Experimental and modeling of autoignition of gaseous hydrocarbon fuels in the presence of H2 and C2H4

Abstract

The focus of the present work is to understand the effect of H2 and C2H4 on the ignition characteristics of other gaseous fuels, namely, CH4, C2H6 and C3H6. Atmospheric-pressure flow reactor experiments were performed to measure the ignition delay times of CH4, C2H6 and C3H6 binary mixtures with H2 or C2H4 between 800 and 950 K. Most of the experiments were conducted at stochiometric conditions with 21% O2. Select tests were performed to examine the effects of equivalence ratios and oxygen concentrations. Ignition delay time were also measured for ternary mixtures of C3H6-C2H4-H2 at select conditions. Based on the experimental data, the overall effectiveness of H2 or C2H4 in reducing the ignition delay time of the binary mixtures can be listed in the following order: CH4 > C3H6 > C2H6. The experimental data were used to refine and validate the chemical kinetic mechanism for allyl-HO2 system relevant to low-temperature ignition chemistry of C3H6. A detailed sensitivity analysis is presented to identify the important reaction pathways, and their implications for the experimental observations are discussed. Monte Carlo simulations were used to quantify the model uncertainty for ignition delay time predictions, and to identify reactions that have significant contribution to the model uncertainty. Among the binary mixtures studied, CH4-H2 mixture produced the largest model uncertainty, primarily due to the sensitive reactions involving HO2 radical.