• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.946-949
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• 2003

This paper reports on the fluid flow simulation results of a multilayer type piezoelectric valve. The mechanical and fluidic analysis are done by finite element method. The designed structure is normally closed type using buckling effect, which is consist of three separate structures; a valve seat die, an actuator die and a MLCA(Multilayer Type Ceramic Actuator). It is confirmed that the complete laminar flow and the lowest flow leakage are strongly depend on the valve seat geometry. In addition, turbulent flow was occurs in valve outlet according to increase seat dimension, height and inlet pressure. From this, we was deducts the optimum geometry of the valve seat and diaphragm deflection that have an great influence fluid flow in valve. Thus, it is expected that our simulation results would be apply for piezoelectric applications such as valve and pump, fluidic control systems.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.5
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• pp.525-533
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• 2022

In this study, in order to numerically analyze the heat flow characteristics in the valve according to the opening rate for the solenoid valve for hydrogen supply applied to the hydrogen storage tank, flow characteristics were comparatively analyzed. Through the analysis of pressure and temperature distributions within the valve according to the high-pressure supply condition of 70 MPa or more, the heat flow characteristics in the valve, inlet and outlet passage according to the opening rate of the valve were identified. As a result a sudden change in the fluid behavior appears in the neck region of the valve, and it is understood that the flow separation caused by the flow path shape of the expanded tube has a dominant influence on the flow characteristics. And, it was confirmed that the shape of the valve seat is a factor significantly affecting the improvement of flow rate and differential pressure performance.

• Journal of Chest Surgery
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• v.24 no.3
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• pp.310-321
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• 1991

Between April 1986 and September 1990, 34 patients with a single or dominant right ventricle underwent modified Fontan procedure for definite palliation in Seoul National University Children`s Hospital. Their age at operation ranged from 8 months to 14 years [Mean 5.5 years]. The ventricular chamber was solitary and of indeterminate trabecular pattern in 6 patients. 28 patients had posteriorly located rudimentary chamber, all of which were trabecular pouches having no communication with outlet septum. The patterns of atrioventricular connection were common inlet[9], double inlet [11], left atrioventricular valve atresia [12] and right atrioventricular valve atresia with L-loop [2]. Pulmonary outflow tracts were atretic in 7 patients and stenotic in 26 patients. Major associated anomalies included anomalous systemic venous drainage [15], dextrocardia [12] and total anomalous pulmonary venous connection[3]. Shunt operations were previously performed in 13 patients and pulmonary artery banding and atrial septectomy in 1 patients. Surgery included intraatrial baffling in 26 patients, bidirectional cavopulmonary shunt in 13 patients, atrioventricular valve obliteration in 3 patients and atrioventricular valve replacement in 3 patients. Central venous pressure measured postoperatively at intensive care unit ranged from 18cm H2O to 28cm H2O [mean 23.2cm H2O]. Hospital mortality was 35.3% [12/34], all died out of low output syndrome. Suspected causes of low output syndrome include ventricular dysfunction [8], hypoplastic or tortuous pulmonary artery [2] and elevated pulmonary vascular resistance [2]. 19 patients had 31 major complications including low output syndrome [18], arrhythmia [4], acute renal failure [3] and respiratory failure [3]. Mortality rate was significantly higher in the groups receiving intraatrial baffling and AV valve replacement respectively [p<0.05]. 20 patients were followed up postoperatively with the mean follow-up period 15.0$\pm$11.6 months. There were no late death and follow-up catheterization was performed in 10 patients. Mean right atrial pressure was 15.4$\pm$6.8mmHg and ventricular contraction was reasonable in all but one case. Thus, Fontan principle can be applied successfully to all the patients with complex cardiac anomaly of single ventricle variety and better results can be anticipated with judicious selection of patient and improvement of postoperative care.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.3
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• pp.49-55
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• 2014

This paper examines the effects of spring characteristics and stiffness in relation to the characteristics of hydrodynamic force. Spring forces and stiffness determine the performance of this type of pan check valve and have an effect on the overall operation. The hydraulic efficiency of the pan check valve is relatively low compared to that of a common check valve. However, a pan check valve is structurally more stable than a common check valve. We implemented the optimum design to increase the flow rate and to resolve the suppression of the pressure drop according to the extent of the compression of the spring. From the results of a flow analysis, we demonstrate spring stiffness design criteria depending on the extent of the compression of the spring of pan check valve acting on the fluid at the inlet 1 MPa pressure.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.2
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• pp.103-108
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• 2014

Growing concerns about environmental pollution have led to an increase in the demand for compressed natural gas (CNG) vehicles in recent years. CNG vehicles are equipped with a cylinder valve installed in a high-pressure vessel to control the CNG flow. The cylinder valve must meet high quality safety standards because the pressure vessel stores high-pressure CNG. Therefore, safety evaluation of the cylinder valve is necessary to ensure the safety of CNG vehicles. In this study, fluid-structure interaction analysis for the structural integrity of the cylinder valve were conducted using a commercial finite element analysis code(ANSYS WORKBENCH V14). The CFD analysis was performed using a steady-state technique according to the inlet and outlet pressures in order to predict the pressure distribution. Structural analysis was performed by a static structure technique at the maximum working pressure to evaluate the structural integrity of the cylinder valve. From the results, the safety factor of the valve component is between 1.57 and 21.5.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1476-1477
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• 2008

This paper reports on a flexible flap valve actuated by electromagnetic force under a constant pressure source. The flexible flap valve consists of the three main components: a flexible flap with a steel disk embedded in PDMS, an electromagnetic actuator and two glass plates with inlet and outlet. Sealing lip structures for improving the valve characteristics are added on the outlet of the bottom glass substrate. The flap valve is fabricated by the spin-coating process, the EDM process, SU-8 mold process and oxygen plasma treatment. The dimension of an assembled flap valve is $12mm{\times}20mm{\times}28mm$. The stroke volume of the flap valve is measured for various pressures and open times. When the input voltage of 30 V is applied for 0.33 s, the minimum stroke volume of the flap valve is 70 ${\mu}L$ at 50 kPa.

• Journal of Drive and Control
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• v.12 no.4
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• pp.48-53
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• 2015

This paper deals with the flow characteristics of a reed valve analyzed using computational dynamics(CFD) for optimal design. The seat sizes of the valve are modeled asØ6[mm] and Ø8[mm] to compare the flow characteristics. The inlet boundary condition is entered at 10[kPa], 15[kPa], 20[kPa], and 30[kPa] and the outlet boundary condition is set to the atmospheric pressure. The flow coefficient(C) and pressure loss coefficient(K) are calculated from the results of flow analysis. From the analysis results, it was confirmed that the flow coefficient of a reed valve having a seat size of Ø6[mm] is greater than that having a seat size of Ø8[mm], and the coefficient of pressure loss of a valve with a seat size of Ø6[mm] is lower than the Ø8[mm] size valve.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.1
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• pp.10-17
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• 2007

For the purpose of optimal control of anti-lock brake system, precise dynamic characteristics analysis of the hydraulic modulator, especially solenoid valve is necessary. However, most of researches so law have dealt with dynamic characteristic analysis of valve itself and the results have been restrictive to apply on the actual ABS modulator, where hydraulic pressure is acting. In this study, mathematical modeling and experimental analysis were executed in order to evaluate the valve dynamic characteristics when the hydraulic pressure applied. High pressure on the master cylinder effects on the valve dynamic characteristics have been analyzed quantitatively and performance improvement methods have been suggested varying the design factor. Consequently, results of solenoid valve dynamic characteristics analysis derived in the study can be utilized criteria for the optimal control of anti-lock brake system.

• Journal of the korean Society of Automotive Engineers
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• v.12 no.3
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• pp.30-40
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• 1990

The computer program for the prediction of the volumetric efficiency of 4-cycle single cylinder diesel engine was developed using the characteristic method which considers the effects of friction, heat transfer and specific heat. The results of calculation by this program are as follows; 1. The back flowing was arised at the beginning and the closing stage of inlet valve, and the back flowing mass and velocity decrease as the engine speed increases. 2. The volumetric efficiency varies with the engine speed and the length of inlet manifold. There was an optimum length of inlet manifold for each specified engine speed. 3. The pressure fluctuation and friction effect in the inlet manifold became very important factors for the determination of the volumetric efficiency.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.3
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• pp.501-511
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• 1995

A numerical model for predicting the performance of gas distrubutor type double inlet pulse tube refrigerators has been developed. The model was based on adiabatic analysis and the losses of heat exchangers and regenerator were considered. Thermodynamic behavior of working fluid within a double inlet pulse tube refrigerator was investigated and the effects of design parameters, such as valve and orifice openings, cold heat exchanger temperature, frequency and pulse tube length, on the cooling capacity and COP were shown.