• 한국자동차공학회논문집
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• 제7권6호
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• pp.57-64
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• 1999

Initial flame development and propagation were visualized under the new ignition system developed to estimate the effects of ignition characteristics on the engine performance in a port injection SI engine. Effects of intake air flow characteristics were also investigated by three different kinds of the swirl control valve. Experiments were performed in an optical single cylinder engine modified form a commercial engine. Flame images were captured through the quartz window mounted in the piston by the high speed video camera and analyzed to compare initial flame development. Results show that IMEP tends to rise slightly as the ignition duration gets longer. The direction of flame propagation is decisively governed by the in-cylinder flow motion. Every flame grows toward the exhaust valve forming a kind of turbulent flame. Initial flame propaagation characteristics are very similar to ones analyzed form pressure data.

• 한국분무공학회지
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• 제9권1호
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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.

• 한국세라믹학회지
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• 제42권1호
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• pp.22-27
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• 2005

[ $B_{2}O_{3}-Mg-C$ ]계에서 자전연소합성법에 의한 C의 제조카 본 연구에서 조사되었다. B의 제조에 있어 반응기내 불활성 가스의 초기 압력, 혼합물내의 Mg와 C의 함량이 반응성과 반응생성물에 미치는 영향이 조사되었다. 본 반응계에서 자전 연소합성 반응이 가능한 반응기내 불활성 가스의 최소 초기 압력은 25기압이었다. 압력이 증가할수록 미반응 Mg의 농도는 감소하였으며 연소온도는 증가하였다 25기압의 반응기내 초기 불활성 가스 압력에서 순수 B의 제조를 위한 최적 조성은 $2B_{2}O_{3}+6.3Mg+0.94C$이었다. 이 조건에서 제조된 B는 부정형으로서 $1\~3{\mu}m$의 입자크기를 가지고 있었다.

• 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.

• International Journal of Automotive Technology
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• 제6권6호
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• pp.563-570
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• 2005

A numerical study of high pressure and temperature droplet vaporization and combustion is conducted by formulating one dimensional evaporation model and single-step chemical reaction in the mixture of hydrocarbon fuel and air. The ambient pressure ranged from atmospheric conditions to the supercritical conditions. In order to account for the real gas effect on fluid p-v-T properties in high pressure conditions, the modified Soave-Redlich-Kwong state equation is used in the evaluation of thermophysical properties. Some computational results are compared with Sato's experimental data for the validation of calculations in case of vaporization. The comparison between predictions and experiments showed quite a good agreement. Droplet surface temperature increased with increasing pressure. Ignition time increased with increasing initial droplet diameter. Temporal or spatial distribution of mass fraction, mass diffusivity, Lewis number, thermal conductivity, and specific heat were presented.

• Geomechanics and Engineering
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• 제15권6호
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• pp.1219-1225
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• 2018

In this study, a comprehensive laboratory experimental programme was conducted on expansive soil with a high swelling potential to study the influence of different additive materials on swelling pressure and index properties. Lime, sand, multifilament fiber and fibrillated fiber were used for stabilization of expansive soil. Lime, sand and fibers were respectively added to the expansive soil at 0-7%, 0-80%, 0-0.5%. On each mixture that was prepared by the proportions mentioned above, Atterberg limits, compaction, and swelling pressure tests were conducted. From the result of these experiments, the swelling pressure-time relation could be replaced by a rectangular hyperbola established to facilitate the prediction of ultimate percent swelling with a few initial data points. The best type of additive and its optimum ratio for engineering purposes could be estimated rapidly by this approach.

• 자원리싸이클링
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• 제20권4호
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• pp.71-77
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• 2011

$MoO_3$ 분말을 723 K ~ 873 K에서 Ar+$H_2$ 혼합기체를 이용히여 수평관상로에서 $MoO_2$로 훤원하였으며, 반용속도를 배가스 중의 상대습도를 측정하여 계산하였다. 반응속도는 수소가스 분압과 반응속도에 따라 현저하게 증가하였다. 환원 반응초기에 $H_2O$의 발생속도가 급격하게 증가하였으며, 시간의 경과에 따라 배가스 중의 $H_2O$ 분압은 급격하게 감소하였다. 이 시기에 환원 반응율은 직선적으로 증가하였다. 환원반응 초기의 $MoO_3$에서 $MoO_2$로의 환원반응의 활성화 에너지는 73.56 kJ/mol로 계산되었다.

• 한국가스학회지
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• 제16권1호
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• pp.8-14
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• 2012

수소는 온실가스 배출을 저감하기 위한 미래 에너지로 고려되고 있지만, 폭발위험에 대한 문제점을 지니고 있다. 따라서 수소가 미래 에너지로 사용되기 위해서는 폭발위험에 대한 연구가 충분히 이루어져야 한다. 폭발위험은 폭발충격에 대한 이해 즉, 폭발과정에서 압력 상승속도에 대한 분석과 밀접한 관계가 있다. 본 연구에서는 폭발에 영향을 미치는 변수, 즉 연소 전후의 비열비, 화학평형상태에서 최대폭발압력, 그리고 연소속도, 이들 변수가 압력 상승속도에 미치는 영향을 살펴보았다. 화학평형상태에서 최대폭발압력과 연소속도는 압력 상승곡선에 큰 영향을 미치는 것을 알 수 있었고, 미연소 가스의 비열비는 초기압력 상승속도보다 최종압력 상승속도에 더욱 영향을 미치고, 연소가스의 비열비는 반대로 초기압력 상승속도에 더욱 큰 영향을 미치는 것을 알 수 있었다. 연소속도는 실험 데이터로부터 구하였으며 밀폐공간에서 수소가스 폭발에서는 폭연에서 폭굉으로 전이가 일어나기에는 연소속도가 매우 느림을 알 수 있었다.

• 한국자동차공학회논문집
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• 제12권3호
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• pp.75-82
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• 2004

The allowable exhaust standard has been intensified as a part of the countermeasure to decrease air pollution in the world. As the cars with an alternative fuel starts to get into the spotlight, the cars with low emission has been introduced and exhaust gas regulation forced in this country. These days, LPG vehicles, which infrastructure of fuel was already built up, and CNG vehicles are recognized for alternative fuel cars in this country. In this study, the constant volume combustion chamber was manufactured and used for experiments to obtain the ignition characteristics of LPG fuel and the optimal ignition energy. The experiment measured the combustion characteristics, in regard to the change of combustion variable, and the change of ignition energy. During the combustion of fuel, the maximum temperature inside the combustion chamber is higher when the initial pressure is higher. The burning velocity also seems to have the same characteristic as the temperature. However, the heat flux did not change much with the theoretical correct mixture but the various initial temperature of the combustion chamber. The heat flux got faster and ignition energy bigger as the dwell time of the ignition system expanded. When the dwell time get longer, the ignition energy also increased then fixed. The ignition energy increased as the initial pressure inside the combustion chamber higher. The heat flux got faster as the dwell time expanded.

• 한국연소학회지
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• 제20권3호
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• pp.21-26
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• 2015

This study was performed to provide the information of the combustion characteristics of n-butanol fuel in accordance with the n-heptane fuel mixing ratio. The closed homogeneous reactor model was used for the analysis. The analysis conditions were set to 800 K of the initial temperature, 20 atm of initial pressure and 1.0 of equivalence ratio. The results of analysis were compared in terms of combustion temperature, combustion pressure, CO, Soot and $NO_X$ emissions. The results of combustion and exhaust emission characteristics showed that ignition delay was decreased and the combustion temperature was increased as the n-heptane mixing ratio was increased. Also, the carbon monoxide(CO) was slightly decreased however, the soot and nitrogen oxides($NO_X$) increased a little in accordance with the n-heptane fuel mixing ratio. In addition, the pressure difference was almost the same in any conditions.