THESIS
Issues on clean diesel combustion technology
using supercritical fluids: Thermophysical properties and thermal stability of
diesel fuel
by Lin, Ronghong, Ph.D., SYRACUSE
UNIVERSITY, 2011
Abstract:
Clean diesel combustion technology using supercritical fluids aims both to
improve fuel economy and reduce emissions. This novel process involves
preparation, injection and combustion of supercritical fuel/diluents mixtures.
Design and development of the process require a deep understanding of fuel properties.
The current study attempts to address three fuel property related issues: fuel
surrogates, diffusivity and thermal stability.
Fuel surrogates are often used in engine
research to mimic real fuel properties. In this work, ten diesel fuel surrogates
were investigated, and the ability of these surrogates to predict diesel fuel
properties was evaluated. It was found that none of them were able to predict
all properties of interest including volatility, critical points, density,
viscosity, heat capacity, and thermal conductivity. Different surrogates are
suggested for predictions of different properties.
The effects of temperature, residence time and
CO2 on thermal stability of diesel fuel at high temperatures were investigated
by both batch and continuous thermal stressing experiments. Results showed that
thermal stability of diesel fuel decreased as temperature and residence time
increased. 400-420?C was found to be the optimal temperature range where
supercritical fuel delivery and combustion could work. The presence of 10 wt%
CO2 reduced accumulation of solid deposits due to enhanced solvent capacity.
However, CO2 was not likely to have the ability to chemically prevent fuel
coking. Solid deposits of different sizes, morphologies and structures were observed
at 300-440°C, which implies different deposit formation mechanisms.
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