• 한국자동차공학회논문집
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• 제2권5호
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• pp.121-134
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• 1994

Shock tube investigation of ethylene oxide-$0_{2}-N_{2}$ mixture have been performed to reveal detonation characteristics of the mixture in terms of detonation pressure and speed. Theoretical calculation of thermodynamic parameters at the Chapmann-Jouguet detonation of the mixture has been also performed. A comparision of the observed results with the calculated ones can lead us to predict the detonation parameters of ethylene oxide in an artificial air. In addition, we have observed ignition delay times of ethylene oxide mixtures. The best fit of the observed delay times to Arrhenius gas kinetic relation gives : ${\tau}=10^{-144}{e{xp}}(E_a/RT)[C_{2}H_{4}O]^{-4.8}[O_{2}]^{-12.4}[N_{2}]^{-14.1}$ $E_a=3.67kcal/mole$ The observed activation energy is markedly reduced, compared with the case of ethylene oxide diluted in Ar. It could be due to the factor that $N_2$ play a role as detonation promoter yielding very reactive NOx radicals.

• Journal of Advanced Marine Engineering and Technology
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• 제24권4호
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• pp.446-453
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• 2000

The closed cycle diesel system is operated in closed circuit system where there is non air breathing with working fluid consisted of the combination of oxygen, argon and recycled exhaust gas for obtaining underwater or underground power sources. this study has been carried out to analysis the performance of closed cycle system by means of investigation on the combustion characteristics of diesel engine MTU8V183TE52 operating in open, semi-closed, and closed cycle modes. The combustion in closed mode starts a little bit earlier than in open cycle mode. The oxygen concentration and fuel consumption at 240kW closed cycle running are 21∼24% by volume and 77∼79kg/h, respectively. The maximum cylinder pressure and ignition delay time are investigated 110bar and 8.9degree. Also, The combustion simulation program has been studied to predict whether or not combustion. The results from numerical prediction for the basic, cylinder averaged quantities such as the cylinder pressure and the heat release showed excellent with the experimental data.

• 한국추진공학회지
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• 제7권2호
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• pp.44-53
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• 2003

KSR-III의 추진시스템 종합성능시험과 단인증시험을 위한 수직형 연소시험시설이 구축되었다. 이러한 시험은 발사체에 준하는 단품을 사용하는 시험으로, 상대적으로 낮은 수준의 안전율 하에서 시험이 진행되게 된다. 이에 연소시험 안전대책의 하나로 엔진부에 대한 비상정지 시스템이 검토되었으며, 정확하고 빠른 판단을 위하여 연소실 압력과 가속도신호를 사용하는 비상정지 시스템이 구축되었다. 이러한 측정변수를 통하여 점화지연 및 실패, 소화, 추진제 공급상태, 불안정 연소, 구조물 과도진동 등을 감시할 수 있었으며, 이상 상황인지 후 빠르게 시험을 중단할 수 있었다. 이처럼 빠른 판단과 후속조치로 시험의 안전을 확보할 수 있었으며, 목적한 개발시험을 안전하게 마칠 수 있었다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.1084-1087
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• 2017

액체로켓에서 엔진의 시동은 산화제와 연료를 연소기에 매우 짧은 시간의 차를 두고 주입하여야 하며, 이때 주입시간의 간격, 점화기 작동 지연 등은 방대한 량의 추진제 혼합물에 에너지를 인가함으로서 대형 폭발로 이어질 수 있는 상황이 된다. 그러므로 각 추진제의 천이특성과 연소기 또는 가스발생기의 유입 시점을 측정하는 것은 매우 중요하며, 상대적으로 느린 응답 특성을 갖는 정압으로는 유입 시점을 관측하기에는 어려움이 많으므로 추진제 유로를 따라 동압을 측정하여 보다 정확한 유입시점을 찾을 수 있었다.

• 한국연소학회지
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• 제22권1호
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• pp.8-13
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• 2017

Ignition delay time of methane/oxygen mixture is measured experimentally with the shock tube in order to obtain the data for high pressure conditions where gas turbines and internal combustion engines are operating. The shock tube experiment is validated first over the temperature range of 1400-2000 K at 10 bar and with the various equivalence ratios of 0.5, 1 and 2. The measured ignition delays are compared with the data from the literatures. And then, experiments are conducted for non-explored conditions, i.e., at 40 bar and with the equivalence ratio of 1.5. The present experimental data show a good agreement with the available ones from the literatures and reasonable dependence on pressure and equivalence ratio. In addition, the effects of the temperature and equivalence ratio on ignition delay time are analyzed.

• 한국자동차공학회논문집
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• 제2권6호
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• pp.102-109
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• 1994

As a fundamental study to apply high pressure injection system to direct injection diesel engine, fuel injection system and constant volume combustion chamber were made and the behaviors of evaporating spray with the variation of injection pressure and the ambient gas temperature were observed by using high speed camera, and the combusion characteristics with the variation of injection pressure and A/F ratio were analyzed. As injection pressure increases, spray tip penetration and spray angle increase and, as a results spray volume increases. This helps an uniform mixing of fuel and air. Spray liquid core length decreases as ambient gas temperature increases, while it decreases as injection pressure increases but the effect of ambient gas temperature is dorminant. As injection pressure increases, ignition delay is shortened and combustion rate being raised, maximum heat release rate increases. It become clear that High injection pressure has high level of potential to improve the performance of DI-diesel engine.

• 한국자동차공학회논문집
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• 제21권2호
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• pp.37-44
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• 2013

Generally, a reduced chemical mechanism of n-heptane is used as chemical fuel of a 3-D diesel engine simulation because diesel fuel consists of hundreds of chemical components and various chemical classes so that it is very complex and large to use for the calculation. However, the importance of fuel in a 3-D simulation increases because detailed fuel characteristics are the key factor in the recent engine research such as homogeneous charged compression ignition engine. In this study, normal paraffin, iso paraffin and aromatics were selected to represent diesel characteristics and n-dodecane was used as a representative normal paraffin to describe the heavy molecular weight of diesel oil (C10~C20). Reduced kinetics of iso-octane and toluene which are representative species of iso paraffin and aromatics respectively were developed in the previous study. Some species were selected based on the sensitivity analysis and a mechanism was developed based on the general oxidation scheme. The ignition delay times, maximum pressure and temperature of the new reduced n-dodecane chemical mechanisms were well matched to the detailed mechanism data.

• 한국추진공학회지
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• 제17권4호
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• pp.73-80
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• 2013

장거리 극초음속 비행체에 적용 가능한 유일한 냉각방안으로 알려져 있는 흡열연료 적용기술을 개발하기 위하여 흡열반응에 의해 분해된 연료의 분사 및 연소특성에 대한 연구사례를 살펴보았다. 흡열반응을 거친 연료가 연소실에 분사될 때 처해지는 초임계 상태의 분사 특성, 초임계 연료가 초음속 유동장에 분사될 때의 공기혼합 특성 등에 관한 연구사례를 살펴보았고, 연소특성으로서 점화지연시간 및 화염전파 속도에 미치는 영향, 초음속 연소실에서 연소될 때의 연소효율 상승 연구사례 등을 살펴보았다. 국내에서 수행된 흡열연료 관련 연구동향을 살펴보았다.

• 한국안전학회지
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• 제36권3호
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• pp.1-6
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• 2021

Hydrogen is considered a cleaner energy source than fossil fuels. As a result, the use of hydrogen in daily life and economic industries is expected to increase. However, the use of hydrogen energy is currently limited because of safety issues. The rate of combustion of the hydrogen mixture is about seven times higher than that of hydrocarbon fuels. The hydrogen mixture is highly flammable and has a low minimum ignition energy. Therefore, it presents considerable risks for fire and explosions in all areas of hydrogen manufacturing, transportation, storage, and use. In this study, the auto-ignition characteristics of hydrogen were investigated numerically for diluted hydrogen mixtures. Auto-ignition temperature, a critical property predicting the fire and explosion risk in hydrogen combustion, was determined in well-stirred reactors. When N₂ and CO₂ were used to dilute the hydrogen/air mixture, the ignition delay time increased with increasing dilution ratios in both cases. The CO₂-diluted mixtures exhibited a longer ignition delay than the N₂-diluted mixtures. We also confirmed that lower initial ignition temperatures increased the ignition delay times at 950 K and above. Overall, the auto-ignition characteristics, such as the concentrations of participating species and ignition delay times, were primarily affected by the initial temperature of the mixture.

• 한국안전학회지
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• 제37권6호
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• pp.18-24
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• 2022

Hydrogen is a clean fuel and is used in many applications in power systems such as fuel cells. It has unique properties such as wide flammability, high burning velocity, and difficulty to liquefy, which lead to critical safety issues. Fire and explosion are the most frequently occurring accidents and one of the major reasons is autoignition. In the ignition process, the chemistry of hydrogen combustion depends mainly on radical pools, and the temperature at which chain-branching and terminating rates are equal is called the crossover temperature. This study addresses the homogeneous autoignition of diluted hydrogen-air mixtures to investigate the effects of dilution on the crossover temperature to prevent explosions in the future. The new criterion for crossover temperature is introduced by only hydrogen radicals to adjust more simply. The detailed calculations indicate that the crossover temperatures are low at high dilutions of carbon dioxide and nitrogen because the concentrations of active radicals are reduced when an inert gas is added. This result is expected to contribute to hydrogen safety and realize a hydrogen society in the future.