http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
최회명,이정우,Kookeui Hong,Sangyul Lee,최승목,Seongeun Yu,민경덕 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.7
To draw a comparison of the effect of multiple injection strategy on the engine-out emissions under two different EGR rate conditions,the effect of pilot injection on emissions and combustion was evaluated and discussed in part 1. Thus, in the second research as part 2, the effects of post injection on the engine-out emissions were systemically evaluated for two different EGR rate conditions (30 % and 60 %). Since the behavior of diesel combustion is significantly different as EGR rate is changed, the characteristics of post injection was different between two EGR rate conditions. This research was investigated as varying injection parameters such as the timing and quantity of the post injection. The results show that the close post injection with injection interval as 10 degree has the potential to reduce PM emission,regardless of EGR rate. However, the reason of reduction of PM emission is different for each case. For a moderate EGR rate condition,close post injection with interval 10 degree enhances the fuel at bottom of bowl. Thus, the distribution of fuel can be improved. On the other hand, for a heavy EGR rate condition, close post injection with interval 10 degree has the charge cooling effect to prolong the ignition delay, rather than well-matched injection targeting. Especially, there is an effect to oxidize PM emission under moderate EGR rate condition as post injection is applied. However, post injection for late cycle of combustion under heavy EGR rate condition does not oxidize PM emission due to low oxygen concentration (~ 10%).
최회명(Hoimyung Choi),김용태(Yongtae Kim),민경덕(Kyoungdoug Min) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
A new stratified combustion model for Direct-Injection Spark-Ignition engines is presented, which considers the secondary diffusion flame in the burned region and the effect of mixture fraction fluctuation on the laminar burning velocity.<br/> For the primary flame propagation, a Flame Area Evolution (FAE) model was adopted and extended to partially premixed combustion by implementing the variance of mixture fraction and the concept of probability density function. And a 2-step reaction mechanism of water-gas shift reaction and hydrogen oxidation was applied to the diffusion flame with the equilibrium concentration of CO, CO₂ H₂ and H₂O in the burned gas. In addition to these models, a new correlation of the laminar burning velocity was adopted. which can be applicable to much wider range of equivalence ratio, pressure and temperature than the other models. The direct-injection gasoline spray model was implemented in order to form a stratified Fuel-air mixture.<br/> Under stratified charged condition. 3-dimensional simulation was performed in a Direct-Injection Spark-Ignition engine geometry by using STAR-CD. The simulation results can be useful to understand the combustion process of DISI engine. And. the present model proves itself to be reasonable to simulate the characteristics of flame propagation, diffusion reaction, concentrations of products in burned region, and burned gas temperature.