A shock tube study of methyl decanoate autoignition at elevated pressures

A shock tube study of the autoignition of methyl decanoate, a candidate surrogate for biodiesel fuels containing large methyl esters, has been carried out. Ignition delay times were measured in reflected-shock-heated gases by monitoring electronically-excited OH chemiluminescence and pressure. Methyl decanoate/air mixtures were studied at equivalence ratios of 0.5, 1.0, and 1.5, at temperatures from 653 to 1336 K, and for pressures around 15–16 atm. The experimental results illustrate negative-temperature-coefficient behavior characteristic of alkanes, with ignition delay times very similar at high temperatures and somewhat longer at low temperatures than those for n-decane. Experimental results are compared to the kinetic modeling predictions of Herbinet et al. [Combust. Flame 154 (2008) 507–528] with remarkable agreement. Both reaction flux analysis and the comparison of experimental methyl decanoate and n-decane ignition delay times illustrate the importance of the long alkyl chain in controlling methyl decanoate overall reactivity and the subtle role the methyl ester group has on inhibiting low-temperature reactivity.