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연료 혼합비율 및 산소농도가 노말데케인/에탄올 혼합연료의 점화특성에 미치는 영향
오채호(Chae Ho Oh),강기중(Ki Joong Kang),최경민(Gyung Min Choi) 대한기계학회 2017 大韓機械學會論文集B Vol.41 No.11
본 연구는 대체연료 개발 및 국제환경규제에 대응하기 위하여, 노말데케인과 에탄올 혼합연료의 조성 및 온도 변화가 자착화 특성에 미치는 영향을 수치적으로 해석하였다. 해석용 프로그램으로는 CHEMKIN-PRO를 사용하였고, 반응모델은 LLNL모델을 이용하였다. 수치해석 결과를 통해 저온 연소반응이 일어나는 1000K 이하에서는 에탄올의 몰 비율이 증가함에 따라 점화지연 시간이 증가하는 현상을 확인하였다. 에탄올의 높은 옥탄가로 인해 에탄올의 높은 비율은 점화를 일으키는 OH라디칼의 농도증가를 지연시키기 때문이다. 배기가스 재순환을 적용하기 위해 혼합연료에 산소농도를 변화하여 수치해석을 하였다. 산소농도가 감소함에 따라 전체 점화지연시간은 증가하게 되고, 이는 질소가스가 연소실 내에 열부하로 작용하기 때문이다. To cope with the development of alternative fuels and international environmental regulations, this study provides a numerical analysis of the effects of composition and temperature changes of n-decane and ethanol on auto-ignition characteristics. CHEMKIN-PRO is used as the analysis program and the LLNL model is used as the reaction model. The numerical results show that the ignition delay time increases as the mole fraction of ethanol increases for temperatures below 1000 K, where low temperature reactions occur. Because of the high octane number of ethanol, the high percentage of ethanol delays the increase in the concentration of OH radicals that cause ignition. The oxygen concentration in the mixture is changed to apply the exhaust gas recirculation and a numerical analysis is then performed. As the oxygen concentration decreases, the total ignition delay time increases because the nitrogen gas acts as a thermal load in the combustion chamber.
강기중,오채호,심태영,송재혁,류승협,최경민,김덕줄 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.7
The autoignition characteristics of n-heptane/ethanol were investigated both experimentally and numerically. The effects of nitrogen dilution and exhaust gas recirculation on the autoignition characteristics were evaluated. A rapid compression machine was employed to measure ignition delay times of blended fuels. A numerical study on the ignition delay time was performed using the CHEMKIN-PRO software to calculate ignition delay time and predict the chemical species in the combustion process. The results revealed that the ignition delay time increased with increasing nitrogen dilution rate due to the thermal load effect of nitrogen. The oxidation reaction of n-heptane in a low temperature regime was limited with increasing nitrogen dilution rate. The ignition delay time sharply decreased with exhaust gas recirculation because of the intermediate species in the exhaust gas. Exhaust gas recirculation reduced first ignition delay dramatically. However, the time interval between the first and main ignition increased with increased exhaust gas recirculation.
강기중,심태영,오채호,최경민,김덕줄 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.3
The autoignition characteristics of n-heptane/hydrogen were investigated numerically. The effects of the temperature, fuel compositions and Exhaust gas recirculation (EGR) on the autoignition characteristics were evaluated. The numerical study on the ignition delay time was performed using the CHEMKIN-PRO software to calculate ignition delay time and predict the chemical species in the combustion process. The results revealed that ignition delay time decreased with an increase in the hydrogen fraction in the mixture in low temperature regime, but the opposite behavior observed in high temperature regime. The oxidation reaction of n-heptane in low temperature regime is limited with increasing mole fraction of hydrogen in blended fuel. Thus, cool flame which is characteristics of n-heptane is weakened. As consumption rate of n-heptane and temperature are decreased, total reactivity is decreased. The ignition delay time sharply decrease with EGR due to intermediate species in the exhaust gas.