Environmental Engineering Reference
In-Depth Information
Fig. 19 Comparison of the measured evolution of
flame (or outer luminous zone) diameter for a
methyl decanoate droplet with a detailed numerical simulation (solid lines). Data are for the same
droplet as Fig.
18
. The droplets were supported by a SiC
fiber (Fig.
5
), and predictions for various
fiber thermal conductivities are shown (from Liu et al.
2013a
)
fl
simulate more complex combustion con
gurations. Armed with this information,
detailed modeling can then be used to determine with some con
dence the oper-
ational conditions under which the formation of gas products responsible for
degrading fuel ef
ciency can be minimized,
thus increasing fuel ef
ciency of
combustion engines.
7 Summary and Conclusions
The development of surrogates for liquid transportation fuels is one of the most
important problems that will impact the ability to predict in-cylinder processes of
combustion engines using detailed numerical simulation. Real fuels are so complex
that it is not currently possible to develop kinetic and property database inputs
needed to simulate engine performance. Surrogates are the only viable way to
address this problem.
The traditional approach to assessing the performance of surrogate fuels has
been to use low-dimensional combustion con
gurations that require the liquid to be
pre-vaporized. This restriction eliminates from consideration the performance of a
surrogate when multiphase processes are important such as spray injection which
sets the initial conditions for in-cylinder combustion processes. The combustion of
an isolated droplet burning with spherically symmetric gas phase transport provides
a platform that folds into the assessment of a liquid surrogate some of the basic
evaporation and phase equilibrium dynamics of sprays, while at the same time
providing a transport process that is amenable to detailed numerical modeling.
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