A lumped approach to the kinetic modeling of pyrolysis and combustion of biodiesel fuels

The aim of this work is to discuss a lumped approach to the kinetic modeling of the pyrolysis and oxidation of biodiesel fuels, i.e. rapeseed and soybean methyl esters. The lumped model is the natural extension of the kinetic scheme of methyl butanoate and methyl decanoate and takes also a great advantage from the detailed kinetic scheme of biodiesel fuels [Westbrook et al. Combustion and Flame 158 (2011) 742–755]. The combustion of methyl palmitate and methyl stearate is very similar to the one of methyl decanoate, while large unsaturated methyl esters are significantly less reactive at low and intermediate temperatures. The formation of resonantly stabilized allylic radicals from unsaturated methyl esters constitutes a critical element very useful to characterize the reactivity of the different fuels. The extension of the previous kinetic model of hydrocarbon and oxygenated fuel combustion to the methyl esters required the introduction of 60 lumped species and 2000 reactions. The dimension of the overall kinetic scheme (420 species involved in 13,000 reactions) allows a more flexible and direct application of the model without the need of kinetic reductions. The comparison of model predictions and different sets of experimental data from one side allows to verify the reliability of the proposed model, from the other side calls for further experimental and theoretical work on this subject.