• 산업기술연구
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• 제32권A호
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• pp.65-70
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• 2012

Carboxy-guns are used for rapid and precise injection of $CO_2$ gas to the target skin area using external power source. In the design of carboxy-gun, the most important thing is how to precisely control injection volume of $CO_2$ gas. This paper deals with the control scheme of injection volume of carboxy-gun using solenoid valve. First the amount of volume that passes through the solenoid valve under on-off time ratio control is estimated based on the assumption of compressible gas flow. The flow rate of gas is experimentally measured under the varying pressure of the gas reservoir. Two results showed good correlation to each other, thus demonstrating the validity of the volume control strategy.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.712-716
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• 2003

In the present study, the gas injection system based on air-water model was designed to investigate the behavior characteristics of bubbles injected into a ladle. The parameters such as gas volume fraction and bubble rise velocity were exprementally measured in a gas-liquid flow region. To measure gas volume fraction, an electo-conductivity probe was used and bubble rise velocity was obtained by a high speed CCD camera. Gas volume fraction was symmetric to the axis of nozzle secured on the bottom of a ladle. The bubble rise velocity was calculated for two different experimental conditions. That is, gas flow conditions were following two case: 1) Q = $0.63{\times}10^{-4}$ $m^{3}/s$, 2) $1.26{\times}10^{-4}$ $m^{3}/s$. As a gas injected into the liquid ladle, the liquid-phase region is circulated by bubbles' behavior. The bubble rise velocity was influenced of the circulation flow of liquid phase. As a result, the bubble rise velocity was appeared higher middle region of ladle than near the nozzle.

• 한국주조공학회지
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• 제18권5호
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• pp.481-487
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• 1998

Shell sand is widely used to make a complex shape castings due to its good collapsibility. When molten metal is poured into the mold, various gases are generated by the thermal decomposition of binder in the shell core. Casting defects such as blow hole and blister come from these gases. If it is possible to predict the evolution of gas quantitatively, it may provide effective solutions for minimizing the casting defects. To examine the gas evolution by shell core quantitatively, casting experiment and calculation were carried out. Gas pressure and gas volume evolved by shell core were measured in the experiment, and temperature distribution in the shell core was obtained by heat transfer analysis. From the result above, prediction on the gas volume evolved during pouring was tried. As forming pressure of the shell core increased and forming temperature decreased, the gas evolution increased. There was a close relationship between the calculated gas volume evolved and the measured one.

• 제어로봇시스템학회논문지
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• 제9권9호
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• pp.707-713
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• 2003

We investigate the ultrasonic gas flow meter for the measurement of gas volume quantity, which passing through pipe, using the transit time difference method. We have designed a receiving system of an ultrasonic signal and hardware system of a flow meter Also, we have designed an experimental system for the characteristic test and calibration of a gas flow meter system. We have developed an ultrasonic gas flow meter, which has a measurement uncertainty within $\pm$ 1.7 %. For the test, we have compared our system with a difference pressure type flow meter for a few months in the real field. Through the test, we have confirmed that our system have a good reliability and durability. Also, we have confirmed that our system follows very well the variation of gas volume quantity, which was measured by a difference pressure type flow meter.

• 한국수소및신에너지학회논문집
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• 제33권6호
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• pp.692-698
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• 2022

With the expansion of domestic hydrogen fuelling station infrastructure, it is necessary to secure reliability among hydrogen traders, and for this, technology to accurately measure hydrogen is important. In this study, 4 types of hydrogen trading volume calculation models (model 1-4) were presented to improve the accuracy of the hydrogen trading volume. In order to obtain the reference value of model 4, and experiment was conducted using a flow rate measurement equipment, and the error rate of the calculated value for each model was compared and analyzed. As a result, model 1 had the lowest metering accuracy, model 2 had the second highest metering accuracy and model 3 had the highest metering accuracy until a certain point. But after the point, model 2 had the highest metering accuracy and model 3 had the second metering accuracy.

• 한국항공우주학회지
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• 제35권4호
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• pp.323-328
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• 2007

소형 인공위성의 전형적인 추진 시스템인 냉가스 추진 시스템에 액화 연료를 직접 적용하여 성능을 분석하였다. 고려하는 액화 연료 냉가스 추진 시스템과 일반적으로 사용되는 질소 추진 시스템의 성능을 비교하였다. 질소 추진 시스템과 동일한 질량 조건, 동일한 부피 조건, 동일한 총 임펄스 조건에서 각각 액화 연료를 사용한 냉가스 시스템의 성능과 필요한 연료 탱크의 부피, 필요한 추진 시스템의 질량을 산출하였다. 액화 연료를 사용한 냉가스 추진 시스템은 일반적인 질소 추진제를 사용한 시스템보다 성능, 부피 및 질량 등에서 많은 이점을 가지며 냉가스 추진 시스템에 직접적으로 적용이 가능함을 알 수 있었다.

• 한국자동차공학회논문집
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• 제9권4호
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• pp.1-9
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• 2001

The soot yield has been studied by a premixed propane-oxygen-inert gas combustion in a specially designed disk-type constant-volume combustion chamber to investigate the effects of pressure, temperature and turbulence on soot formation. Premixtures are simultaneously ignited by eight spark plugs located on the circumference of chamber at 45 degree intervals in order to observe the soot formation under high pressures. The eight flames converged compress the end gases to a high pressure. The laser schlieren and direct flame photographs for observation field with 10 mm in diameter are taken to examine into the behaviors of flame front and gas flow in laminar and turbulent combustion. The soot volume fraction in the chamber center during the final stage of combustion at the highest pressure is measured by the in situ laser extinction technique and simultaneously the corresponding burnt gas temperature by the two-color pyrometry method. The pressure and temperature during soot formation are changed by varying the initial charge pressure and the volume fraction of inert gas compositions, respectively. It is found that the soot yield increases with dropping temperature and rising pressure at constant equivalence ratio, and that the soot yield of turbulent combustion decreases in comparison with that of laminar combustion because the burnt gas temperature increases with the drop of heat loss.

• 한국자동차공학회논문집
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• 제3권6호
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• pp.112-122
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• 1995

As an alternative fuel producing less exhaust emissions, natural gas is of interest for use both in SI and CI engines. The potential of natural gas fuelled dual-fuel engine is considered high enough. However, much effort has to be made so that gaseous fuel is used efficiently with simultaneous minimum use of pilot oil. Hence, a simplified three-dimensional model, using a finite volume method in cylindrical coordinates, has been developed to facilitate an understanding of the dual-fuel combustion phenomena and to predict the complex interactions between the pilot distillate and natural gas. The computer model was calibrated by comparing it with the experimental results obtained from diesel engine like combustion bomb tests. In the pre-mixed natural gas combustion, the fuel burning was highly reliant on the injection condition and subsequent burning nature of the pilot distillate.

• 한국가스학회지
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• 제3권3호
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• pp.23-28
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• 1999

밀폐공간 내에 블록을 조합하여 부피와 표면적이 다르게 내용물을 채우고 용기 부피에 대한 내용물의 부피와 내용물의 표면적을 변화시키면서 LPG 또는 NG와 공기 혼합가스의 폭발특성을 측정하여 밀폐공간 내부에 있는 내용물의 부피와 표면적의 변화가 폭발특성에 미치는 영향을 해석하고자 하였다. 폭발용기는 가로 세로 높이가 각각 $100cm{\times}60cm{\times}45cm$인 부피 270리터의 금속 용기이며, 용기 내 가연성 혼합가스는 전기 스파크로 착화시켰고, strain형 압력센서로 폭발압력을 측정하였다. 실험 결과 부피봉쇄율이 증가할수록 폭발압력이 감소하였으며, 내용물의 표면적의 증가에 따라서도 폭발압력이 낮아졌으며, 이러한 폭발압력의 감소 경향은 표면적의 증가에 대한 영향보다 부피의 증가에 의한 영향이 더욱 크게 나타났다.

• Korea-Australia Rheology Journal
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• 제16권1호
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• pp.47-54
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• 2004

Low Reynolds number, dilute, and surfactant-free bubble suspensions are prepared by mechanical mixing after introducing carbon dioxide bubbles into a Newtonian liquid, polyol. The apparent shear viscosity is measured with a wide-gap parallel plate rheometer by imposing a simple shear flow of capillary numbers(Ca) of the order of $10^{-2}$ ~ $10^{-1}$ and for various gas volume fractions ($\phi$). Effects of capillary numbers and gas volume fractions on the viscosity of polyol foam are investigated. At high capillary number, viscosity of the suspension increases as the gas volume fraction increases, while at low capillary number, the viscosity decreases as the gas volume fraction increases. An empirical constitutive equation that is similar to the Frankel and Acrivos equation is proposed by fitting experimental data. A numerical simulation for deformation of a single bubble suspended in a Newtonian fluid is conducted by using a newly developed two-dimensional numerical code using a finite volume method (FVM). Although the bubble is treated by a circular cylinder in the two dimensional analysis, numerical results are in good agreement with experimental results.