• International Journal of Naval Architecture and Ocean Engineering
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• 제8권1호
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• pp.73-82
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• 2016

In order to extend the operational life of Underwater Moored Platforms (UMPs), a horizontal axis water turbine is designed to supply energy for the UMPs. The turbine, equipped with controllable blades, can be opened to generate power and charge the UMPs in moored state. Three-dimensional Computational Fluid Dynamics (CFD) simulations are performed to study the characteristics of power, thrust and the wake of the turbine. Particularly, the effect of the installation position of the turbine is considered. Simulations are based on the Reynolds Averaged Navier-Stokes (RANS) equations and the shear stress transport ${\kappa}-{\omega}$ turbulent model is utilized. The numerical method is validated using existing experimental data. The simulation results show that this turbine has a maximum power coefficient of 0.327 when the turbine is installed near the tail of the UMP. The flow structure near the blade and in the wake are also discussed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.633-638
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• 2009

This paper presents an optimal design of a magnetorheological(MR) fan clutch based on finite element analysis and also presents torque control of engine cooling fan using a sliding mode control. The MR fan clutch is constrained in a specific volume and the optimization problem identifies the geometric dimension of the fan clutch that minimizes an objective function. The objective function for the optimization problem is determined based on the solution of the magnetic circuit of the initially designed clutch. Under consideration of spatial limitation, design parameters are optimally determined using finite element analysis. After describing the configuration of the MR fan clutch, the viscous torque and controllable torque are obtained on the basis of the Bingham model of MR fluid. Then, a sliding mode controller is designed to control the torque of the fan clutch according to engine room temperature and control performance is evaluated through computer simulation.

• 한국소음진동공학회논문집
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• 제23권5호
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• pp.463-471
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• 2013

This paper presents design and control of electronic control suspension(ECS) equipped with controllable magnetorheological(MR) damper for passenger vehicle. In order to achieve this goal, a cylindrical type MR fluid damper that satisfies design specification of a middle-sized commercial passenger vehicle is proposed. After manufacturing the MR damper with design parameters, their field-dependent damping forces are experimentally evaluated and compared with those of a conventional damper. A quarter-vehicle MR ECS system consisting of sprung mass, spring, tire, controller and the MR damper is established in order to investigate the ride comfort performances. On the basis of the governing equation of motion of the suspension system, five control strategies(soft, hard, comfort, sport and optimal mode) are formulated. The proposed control strategies are then experimentally realized with the quarter-vehicle MR ECS system. Control performances such as vertical acceleration of the car body and tire deflection are evaluated in frequency domains on random road condition. In addition, performance comparison of WRMS(weighted root mean square) of the quarter-vehicle MR ECS system on random road are undertaken in order to investigate ride comfort characteristics.

• 한국소음진동공학회논문집
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• 제21권12호
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• pp.1199-1205
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• 2011

In the present work, a seat suspension system adopting semi-active damper is evaluated for driver's ride quality. A cylindrical type of ER(electrorheological) damper is designed and manufactured for the seat suspension of heavy vehicles. The governing equation is derived under consideration of human vibration. A sliding mode controller is then synthesized and experimentally realized on the manufactured ER seat suspension while a driver is sitting on the controlled seat. Ride quality is evaluated by fatigue decreased proficiency boundary, vibration dose value and crest factor utilizing weighted-acceleration according to ISO2631.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.121-126
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• 2001

This paper presents the experimental study for the reduction of transmitted shock waves in smart structures incorporating MR insert. MR fluid is filled within the two aluminum layers and two piezoceramic disks are embedded on the host plate as a transmitter and a receiver of the shock wave. Pulse wave generated by the transmitter is transmitted to the receiver through the MR insert and the plate. By applying magnetic field to the MR insert, the amplitude of the transmitted shock wave is reduced remarkably. The attenuation performance is tested by changing the applied magnetic field on MR inserts in two ways: by changing angle of permanent rubber magnet from 90 to 5 with 5 decrements, by using electromagnet in which magnetic field is controllable. The propagating wave speed of MR insert is also investigated.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.323-327
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• 2001

Electrorheological(ER) and magnetorheological(MR) fluids have a unique ability to increase the dynamic yield stress of the fluid substantially when electric or magnetic field is applied. Controllable fluids such as ER and MR fluids have received considerable attention as several components of engineering devices. One of them is a smart impact damper using ER/MR fluids. Impact damper system can be used in the joint mechanism of railroad vehicle, protection equipment of elevator's drop, and launch equipment of aircraft. This paper presents the results of an analytical study of the performance of a smart impact damper to suppress vibration during impact excitation. The damping capabilities of MR impact damper for variable applied current are analyzed using Bingham model under sudden impact load.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.I
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• pp.247-250
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• 2005

In this paper, new address electrode having separated dual electrodes is suggested to reduce addressing time in ac PDP. It had been found that both the formative and jitter width of the suggested electrode are improved by $10{\sim}20$ % compared with the conventional one on IMID 04'. So we experiment other several kinds of the separated electrodes, and the change in discharge characteristics is analyzed by using a two-dimensional fluid simulation. The key feature of the suggested structure is that the distribution of Xe and Ne ion is controllable during the address periods without significant increases in the capacitive load of the address electrodes.

• 한국지진공학회논문집
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• 제6권2호
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• pp.63-71
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• 2002

본 논문에서는 미국토목학회(ASCE)의 사장교에 대한 첫번째 벤치마크 문제를 이용하여 제어-구조물 상호작용을 고려한 새로운 반능동제어 기법을 제안하였다. 이 벤치마크 문제에서는 2003년 완공 예정으로 미국 Missouri주에 건설 중인 Cape Girardeau 교를 대상 구조물로 고려하였다. Cape Girardeau 교는 New Madrid 지진구역에 위치하고, Mississippi 강을 횡단하는 주요 교량이라는 점 때문에 설계단계에서부터 내진 문제를 중요하게 고려하였다. 본 연구에서는 MR 유체 감쇠기를 제어 장치로 제안하였고, clipped-optimal 알고리듬을 제어 알고리듬으로 사용하였다. 또한, 대용량 MR 유체 감쇠기 실험 결과를 이용하여, Bingham 모델, Bouc-Wen 모델, 수정된 Bouc-HWen 모델과 같이 수치해석에 이용할 수 있는 다양한 동적 모델을 개발하였다. MR 유체 감쇠기는 제어가능한 에너지 소산장치이며 구조물에 에너지를 가하지 않기 때문에 제안된 제어기법은 한정입출력 안정성이 보장된다. 수치해석을 통해, MR 유체 감쇠기를 이용한 반능동제어 기법이 사장교의 응답 감소에 효과적인 방법임을 증명하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.375-380
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• 2007

This paper presents optimal design of controllable magnetorheological (MR) shock absorbers for passenger vehicle. In order to achieve this goal, two MR shock absorbers (one for front suspension; one for rear suspension) are designed using an optimization methodology based on design specifications for a commercial passenger vehicle. The optimization problem is to find optimal geometric dimensions of the magnetic circuits for the front and rear MR shock absorbers in order to improve the performance such as damping force as an objective function. The first order optimization method using commercial finite element method (FEM) software is adopted for the constrained optimization algorithm. After manufacturing the MR shock absorbers with optimally obtained design parameters, their field-dependent damping forces are experimentally evaluated and compared with those of conventional shock absorbers. In addition, vibration control performances of the full-vehicle installed with the proposed MR shock absorbers are evaluated under bump road condition and obstacle avoidance test.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.569-572
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• 2006

In present study, the influence of changing combustor pressure on flame stabilization and nitrogen oxide (NOX) emission in the swirl flame with secondary fuel injection was investigated. The combustor pressure was controlled by suction at combustor exit. Pressure index ($P^*=Pabs/Patm$), where Pabs and Patm indicated the absolute pressure and atmosphere pressure, was controlled in the range of 0.7~1.15 for each equivalence ratio conditions. It could be observed that flame stable region became narrower with decreasing equivalence ratio and pressure index. In this combustion system, stable flames were formed until $P^*=\;0.7$. Emission index decreased with decreasing pressure index for overall equivalence ratio conditions and NOx reduction rates were almost identical for $P^*<1$ regardless of equivalence ratio though EINOx values showed different level with change of equivalence ratio for $P^*{\geq}1$. It is also observed that EINOx decreased with increasing secondary fuel injection ratio. Emission index of nitric oxide was controllable by adjusting the changing combustor pressure and injecting secondary fuel and this NOx reduction technology is applicable to industrial furnaces and air conditioning system.