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Modelling studies of the oxidation and autoignition of alkanes, aromatics, and their mixtures at high pressure between 600 and 1500 K. Reduction of detailed mechanisms. Measurement of soot formation.

Author: Dr. Ahmad Saylam

Document type: Doctoral thesis

Original thesis date:

Archival status: The thesis was completed in 2005 and later deposited as an open digital archival record. The DOI identifies the archival deposit; it does not change the original thesis date.

Scientific scope: Experimental and modelling investigation of hydrocarbon oxidation and autoignition at elevated pressure, detailed chemical-kinetic mechanism development and reduction, comparison with experimental data, and soot and aromatic-species diagnostics.

Archival DOI: 10.5281/zenodo.19438123

Zenodo record: https://zenodo.org/records/19438123

Abstract

Understanding and controlling combustion phenomena requires close interaction between experiments and modelling. The two approaches are presented together because the complexity of hydrocarbon oxidation often prevents complete elucidation of all chemical pathways.

The work examines the difficulty of improving detailed oxidation mechanisms, including an investigation of isooctane chemistry. Detailed hydrocarbon mechanisms can contain hundreds of species and thousands of reactions, creating a need for smaller mechanisms that retain the behaviour relevant to autoignition and oxidation.

A mechanism-reduction approach was therefore developed and applied. Detailed thermokinetic mechanisms were constructed and reduced, then evaluated against new experimental measurements together with earlier experimental data and literature datasets. Agreement was assessed for the observables and thermochemical conditions represented by those comparisons and should not be generalized beyond them without re-evaluation.

The thesis also includes optical and laser-diagnostic investigations of soot particles and polycyclic aromatic hydrocarbons in a methane flame. These measurements provide an additional experimental line of inquiry into particle-formation precursors and soot development; they should not be interpreted as direct validation of every oxidation or autoignition mechanism discussed elsewhere in the thesis.

Principal research contributions

  • analysis of oxidation and autoignition chemistry for alkanes, aromatics and selected mixtures over the investigated high-pressure and temperature conditions;
  • development and evaluation of detailed thermokinetic mechanisms;
  • reduction of large kinetic mechanisms using reaction-rate and sensitivity information;
  • comparison and validation of selected mechanism predictions against rapid-compression-machine measurements and published experimental data within defined conditions;
  • investigation of soot particles and aromatic intermediates using optical and laser-diagnostic methods.

Scope and application boundary

The thesis establishes a substantial research basis for mechanism-development, reduction and validation workflows. Individual detailed and reduced mechanisms remain dependent on their fuels, mixture compositions, temperature and pressure range, reactor assumptions, experimental database and target observables. Agreement for ignition delay or selected species does not establish equal fidelity for flame propagation, pollutant formation, soot chemistry or other objectives.

Use in modern CFD, engine simulations, alternative fuels, broader mixture compositions or new pressure and temperature ranges requires renewed applicability assessment and validation and, where appropriate, updating of thermodynamic, transport and kinetic data. Modern use should also account for subsequent mechanism revisions, improved rate coefficients and newer experimental datasets.

Evidence interpretation

The thesis combines several evidence types: independent experiments, detailed kinetic modelling, reduced-mechanism development, comparison with measurements, and optical diagnostics. These contributions are complementary but not interchangeable.

Computational agreement between a reduced and detailed mechanism is evidence about reduction fidelity relative to the parent model. Agreement between a model and experiments is a separate validation step. Optical soot or aromatic-species measurements provide experimental evidence for those measured quantities, not universal validation of all chemical pathways in the kinetic mechanism.

Full text

Availability of the thesis for reading does not by itself grant reuse rights beyond those stated in the thesis, archival deposit or applicable rights information.

Recommended citation

Saylam, A. (2005). Modelling studies of the oxidation and autoignition of alkanes, aromatics, and their mixtures at high pressure between 600 and 1500 K. Reduction of detailed mechanisms. Measurement of soot formation. Doctoral thesis. Archival DOI: https://doi.org/10.5281/zenodo.19438123

Relation to later kinetic-intelligence work

The thesis provides historical experimental and modelling foundations for later work on mechanism reduction and combustion-reaction analysis. Later degree-centrality, reaction-network, DRG, adaptive-chemistry and state-transfer methods are separate developments and should not be treated as components of the 2005 thesis unless an explicit later study establishes that connection.