Direct numerical simulations of ignition of a lean n-heptane/air mixture with temperature and composition inhomogeneities relevant to HCCI and SCCI combustion

Handle URI:
http://hdl.handle.net/10754/594228
Title:
Direct numerical simulations of ignition of a lean n-heptane/air mixture with temperature and composition inhomogeneities relevant to HCCI and SCCI combustion
Authors:
Luong, Minh Bau; Yu, Gwang Hyeon; Lu, Tianfeng; Chung, Suk-Ho ( 0000-0001-8782-312X ) ; Yoo, Chun Sang ( 0000-0003-1094-4016 )
Abstract:
The effects of temperature and composition stratifications on the ignition of a lean n-heptane/air mixture at three initial mean temperatures under elevated pressure are investigated using direct numerical simulations (DNSs) with a 58-species reduced mechanism. Two-dimensional DNSs are performed by varying several key parameters: initial mean temperature, T0, and the variance of temperature and equivalence ratio (T' and φ') with different T-φcorrelations. It is found that for cases with φ' only, the overall combustion occurs more quickly and the mean heat release rate (HRR) increases more slowly with increasing φ' regardless of T0. For cases with T' only, however, the overall combustion is retarded/advanced in time with increasing T' for low/high T0 relative to the negative-temperature coefficient (NTC) regime resulting from a longer/shorter overall ignition delay of the mixture. For cases with uncorrelated T-φfields, the mean HRR is more distributed over time compared to the corresponding cases with T' or φ' only. For negatively-correlated cases, however, the temporal evolution of the overall combustion exhibits quite non-monotonic behavior with increasing T' and φ' depending on T0. All of these characteristics are found to be primarily related to the 0-D ignition delays of initial mixtures, the relative timescales between 0-D ignition delay and turbulence, and the dominance of the deflagration mode during the ignition. These results suggest that an appropriate combination of T' and φ' together with a well-prepared T-φdistribution can alleviate an excessive pressure-rise rate (PRR) and control ignition-timing in homogeneous charge compression-ignition (HCCI) combustion. In addition, critical species and reactions for the ignition of n-heptane/air mixture through the whole ignition process are estimated by comparing the temporal evolution of the mean mass fractions of important species with the overall reaction pathways of n-heptane oxidation mechanism. The chemical explosive mode analysis (CEMA) verifies the important species and reactions for the ignition at different locations and times by evaluating the explosive index (EI) of species and the participation index (PI) of reactions. © 2015 The Combustion Institute.
KAUST Department:
Clean Combustion Research Center
Citation:
Luong MB, Yu GH, Lu T, Chung SH, Yoo CS (2015) Direct numerical simulations of ignition of a lean n-heptane/air mixture with temperature and composition inhomogeneities relevant to HCCI and SCCI combustion. Combustion and Flame 162: 4566–4585. Available: http://dx.doi.org/10.1016/j.combustflame.2015.09.015.
Publisher:
Elsevier BV
Journal:
Combustion and Flame
Issue Date:
Dec-2015
DOI:
10.1016/j.combustflame.2015.09.015
Type:
Article
ISSN:
0010-2180
Sponsors:
U.S. Department of Energy[DE-SC0008622]; Ulsan National Institute of Science and Technology[1.150033.01]; National Research Foundation of Korea[2015R1A2A2A01007378]
Appears in Collections:
Articles; Clean Combustion Research Center

Full metadata record

DC FieldValue Language
dc.contributor.authorLuong, Minh Bauen
dc.contributor.authorYu, Gwang Hyeonen
dc.contributor.authorLu, Tianfengen
dc.contributor.authorChung, Suk-Hoen
dc.contributor.authorYoo, Chun Sangen
dc.date.accessioned2016-01-19T14:43:51Zen
dc.date.available2016-01-19T14:43:51Zen
dc.date.issued2015-12en
dc.identifier.citationLuong MB, Yu GH, Lu T, Chung SH, Yoo CS (2015) Direct numerical simulations of ignition of a lean n-heptane/air mixture with temperature and composition inhomogeneities relevant to HCCI and SCCI combustion. Combustion and Flame 162: 4566–4585. Available: http://dx.doi.org/10.1016/j.combustflame.2015.09.015.en
dc.identifier.issn0010-2180en
dc.identifier.doi10.1016/j.combustflame.2015.09.015en
dc.identifier.urihttp://hdl.handle.net/10754/594228en
dc.description.abstractThe effects of temperature and composition stratifications on the ignition of a lean n-heptane/air mixture at three initial mean temperatures under elevated pressure are investigated using direct numerical simulations (DNSs) with a 58-species reduced mechanism. Two-dimensional DNSs are performed by varying several key parameters: initial mean temperature, T0, and the variance of temperature and equivalence ratio (T' and φ') with different T-φcorrelations. It is found that for cases with φ' only, the overall combustion occurs more quickly and the mean heat release rate (HRR) increases more slowly with increasing φ' regardless of T0. For cases with T' only, however, the overall combustion is retarded/advanced in time with increasing T' for low/high T0 relative to the negative-temperature coefficient (NTC) regime resulting from a longer/shorter overall ignition delay of the mixture. For cases with uncorrelated T-φfields, the mean HRR is more distributed over time compared to the corresponding cases with T' or φ' only. For negatively-correlated cases, however, the temporal evolution of the overall combustion exhibits quite non-monotonic behavior with increasing T' and φ' depending on T0. All of these characteristics are found to be primarily related to the 0-D ignition delays of initial mixtures, the relative timescales between 0-D ignition delay and turbulence, and the dominance of the deflagration mode during the ignition. These results suggest that an appropriate combination of T' and φ' together with a well-prepared T-φdistribution can alleviate an excessive pressure-rise rate (PRR) and control ignition-timing in homogeneous charge compression-ignition (HCCI) combustion. In addition, critical species and reactions for the ignition of n-heptane/air mixture through the whole ignition process are estimated by comparing the temporal evolution of the mean mass fractions of important species with the overall reaction pathways of n-heptane oxidation mechanism. The chemical explosive mode analysis (CEMA) verifies the important species and reactions for the ignition at different locations and times by evaluating the explosive index (EI) of species and the participation index (PI) of reactions. © 2015 The Combustion Institute.en
dc.description.sponsorshipU.S. Department of Energy[DE-SC0008622]en
dc.description.sponsorshipUlsan National Institute of Science and Technology[1.150033.01]en
dc.description.sponsorshipNational Research Foundation of Korea[2015R1A2A2A01007378]en
dc.publisherElsevier BVen
dc.subjectChemical explosive mode analysis (CEMA)en
dc.subjectDirect numerical simulation (DNS)en
dc.subjectHomogeneous-charge compression ignition (HCCI)en
dc.subjectNegative-temperature coefficient (NTC)en
dc.subjectStratified-charge compression ignition (SCCI)en
dc.titleDirect numerical simulations of ignition of a lean n-heptane/air mixture with temperature and composition inhomogeneities relevant to HCCI and SCCI combustionen
dc.typeArticleen
dc.contributor.departmentClean Combustion Research Centeren
dc.identifier.journalCombustion and Flameen
dc.contributor.institutionDepartment of Mechanical Engineering, Ulsan National Institute of Science and Technology, Ulsan, South Koreaen
dc.contributor.institutionDepartment of Mechanical Engineering, University of Connecticut, Storrs, CT, United Statesen
dc.contributor.institutionSchool of Mechanical and Nuclear Engineering, Ulsan National Institute of Science and Technology, Ulsan, South Koreaen
kaust.authorChung, Suk-Hoen
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