지원사업
학술연구/단체지원/교육 등 연구자 활동을 지속하도록 DBpia가 지원하고 있어요.
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연구자들이 자신의 연구와 전문성을 널리 알리고, 새로운 협력의 기회를 만들 수 있는 네트워킹 공간이에요.
논문 기본 정보
- 자료유형
- 학술대회자료
- 저자정보
- 발행연도
- 2011.12
- 수록면
- 273 - 283 (11page)
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초록· 키워드
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The effect of thermal stratification, spark-ignition, and turbulence on the ignition of a lean homogeneous iso-octane/air mixture at constant volume and high pressure is investigated by direct numerical simulations (DNS) with a new 99-species reduced kinetic mechanism developed for very lean mixtures from the detailed mechanism (Mehl et al., 4th European Combustion Meeting, Vienna, Austria, 2009). Two-dimensional DNS are performed in a fixed volume with two-dimensional isotropic velocity spectrums, temperature fluctuations, and ignition source superimposed on the initial scalar fields. The influence of variations in the initial temperature field imposed by changing the variance of temperature, the ignition-timing by changing the time at which ignition source is superimposed, and the turbulence intensity and length scale on ignition of a lean iso-octane/air mixture is elucidated. The mean heat release rate increases more slowly and ignition delay decreases with increasing thermal stratification under homogeneous charge compression-ignition (HCCI) condition since the present mean temperature lies far outside of the negative temperature coefficient (NTC) regime. The spark-ignition induces relatively short ignition delay under spark-assisted compression ignition (SACI) condition while slightly spreading out the mean heat release rate. For SACI combustion, high turbulence intensity decreases the ignition delay more by increasing turbulent flame area. Displacement speed and Damkohler number analyses reveal that the high degree of thermal stratification induces deflagration at the reaction fronts, and hence, the mean heat release rate is smoother subsequent to thermal runaway occurring at the highest temperature regions in the domain. For SACI combustion, the heat release occurs solely by deflagration prior to the occurrence of the maximum heat release and subsequently by the mixed mode of deflagration and spontaneous ignition. These results suggest that the thermal stratification is more effective for smooth operation of HCCI engines and the spark-ignition can precisely control the ignition timing for SACI combustion.
목차
ABSTRACT
1. Introduction
2. iso-Octane/air reduced mechanism
3. Numerical method and initial conditions
4. Results - effect of temperature fluctuations
5. Results - effect of spark-ignition timing
6. Results - effect of turbulence
7. Conclusions
Acknowledgement
References
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UCI(KEPA) : I410-ECN-0101-2013-431-003274780