TY - JOUR
T1 - Experimental and numerical study on soot formation and oxidation by using diesel fuel in constant volume chamber with various ambient oxygen concentrations
AU - Bi, Xiaojie
AU - Liu, Haifeng
AU - Huo, Ming
AU - Shen, Cai
AU - Qiao, Xinqi
AU - Lee, Chia Fon F.
N1 - Funding Information:
The authors would like to acknowledge the financial supports to the research provided by National Natural Science Found of China (NSFC) through its Project of 51206120 and by the U.S. Department of Energy (DOE) sponsored Graduate Automotive Technology Education (GATE) Centers of Excellence under Grant DE-FG26-05NT42622 .
PY - 2014/8
Y1 - 2014/8
N2 - The study on effects of exhaust gas recirculation (EGR) on soot behavior is very important to reduce soot emissions and control the low temperature combustion process in diesel engines. In this work, high time-resolved quantitative soot measurements were experimented on a constant volume chamber by using European low-sulfur diesel fuel at three ambient oxygen concentrations (21%, 18%, 15%). Meanwhile, an improved semi-empirical soot model was coupled into computational fluid dynamics (KIVA-3V Release 2) code for in-depth understanding the soot formation and oxidation processes. Results demonstrated that numerical results of the improved semi-empirical soot model showed good agreement with experimental data in the whole processes of soot formation/oxidation and soot distribution under different oxygen concentrations. The mass concentration of acetylene, soot precursor species and soot mass initially increased with decreasing ambient oxygen concentrations from 21% to 15% and then began to decrease at 12% oxygen, while OH radicals reduced monotonically from 21% oxygen to 12%. At 12% oxygen, the concentrations of local rich sooty zone, acetylene and soot precursor species were as high as those under higher oxygen concentrations, but the total area of soot zone shrank remarkably at 12% oxygen. Compared to 21% ambient oxygen concentration, both soot formation and oxidation rates were increased under 18% oxygen, while the higher soot mass under 18% oxygen was the result of stronger soot formation mechanism. At 15% oxygen, both soot formation and oxidation rates were reduced and the maximum peak of soot mass concentration was caused by the suppressed oxidation mechanism. At 12% oxygen, reaction rates of soot formation and oxidation dropped to the very low level and the reduction in soot mass concentration and number density were achieved. Finally, it could be concluded that the retarded and reduced soot mass concentration at low ambient oxygen was the result of suppressed soot inception reaction from precursor species.
AB - The study on effects of exhaust gas recirculation (EGR) on soot behavior is very important to reduce soot emissions and control the low temperature combustion process in diesel engines. In this work, high time-resolved quantitative soot measurements were experimented on a constant volume chamber by using European low-sulfur diesel fuel at three ambient oxygen concentrations (21%, 18%, 15%). Meanwhile, an improved semi-empirical soot model was coupled into computational fluid dynamics (KIVA-3V Release 2) code for in-depth understanding the soot formation and oxidation processes. Results demonstrated that numerical results of the improved semi-empirical soot model showed good agreement with experimental data in the whole processes of soot formation/oxidation and soot distribution under different oxygen concentrations. The mass concentration of acetylene, soot precursor species and soot mass initially increased with decreasing ambient oxygen concentrations from 21% to 15% and then began to decrease at 12% oxygen, while OH radicals reduced monotonically from 21% oxygen to 12%. At 12% oxygen, the concentrations of local rich sooty zone, acetylene and soot precursor species were as high as those under higher oxygen concentrations, but the total area of soot zone shrank remarkably at 12% oxygen. Compared to 21% ambient oxygen concentration, both soot formation and oxidation rates were increased under 18% oxygen, while the higher soot mass under 18% oxygen was the result of stronger soot formation mechanism. At 15% oxygen, both soot formation and oxidation rates were reduced and the maximum peak of soot mass concentration was caused by the suppressed oxidation mechanism. At 12% oxygen, reaction rates of soot formation and oxidation dropped to the very low level and the reduction in soot mass concentration and number density were achieved. Finally, it could be concluded that the retarded and reduced soot mass concentration at low ambient oxygen was the result of suppressed soot inception reaction from precursor species.
KW - Constant volume chamber
KW - Diesel combustion
KW - High time-resolved quantitative soot measurements
KW - Semi-empirical soot model
KW - Soot formation/oxidation
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U2 - 10.1016/j.enconman.2014.04.023
DO - 10.1016/j.enconman.2014.04.023
M3 - Article
AN - SCOPUS:84899657436
SN - 0196-8904
VL - 84
SP - 152
EP - 163
JO - Energy Conversion and Management
JF - Energy Conversion and Management
ER -