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A model of reduced kinetics for alkane oxidation using constituents and species: Proof of concept for n-heptane

Harstad, Kenneth and Bellan, Josette (2010) A model of reduced kinetics for alkane oxidation using constituents and species: Proof of concept for n-heptane. Combustion and Flame, 157 (8). pp. 1594-1609. ISSN 0010-2180.

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A methodology for deriving a reduced kinetic mechanism for alkane oxidation is described and applied to n-heptane. The model is based on partitioning the species of the skeletal kinetic mechanism into lights, defined as those having a carbon number smaller than 3, and heavies, which are the complement in the species ensemble. For modeling purposes, the heavy species are mathematically decomposed into constituents, which are similar but not identical to groups in the group additivity theory. From analysis of the LLNL skeletal mechanism in conjunction with CHEMKIN II, it is shown that a similarity variable can be formed such that the appropriately scaled global constituent molar density exhibits a self-similar behavior over a very wide range of equivalence ratios, initial pressures and initial temperatures that is of interest for predicting n-heptane oxidation. Furthermore, the oxygen and water molar densities are shown to display a quasi-linear behavior with respect to the similarity variable. The light species ensemble is partitioned into quasi-steady and unsteady species. The concept is tested by using tabular information from the LLNL skeletal mechanism in conjunction with CHEMKIN II. The test reveals that the similarity concept is indeed justified and that the combustion temperature is well predicted, but that the ignition time is overpredicted. To palliate this deficiency, functional modeling is incorporated into our conceptual reduction. Due to the reduction process, models are also included for the global constituent molar density, the kinetics-induced enthalpy evolution of the heavy species, the contribution to the reaction rate of the unsteady lights from the heavies, the molar density evolution of oxygen and water, the mole fractions of the quasi-steady light species and the mean molar heat capacity of the heavy species. The model is compact in that there are only nine species-related progress variables. Results are presented comparing the performance of the model for predicting the temperature and species evolution with that of the skeletal mechanism. The model reproduces the ignition time over a wide range of equivalence ratios, initial pressure and initial temperature.

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Bellan, Josette0000-0001-9218-7017
Additional Information:© 2010 The Combustion Institute. Published by Elsevier Inc. Received 15 October 2009, Revised 19 January 2010, Accepted 18 February 2010, Available online 11 March 2010. This study was conducted at the California Institute of Technology, Jet Propulsion Laboratory (JPL), and was sponsored by the Army Research Office, with Dr. Ralph Anthenien as Program Manager. Ms. Elly Ponce of JPL is thanked for the drawing of Fig. 1.
Funding AgencyGrant Number
Army Research Office (ARO)UNSPECIFIED
Subject Keywords:Reduced oxidation kinetics for n-heptane
Issue or Number:8
Record Number:CaltechAUTHORS:20171019-095909602
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Official Citation:Kenneth Harstad, Josette Bellan, A model of reduced kinetics for alkane oxidation using constituents and species: Proof of concept for n-heptane, In Combustion and Flame, Volume 157, Issue 8, 2010, Pages 1594-1609, ISSN 0010-2180, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:82482
Deposited By: Tony Diaz
Deposited On:19 Oct 2017 18:14
Last Modified:09 Mar 2020 13:18

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