Combustion kinetic studies of future transportation fuels and intermediates

Abstract

The transportation sector requires an abundant supply of fossil and/or bio-derived fuels, which all produce significant quantities of greenhouse gas (GHG) emissions. The transportation sector is expected to account for nearly 55% of liquid fuel demand in the next two decades, with a majority share occupied by gasoline-powered light-duty vehicles. To mitigate emissions and increase engine efficiency, it is critical to understand the impact of a fuel’s combustion properties on internal combustion engine performance. The potential future fuels considered in this thesis include alcohols (prenol), cycloalkanes (cyclopentane), ketones (cyclopentanone), esters (methyl and ethyl acetate) and un-saturates (di-isobutylene) that can be produced from biomass and can also be blended with conventional liquid fuels to tailor the fuel properties required to optimize advanced internal combustion engines. These hydrocarbons can also act as ‘surrogate’ molecules. Since the complex molecular structures of real fuels result in many obstacles for carrying out auto-ignition experiments in laboratory scale facilities, and in the development of chemical kinetic models, the ‘surrogate’ molecules are selected to represent the physical and chemical properties of real fuels of interest and can reproduce critical engine phenomena of interest. In addition to the fuels mentioned above, critical intermediates which are almost ubiquitously formed in the decomposition of higher hydrocarbons, such as acetylene, iso-butene and iso-butane were also studied in this work. An extensive experimental campaign leading into investigations of a physiochemical fuel property i.e. ignition deal time (IDT) of these hydrocarbons were carried out in two independent but complimentary experimental facilities namely a high pressure shock-tube (HPST) and a rapid compression machine (RCM). These measurements were carried out covering a wide range of conditions, including T = 600 – 1400 K, p = 10 – 40 bar for fuel in O2 and N2 mixtures covering equivalence ratios of, φ = 0.5 – 2.0 relevant to internal combustion engine operation. In addition, detailed kinetic models were also developed in external collaboration to describe the oxidation mechanism of the fuels and validated against the experimental data generated in this work and also with a wide range of data available in the literature.