Chemical Kinetic Influences of Alkyl Chain Structure on the High Pressure and Temperature Oxidation of a Representative Unsaturated Biodiesel: Methyl Nonenoate

The high pressure and temperature oxidation of methyl <i>trans</i>-2-nonenoate, methyl <i>trans</i>-3-nonenoate, 1-octene, and <i>trans</i>-2-octene are investigated experimentally to probe the influence of the double bond position on the chemical kinetics of long esters and alkenes. Single pulse shock tube experiments are performed in the ranges <i>p</i> = 3.8–6.2 MPa and <i>T</i> = 850–1500 K, with an average reaction time of 2 ms. Gas chromatographic measurements indicate increased reactivity for <i>trans</i>-2-octene compared to 1-octene, whereas both methyl nonenoate isomers have reactivities similar to that of 1-octene. A difference in the yield of stable intermediates is observed for the octenes when compared to the methyl nonenoates. Chemical kinetic models are developed with the aid of the Reaction Mechanism Generator to interpret the experimental results. The models are created using two different base chemistry submodels to investigate the influence of the foundational chemistry (i.e., C0–C4), whereas Monte Carlo simulations are performed to examine the quality of agreement with the experimental results. Significant uncertainties are found in the chemistry of unsaturated esters with the double bonds located close to the ester groups. This work highlights the importance of the foundational chemistry in predictive chemical kinetics of biodiesel combustion at engine relevant conditions

A Shock Tube Study of <i>n</i>- and <i>iso-</i>Propanol Ignition

An understanding of the ignition and oxidation characteristics of propanol, as well as other alcohols, is important toward the development and design of combustion engines that can effectively utilize bioderived and bioblended fuels. Building upon a database for “first-generation” alcohols including methanol and ethanol, the ignition characteristics of the two isomers of propanol (<i>n</i>-propanol and <i>iso</i>-propanol) have been studied in a shock tube. Ignition delay times for propanol/oxygen/argon mixtures have been measured behind reflected shock waves at temperatures ranging from approximately 1350 to 2000 K and a pressure of 1 atm. Equivalence ratios of 0.5, 1.0, and 2.0 have been used. Pressure measurements and CH* emissions were used to determine ignition delay times. The influences of equivalence ratio, temperature, and mixture strength on ignition delay have been characterized and compared to the behavior seen with a newly developed detailed kinetic mechanism. The overall trends are captured fairly well by the mechanism, which include a greater level of reactivity for the <i>n</i>-propanol mixtures relative to <i>iso</i>-propanol at the conditions used in this study