Experimental and kinetic study on the pyrolysis and oxidation of isopentane in a jet-stirred reactor

Abstract

An experimental and kinetic study on the pyrolysis and oxidation of isopentane (2-methylbutane) were conducted in this work. The experiments were performed in a jet-stirred reactor (JSR) at the equivalence ratios of 0.5, 1.0, 2.0 and ∞, across the temperature range from 700 to 1100 K, and at atmospheric pressure. Mole fractions of oxygen, hydrogen, CO, CO2, C1C6 hydrocarbons and methanol were measured using a gas chromatograph (GC), at the initial fuel mole fraction of 0.5% and residence time at 2 s. Three literature kinetic models, named as the Bugler model, the NUIGMech1.1 model, and the LLNL model, were employed to predict the speciation profiles measured in this work, and the ignition delay times in the literature. Based on the model performances and kinetic analysis, some modifications were made to the LLNL model, by supplementing the beta-scission reaction aC5H11 = C4H8–1 +CH3, and updating the rate constants for the reactions iC5H12 + OH = cC5H11 + H2O, iC5H12 + OH = bC5H11 + H2O, C3H4-a = C3H4-p, C3H4-a + H = C3H4-p + H, and C2H6 + CH3 = C2H5 +CH4. After the modifications, the model predictions on mole fractions of 1-butene, ethane, allene and propyne in JSR pyrolysis and oxidation were improved, and the overestimations on the ignition delay times at low temperatures are significantly reduced. Reaction pathway and sensitivity analyses were carried out using the modified model. The results indicated that fuel consumption in pyrolysis is sensitive to the unimolecular decomposition reaction iC5H12 = iC3H7 + C2H5 across the temperature range of 900–1100 K. In addition, fuel low-temperature oxidation reactivity is sensitive to the mutual conversion between HO2 and H2O2, while the competition between OH and HO2 formation has a more pronounced effect at increased temperatures.