Laminar Flame Speeds of Cyclohexane and Mono-alkylated Cyclohexanes at Elevated Pressures

摘要

Laminar flame speeds of cyclohexane, methyl-cyclohexane and ethyl-cyclohexane at atmospheric and elevated pressures up to 20 atm were determined in a heated, dual-chamber vessel using nonlinear extrapolation. Calculated values using JetSurf 2.0 mechanism yielded satisfactory agreement with the present measurements at all pressures, with slight over-prediction at 1 atm. Results show that the flame speeds of methyl-cyclohexane and ethyl-cyclohexane are similar, while those of cyclohexane are higher by 5% at 1 atm and 13% at 10 atm. Examination of computed flame structure shows that owing to its special, symmetric ring structure, cyclohexane produces substantially more chain-branching C_2 and C_4 intermediates than the relatively less reactive C_3 intermediates. On the contrary, a more balanced distribution of C_2-C_4 intermediates is present in flames of methyl- and ethyl-cyclohexane due to the substitution of alkyl group for H.