TY - JOUR
T1 - Effect of injection timing on knock combustion and pollutant emission of heavy-duty diesel engines at low temperatures
AU - Wu, Han
AU - Dong, Xinyi
AU - Shi, Zhicheng
AU - Li, Haiying
AU - Cao, Weiren
AU - Zhang, Lu
AU - Bo, Yaqing
AU - Li, Xiangrong
N1 - Publisher Copyright:
© 2022 Elsevier Ltd
PY - 2022/10
Y1 - 2022/10
N2 - The knock combustion and pollutant emission of heavy-duty diesel engines at low temperatures are still unclear, especially under different injection timings. Therefore, this study illustrates the above issues through CONVERGE simulation. The results show that with the start of injection (SOI) sweeps from −7°CA to −32°CA, a large amount of liquid-phase fuel adheres to the wall, and the wet-wall ratio of fuel at SOI = −32°CA is as high as nearly 30%. The fuel film evaporates slowly, coupled with the effect of low temperature on chemical reactions, the high-temperature ignition (HTI) is delayed seriously until the end of injection. The amount of premixed mixture formed during long ignition delay is significantly increased, but its uniformity is better and the concentration is more suitable for ignition. Once HTI is triggered, high-frequency and strong pressure oscillation occurs in the cylinder, and the maximum oscillation amplitude is as high as nearly 10 MPa, far exceeding the threshold of destructive knock combustion. Delayed fuel injection can effectively alleviate the above problems, such as the best when the SOI in this study is −17°CA. In addition, HC emissions are positively correlated with the amount of fuel film, but the trend of CO quantity with injection timing shows the opposite result. NOx emission increases as the injection timing advances, while soot is the opposite, because the mixture concentration is leaner at the earlier SOI and the expanded high-temperature region leads to an accelerated oxidation rate of soot.
AB - The knock combustion and pollutant emission of heavy-duty diesel engines at low temperatures are still unclear, especially under different injection timings. Therefore, this study illustrates the above issues through CONVERGE simulation. The results show that with the start of injection (SOI) sweeps from −7°CA to −32°CA, a large amount of liquid-phase fuel adheres to the wall, and the wet-wall ratio of fuel at SOI = −32°CA is as high as nearly 30%. The fuel film evaporates slowly, coupled with the effect of low temperature on chemical reactions, the high-temperature ignition (HTI) is delayed seriously until the end of injection. The amount of premixed mixture formed during long ignition delay is significantly increased, but its uniformity is better and the concentration is more suitable for ignition. Once HTI is triggered, high-frequency and strong pressure oscillation occurs in the cylinder, and the maximum oscillation amplitude is as high as nearly 10 MPa, far exceeding the threshold of destructive knock combustion. Delayed fuel injection can effectively alleviate the above problems, such as the best when the SOI in this study is −17°CA. In addition, HC emissions are positively correlated with the amount of fuel film, but the trend of CO quantity with injection timing shows the opposite result. NOx emission increases as the injection timing advances, while soot is the opposite, because the mixture concentration is leaner at the earlier SOI and the expanded high-temperature region leads to an accelerated oxidation rate of soot.
KW - Heavy-duty diesel engine
KW - Injection timing
KW - Knock combustion
KW - Low temperature
KW - Pollutant emission
KW - Spray impingement
UR - http://www.scopus.com/inward/record.url?scp=85133204464&partnerID=8YFLogxK
U2 - 10.1016/j.chemosphere.2022.135519
DO - 10.1016/j.chemosphere.2022.135519
M3 - Article
C2 - 35777540
AN - SCOPUS:85133204464
SN - 0045-6535
VL - 305
JO - Chemosphere
JF - Chemosphere
M1 - 135519
ER -