화학공학소재연구정보센터
Fuel, Vol.251, 162-174, 2019
Predictions of oxidation and autoignition of large methyl ester with small molecule fuels
Biodiesel contains large methyl esters including methyl palmitate (MP), methyl oleate (MO), methyl linoleate (ML), etc. Long alkyl chains and asymmetric structures of these large methyl esters lead to complexity in development of kinetic models. In this paper, surrogate fuels for large methyl esters were proposed and developed. Surrogate models can be used to replace the detailed mechanisms of large methyl esters in prediction of oxidation and autoignition properties. Key characteristics in combustion have non-linear relationships with fuel components in a neural network diagram, which indicates that surrogates with the same functional groups can exhibit similar combustion properties as large methyl esters. In formulation of surrogate fuels, candidates consist of small species such as methyl decanoate, n-hexadecane, methyl trans-3-hexenoate, and 1, 4-hexadiene. To compare the oxidation properties, point-to-point experimental validations were conducted in laminar flow reactor. Oxidation properties of surrogate and target fuels were in satisfactory agreements. Surrogate fuels not only successfully captured the discrepancies in reactivity of different methyl esters, but also reproduced species concentrations of intermediate and products at various equivalence ratios. To test the performance in predicting autoignition characteristics, simulations based on surrogate models were compared with previous experimental data. Surrogate models not only predicted ignition delay times at various pressure and equivalence ratios, but also reproduced the trends of apparent activated energy under different conditions. To sum up, oxidation and autoignition characteristics of large methyl esters can be predicted by the combined kinetic model of small molecule compounds, which will have great potentials in the development of kinetic models for fuels with complicated molecular structures.