• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.344-349
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• 2012

This paper presents a new small-sized damper featuring magneto-rheological (MR) fluid which can be applied to vibration control system. The proposed MR damper consists of cylinder, piston, a couple of bearings, oil-seals and magnetic circuit which has two coils. In this damper, approximately 5cc of MR fluid is used. The damping force of the MR damper is designed to be followed by linear shear-mode Bingham-plastic model. In order to verify the performance of the MR damper, an experimental apparatus is established. In the experimental test, the damping force of the MR damper is measured with respect to time, displacement and velocity. In addition, the time response of MR damper is measured when 1A of step current is applied. Finally, The proposed small MR damper is applied to vibration control. In this process, a simple 1-DOF system is modeled and controlled using PID controller.

• 한국소음진동공학회논문집
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• 제22권11호
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• pp.1121-1127
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• 2012

This paper presents a new small-sized damper featuring magneto-rheological(MR) fluid which can be applied to vibration control system. The proposed MR damper consists of cylinder, piston, a couple of bearings, oil-seals and magnetic circuit which has two coils. In this damper, approximately 5cc of MR fluid is used. The damping force of the MR damper is designed to be followed by linear shear-mode Bingham-plastic model. In order to verify the performance of the MR damper, an experimental apparatus is established. In the experimental test, the damping force of the MR damper is measured with respect to time, displacement and velocity. In addition, the time response of MR damper is measured when 1A of step current is applied. Finally, the proposed small MR damper is applied to vibration control. In this process, a simple 1-DOF system is modeled and controlled using PID controller.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권2호
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• pp.140-148
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• 2000

In this paper, using surface micromachining technology with thick photoresist and aluminum, an SLM(Spatial Light Modulator), which is applied to the fields of adaptive optics and pattern recognition system, was fabricated and the electromechanical properties of the fabricated micro SLM are measured. In order to maximize fill-factor and remove mechanical coupling between micro SLM actuators, the micro SLM is composed of three aluminum layers so that spring structure and upper electrode are placed beneath the mirror plate, and $10\times10$ each mirror plate is individually actuated. Also, the micro SLM was designed to be able to modulate phase and amplitude of incoming light in order to have a continuity of phase modulation of incoming light. In the case of amplitude and phase modulation, maximum vertical displacement is 4$\mum$, and maximum angular displacement is $\pm4.6^{\corc}$ respectively. The height difference of the fabricated mirror plate was able to be reduced to 1100A with mirror plate planarization method using negative photoresist(AZ5214). The electromechanical properties of the fabricated micro SLM were measured with the optical measurement system using He-Ne laser and PSD(position sensitive device).

• 한국항해항만학회지
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• 제38권5호
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• pp.443-450
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• 2014

The objective of this study is to examine the nonlinear fluid characteristics near and inside a moonpool in various sea conditions. We estimate the flow of the free surface in a moonpool taking into account the viscosity effect and the hydrodynamic forces that affects a moonpool and hull through CFD calculations. The comparison of horizontal forces per wave length shows that the hydrodynamic force is greater for the long wave length than short wave length, and the greatest hydrodynamic force acts on the moonpool when the wave length is equal to the ship's length. The horizontal force decreases as the wave amplitude decreases, and the hydrodynamic force acting on the moonpool in ${\lambda}=LBP$ is 10 times that in ${\lambda}=LBP/3$. The free surface demonstrates the piston mode, in which it oscillates up and down while remaining essentially flat, and the rise of the free surface level increases as the wave length increases. We can assume that the hydrodynamic force acting on the moonpool increases owing to the effect of a strong vortex for ${\lambda}=LBP$ and owing to the rise of the free surface level for ${\lambda}=LBP{\times}2$.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.967-971
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• 2004

Today, as the demands for home appliances are increasing, the understanding of noise and vibration characteristics have become more important. It is hard to control its vibration and noise characteristics, because its mechanical structure is very complex. In this study a model of reciprocating compressor is developed. Spring, frame, and LDT are modeled as flexible body, and the other parts are modeled as rigid. FEM model of frame is simplified in order to save the simulation time. We validated the simple model by comparing their natural frequencies and mode shapes. Motor torque is applied to a rotor, and the piston is subjected to a gas pressure. The vibrational characteristics of compressor is analyzed with LS-DYNA. Its results are compared with the simulation results of rigid body frame. The effect of LDT is also studied by comparing the vibration of frame with the results of simulation with no LDT.

• 대한기계학회논문집A
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• 제41권7호
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• pp.683-689
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• 2017

고유가, 환경규제 등의 국제무역환경 변화에 따라 수출주력상품인 유압 브레이커의 고부가가치화를 위하여 지능형 전자제어유압시스템 분야인 ICT 융합기술을 활용하여 암반특성을 예측하고 최적모드(다단형)로 구동하는 지능형 파쇄기술 및 에너지 효율을 극대화할 수 있는 유압 브레이커 개발에 관한 연구를 수행하였다. 본 연구에서는 암반의 강도에 따라 최적의 타격력을 제공하기 위해 근접센서를 이용해 암반 타격 시 피스톤의 하강 깊이를 측정하고 이를 통해 암반의 특성을 판별하여 타격력을 결정하는 피스톤 스트로크의 길이를 솔레노이드 밸브를 이용해 제어하였다. 다단 타격시스템을 위해 컨트롤러와 디스플레이/조작장치를 개발하였고, 무선통신을 이용하여 상호 정보교환이 가능하도록 하였다. 최종적으로 암반 강도에 따라 3단으로 타격할 수 있는 제어시스템을 개발하였고, 실차실험을 통해 이를 검증하였다.

• 한국진공학회지
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• 제12권3호
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• pp.157-161
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• 2003

오늘날 환경 산업의 발달과 함께 수정진동형 기압계 같은 정밀한 기압계가 개발됨에 따라 이를 교정하기 위한 보다 우수한 압력표준기가 필요하게 되었다. 수은압력계는 압력변화에 따른 수은의 높이차를 측정하여 압력을 계산하는 압력표준장비로 지금까지 많이 사용되어 왔으나 정밀 기압 측정의 경우 수은의 높이 측정을 초음파나 레이져를 사용해야 하므로 측정시스템이 복잡해지고 수은의 맹독성으로 인해 그 사용이 제한적이다. 그 대신 기체식 압력저울을 이용한 정밀한 기압계 교정이 오늘날 많이 시도되고 있으나 압력저울은 교정 시 피스톤 주위 공간을 진공으로 만들어 측정해야 하므로 진공중의 분동 교환이 사용의 가장 큰 걸림돌로 지적되어 왔다. 본 논문에서는 이를 해결하기 위해 진공을 깨지 않고도 효율적으로 분동을 교환할 수 있는 장치를 고안, 제작하였다. 본 장치를 이용하면 교정 시 측정시간의 단축과 함께 잦은 대기 노출로 인한 피스톤, 실린더, 분동의 오염과 피스톤과 실린더 간격 사이의 불순물 삽입으로 인한 압력표준기 성능저하를 예방할 수 있다. 아울러 이 장치로 실제 상용되고 있는 초정밀 기압계의 특성 검사를 수행하여 그 실험 결과를 기술하였다.

• Tribology and Lubricants
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• 제32권3호
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• pp.82-87
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• 2016

We performed an experimental research on lubricant oil in dual fuel medium-speed engines. It is important to select the appropriate lubricant oil because it could significantly affect engine lifetime and performance. We generally recommend the selection of the lubricant oil according to the fuel grades as contents in the project guide. However, it is a considerable challenge for shipyards to implement this concept because of the lack of space to install the complicated lubricating oil system for dual fuel engines. Therefore, we determine the adaptability of one-common lubricant oil for HiMSEN dual fuel engine through this experimental research. To check abnormality in gas mode operation and durability of engine components when a lubricating oil with high BN (base number) is used, overhaul inspections and lubricant oil analysis are carried out two times, and four times, respectively, during an operation of approximately 300 h. We investigated the variations in kinematic viscosity, base number, element quantity, pentane insoluble and sulfated ash in lubricant oil analysis. Moreover, we also investigated whether the deposit formation or wear occurred in various bearings, injectors, exhaust valves, intake valves, piston rings and so on through the overhaul inspections. There are no problems in the lubricant analysis and the overhaul inspections. Through the experimental research, we confirm that one-common lubricant oil should be selected according to the higher sulfur content of fuel oil in dual fuel engines.

• 한국자동차공학회논문집
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• 제23권1호
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• pp.97-104
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• 2015

This study is a part of the high pressure injection system development on the Turbo GDI engine in order to reduce smoke emission in case of using the low volatile(high DI) fuel which is used as normal gasoline fuel in the US market. Firstly, theoretical approach was done regarding gasoline fuel property, performance, definition of particle matters and its creation as well as problems of the high DI fuel. In this experimental study, 2L Turbo GDI engine was selected and optimized system parameter was inspected by changing fuel, fuel injection mode (single/multiple), fuel pressure, distance between injector tip and combustion chamber, start of injection, intake valve timing in engine dyno at all engine speed range with full load. In case of normal gasoline fuel, opacity was contained within 2% in all conditions. On the other hands, in case of low volatile fuel (high DI fuel), it was confirmed that the opacity was rapidly increased above 5,000 rpm at 14.5 ~ 20 MPa of fuel pressure and there were almost no differences on the opacity(smoke) between 17 MPa and 20 MPa fuel pressure. According to the SOI retard, smoke decrease tendency was observed but intake valve close timing change has almost no impact on the smoke level in this area. Consequently, smoke decrease was observed and 16% at 6000rpm respectively with injector washer ring installed. By removing injector washer to make injector tip closer to the combustion chamber, smoke decrease was observed by 46% at 5,500 rpm, 42% at 6,000 rpm. It is assumed that the fuel injection interaction with cylinder head, piston head, intake and exhaust valve is reduced so that impingement is reduced in local area.

• 한국해안·해양공학회논문집
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• 제30권6호
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• pp.242-252
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• 2018

진동수주형의 파력발전구조물(OWC-WEC)는 파랑에너지 흡수장치 중에 가장 효율적인 것으로 알려져 있다. 이 장치는 공기실 내부에서 해수면의 상 하운동을 공기흐름으로 변환하고, Wells 터빈으로 대표되는 터빈의 구동력으로부터 전기에너지가 생산된다. 따라서, 높은 전기에너지를 얻기 위해서는 공기실 내부에서의 수면변동에 피스톤모드의 공진을 유발시켜 수면진동을 증폭시킬 필요가 있다. 본 연구에서는 해수소통구를 구비한 신형식의 OWC-WEC를 상정하고, 구조물에 의한 파랑변형, 공기실 내에서 수면변동과 노즐에서 공기유출속도 및 해수소통구에서 해수흐름속도를 수치해석적으로 상세히 평가한다. 수치해석모델은 Navier-Stokes solver의 혼상류해석기법에 기초한 공개 CFD code인 OLAFLOW 모델을 적용하며, 모델의 타당성을 검증하기 위하여 기존의 실험결과 및 수치해석결과와를 비교 논의한다. 본 연구의 범위 내에서 Ursell수가 커질수록 노즐에서 공기흐름속도가 증가하며, 공기실 내부에서 외부로 유출되는 공기속도가 외부에서 공기실 내부로 유입되는 공기속도보다 더 크다 등의 중요한 사실을 알 수 있었다.