• 한국유체기계학회 논문집
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• 제6권4호
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• pp.29-37
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• 2003

This study was undertaken to verify the effect of flow coefficient when a globe control valve was attached by different type of fitting. The valve flow coefficient is usually determined by measuring the flow rate and the pressure drop with the connection of straight pipe through the valve. The effect of different fitting that is mounted on the downstream of the valve is studied. Four types of fittings and three distances between the valve and a downstream fitting are compared parametrically to investigate the effect on the flow coefficient of it. Measured flow coefficient and numerically predicted value by using computational fluid dynamics were compared in detail. It is concluded that the flow coefficient is reduced if the fitting is attached after a valve, but the effect of different type of fitting is not crucial.

• 대한기계학회논문집B
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• 제32권1호
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• pp.39-46
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• 2008

The loss coefficient of the butterfly valve which allows partial opening of the valve at closed position and is applicable to the small-sized pipe system with the diameter of 1 inch was measured for the variation of the valve disk blockage ratio. Two different types of the valve disk configuration to adjust the blockage ratio were considered. One was the solid type valve disk of which the diameter was changed into the smaller size rather than the pipe diameter, and the other was the perforate type valve disk on which some holes were perforated. The results from two types of valve disk were compared to identify their characteristics in the loss coefficient distributions. The loss coefficient and the controllable angle of the valve disk were decreased exponentially with the decrease of the blockage ratio. In addition, the perforate valve disk had the effect on the higher loss coefficient rather than the solid type valve disk.

• 한국유체기계학회 논문집
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• 제10권5호
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• pp.46-53
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• 2007

Stem friction coefficient and valve factor are very important parameters for the evaluation of valve performance. In this study, the characteristics of stem friction coefficient and valve factor are analyzed, and thor bounding value is determined. The hydraulic testing is performed for many flexible wedge gate valves in the plant and statistical method is applied to the determination of bounding value. According to the results of this study, stem friction coefficient does not change much with differential pressure, and the bounding value of closing stroke is higher than that of opening stroke. The valve factor of valves with high differential pressure is higher than that of valves with medium differential pressure. It means valve factor is more sensitive to the differential pressure than the stem friction coefficient. Valve factor of the closing stroke is higher than that of opening stroke due to piston effect.

• 대한기계학회논문집B
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• 제23권2호
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• pp.166-174
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• 1999

The flow characteristics of 2-valve and 4-valve cylinder heads with various blocked-valve were experimentally investigated in a steady flow rig. Effects of the blocked-valve configurations on flow coefficient, swirl and tumble intensity are studied. Compared to the conventional valve, the blocked valve in both cylinder heads have the much lower flow coefficient and the much higher intensity of swirl and tumble. Under the same size of blockage, the value of flow coefficient and swirl(or tumble) intensity were varied according to the position of blockage. Throughout these steady flow test the optimized positions of blockage in both cylinder heads were determined.

• Journal of Advanced Marine Engineering and Technology
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• 제32권6호
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• pp.923-930
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• 2008

The butterfly valve is widely used in the industrial field as an on-off or a flow control valve. When the butterfly valve is used as a flow control valve. cavitation sometimes occurs in the range of high flow rate because of the small valve opening. Therefore. the pressure loss and the cavitation characteristics are investigated by use of a commercial CFD code. The results show that the possibility of cavitation occurrence in the cryogenic butterfly valve is very high in the case of valve opening angle below 10 degree and incident velocity over 6m/s. By increasing the inlet velocity at 10 degree of valve opening angle. the value of loss coefficient increased. However. by increasing the inlet velocity at 50 degree of valve opening angle. the value of loss coefficient decreased.

• 한국유체기계학회 논문집
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• 제14권5호
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• pp.39-47
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• 2011

Flow control range of valve, which is installed on pipeline, varies according to valve type, pipe diameter, pipe length, roughness, and elevation difference of both ends of pipeline. A lot of computation efforts and knowledge are needed to estimate flow control range of valve, considering above many parameters. The table of flow control range of each valve type is presented for convenience of pipeline design engineers who must make decision of valve size and type in this study. Also the reason that butterfly valve is recommended for flow control, and gate valve is forbidden is presented via quantification and figures in this study.

• 한국항공우주학회지
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• 제36권1호
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• pp.14-21
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• 2008

밸브 디스크 직경이 25.4 mm 인 소형 버터플라이밸브의 유동특성이 다양한 밸브 닫힘각에 대해 실험적으로 연구되었다. 밸브 디스크각이 작은 경우 유량조절특성을 향상시키기 위해 주어지는 밸브 닫힘각을 0$^{\circ}$, 5$^{\circ}$, 10$^{\circ}$, 20$^{\circ}$, 30$^{\circ}$로 변화시켜 밸브 디스크각에 따른 손실계수를 측정하였다. 또한 밸브선단 형상이 손실계수 변화에 미치는 영향을 조사하였다. 밸브 닫힘각이 증가함에 따라 최대손실계수는 감소하며, 밸브 닫힘각 0$^{\circ}$~5$^{\circ}$에서 가장 큰 감소를 나타냄을 알 수 있었다. 밸브 디스크 형상에 따른 손실계수는 밸브 닫힘각이 0$^{\circ}$인 경우 날카로운 모서리를 갖는 디스크가 더 큰 손실계수를 나타낸 반면, 닫힘각 10$^{\circ}$의 경우 날카로운 모서리를 갖는 디스크의 경우가 더 낮은 손실계수를 나타냄을 알 수 있었다.

• 한국화재소방학회논문지
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• 제21권3호
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• pp.91-96
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• 2007

수계소화시스템 버터플라이 밸브의 성능해석에 대한 연구를 수행하였다. 버터플라이 밸브의 성능해석으로는 토크특성, 압력손실과 캐비테이션을 고찰하였다. 밸브의 토크특성은 토크 이론식에 밸브 디스크의 개도각이 보정되었고, 보정식이 추가되었다. 밸브의 열림각에 대한 압력손실계수는 Carnot 방정식을 응용하여 수식화하였다. 버터플라이 밸브의 토크특성, 압력손실과 캐비테이션은 디스크의 두께와 직경 비에 대해 해석하였다. 캐비테이션은 밸브의 압력손실계수로부터 해석하였다. 압력손실과 캐비테이션 해석은 밸브의 열림각에 대한 두께 비의 변화에 따라 수행하였다. 이들 해석 데이터는 버터플라이 밸브를 개발하는데 필요한 엔지니어링 데이터로 활용하고자 한다.

• 동력기계공학회지
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• 제20권1호
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• pp.5-10
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• 2016

Swing check valve is opened when the flow direction is forward, when the flow is reversed, the valve is automatically closed by back pressure. In this study, the internal flow field analysis of the valve was conducted by Fluent. The working fluid used in the study, using liquefied methane $-165^{\circ}C$ (CH4) and velocity field, pressure field, pressure drop coefficient were simulated by varying separately the opening divergence into four intervals from 0 to 100%. The approximate research result are as follow : When the opening divergence is smaller, it appears high pressure on the upstream side, this value is relaxed when the opening divergence is large. Flow rate coefficient of the valve shows a larger value as the degree of opening becomes larger, confirming that the check valve used in the study is in the effective flow rate counting range.

• 한국정밀공학회지
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• 제17권2호
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• pp.151-160
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• 2000

An experimental and theoretical analysis for the improvement of dynamic characteristics and design of electro-hydraulic flow control servo valve are performed. The theoretical results are compared with the experimental step responses, and the important design parameters of an electro-hydraulic flow control servo valve are derived by using the simulation program. Simulation parameters of nozzle jet coefficient and orifice and spool valve discharge coefficient are given through experiment. The theoretical and experimental step response curves show that the valve gain depends on the fixed orifice and nozzle $ratio(R_on)$ and is maximum at $R_on=1.$ And drain orifice in the flapper - nozzle return line creates a small back pressure, which improves the performance fur the valve.