• International Journal of Automotive Technology
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• 제7권6호
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• pp.675-680
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• 2006

In the direct injected gasoline engine, atomized spray is desired to achieve efficient mixture formation needed to good engine performance because the injection process leaves little time for the evaporation of fuels. Therefore, substantial understanding of global spray structure and quantitative characteristics of spray are decisive technology to optimize combustion system of a GDI engine. The combustion and emission characteristics of gasoline-fueled stratified-charge compression ignition(SCCI) engine according to intake temperature and compression ratio was examined. The fuel was injected directly to the cylinder under the high temperature condition resulting from heating the intake port. With this injection strategy, the SCCI combustion region was expanded dramatically without any increase in NOx emissions, which were seen in the case of compression stroke injection. Injection timing during the intake temperature was found to be an important parameter that affects the SCCI region width. The mixture stratification and the fuel reformation can be utilized to reduce the required intake temperature for suitable SCCI combustion under each set of engine speed and compression ratio conditions.

• Macromolecular Research
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• 제11권2호
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• pp.73-79
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• 2003

Generally, field performance of elastomeric track pad components has been poor, especially for the medium to heavy tonnage tracked vehicles, which are operated on the hilly cross-country course. The service life of these track pad, is affected not only by the terrain and environmental conditions but also by the speed, cornering, braking, weight of the vehicle, and the track tread design. In this research, modulus, tearing energy, and the rate of crack propagation of vulcanizates are evaluated by changing base materials to improve the service time of track pad. By increasing the contents of carbon black, modulus, tearing energy, and fatigue crack growth resistance of vulcanizates improved. Compared with the NR vulcanizate, the HNBR vulcanizate had a higher value of tearing energy. The rate of crack propagation of vulcanizates using smaller size carbon black was slower than that using larger size carbon black. When the HNBR was blended with the ZSC, the tearing energy of the vulcanizates was a little reduced because of the high modulus but the crack propagation rate was reduced significantly. In the relation between the crack propagation rate and the strain energy release rate, though up to 100% strain were applied to specimens, the slope on the log scale ($\beta$) varied between 1.72 and 2.3 with the kind of elastomer.

• 대한조선학회논문집
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• 제45권4호
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• pp.345-352
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• 2008

The motion of a projectile initiated by the release of highly pressurized air is simulated presuming the flow field as a two dimensional one. The effects of water compressibility on projectile movements are investigated, comparing results based on the Fluent VOF model where water is treated as an incompressible medium with those from the presently developed VOF scheme. The present model considers compressibility of both air and water. The Fluent results show that the body moves farther and at higher speeds than the present ones. As time proceeds, the relative difference of speed and displacement between the two results drops substantially, after acoustic waves in water traverse and return the full length of the tube several times. To estimate instantaneous accelerations, however, requires implementation of the water compressibility effect as discrepancies between them do not decrease even after several pressure wave cycles.

• 대한기계학회논문집B
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• 제29권3호
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• pp.417-423
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• 2005

This paper describes the engine performance of a Homogeneous Charge Compression Ignition(HCCI) engine according to Exhaust Gas Recirculation(EGR), cylinder-to-cylinder, fuel of propane and butane. HCCI engines are being considered as a future alternative for diesel and gasoline engines. HCCI engines have the potential for high efficiency, very low NOx emissions and very low particulate matter(PM). On experimental work, we have done an evaluation of operating conditions in a 4-cylinder compression engine. The engine has been run with propane and butane fuels at a constant speed of 1800rpm. This work is intended to investigate the HCCI operation of the engine in this configuration that has been modified from the base diesel engine. The performance and emissions of the engine are presented. In this paper, the start of combustion(SOC) is defined as the $50{\%}$ point of the peak rate of heat release. SOC is delayed slightly with increasing EGR. As expected, NOx emissions were very low for all EGR range and nbuned HC and CO emission levels were high. CO and HC emissions are lower with using propane than butane as fuels of HCCI engines.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2013년도 제46회 KOSCO SYMPOSIUM 초록집
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• pp.109-110
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• 2013

This paper describes gas turbine combustion characteristics of synthetic natural gas which contains a small amount hydrogen content. By conducting ambient pressure high temperature combustion test at gas turbine relevant combustor geometry, the combustion characteristics such as combustion instability, NOx and CO emission, temperatures at turbine inlet, nozzle and dump plane, and flame structure from high speed OH chemiluminescence images were investigated when changing hydrogen content from zero to 5%. From the results, qualitative and quantitative relationships are derived between key aspects of combustion performance, notably NOx/CO emission and combustion instability. Natural gas containing hydrogen up to 5% does not show significant difference in view of all combustion characteristics except combustion instability. Only up to 1% hydrogen addition could not change the pressure fluctuation and phase gas between fluctuations of pressure and heat release. From the results, it can be concluded that synthetic national gas which contains 1% of hydrogen can be guaranteed for the stable and reliable operation of natural gas firing gas turbine.

• 동력기계공학회지
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• 제10권1호
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• pp.19-24
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• 2006

This work treats a controlled auto-ignition (CAI) single cylinder gasoline engine, focusing on the extension of operating conditions. The fuel was injected indirectly into electrically heated inlet air flow. In order to keep a homogeneous air-fuel mixing, the fuel injector was water-cooled by a specially designed coolant passage. The engine performance and emission characteristics were investigated under the wide range of operating conditions such as 40 in the air-fuel ratio, 1000 to 1800 rpm in the engine speed, 150 to $180^{\circ}C$ in the inlet-air temperature, and $60^{\circ}$ BTDC in the injection timing. The ultra lean-burn with self-ignition of gasoline fuel by heating inlet air was achieved in a controlled auto-ignition gasoline engine. It could be also achieved that the emission concentrations of carbon monoxide, hydrocarbons and nitrogen oxide significantly reduced by CAI combustion compared with conventional spark ignition engines.

• 한국화재소방학회논문지
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• 제23권3호
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• pp.73-78
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• 2009

Fire whirl은 도시 및 산림화재와 같이 광범위한 지형에서 주로 발생하며, 화염주위 환경의 불안전성에 의해 발생하는 현상이다. Fire whirl은 드물게 발생하지만, 높은 흡입력과 양력을 가지게 되어 연소속도를 증가시키는 매우 위험한 현상이다. 본 연구에서는 산림화재에서 발생하는 fire whirl 특성에 대한 고찰을 위해 굴참나무 낙엽을 이용한 fire whirl 실험 및 수치해석 연구를 실시하였다. 실험 결과 유입공기의 속도가 증가함에 따라 화원주위의 회전강도가 증가하여 발열량 및 화염길이가 일반 풀화재에 비해 최대 22.8%, 18.4% 증가하였으며, 수치해석은 실험결과와 유사한 경향을 나타내었다.

• 한국추진공학회지
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• 제17권2호
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• pp.1-8
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• 2013

모형 연소실에서 충돌형 분사기의 연소 안정성 평가를 위해 시간지연(time lag)과 간섭인자(interaction index)의 관계를 연구하였다. 산화제 분사 속도의 5%에 해당하는 섭동을 공진주파수로 인위적으로 가진하여 이에 대한 화염의 응답특성을 분석하였다. 연료와 산화제의 혼합지점인 충돌점들, 즉, 특성길이 위치에서 속도섭동과 열방출율 섭동간의 관계를 시간지연 모델을 이용하여 나타내었다. 시간지연을 정량화하는 개선된 방법으로서, 수치해석을 통해 얻은 결과로부터 분사기 출구면으로부터 충돌점까지 평균속도를 이용하는 방법을 제안하였다. 축방향의 평균속도가 증가할수록 시간지연이 짧아지는 경향성을 확인할 수 있었다.

• 한국수산과학회지
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• 제13권4호
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• pp.151-162
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• 1980

온산만내에서는 대조시 조류가 우세한 편이지만 (0.1 kt), 소조시의 표층류는 매우 불규칙하며(0.07 kt), 취송류와 지형성 소용돌이의 영향을 크게 받는다. 대조시 만북부에서는 썰물 때 동류하고 밀물 때 서류한다. 만남부에서는 밀물은 서북서류하고 철물은 동북동류이다. 만외에서는 조류가 우세하여 밀물 때 남-남남서류하고 썰물 때 북-북북동류한다. 최대유속은 $1\~1.1kt$로 관측되었다. 소조시의 항류는 북북동 14.3cm/sec였다. 우봉갑 남쪽 만입부에는 밀물갈때나 썰물갈 때 지름 약 1km미만의 시계방향 소용돌이가 존재하여 해수의 정체성이 비교적 강한편이다. 겨울의 취송류는 대체로 남류하며 최대유속은 약 0.1kt에 달한다. 온산만내에서 점원방출한 염료는 바람에 의해 변형되면서 주로 조류에 따라 만구쪽으로 이동, 분산하였고, 방출 3시간후의 평균확산계수는 $4.4\times10^4cm^2/sec$ 였다. 만외 만입부 시계방향의 환류내에서는 이보다 다소 낮은 값을 보였다.

• Journal of Radiation Protection and Research
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• 제37권3호
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• pp.116-122
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• 2012

미국 원자력규제위원회(U. S. NRC)에서 개발한 PAVAN 프로그램을 사용하여 기상자료의 통계처리방법에 따른 원자력발전소의 수명기간 중 발생할 수 있는 가상 사고시 단기 대기확산인자 값의 영향을 분석하였다. 대기확산을 평가하기 위한 기본요소는 기상자료이며, PAVAN에서는 대기안정도에 대한 풍향과 풍속의 발생빈도를 나타내는 결합빈도분포자료를 사용하여 평가한다. 고리와 월성 원자력발전소 부지에서 2006~2010년까지 5년간 관측된 기상자료를 사용하여 풍속등급의 분류방법(U. S. NRC 권고와 균등발생빈도 분류방법)과 평가에 적용되는 기상자료의 통계처리기간(1년, 2년, 3년, 4년, 5년)에 따른 결합빈도분포자료를 작성하여 단기 대기확산인자를 평가하였다. 평가결과, 두 원자력발전소 부지 모두 풍속등급의 분류에 따른 단기 대기확산인자 값의 영향은 미미한 반면 평가에 적용되는 기상자료의 분석기간은 상대적으로 중요한 영향을 나타냈는데, 최대값과 최소값의 비는 1.5배 이상의 차이를 보였다.