Ignition characteristics of ethanol–hydrogen mixtures with different hydrogen contents at elevated initial temperatures

Abstract

Through a shock tube facility, ignition processes of ethanol–hydrogen mixtures with different hydrogen contents at elevated initial temperatures were explored experimentally and numerically. Relationships between ignition delay time and initial temperature as well as hydrogen content were analyzed. Ignition characteristics of the mixtures were paid attention to from the point of chemical kinetics. The result shows that at hydrogen contents of 0%, 70% and 90%, linear relationships are observed between logarithmic ignition delay times of the mixtures and reciprocals of initial temperatures. At higher initial temperatures, the ignition delay time of the mixtures does not vary monotonously with the hydrogen content. At initial temperature of 1200 K, for the mixtures with hydrogen contents of 10% and 70%, the ignition depends on H and OH, but at hydrogen content of 90%, the ignition is affected exclusively by H. At 1700 K, as the hydrogen content rises from 10% to 70%, effect of reactions involving H on the ignition enhances, but when elevating continually the hydrogen content to 90%, this kind of effect weakens. During ignition processes of the mixtures at 1200 K, ethanol is consumed mainly through reacting with radicals, and the conversion of hydrogen occurs mainly near the ignition time points. While at 1700 K, the time period during which the decomposition reaction dominates the ethanol consumption extends gradually with the increasing hydrogen content, and the consumption of hydrogen also occurs over a wider time period relative to the entire ignition period.