• International Journal of Automotive Technology
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• 제5권3호
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• pp.181-188
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• 2004

A cylindrical constant-volume combustion chamber was used to investigate the flow characteristics at the spark electrode gap and the combustion characteristics of an inhomogeneous charge methane-air mixture under several parameters such as stratified pattern, initial charge pressure, ignition time and the excess air ratio of the initial charge mixture. Flow characteristics including mean velocity and turbulence intensity were analyzed by a hot-wire anemometer. The combustion pressure development, measured by a piezo-electric pressure transducer, was used to investigate the effect of initial charge pressure, excess air ratio and ignition times on combustion pressure and combustion duration. It was found that the mean velocity and turbulence intensity had the maximum value around 200-300 ms and then decreased gradually to near-zero value at 3000 ms. For the stratified patterns, the combustion rate under the rich injection (RI) condition was the fastest. Under the initial charge conditions, the second mixture was accompanied by an increase in the combustion rate, and that the higher the mass which is added in the second stage injection, the faster the combustion rate.

• 한국자동차공학회논문집
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• 제12권2호
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• pp.1-8
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• 2004

A cylindrical constant volume combustion chamber was used to investigate the exhaust emission characteristics of homogeneous charge, stratified pattern and inhomogeneous charge under various conditions using gas chromatography. In the case of homogeneous charge condition, the $CO_2$ concentration is proportional to excess air ratio and overall charge pressure, the $CO_2$ concentration is proportional to excess air ratio and the UHC concentration is inversely proportional to ignition time and overall charge pressure. In the case of stratified pattern, the RI(rich injection) condition shows better exhaust emission characteristics, especially $CO_2$, than that of HI (homogeneous injection) or LI (lean injection) conditions. In inhomogeneous charge conditions, when initial charge pressure is increased, $CO_2$ and UHC concentration is reduced but $O_2$ concentration is increased. And when the excess air ratio of initial charge mixture is 3.0, UHC and $CO_2$concentration show lowest values.

• 한국자동차공학회논문집
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• 제11권4호
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• pp.29-36
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• 2003

A cylindrical constant volume combustion chamber was used to investigate the flow characteristics at spark plug and the combustion characteristics of inhomogeneous charge methane-air mixture under several parameters. The flow characteristics such as mean velocity and turbulence intensity was analyzed by hot wire anemometer. Combustion pressure development measured by piezoelectric pressure transducer was used to investigate the effect of initial charge pressure, excess air ratio and ignition times on combustion pressure and combustion duration. Mean velocity and turbulence intensity had the maximum value at 200 or 300ms and then decreased to beneath 0.05m/s gradually at 3 seconds. Second mixture is accompanied by an increase in the combustion rate, and that the higher the mass which is added in the second stage injection, the faster the burn rate.

• 한국자동차공학회논문집
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• 제11권3호
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• pp.48-57
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• 2003

A cylindrical constant volume combustion chamber was used to investigate the flow characteristics at spark plug and the combustion characteristics of homogeneous charge methane-air mixture under various initial pressure, excess air ratio and ignition times in quiescent mixture. The flow characteristics such as mean velocity and turbulence intensity was analyzed by hot wire anemometer. Combustion pressure development measured by piezoelectric pressure transducer and flame propagation acquired by ICCD camera were used to investigate the effect of initial pressure, excess air ratio and ignition times on pressure, combustion duration, flame speed and burning velocity. Mean velocity and turbulence intensity had the maximum value at 200 or 300ms and then decreased to near 0 value gradually after 3 seconds. Combustion duration, flame speed and burning velocity were observed to be promoted with excess air ratio of 1.1, lower initial pressure and ignition time of 300ms.

• 한국대기환경학회지
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• 제28권6호
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• pp.644-655
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• 2012

As soon as a new air filter is applied to an air purification process, the filter gets loaded with dust particles. Thus, the study on the particle loading characteristics of air filter is very essential in order to understand the real filtration phenomena during filter use. In this study, we investigated the effect of particle and filter charge on the particle loading property of air filter. Charged filter and uncharged filter prepared by discharging the charged filter by isopropyl alcohol were used as test samples, and three types of particle having different charge states were supplied to filters tested. For neutralized particles there was a big difference in areal mass loading rates between charged and uncharged filters due to the very small amount of particle charge, on the other hand the difference was diminished for atomized particle and finally almost vanished for corona charged particles. The pressure drop of filter loaded with corona charged particles was only half of those for neutralized and atomized particles at the same areal mass loading because of the porous structure of particle deposit formed on filter fibers, caused by the space charge effect between particles.

• International Journal of Automotive Technology
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• 제6권4호
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• pp.323-332
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• 2005

A cylindrical constant volume combustion chamber was used to investigate the flow characteristics at the spark electrode gap and the combustion characteristics of a homogeneous charged methane-air mixture under various overall charge pressures, excess air ratios and ignition times. The flow characteristics, including the mean velocity and turbulence intensity, were analyzed with a hot wire anemometer. Combustion pressure development measured by piezoelectric pressure transducer, a flame propagation image acquired by ICCD camera and exhaust emissions measured by 2-valve gas chromatography were used to investigate effects of initial pressures, excess air ratios and ignition times on the combustion characteristics. It was found that the mean velocity and turbulence intensity had the maximum value around 200-300 ms and then decreased gradually to a near-zero value after 3000 ms and that the combustion duration was shorten and the flame speed and laminar burning velocity had the highest value under the condition of an excess air ratio of 1.1, an overall charge pressure of 0.15 MPa and an ignition time of 300 ms in the present study. The $CO_2$ concentration was proportional to the ignition time and overall charge pressure, the $CO_2$ concentration was proportional to the excess air ratio, and the UHC concentration was inversely proportional to the ignition time and overall charge pressure.

• 한국연소학회지
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• 제13권3호
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• pp.9-16
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• 2008

In this study, a cylindrical constant volume combustion chamber is used to investigate the flow and combustion characteristics of methane-air homogeneous mixture under various initial charge pressure, excess air ratios and ignition times. The flame and burning speed, mean gas speed are calculated by numerical analysis to analyze the combustion characteristics. It is found that the mean gas velocity during combustion has the maximum value around 300 ms and then decreased gradually on the condition of 10000 ms, and that the combustion duration is shorten and flame speed and burning velocity have the highest value under the conditions of an excess air ratio 1.1, an initial charge pressure of 0.2 MPa and an ignition time of 300 ms in the present study. And, the initial pressure and burning speed are in inverse proportion, so that it is in agreement with Strehlow who presented that the initial pressure and burning speed are in inverse proportion when the burning speed is under 50cm/s.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 후기학술대회논문집
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• pp.15-16
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• 2005

In this study, the characteristics of NOx reduction by using charge air moisturizer system were evaluated by engine performance simulation in medium speed diesel engines. The results of performance simulation were verified by experimental results of single cylinder medium speed diesel engine equipped with charge air moisturizer system. Performance simulation was carried out to evaluate charge air moisturizer system of turbocharged diesel engine, HYUNDAI HiMSEN 9H25/33 engine. Those results show 50% NOx reduction at dew point $80^{\circ}C$ and charge air pressure 4bar.

• 화약ㆍ발파
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• 제29권1호
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• pp.1-9
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• 2011

에어데크 공법은 노천광 및 대규모 발파현장에서 널리 쓰이는 대표적인 발파기술 중 하나이다. 에어데크 공법의 효율성 극대화를 위해 그간 많은 연구와 실험이 이루어졌으며, 공내에서 어떠한 압력 거동을 일으키는가를 규명하기 위한 노력들이 있었다. 본 연구에서는 다양한 에어데크 조건하에서 각 에어데크 구간이 어떠한 압력의 차이를 일으키는가에 대해 수치해석적으로 분석하였고, 에어데크의 위치와 에어데크 구간의 길이에 대한 압력변화를 알아보았다. 기본적으로 모든 수치해석은 JWL 상태방정식을 사용하였으며 2차원 평면상에서 진행 하였다. 순수한 압력의 변화만을 관찰하기 위해 암반의 밀도와 강도만을 달리하고 모든 암반은 균질한 상태로 가정하였다.

• 설비공학논문집
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• 제14권8호
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• pp.617-625
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• 2002

In this study, effects of refrigerant and oil charges on the performance of a refrigeration system simulating an automobile air conditioner have been experimentally investigated using R134a and PAG oil. Measurements were taken in a breadboard type refrigeration test unit with a compressor used for a commercial automobile air-conditioner under a set of condition imposed upon normally to automobile air conditioners. Both the COP and capacity decreased rapidly as the oil charge increased because of the decrease in vapor pressure of the circulating refrigerant/oil mixture. The excess oil left in the evaporator also caused heat transfer degradation resulting in a decrease in capacity and in turn COP. It was found that there is an optimum refrigerant charge at which the COP becomes the maximum. Below this optimum charge, both the capacity and COP increased as the refrigerant charge increased and above the optimum charge, both of them remained almost constant. Hence, the COP seems to be the most important factor in determining the optimum refrigerant charge. When the system was undercharged, the refrigerant at the condenser exit lost subcooling and showed a sign of poor miscibility.