Tailoring charge reactivity using in-cylinder generated reformate for gasoline compression ignition strategies

Isaac W. Ekoto, Benjamin M. Wolk, William Northrop, Nils Hansen, Kai Moshammer

Research output: Chapter in Book/Report/Conference proceedingConference contribution

3 Scopus citations

Abstract

In-cylinder reforming of injected fuel during an auxiliary negative valve overlap (NVO) period can be used to optimize main-cycle combustion phasing for low-load Low-Temperature Gasoline Combustion, where highly dilute mixtures can lead to poor combustion stability. The objective of this work is to examine the effects of reformate composition on main-cycle engine performance for a research gasoline. A custom alternatefire sequence with nine pre-conditioning cycles was used to generate a common exhaust temperature and composition boundary condition for a cycle-of-interest. Performance metrics such as main-period combustion stability and total cycle efficiency were collected for these custom cycles. The NVOproduced reformate stream was also separately collected using a dump valve apparatus and characterized in detail using both gas chromatography and photoionization mass spectroscopy. To facilitate gas sample analysis, sampling experiments were conducted using a five-component gasoline surrogate (isooctane, n-heptane, ethanol, 1-hexene, and toluene) that matched the molecular composition, 50% boiling point, and ignition characteristics of the research gasoline. For the gasoline, it was found that the most advanced NVO start-of-injection (SOI) led to the most advanced main-cycle 10% burn angle. The effect was more pronounced as the fraction of total fuel injected in the NVO period increased. With the most retarded NVO SOI, shorter residence times and piston spray impingement limited the opportunity for injected fuel decomposition. For the gasoline surrogate, the most advanced NVO SOI had reduced reactivity relative to more intermediate NVO SOI, which was attributed to rapid in-cylinder mixing that led to a large amount of fuel quench in the piston crevice. For all NVO periods, combustion phasing advanced as the mainperiod fueling decreased. Slower kinetics for leaner mixtures were offset by a combination of increased bulk-gas temperature from higher charge specific heat ratios and increased fuel reactivity due to higher charge reformate fractions.

Original languageEnglish (US)
Title of host publicationASME 2016 Internal Combustion Engine Fall Technical Conference, ICEF 2016
PublisherAmerican Society of Mechanical Engineers
ISBN (Electronic)9780791850503
DOIs
StatePublished - Jan 1 2016
EventASME 2016 Internal Combustion Engine Fall Technical Conference, ICEF 2016 - Greenville, United States
Duration: Oct 9 2016Oct 12 2016

Other

OtherASME 2016 Internal Combustion Engine Fall Technical Conference, ICEF 2016
Country/TerritoryUnited States
CityGreenville
Period10/9/1610/12/16

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