Experimental and kinetic modeling studies on the auto-ignition of methyl crotonate at high pressures and intermediate temperatures

Abstract

Biofuels, including biodiesel have the potential to partially replace the conventional diesel fuels for low-temperature combustion engine applications to reduce the CO2 emission. Due to the long chain lengths and high molecular weights of the biodiesel components, it is quite challenging to study the biodiesel combustion experimentally and computationally. Methyl crotonate, a short unsaturated fatty acid methyl ester (FAME) is chosen for this chemical kinetic study as it is considered as a model biodiesel fuel. Auto-ignition experiments were performed in a rapid compression machine (RCM) at pressures of 20 and 40 bar under diluted conditions over a temperature range between 900 and 1074 K, and at different equivalence ratios (ϕ = 0.25, 0.5 and 1.0). A chemical kinetic mechanism is chosen from literature (Gaïl et al. 2008) and is modified to incorporate the low-temperature pathways. The mechanism is validated against existing shock tube data (Bennadji et al. 2009) and the present RCM data. The updated mechanism shows satisfactory agreement with the experimental data with significant improvements in low-temperature ignition behavior. The key reactions at various combustion conditions and the improved reactivity of the modified mechanism are analyzed by performing sensitivity and path flux analysis. This study depicts the importance of low-temperature pathways in predicting the ignition behavior of methyl crotonate at intermediate and low temperatures.