CIMAC Congress - Schiff & Hafen

CIMAC CONGRESS | BERGEN 2010
combustion chamber. First results show that endoscopic in-situ
investigations of the combustion process can give feasible data for
validating CFD combustion simulation models. The used CFDmodels
are capable of predicting standard measurement data of
medium speed diesel engines like cylinder pressure, heat release rate
or NOx emissions without adjustment of model parameters. The
comparisons of spatially resolved data show that the used CFD
models are capable of predicting important trends, but that they are
not yet accurate enough for getting exact agreement with the optical
images. Nevertheless, the observed deviations between spatially
resolved details represent valuable information about how to further
optimize the CFD models with a focus on medium speed diesel
engines.
Fuel injection strategies for heavy fuel
medium speed engines to comply with
future emission limits
R. Rabe, M. Epp, H. Harndorf, E. Hassel, C. Fink,
University of Rostock, Germany
To fulfil prospective emission regulations, IMO Tier III engines must
be able to adjust themselves to operating conditions and to fuel
quality currently applied. This requires the implementation of an
optimal combustion control strategy to distinguish between HFO
and distillate fuel operation. The research objective at the University
of Rostock is to find fuel injection strategies for efficient and
emission-minimised combustion of maritime fuels. The
conventional fuel injection system of the heavyfuel capable singlecylinder
research engine has been replaced with a CR injection
system, a freely programmable research engine control unit and
fitted with optical accesses. With this HFO-capable, needle controlled
CR injection system which allows up to five independent injection
events per working cycle, the medium-speed single-cylinder research
engine offers ideal conditions for research. Results from other
analysis facilities at the University of Rostock, i.e. the CR injection
rate analyser, the high-pressure / high-temperature chamber, the
optical and laser-optical research tools and the DOE-Method are
validated with the single cylinder HFO- research engine. Thereby, a
detailed understanding of the relationships between different CR
injection strategies, fuel quality, combustion and emission formation
processes is gained. This serves as a valuable foundation for future
engine control strategies and engine internal emission reduction. As
a result, engine-type independent basics for the functions to be
integrated in engine control units are created, allowing injection
adapted to the pertaining emission limits and the operation
conditions of the individual fuels and fuel qualities. The test engine
and the optical and laser-optical analysis tools used are presented in
the paper. Furthermore, Injection Rate Analyzer studies such as the
injection rate dependency on fuel viscosity and the viscosityinfluence
on fuel spray penetration depth found in the highpressure/high-temperature
chamber are shown. Their effects on the
engine’s emission process depending on the fuel and its conditioning
are discussed. Further research projects will be presented.
Experimental and computational
considerations of fuel spray mixing
H. J. Hillamo, V. Vuorinen, T. Sarjovaara, O. Kaario, M.
Larmi, Aalto University School of Science and
Technology, Finland
Fuel sprays play major role in primary emission reduction of diesel
engines. In this study fuel sprays have been studied in pressurized
measurement chamber. Experimental fuel spray imaging results
were analyzed by image processing techniques to analyze mixing
and the internal structure of the sprays. The interesting features of
sprays include shear layer vortices, interaction of droplets with the
vortices and subsequently mixing. To support these views we offer
possible explanations to mixing using Large-Eddy Simulation (LES)
of a spray jet. The LES results support the experimental picture on
spray formation mechanisms. In specific, LES reveals that droplet
size is an important parameter and closely related to mixing.
Turbulent diffusion of droplets is also demonstrated in the LES
simulations. Measurements were performed using both laser sheet
imaging and back-light imaging. The inner structures of fuel spray
and turbulent mixing were of interest. Ambient conditions were
non-evaporative. The tests of the common rail diesel engine injector
have been done at pressurized injection test rig. In diesel sprays the
inner structures of spray can have high effect on mixing and those
structures are monitored. Turbulence levels in fuel sprays have high
importance to mixing of fuel and air. Used procedure reveals inner
structures of spray, and the growth of structure sizes of droplet
clusters (more concentrated areas of spray). In the near nozzle area
the occasional change in concentration of droplets is most likely
dominated by nozzle effects, but after the spreading of spray and
complete atomization, the more concentrated areas of spray are
formed due to flow effects. Certain estimations of droplet size
distribution can be linked to experimental data.
8:30 June 16th Room Troldtog
(3–7) Environment, Fuel & Combustion –
Diesel Engines – Modelling I
Aspects of emulsified fuel spray
combustion in a high-pressure and hightemperature
atmosphere
H. Okada, T. Tsukamoto, H. Sasaki, Tokyo University
of Marine Science and Technology, Japan,
T. Ohtsuka, Ibaraki Prefectual Kaiyo High School,
Japan
Marine diesel engine-operation with emulsified fuels is an effectual
method for NOx reduction as the Tier II regulation controls applied
from 2011 in IMO. Previous studies revealed that the emulsified fuel
improved the thermal efficiency, and suppressed the formation of
thermal NO and soot particles (carbon components etc) in diesel
engine due to the secondary atomization caused by the microexplosion.
However, the micro-explosion phenomena and the
behavior of water particles in the emulsified fuel droplets are not
clear enough to understand its effects on combustion. The process
of spray formation, ignition and combustion of emulsified fuel
spray in high-pressure and high-temperature atmosphere which
corresponds to burning condition in marine diesel engines was
investigated by using the equipment involving a combustion
chamber (386’×533), a fuel injection system was able to single
diesel spray and a fuel nozzle of marine diesel engine. The
experiments were conducted in a variety of conditions of ambient
gas pressure up to 6.9MPa, the ambient gas temperature up to 900K,
the fuel injection pressure up to 75MPa, and the nozzle opening
pressure was 31.4MPa. The emulsified fuel was a mixture of water
particles dispersed in marine diesel fuel (MDF). We made the
different water content emulsified fuel oil with the emulsifier. It was
found that as follows:
(1) The spray angle of fuel became wide following the increase of
injection volume and ambient gas pressure regardless of water
contents. Its angle of emulsified-fuel became a little narrow for
increasing of penetration by high density with water content in
compared with MDF.
(2) The position of occurring first flame exists at the mixing part
66 Ship & Offshore | 2010 | No. 3