Experimental and kinetic study of pentene isomers and n-pentane in laminar flames

Abstract

Laminar flame speeds of three pentene isomers (1-pentene, 2-pentene and 2-methyl-2-butene) and n-pentane are investigated at equivalence ratios of 0.7–1.6, initial pressures of 1–4 atm, and initial temperatures of 353–433K using a constant volume combustion bomb. Results show that the laminar flame speeds increase in the order of 2-methyl-2-butene, n-pentane, 2-pentene, and 1-pentene. A recently published model on pentane isomers (NUI-PI) has been optimized by refining the submodels of the 1-pentene and 2-methyl-2-butene. This optimized model yields reasonable agreement with the experimental data except over-predictions for 2-pentene. The analysis indicates the discrepancy of laminar flame speeds between 1-pentene and n-pentane is mainly caused by the thermal effect, different from the discrepancy between 1-pentene and 2-methyl-2-butene which mainly results from the chemical kinetic effect. The kinetic effect is further investigated employing the sensitivity and reaction path analyses. The analyses reveal that 1-pentene generates the H-radical precursor ethyl radical, while 2-methyl-2-butene produces large amount of the H-consuming branching intermediates (IC4H8, AC5H9C, CC5H9-B and B13DE2MJ) and presents the weaker H regenerating ability. In addition, compared with 1-pentene, 2-methyl-2-butene yields larger amount of methyl radical which would block the whole reaction process.