THE EFFECT OF NITRIC-OXIDE ON PREMIXED FLAMES OF CH4, C2H6, C2H4, ANDC2H2

Nitric oxide was doped into premixed, stoichiometric, 10 torr flames o f CH4/O-2/N-2, C2H6/O-2/N-2, C2H4/O-2/N-2 and C2H2/O-2/N-2. Spatial pr ofiles of electronic ground state CH, OH, NO, CN, NCO, NH and metastab le state C-3(2) were obtained by laser-induced fluorescence. The peak temperatures of the flames were maintained at 1800 K by varying the N- 2 buffer gas mole fraction. Comparisons of the profiles among the diff erent fuels illustrate differences in the hydrocarbon flame structure that lead to different NO reactivities in these flame systems. Concent rations of the nitrogen-containing intermediates are similar in the me thane, ethane, and ethylene flames, but are considerably larger in the acetylene flame, indicating a much greater NO reactivity in this flam e, The species profiles are modeled using three different kinetic mech anisms; all of these have significant shortcomings. (C) 1997 by The Co mbustion Institute.