• 대한의용생체공학회:의공학회지
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• 제16권1호
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• pp.61-66
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• 1995

We have developed a monoleaflet polymer valve as an inexpensive and viable alternative, especially for short-term use in the ventricular assist device or total artificial heart. The frame and leaflet of the polymer valve were made from polyurethane. To evaluate the hemodynamic performance of the polymer valve a comparative study of flow dynamics past a polymer valve and a St. Jude Medicals prosthetic valve under physiological pulsatile flow conditions in vitro was made. Comparisons between the valves were made on the transvalvular pressure drop, regurgitation volume and maximum valve opening area. The polymer valve showed smaller regurgitation volllme and transvalvular pressure drop compared to the mechanical valve at higher heart rate. The results showed that the functional characteristics of the polymer valve compared favorably with those of the mechanical valve at higher heart rate.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.509-513
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• 2004

There are a lot of efforts to improve noise and vibration in compressor. It had depended on experiments to reduce the annoying noise and vibration raised by costumer complaints until the twentieth century. But a trend of noise and vibration research changed tremendously by simulation techniques. Simulation techniques are also applied to fields on acoustic and valve dynamics etc, to validate a experiment and improve the performance of various fields in noise and vibration.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1992년도 춘계학술대회
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• pp.123-126
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• 1992

In this paper, a numerical simulation of steady laminar and turbulent flow in a two dimensional model for the total artificial heart is presented. A trileaflet polyurethane valve was simulated at the outflow orifice while the inflow orifice had a trileaflet or a flap valve. The numerical solutions of the simulated model show that regions of relative stasis and trapped vortices were smaller wi thin the ventricular chamber wi th the flap valve at the inflow orifice than that with the trileaflet valve. The predicted Reynolds stresses distal to the inflow valve within the ventricular chamber were also found to be smaller with the flap valve than with the trileaflet valve. Analysis of the numerical solutions suggests that geometries similar to the flap valve(or a tilting disc valve) results in a better flow dynamics within the total artificial heart chamber compared to a trileaflet valve.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제30회 추계학술대회
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• pp.318-322
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• 1999

An analytical study about dynamic behavior of center pivot rocker arm type valve train system equipped with roller of diesel engine is developed. At first, a mathematical model for the dynamic analysis has been set up using the lumped parameter method. In that model, valve spring is divided as some mass elemehts so as to simulate spring surging, Then, how the design parameters, such as valve mass, rocker arm inertia, valve spring stiffness, and initial load on valve spring, affect valve dynamic behavior especially in the valve close area is scrutinized.

• 대한의용생체공학회:의공학회지
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• 제10권2호
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• pp.91-93
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• 1989

We have developed a monoleaflet polymer valve as an inexpensive and viable alternative, especially for short-term use in the ventricular assist device or total artificial heart. The frame and leaflet of the polymer valve were made from polyurethane, To evaluate the hemodynamic performance of the polymer valve a comparative study of flow dynamics past a polymer valve and a St. Jude Medical prosthetic valve under physiological pulsatile flow conditions in vitro was made. Comparisons between the valves were made on the transvalvular pressure drop, regurgitation volume and maximum valve opening area. The polymer valve showed smaller regurgitation volume and transvalvular pressure drop compared to the mechanical valve at higher heart rate. The results showed that the functional characteristics of the polymer valve compared favorably with those of the mechanical valve at higher heart rate.

• 소음진동
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• 제3권2호
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• pp.163-167
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• 1993

Suction and discharge valves of special type refrigerant compressor are designed by finite element method for effective valve design development procedure. It is well known that valve dynamic characteristics, for example, the natural frequencies and vibration modes, are necessary for the computer simulation of compressor valve dynamics, the analysis of flow patterns, noise, impact stresses and their propagation phenomena. This paper has analysed the natural frequencies and vibration modes for the first three orders under the given special boundary conditions and the experiments are conducted by laser holography. And also stress distribution is analysed and experiment by strain gage is followed.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.1172-1177
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• 1993

Dynamic characteristics of a hydraulic power supply are studied theoretically and computationally. The transfer function between the supply pressure and the load flow is derived considering relief valve dynamics, accumulator dynamics, and flow line dynamics. Frequency responses and time responses are obtained in many conditions using the transfer function and nonlinear mathematical model respectively.

• International Journal of Automotive Technology
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• 제8권5호
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• pp.615-622
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• 2007

In this study, a Coupled Computational Fluid Dynamics(CFD) and Finite Element Analysis(FEA) method are used to predict and evaluate the performance of an automotive shock absorber. Averaged Navier-Stokes equations are solved by the SIMPLE method and the RNG $k-\varepsilon$ is used to model turbulence. CFD analysis is carried out for different intake valve deflections and piston velocities. The force exerted on the valve in each valve deflection is obtained. The valve deflection-force relationship is investigated by the FEA method. The force exerted on the valve in each piston velocity is obtained with a combination of CFD and FEA results. Numerical results are compared with the experimental data and have shown agreement. Dependence of valve deflection as a function of piston velocity is investigated. Effects of hydraulic oil temperature change on valve behavior are also studied.

• 대한기계학회논문집A
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• 제35권5호
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• pp.487-494
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• 2011

LNG / LNG-FPSO선박에 사용되는 안전밸브는 배관 시스템으로부터 유체를 방출하여 시스템의 압력을 일정하게 유지시키는데 중요한 역할을 한다. 이러한 안전밸브의 기능적 특성으로 인해 유출계수는 밸브의 성능 중 가장 큰 비중을 차지하며, 선급의 인정을 받기 위해서는 0.8이상의 유출계수가 요구되고 있다. 밸브 성능을 향상시키기 위해서 밸브 내부에서 발생하는 유동특성에 대한 정확한 이해가 필요함에도 불구하고 대부분의 밸브 설계의 경우 현장 작업자들의 경험과 실험에 의한 시행착오에 의존하고 있다. 본 논문에서는 안전밸브에 대한 유동해석을 통해 밸브 내부에 발생하는 압축성 유동현상을 고찰하였고, 실험과 해석에 의한 유출계수를 비교하여 유동해석의 타당성을 검증하였으며, 안전밸브를 지나는 공기의 질량유량을 예측하기 위한 유동해석 모델을 확립하였다.

• 한국정밀공학회지
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• 제20권10호
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• pp.105-111
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• 2003

ORVR filler neck check valve, which is one of the essential components of the vapor fuel control system, should diminish the evaporation by maintaining laminar fluid flow on refueling process. This study presents numerical. results of pressure and velocity distributions of the fluid flow in a ORVR filler neck check valve on refueling process. CFD-ACE+ has been employed for numerical analysis based on the information of experimental results of valve position as a function of inlet flow rate. No abrupt pressure change, which may causes vaporization of fuel, has been confirmed to take place on the concave surface of the valve spool. However, it is clear that some possibility exist at the mid-position of surface of valve spool and downstream according to the opening of valve.