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Cimac Congress | Shanghai 2013
low frequency plane wave range and high frequency non-plane
wave range. The low frequency plane wave range acoustic source
characteristics of an IC engine can be determined accurately by
using for example process simulation software and acoustic multi-load
methods. If the diameter of the studied duct is small as in
automotive systems, the low frequency plane wave range source
characterisation might be enough. When studying noise from a
medium-speed power plant or marine IC engine, the duct diameters
are large and therefore the acoustic source characteristics in
the high frequency nonplane wave range are also important. The
goal of this study is to estimate how the acoustic source data of
a medium-speed IC engine exhaust system can be determined in
the low frequency plane wave range and also in the high frequency
non-plane wave range using engineering practices and acoustic
power based methods. In this study the source characteristics are
determined based on simulations and measurements, then the
low- and high-frequency source characteristics are combined in a
way that allows them to be used in multiport simulations.
The effect of piston structure parameters on the
lube oil consumption
Jilin Lei, Zhejiang University, China
Xiaoli Yu, Zhejiang University, China
Jun Wen, Chendu Galaxy Power Co, Ltd, China
Lizhong Shen, Kunming University of Science and Technology, China
Zhentao Liu, Zhejiang University, China
Based on the measurement of temperature filed of piston and
cylinder sleeve, the dynamic model of 2D25 diesel piston assembly
was established. The effect of piston structural multi-parameters
and single parameters on lube oil consumption was analysed
by orthogonal experimental design method and conventional
method, and the single parameters, including the radial clearance
between piston skirt, piston head and cylinder inner wall,
and piston pin offset. The results indicate that the radial clearance
between piston skirt and cylinder inner wall has the greatest
impact on the lub-oil consumption, followed by the piston head
radial clearance and the piston pin offset. The convex position of
piston skirt profile, stiffness and ovality of piston skirt had little
impact on the oil consumption. The lub-oil consumption had
little change with the radial clearance between piston skirt and
inner wall from 0.06mm ~ 0.09mm, but the lub-oil consumption
increased rapidly when the radial clearance between piston
skirt and inner wall was at the range of 0.09mm ~ 0.15mm. The
lub-oil consumption had a little increment with the piston head
radial clearance. The lub-oil consumption was the lowest when
the piston pin offset to main bearing surface was 0.5mm, and
the lub-oil consumption was increasing with piston pin offset
to main bearing surface was increasing, but the range was not
obvious.
Thursday May 16th / 08:30 – 10:00
Users´ Aspects
Marine Application – Service Experience
Room B
Service experience of MAN B&W two-stroke diesel
engines – an update
Stig Baungaard Jakobsen, MAN Diesel & Turbo, Denmark
After the introduction of the Tier II versions of the MAN B&W
M-range of two-stroke diesel engines, around 85% of all new
orders are specified as electronically controlled ME/ME-C/ME-B
types. This trend is covering all engine sizes; however the trend
is most dominating for large-bore engines (80, 90, 98) where
nearly 100% of all orders are specified in electronic controlled
versions. It is therefore of extreme importance that the ME engines
have reached a matured development status and this paper
confirms that this is indeed the case. Today, the ME engine concept
is widely accepted among major shipowners and the benefits
of electronic control is seen more and more as the concept
is enhanced with features as auto-tuning, integrated control of
exhaust bypass, variable turbine area turbochargers, turbocharger
cut-out and in the near future (Tier III era) integrated control of
exhaust gas recirculation, water in fuel emulsion and SCR. An
update of service-related issues on the electrohydraulic control
will be given. The continued change in economics for shipping
following the worldwide financial crisis starting in autumn 2008
has called for continued focus on extreme low continuous load
operation of several types of vessels. This focus started for large
container vessels operated down to 10% load continuously. However,
now it also becomes relevant for other ship types like tankers
and bulkers. An update on service experience will be given,
including service experience with ’high-pscav tuning’ as retrofit.
Lower design speed for newly ordered ships has called for new
engine types in various types of vessels applying larger diameter
and more efficient propellers. For large container vessels, about
8,000 - 14,000 TEUs, the S90ME-C engine in Mark 8 and Mark 9
versions have become new industry standard. An update on service
experience with this new application of the well-proven S90
engine, formerly predominantly specified for VLCC propulsion,
will be given. The trend of applying lower propeller revolutions
on various ship types has also called for the introduction of the
ultra-long stroke G-type engine series. Early service experience of
these engines will be given. Common for both the ME/ME-C and
the MC/MC-C engine series is the well-documented possibility to
do condition based overhaul (CBO) with average time between
overhauls (TBOs) of 32,000 hours and above. For tankers, this
opens up the possibility to do only major overhauls at dockings
with five years interval. Many shipowners do now have the experience
with CBO. Development of a new piston ring package for
small bore engines (50 bore and lower) has made it possible also
to enjoy extended time between piston overhauls on these engine
types. The so-called POP (Port On Plane) top piston ring will also
be introduced.
Diesel engines optimisation and fuel savings
Magnus Karlsson, Stolt Tankers BV, The Netherlands
The aim of this paper is to present how to achieve a reduction of
fuel oil consumption and maintenance cost through optimisation
of diesel engines. Furthermore, the paper will also handle
combustion-related problems of Marpol Annex VI emission Tier
I, low NOx settings of diesel engines and diesel engine optimisation
in general. All presented cases are real and are backed up
with real combustion diagrams, measurements and calculations
carried out during performance and energy audits onboard Stolt
Tanker’s vessels by the author of this paper. The author has as
well attended several factory acceptance tests for diesel engines. A
diesel engine combustion analyser instrument is used when carrying
out the performance tests of diesel engines onboard vessels.
Based on the results from the combustion diagrams achieved
from the combustion analyser and other relevant performance
data, the diesel engines are optimised for improved performance.
The work process in the combustion diagrams will be explained
and also how the diagrams should look like to achieve the most
efficient combustion. The paper will show examples of diesel alternator
engines with Marpol Tier I low NOx emission settings.
The paper reveals that newly installed diesel engines on vessels
optimised in compliance with low NOx emission limitations
68 SPECIAL
Schiff&Hafen | Ship&Offshore | May 2013