TURBO NEWS

Press release
Premiere at the Ammersee
In the heart of Bavaria: the new TCA turbochargers
Herrsching, 7 May 2002 – Today sees the unveiling of an ocean-going product deep in
the heart of land-locked Bavaria: the lake at Ammersee near Munich is where large-bore
engine manufacturers MAN B&W Diesel, represented by Board-member Fritz Pape,
present their new TCA ("TurboCharger Axial") turbocharger series to the world's press.
Two years in the making, the first production turbocharger, the TCA77, has gone into
service with an MAN B&W 7S50MC-C two-stroke Diesel engine. "The TCA turbocharger
will set new standards in both performance and serviceability, and at the same time
bring down lifecycle costs and installation outlay", says Rolf Studte, head of the
turbocharger division at MAN B&W Diesel AG. Employing leading-edge design and
development tools, MAN B&W were able to go far beyond their initial goals in a number
of respects.
The new turbocharger development combines a radial-flow compressor wheel with axial-flow
turbine blading. The first production turbocharger from this series is the TCA77. Additional framesizes,
from the TCA33 all the way up to the TCA99, are already under development. In order to
cover as broad a range of applications as possible the new turbocharger is of modular design.
Air is sucked in either via an intake air intake silencer, a 90-degree intake casing or an intake
manifold. The exhaust gas from the combustion process flows into the turbine via either an axialor
a radial-flow casing. The new TCA series also boasts the proven separate-casing-base
concept from the NA series. It is this design concept that makes this series adaptable to the
turbocharging requirements of the application in question. The compressor volute is available
with either one or two opposing thrust pieces. The single-piece variant is advantageous in twostroke
and four-stroke in-line engines. The two-piece volute offers considerable advantages
when attaching a single turbocharger to V-type four-stroke engines.
Adjustable nozzle ring
The intake air is compressed by the compressor wheel, which is driven by the turbine. Both the
compressor wheel and the turbine can be adjusted to engine requirements by choosing from a
range of meridians and blading configurations. Diffusers and nozzle rings which are very finelystepped
in their mass-flow areas allow the turbochargers to be fine-tuned to the engine. For
maximum variability an optional nozzle ring capable of adjustment during operation will be
available in the near future.
All TCA turbochargers come equipped with a minimum of external connections. On the engine
side and in the plant system itself the only additional connections, apart from the air and exhaustgas
connections already mentioned, is an oil inlet and drain pipe, together with a breather
connection for the bracket. The TCA requires neither cooling-water nor lock-air connections, let
alone an external luboil supply. In order to ensure that it can continue to operate in an
emergency, the unit can be supplied with a special emergency operation facility integrated into
the turbocharger. The TCA series represents the consistent continuation of the "pipeless engine"
principle.
Press release
All the turbocharger's hot casing components are equipped with a new temperature and noisereducing
casing with a sturdy sheet-metal cover. This casing significantly reduces the risk of
engine-room personnel being injured by coming into contact with excessively hot surfaces in
installations where the turbocharger is in an accessible area.
Building on their almost 70 years of experience, MAN B&W have designed the TCA series with
inboard sleeve bearings. Surrounding these core components is a compact, powerful
turbocharger designed to meet the following key design goals:
·  high specific flow rates
·  high efficiencies
·  low noise emissions
·  ease of maintenance
·  ease of engine mounting
·  high reliability and long service life
In order to limit bearing losses the shaft diameter of the rotating assembly was reduced. In so
doing, particular attention was paid to rotor dynamics so that, despite the reduction in the shaft
diameter, it proved possible to increase rotor stability still further compared with the NA-series
turbochargers. The rotating assembly is mounted in the bearing casing on two floating-sleeve
radial bearings. Since the floating-sleeve design of bearing significantly reduces the rate of shear
in the bearing gaps in comparison to the fixed-sleeve type, both bearing losses and bearing wear
are reduced.
The thrust bearing is equipped with a floating centre plate which acts in the same way as the
floating-sleeve radial bearings. The thrust bearing is located outside the radial bearing on the
compressor side. This means that it can be removed easily without having to dismantle the
radial bearing and rotating assembly. The fact that the thrust bearing is subject to far greater
stresses than radial bearings, because of the axial thrust of the turbine and the compressor,
makes this feature a significant one for ease of maintenance.
The bearing points are supplied with oil by a ring channel arranged in the inside of the bearing
casing. Oil feed, either from the right or left side of the turbocharger, distribution of the luboil to all
the bearing points and supply of the optional emergency luboil service tank, are via this ring
channel. The principle of the "pipeless engine" is continued simply, but efficiently, in the
turbocharger. This significantly reduces the work involved in connecting the turbocharger to the
engine.
Oil mist instead of water cooling
None of the TCA turbocharger bearing casings is water-cooled - not even in the largest framesizes,
the TCA88 and TCA99. The heat brought in by the compressor and the turbine is
dissipated in the luboil flung off the shaft of the rotating assembly. The oil mist thus generated
can drop down the walls of the very generously-dimensioned interior of the bearing casing,
thereby evenly absorbing the heat which is to be dissipated. The bearing casing boasts its own
air vent, which can likewise be connected to the left or right. This air vent ensures that the
leakage air which the compressor inevitably forces into the bearing casing through the shaft seal
of the rotating assembly does not increase crankcase pressure in the engine, but instead is
dissipated directly.
All the airflow components of the TCA turbocharger have been optimised with regard to flow
configuration and stress reduction using state-of-the-art 3-D CFD and FEM analysis. The result
is a turbine with 41 so-called "wide-chord" blades arranged in a fir-tree root in the turbine disc.
The characteristic feature of wide-chord blades is their very high chord-to-height ratio. This
Press release
produces a compact-looking, very stiff and hard-wearing turbine blade. For engine matching the
turbine blades can be of varying angles and lengths. With the aid of leading-edge design tools it
is now possible to dispense with lacing wire to dampen exhaust-generated vibrations, even in
four-stroke engine applications. Apart from improving the blade profile, this has also been an
immense boost to efficiency.
Centrifugal force like a fully-loaded truck and trailer
As in the thousands of NA-series turbochargers, the turbine shaft is friction-welded to the turbine
disc. The turbine disc, which in the TCA77 must absorb a centrifugal force per turbine blade
equivalent to the weight of a fully-loaded truck and trailer, is made from a forged steel alloy. It
was designed to the same specifications as its NA-series equivalent, which is renowned for not
having suffered a single case of turbine-disc failure at any time in its long and distinguished
production life. Nozzle rings, with their new design of blade profile and a very carefully matched
turbine outlet diffuser, also contribute to the gain in efficiency.
The core component of the compressor is the compressor wheel. It is operated at
circumferential speeds well in excess of 500m/s, generating very considerable centrifugal
forces. In order to be able to withstand these forces the compressor wheel is made of a highstrength
aluminium alloy. A specially-developed process for manufacturing the master material
ensures a longer lifetime for a component which is subjected to considerable stresses. For
applications where the units will come into contact with corrosive media, a special corrosionresistant
coating can be applied to the compressor wheel. MAN B&W have many years of
positive experience with coatings of this kind.
A new design of compressor volute and new designs of nozzle ring ensure optimum
turbocharger matching and contribute to the high efficiency of the TCA turbochargers. On the
one hand the shaft-hub connection between the compressor wheel and the turbine shaft has a
key influence on turbocharger behaviour: on the other, removal has to be easy if the rotating
assembly requires frequent re-balancing. With this in mind a completely new system of
compressor mounting had to be developed.
The compressor wheel is deformed by the powerful centrifugal forces acting on it. This tends to
cause it to expand across its diameter, and this inevitably provokes a shortening in axial
direction, causing the bore to widen. The new design ensures good centering of the compressor
wheel on both the inlet side as well as to the labyrinth ring in the plant system itself. The tiebolt
compensates the axial shortening. An adapted tightening system allows a small torque wrench
to produce the required tiebolt tensioning. This reduces assembly and dismantling work to a
minimum as this system can still be removed easily, even after lengthy periods in service.
The very good centering makes it possible to remove and replace the compressor wheel without
needing to re-balance the rotating assembly. Individual component balancing means that
component-related imbalance problems are now a thing of the past. With its ease of assembly
and dismantling this MAN-B&W-patented shaft-hub connection sets new standards in
serviceability.
Noise emissions in a turbocharger occur primarily at the compressor wheel. Any measures
aimed at reducing noise emissions therefore concentrate on the cold area of the turbocharger.
Noise is generated by a combination of pressure fluctuation in way of the compressor wheel inlet
and the interaction between the compressor wheel and the diffuser.
Inlet-side noise emission was reduced by optimising the fluid mechanics of the compressor
wheel. The aim was to find the best compromise between high compressor efficiency and noise
emission. Additionally, the silencer was designed with radially-arranged curved plate elements.
Press release
With this innovative silencer concept noise emissions can be dampened to a very high degree
whilst intake pressure losses are kept low.
Major noise reduction
In order to reduce noise radiation in the engine's charge-air manifold the number of blades in the
diffuser was matched to the number of blades in the compressor. In addition, the compressor
volute was provided with a noise-reducing casing. Together all these measures significantly
reduce the level of noise emissions compared with the NA series. The goal of lowering noise
emissions below the level of 105 dB(A) at 1 m distance, the figure that in future will be demanded
by the mariners' associations and classification societies, was achieved comfortably.
The TCA is the first MAN-B&W turbocharger series to have been designed entirely with the aid of
the 3-D CAD system Pro/Engineer. This offered significant advantages both in the design of raw
castings as well as in the finish-machining of individual turbocharger components. A process
has been developed for designing castings which allows us to develop the raw casting and the
finished component almost completely in parallel at different locations. Having access to shared
data meant that our production facilities were able to make use of design data at a very early
stage and plan machining and the construction of jigs and fixtures. This simultaneousengineering
effect significantly shortened development time. It also ensured that the foundry,
design and production divisions were able to work very closely together, and this impacted
positively on the production turbocharger at a very early stage in the manufacturing process.
This significantly reduced the development time of the TCA77 from preliminary design to finished
prototype.
3-D CAD models of all TCA turbocharger models are available to our engine designers. With all
the key dimensions for turbocharger connection stored in a spatial volume model, optimum
matching of the TCA turbocharger to the engine is possible as early as the planning phase and
attachment analyses can be conducted effectively at a very early stage. The experience gained
with attaching the TCA77 to MAN B&W's 12V48/60B and to other engines produced by the MAN
B&W Group shows that this method offers significant advantages for the engine designer.
The MAN B&W Diesel Group is the world's leading supplier of large-bore Diesel engines for
marine propulsion and power stations with unit outputs of up to 80 MW. The two- and four-stroke
engines produced by MAN B&W Diesel and our licensees account for some 50 per cent of the
world market, making them the world market leaders. The company is also one of the world's
leading suppliers of Diesel power stations and turbochargers. With some 7 300 staff and
production facilities in Germany, Denmark, the United Kingdom, France and Singapore the
Group Division generates annual sales of approx. 1.5 billion euro. MAN B&W Diesel is an affiliate
of MAN Aktiengesellschaft, Munich. The MAN Group is one of Europe's leading suppliers of
commercial vehicles and mechanical and plant engineering products with sales of some 16
billion euro and a workforce of 77 000 staff.
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