Effect of oxygen content on n-heptane auto-ignition characteristics in a HCCI engine

Zhijun Wu, Zhe Kang, Jun Deng, Zongjie Hu and Liguang Li

Applied Energy, 2016, vol. 184, issue C, 594-604

Abstract: To take maximum advantage of the high efficiency of homogeneous charge compression ignition combustion mode and internal combustion Rankine cycle concept, in this study, the n-heptane auto-ignition characteristics have been investigated using a compression ignition internal combustion Rankine cycle engine test bench and a zero-dimensional thermodynamic model coupled with a detailed kinetic model. The n-heptane auto-ignition process shows that under both air and oxygen intake, a typical two-stage combustion in which oxygen enrichment has very minor effects on the n-heptane high temperature reaction. The higher specific heat capacity of oxygen compared with nitrogen leads to an overall increased specific heat capacity, which lowers the in-cylinder temperature during compression stroke, thereby delaying the low temperature reaction initial timing. The higher oxygen content also improves the H-atom abstraction, first O2 addition, second O2 addition and peroxyalkylhydroperoxide isomerization, thereby improving the overall reaction rate and the heat release fraction of low temperature reaction. As a result, the in-cylinder temperature at the end of low temperature reaction also increases, thereby shortening significantly the negative temperature coefficient duration compared with a combustion cycle using air as oxidizer.

Keywords: Homogeneous charge compression ignition; n-Heptane; Oxy-fuel; Chemical reaction kinetics (search for similar items in EconPapers)
Date: 2016
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Citations: View citations in EconPapers (5)

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DOI: 10.1016/j.apenergy.2016.10.050

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