Combustion kinetic studies of future transportation fuels and intermediates

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2020-10-22Author
Lokachari, Nitin
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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.