The chemical structures of opposed flow diffusion flames of C3 oxygenated hydrocarbons (isopropanol, dimethoxy methane, and dimethyl carbonate) and their mixtures

Species concentrations and temperatures were measured across opposed flow diffusion flames of three C3 oxygenated hydrocarbons: isopropyl alcohol, dimethoxy methane (DMM), and dimethyl carbonate (DMC). In addition, measurements were made with propane for comparison. Measurements were repeated for mixtures of propane and oxygenated hydrocarbons to investigate synergistic effects. The experiments were conducted at atmospheric pressure by withdrawing samples from the flame using a quartz microprobe coupled to an online gas chromatograph (GC). Gas analysis was also performed using HPLC techniques. Profiles were made of temperature and of more than 16 species, including oxygenated and aromatic hydrocarbons. The isopropyl alcohol results suggest that the presence of the OH group favors the formation of propylene, as well as acetaldehyde and acetone, relative to the propane case. For DMM and DMC, the lack of C-C bonds greatly reduces the formation of ethylene, acetylene, and propylene. For example, relative to the propane flame, the ethylene levels of isopropanol, DMM, and DMC flames were reduced by 41, 77, and 93%, respectively. In the case of DMM, significant quantities of formaldehyde and methyl formate, were measured. All intermediate hydrocarbon levels were lower for DMC relative to DMM. The principal intermediate of DMC was formaldehyde. Mixtures of propane and oxygenates generally had lower hydrocarbon levels than would be expected based on only additive effects. The information provided should be of considerable utility in providing better insight into oxygenated hydrocarbon combustion, as well as in developing and validating chemical kinetic mechanisms. (C) 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved.