A COMPUTER MODELLING STUDY OF METHANE OXIDATION

 
 
 
 

A COMPUTER MODELLING STUDY OF METHANE OXIDATION

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Title: A COMPUTER MODELLING STUDY OF METHANE OXIDATION
Author: Mesarch, Scott Eugene
Description: Methane oxidation has been studied by numerous investigators because of its simplicity in structure and great importance as a practical fuel. Overall, the broad outlines of methane oxidation seem to be agreed upon and only the details remain to be sorted out. A comprehensive and robust chemical reaction mechanism is one of the key components in a computer modeling study for designing and/or optimizing practical combustion systems. In this study, a comprehensive but truncated methane oxidation mechanism (31 species, 172 reactions) - GRC_Methane_Mech - has been optimized using the shock tube ignition data of stoichiometric air-like, stoichiometric non air-like and lean mixtures at various conditions. Important reactions in methane oxidation were identified by means of a series of flux and sensitivity analyses using the existing GRI_Mech 2.11 and their rate coefficients are updated or revised through critical literature review. Two less well known reactions were found to be crucial in simulating experimental ignition delay data. The optimized rate coefficient expressions of these two reactions are (unit of cm³ /(mol¹ s¹): k114 (HO2 + CH3 → CH4 + O2) = 5.5 x 10¹² exp(-4900 K/T) and k115 (HO2 + CH3 → CH3O + OH) = 16.0 x 10¹³ exp(-5500 K/T). The absolute values of the experimental ignition delay data of various mixtures and their dependence on the concentrations of methane (fuel) and oxygen (oxidizer) are correctly re-produced by our GRC_Methane_Mech. In this optimization, methane oxidization is explained via reactions with H, O, and OH chain carriers, not with HO2 as a major chain carrier. Although reaction progresses for stoichiometric air-like, non air-like, and lean mixtures have been successfully simulated with GRC_Methane_Mech, it would be very beneficial if our optimized rate coefficients for R114 (HO2 + CH3 → CH4 + O2) and R115 (HO2 + CH3 → CH3O + OH) are validated by carefully designed experiments or high level quantum calculations.
Permanent Link: http://rave.ohiolink.edu/etdc/view?acc_num=akron1134091533
http://hdl.handle.net/2374.OX/3586
Date: 2005

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