EXPERIMENTAL AND MODELING STUDY OF PREMIXED LAMINAR FLAMES OF ETHANOL AND METHANE

An Experimental and Kinetic Modelling Study on Laminar Premixed Flame Characteristics of Ethanol/Acetone Mixtures

Since both ethanol and acetone are the main components in many alternative fuels, research on the burning characteristics of ethanol-acetone blends is important to understand the combustion phenomena of these alternative fuels. In the present study, the burning characteristics of ethanol-acetone fuel blends are investigated at a temperature of 358 K and pressure of 0.1 MPa with equivalence ratios ranging from 0.7 to 1.4. Ethanol at 100% vol., 25% vol. ethanol/75% vol. acetone, 50% vol. ethanol/50% vol. acetone, 75% vol. ethanol/25% vol. acetone, and 100% vol. acetone are studied by the constant volume combustion chamber (CVCC) method. The results show that the laminar burning velocities of the fuel blends are between that of 100% vol. acetone and 100% vol. ethanol. As the ethanol content increases, the laminar burning velocities of the mixed fuels increase. Furthermore, a detailed chemical kinetic mechanism (AramcoMech 3.0) is used for simulating the burning characteristics of the mixtures. The directed relation graph (DRG), DRG with error propagation (DRGEP), sensitivity analysis (SA), and full species sensitivity analysis (FSSA) are used for mechanism reduction. The flame structure of the skeletal mechanism does not change significantly, and the concentration of each species remains basically the same value after the reaction. The numbers of reactions and species are reduced by 90% compared to the detailed mechanism. Sensitivity and reaction pathway analyses of the burning characteristics of the mixtures indicate that the reaction C2H2+H(+M)<=>C2H3(+M) is the key reaction.

ReaxFF Study of Ethanol Oxidation in O2/N2 and O2/CO2 Environments at High Temperatures

The goal of this study was to investigate the reaction mechanisms linked with the oxy-fuel combustion of ethanol (C₂H₆O). The oxidation of ethanol in O₂/N₂ and O₂/CO₂ environments was examined using reactive molecular dynamics in the temperature range from 2200 to 3000 K at constant density media and O₂/fuel ratio equals to 0.5. The main reactions were examined to supply a description of the ethanol oxidation behavior, the main product distribution, and the corresponding time evolution behavior in the atomic scale. It has been noted that the oxidation of C₂H₆O was initiated mainly from the same routes in both environments generating the same main species. However, the key reaction pathways were different depending on the media. We noticed an increase of CO formation when N₂ was replaced by CO₂ molecules, increasing the net flux of the following reactions: by CO₂ + H → CO + OH and CO₂ + CHO → O═COH + CO. This work also studied the effect of increasing O₂ concentration (O₂/fuel ratio equals to 0.5, 1.0, and 2.0) in O₂/CO₂ combustion. During the simulations, high oxygenated and unstable species were detected such as carbonates and carboxyl radicals. The change of the O₂/fuel ratio from 0.5 to 2.0 lead to an increase of CO₂ formation mainly from O₂ + O═COH → CO₂ + HO₂ and O₂ + CO → CO₂ + O reactions. In addition, the increase of O₂ concentration attenuated the effect of CO₂ and could increase the occurrence of reactions that lead to flame cessation.

Combustion chemistry and flame structure of furan group biofuels using molecular-beam mass spectrometry and gas chromatography - Part III: 2,5-Dimethylfuran

This work is the third part of a study focusing on the combustion chemistry and flame structure of furan and selected alkylated derivatives, i.e. furan in Part I, 2-methylfuran (MF) in Part II, and 2,5-dimethylfuran (DMF) in the present work. Two premixed low-pressure (20 and 40 mbar) flat argon-diluted (50%) flames of DMF were studied with electron-ionization molecular-beam mass spectrometry (EI-MBMS) and gas chromatography (GC) under two equivalence ratios (φ=1.0 and 1.7). Mole fractions of reactants, products, and stable and radical intermediates were measured as a function of the distance to the burner. Kinetic modeling was performed using a reaction mechanism that was further developed in the present series, including Part I and Part II. A reasonable agreement between the present experimental results and the simulation is observed. The main reaction pathways of DMF consumption were derived from a reaction flow analysis. Also, a comparison of the key features for the three flames is presented, as well as a comparison between these flames of furanic compounds and those of other fuels. An a priori surprising ability of DMF to form soot precursors (e.g. 1,3-cyclopentadiene or benzene) compared to less substituted furans and to other fuels has been experimentally observed and is well explained in the model.