Ignition delay times of C2H4, C2H4/n-C4H10, and n-C4H10/i-C4H10 under O2/CO2 atmospheres: Shock tube experiments and kinetic model

Abstract

Oxy-fuel combustion of fossil fuels based on the Allam cycle has garnered increasing attention owing to its high-power cycle efficiency in carbon capture. The submechanism of ethylene, an important intermediate product in the oxidation of long-chain alkanes, is vital for establishing chemical kinetic models of alkanes for oxy-fuel combustion. In this study, the ignition delay times of C2H4 diluted in CO2 are measured at pressures of 1 and 10 atm under O2/CO2 atmospheres at three equivalence ratios (0.5, 1.0, and 2.0) in a shock tube. Meanwhile, the ignition delay times of C2H4/n-C4H10 mixtures and n-C4H10/i-C4H10 mixtures diluted in CO2 are measured at pressures of 1 and 10 atm, equivalence ratios of 1.0, and three mixing ratios (1:2, 1:1, and 2:1). The C2H4 submechanism in the Oxymech2.0 Plus model proposed in our previous study is modified by updating some C2H4-related reactions. The modified Oxymech model, NUIGMECH1.1, and Wang2021 are evaluated based on the present experimental ignition delay times and other experimental results from the literature, including the ignition delay times of C2H4 diluted in both CO2 and conventional atmospheres, as well as the laminar flame speeds of C2H4 and C2H4 profiles in pyrolysis. The results show that the modified Oxymech model accurately predicts the experimental results. The modified Oxymech model is compared with NUIGMECH1.1 to predict the ignition delay times in CO2 atmospheres and laminar flame speeds more accurately. The effects of CO2 on the ignition delay of C2H4 are discussed comprehensively.