Experimental and Modeling Evaluation of Dimethoxymethane as an Additive for High-Pressure Acetylene Oxidation

Area of Science:

• Combustion Chemistry
• Chemical Kinetics
• High-Pressure Reactivity

Background:

• Acetylene (C2H2) oxidation is crucial for understanding combustion processes.
• Dimethoxymethane (DMM) is an oxygenate fuel additive with potential applications.
• High-pressure oxidation introduces complex reaction pathways.

Purpose of the Study:

• To experimentally and computationally analyze the high-pressure oxidation of acetylene-dimethoxymethane (C2H2-DMM) mixtures.
• To investigate the influence of pressure, oxygen availability (air excess ratio, λ), and DMM concentration on C2H2 oxidation.
• To update and validate a chemical kinetic mechanism for DMM oxidation.

Main Methods:

• Tubular flow reactor experiments were conducted at pressures of 20, 40, and 60 bar.
• Varying air excess ratios (λ) and DMM concentrations (70 and 280 ppm) were employed.
• A detailed chemical kinetic mechanism, updated with recent theoretical calculations for DMM, was used for modeling.

Main Results:

• Under fuel-lean conditions, DMM enhances C2H2 reactivity via chain branching pathways, especially at higher concentrations.
• H-abstraction by OH radicals is the primary DMM consumption route, forming dimethoxymethyl and methoxymethoxymethyl radicals.
• A competition between β-scission and O2-addition reactions governs radical consumption, with O2-addition increasing at higher oxygen concentrations.

Conclusions:

• DMM addition significantly impacts high-pressure C2H2 oxidation by promoting radical formation.
• The presence of ethers like DMM and dimethyl ether (DME) shifts C2H2 conversion to lower temperatures compared to ethanol.
• The validated kinetic model provides insights into the complex reaction network of C2H2-DMM oxidation.