• Journal of the Korean Magnetics Society
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• v.7 no.6
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• pp.321-326
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• 1997

We analyzed an important part of control valve, magnet unit, which is used to control the fluid. Magnetic circuit which is composed of magnet and yoke is analyzed using finite element method. Then, flux density and coil force were calculated and compared with those of measured. According to the simulation results, the gap field, force constant, and permeance coefficient were 3~5 kG, 27.5 N/A, 22.1, respectively, which corresponded reasonably well with the measured values. We also obtained reluctance factor of 1.1 and fringing factor of 1.4 by simulation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.488-491
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• 1997

In this paper, a ncw control 'ialvc which can misc air-iraksge pneumatically and compensate pressure drop for an alrho~ st system uas proposed A new control valve called "Pneuniatic C70ntro1 Valve (PCV)" functions as a control valve to compcns;ltc prcssure in thc casc of air-leakage. by using the pure pneummatic control ofpilot pressure. Based on the sirnulation of the proposed PCY, thc experimental system was fabricaied su as to illustrate the efficient pcrformance of the proposed PCV with anti-leakage. Such good perfo~manccs of PCV in the air-hoist system are shown by the simulation. In addition, the simulation bascd design approach presented in this paper can be applied to any hydraulic or pneumatic-hydraulic system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.1
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• pp.81-86
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• 2016

The valves used to control or shut off the flow through a pipeline can be divided into many different types, including gate valves, globe valves, and check valves. Globe valves, in particular, have excellent properties, and because they can easily control the flow under high-pressure conditions, they are generally used in LNG ship and steam pipelines. In this paper, a method for changing the shape of a seat was suggested to solve the valve leakage problem from a structural perspective. In addition, the stress distribution and directional deformation were compared for each model. The suggested models were thus validated, and the optimized seat structure, which includes a self-supporting capability for decreasing the amount of leakage, was determined.

• Journal of Aerospace System Engineering
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• v.12 no.5
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• pp.54-68
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• 2018

The objective of this study is to analyze the effect of dynamic characteristics of the check valve applied to the small piezoelectric-hydraulic pumps on flow rate formation. The flow rate of the piezoelectric-hydraulic pump is a key factor in the formation of the load pressure to operate the brake system. At this time, the natural frequency of the check valve operating in the fluid has a great influence on the formulation of the flow rate of the piezoelectric-hydraulic pump. In addition, the natural frequency of the check valve is affected by the gap between the check valve and the pump seat. In this study, the natural frequency of the check valve according to the gap between the check valve and the pump seat was calculated through the fluid-structure interaction analysis. The flow rate obtained from the simulation result was verified by comparing it with the result from the flow rate experiment using the developed piezoelectric-hydraulic pump.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.7-7
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• 2019

중요한 사회기반시설물 중 하나인 상수관망시스템은 대부분의 시설물이 지중에 매설되어있기 때문에 지진에 취약하고 복구에 어려움이 크며, 지진 발생 시 대규모 피해로 이어질 우려가 있다. 따라서 상수관망시스템에 대한 지진피해를 최소화하고 재해로부터 신속하게 복구하기 위한 적절한 복구전략을 마련할 필요가 있다. 상수관로에 발생하는 지진피해는 크게 파손과 누수로 구분되며, 대구경 관로가 파손될 경우 대규모 단수 및 피해가 우려되므로 신속한 복구전략이 마련되어야한다. 일반적으로 파손 관로의 복구는 먼저 피해 관로 인근의 제수밸브의 차폐를 통해 통수를 차단한 후 교체 작업을 진행하는 것이 일반적이며, 해당 과정에서 밸브 차폐에 의한 단수구역의 발생이 불가피하다. 이러한 단수구역 발생은 해당 지역의 용수공급능력 저하로 이어지며, 단수구역의 범위 및 단수용량의 규모는 제수밸브의 위치 및 개수에 따라 결정된다. 본 연구에서는 기개발된 상수관망 지진피해복구 시뮬레이션 모형(Choi et al., 2018)을 개선하여 지진피해복구 시 시스템 내 제수밸브의 설치 위치와 개수에 따라 발생되는 단수구역과 단수상황이 상수관로의 용수공급능력(Serviceability)에 미치는 영향을 분석하였다. 개선된 모형은 피해복구에 따른 용수공급능력을 정량적으로 산정할 수 있으며, 피해 관로의 복구 시 제수밸브 차폐에 의해 발생되는 단수구역을 탐색한 후, 수리해석 모의에 적용함으로써 현실적인 용수공급 상황을 모의할 수 있도록 개선되었다. 또한, EPANET3.0의 Full-PDA(Pressure driven analysis)를 이용함으로써 지진과 같은 비정상상황(다수관의 파손에 따른 압력저하)에서 좀 더 현실적인 수리해석이 가능하도록 개선되었다. 본 연구에서는 해당모형을 실제관망에 적용하여 제수밸브 설치개수 및 위치가 지진피해복구에 미치는 영향을 비교 분석하였으며, 또한 효율적인 지진피해복구 방안을 제시하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.641-642
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• 2008

• Journal of Aerospace System Engineering
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• v.12 no.2
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• pp.7-14
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• 2018

In this study, a new check valve was studied to improve the load pressure of a brake system with a small piezoelectric-hydraulic pump. During the pressurization process, the steady-state pressure at the load is affected by the ratio of the cross-sectional area of the check valve the chamber pressure and load pressure. Since the flow path cover of the check valve is made wider than the cross-sectional area of the output flow to prevent backflow, a method of reducing the area ratio is proposed for a higher load pressure by mounting an additional mass to a thin plate spring type check valve. To identify the effect of mounting an additional mass to the existing check valve on the load pressure, a simple brake system with a small piezoelectric-hydraulic pump was modeled using a commercial code AMESim. The AMESim modeling was verified by comparing the simulation results with the experimental results of the pump the existing check valve. The additional mass was added to the verified AMESim modeling and higher load pressure was able to be obtained through simulation. The 35% performance improvement in load pressure identified by carrying out pressurization test of the brake system after adopting the new check valve the small piezoelectric-hydraulic pump.

• Journal of the Korea Society for Simulation
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• v.22 no.3
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• pp.81-87
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• 2013

This paper is about study how to decrese surge pressure that is occurred in excavator driving motor. We used computer simulation program SimulationX. It is also about the way finding design problem and approaching a solution through interpreting shape design sensitivity analysis. Programmes are below. First of all, finding shape fault by analyzing dynamic behavior of valves installed in hydraulic driving motor which is designed now. And drawing variable which is considered sensitive to improve dynamic efficiency among a lot of shape variables. Then, targeting that variable and examining dynamic efficiency stabilization tendency with controlling it. Finally, suggesting the most effective tuning method through variable combination as there are a lot of sensitive variables.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.500-507
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• 1989

The improvement of volumetric efficiency of air charging into combustion chamber is a primary requirement to obtain better mean effective pressure of an engine. Since parameters such as the air resistances in intake and exhaust flow passages, valve lift and valve timing influence greatly to the volumetric efficiency, it is very convenient and time saving if we can optimize these parameters by computation before we enter into long time fact finding engine tests. In this study we have developed a semi-empirical engine simulation program for the determinations of intake and exhaust valve timings, valve lifts, intake and exhaust port diameters in order to obtain highest volumetric efficiency. In this computation it requires only the measured variational pressures in intake and exhaust port. Using these variational pressures as an input data for our simulation program, we can calculate volumetric efficiency more accurately and can save computing time drastically. To confirm the validity of our simulation program we have made engine operation test in parallel and taken the experimental data. Comparing the computation result with the experimental data obtained through real engine test it has shown only the difference of 3%.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.1
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• pp.51-58
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• 2002

A simulation model has been developed to predict the performance of 5-valve gasoline engine by gas exchange process with combustion model. In this study, we simulated the intake flow characteristics and performance of 5-valve engine with entwine speed and we compared the 5-valve engine performance with that of 4-valve engine. As a result. the calculated value was in consistency with the measured value relatively. The performance of 5-valve engine was higher than that of 4-valve engine in high engine speed region.