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RISS 인기검색어
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- 저자 : Kookeui Hong (검색결과 3 건)
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Jeongwoo Lee,Kookeui Hong,최승목,Seongeun Yu,최회명,민경덕 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.4
As vehicle emissions regulations have become stricter, improving injection strategies and using high EGR rates has become important to reduce engine-out emissions. Previous research has found that, a multiple injection strategy with a pilot or post injection has the potential to improve the distribution of the air-fuel mixture or oxidation. Thus, it is important to determine the effect of multiple injection strategies on the engine-out emissions. Especially, since the latest diesel engines have used high EGR rates to reduce NOx emission, the target of emissions is different from that of moderate EGR rate condition. Under heavy EGR rate condition, it is needed to improve combustion efficiency by reduction of CO and THC emissions. Therefore, in the first research as part 1, the effects of pilot injection on the engine-out emissions were systemically evaluated for two different EGR rate conditions (30 % and 60 %). The characteristics of the pilot injection were different between the two EGR rate conditions because the behavior of diesel combustion is significantly different when the EGR rate is changed. This research condition was investigated using varying injection parameters such as the timing and quantity of the pilot injection. The results show that each different pilot injection strategy was suggested between two EGR rate conditions to reduce engine-out emissions. Under moderate EGR rate condition, very earlier pilot SOI with large amount has the potential to reduce NOx and PM emissions simultaneously. On the other hand, under heavy EGR rate condition, the closest pilot SOI to main SOI has the potential to reduce CO and THC emissions.
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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%).
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