CIMAC Congress - Schiff & Hafen

CIMAC CONGRESS | BERGEN 2010
and by - the turbocharging system. The simultaneous achievement of
emissions compliance, targeted power density and lowest specific fuel
consumption are decisively affected by charge air pressure and
particularly with low speed engines exhaust gas receiver pressure as a
function of engine load and engine speed. Based on these values, the
turbocharger air pressure ratio and efficiency can be derived. Other
parameters, like the specific volume flow of the compressor, variable
elements of the turbocharging system and the design of the
turbocharger itself, are mainly related to economics, servicefriendliness
and reliability as well as to the physical restrictions
imposed by flows and materials. In a first step, this paper discusses the
principal thermodynamic requirements of turbocharger design for
diesel and gas engines with enhanced emissions, higher power density
and optimised fuel consumption and how they have evolved for the
three major engine types i.e. low, medium and high speed. In a second
step, using the evolution of ABB’s A100 turbocharger generation as an
example, the practical realisation of turbocharging systems for the
fulfilment of these requirements is described, including the product
objectives reliability and service friendliness. The paper emphasises
the new technical features against the background of future engine
requirements but also justifies the retention of well-proven principles
from predecessor generations. Finally, the paper concludes with a
summary of field experience to date is given.
TCA33 – the new MAN Diesel turbocharger
for high-speed engines
K. Bartholomae, E. Boelt, D. Balthasar, MAN Diesel &
Turbo SE, Germany
In summer 2008 the decision was made to develop a new turbocharger
for MAN Diesel’s new high-speed engine 28/33D. This turbocharger
should be tailor-made to the particular needs of this engine type. The
development process should profit from all advantages resulting
from the fact that MAN Diesel engines and turbochargers are all
developed under one roof so that the turbocharger is integrated to a
great extent into the engine architecture. As MAN Diesel’s latest
turbocharger the TCA33- 42 extends the TCA axial turbocharger
series towards smaller power outputs. Being the smallest TCA
turbocharger this turbocharger type combines the advantages of the
well-established TCA and TCR turbocharger series. As forerunner for
a new TCA 4- stroke generation the design includes all features
necessary for fulfilling the IMO Tier II regulations. The turbocharger
TCA33-42 is characterized by a high power to weight ratio and high
compactness. The requirement specification also contained highest
pressure ratios up to six in the peak as well as a low mass moment of
inertia, high flexibility for Tier I and Tier II applications to cover all
cylinder numbers from 12V to 20V28/33D. Different rotors are
installed in the same outlines for the different cylinder numbers in
order to keep the mounting variants on the engine and hence the
development effort for the engine customer at a minimum. As many
modern diesel engines, the 28/33D is also designed for Miller timing,
resulting in the demand of a high pressure ratio for the turbocharger.
MAN Diesel has consequently developed special compressor wheels
that also generate the best possible flow rate at a high pressure ratio.
In comparison with previous turbochargers, the increased pressure
ratio results in an increased air temperature and as a consequence to
an increase of the compressor wheel component temperature. If,
however, the use of aluminium as compressor wheel material instead
of titanium should be continued, then the service life of the
compressor wheel will be considerably shortened due to the
accelerated material aging. An efficient compressor wheel cooling
counteracts this drawback. MAN Diesel developed a water cooling
that utilizes the water from the engine circuit and has hence no
influence on the thermodynamic parameters of the turbocharging
unit. Two turbochargers TCA33-42 were mounted on an engine
20V28/33D and successfully tested already one year after starting the
development. At the same time MAN Diesel carried out fundamental
investigations and approval tests at the combustion chamber in
Augsburg. The results of these first operational experiences as well as
the new design features of the new turbocharger are presented.
Development of high-pressure ratio type
turbocharger
R. Murano, K. Nakano, Y. Hirata, IHI, Japan
The raising of the environmental awareness in global scale over the
past few years has lead to the discussion of the prevention of air
pollution by exhaust gas from ship engines at International Maritime
Organization (IMO). The discussion has been held at IMO for many
years. And as a result, MARPOL Appendix VI was established, and the
1 st stage emission regulation became effective in May 2005. The
regulation value is agreed to be adjusted in every five years, so the 2 nd
stage regulation will become effective in Jan 2011. In the 2 nd stage
regulation, NOx has to be reduced approximately 20% more,
compared to the 1 st stage regulation. It is possible to achieve this
desired value by applying mirror cycle timing, which is available by
changing the intake air valve timing in the engine. And for
turbochargers, higher pressure ratio will be demanded to take in
necessary amount of suction air at shorter time. In addition to these
technical demands related to environment, users also strongly require
longer maintenance interval, easier handling, and reduction of life
cycle cost, against turbochargers. Under these circumstances, IHI has
developed the new radial type high-pressure ratio turbocharger based
on a conventional type for 500kW class marine diesel engine. The
main development items are the compressor wheel, the compressor
housing with recirculation device, cooling system of the compressor
back surface, and simplification of maintenance. IHI improved
pressure ratio from 3.8 to up to 5.0 at the engine operation point, by
optimizing the compressor wheel, the diffuser, and also the
compressor housing with recirculation device, by using CFD and so
on. When rising compressor pressure ratio, the compressor wheel is
heated up by the compressed air, and this gives negative effect on life
duration of the compressor wheel. IHI solved this problem by
developing a system to spray lubricant oil on the back plate by way of
cooling the back plate and reducing the radiation heat transferred to
the compressor wheel. A turbocharger for marine diesel engines
requires easy maintenance by the users. This is because that a
turbocharger is usually maintained several times by the users
themselves while on the ship. To answer this request, IHI revised the
design of the housings to make it simpler, and also applied ’seal bush’
type rotor. A ’seal bush’ type rotor separates the turbine side sealing
part as a ’seal bush’ from the rotor, and is easily available to replace
the sealing part for maintenance. These efforts have made IHI
turbochargers more convenient than the conventional. IHI’s highpressure
ratio type turbocharger which has succeeded in various
developments, has already been adopted as a standard model by
some engine builders, and is expected to show its high-performance
in the global market. IHI is continuously developing series of this
turbocharger for 300kW – 400kW smaller marine diesel engines.
High performance of small turbochargers
J. Klima, M. Vacek, O. Tomek, PBS Turbo s.r.o.,
Czech Republic
The papers summarize the latest results for the development of
turbochargers suitable for the latest generation of engines. The
engines have to observe primary emission limits such as IMO Tier
II, TALUFT, which will come into force soon. To meet these limits,
most engine-makers have settled on the design concept of
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Ship & Offshore | 2010 | No. 3