Experimental and chemical kinetic modeling investigation of methyl butanoate as a component of biodiesel surrogate

Biodiesel is a potential alternative to fossil diesel. In combustion simulations, in order to circumvent the difficulty in integrating reaction schemes for biodiesels, which are typically of a large size and not well understood, a surrogate approach to simplify the representation of its long chain methyl ester components is adopted. In this work, a compact reaction scheme for methyl butanoate, which is a potentially important candidate for biodiesel surrogates, is derived from a detailed reference mechanism (Dooley et al., 2008). An existing well-validated model for n-dodecane (Narayanaswamy et al., 2014) oxidation, which is a suitable base to model biodiesel surrogates, is augmented with the oxidation pathways of methyl butanoate. The resulting combined mechanism is comprehensively assessed for methyl butanoate kinetic description. Several rate constants pertaining to methyl butanoate kinetics are updated in the resulting chemical mechanism based on recent rate recommendations from the literature in a consistent manner. The revised kinetic model has been validated comprehensively against a wide range of experimental data and found to be satisfactory. In addition, auto-ignition delay times of methyl butanoate have been measured in a rapid compression machine (RCM). The ignition delay time measurements cover a wide range of experimental conditions: temperatures of 850-1100 K and pressures of 10-40 bar. The impact of varying equivalence ratios on ignition delay times has also been investigated for ϕ = 0.5-1.5 and ignition delay times are reported for the rich mixtures for the first time as a part of this work. No two-stage ignition or negative temperature coefficient (NTC) behavior has been observed for methyl butanoate in the experimental investigation. The effect of addition of low-temperature chemistry pathways to the methyl butanoate chemical kinetic mechanism has also been explored.