO deep well. In a vertical rotor system, since linearized stiffness and damping coefficients of fluid film bearing are no longer be valid, hence the transient response analysis considering a fluid film force for every journal position in the bearing needs to be required. In this study, the transient response analysis of the proposed vertical pump rotor system was carried out in dry-run and wet-run conditions, respectively. The results show that orbital vibration responses of the rotor system remain stable at rated speed and thereby operating reliability of the vertical rotor system is confirmed. To overcome complexity of calculation pr ocedure and time consuming calculation of transient analysis, the calculating technique of steady-state response analysis is also proposed. The results of steady-state response obtained by applying the proposed technique to the rotor system are good agreement with the reference results, that is, transient responses.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.2
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• pp.99-104
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• 2014

Active vibration control methods are required in the high speed rotor systems supported by magnetic bearings. A prediction control technique is one of the control methods. Gain and phase angle are primarily chosen with analyzing the responses for a certain rotor speed. The feasibility of this technique has been reported for only analytical simulations. Therefore this paper constructs the test rig supported by ball bearings with a magnetic bearing type actuator and develops a prediction control system by using LabVIEW and Compact RIO. Finally as rotating speeds are modulated, the gains and phase angles for the speeds are determined with vibration control of the test rig. This leads that the prediction control technique may be applied to the rotor system with the magnetic bearing.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.5
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• pp.380-388
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• 2002

This paper describes the optimum design for low-pressure steam turbine rotor of 1,000 MW nuclear power plant by using a combined genetic algorithm, which uses both a genetic algorithm and a local concentrate search algorithm (e.g. simplex method). This algorithm is not only faster than the standard genetic algorithm but also supplies a more accurate solution. In addition, this algorithm can find the global and local optimum solutions. The objective is to minimize the resonance response (Q factor) and total weight of the shaft, and to separate the critical speeds as far from the operating speed as possible. These factors play very important roles in designing a rotor-bearing system under the dynamic behavior constraint. In the present work, the shaft diameter, the bearing length, and clearance are used as the design variables. The results show that the proposed algorithm can improve the Q factor and reduce the weight of the shaft and the 1st critical speed.