• 대한조선학회논문집
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• 제56권2호
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• pp.168-174
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• 2019

In order to investigate Propeller Open Water (POW) characteristics for the high-speed propeller in Large Cavitation Tunnel (LCT), the high-capacity inclined-shaft dynamometer was designed and manufactured. Its measuring capacities of thrust and torque are ${\pm}2200N$ and ${\pm}120N-m$, respectively. The driving motor is directly connected to the propeller shaft. Inclined angle of the propeller shaft can be adjusted up to ${\pm}10^{\circ}$. As the pressure inside LCT can be adjusted in the range of 0.1~3.0bar, we can carry out the POW test at high Reynolds number (above $1.0{\times}10^6$) without propeller cavitation and the cavitation test in uniform flow. After the new dynamometer setup in LCT, the Reynolds number variation test and propeller open-water test were conducted at the inclined angle of $0^{\circ}$ and $6^{\circ}$. The present POW results of the new dynamometer are compared with those of the existing high-capacity dynamometer in LCT and of the dynamometer in the towing-tank. Through systematic model tests and comparison with their results, the performance of the new inclined-shaft dynamometer was verified. It is thought the POW test for the high-speed propeller should be better conducted at high Reynolds number.

• 대한조선학회논문집
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• 제48권2호
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• pp.158-164
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• 2011

The study on the improvement of resistance performance is very important for coastal fishing boats in Korea, because the prices of fuel oil are gradually risen and the demand of high-speed fishing boats is increased lately. This study is concerned with the improvement of the resistance performance for Korean high-speed small coastal fishing boats. A semi-planing hull form of Korean small coastal fishing boat is selected in the role of initial hull. From the modification of the hull form parameters and the local characteristics of the hull form, the improvement of the resistance performance is achieved. The resistance performances of the initial and the modified hull forms are estimated by using a numerical simulation method. Also, ship model tests are carried out in ship model basin.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.429-432
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• 2001

This study presents an approach to model and to analyse traction power feeding system focused on the amplification of harmonic current. Through the research, 8-port network model which can be effectively applied to harmonic analysis is derived.

• 한국철도학회논문집
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• 제15권5호
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• pp.467-475
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• 2012

지오그리드에 의해 부분 보강 및 전면 보강된 2가지 타입의 블록식 보강토 옹벽으로 지지된 철도노반의 열차하중 전달 메카니즘을 조사하기 위해 정 동적 열차하중 재하실험을 수행하였다. 실험 노반은 높이 2.6m, 폭 5m, 뒷 길이 6m로 구축하였으며, 소정의 위치에 토압계, 변위계 및 변형율계를 설치하였다. 실험결과, 2가지 타입의 블록식 보강토 옹벽으로 지지된 철도노반에서의 벽체 변위 양상 및 보강 정도에 따른 연직 토압의 차이를 확인하였다. 또한 동적 열차하중 재하시 벽체 상부에서 변형율이 감소하는 현상을 볼 수 있었으며, 열차하중 재하에 의한 잔류 변형율 및 변형율 증분은 현행 설계기준에 비해 매우 작은 값을 보이고 있었다.

• Tribology and Lubricants
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• 제37권6호
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• pp.261-272
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• 2021

This study investigates the structural characteristics of oil-free, gas beam foil journal bearings (GBFJBs) for use in high speed motors. Mathematical modeling was carried out, and reaction force modeling for static load was performed to predict the structural characteristics of the GBFJB. Mathematical modeling and reaction force modeling for static load are performed to predict the structural characteristics of GBFJBs. The reaction force of the test bearing against static loads was measured during experiments and compared with the predicted results. The measured experimental data reveal the nonlinear stiffness characteristics of the GBFJB against varying displacement and agree well with the predictions. Dynamic load tests using an exciter allow to identify the vibration characteristics of the GBFJB. Test results show that the vibration displacement, dynamic force, and acceleration measured on the test bearing are most dominant at the applied dynamic load (synchronization) frequency. Futhermore, the test results show that the hysteresis area recorded during the dynamic tests increases with the excitation amplitude and frequency, and that the beam stick phenomena occurr at high excitation frequencies. The single degree of freedom (DOF) vibration model aids to identify the stiffness and damping coefficient of the GBFJB, which decrease as the excitation frequency increases.

• Tribology and Lubricants
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• 제12권1호
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• pp.22-28
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• 1996

This study was undertaken to investigate the dry wear characteristics and mechanism of KP-4M steel for plastic molding against SKD 61 hardened by heat treatment. The wear test was carried out under different conditions such as sliding speed, contact pressure, sliding distance, with frictional tester of pin on disc type. The wear loss on variation of sliding speed was little in lower speed range below 0.5 m/sec and in higher speed range above 1.5 m/sec,'but wear loss was high in intermediate speed range. The critical sliding speed, which showed the maximum value of specific wear rate, became lower with increased contact pressure. Increasing the contact pressure, the critical sliding distance Lcr which the wear mechanism changes from severe wear to mild wear was increased due to the decrease of oxidation reaction velocity. Through this study we suggested a model of generation and elimination process of wear debris of KP-4M steel for plastic molding.

• 한국철도학회논문집
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• 제10권6호
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• pp.742-750
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• 2007

본 논문은 장래 도입되는 KTX2 고속차량을 이용한 중련편성 운영계획 최적화를 위한 방법론 제시를 목적으로 한다. 중련편성 운영계획 최적화를 위한 수리적 모형을 제시하고, 제안된 수리적 모형의 적용방안을 제시한다. 특히 확률적 수요를 고려한 모형을 수립하여, 계획수립 단계에서 수요의 확률적 요소를 보다 현실적으로 반영하고, 모형내에서 좌석 서비스 수준을 직접 조정할 수 있다.

• 한국산학기술학회논문지
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• 제19권11호
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• pp.350-356
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• 2018

팬터그래프(Pantograph)와 전차선간의 동적 상호작용인 접촉력(contact force)은 차량에 대한 안정적 전원공급 특성인 집전성능을 평가하는 중요한 지표이다. 본 연구에서는 동력분산형 고속열차 시험차량인 HEMU-430X(High-speed Electric Multiple Unit - 430km/h eXperiment) 차량의 팬터그래프 동적 접촉력 특성을 전차선 장력에 따라 분석하였고, 이를 팬터그래프-전차선 동적 상호작용 모델을 이용한 해석결과와 비교하였다. 시험결과와 해석결과를 비교한 결과, 주요 동적접촉력 특성인 평균접촉력 및 접촉력 표준편차가 비교적 잘 일치하는 것을 확인하였다. 또한 해석모델을 이용하여 전차선 장력과 접촉력과의 상관관계를 차량 운행속도에 따라 제시하였으며, 이를 이용하여 각 운영속도별 최적 전차선 장력을 제시하였고 이를 국제규격과 비교하였다. 그 결과 해석을 통해 도출된 결과와 국제 규격에서 권장하는 전차선 장력이 비교적 잘 일치하는 것을 알 수 있었다.

• 한국정밀공학회지
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• 제19권2호
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• pp.203-212
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• 2002

Active magnetic hearings allow much high surface speed than conventional ball bearings and therefore greatly suitable for high speed cutting. This paper describes a design and test of an active magnetic bearing system with 16-pole radial magnets. The spindle is originally designed for a CNC lathe and driven by outer motor with 5.5 kW power and maximum speed 10,000 rpm. Considering static load condition and geometric restrictions, radial magnet is designed 16-pole type for smaller outer diameter of the spindle system. Dynamic system characteristics such as natural frequency, critical speed, stiffness, damping and system stabilities are simulated with a rigid rotor model including direct feedback controller. The designed spindle system is realized with digital PIDD controller to compensate phase lag of PWM amplifier and magnet coils. With levitation and step response experiment the control system characteristics are tested, and the spindle is rotated up to 10,000 rpm stab1y.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.830-837
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• 2010

Since it started the researches on a maglev train on 1960, Germany and Japan arrived to putting to practical use level and accomplished most tests from their test-line. Korea is in progress the preparation for a practical use of low-speed maglev train in 110 [km/h] class and Korea Railroad Research Institute(KRRI) is in progress of a research about core technology of maglev system for high-speed tube train of 700 [km/h] class. In this paper, authors suggest an effective design method of Linear Synchronous Motor(LSM) for high-speed tube train of 700 [km/h] class which has a wound type electro-magnet. Then, authors calculate a variety of properties by changing speed of the LSM model which is designed by a method based on some theoretical equations. Then, authors verify the validity of the method based on some theoretical equations through a verification of property values by Finite Element Method(FEM) analysis method. Finally, in order to design a shape of pole-shoe part of LSM electro-magnet which is hard to design with a basic design method, authors analyze a transition of property values by changing a pole-shoe width and current of the electro-magnet through an analytical method by FEM.