Environmental Engineering Reference
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Developing Surrogates for Liquid
Transportation Fuels: The Role
of Spherically Symmetric Droplet
Combustion
C. Thomas Avedisian
Abstract The
finite supply of transportation fuels has generated renewed interest to
improve their performance in power and propulsion devices. However, the com-
plexity of real fuels prohibits developing their combustion chemistries and property
databases needed for simulating performance in engines to identify operational
regimes for improving fuel ef
ciency. Surrogates offer the means to address these
concerns if they can be shown to replicate certain combustion targets of the real fuel,
and to result in combustion properties similar to real fuels when burned in a suitable
con
guration that is amenable to detailed numerical modeling. This paper examines
the role which droplet combustion can play in the development of surrogates for
complex transportation fuels. Recognizing that spray combustion is far too dif
cult
to model and that droplets represent the
fine-grid structure of sprays, the combustion
dynamics of fuel droplets are examined in an environment that seeks to remove
external convective in
field and produce spherical
symmetry in the droplet burning process that can be modeled using a detailed
numerical simulation approach. The one-dimensional flames and transport dynamics
that result are shown to be well positioned to evaluate the ef
fl
uences to simplify the transport
cacy of surrogate fuel
performance. Recent efforts are summarized that have used the spherical droplet
fl
guration to evaluate the performance of surrogate fuel blends. Experi-
ments are discussed for promoting spherical symmetry, and results are presented to
show the ef
ame con
cacy of some surrogate blends to replicate the performance of gasoline
and jet fuels using the spherical droplet con
guration. Some results are also included
from detailed numerical modeling of biodiesel droplets that incorporate complex
combustion chemistry, and unsteady transport, vaporization, and variable property
effects that illustrate the potential for high
fidelity predictions needed for developing
surrogates using the spherically symmetric droplet
fl
ame con
guration.
This paper is based on a presentation given at the Indo-US International Workshop on Novel
Combustion for Sustainable Energy Development, Kanpur, India, January 2
-
4, 2014.
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