Numerical and experimental investigation of liquid fuel combustion in a counterflow configuration

A major portion of world's energy demand is currently met by combustion of liquid fuels. The products of combustion of most commercially available fuels contain pollutants such as particulate matter, and oxides of nitrogen. Consequently, energy conservation and environmental concerns provide a strong motivation for fundamental studies on the flame structure and the mechanism of soot and NOX formation in flames.; In order to avoid the complexities associated with the droplet/vapor transport and nonuniform evaporation processes, a fundamental investigation of prevaporized liquid fuel combustion in idealized configurations is very useful. However, there is a paucity of such measurements in the literature.; An experimental and numerical investigation of counterflow prevaporized n-heptane nonpremixed and partially premixed flames is reported. The major objective is to provide well resolved experimental data regarding the detailed structure and emission characteristics of these flames for a wide range of nitrogen dilution, partial premixing and strain rate.; The measurements include profiles of temperature, concentration of main species, hydrocarbon intermediates, and soot precursors. The measurements are compared with predictions using a detailed n-heptane oxidation mechanism that includes the chemistry of NOX and PAHs formation. The reaction mechanism is improved using pathway analysis and measured benzene profiles. The validated mechanism is then used to investigate the effects of nitrogen dilution, partial premixing and strain rate on the flame structure and the production of NOX and soot precursors.; Measurements are compared with predictions for both nonpremixed and partially premixed flames on a wide range of nitrogen dilution, degree of premixing and strain rate. Measurements and predictions show excellent agreement with respect to temperature and major species profiles and reasonably good agreement with respect of intermediate hydrocarbons and benzene species.; Numerical results for N2 diluted nonpremixed flames indicate that NOX formation is more strongly influenced by nitrogen dilution, while soot precursor formation is influenced by both nitrogen dilution and strain rate. Both the numerical and experimental results for partially premixed flames show the double flame structure, containing a rich premixed zone on the fuel side and a nonpremixed zone on the oxidizer side, and its evolution with partial premixing and strain rate.