Experimental and modeling efforts towards a better understanding of the high-temperature combustion kinetics of C3C5 ethyl esters

Kinetic investigations into small ethyl esters lay the foundation for a good understanding of combustion properties, particularly those brought about by the ethyl ester functional group, for biodiesels in forms of fatty acid ethyl esters. A systematical study was conducted in this work, aimed at better interpreting the high-temperature reaction schemes for the simple C3C5 ethyl esters. Quantitative information for crucial intermediates closely related to fuel consumptions was probed in the low-pressure premixed flame of each ester with a molecular beam mass spectrometer. Efforts based on theoretical calculations and extensive literature reviews were devoted to developing a kinetic model which can well predict the current experimental flame structures as well as speciation measurements under pyrolysis conditions reported in literature (Ren et al. (2014)). Model analyses in combination with experimental results helped in revealing the significant effects of specific reactions on the fates of key intermediates in ethyl esters combustion. The competitions between eliminations producing ethylene and acids and hydrogen abstractions by H atoms account for fuel consumptions under flame conditions, but the relative importance of the two reaction categories vary among the three flames. During the shock tube pyrolysis, acids are rapidly produced from fuel decompositions, but consumed in much longer periods, resulting in species formation and enriching the radical pools.