Shock tube studies of methyl butanoate pyrolysis with relevance to biodiesel
Davidson, David Frank
Hanson, Ronald Kenneth
Westbrook, Charles K.
KAUST DepartmentClean Combustion Research Center
Physical Sciences and Engineering (PSE) Division
Mechanical Engineering Program
Chemical Kinetics & Laser Sensors Laboratory
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AbstractMethyl butanoate pyrolysis and decomposition pathways were studied in detail by measuring concentration time-histories of CO, CO 2, CH 3, and C 2H 4 using shock tube/laser absorption methods. Experiments were conducted behind reflected shock waves at temperatures of 1200-1800K and pressures near 1.5atm using mixtures of 0.1%, 0.5%, and 1% methyl butanoate in Argon. A novel laser diagnostic was developed to measure CO in the ν 1 fundamental vibrational band near 4.56μm using a new generation of quantum-cascade lasers. Wavelength modulation spectroscopy with second-harmonic detection (WMS-2f) was used to measure CO 2 near 2752nm. Methyl radical was measured using UV laser absorption near 216nm, and ethylene was monitored using IR gas laser absorption near 10.53μm. An accurate methyl butanoate model is critical in the development of mechanisms for larger methyl esters, and the measured time-histories provide kinetic targets and strong constraints for the refinement of the methyl butanoate reaction mechanism. Measured CO mole fractions reach plateau values that are the same as the initial fuel mole fraction at temperatures higher than 1500K over the maximum measurement time of 2ms or less. Two recent kinetic mechanisms are compared with the measured data and the possible reasons for this 1:1 ratio between MB and CO are discussed. Based on these discussions, it is expected that similar CO/fuel and CO 2/fuel ratios for biodiesel molecules, particularly saturated components of biodiesel, should occur. © 2012 The Combustion Institute.
SponsorsThe experiments were performed at Stanford University. The kinetics work of the Stanford authors was supported by the Combustion Energy Frontier Research Center (CEFRC) and the diagnostic development work by the Air Force Office of Scientific Research (AFOSR) with Drs. J. Tishkoff and C. Li as technical monitors. The work by Dr. Westbrook of Lawrence Livermore National Laboratory was supported by the US Department of Energy with program managers Gurpreet Singh and Kevin Stork.
JournalCombustion and Flame