CIMAC Congress - Schiff & Hafen

CIMAC CONGRESS | BERGEN 2010
are tested combined with both high and low engine loads. The
same setup with the highest rail pressure is used for all the run
loads. The results show that there is a clear dependency between
the injection parameters and the engine performance. An
optimization may be possible but the overall view of all the main
engine outcomes has to be taken into account.
Predictive simulation and experimental
validation of phenomenological
combustion and pollutant models for
medium-speed common rail diesel engines
at varying inlet conditions
P. Kyrtatos, P. Obrecht, K. Boulouchos, ETH Zürich,
Switzerland,
K. Hoyer, Paul Scherrer Institut, Switzerland
As internal combustion engines are becoming ever more complex,
there is increasing need for engine parameter optimization through
simulation, to avoid numerous timely and costly test-bed
measurements. When performing simulations for engine
performance and emission optimization, the capability of the
combustion model used to accurately predict NOx emission
formation as well as heat release rates at varying engine conditions
becomes increasingly important. Considering the trade-off between
computational cost and accuracy of predictions of diesel engine
combustion and pollutant models, phenomenological models have
a clear advantage compared to their CFD and simple mathematical
approximation alternatives. The detailed phenomenological model
used in this study is able to capture changes in fuel injection system
and charge-air thermal and chemical properties for direct injection
diesel motors, while being computationally efficient. This paper
aims to show the ability of these models to predict diesel combustion
and emission formation during significantly varying inlet charge
and injection conditions, in common rail medium-speed diesel
engines. Initially the phenomenological models are calibrated using
measurement data from a production common rail medium-speed
Wärtsilä 6L20CR diesel engine, employing a state-of-the-art
turbocharging system. The model calibration includes data from
experiments where injection timing and pressure as well as engine
load were varied, to determine their influence on combustion and
NOx emissions. The models are then used to predict the heat release
rate and NOx formation when the inlet valve timing is changed to
earlier Miller timing and the charge air pressure is raised using twostage
turbocharging. Additionally, the models are embedded in a
1-D simulation model of the engine to predict the resulting engine
performance. The simulation results are compared with experimental
results obtained from the test engine with matching hardware
changes, giving an indication of the models’ ability to capture the
most important combustion and emission formation characteristics.
Results from the study show very good performance of the
combustion and emission models, when used to perform operating
map-wide simulations with varying fuel injection conditions. When
the models are used to predict heat release rate in the two-stage
turbocharged engine with Miller timing, the combustion rate is
predicted well, with small discrepancies in ignition delay calculation.
The emission model correctly forecasts the reduction in NOx
emissions as a result of the advanced Miller valve timing, but
underestimates the true level of NOx produced. Overall, the
combustion and emission models show good performance, and
their short calculation time allows them to be used for multi-variable
engine optimization within the calibration ranges. With
improvements in the ignition delay and NOx calculation, the
models can additionally be used for preliminary engine concept
design studies and turbocharger matching through simulation.
Emission reduction potential of 3000 bar
common rail injection and development
trends
S. Pflaum, J. Wloka, G. Wachtmeister, Technical
University of Munich, Germany
Due to the introduction of new emission limits, engine developers
are forced to optimize both, combustion process and peripheral
equipment of diesel engines. For this purpose peripherical systems
like the cooling system, the exhaust-gas-recirculationsystem (EGR)
and the injection system play a major role. Beside cooling- and EGRsystem
highly affecting the generation of nitrogen oxide (NOx)
emissions, the soot production is primarily influenced by the
injection system. To investigate and develop new combustion
processes the Chair of Internal Combustion Engines (LVK) at the
Technische Universitaet Muenchen (TUM) developed a novel singlecylinder-research-engine,
equipped with a special EGR system and a
3000 bar common rail system. This common rail system based on a
standard 1800 bar system had to be adapted and redeveloped for
the extremely high injection pressures. The LVK-Research-Engine
itself was build for combustion pressures up to 300 bar, which is
high above series. The first engine tests with the new 3000 bar
injection system showed a great correlation between the injection
pressure and the emission. As the extremely high injection pressures
in combination with standard injector nozzles (designed for
1800 bar) did not yet produce satisfying emission results, the LVK
started to adapt and design new nozzles for this high injection
pressures. The development process of the new highpressure-nozzles
is based on Computional Fluid Dynamic (CFD) calculations, which
show the diesel flow in the injector nozzle holes. After adapting the
calculations to the new high-pressure range, the influence of the
different geometry parameters, like nozzle-hole number, diameter,
conicity and degree of hydro erosive (HE)-rounding of the nozzle
holes was studied. With consideration of the needs of a low-emission
combustion process, the new, adapted nozzles for high pressures
were designed by CFD and manufactured by drilling and HErounding.
The high-pressure-nozzles were mounted in the LVK-
Research-Engine for further investigations. The emission behaviour
of the new nozzles was tested and validated in the research engine.
With the new high-pressure-nozzles remarkable good emissionresults
could be achieved. The 3000 bar common rail system with
the new CFD-optimized nozzles showes big potential to comply
with EURO VI
in a distinctive area of the engine map. Beside the described
development process the paper will discuss engine development
trends concerning also costs, lifetime and potentials, like reduction
of emission and fuel consumption by applying new, adapted highpressure-injection-systems
(up to 3000 bar and above). In addition
some future visions will be presented.
NOx emission reduction by use of N 2
diluted charge air
O. Melhus, I. J. Garasen, B. Haukebo, K. K. Langnes,
Ecoxy AS, Norway,
D. J. Stookey, Compact Membrane Systems, Inc.,
USA,
J. E. Hustad, Norwegian University of Science and
Technology (NTNU)
In the years from 2004 to 2009 Ecoxy has tested three different ways
to dilute the charge air for NOx reducing purposes. EGR is a wellknown
measure to reduce NOx from diesel engines and has been
extensively used for automotive diesel engines for a number of years.
For marine diesel engines, which run on totally different types of
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Ship & Offshore | 2010 | No. 3