Twenty-Seventh Symposium (International) on Combustion/The Combustion Institute, 1998/pp. 389±396 AN EXPERIMENTAL AND KINETIC CALCULATION OF THE PROMOTION EFFECT OF HYDROCARBONS ON THE NO±NO2 CONVERSION IN A FLOW REACTOR

Experimental and detailed chemical kinetic modeling work has been performed to investigate the role of hydrocarbon oxidation in NO±NO2 conversion. An atmospheric pressure, quartz ¯ow reactor was used to examine the dependence of NO oxidation to NO2 by hydrocarbon type, reaction temperature, and residence time. The ®ve hydrocarbons examined were methane, ethylene, ethane, propene, and propane. In the experiment, probe measurement of the species concentrations was performed in the ¯ow reactor using a mixture of NO(20 ppm)/air/hydrocarbon(50 ppm) at residence times from 0.16 to 1.46 s and temperatures from 600 to 1100 K. In the chemical kinetic calculation, the time evolution of NO, NO2, hydrocarbons, and reaction intermediates were evaluated for a series of the hydrocarbons and the tem-peratures. The chemical mechanism consisted of 639 reversible reactions and 126 species. Experimental results indicate that, in general, ethylene and propane effectively oxidize NO to NO2 while methane is less effective. The calculation indicates the important chemical kinetic features that control NO±NO2 conversion for each hydrocarbon type. The dependence of NO±NO2 conversion with hydrocar-bon type and temperature is qualitatively reproduced by the calculation. The calculation indicates that all ®ve hydrocarbons oxidize NO to NO2 predominantly through NO ` HO2 i NO2 ` OH and that the contribution of oxidation by RO2 and HORO2 is minor. Highest effectiveness comes from hydrocarbon