• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.14-17
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• 2008

A poppet type shutoff valve under the pneumatic control has been adapted for the MOV (Main Oxidizer shutoff Valve) for KSLV (Korea Space Launch Vehicle). The MOV controls the supply of liquid oxygen into the combustion chamber just by opening and shutting operations. The poppet part of the poppet valves is usually connected with the piston, but on the other hand that of the MOV is separated and just contacted with the piston in order to secure the flexibility of the valve design. For the prevention of the collision with valve body by an undesirable movement of the piston part, it is necessary to evaluate the force during the valve closing. The analysis of the force balance of the MOV at the moment of the valve closing have been performed and some important design parameters for the force balance control have been introduced.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.5371-5376
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• 2013

The role of a main starting air valve is to supply compressed air to the diesel engine for starting the stopped diesel engine of a ship and cut off the air during normal operation. In this study, the main starting air valve with 80mm size was designed based on the developed valve with 50mm size. The concept design of the 80A main starting air valve was completed by using CATIA. Then, fluid analysis was performed to investigate the flow characteristics such as pressure and velocity distribution. Sequentially, structural analysis using FSI was performed. In this study, ANSYS CFX and ANSYS Workbench are utilized. The heavy weight of the body can deteriorate the strength performance of neighbor elements, leading to undesirable effect on flow characteristics. Thus, in this research, a lightweight design of the body was suggested satisfying strength requirement. The weight of the suggested design was reduced by 7kg, and the strength satisfied its requirement.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.1
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• pp.187-195
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• 2003

The performance of shock absorber is directly related to the car behaviour and performance, both for handling and ride comfort. The displacement sensitive shock absorber has two modes of damping force (i.e. soft and hard) according to the position of piston. In this study, a mathematical nonlinear dynamic model is introduced to predict the performance of displacement sensitive shock absorber. Especially in this paper, the transient zone is considered and the simulation result is well fit with experimental data. And the vehicle dynamic characteristic of displacement sensitive shock absorber is presented using quarter car simulation model. The simulation results of frequency response are compared with passive shock absorber.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.4
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• pp.683-692
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• 2002

The most important parameter for hydraulic active suspension system is to sustain desirable vehicle maneuvering stability and ride comfort without increasing power consumption. The performance of hydraulic active suspension system depends on damping force of body damping valve and piston damping valve. Hydraulic actuator design and damping valve parameter selection are essential and basic procedure to design hydraulic system. This paper is on computer simulation with use of mathematical model that was delivered from dynamic characteristic of hydraulic actuator, as know basic damping characteristics of hydraulic active suspension system. The aim of this paper is to select the system parameter that affect mainly hydraulic active suspension, and identify the validity on the system parameter selection.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.510-515
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• 1993

본 연구에서는 저속에서도 시스템의 자세 제어가 용이하게 하기 위하여 추진기 뒤에 제어판이 위치하도록 설계하였으며, 일반 서보 시스템과는 달리 무게와 공간 제약이 크고, 제어판 운동에 따른 외란 등록성의 변화가 심하므로 push-pull 형태의 소형, 고출력 편로드 복동 복수 실린더의 작동기를 설계하였다. 또한 일반적으로 서보밸브와 작동기는 일체형으로 설계되나 본 시스템의 공간상 심한 제약으로 인하여 서보밸브와 작동기를 분리하는 방법으로 구조설계를 하고 그 사이 유로는 매니폴드식으로 하여 동력전달을 하였다. 설계된 구동장치를 실제 정밀제작하여 실험을 수행하였으며, 시뮬레이션 결과와 실험에 의하여 얻어진 결과를 비교 분석하여 설계의 타당성 및 시스템의 성능을 검증하였다. 고속 수중운동체에 대하여 저속에서 자세제어를 용이하게 하고, 제한된 좁은 설치공간의 문제점을 해결하기 위하여 1) 추진기 후미에 독립된 4개의 상, 하, 좌, 우 제어판 설치 2) 서보밸브는 몸체에, 작동기는 Tail Tube에 분리 작동 설계 3) 소형의 편로드 복동 복수 실린더로 설계 구성된 유압식 구동장치는 시뮬레이션과 실험 결과를 통하여 시스템의 타당성을 입증하였다. 그러므로, 개발한 구동장치는 저속에서도 큰 제어력으로 자세 제어가 용이하기 때문에 얕은 수심에서 발사시 예상되는 위험 요소를 상다ㅇ 개선 시키므로써 운용범위의 다양화를 가져 올것으로 기대된다.

• Journal of the Korean Institute of Gas
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• v.11 no.2 s.35
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• pp.37-42
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• 2007

This paper presents the leakage safety of two O-rings, which are located at the rectangular groove between a valve body and a valve stem. The leakage safety analysis of 0-ring seals has been computed as functions of a compression set and a liquefied petroleum gas pressure of a LPG cylinder using a FEM program, MARC. The FEM computed results indicate that the loads from the filling pressure of $8kg/cm^2$ to the upper limit of the safety valve, $24.8kg/cm^2$ work safely according to the pressure vessel code. But two O-rings should consider the aging effects for an increased safety of the o-ring.

• Journal of the Korean Institute of Gas
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• v.21 no.4
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• pp.70-75
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• 2017

This paper presents the FEM analysis results on the deformation behavior safety of automatic cut-off horizontal and conventional vertical gas valves. Based on the FEM analysis, the primary maximum deformation of $4.4{\mu}m$ was formed on the right end side of a valve body when the internal gas pressure was supplied on the screw port and gas discharge port of an automatic cut-off horizontal gas valve. And the secondary maximum deformation of $2.9{\mu}m$ was formed on the end side of safety valve port. This small deformation of an automatic cut-off horizontal gas valve is strongly related to the balanced design of a horizontal gas valve main body, which is composed of a screw part, gas outlet port, port for a stem and spindle shaft assembly, and safety valve port. But, the primary maximum deformation of 0.076mm was formed on the upper part of a conventional automatic cut-off vertical gas valve when the internal gas pressure was supplied on the screw port and gas discharge port. And the secondary maximum deformation of 0.055mm was formed on the left end side of a gas outlet port. This may effect on the sealing clearance of o-ring that is inserted on the groove of an automatic cut-off unit. Thus, this paper recommends an automatic cut-off horizontal gas valve compared with that of a conventional gas valve for a gas leakage free mechanism of a LPG cylinder valve.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.7 s.250
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• pp.707-714
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• 2006

A numerical analysis study has performed in terms of fluid dynamics to identify the wall thinning generated in the main feedwater isolation valve body of a nuclear power plant. To review the relations between flow characteristics and the wall thinning induced by flow accelerated corrosion (FAC), numerical analysis using FLUENT code and ultrasonic tests (UT) were performed. The local velocities according to the analysis results were compared with the distribution of the measured wall thickness by ultrasonic tests. The comparison results show that the local velocity in the x-direction had no correlation with the wall thinning but the local velocity in the y-direction and turbulence intensity had a great influence on that. These results provide a good match to those of the previous studies - locations colliding vertically against components undergo severe wall thinning. These results may be utilized to the design modification and the wall thinning management for main feedwater isolation valves for preventing the wall thinning degradation.