• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.2
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• pp.26-31
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• 2011

This article provides the systematic design methodology for a tilting pad journal bearing. First the dynamic factors for the bearing are selected with the critical speed analysis. The pad bearing is then designed to have its best mechanical efficiency by simulations with changing of the number of pad and the lubricant flow rate with meeting the design specifications such as metal temperature, clearance and so on. And the simulation results are reviewed to compare with an experimental test. Finally the stability of rotor with the designed bearing is investigated. This methodology is successfully applied to the rotor for 1.2MW turbo-blower.

• 유체기계공업학회:학술대회논문집
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• 1999.12a
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• pp.141-146
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• 1999

The comming of high speed computers with large memory size in recent years has allowed the practical development of codes which solve the Reynolds-averaged NAvier-Stokes (RANS) equations in three dimensions. Such codes are already used by the large engine manufacturers for the advanced design of some engine components. Different computational fluid dynamics approaches and turbulence models exist, and it seems essential today to establish their degree of validity for application to typical configurations in turbomachinery. In 1993 the Turbomachinery Committee of the IGTI of ASME has issued an open invitation to predict the flow details of an isolated transonic fan rotor called as NASA ROTOR 37. This paper reports this test case.

• Journal of Electrical Engineering and Technology
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• v.12 no.3
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• pp.1166-1176
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• 2017

Estimation errors of the rotor speed and position in sensorless control systems of Permanent Magnet Synchronous Motors (PMSM) will lead to low efficiency and dynamic-performance degradation. In this paper, a parallel-type extended nonlinear observer incorporating the nominal parameters is constructed in the stator-fixed reference frame, with rotor position, speed, and the load torque simultaneously estimated. The stability of the extended nonlinear observer is analyzed using the indirect Lyapunov's method, and observer gains are selected according to the transfer functions of the speed and position estimators. Taking into account the parameter inaccuracies issue, explicit estimation error equations are derived based on the error dynamics of the closed-loop sensorless control system. An equivalent flux error is defined to represent the back Electromotive Force (EMF) error caused by the inaccurate motor parameters, and a compensation strategy is designed to suppress the estimation errors. The effectiveness of the proposed method has been validated through simulation and experimental results.

• Journal of KSNVE
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• v.10 no.1
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• pp.153-159
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• 2000

This paper presents a new method for including the dynamic stiffness of the stationary parts in rotordynamic analysis. As a consequence of the support dynamics, critical speeds are varied and/or additional critical speeds are introduced. Therefore, dynamic effects of the support are often significant in high speed turbomachinery, but most of analysis has considered the support as a rigid body or a simple structure. The proposed method is based on the coupled characteristics of the driving point and transfer frequency response functions of the support system to model the equivalent spring-mass series in finite element analysis. To demonstrate the applicability of the simulation procedures provided, it is applied to the rotor model of the double suction centrifugal pump. Results of the suggested equivalent-support rotor model including coupled effects agree well with the entire pump model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.1056-1061
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• 2004

The vibration of rotor systems is caused by various factors, such as misalignment, unbalance, gear meshing, error of assembly, etc. Modal test and TDA/ODS analysis were done. The dynamic analysis of the armature was done with SAMCEF which is a commercial software for finite element and kinematic analysis. The transient response of the armature is calculated by the SAMCEF with the consideration of magnetic force and bearing stiffness, which are the essential elements for the design of high speed cutter. Main frequency of the vibration is due to the unbalance of the armature. The FEM analysis model considering unbalance and the high speed cutter have same vibration properties. The vibration sources of the high speed cutter is proved to be unbalance.

• Structural Engineering and Mechanics
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• v.33 no.1
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• pp.47-66
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• 2009

Radiation damping due to wave propagation in unbounded domains may cause a significant reduction of structural vibrations when excited near resonance. Here a novel matrix-valued algebraic Pad$\acute{e}$-like stiffness formulation in the frequency-domain and a corresponding state equation in the time domain are elaborated for a soil-structure interaction problem with a layered soil excited in a transient manner by a flexible rotor during startup and shutdown. The contribution of radiation damping caused by a soil-layer upon a rigid bedrock is characterized by the corresponding amount of critical damping as it is used in structural dynamics.

• New & Renewable Energy
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• v.3 no.3
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• pp.54-62
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• 2007

The present paper describes the scale effect correction methods for scaled NREL Phase VI wind turbines by using CFD[computational fluid dynamics). For the corrections of wind turbine scale effect, various researches on the helicopter rotor scale effect were investigated and the feasibility study of the methods was performed to correct wind turbine scale effect. The present paper also introduces scale effect correction methods based on two dimensional lift slope. In order to test the present method, performance analyses of NREL Phase VI wind turbines under various scale conditions were carried out and new correction method was applied. Granting that the new correction method is valid only above Reynolds No. 100,000, it showed reasonable agreement between model and full scale wind turbines in the linear torque region.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.293-295
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• 1995

In this article a fuzzy controller and neural network adaptive observer is proposed and applied to the case of induction motor control. The proposed observer which comprises neural network flux observer and neural network torque observer is trained to learn the flux dynamics and torque dynamics and subjected to further on-line training by means of a backpropagation algorithm. Therefore it has been shown that the robust control of induction motor neglects the rotor time constant variations.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.1
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• pp.1-9
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• 2004

In this paper, an efficient modeling method of Horizontal-Axis Wind Turbine(HAWT) system is proposed. This method Is based on representing a HAWT system as a multi-body system with several rigid bodies i.e. rotor blade, low/high speed shaft, gear system, md generator. Also, simulation software WINSIM is developed to evaluate performance of wind turbine system. Simulation results show that the proposed modeling method and simulation software are efficient and reliable.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.75-78
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• 2003

In this paper, an active magnetic bearing-based motor-generator(M-G) system is designed and controlled using a digital PID control concept. The plant dynamics consisting of actuator and rigid rotor dynamics are described. And some experiments are conducted with each global control and local control concept. From the whirl test, the M-G set can be controlled within about ${\pm}10{\mu}m$ gap variation at the rotational speed of 6000rpm.