Fuel-rich flame chemistry in low-pressure cyclopentene flames

Laminar premixed flat cyclopentene/oxygen/argon Barnes with different stoichiometries (C/O = 0.6. 0.77, and 0.94) were studied at 50 mbar under fuel-rich non-sooting conditions. This study was motivated by the scarcity of information on C-5 fuel combustion which is ill contrast with the potential importance of C-5 species reactions in benzene formation. Concentrations as a function of height above the burner were measured for more than 30 stable and radical species using molecular beam mass spectrometry Temperature was measured in the unperturbed flame with laser-induced fluorescence of seeded NO. Stable species concentrations in the burned gases were found in good agreement with equilibrium calculations. For information on the flame structure in the reaction zone, species profiles for intermediates of relevance in the formation of aromatics were inspected regarding in particular several CxHy compounds with 2 less than or equal to x less than or equal to 10. The measured data was analyzed with respect to the formation of C-6 species, in particular of benzene as a key species in the soot formation mechanism. A reaction flow analysis has been performed which reveals striking differences to other fuels, including acetylene and propene. It does not seem feasible to rely on a single dominant pathway to benzene in cyclopentene flames. Reactions of C5H5 and C5H6 were found of importance, that of C5H6 + CH3 being of similar influence on C6H6 formation as the propargyl recombination, a result of interest for detailed flame modeling.