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dc.contributor.authorLuong, Minh Bau
dc.contributor.authorSankaran, Ramanan
dc.contributor.authorYu, Gwang Hyeon
dc.contributor.authorChung, Suk-Ho
dc.contributor.authorYoo, Chun Sang
dc.date.accessioned2017-07-03T08:05:53Z
dc.date.available2017-07-03T08:05:53Z
dc.date.issued2017-06-10
dc.identifier.citationLuong MB, Sankaran R, Yu GH, Chung SH, Yoo CS (2017) On the effect of injection timing on the ignition of lean PRF/air/EGR mixtures under direct dual fuel stratification conditions. Combustion and Flame 183: 309–321. Available: http://dx.doi.org/10.1016/j.combustflame.2017.05.023.
dc.identifier.issn0010-2180
dc.identifier.doi10.1016/j.combustflame.2017.05.023
dc.identifier.urihttp://hdl.handle.net/10754/625140
dc.description.abstractThe ignition characteristics of lean primary reference fuel (PRF)/air/exhaust gas recirculation (EGR) mixture under reactivity-controlled compression ignition (RCCI) and direct duel fuel stratification (DDFS) conditions are investigated by 2-D direct numerical simulations (DNSs) with a 116-species reduced chemistry of the PRF oxidation. The 2-D DNSs of the DDFS combustion are performed by varying the injection timing of iso-octane (i-C8H18) with a pseudo-iso-octane (PC8H18) model together with a novel compression heating model to account for the compression heating and expansion cooling effects of the piston motion in an engine cylinder. The PC8H18 model is newly developed to mimic the timing, duration, and cooling effects of the direct injection of i-C8H18 onto a premixed background charge of PRF/air/EGR mixture with composition inhomogeneities. It is found that the RCCI combustion exhibits a very high peak heat release rate (HRR) with a short combustion duration due to the predominance of the spontaneous ignition mode of combustion. However, the DDFS combustion has much lower peak HRR and longer combustion duration regardless of the fuel injection timing compared to those of the RCCI combustion, which is primarily attributed to the sequential injection of i-C8H18. It is also found that the ignition delay of the DDFS combustion features a non-monotonic behavior with increasing fuel-injection timing due to the different effect of fuel evaporation on the low-, intermediate-, and high-temperature chemistry of the PRF oxidation. The budget and Damköhler number analyses verify that although a mixed combustion mode of deflagration and spontaneous ignition exists during the early phase of the DDFS combustion, the spontaneous ignition becomes predominant during the main combustion, and hence, the spread-out of heat release rate in the DDFS combustion is mainly governed by the direct injection process of i-C8H18. Finally, a misfire is observed for the DDFS combustion when the direct injection of i-C8H18 occurs during the intermediate-temperature chemistry (ITC) regime between the first- and second-stage ignition. This is because the temperature drop induced by the direct injection of i-C8H18 impedes the main ITC reactions, and hence, the main combustion fails to occur.
dc.description.sponsorshipThis research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (No. 2015R1A2A2A01007378). This research used the resources of the KAUST Supercomputing Laboratory and UNIST Supercomputing Center. The work at ORNL used resources of the Oak Ridge Leadership Computing Facility, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725.
dc.publisherElsevier BV
dc.relation.urlhttp://www.sciencedirect.com/science/article/pii/S0010218017301980
dc.rightsNOTICE: this is the author’s version of a work that was accepted for publication in Combustion and Flame. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Combustion and Flame, 9 June 2017. DOI: 10.1016/j.combustflame.2017.05.023. © 2017. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
dc.subjectDirect numerical simulation (DNS)
dc.subjectHomogeneous-charge compression ignition (HCCI)
dc.subjectDirect dual fuel stratification (DDFS)
dc.subjectReactivity controlled compression ignition (RCCI)
dc.subjectPrimary reference fuel (PRF)
dc.titleOn the effect of injection timing on the ignition of lean PRF/air/EGR mixtures under direct dual fuel stratification conditions
dc.typeArticle
dc.contributor.departmentClean Combustion Research Center
dc.contributor.departmentMechanical Engineering Program
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Division
dc.identifier.journalCombustion and Flame
dc.eprint.versionPost-print
dc.contributor.institutionDepartment of Mechanical Engineering, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
dc.contributor.institutionNational Center for Computational Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
kaust.personChung, Suk-Ho


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