• Journal of Advanced Marine Engineering and Technology
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• 제35권4호
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• pp.443-450
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• 2011

연료가스 압축 시스템은 중급의 FPSO에 설치되며, 이 시스템에서 서지를 방지하기 위하여 안티 서지 밸브가 사용되어진다. 만약 서지가 발생하게 되면 시스템의 파괴를 초래할 수 있으므로 안티서지 밸브는 반드시 구조강도와 구조안전성 평가가 수반되어야한다. 특히, 비상시에도 밸브는 구조안전성과 그 성능을 보장해야 된다. 이 연구에서는 안티서지 밸브의 구조강도와 구조안정성 평가를 수치해석을 통하여 수행하였다. 형상모델은 유니그래픽스 NX4.0을 사용하였으며 시뮬레이션은 ANSYS Workbench 12.1 버전을 이용하였다. 밸브의 허용 강도와 안전계수는 ASME Boiler & Pressure Vessel Code를 참조하였다.

• 한국정밀공학회지
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• 제34권2호
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• pp.145-150
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• 2017

Air brake valves are widely used in automotive braking systems and the Korean automobile industry depends on importing them. Therefore, we should develop the technical expertise for their domestic production. In this study, air brake valves were analyzed that can be used in a variety of automobiles. Computational fluid dynamics analysis, static structural analysis, and hyper-elastic analysis were carried out. Before production of an air brake valve system, the performance of different parts has to be evaluated, for instance by using finite element analysis. The structural stability of the product can be determined using static dynamics. The compression behavior of the O-ring is predictable by nonlinear hyper elastic analysis, although errors are possible due to one-way loading. This simulation study can both save time and reduce costs compared to the development of experimental prototypes.

• 소성∙가공
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• 제22권8호
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• pp.442-449
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• 2013

The solenoid valve case of an 8-speed automatic transmission plays a role in maintaining the valve seal, which prevents an inflow of foreign substances into the transmission. The seal increases the reliability of the automatic transmission's performance. As a solution to pollution-related problems and to reduce fuel consumption, transmissions are being made with more gears to work more economically and have reduced fuel consumption. These newer transmission require greater dimensional tolerances and need to be manufactured with more precision. In the current study, the design of a multistage drawing considering both the product's height and limit draw ratio (LDR) of the material was performed using both a theoretical analysis and the expertise of industrial experts. The finite element modeling (FEM) simulation was performed using the commercial software, PAM-stamp, and tests of the dimensional measurements for a prototype were performed to verify the optimal progressive process.

• 한국정밀공학회지
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• 제13권6호
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• pp.102-113
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• 1996

An experimental and theoretical study on a pneumatic servo system has been conducted using on-off valves and a pneumatic cylinder. A V/I converter has been designed for rapid rising and falling of the solenoid current, which significantly improves the positioning accuracy and settling time of the servo system by shortening the valve opening time. Pulse width modulation was modified to operate on-off valves effectively. A state feedback controller which feeds back position, velocity and acceleration is used to control the system. The influence of controller gains on the system performance is studied to develop a scheme that automatically adjusts the gains using fuzzy logic theory. It is shown experimentally that the proposed fuzzy logic tuner works satisfactorily. A new method for measurements of valve effective areas is proposed, and a partially polytropic model is applied to simulation of the pneumatic system. Simulated results show good agreement with experimental data.

• 한국자동차공학회논문집
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• 제24권1호
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• pp.47-52
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• 2016

Miller timing is one of the promising ways which can improve the fuel consumption of internal combustion engines. Indeed, Miller timing employing an early intake valve close is widely applied to large diesel and gas engines to enhance performance and reduce NOx emissions. In this study, performance evaluation is carried out by 1-D cycle simulation in order to estimate the effect of Miller CAM timing before BDC for a 32 L turbocharged diesel engine. To optimize Miller CAM timing, a single stage turbocharger is matched with an early intake valve close since boost pressure is a significant parameter that can control compression work in a turbocharged engine. The engine simulation result shows that there is enough potential to improve fuel consumption rate and also reduce NOx emissions at the same time.Abstract here.

• 한국가스학회지
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• 제6권1호
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• pp.74-80
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• 2002

지하공간에서 천연가스가 고압으로 분출될 때, 이에 응하여 작동되는 환기시스템이 전체 지하공간 내 유동에 미치는 영향은 매우 크며 이에 대한 적정한 선계는 안전성 확보측면에서 매우 중요한 일이다. 본 연구에서는 천연가스 분출 비상시의 유동을 전산해석을 통하여 반밀폐공간 내 천연가스의 농도분포 및 유동특성을 규명함으로써, 내부유동을 가시화하고 상부 환기팬 유$\cdot$무에 따른 환기효율을 비교함으로써 환기시스템의 개선사항 및 설계 방안을 제시하였다.

• 설비공학논문집
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• 제20권6호
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• pp.365-371
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• 2008

Condensing gas boiler units may make a big role for the reduction of energy consumption in heating industries. In order to decrease the energy consumption of a condensing gas boiler unit, effective operations of the system are necessary. In this study, mathematical models of a condensing gas boiler system were developed in order to develop control algorithms of the system. These include dynamic models of a blower, a gas valve, a pump, a burner, a boiler heat exchanger, and a hot water heat exchanger. Control algorithms of a blower, a gas valve, and a pump were also assumed. Simulation results showed good predictions of dynamic behaviors of a boiler system. Therefore, the simulation program developed for this study may be effectively used for the development of control algorithms of a boiler system.

• Nuclear Engineering and Technology
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• 제55권8호
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• pp.3088-3101
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• 2023

A pressurized vessel-pipe-safety valve (PVPSV) combination is a commonly used configuration in nuclear power plants, and a good numerical model is essential for the system design, sizing and performance optimization. However, owing to the large-scale and cross-scale features, it is still a challenge to build a system level numerical model with both high accuracy and efficiency. To overcome this, a novel system level modeling method which can synthesize the advantages of various models is proposed in this paper. For system modeling, the analytical approach, the method of characteristics (MOC) and the surrogate model approach are respectively adopted to predict the dynamics of the pressure vessel, the connecting pipe and the safety valve, and different models are connected through data interfaces. With this system model, dynamic simulations were carried out and both the stable and the unstable system responses were obtained. For the model verification purpose, the simulation results were compared with those obtained from experiments and full CFD simulations. A good agreement and a better efficiency were obtained, verifying the ability of the model and the feasibility of the modeling method proposed in this paper.

• 한국정밀공학회지
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• 제25권6호
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• pp.108-115
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• 2008

The wear on engine valve and seat insert is one of the most important factors affecting engine performance. The engine valve and seat insert must be able to withstand the severe environment that is created by: high temperature exhaust gases generated while the engine is running, rapid movement of the valve spring, high pressure generated in the explosive process. In order to study such problems, a simulator has been developed to generate and control high temperatures and various speeds during motion. The wear simulator is considered to be a valid simulation of the engine valve and seat insert wear process with various speeds during engine activity. This work focused on the test of various degrees of wear on four different exhaust valve materials such as HRV40, HRV40-FNV (face nitrided valve), STL #32, STL #6,. Throughout all tests performed in this study, the outer surface temperature of the seat insert was controlled at $350^{\circ}C$, the cycle number was $4.0{\times}10^6$, the test load was 6860 N, the fuel was LPG the test speed was 20 Hz (2400 RPM) and the seat insert material was HVS1-2. The mean (standard deviation) maximum roughness of the exhaust valve and seat insert was $25.44\;(3.16)\;{\mu}m$ and $27.53\;(3.60)\;{\mu}m$ at the HRV40, $21.58\;(2.38)\;{\mu}m$ and $25.94\;(3.07)\;{\mu}m$ at the HRV40-FNV, $36.73\;(8.98)\;{\mu}m$ and $61.38\;(7.84)\;{\mu}m$ at the STL #32, $73.64\;(23.80)\;{\mu}m$ and $60.80\;(13.49)\;{\mu}m$ at the STL #6, respectively. It was discovered that the maximum roughness of exhaust valve was lower as the high temperature hardness of the valve material was higher under the same test conditions such as temperature, test speed, cycle number, test load and seat insert material. The set of the HRV40-FNV exhaust valve and the HVS1-2 seat insert showed the best wear resistance.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 B
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• pp.809-811
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• 1999

The three-mode PID controller is widely used in plant because control algorithm is simple and tuning method is general. But the conventional PID controller can not have the both purpose of setpoint tracking and disturbance rejection at the same time. In this paper, we studied the application 2DOF PID controller to pneumatic control valve through simulation and experiments. Results are Presented a satisfactory response