Shock tube measurements and kinetic modeling study on autoignition characteristics of cyclohexanone

Cyclohexanone was identified as an attractive second-generation biofuel that can be used as an alternative fuel or blending component, thereby reducing greenhouse gas and particulate emissions from internal combustion engines. This paper investigates auto-ignition characteristics of cyclohexanone/O-2/Ar mixtures behind reflected shock waves. Ignition delay time measurements cover the temperature range of 1255-1646K, with pressures near 2.5, 5, and 10 atm, argon/oxygen dilution ratios of 23.9, 48.9 and 98.9, and equivalence ratios of 0.5, 1.0, and 2.0. Five kinds of mixtures were prepared to determine the effects of pressure, equivalence ratio and dilution ratio on the reactivity over the entire temperature range. An ignition delay correlation, tau = 6.87 x 10(-6)p(-0.52)Phi D-0.70(0.66) exp(45.59/RT) (mu s), has been developed for cyclohexanone, including dependencies on pressure, equivalence ratio and dilution ratio. Experimental data have been compared to the kinetic modeling predictions of Serinyel et al. [Proc. Combust. Inst. 35 (2015) 507-514]. In general, the predictions overestimate the experimental data by 30-50%. With several reaction rate constants of selected small radical reactions updated, the predictions by modified mechanism present satisfactory agreement with the measured ignition delay data. Also, simulations based on the original model and modified model were compared to species concentrations measured in a jet-stirred reactor at 10 atm from the literature. Reaction pathway and sensitivity analyses were performed to identify the fuel consumption paths and key reactions during the ignition process of cyclohexanone. To our knowledge, the auto-ignition measurement of gas-phase cyclohexanone presented here are the first measurement for this compound. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.