Ginnante_DePellegrin..

Andrea Ginnante, Fincantieri Naval Vessels Business Unit Italy
Conventional Combined Propulsion Systems: The View
From a European Ship Designer and Builder
ABSTRACT
The Fincantieri combined propulsion systems
for naval ships: after a short view of the early
applications of Gas Turbines on Naval Vessels
and
the classic CODOG and COGAG
systems, the propulsion of ships today at sea
trials (Andrea Doria and Cavour) and in
advanced design phase (FREMM) are
examined.
-Two 2,700 t
Frigates Alpino and
Carabiniere, commissioned 1968 (Alpino
radiated few years ago, Carabiniere is still inservice as experiment Ship.
INTRODUCTION
MMI (Marina Militare Italiana)and Italian
Shipbuilder FINCANTIERI soon entered into
the Gas Turbine marine application field,
exploring several applications with different
Classes of Ships.
The parts of the paper are useful to understand
how the propulsion system are influenced by
prime movers existing on the market and from
other factors.
The selection of Propulsion Systems for future
classes of Ships are, more than in the past,
influenced by economical factors that are in
large amount affecting the final decisions of
the users.
CODAG of First Generation
(S. GIORGIO and ALPINO Class)
The history of FINCANTIERI Gas Turbine
Combined Propulsion systems starts in the
early sixties with three very similar propulsion
systems for:
- Transformation of the steam propulsion
destroyer S.Giorgio (former Pompeo Magno
1943) in school Ship for second year academy
cadets (1963-65, radiated 1980)
Fig.1 S.Giorgio, Alpino and Carabiniere G.B.
The propulsion systems of the above
mentioned Ships were of CODAG type. The
two shafts were each powered by one or two
reversible Diesel Engines And Gas Turbine.
The propellers were of Fixed Pitch type.
Each Diesel Engine (4,200 hp), of reversing
type for manoeuvring mode, was connected to
the gearbox via hydraulic couplings. It was
possible to connect each diesel engine to the
high speed drive or to the low speed drive for
single Diesel Engine Mode or Double Engine
Mode and Double Engine Plus Gas Turbine
Mode.
The Gas Turbine was a first generation engine
( G6 Vickers-Metropolitan AEI rated at 7,500
hp). The GT was connected to the gearbox via
a SSS Self Synchronizing clutch.
CODOG(LUPO and MAESTRALE Class)
In the early seventies, while completing the
last
steam Ships, the Italian Navy and
FINCANTIERI started the studies for a new
class of CODOG Frigates.
The result were the successful LUPO (2,500 t)
and MAESTRALE (3,200 t) Classes.
FINCANTIERI built a total of twenty-six
vessels for Italian and foreign Navies.
The GE LM 2500 Gas Turbine, rated at 25,000
hp, was selected as main prime mover and was
installed on board at approximately the same
time as the first US Navy application.
The DD 963 Spruance was commissioned in
1975 and F 564 Lupo in 1977.
The propulsion and power generating system
was on four compartments i.e., a Gas Turbine
room, a Gearbox room and a Diesel
Propulsion/Diesel Generator room plus a
second Diesel Generators room forward. The
Ship’s
mobility
with
two
adjacent
compartments flooded was assured by
watertight gearboxes and suitable auxiliaries
arrangement.
The propulsion diesel engines were GMT
A230.20 connected to the gearboxes trough
friction clutches in air. The DG sets were
based on the same type of engine (6 cyl),
sharing part of the spares. The Gearboxes were
MAAG- Fincantieri and the CP Propellers of
Fincantieri –Lips type.
COGAG GIUSEPPE GARIBALDI
(Aircraft Carrier Cruiser C551)
The Giuseppe Garibaldi (14,000t 30knots)
was delivered in 1985. The Propulsion System
(COGAG) is based on four GTs GE LM 2500,
each rated at 20,000 hp.
The main engine rooms are separated by two
compartments, assuring the Ship’s mobility
with up to three adjacent compartments
flooded.
Each engine room contained two GTs and the
relevant gear box. The propellers are the Fixed
Pitch type. The innovating characteristic of this
combined Ship’s propulsion system was the
introduction of Franco Tosi
Reversing
Coupling Converter for manoeuvring and
reversing mode.
Fig.3 Giuseppe Garibaldi Gearbox with RCCs
Fig.2 Lupo and Maestrale Propulsion Scheme
The Lupo Propulsion System was the first one
fully controlled
by industrial derivative
process computers.
Maestrale (F 570) Class is the enhanced ASW
type respect to Lupo, the propulson concepts
are the same, the propulsion diesel engines are
GMT A.230.20 DVM (Double turbocharging
Variable compression ratio Miller type).
The Ship dimensions made possible to install
the auxiliaries on simple or double resilient
mountings according to necessity. Prairie and
Masker Systems were installed, the C.P.
Propeller rpm lowered respect to Lupo class.
The Franco Tosi RCC is mounted after the first
GB reduction stage from 3600 to about 1500
rpm. In navigation mode the RCC is void, the
SSS Self Synchronizing direct drive coupling
is engaged and the ahead power is directly
transmitted to the secondary pinion.
In manoeuvring mode the power is transmitted
to the secondary pinion via the hydraulic
coupling, ahead or astern following the
position of the reversing stator vanes of the
Reversing Coupling Converter.
The Gearboxes are Maag-Franco Tosi type.
CODOG LUIGI DURAND DE LA
PENNE Class
The Durand De La Penne D 560 ( 5,400 t
DDG) was delivered in 1992. The propulsion
system is the CODOG type.
The prime movers GE LM2500 GT rated at
27,500hp and GMT B230.20 DVM 6,300 hp,
are located one alongside the other in the same
engine room. The two prime movers
compartments are separated by the two Gear
Box compartments; the gearboxes are of
watertight type.
Navy, that was issuing a staff requirement very
similar to the common one of French and UK
Navy, joined the program. Later on UK
decided to pass to a larger, full electric Ship:
the type T45. French and Italian Navy decided
to proceed with the program of building a
common Ship class.
The GT clutches are of SS type and DE
clutches of friction discs type in oil.
A remarkable innovation of this class is the
FINCANTIERI Feathering Pitch Propeller.
The propeller pitch can overcome the design
pitch position arriving to the position of
minimum drag, at about 90°.
The project of the Ship was co-shared between
DCN and FICANTIERI.
FINCANTIERI had the prime contractor role
in Platform and Propulsion System design.
The French Navy FOC (Forbin) started sea
trials in June 2006 and the Italian Navy FOC
(Andrea Doria) in September 2006.
The architecture of the Propulsion System is
the concentrated type, with prime movers and
gearboxes located in the same engine room.
The propulsion studies were initially based on
a CODLOG system with a WR21 Gas Turbine
and an Electric Motor per shaft connected to
the gear Box for manoeuvring and low speed
modes.
The selected solution maintains the general
arrangement described changing into a classic
CODOG system based on a GE-LM2500 Gas
Turbines rated at 20.5MW and a Pielstick
Diesel Engine 12PA6B 4,320 kW per shaft.
Fig.4 Feathering Control Pitch Propeller
It is possible to sustain asymmetric propulsion
with only one shaft propelling the Ship in GT
mode and the other one locked in feathered
position. The Ship can then sustain speeds
higher than possible in Diesel mode, with a
single GT and drag resistance 15-20% less
than with the non propelling shaft in trailed
mode.
Due to the characteristic fuel consumption of
the Gas Turbine versus power, it is possible to
achieve considerable fuel savings in good
portion of the GT mode field.
The FCPP was introduced on all following
CODOG, COGAG and DIESEL Propulsion
classes of Italian Navy.
Fig.5 Horizon forward Engine room
The gearbox is of DCN-PROPULSION design,
shaft lines and propellers (FCCP type) of
FINCANTIERI. The GT clutches are of SSS
type and DE clutches of hydraulic type.
CAVOUR Aircraft Carrier 550
HORIZON CLASS FRIGATES (MMI
First of Class D553 ANDREA DORIA)
The studies for Horizon Class started in 1992
under a cooperation program between the
French and UK Navies. Very soon the Italian
The Cavour is the largest Vessel ever built for
the Italian Navy, 230m in length and nearly
30,000 t of displacement. The Ship will carry
VTOL aircrafts and helicopters.
Today the MMI aircrafts are the Harrier type.
The Ship is designed for this type and for the
future JFS.
The Hangar is able to do a double function,
and can also be used as garage for wheeled
vehicles and 60t battle tanks. The Ship can
carry a full crew plus a marine’s battalion.
The propulsion System was dimensioned to
reach 30 knots of speed.
The Propulsion System is based on four Gas
Turbines GE-LM2500 rated at 22MW, located
in two main engine rooms, coupled via SSS
clutches to two GE-FINCANTIERI gearboxes
of double locked train type. The main thrust
blocks are separated from gearboxes. The
propellers are Feathering Control Pitch type,
FINCANTIERI design and fabrication 6,40 m
of diameter transmitting the full power, 44
MW per shaft at 140 rpm, the largest
power/rpm combination on CPP ever built.
The Gearbox design torque and bearing
reactions afford to reach the maximum power
of GTs even when only one of four is in
service and the non propelling shaft is stopped
with his propeller in feathered position.
Fig.6 CAVOUR Propeller 12 October 2006
A significant note to mention is that the
electric power generation of Cavour is the ring
type based on six DG sets plus two generators
driven by the main shafts. Each generator is
connected to his own main switchboard and
the main switchboards are connected trough a
ring shaped power net. The switches are
electronically controlled.
CODLOG MMI FNG Study/FREMM
In 2002 MMI asked Fincantieri for a PreFeasibility study of a FNG (New Generation
Frigate) in two versions i.e., ASW and GP.
The program was intended for Lupo and
Maestrale Class replacement.
The study received as input constraint to have
common hull and propulsion for the two
versions of Frigate.
The feasibility study had the goal to consider:
- different type of propulsors
- different propulsion system configurations
- number and size of the prime movers
- number and size of electric power sources.
The main operative requirements were fixed:
a) Operative profile per year
30% harbour condition
35% full Ship’s availability in harbor
35% navigation
b) Navigation
50% up to 16 knots
30% 16 to 22 knots
20% 22 to 28 knots
c) Good life cycle cost, suitable Reliability,
Availability, Maintainability and Testability
d) Reduced manning
e) Ship’s speed 28 knots end of life and sea
margin
f) Range 6000 nm @18 knots
g) Vulnerability:
- Shock as per Italian NAV rules
- NBC protection
- Mobility with 2 compartments flooded
h) Signatures:
- very low acoustic signature
- low infrared signature
- low radar signature
g) Power generation:
- 100% redundancy for Ship’s services
- power generation with 3 compartments
flooded
Three propulsor types were considered:
- Propellers (FP and CP type)
- Water jets
- Podded drives
and their behaviour in connection with three
hull forms and necessary appendages, under
the conditions of reference:
- round bilge
- monohull deep vee
- Multi hull (trimaran configuration)
The combination of round bilge and propeller
was selected because good combination
respect to the input data:
- good efficiency for the operative profile
- low acoustic signature
- flexibility in full range
The water jet propulsion system showed better
efficiency than propeller only over 25-26
knots and very good manoeuvring capabilities,
a disadvantage is the noise signature in the
ASW range.
The podded propulsion showed good
advantages as propulsion efficiency and
manoeuvrability,
but
needs
further
development to arrive, for the requested power,
to dimensions compatible with the size of a
frigate. Also problems connected to
vulnerability (shock) and to signatures appear
to be solved.
A promising solution appeared to be a
combination of pods and water jets, but with
problems to be solved by research (layout,
signatures, Pod drive with CPP).
The different form of the hull appeared to be
more or less favourable in combination with
the propulsion types. The MDV type is better
in combination with water jets, in the high
speed field. The trimaran form can be
favourable in connection with propellers and
water jets, but creating constraints to the
internal Ship’s arrangement.
Different propulsion configuration were
examined: CODOG, CODAG, CODLOG,
COGOL, IFEP(Integrated Fully Electrical
Propulsion) together with suitable, available on
the market prime movers (GE-LM2500, GELM2500+, WR21, Diesel Engines @ 10001300 rpm).
The range of options was than restricted by
following considerations:
a) to fulfil speed requirement it was necessary
to embark 44MW and to have available about
10MW for cruise
b)the full electrical propulsion was weighting
more than other solutions in measure to affect
in non negligible way the power need
c) the very tough acoustic requirement
specified was bringing to necessity of low
speed electrical propulsion engines (at shaft
rpm)
d)COGOL arrangement was not supported by
suitable Gas Turbine generators available on
the market.
Conclusion of the FNG study was to look
deeper at the possible CODLOG combinations
powered by a GT per shaft, and electric motors
of size and rpm to be further investigated.
Fig.7 FNG Propulsion study
In 2003 the FNG program was abandoned
because MMI and French Navy decided to join
their efforts in FREMM program (Fregata
Europea Multimissione) together with the
national Shipyards DCN and FINCANTIERI.
The original staff requirements of the two
Navies were not so coincident as for former
Horizon
program,
the
commonality
requirement between French and Italian Ships
was than relaxed were necessary.
Hull and propulsion System are very similar,
combat systems are quite different.
At the beginning of the common work the
CODLOG propulsion system was based on
two Gas Turbines (WR 21 and GE-LM2500
were under consideration) or two electric
motors at main shafts rpm. Propulsion
equipment, power generation and auxiliaries
were distributed on four compartments.
The necessity to contain the Ship’s cost
brought to compromises not considered for
FNG study.
The propulsion passed to a CODLOG system
based on a single Gas Turbine and two parallel
shafts, the propulsion and DG rooms were
contained in 2 main machinery spaces plus a
forward Diesel Generators and emergency
/manoeuvring retractable propeller.
The forward main engine room accommodates
the propulsion turbine, the gearbox and two
diesel generator sets in acoustic enclosure,
double resiliently mounted.
The aft main engine rooms accommodate the
electric motors, the thrust blocks and
auxiliaries.
A peculiarity of MMI Ships will be to have
reversible Electric Motors i.e., it will possible
to use the EM as driven generators when the
Ship is under way in GT mode at propulsion
power lower than maximum.
Moreover the MMI ship will have Controllable
Pitch Propellers, than the Ship will have
possibility to cover the full operation range
from full ahead to full astern in GT mode.
CONCLUSION
Looking at FNG to FREMM passage is clear
how considerations different from the initial
requirements can lead to a more economically
optimised solution with marginal modifications
of the initial requirements.
Fig.8 FREMM Propulsion Arrangement
As consequence of passage from two to a
single GT it was necessary to consider more
powerful Gas Turbines. The attention shifted
to new candidates: RR MT30 rated at 34MW
and GE LM2500+G4 rated at 32MW@25°C.
This last engine was selected in 2005.
Both of them are able to insure the requested
speed of more than 27 knots end of life with
sea margin.
The main gearbox is composed by three bodies
i.e., the first one for primary reduction and for
splitting the power on the two shafts and the
other two, symmetrical, for final reduction
stage.
The electric motors are directly connected to
the shaft lines; the gearbox is not in use during
the electric propulsion mode. The power of
electric motors was limited to about 2,5MW.
This power is sufficient to sustain speed in
excess of 16 knots. The generator sets are 4 x
2.1 MW, two of them in GT room and two in
forward generator room.
Fig.9 FREMM Propulsion rooms arrangement