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@PHDTHESIS{Kerschgens:538518,
author = {Kerschgens, Bruno},
othercontributors = {Pitsch, Heinz Günter and Pischinger, Stefan},
title = {{S}imulation of unconventional fuels for diesel engine
combustion},
school = {Zugl.: Aachen, Techn. Hochsch.},
type = {Dissertation},
address = {Aachen},
publisher = {Shaker},
reportid = {RWTH-2015-05342},
isbn = {978-3-8440-3910-8},
series = {Berichte aus der Energietechnik},
pages = {XII, 115 S. : Ill., graph. Darst.},
year = {2015},
note = {Druckausgabe: 2015. - Auch veröffentlicht auf dem
Publikationsserver der RWTH Aachen University 2016; Zugl.:
Aachen, Techn. Hochsch., Diss., 2015},
abstract = {This study focuses on computational fluid dynamics (CFD)
simulationsof diesel engine combustion of unconventional
fuels. The fuels are: A diesel/gasoline blend,
di-methyltetrahydrofurane (2-MTHF), a blend of 2-MTHF and
di-n-butylether (DnBE), n-octane, DnBE, and n-octanol.
Experimental data from two different diesel engine test
benches are available for comparison and validation of the
simulations. Good results regarding pressure traces, heat
release rates, and pollutant emissions are obtained. Fuel
property effects are analyzed individually and detailed
insights into the interdependencies of fuel molecular
structure and combustion behavior are gained. Simulations
are perfomed using the Representative Interactive Flamelet
(RIF) model, which has been applied in many studies modeling
compression ignitionin internal combustion engines. By the
use of detailed chemical reaction mechanisms, the RIF model
inherently accounts for low and high temperature
auto-ignition, heat release, and pollutant formation. For
simulation of the novel fuels in this study, the modeling
approaches had to be adapted and assumptions had to be
reassessed. To validate the spray representation and to set
the model parameters of the liquid breakup model,
simulations of a spray vessel experiment using several fuels
are performed and compared to the respective experimental
data. The first fuel to be analyzed by simulation and
experiment is a diesel/gasoline blend. Here, the
experimental aim is to reduce the ignitability of the fuel
to enable longer premixing duration and thus low temperature
combustion. This presents a step towards tailoring a
fuel’s properties to the requirementsof the combustion
system. A surrogate fuel blend is used to describe there
action chemistry of the diesel/gasoline blend, which is a
common modeling approach for complex liquid hydrocarbon
fuels. The surrogate composition is chosen to match several
kinetic properties of the fuel blend. Increased emissions of
carbon monoxide and rather high emissions of nitrogen oxides
are observed experimentally. The simulations show where
these originate, how this is related to the modified fuel
properties, and how the emissions could possibly be reduced.
The next two fuels in this study are neat
di-methyltetrahydrofurane (2-MTHF) and a blend of 2-MTHF and
di-n-butylether (DnBE). As biofuel candidates, these fuels
have a very promising performance in the diesel engine
experiments. Their reaction chemistry is described by a
surrogate mixture, which represents a new aspect to a
reaction chemistry surrogate. Here, not a mixture of
hundreds or thousands of hydrocarbons is modeled by a
reducedset of fuels, like for the diesel/gasoline blend
above, but one single and one dual component fuel with only
roughly known reaction chemistry are modeled by a well
defined mixture of fuel components. The methodology to
define this mixture is described in detail. Comparisons with
diesel engine experiments and homogeneous reactor
experiments confirm the approach and the methodology to
define the surrogate composition, and demonstrate that the
approach allows for insights into the pollutant formation
processes in the engine. The final set of fuels in this
study are three n-C8 fuels, namely n-octane, DnBE, and
n-octanol. These fuels feature very similar molecular
structures, but very different spray formation, ignition,
and combustion properties. As such, they present an example
to understand the influence of small changes in molecular
structure on the combustion behavior. For the simulations
oft hese fuels, detailed reaction mechanisms are used.
Results are analyzed to investigate the effects of mixture
formation, fuel stoichiometry, and reaction chemistry
individually. Pollutant emissions are found to be mainly
dependent on the time available for premixing of the charge,
as reflected by the cetaneratings of the fuels. The
substantially lower cetane rating of n-octanol compared to
n-octane is explained by analysis of engine simulations and
homogeneous reactor calculations. These fuels have similar
ignition delay times in homogeneous reactor experiments, but
quite different ignition behavior in engine relevant
conditions. This is shown to be a strong effect of the
fuel’s stoichiometries, rather than being related to the
very different spray properties of the fuels.},
cin = {411410},
ddc = {620},
cid = {$I:(DE-82)411410_20140620$},
typ = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
urn = {urn:nbn:de:hbz:82-rwth-2015-053423},
url = {https://publications.rwth-aachen.de/record/538518},
}
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