UC San Diego

Well-controlled laboratory experiments in simplified reactors, such as counterflow burners, most easily and accurately test the ability of chemical-kinetic mechanisms and transport descriptions to predict combustion processes. Diffusion flame investigations at atmospheric and elevated pressures have been carried out to provide insights into the structure and combustion chemistry of hydrogen, low molecular weight hydrocarbons and oxygenated fuels. A newly designed high-pressure combustion facility was used to study the structures and extinction conditions of counterflow diffusion flames in air for nitrogen- diluted hydrogen, methane, ethane, and ethylene, from 0.1MPa to 2.0 MPa. In all cases, the strain rate at extinction was found to increase with pressure in the moderate pressure range until a peak value is attained, above which a decreasing trend begins. In addition, a methane air diffusion flame was doped with hydrogen at atmospheric pressure. Irrespective of whether the hydrogen was added on the fuel or oxidizer side, the ratio of the extinction strain rate with hydrogen addition to that without was the same when the stoichiometric mixture fraction, the adiabatic flame temperature, and the proportion of oxygen that consumes the added fuel are fixed. Furthermore, an experimental investigation of the structure of large alcohols and critical conditions of methyl-esters provide new insights for the development and validation of chemical-kinetic mechanisms