CIMAC Congress - Schiff & Hafen

Monday, 14 June
Tuesday, 15 June
Thursday, 17 June
Wednesday, 16 June
emissions, as well as on Specific Fuel Oil Consumption (SFOC) are
quantified. For the cases of unmodified fuel injection, representative
results indicate that a reduction in NOx of approximately 85% is
achieved with DWI, and of 60% with intake water addition, for
water mass levels of 50% and 200% of the injected fuel mass,
respectively. Under those conditions, SFOC is increased by
approximately 4.5% and 2.0%, respectively, accompanied by nonnegligible
increase in the emitted soot levels. By systematically
varying the locations of the water injectors, as well as fuel injection
timing, it has been possible to maintain the same levels of NOx
emissions reduction, with milder penalties in SFOC and soot
emissions. The present detailed study suggests that: (a) the 2016
NOx emission standards could be met by proper water injection
strategies, (b) further improvements in emissions levels and engine
performance would be feasible in terms of optimized water and fuel
injection, based on rigorous optimization studies.
A combined numerical and experimental
study on the influence of the injection
system on the spray, the combustion and
emissions in medium speed diesel engines
C. Fink, H. Harndorf, Rostock University, Germany,
M. Frobenius, AVL Deutschland GmbH, Germany,
R. Pittermann, WTZ Rosslau gGmbH, Germany
In cooperation with several partners a project funded by the German
government was initiated in order to investigate the emission
reduction potential of modern common-rail injectors using different
marine fuels. The experimental and numerical study focuses on
engine part load and low temperature (Miller-cycle) conditions, as
these conditions are mainly causing high smoke and particulate
emissions. The first part of the project includes the experimental
and numerical analysis of injection sprays in a high pressure/high
temperature research chamber at Rostock University. In order to
account for nozzle internal effects, a coupled simulation method
between the nozzle internal flow and the spray is applied. The CFD
simulations have been performed using the CFD Code FIRE, which
provides a modern nonlinear cavitation model combined with
advanced turbulence modelling techniques to account for transient
cavitation effects in the needle seat area and in the nozzle. By means
of a special polymer moulding technique, real nozzle geometries
were derived and considered in the simulation of the nozzle internal
flow pattern. The obtained flow conditions are then used as input
data for the spray simulation. Here, besides the droplet primary and
secondary break-up and droplet collision models, a new advanced
evaporation model considering droplet internal flows has been
applied. The developed models have been validated against
experimental data obtained in the optically accessible high pressure/
high temperature research chamber at Rostock University. Different
optical methods are applied in order to quantify the characteristic
spray parameters penetration length, cone angle, droplet size and
velocity. Good correlations of the experimental and simulation
results are observed, which confirm the applicability of the developed
simulation models for the simulation of the mixture formation in
the engine. In the second part of the project, the spray and mixture
behaviour as well as the combustion and emission formation in a
single-cylinder medium speed engine is investigated. The ECMF-3Zcombustion-model
has been applied for the simulations together
with an advanced NOx-model and a new developed kinetic soot
model. The complex combustion and emission generation processes
are investigated experimentally at the WTZ Rosslau gGmbH. A single
cylinder medium speed research engine is equipped with the same
common rail injector as used at Rostock University. Optical
measurements of flame temperatures and soot concentration inside
the cylinder are done for several variations. Filter smoke numbers
(FSN), particulates (mass, composition, size distribution) and
gaseous emissions are measured giving insight into emission
generation mechanisms. As smoke emissions during low loads are
mainly caused by oxygen lack, those conditions were counted for by
a reduced charge air pressure of the auxiliary blowers. To investigate
parameters for smoke emission reduction, the influence of the rail
pressure, the injection timing and multiple injections on the smoke
reduction was analysed. Good agreement of calculated and measured
incylinder pressure traces as well as pollutant formation trends
could be observed for the investigated arameter variations. The
combined numerical and experimental study shows the potential of
further emission reductions by the use of the flexible common-rail
system. The developed coupled simulation method can improve the
understanding of the influence of the nozzle flow conditions and
the spray characteristics on combustion and emission behaviour.
Predictive simulation of combustion and
emissions in large diesel engines with
multiple fuel injection
G. Pirker, B. Losonczi, W. Fimml, A. Wimmer,
F. Chmela, LEC - Large Engines Competencce Center,
Austria
Reliable simulation tools for preoptimization of the engine cycle are
necessary in order to minimize the time and cost of development of
a new engine and to fulfil future requirements for performance,
efficiency and emissions. As the number of adjustable parameters in
engine control continues to grow, an ever larger number of variants
must be investigated when optimizing the entire system.
Zerodimensional simulation processes with simple handling and
short calculation times have proven to be advantageous. The shaping
of the injection rate through multiple fuel injection has likewise
proven to be an effective measure for reducing particulate emissions
in large diesel engines, especially when using exhaust gas
recirculation. Thus the reliable pre-calculation of combustion using
different injection strategies is increasing in importance. A consistent
simulation methodology describing the processes in internal
combustion engines has been developed at the LEC in recent years.
In this article, the continuing development of a combustion model
for large diesel engines is presented with a special emphasis on the
detailed modeling of the injection spray. An extended spray model
succeeds in describing the mixing process for operating points with
multiple fuel injection, which is a requirement for the prediction of
burn rate and emissions. Exact knowledge of the injection parameters
is essential as the basis for the burn rate calculation with multiple
fuel injection in particular. To this end, a combined measuring
system for determining the rate of injection, spray velocity and the
amount of fuel injected has been developed at the LEC.
13:30 June 16th Room Klokkeklang
(5–2) Component & Maintenance Technology –
Piston Engines – Wear & Monitoring
Contact pressure and temperature
prediction in a marine piston ring
D. Grunditz, H. Pedersen, H.-G. Qvist, S. Grahn,
Daros Piston Rings, Sweden
A novel simulation method is proposed for predicting temperature
field and ring-liner contact pressure for a given top piston ring
design and given engine operating conditions. The method employs
AVL Excite to predict the blow-by gas flow rate and pressure difference
No. 3 | 2010 | Ship & Offshore
79