• 열처리공학회지
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• 제13권3호
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• pp.143-150
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• 2000

Ferritic plasma nitrocarburising was performed on pure iron using a modified DC plasma unit. This investigation was carried out with various gas compositions which consisted of nitrogen, hydrogen and carbon monoxide gases, and various gas pressures for 3 hours at $570^{\circ}C$. After treatment, the different cooling rates(slow cooling and fast cooling) were used to investigate its effect on the structure of the compound layer. The ${\varepsilon}$ phase occupied the outer part of the compound layer and ${\gamma}^{\prime}$ phase existed between the ${\varepsilon}$ phase and the diffusion zone. The gas composition of the atmosphere influenced the constitution of the compound layer produced, i.e. high nitrogen contents were essential for the production of ${\varepsilon}$ phase compound layer. It was found that with increasing carbon content in the gas mixture the compound layer thickness increased up to 10%. In the gas pressure around 3 mbar, the compound layer characteristics were slightly effected by gas pressure. However, in the low gas pressure and high gas pressure, the compound layer characteristics were significantly changed. The constitution of the compound layer was altered by varying the cooling rate. A large amount of ${\gamma}^{\prime}$ phase was transformed from the ${\varepsilon}$ phase during slow cooling.

• 한국분무공학회지
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• 제3권3호
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• pp.49-59
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• 1998

The vaporization characteristics and spray combustion processes in the high-pressure environment are numerically investigated. This study employ the high-pressure vaporization model together with the state-of-art spray submodels. The present high-pressure vaporization model can account for transient liquid heating, circulation effect inside the droplet forced convection, Stefan flow effect, real gas effect and ambient gas solubility in the liquid droplets. Computations are carried out for the evaporating sprays, the evaporating and burning sprays, and the spray combustion processes of the turbocharged diesel engine. Numerical results indicate that the high-pressure effects are quite crucial for simulating the spray combustion processes including vaporization, spray dynamics, combustion, and pollutant formation.

• 전기학회논문지
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• 제56권1호
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• pp.142-146
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• 2007

Nowadays, itis inevitable trend to use high Xe gas contents for increase luminous efficiency and luminance in plasma display panel. However, the increase of Xe gas contents causes the driving voltage, although the brightness is increase. In this paper, we study the characteristics of electro optical according to Xe gas contents and gas pressure. Electro-optical characteristics were investigated by the discharge voltage, luminance and luminous efficacy measurements, respectively. With some increasing Xe gas contents and pressure, the electro-optical properties increased. However, the characteristics of electro-optical begin to be saturated, when too high increased Xe gas contents and pressure.

• 한국기계가공학회지
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• 제10권3호
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• pp.67-72
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• 2011

Turbine blades operate under high temperature and pressure. The influence changes according to its width and angle. Thermal stress and pressure are important factors to analyze the stress distribution. The purpose of this study is to investigate the effects of loads on the gas turbine blade using thermal stress analysis. These analysis results show the gas fluid flow with a high pressure around the surface of blade. Gas temperature is related to the pressure of flow around the blade. The stress concentration around blade is shown and the concentration is due to the difference between suction side and pressure side of combustion gas.

• 반도체디스플레이기술학회지
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• 제11권2호
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• pp.17-21
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• 2012

This study developed a high-temperature, high-pressure dynamic pressure sensor using LGT(lanthanum gallium tantalate). The sensitivity of the fabricated dynamic pressure sensor was 2.1 mV/kPa and its nonlinearity was 2.5%FS. We confirmed that the high-temperature dynamic pressure sensor operated stably in high-temperature environment at $500^{\circ}C$. The developed dynamic pressure sensor using LGT is expected to be applicable not only to gas turbines but also in various industrial areas in duding airplanes and power stations.

• 한국세라믹학회지
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• 제30권4호
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• pp.309-315
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• 1993

Gas pressure sintering is a promising process in various densification methods of high strength Si3N4 ceramics. Environmental influences on gas pressure sintering of Si3N4 was investigated with the variationof packing powder, specimen container and N2 gas pressure. The specimens had higher density, larger weight loss and inhomogeneous color in graphite specimen container than in SN26 crucible. The variations of sintering densities in various packing powders (Si3N4, SN26, AlN, BN) were very small but SiC powder was synthesised in graphite crucible with Si3N4 packing powder, aluminium oxynitride compounds were synthesised in SN26 crucible with AlN packing power. Also N2 gas pressure over 20kg/$\textrm{cm}^2$ reduced the densification of Si3N4 in one step-gas pressure sintering. As the result of two step-gas pressure sintering at 700kg/$\textrm{cm}^2$ for 15min., relative density of 99.9% and 3-point bending strength of 1090MPa and dense microstructure of 3~4${\mu}{\textrm}{m}$ grain size were obtained.

• 한국수소및신에너지학회논문집
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• 제31권5호
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• pp.453-458
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• 2020

In this study, ethylene-propylene-diene monomer (EPDM) rubbers reinforced with various particle size of carbon black were prepared and tested. We followed recently published CSA/ANSI CHMC2 standard "the test methods for evaluating material compatibility in compressed hydrogen applications-polyemr". Measurement of change in hardness, tensile strength and volume were performed after exposure to maximum operating pressure, 87.5 MPa, for 168 hours (1 week). Once EPDM was exposed to high-pressure hydrogen, the samples experience volume increase and degradation of the physical properties. Also, after the dissolved hydrogen was fully eliminated from the specimens, the hardness and the tensile properties were not recovered. The rubber reinforced with smaller sizes of carbon black particles showed less volume expansion and decrease of physical properties. As a result, smaller particle size of carbon black filler led to more resistance to high-pressure hydrogen.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
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• pp.345-348
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• 2010

Two-stage light-gas gun은 고압실, 압축실 그리고 발사관으로 비교적 간단한 구조로 구성되며, 짧은 시간동안 초고압을 발생시키기 용이함으로 현재까지 고속충격역학, 발사체 공기역학, 재료역학 등 다양한 공학 분야에서 적용되어왔다. 본 연구는 초고압 액체 제트 분사에 적용하기 위한 기초적 연구로서, 고압실 하류에 설치된 제1격막의 파막 압력의 변화에 따른 발사체의 속도 변화 및 관내 압력 거동을 조사하기위하여, 다양한 격막을 적용하여 실험을 수행하였다. 제1격막의 파막 압력은 발사체의 속도에 지배적인 영향을 미치게 되며, 약 14 Bar이상일 경우 발사관의 압력이 압축튜브의 압력보다 크게 증가하였다.

• 한국건축시공학회지
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• 제5권3호
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• pp.131-138
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• 2005

The study is focused on the settling the developing direction of korean gas pressure welding machine which can be applied in korean construction sites with moderate and high performance. Gas pressure welding is more economical and has good performances than other steel bar jointing methods, as arc welding and mechanical joint etc. Therefore in Japan, the gas pressure welding, which has less loss of steel bars and low performance of joints, when connecting the D29 and thicker steel bars, Is one of the typical connection of steel reinforcement. But in Korea, the gas pressure welding method is not widely used caused by the shortage of skilled workers, and this situation in Korea can not be solved in short period. The training of the skilled workers takes long period(around $6\~10$ years), and there is no certification system for gas pressure welding. So to activate the gas pressure welding in Korea, the development of the automatic gas pressure welding machine is necessary, which gives regular performance of the steel bar joints and can be operated by not sufficient skilled workers. The automatic gas pressure welding machine was developed in Japan, but this machine has many problems when applied in korean construction sites. Therefore, it is necessary to develop a korean automatic gas pressure welding machine to overcome this problems. To develop korean automatic gas pressure welding machine, the problems, which shows when applied in korean construction sites, need to be investigated. According to the investigation, counterproposals are presented for the pragmatical development of the korean automatic gas pressure welding machine.

• Korean Chemical Engineering Research
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• 제58권4호
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• pp.610-617
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• 2020

In process installations, chemicals operate at high temperature and high pressure. Propylene is used as a basic raw material for manufacturing synthetic materials in the petrochemical industry; However, it is a flammable substance and explosive in the gaseous state. Thus, caution is needed when handling propylene. To prevent explosions, an inert gas, carbon dioxide, was used and the changes in the extent of explosion due to changes in pressure and oxygen concentration at 25 ℃, 100 ℃, and 200 ℃ were measured. At constant temperature, the increase in explosive pressure and the rates of the explosive pressure were observed to rise as the pressure was augmented. Moreover, as the oxygen concentration decreased, the maximum explosive pressure decreased. At 25 ℃ and oxygen concentration of 21%, as the pressure increased from 1.0 barg to 2.5 bar, the gas deflagration index (K_g) increased significantly from 4.71 barg·m/s to 18.83 barg·m/s.