• 한국추진공학회지
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• 제17권2호
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• pp.128-134
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• 2013

우주발사체 추진기관 공급계에서 2-way 솔레노이드밸브는 제어시스템의 명령에 의해 추진제 탱크를 가압하여 탱크내의 압력을 조절한다. 가압용 솔레노이드밸브의 제작에 앞서 설계검증 및 기본적인 작동특성을 분석하기 위해 AMESim상용코드를 이용하여 해석모델을 수립하였다. FLUENT 상용코드를 이용하여 내부유동해석을 수행하여해 해석의 정확도를 높이고, 모델을 검증하기 위해 동특성 해석을 통해 입구압력에 따른 작동시간을 시험결과와 비교하였고 잘 일치함을 확인하였다. 또한 해석 모델을 이용하여 컨트롤밸브와 기본밸브의 설계변수에 대한 밸브의 동특성 해석을 수행하였다. 해석을 통해 기본밸브의 시트형상과 직경비에 따른 밸브의 작동시간, 작동성능, 개폐압력을 예상하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제33권8호
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• pp.1100-1106
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• 2009

최근, 디젤기관의 고효율달성을 위한 방법으로 밀러방식의 고팽창사이클에 대한 연구가 관심이 높다. 본 연구에서는 고팽창 디젤사이클을 구성하여 열역학적으로 해석하고, 몇몇 인자에 의한 사이클 특성을 분석하였다. 이론해석 결과 흡기밸브 닫힘시기가 지각될수록 유효압축비의 감소로 상대적인 팽창비의 효과는 커져 팽창-압축비의 비는 기대할 수 있었으나, 압축압력 및 흡입공기의 역류로 인해 평균유효 압력과 출력의 감고를 수반하였다. 따라서 이에 대한 대책이 있어야 진정한 의미의 고팽창 디젤사이클이 실현되고 열효율향상 가능성이 있음이 확인되었다. 위와 같은 사이클을 실제기관으로부터 구현하기 위해 흡기밸브 닫힘시기를 늦게 하는 제어시스템을 구축하고, 시험을 위해서 S/B가 약 3인 저속 단기통 디젤기관에 가변밸브타이밍(VVT)시스템을 적용하여 성능을 평가하였다. 그 결과 시험기관의 밸브제어에는 큰 문제없는 것으로 평가되었다.

• 한국정밀공학회지
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• 제15권12호
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• pp.142-147
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• 1998

Developing robot hands with multi-degree-of-freedom is one of the topics that researchers have recently begun to improve the limitation by adding flexibility and dexterity. In this study, an articulated servo-pneumatic robot hand system with direct-drive joints has been developed whose main feature is the minimization of the dimension. The servo-pneumatic system is advantageous to fabricate a dexterous robot hand system due to the high torque-to-weight and torque-to-volume ratio. This enables the design of a finger joint with an integrated rotary vane type actuator which produces high output torque without reduction gears, being very robust. In order to control the servo-pneumatic finger joints, a miniature proportional valve that can be attached to the robot hand is required. In this paper, a flapper nozzle type 4/3-way proportional directional valve has been designed and tested. The experimental results show that the developed valve can control a finger joint satisfactorily without much vibratory joint movements and acoustic noises.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2001년도 유체기계 연구개발 발표회 논문집
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• pp.419-424
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• 2001

TCV(Temperature control valve by pressure compensation) controls temperature constantly, when it is sending steam or high temperature water to heating device of heat exchanger. For designing TCV, the ratio of piston and hole diameters is one of the important design parameters. Numerical analysis is carried out to elucidate the flow characteristics in the TCV with different port areas of cold and hot waters, using the k-$\epsilon$ turbulence model and Cartesian cut-cell method. Numerical results show that the exit flow rate is mainly affected by pressure distribution in the piston.

• 대한기계학회논문집A
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• 제33권6호
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• pp.568-572
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• 2009

We present a ternary microfluidic multiplexer unit, capable to address three flow channels using a pair of control lines with two different threshold pressure valves. The previous binary multiplexer unit addresses only two flow channels using a pair of control line with identical threshold pressure valves, thus addressing $2^{n/2}$ flow channels using n control lines. The present ternary multiplexer addressing three flow channels using a pair of control lines, however, is capable to address $3^{n/2}$ flow channels using n control lines with two different threshold pressure valves. In the experimental study, we characterized the threshold pressure and the response time of the valves used in the ternary multiplexer. From the experimental observation, we also verified that the present ternary multiplexer unit could be operated by two equivalent valve operating conditions: the different static pressures and dynamic pressures at different duty ratio. And then, $3{\times}3$ well array stacking ternary multiplexers in serial is addressed in cross and plus patterns, thus demonstrating the individual flow channel addressing capability of the ternary multiplexer. Thus, the present ternary multiplexer reduces the number of control lines for addressing flow channels, achieving the high well control efficiency required for simple and compact microfluidic systems.

• 자동차안전학회지
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• 제12권2호
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• pp.21-26
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• 2020

This paper presents an anti-lock braking system for commercial vehicles with pneumatic brake system by using slip ratio. By virtue of system reliability, most commercial vehicles adopt pneumatic brake system. However, pneumatic brake systems control is more difficult than hydraulic systems due to a longer time delay and the system nonlinearity. One of the major factors in generating braking forces is the wheel slip ratio. Accordingly, the proposed ABS strategy employs the slip ratio threshold-based valve on/off control. This threshold-based algorithm is simple but effective to control the pneumatic brake systems. The control performance of the proposed algorithm has been validated via simulation studies using MATLAB/Simulink and Trucksim. The results show ABS by using slip ratio reduces the braking distance and improves vehicle control.

• 한국추진공학회지
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• 제15권4호
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• pp.73-78
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• 2011

가스발생기 사이클 액체로켓 엔진의 보정이나 제어를 위해 제어밸브를 적용하는 경우 제어밸브의 고유유량특성을 제어 대상값인 추력이나 혼합비와 선형적인 관계를 가지도록 선정함으로써 제어를 간단하면서도 예측가능한 형태로 가져갈 수 있다. 이에 본 연구에서는 기존에 개발된 엔진 모드해석 프로그램을 응용하여 추력 제어밸브와 혼합비 제어밸브의 고유유량특성을 계산하기 위한 알고리즘을 제안하였으며, 제어밸브의 스로틀 각에 따른 민감도를 계산하였다. 계산된 제어밸브의 고유유량특성을 해외사례와 운용범위에서 그 곡선의 형태를 비교하여 결과의 타당성을 검토하였다.

• 한국분무공학회지
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• 제22권1호
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• pp.22-28
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• 2017

In this study, the effects of intake valve closing timing by using Cam-in-Cam system on combustion and emission characteristics for diesel engine were investigated under GT-POWER simulation environment. As a result, it was found that volumetric efficiency and effective compression ratio were decreased as the intake valve closing(IVC) timing is retarded due to its backflow effect. Also, we found that in-cylinder pressure, heat release rate and NOx emission were decreased as IVC timing was retarded. These show that the LIVC(late intake valve closing) can be effective to control AFR and mixing rate in diffusion combustion of diesel engine.

• 한국자동차공학회논문집
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• 제9권1호
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• pp.112-121
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• 2001

In this paper, an engine-CVT integrated control algorithm is suggested by considering the powertrain loss, inertia torque and the CVT ratio response lag. The integrated control algorithm consists of (1) the optimal engine power calculation and (2) determining of the optimal throttle valve opening and the optimal CVT ratio. The optimal engine power is obtained by compensating the inertia torque due to the CVT ratio change and the powertrain loss that is calculated iteration procedure. In addition, an algorithm to compensate the effect of the CVT ratio response lag on the drive torque is suggested by the engine speed compensation causing the increased optimal CVT ratio. Simulation results show that the engine-CVT integrated control algorithm developed in this study makes it possible to obtain better engine operation on the optimal operating line, which results in the improved fuel economy while satisfying the driver's demand.

• Journal of Mechanical Science and Technology
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• 제15권7호
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• pp.1061-1071
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• 2001

The present study investigated design parameters of shunt valves and anti-siphon device used to treat patients with hydrocephalus. The shunt valve controls drainage of cerebrospinal fluid (CSF) through passive deflection of a thin and small diaphragm. The anti-siphon device(ASD) is optionally connected to the valve to prevent overdrainage when the patients are in the standing position. The major design parameters influencing pressure-flow characteristics of the shunt valve were analyzed using ANSYS structural program. Experiments were performed on the commercially available valves and showed good agreements with the computer simulation. The results of the study indicated that predeflection of the shunt valve diaphragm is an important design parameter to determine the opening pressure of the valve. The predeflection was found to depend on the diaphragm tip height and could be adjusted by the diaphragm thickness and its elastic modulus. The major design parameters of the ASD were found to be the clearance (gap height) between the thin diaphragm and the flow orifice. Besides the gap height, the opening pressure of the ASD could be adjusted by the diaphragm thickness, its elastic modulus, area ratio of the diaphragm to the flow orifice. Based on the numerical simulation which considered the increased subcutaneous pressure introduced by the tissue capsule pressure on the implanted shunt valve system, optimum design parameters were proposed for the ASD.