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A model of reduced oxidation kinetics using constituents and species: Iso-octane and its mixtures with n-pentane, iso-hexane and n-heptane

Harstad, Kenneth and Bellan, Josette (2010) A model of reduced oxidation kinetics using constituents and species: Iso-octane and its mixtures with n-pentane, iso-hexane and n-heptane. Combustion and Flame, 157 (11). pp. 2184-2197. ISSN 0010-2180. http://resolver.caltech.edu/CaltechAUTHORS:20171019-095549725

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Abstract

A previously described methodology for deriving a reduced kinetic mechanism for alkane oxidation and tested for n-heptane is here shown to be valid, in a slightly modified version, for iso-octane and its mixtures with n-pentane, iso-hexane and n-heptane. The model is still based on partitioning the species into lights, defined as those having a carbon number smaller than 3, and heavies, which are the complement in the species ensemble, and mathematically decomposing the heavy species into constituents which are radicals. For the same similarity variable found from examining the n-heptane LLNL mechanism in conjunction with CHEMKIN II, the appropriately scaled total constituent molar density still exhibits a self-similar behavior over a very wide range of equivalence ratios, initial pressures and initial temperatures in the cold ignition regime. When extended to larger initial temperatures than for cold ignition, the self-similar behavior becomes initial temperature dependent, which indicates that rather than using functional fits for the enthalpy generation due to the heavy species’ oxidation, an ideal model based on tabular information extracted from the complete LLNL kinetics should be used instead. Similarly to n-heptane, the oxygen and water molar densities are shown to display a quasi-linear behavior with respect to the similarity variable, but here their slope variation is no longer fitted and instead, their rate equations are used with the ideal model to calculate them. As in the original model, the light species ensemble is partitioned into quasi-steady and unsteady species; the quasi-steady light species mole fractions are computed using the ideal model and the unsteady species are calculated as progress variables using rates extracted from the ideal model. Results are presented comparing the performance of the model with that of the LLNL mechanism using CHEMKIN II. The model reproduces excellently the temperature and species evolution versus time or versus the similarity variable, with the exception of very rich mixtures, where the predictions are still very good but the multivalued aspect of these functions at the end of oxidation is not captured in the reduction. The ignition time is predicted within percentages of the LLNL values over a wide range of equivalence ratios, initial pressures and initial temperatures.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.combustflame.2010.06.010DOIArticle
http://www.sciencedirect.com/science/article/pii/S0010218010001768?via%3DihubPublisherArticle
Additional Information:© 2010 The Combustion Institute. Published by Elsevier Inc. Received 26 March 2010, Revised 12 May 2010, Accepted 18 June 2010, Available online 9 July 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. Computation with the full kinetic mechanisms were performed using the JPL Supercomputing facility.
Funders:
Funding AgencyGrant Number
JPL/CaltechUNSPECIFIED
Army Research Office (ARO)UNSPECIFIED
Subject Keywords:Reduced oxidation kinetics for iso-octane; Iso-octane mixtures
Record Number:CaltechAUTHORS:20171019-095549725
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20171019-095549725
Official Citation:Kenneth Harstad, Josette Bellan, A model of reduced oxidation kinetics using constituents and species: Iso-octane and its mixtures with n-pentane, iso-hexane and n-heptane, In Combustion and Flame, Volume 157, Issue 11, 2010, Pages 2184-2197, ISSN 0010-2180, https://doi.org/10.1016/j.combustflame.2010.06.010. (http://www.sciencedirect.com/science/article/pii/S0010218010001768)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:82481
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:19 Oct 2017 18:17
Last Modified:19 Oct 2017 18:17

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