Fuel effects in homogeneous charge compression ignition (HCCI) engines

Homogenous-charge, compression-ignition (HCCI) combustion is a new method of burning fuel in internal combustion (IC) engines. In an HCCI engine, the fuel and air are premixed prior to combustion, like in a spark-ignition (SI) engine. However, rather than using a spark to initiate combustion, the mixture is ignited through compression only, as in a compression-ignition (CI) engine; this makes combustion in HCCI engines much more sensitive to fuel chemistry than in traditional IC engines. The union of SI- and CI-technologies gives HCCI engines substantial efficiency and emissions advantages. However, one major challenge preventing significant commercialization of HCCI technology is its small operating range compared to traditional IC engines. This project examined the effects of fuel chemistry on the size of the HCCI operating region, with an emphasis on the low-load limit (LLL) of HCCI operability. If commercialized, HCCI engines will have to operate using standard commercial fuels. Therefore investigating the impact of fuel chemistry variations in commercial gasolines on the HCCI operability limits is critical to determining the fate of HCCI commercialization. To examine these effects, the operating ranges of 12 gasolines were mapped in a naturally-aspirated, single-cylinder HCCI engine, which used negative valve overlap to induce HCCI combustion. The fuels were blended from commercial refinery streams to span the range of market-typical variability in aromatic, ethanol, and olefin concentrations, RON, and volatility. The results indicated that all fuels achieved nearly equal operating ranges. The LLL of HCCI operability was completely insensitive to fuel chemistry, within experimental measurement error. The high-load limit showed minor fuel effects, but the trends in fuel performance were not consistent across all the speeds studied. These results suggest that fuel sensitivity is not an obstacle to auto-makers and/or fuel companies to introducing HCCI technology.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Chemical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2009

Author dc:creator

• Angelos, John P. (John Phillip)

Advisor dc:contributor.advisor

• William H. Green, Jr.

• Chemical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/50615

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/50615