Diesel Combustion: An Integrated View Combining Laser Diagnostics, Chemical Kinetics, And Empirical Validation

Abstract

February 1999This is a preprint of a paper intended for publication in a journal or proceedings. Since changes may be made before publication, this preprint is made available with the understanding that it will not be cited or reproduced without the permission of the author. PREPRINTThis paper was prepared for submittal to the DISCLAIMER This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes. 1999-01- Charles K. WestbrookLawrence Livermore National Laboratory ABSTRACT This paper proposes a structure for the diesel combustion process based on a combination of previously published and new results. Processes are analyzed with proven chemical kinetic models and validated with data from production-like direct injection diesel engines. The analysis provides new insight into the ignition and particulate formation processes, which combined with laser diagnostics, delineates the twostage nature of combustion in diesel engines. Data are presented to quantify events occurring during the ignition and initial combustion processes that form soot precursors.A framework is also proposed for understanding the heat release and emission formation processes.

Chemical Kinetic Modeling Study of the Effects of Oxygenated Hydrocarbons on Soot Emissions from Diesel Engines

“…Diesel engine chemistry has been primarily an experimental subject, but the phenomenological model of Dec [15][16][17][18][19][20][21] has provided a framework within which focused computational studies can provide valuable insights. The present kinetic modeling analysis fits conveniently into Dec's framework, connecting the fuel vaporization and air entrainment processes with the soot growth period.…”

“…Therefore these incompletely oxidized species such as CO, H 2 and small, intermediate hydrocarbon species including acetylene, ethene, propene and others then react to produce soot [17][18][19] which is later consumed in a diffusion flame environment 19 farther downstream of the ignition region. The same unsaturated hydrocarbon species have been identified as major contributors to soot production in both diesel engines and laboratory flames [21][22][23][24][25][26][27][28][29][30][31][32] .…”

Ignition of isomers of pentane: An experimental and kinetic modeling study

“…Low-temperature reactions produce an increasing amount of H 2 O 2 that is stable until its decomposition temperature is reached; since this reaction is part of the H 2 /O 2 reaction submechanism, it is independent of the specific hydrocarbon fuel being studied. Past kinetic modeling studies have demonstrated that this same decomposition reaction is responsible for the onset of knock in spark-ignition engines [21,25,26], ignition in diesel engines [26,27], and ignition under homogeneous charge compression ignition (HCCI) conditions [26,28].…”

Experimental and kinetic modeling study of the shock tube ignition of a large oxygenated fuel: Tri-propylene glycol mono-methyl ether

“…[38]. Figure 16(a) presents the predicted mole fractions for some soot precursor species (C 2 H 2 , C 2 H 4 , and C 3 H 6 ) at φ = 3.0 in "air", p 5 = 50 atm, and T 5 = 770 K for both TPGME and nheptane.…”