Experimental and computational study of soot formation under diesel engine conditions

Past research has shown that during diesel combustion, soot is formed in local premixed fuel-rich regions. This project focuses on the fundamentals soot formation under fuel-rich conditions similar to those in diesel engine operation. Since these conditions cannot be easily reproduced in typical laboratory scale experiments, such as flat-flame burners, and since diesel engine data are difficult to interpret because of uncertainty in the local charge composition and thermal state, a new rapid compression machine (RCM) was built to study the phenomenon. The RCM provides a well-controlled and uniform engine-like thermal environment, where mixing and chemistry are decoupled. Fuel-rich mixtures of n-butane and air were primarily used in this study; aromatics, oxygenates and cetane improvers completed the test matrix. Line-of-sight absorption technique was used to investigate the details of soot evolution. The primary data set consisted of soot volume loading history for selected fuels at various equivalence ratios, temperatures and pressures. Based on existing sub-models, a detailed chemical kinetic calculation leading to soot particles was per- formed to study the relative importance of the underlying chemistry. The results show that the initial soot volume grows exponentially with time, reflecting an "autocatalytic" mechanism. The growth rate depends strongly on temperature and pressure. The lower rates observed for richer mixtures can be attributed to lower temperatures after the end of the main heat release process, when most of the soot is formed. Soot yield increases steadily with fuel-air equivalence ratio and depends on fuel structure. Toluene addition to n-butane increases the final soot yield at constant fuel-air equivalence ratio (-1%/1% toluene by mol) but not at constant C/O ratio.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2004

Author dc:creator

• Kitsopanidis, Ioannis, 1975-

Advisor dc:contributor.advisor

• Wai. K. Cheng.

• Mechanical 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/1721.1/30330

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/30330