• Journal of the Korean Society of Marine Environment & Safety
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• v.5 no.2
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• pp.113-123
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• 1999

The aim of this paper was to expand on work already carried out on the modelling of the flow through a poppet valve using CFD software FLUENT V4.22. Several different models were run on FLUENT for various lifts of the poppet cone and various back pressures. The results for pressure and velocity obtained were interpreted. The results revealed the presence of cavitation downstream of the orifice around the cone tip, and the presence of a high velocity jet stream along the centre line. These results confirm what has been found to happen in practice.

• PNF and Movement
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• v.20 no.3
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• pp.431-441
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• 2022

Purpose: The purpose of this study was to compare the changes in the contact area, maximum pressure, maximum mean pressure, and maximum force of functional insoles and general insoles when walking. Methods: Foot pressure was measured by the ignition of functional insoles and general insoles on Company N shoes. The foot pressure was measured using a precision pressure distribution meter (Pedar - X mobile system, Novel, Germany). Each insole sensor contained 99 independent cells and was inserted between the foot and the shoe. A wireless Bluetooth-type program was used to measure the pressure detected by the measuring insoles. In order to eliminate adaptation and fatigue caused by wearing the guide during the experiment, sufficient rest was taken between each experiment, and the wearing order was randomly selected. Results: Functional insole significantly increased the forefoot and midfoot (medial, lateral) (p<0.05), while total foot, forefoot, and rearfoot peak pressure significantly decreased (p < 0.05) compared to the general insole. Conclusion: In the functional insole, a high contact area was measured inside, even in the middle of the foot, leading to a proper change in foot pressure. It was confirmed that the contact area was reduced and dispersion occurred well. In addition, it was found that the maximum pressure in the front and back of the entire foot was reduced, so the weight pressure dispersion in the functional insole was evenly distributed, and the maximum average pressure change was similar.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.2
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• pp.219-225
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• 2018

This study was carried out to investigate the injection characteristics of 800 kPa compressed natural gas compressed natural gas (CNG) injector developed in Korea. The CNG injector with multi-holes, employed in this experiment, was designed to inject CNG in the manifold at high pressure of 800 kPa. The spray macroscopic visualization test was carried out via Schlieren photography to study fuel-air mixing process. The fundamental spray characteristics, such as spray penetration, spray cone angle and spray velocity, were evaluated in the constant volume combustion chamber (CVCC) with varying the constant back pressure in CVCC from 0 to 1.8 bar. For the safety reason, nitrogen ($N_2$) and an acetone tracer were utilized as a surrogate gas fuel instead of CNG. The surrogate gas fuel pressures were controlled at 3, 5.5, and 8 bar, respectively. Injection durations were set at 5 ms throughout the experiment. The simulating events of the low engine speed were arranged at 1,000 rpm. The spray images were recorded by using a high-speed camera with a frame rate of 10,000 f/s at $512{\times}256pixels$. The spray characteristics were analyzed by using the image processing (Matlab). The results showed the significant difference that higher injection pressure had more effect on the spray shape than the lower injection pressure. When the injection pressure was increased, the longer spray penetration occurred. Moreover, the linear relation between speed and time are dependent on the injection pressure as well.

• Journal of the Society of Disaster Information
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• v.18 no.2
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• pp.241-251
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• 2022

Purpose: In the event of a fire in a high-rise building, if the smoke control area is not effectively protected, smoke or flames enter the stairwell, making it difficult to evacuate. When inflowing air is discharged from a closed corridor, a negative pressure is formed in the corridor, the pressure in the smoke control area becomes excessively high, and the force required to open the door during evacuation is exceeded. Also, if the air introduced into the hallway is not exhausted, the smoke may flow back into the smoke control area. This paper tried to identify the problems caused by the inflowing air and to find out how to improve the performance. Method: Using the CONTAM program, simulations were performed with the basic conditions and the modified conditions. Result: If the inflowing air was discharged from the sealed corridor, overpressure occurred in the Smoke Control Area and exceeded the opening force, and the prevent smoke backflow was insufficient in the layer where the inflowing air was not discharged. Conclusion: "Differential pressure exhaust damper" application, simultaneous opening of two exhaust dampers, and automatic window installation between corridors and outdoors improved the exhaust performance of inflowing air.

• Membrane Journal
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• v.16 no.1
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• pp.31-38
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• 2006

The ceramic microfiltration system with periodic $N_2$-back-flushing was operated for treating paper wastewater discharged from a company making toilet papers by recycling milk or juice cartons. Two kinds of alumina membranes with 7 channels used here for recycling paper wastewater. The optimal filtration time interval for HC04 membrane with $0.4{\mu}m$ pore size was lower value of 4 min than 16 min for HC10 with $1.0{\mu}m$ pore size at fixed back-flushing time 40 sec, trans-membrane pressure $1.0kg_f/cm^2$ and back-flushing pressure $5.0kg_f/cm^2$. From the results of TMP effect at fixed filtration time interval and back-flushing time, the lower TMP was better on membrane fouling because high TMP could make easily membrane cake and fouling inside membrane structure. However, we could acquire the highest volume of total permeate at the highest TMP for the reason that TMP was driving force in our filtration system to treat paper wastewater. Then the permeate water of low turbidity was acquired in our microfiltration system using multi channels ceramic membranes, and the treated water could be reused in paper process.

• Journal of Advanced Marine Engineering and Technology
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• v.11 no.4
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• pp.50-58
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• 1987

At present it has been cleared that even carefully polished surfaces have irregularities on them which are large compared with molecular dimensions by the progress of a scanning electron microscope. When two solids are placed together, the real area of contact is very small, so that the local pressure is high and, in general, exceeds the yield pressure of the metal. Plastic flow of the solid occurs at the summits of the irregularities so that the real area of contact is proportional to the applied load. There is adhesion at local resions of contact and the friction is, in a large measure, the force required to shear them. On this view point, the friction experiment with different specimens which are carbon steel, copper and constantan was attempted to know the characteristics of temperature change in contact with different metals. Various experiments are summerized as follows; 1) With metals of high melting point, momentary 1000 .deg. C may last below $10^{-4}$ of a second. It is thought that above phenomena back up previous adhesion theory in wear. 2) As a general rule, surface temperature in contact with different metals becomes high when the load increases while it is observed that surface temperature decreases when the load increases with shapes of specimens.

• Journal of ILASS-Korea
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• v.19 no.1
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• pp.9-14
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• 2014

Performance of DI diesel engine with high-pressure fuel injection equipment is directly related to its emission characteristics and fuel consumption. So, the electro-hydraulic injector for the common-rail injection system should be designed to meet the precise high fuel delivery control capability. Currently, most high pressure injector in use has a needle driven by the solenoid coil energy or the piezo actuator controlled by charge-discharge of output pulse current. In this study, macroscopic spray approaching method was applied under constant volume chamber to research the performance of three different injectors : solenoid, indirect-acting piezo and direct-acting piezo type for CR direct-injection. LED back illumination for Mie scattering was applied on the liquid spray visible of direct-acting piezo injector, including hydraulic-servo type solenoid and piezo-driven injectors. As main results, we found that a direct-acting piezo injector had better a spray tip penetration than hydraulic-servo injectors in spray visualization.

• 한국연소학회:학술대회논문집
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• 2003.12a
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• pp.251-256
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• 2003

The capability of pilot injection with small fuel quantity at all engine operating conditions is one of the main feature of the common rail system. The purpose of the pilot injection is to lower the engine noise and to reduce the NOx emissions. This study describes the pilot spray structure characteristics of the common-rail diesel injectors, solenoid-driven and piezo-driven type, with different electric driving characteristics So, three common-rail injectors with different electric current wave were used in this study. The pilot spray characteristics such as spray speed, spray tip penetration, and spray angle were obtained by spray images, which is measured by the back diffusion light illumination method with optical system for high-speed temporal photography. Also the CFD analysis was carried out for fuel behavior under high pressure in between needle and nozzle of solenoid-driven injector to know the condition of initial injection at experiment test. It was found that pilot injection of common-rail system was effected by rate of injection and temperature of injected fuel and electrical characteristic of the driven injector.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.786-788
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• 2013

Molybdenum (Mo) thin film has high electrical conductivity and has been used for a back contact of CIGS thin film solar cell. Generally, the electrical conductivity and the adhesion between the substrate and the film is greatly affected by sputtering conditions such as sputtering power, working pressure, and substrate temperature. In this study, Mo films were deposited by DC magnetron sputtering technique. The influence of sputtering pressure on the electrical and structural properties of Mo films was investigated by using SEM(scanning electron microscope), XRD(X-ray Diffraction), 4-point probe, Reflectance, Hall measurement.

• Journal of ILASS-Korea
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• v.9 no.1
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• pp.30-36
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• 2004

The purpose of this study was to investigate the fuel spray characteristics that made most important at an homogeneous air fuel mixture, in a common rail direct injection type HCCI engine. As a study conducted relation which a back pressure and injection pressure are influenced to air fuel mixture characteristics, we tried to offer date even through we select suitable to a HCCI engine running condition of the fuel injection condition. To accomplish the study, to measure a injection rate of common rail type injector and to visualize and simulate a fuel spray was conducted. From the result of injection rate, a common rail injector was confirmed to appear a initial delay of 0.3msec and a latter period delay of 0.7msec. Therefore, real injection duration was determined by about 0.5msec increasing. From the result of fuel spray, the spray penetration was proportional to 1/4 exponent of atmosphere pressure. An experimental equation was deduced from the spray penetration of spray visualization experiment and the relation of injection duration and penetration was estimated in HCCI engine using an experimental equation.