• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1757-1763
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• 2010

Flywheel energy storage system (FESS) is defined as a high speed rotating flywheel system that can save surplus electric power. The FESS is proposed as an efficient energy storage system because it can accumulate a large amount of energy when it is operated at a high rotating speed and no mechanical problems are encountered. The FESS consists of a shaft, flywheel, motor/generator, bearings, and case. It is difficult to simulate rotor dynamics using common structure simulation programs because these programs are based on the 3D model and complex input rotating conditions. Therefore, in this paper, a program for the FESS based on the 2D FEM was developed. The 2D FEM can model easier than 3D, and it can present the multi-layer rotor with different material each other. Stiffness changing of the shaft caused by shrink fitting of the hub can be inputted to get clear solving results. The results obtained using the program were compared with those obtained using the common programs to determine any errors.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.10a
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• pp.319-323
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• 1996

\ulcorner\ulcorner\ulcorner\ulcorner 80,000 rpm \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner(ultra-centrifuge)\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner. \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner(critical speed)\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner(separation margin)\ulcorner \ulcorner\ulcorner, \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner-\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner. \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner \ulcorner\ulcorner\ulcorner, \ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner(extra slender shaft)\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner. \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner, \ulcorner\ulcorner 1\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner(bumper ring) \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner(guide bearing)\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner. \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner(finite element method)\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner, \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner(damping)\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.3
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• pp.240-248
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• 2013

Torsional vibrations, such as the gear rattle of the manual transmission in vehicle systems, are correlated with the firing stroke from the engine. These vibro-impacts can be examined based upon linear time-invariant analysis. In order to understand the gear dynamics, a specific manual transmission with a front-engine front-wheel drive configuration is investigated. A method to reduce the degrees of freedom is suggested based upon the eigensolutions and frequency response functions, which will lead to the development of an efficient matrix size. The dynamic characteristics of single- and dual-mass flywheels are then compared. The effect of the dual-mass flywheel is investigated based upon the mobility analysis, which will lead to understanding of the concepts for avoiding vibro-impacts. A linear time-invariant system model is examined by employing the effective clutch stiffness from a two-stage clutch damper. Thus, the relationship between the dynamic characteristics and the clutch damper can be predicted by assuming a combination of different stage stiffness levels.

• Tribology and Lubricants
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• v.31 no.6
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• pp.294-301
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• 2015

In this paper, we predict the rotordynamic force coefficients of tilting pad journal bearings (TPJBs) with rocker-back pivots, and we compare the predictions to recently published predictions and test data. The present TPJB model considers the rocker-back pivot stiffness calculated based on the Hertzian contact-stress theory, which is nonlinear with the application of a force . For the five-pad TPJB in load-between-pad and load-on-pad configurations, the predictions show the pressure- and film-thickness distributions, the deflection and stiffness of the individual pivots, and bearing stiffness and damping coefficients. The minimum film thickness and peak pressure occur at the bottom pad on which the applied load is directed. Because of the preload, the pres- sure is positive even at the upper pad in the opposite direction to the applied load. The pivot deflection and stiff- ness are maximum at the bottom pad that receives the heaviest pressure load. The predicted stiffness coefficients increase as the static load and rotor speed increase, while the damping coefficients decrease as the rotor speed increases, but increase as the static load increases. In general, the predicted stiffness coefficients agree well with the test data. The predicted damping coefficients overestimate the test data, particularly for large static loads. In general, the current predictive model considering the pivot stiffness improves the accuracy of the rotordynamic performance compared to previously reported models.

• Journal of Ocean Engineering and Technology
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• v.13 no.4 s.35
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• pp.10-18
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• 1999

본 논문에서는 대형구조물의 해석에 있어서 부분구조합성법과 섭동법을 이용하여 복잡한 비선형시스템의 해석방법을 제안하였다. 해석방법은 전체시스템을 먼저 몇 개의 분계로 분할한다. 각 분계의 운동방정식에 비선형항이 존재하여도 전체시스템의 지배적 진동모드는 선형모드라는 가정하에 이 시스템의 각 분계를 모드좌표로 변환한다. 이때, 비선형항은 근사적으로 변환한다. 그리고 섭동법을 이용하여 각 분계의 모드좌표방정식은 섭동좌수별로 정식화되어 순차적으로 구해진다. 비선형의 감도는 비선형계수로 정의되고, 그에 상응하는 강성에 의해 구해진다. 제안된 해석방법으로 비선형회전체, 비선형 베어링-페데스탈로 구성된 대형시계구조물의 진동을 해석하였다. 해석방법의 유효성을 평가하기 위해 응답의 정도와 계산소요시간을 유한요소법의 결과와 비교 분석하였다.

• Tribology and Lubricants
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• v.35 no.5
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• pp.310-316
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• 2019

This paper presents two methods for designing a high-speed air spindle operated over the rotational speed of 50,000 rpm. The first method is an approximate method, which assumes a symmetric spindle shape even though it is not symmetric in reality. The second is an analysis of rotordynamics using beam and solid models. The approximate method can be used to calculate the bearing load capacities, stiffness and damping coefficients, stability of the shaft system, and response of the forced excitation from the unbalanced mass. Designers can use this method to determine the dimensions of the desired spindle at the first stage of the design. The more detailed behavior of the spindle can be calculated using the rotordynamics theory using beam and solid models based on the Finite Element Method. In this paper, a spindle, with two air bearings, one motor at the end, and two air thrust bearings, is newly developed. The solutions from the two rotordynamics theories are compared with the solution obtained using the approximate method. The three calculations are in agreement, and the procedure for the design of a spindle system, supported on the externally pressurized air bearings, ispresented and discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.10
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• pp.1029-1037
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• 2015

Recently, the importance of rotordynamic stability has been increased because of the tendency to employ ultra-high speeds in rotating machinery. In particular, the dynamic characteristics of gas bearings for high-speed rotating machinery need to be identified at various excitation frequencies to predict the rotor's behavior. In this study, we perform dynamic loading tests for gas-foil bearings (GFBs) to determine the bump foil structure and an air-film combined bump-foil structure for varying excitation frequencies. We calculate the dynamic characteristics from the measured force and displacement data. The air film is generated by a pressurized air supply. Based on the results, the stiffness coefficients of the bump structure and the air-film combined bump structure increased, while the damping coefficients decreased at increasing excitation frequencies. Further, the stiffness and damping coefficients of the air-film combined structure show lower values than those of the bump structure. Consequently, we identify the frequency-dependent dynamic characteristics of the bump structure and the effect of gas film on the dynamic characteristics of GFBs. Furthermore, to reveal the effectiveness of the proposed method, we perform experiments and discuss two methods of extracting the dynamic characteristics from the measured data.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.8
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• pp.583-591
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• 2014

The mathematical modeling on the free vibration and stability of a multi-stepped shaft of turbo compressor is performed in this study. The multi-stepped shaft is modeled as a non-uniform Timoshenko beam supported by anisotropic bearings. It is assumed that the shaft is spinning with constant speed about its longitudinal axis and subjected to a conservative axial force induced by front and rear impellers attached to the shaft. The structural model incorporates non-classical features such as transverse shear and rotary inertia. A structural coupling between vertical and lateral motions is induced by Coriolis acceleration terms. The governing equations are derived via Hamilton's variational principle and the equations are transformed to the standard form of an eigenvalue problem. The implications of combined gyroscopic effect, conservative axial force, bearing stiffness and damping are revealed and a number of pertinent conclusions are outlined. In this study analytical results are compared with those from ANSYS finite element analysis and experimental modal testing.

• Journal of Korea Multimedia Society
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• v.11 no.10
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• pp.1376-1384
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• 2008

Numerous researches on network self-configuration have been conducted on Wireless Sensor Network (WSN) and Ad Hoc network but the results have not been applied yet for factory automation. This paper presents development of intelligent process management systems conducting process monitoring and control irrelevant to physical position of a plant operator. The systems are indispensable for diagnosis of rotating machines which cannot exploit wired network. The system was implemented in a Personal Digital Assistant (PDA) using Bluetooth communication protocol. When a mobile terminal reaches to communication range of the process management server, the server detects the mobile terminal to reconfigure plant network automatically. The server authenticates a user of the terminal to download and installs monitoring and control program considering authorized level of the user. If the terminal leaves communication range of the server, it deletes the node from the network and removes the program automatically to save resources and prevent security problems such as missing terminal. Operation of developed functions was verified in a testbed emulating steel-making plant.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.12
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• pp.1483-1487
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• 2013

Water injection pump outputs oil with high pressure during this process, seawater is injected into the well to recover the well pressure and maintain high productivity. A water injection pump has high productivity, and therefore, it serves as a key piece of equipment in marine plants. In this light, water injection pumps are being studied widely in industry. In this study, the rotor dynamics is analyzed to determine the natural frequency according to the bearing stiffness and operation speed change. This study aims to establish the pump reliability through critical speed, stability, and unbalance response analysis.