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7/27/2019 Advanced Machinery With CRP Propulsion for Fast Rpax Vessels.pdf
1/17
April 10-11th, 2002
Oskar Levander Advanced machinery with CRP propulsion for fast RoPax vesselsWrtsil Corporation / Marine Division The Motorship Marine Propulsion Conference 2002
Oskar Levander
Advanced machinery with CRP propulsion for
fast RoPax vessels
ABSTRACT
The hydro-dynamical benefits of CRPpropulsion have been presented several times inthe past years. This paper describes how thepropulsion arrangement can be optimist and themachinery configured in RoPax vessels withpodded CRP propulsion. Some interestingmachinery solutions are also presented.
The propulsion efficiency of the CRParrangement depends on the power split betweenthe propulsors. However, the power split givingthe best efficiency does not result in the most
cost-effective option when the transmissionlosses, capital cost and the operating profile are
taken into account. The method for reaching themost cost efficient solution is explained.
The combined diesel-electric and diesel-mechanical machinery (CODED) used with
podded CRP propulsion shows great benefitsand possibilities for future RoPax vessels.
Dual Fuel-engines running on LNG are shownto be an interesting option for environmentallyfriendly RoPax vessels.
INTRODUCTION
This paper will examine both technical as wellas economical aspects for two new machineryand propulsion concepts for fast displacementRoPax vessels.
One of the new concepts features a CombinedDiesel-Electric and Diesel-mechanical(CODED) machinery in combination with a
propulsion configuration based on amechanically driven propeller in front of an
electric pod with a contra-rotating propeller(CRP). Two Wrtsil diesel engines drive the
single mechanical CP propeller through a twin-in / single-out gearbox, while the electrical podunit is powered by a diesel-electric power plant
type machinery. As an example, two alternativeCODED machinery versions have beendeveloped, one for a 30 knot and the other for a28 knot service speed.
FIGURE 1. Fast RoPax vessel with podded CRP propulsion
7/27/2019 Advanced Machinery With CRP Propulsion for Fast Rpax Vessels.pdf
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April 10-11th, 2002
Oskar Levander Advanced machinery with CRP propulsion for fast RoPax vesselsWrtsil Corporation / Marine Division The Motorship Marine Propulsion Conference 2002
The other concept is based on dual fuel engines
in combination with CRP propulsion. In thisconcept, both the pod as well as the shaft
propeller is electrically driven and the power isprovided with a power plant type machinery,
which also supplies the hotel load. In thisalternative Wrtsils Dual Fuel (DF) gasengines are applied and liquid natural gas (LNG)
is used as the primary fuel with marine diesel oil(MDO) as back up fuel.
Both machinery concepts are applied to twoRoPax vessel design, which have beendeveloped in co-operation between WrtsilCorporation and Kvaerner Masa-YardsTechnology as part of the Finnish research
project SEATECH 2000+.
CASE STUDY VESSELS
Vessel Design
Totally new ship designs have been developedfor the fast RoPax vessel. Two versions will be
used in this paper to illustrate the newpropulsion and machinery concepts. The first
one is intended for a long route with overnightoperation. The other is intended for short routes
with only daytime transits. This version has adrive-through car deck and is slightly shorter.All three alternative machinery versions, the 28and 30 knot CODED machinery as well as the28 knot DF-electric machinery, can been appliedto both vessels. The main dimensions are
indicated in table 1 and the general arrangement
of the long route vessel is shown in figure 2.
The superstructure, housing either day facilitiesfor 2000 passengers or overnight facilities for
900 person in 300 cabins, is located in theforward part of the ship leaving the aft end ofthe upper car deck open. The cargo is
transported on the two large RoRo decks.Trailers and trucks are loaded on the main deck,which has 4,8m free height over the entire deck.High vehicles can also be carried on the openpart of the upper deck. The enclosed forwardpart of the upper deck is used solely for privatecars due to the restricted free height. The hullsides are flared out to increase the width of the
RoRo decks, while keeping the breadth at the
waterline level narrow. This makes it possible toincrease the number of lanes and thereby thelane meters without impacting on the resistance.The enlarged car decks also makes it possible tocarry all cargo on two decks and no lower holdis needed. This allows for faster loading and
unloading since no internal ramps are used. Theloading and unloading of vehicles is handled
over the double level stern ramps directly toboth the main and upper deck. The simple andfast cargo-handling concept is in line with thehigh-speed philosophy of this ship. The shortroute vessel features an additional bow ramp fordrive through loading.
The hull is of full-displacement type and
features a very long and slender form with asingle centreline skeg to offer the lowest
possible resistance.
TABLE 1. Main properties of the vessels
L O N G R O U T E S H O R T R O U T E
L e n g th , o a 2 4 6 2 2 0 m
L e n g th , d w l 2 3 0 2 0 5 m
B e a m , h u l l 3 0 3 0 m
B e a m , d w l 2 8 2 7 m
D ra u g h t , d w l 7 7 m
P a s s e n g e r s 9 0 0 2 0 0 0 p e r s o n s
P a s s e n g e r s c a b in s 3 0 0 - p c s
L a n e m e te r s 1 7 4 0 1 5 0 0 m
B u s e s 2 4 - p c s
P r iv a te c a r s 2 0 0 3 5 0 p c s
D W T 4 2 0 0 4 2 0 0 to n
7/27/2019 Advanced Machinery With CRP Propulsion for Fast Rpax Vessels.pdf
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April 10-11th, 2002
Oskar Levander Advanced machinery with CRP propulsion for fast RoPax vesselsWrtsil Corporation / Marine Division The Motorship Marine Propulsion Conference 2002
FIGURE 2. General arrangement of the 30 knot long route RoPax vessel.
7/27/2019 Advanced Machinery With CRP Propulsion for Fast Rpax Vessels.pdf
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April 10-11th, 2002
Oskar Levander Advanced machinery with CRP propulsion for fast RoPax vesselsWrtsil Corporation / Marine Division The Motorship Marine Propulsion Conference 2002
Itineraries and operating profiles
Three example routes have been selected for thecase vessels to give a realistic operating profilethat can be used in the evaluation of the
machinery concept. The same ship conceptcould of course be used on many otheritineraries in other parts of the world.
The 30 knot ship is intended to operate on alonger route, in this case between Helsinki inFinland and Rostock in Germany. The distancelogged between these cities is 585 nauticalmiles. This means that one leg takes less than 20hours with a service speed of 30 knots. The timefor manoeuvring, loading and unloading is
estimated to take four hours. A one way trip can
therefore be covered in less than a day. A returntrip takes 48 hours, which enables a single shipto depart every second day at a fixed time.Alternatively, two ships can offer dailydepartures.
585 n.m.
50 n.m.
535 n.m.
FIGURE 3. The three alternative routes used for
the case vessels.
The 28 knot ship is a more suitable choice for a
short route where the time in port takes up alarger part of the total time. A crossing over theGulf of Finland between Helsinki and Tallinn isused as the example for the short route in thisstudy. The leg is about 50 nautical miles so itcan be accomplished in roughly 2 hours. Areturn trip is estimated to take 8 hours, which
means that a single ship can offer two dailydepartures from both cities. The ship has only
day facilities for the passengers and no cabins,since it will stay in port during the night.
The ship with overnight facilities in combinationwith the machinery offering a speed of 28 knot
could of course also be operated on a long route.
A route between Hanko in Finland and Rostockin Germany is used as an example. This route is
about 50 nautical miles shorter, than theHelsinki-Rostock trade which means that the 28
knot ship can maintain the same 48 hours roundtrip schedule as her faster sister vessel.
The operating profiles for the vessels areindicated in figure 4 and 5.
OPERATING PROFILEHELSINKI - ROSTOCK
0 %
10 %
20 %
30 %
40 %
50 %
60 %
70 %
80 %
90 %
Port
Man
.10 15 20 25 30
Max
Operatingtime[%]
FIGURE 4. Operating profile for the long route.
OPERATING PROFILEHELSINKI - TALLIN
0 %
10 %
20 %
30 %
40 %
50 %
60 %
70 %
80 %
90 %
Rest
Port
Man
.10 15 20 25 28
Max
Operatingtim
e[%]
FIGURE 5. Operating profile for the short route.
7/27/2019 Advanced Machinery With CRP Propulsion for Fast Rpax Vessels.pdf
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Oskar Levander Advanced machinery with CRP propulsion for fast RoPax vesselsWrtsil Corporation / Marine Division The Motorship Marine Propulsion Conference 2002
THE PODDED CRP CONCEPT
Both ship versions have a podded CRPpropulsion concept with a contra-rotatingpropeller mounted on an electrical pod located
directly behind a single conventional propellerlocated on the centreline skeg. (This propulsionarrangement will be referred to as the poddedCRP concept or just the CRP concept in this text
unless otherwise mentioned.) The propellermounted on the pod is of a fixed pitch (FP)
model, while the mechanically driven propelleron the mechanical shaft is of the featheringcontrollable pitch (CP) type.
FIGURE 6. A contra rotating pod behind a
conventional CP propeller.
Characteristics of the podded CRP concept
The podded CRP configuration offers betterhydrodynamical efficiency, compared to aconventional vessel with twin screws on longopen shafts supported by brackets, due to the
following reasons:n The aft propeller takes advantage of the
rotative energy left in the slipstream of the
forward propeller when it turns in theopposite direction. This improves the
rotative efficiency (hR) of the propulsion.
n The single skeg hull form offers a more
favourable wake than an open shaft line,
resulting in better hull efficiency (hH).
n The resistance of the single skeg hull formwith a single pod is lower than that of a twinscrew hull with two open shaft lines.Especially the lack of appendages, such asrudders, shaft brackets, bossings and sternthrusters contributes to the lower resistance
of the single skeg hull.
The improvement in propulsion efficiency has
been quantified with model test by at least twoindependent model test basins. Both ABB and
Blom&Voss have conducted podded CRP testson RoPax vessels at Marintek and HSVA
respectively. Both tests have showed efficiencyimprovements of over 15% compared toconventional vessels (Jokela 2002) (Praefke et al
2001). The Germans were even able to reach anefficiency improvement of 19 % when speciallydesigned propellers were applied instead ofstandard stock propellers.
The podded CRP drive also offers otherbeneficial characteristics such asn Excellent manoeuvring performance thanks
to the pods ability to turn 360o
and thereby
direct the thrust in any direction.n Better reversing capabilities. The pod can be
turned around 180 degrees, while thepropeller still turns in the same optimumdirection. Important feature with high skewpropellers.
n The steering capability should be maintainedduring crash stops thanks to the electric pod.
However, this has not yet been proven bymodel test.
n Better redundancy compared to a singlescrew or a conventional CRP system. Thepod and the mechanical drive are separatelydriven.
The podded CRP concept features proven and
reliable components combined into a newconfiguration. This way mechanical problems
associated with the shafting and sealing ofconventional mechanically driven CRP systems,which feature an inner shaft rotating inside andhollow outer shaft, are avoided.
CRP power ratio optimisation
The power split between the electric pod and themechanical propeller influences many aspects ofthe design and performance of the ship, such asthe hydrodynamic efficiency, the transmissionlosses and the investment cost. A total approachmust be taken when optimising the power split
between the pod and the conventional propellerin order to reach the most economical solution.
The power split between the two propellers has
an influence on the hydrodynamic efficiency ofthe propulsion and thereby on the delivered shaft
7/27/2019 Advanced Machinery With CRP Propulsion for Fast Rpax Vessels.pdf
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Oskar Levander Advanced machinery with CRP propulsion for fast RoPax vesselsWrtsil Corporation / Marine Division The Motorship Marine Propulsion Conference 2002
power demand. This can be seen in figure 7
where the blue line indicates the delivered shaftpower demand at different power ratios.
However, there is very little informationavailable on this subject and the source data
behind the picture can not be considered reliablefor this type of application. Even though thefigure does not necessarily give exactly the
correct values, it still shows the principal inquestion. It can be seen that there is an optimumpower ratio, which is close to 50/50, in order toachieve the highest efficiency. When the powersplit is moved in either direction, there will bean increase in the power demand.
However, the delivered power at the propeller is
not the hole truth when seeking the lowest fuel
costs, it is the brake power demand at the dieselengines that determines the fuel consumption.The transmission efficiency must therefore alsobe taken into account. The losses associated withelectrical propulsion are about 8%, which can becompared to about 2-3 % for the mechanical
propulsion. The brake power demand atdifferent power ratios is also indicated in figure
7. It can be seen that the increase in brake poweris not as rapid as the corresponding increase inshaft power when reducing the power share ofthe pod from the optimum value (moving to the
left in the graph). The lowest value is still
reached at a power-split ratio of about 50 %though.
The investment cost must also be included when
optimising the machinery configuration for besteconomical performance. The much highercapital cost of the electrical propulsion part
compared to the mechanical propulsion trainwill have a big impact on the optimum powerratio for lowest total costs. This means that morepower should be on the mechanical propellerthan on the pod in order to reduce the capitalcosts and thereby lower the total machineryrelated cost of the ship.
The cost efficiency at different pod power ratios
for the RoPax operating the longer route isindicated in figure 8. The most economical pointof operation according to this graph is at apower split of 40/60 between the installed powerof the pod and the mechanical propeller and notat point where the lowest fuel consumption is
reached. The curve is very flat, so the powersplit could be varied from the optimum without
much impact on the total costs, especially byreducing the electrical pod size. This would beinteresting, in order to reduce the electricalinstallations onboard.
CRP EFFICIENCYFOR DIFFERENT POD POWER RATIOS
90 %
95 %
100 %
105 %
110 %
115 %
120 %
25 30 35 40 45 50 55 60 65
POWER SPLIT: [%]
POD POWER/ TOTAL DELIVERED POWER
POWER[%]
Break power
Shaft power
FIGURE 7. Estimated relative power demand at different power-split ratios between the pod and the
mechanical propeller.
7/27/2019 Advanced Machinery With CRP Propulsion for Fast Rpax Vessels.pdf
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April 10-11th, 2002
Oskar Levander Advanced machinery with CRP propulsion for fast RoPax vesselsWrtsil Corporation / Marine Division The Motorship Marine Propulsion Conference 2002
CRP COST EFFICIENCY FOR THE FAST ROPAXAT DIFFERENT POD POWER RATIOS
LONG ROUTE
0 %
20 %
40 %
60 %
80 %
100 %
120 %
20 25 30 35 40 45 50 55 60
POWER RATIO: [%]
POD POWER / TOTAL INSTALLED PROPULSION POWER
ANNUALCOST[%]
Total annual cost (incl.
operating and capitalcosts)
Annual operating cost(incl. fuel, lube oil, andmaintenance costs)
Annual capital cost
FIGURE 8. Cost efficiency at different pod power ratios for the RoPax operating the longer route.
The operation profile has also a big influence onwhich power ratio that offers the lowest totalcosts. This can be seen when comparing figure 8with figure 9. (It might be worth noticing thatthese figures show the power ratio of theinstalled power and not the delivered power as
used in figure 7). The first graph showed thecosts for the RoPax vessel operating at a long
route and spends 6500 hours at sea annually,
while the other graph shows the same values fora short route version that spends only 2500hours at sea. It can be seen that the optimumpower split between the pod and the mechanicalpropeller has changed a lot and is below 25/75for the short route vessel. In this case the capital
costs contributes to a much larger part of thetotal costs than for the long route vessel, where
the fuel consumption is the largest cost item.
CRP COST EFFICIENCY FOR THE FAST ROPAXAT DIFFERENT POD POWER RATIOS
SHORT ROUTE
0 %
20 %
40 %
60 %
80 %
100 %
120 %
20 25 30 35 40 45 50 55 60
POWER RATIO: [%]
POD POWER / TOTAL INSTALLED PROPULSION POWER
ANNUALCOST[%
]
Total annual cost (incl.operating and capitalcosts)
Annual operating cost(incl. fuel, lube oil, andmaintenance costs)
Annual capital cost
FIGURE 9. Cost efficiency at different pod power ratios for the RoPax operating the short route.
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Oskar Levander Advanced machinery with CRP propulsion for fast RoPax vesselsWrtsil Corporation / Marine Division The Motorship Marine Propulsion Conference 2002
The conclusion is that the total economy needs
to be assessed when selecting the propulsion set-up for a vessel with a podded CRP in order to
reach the best result. Also the operating profilehas a big influence on the correct propulsion
configuration. The exact values, for the optimumlocation of the power splits as indicated in thefigures 7-8, can not be relied upon, since there
are no reliable figures for the affect that thepower ratio has on the hydrodynamic efficiency.However, the graphs do show the principal onhow to optimise the propulsion set-up and thetrend of the different input values. Wrtsil willconduct more tests in order to get more reliabledata.
Technical issues regarding the
implementation of the podded CRP concept
There are still many issues that have to beinvestigated before a podded CRP can beintroduced in full size applications. There arealways considerable risks involved with the
implementation of new technology, especiallywhen it might have a large impact on the total
performance of the complete product. This iscertainly the case for a CRP concept. Someissues that might poses problems or need to befurther investigated are:
n Cavitation performance of the aft propellerwhen steering
n Vibration excitation forces
n Structural strength in extreme situationsn Behaviour in extreme situation, such as
crash stopsn Operation with one of the propellers stoppedn Operation philosophy
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Oskar Levander Advanced machinery with CRP propulsion for fast RoPax vesselsWrtsil Corporation / Marine Division The Motorship Marine Propulsion Conference 2002
CODED MACHINERY
CONFIGURATIONS
Two alternative Combined Diesel-Electric andDiesel-Mechanical machinery concepts weredeveloped for the fast RoPax vessels. Bothmachinery solutions feature a diesel mechanicalpart driving a feathering CP propeller and adiesel electric power plant powering both theelectric CRP pod and the entire hotel load. The
first concept is aimed to give the vessel a servicespeed of 30 knots while the other will be able to
power the ship with a speed of 28 knots.
Machinery concept 30 knot CODED version
The total delivered power demand under serviceconditions is about 47 MW. The installed powersplit should be around 40/60 between the pod
and the mechanical propeller according to theresults from the previous chapter. This mean thatthe optimum installed mechanical power isabout 34 MW when transmission losses and an85% engine margin is applied. The only enginemodels that are large enough to supply thispower through a twin in / single out gear are theWrtsil 46 and 64 engine series. However, the
Wrtsil 64 engine is too large to fit under the
car deck and still allow sufficient space formaintenance work. The Wrtsil 46 engine istherefore the only feasible option for this ship.
The best option for this case is therefore two
16V46C engines. Their combined power of 33,6MW is very close to the optimum power of 34
MW or 60 % of the total propulsion power. Thedelivered power at the mechanically driven
propeller is about 28 MW in service conditionswhen transmissions losses of 2,5% and a servicerating of 85% MCR are taken into account.
The power demand for the electrical pod is then19 MW to be able to coupe with the totaldelivered power demand of 47 MW. One shouldalso consider that the pod power fits well withthe steps in the pod sizes available. If the powerdemand is just under a certain step and the nextlarger pod model is much larger, it might be
interesting to consider the smaller pod size and
larger diesel engines to drive the mechanicalpropeller instead. The larger pod size increasesinstallation work and might impact on the cargocapacity and handling negatively in a Ro-Roship, if the auxiliary machinery for the pod isintruding on the car deck. The total cost curve in
figure 8 is very flat to the left of the optimumpower ratio, so a smaller pod should not have
any negative impact on the total feasibility.However, in this case the load is already veryhigh on the mechanically driven propeller, so itis not motivated to deviate from the optimumpod size in figure 8. The selected pod hastherefore a nominal power of 19 MW.
INSTALLED POWER :
Mechanical power 33600 kW
Electrical power 27900 kW
Total installed power 61500 kW
LIPS bow thr usters:
2 x 1300 kW
Hotel
consumers:
1,5 - 2,5 MW
W6L32 2700 kW
W12V46C 12600 kW
W16V46C 16800 kW
W16V46C 16800 kW
W12V46C 12600 kW
DELIVERED POWER :
Engine load Nominal Service
Electric pod 19.000 kW 17.000 kW
35 % 38 %
LIPS CP propeller 33.600 kW 27.700 kW
65 % 62 %
Total shaft power 51.600 kW 44.700 kW
FIGURE 10. CODED machinery configuration for the 30 knot RoPax
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Oskar Levander Advanced machinery with CRP propulsion for fast RoPax vesselsWrtsil Corporation / Marine Division The Motorship Marine Propulsion Conference 2002
The pod propulsion power of 19 MW gives an
electrical load of 20 MW when the converter,transformer and electrical motor efficiencies are
taken into account. The total electrical load isabout 22 MW when the hotel load of about 2
MW is added. The total installed break power ofthe genset engines should then be about 26,5MW to allow for a service rating of 85% MCR
and generator efficiency of 97%.
The gensets are configured into a power planttype machinery where the same gensets suppliesboth the electric propulsion and the hotel load.The combinations of available genset options arenumerous and there are many suitable solutions.The large power demand makes it feasible to opt
for an engine type with a large power output per
cylinder to reduce the total number of cylinders.Therefore the Wrtsil 38 and 46 series are themost suitable engine types. Since the 46 engineis used for the mechanical propulsion, it isbeneficial to use the same type for the electricalpower plant. However, the power demand in
port can be under 2 MW, so there should also be
at least one unit with a power output in the
region between 2,5 4 MW to avoid too lowloads on the engines. Even though it is possible
to run an engine at low loads under 20%,continuous operation at low loads is not
recommended. The smallest engine in both the46 and 38 series have a power output of over 4MW, so there is no suitable model to create the
electricity in port. Therefore, another type ofengine must also be brought onboard.
In this case, the selected configuration consist oftwo 12V46 engine and one 6L32 engines, withpower outputs of 12600 kW and 2700 kWrespectively. This gives a total electrical powergeneration capacity of 27,9 MW. The large
diesel generators with low fuel consumption
supply most of the electrical power. The small6L32 genset is mostly used in port when theonly electrical load consists of the hotel load.However, it can also be used for extra power atfull speed or to reduce the load jump betweenthe large engines at part load.
FIGURE 11. CODED machinery for the 30 knot ship
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Oskar Levander Advanced machinery with CRP propulsion for fast RoPax vesselsWrtsil Corporation / Marine Division The Motorship Marine Propulsion Conference 2002
Machinery concept 28 knot CODED version
The machinery for the 28 knot machinery isselected according to the same principal. In thiscase the optimum power split between the
propulsors has moved so that more powershould be mechanical and less electrical, sincethis machinery is intended mostly for short route
operation. In this case the capital cost has moreimpact on the total costs as indicated in figure 9.
The mechanical propulsion is powered by two16V46C engines, the same as for the 30 knotversion. The pod size is on the other handreduced to 14 MW to reflect the lower deliveredpropulsion power demand of 40-41 MW. The
power split between the installed mechanical
propeller and the pod power is therefore about30/70.
The electrical generation capacity is matched tothe lower power demand and two 8L46 plus one6L32 genset are selected, with a combined
power of 19500 kW.
Redundancy
The main engines driving the mechanicalpropeller are located in the aft engine roomcompartment while the gensets are located in thetwo compartments forward of that. A watertight
A-60 class bulkhead separates the engine
compartments from each other. This preventsfires and flooding to spread from one engine
room to the other. This gives a certain degree ofsafety and redundancy. The engine room is not
fully redundant though, since all the electricalgeneration equipment is in the samecompartment and also some of auxiliary systems
are not divided into separate compartments.However, the ship should not lose the entirepropulsion power even if any one of thecompartments is knocked out.
The main engines can be configured to run evenunder a full black out and drive the mechanicalpropeller. The emergency generator will provide
the power needed for the essential equipment to
get back to port. The pod is used as a rudder inthis case without any driving force. It might beworth to consider increasing the lateral area ofthe pod to enhance its ability to create side forcewhen acting as a rudder.
On the other hand, if the main engines aredamage and the gensets are intact, the situation
is not as bad. Then the ship can power itself withjust the pod back to port. In this case, thepassengers would not notice much else than areduction in speed, since the entire hotel powerdemand can easily be covered.
INSTALLED ENGINE POWER :
Mechanical power 33.600 kW
Electrical power 19.500 kW
Total installed power 53.100 kW
DELIVERED PROPULSION POWER :
Engine load Nominal Service
Electric pod 14.000 kW 13.300 kW
29 % 34 %
LIPS CPP 33.600 kW 27.700 kW
71 % 66 %
Total shaft power 47.600 kW 41.000 kW
W 6L32 2700 kW
W 16V46C 16800 kW
W 16V46C 16800 kW
W 8L46C 8400 kW
W 8L46C 8400 kW
FIGURE 12. CODED machinery configuration for the 28 knot RoPax
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Oskar Levander Advanced machinery with CRP propulsion for fast RoPax vesselsWrtsil Corporation / Marine Division The Motorship Marine Propulsion Conference 2002
DF-ELECTRIC MACHINERY
CONCEPT
The third machinery alternative developed in theSeaTech 2000+ project is also based on the CRPconcept. However, this machinery consists ofWrtsils Dual Fuel engines, which run onnatural gas and MDO instead of the typicalHFO. The machinery is of the totally electricpower plant type and both propellers are
powered with electrical motors. This shipconcept is also aimed at a service speed of 28
knots.
Machinery concept 28 knot DF electric
version
The propulsion power demand is about 40 MWin service conditions. The optimum power split
between the propulsors is different than for theCODED version since both propellers areelectrically driven. However, there is still adifference in capital cost between a pod and anelectrically powered conventional propeller. Alarge pod size also increases the space demandabove the pod, which impacts on the car deckspace and can complicate the installation. The
pod power is therefore selected to be 17 MW,
which is larger than for the CODED. However,most part of the propulsion power, 24 MW, isstill on the conventional propeller.
The power plant is configured to meet the totalpower demand from the propulsion and hotel
load. It has four 12V50DF and two 9L32DF
gensets giving a total installed engine power of51,9 MW. The gensets are divided into twoseparate engine rooms to provided redundancy.
Machinery arrangement
The machinery is designed according to an
Emergency Shutdown (ESD) philosophy. Theconfigurations consist of the following features:n Automatic switch to MDO use or shutdown
of one of the engine rooms in case of a gasleak.
n Gas detectors in engine roomsn Engines located in two separated engine
rooms
n Redundant power generation
n Low gas pressure (under 10 bar)n Single wall gas piping within the engine
roomn The gas pipes are enclosed in ducts outside
the engine room
The natural gas is stored in liquid form (LNG) inspecial vacuum insulated tanks. The LNG tank
space features some special arrangements tocomply with the only suitable classification rulesto date (DNV 2001):n Thermally isolated from the hulln Venting to safe locationn Located inside B/5n Buffer zone to A class machinery spaces
INSTALLED ENGINE POWER :
Mechanical power 0 kW
Electrical power 51.900 kW
Total installed power 51.900 kW
W 9L32DF 3150 kW
W 12V50DF 11400 kWW 12V50DF 11400 kW
W 9L32DF 3150 kW
W 12V50DF 11400 kWW 12V50DF 11400 kW
DELIVERED PROPULSION POWER :
Engine load Nominal Service
Electric pod 17.000 kW 17.000 kW
40 % 41 %
LIPS CPP 25.000 kW 24.000 kW
60 % 59 %
Total shaft power 42.000 kW 41.000 kW
FIGURE 13. DF-electric machinery configuration for the 28 knot RoPax
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POWER IN FERRIES -
STATISTICS
The installed propulsion power in existingferries and RoPax vessels are indicated in figure14. The ships are divided into different groupsaccording to their service speed. The power ofboth the 30 and 28 knot version is clearly belowthe power of the average vessels in their groups.However the difference is not that clear, since
most ships in the graph are pure dieselmechanical installations with a certain engine
margin applied to the engines. The situation isnot the same for a ship with electricalpropulsion. There is normally no service ratingon electrical propulsion motors, since they can
operate at maximum power with very little, ifany, side effects. The installed propulsion powerof a CODED or diesel-electric ship is therefore
lower than for a similar conventional ship withthe same resistance.
PROPULSION POWER IN FERRIES
0
10 000
20 000
30 000
40 000
50 000
60 000
70 000
80 000
0 10 000 20 000 30 000 40 000 50 000 60 000 70 000
GROSS TONNAGE [GT]
PO
WER[kW]
30 kn CRP Ro Pax
28 kn CRP Ro Pax
>33
knots
28-33
knots
24-27kn
ots
20-23knots
33
knots 28
-33kn
ots
24-27kn
ots
20-23knots
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Oskar Levander Advanced machinery with CRP propulsion for fast RoPax vesselsWrtsil Corporation / Marine Division The Motorship Marine Propulsion Conference 2002
BENCHMARKING
The presented CODED and DF-electricmachinery concepts with CRP propulsion arecompared with conventional RoPax machinery
concepts to quantify the benefits and drawbacksof the new solutions.
The 28 knot machinery versions operating the
long route between Hanko and Rostock will beused for the comparison. Both a CODED
machinery operating on HFO and one operatingon MDO will be used to determine the influencethat a better quality fuel option will have. Thereference will be a typical mechanical RoPaxmachinery with four Wrtsil 12V46 propulsionengines and three 6L26 gensets. A fully dieselelectric alternative with two pods will also beincluded to broaden the comparison. Thealternative machinery options are indicated infigure 18.
Fuel consumption
The energy consumption and the related fuelcost are indicated in figure 17. The CRP vessels
offer the lowest energy consumption due to thelower propulsion power demand. However, the
higher price of MDO results in the highest fuelcost despite the lowest consumption for the
CODED (MDO) version. The DF-ship has
higher fuel costs than the HFO ships but lowercosts than the environmentally friendly MDO
version. However, the price of the LNG mightvary greatly from one place to another. There is
no existing infrastructure to bunker ships withLNG and therefore no existing marine LNGprices when delivered to the ship. The estimated
LNG cost can therefore change considerably forother applications.
Machinery related costs
The total machinery related costs are indicatedin figure 19. The CODED (HFO) machinery hasthe lowest operating costs and only slightly
higher capital costs than the diesel-mechanical
version. The diesel-electric and the DF-electricalternatives have significantly higher capitalcosts than the other alternatives due to theexpensive electrical propulsion systems. TheCODED (HFO) alternative offers the lowesttotal machinery related costs. The DF-electric
alternative has a higher total cost than the shipsoperating on HFO, but it is lower than that of the
ship running on MDO when the SCR relatedcosts are taken into account. This should beincluded to make the environmental impact ofthese vessels somewhat more comparable.
M=B
OM=B
QM=B
SM=B
UM=B
NMM=B
NOM=B
NQM=B
NSM=B
aJj~~
J
ecl
aJb
mla
ecl
`laba
`om
ecl
`laba
`om
jal
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crbi=`lpq
Assumed fuel prices:
HFO 120 USD/ton
MDO 200 USD/ton
MGO 220 USD/ton
LNG 170 USD/ton
FIGURE 17. Energy consumption and fuel costs for the alternative machinery concepts.
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April 10-11th, 2002
Oskar Levander Advanced machinery with CRP propulsion for fast RoPax vesselsWrtsil Corporation / Marine Division The Motorship Marine Propulsion Conference 2002
Diesel-mechanical (HFO)
n Installed power: 55980 kW
W 12V46 12 600 kW
W 12V46 12 600 kW
W 12V46 12 600 kW
W 12V46 12 600 kW
W 6L26 1860kW
W 6L26 1860
kW
W 6L26 1860
kW
Diesel-electric (HFO)n Installed power: 53100 kW
W 12V46C 12600 kWW 12V46C 12600 kW
W 12V46C 12600 kWW 12V46C 12600 kW
W 6L32 2700 kW
CODED (HFO)CODED (MDO)
n Installed power: 53100 kW
W 6L32 2700 kW
W 16V46C 16800 kW
W 16V46C 16800 kW
W 8L46C 8400 kW
W 8L46C 8400 kW
DF-electric (LNG/MDO)
n Installed power: 51900 kW
W 9L32DF 3150 kW
W 12V50DF 11400 kWW 12V50DF 11400 kW
W 9L32DF 3150 kW
W 12V50DF 11400 kWW 12V50DF 11400 kW
FIGURE 18. Machinery alternatives for a 28 knot RoPax vessel
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Oskar Levander Advanced machinery with CRP propulsion for fast RoPax vesselsWrtsil Corporation / Marine Division The Motorship Marine Propulsion Conference 2002
0
2 000
4 000
6 000
8 000
10 000
12 000
14 000
16 000
18 000
D-Mechanicaltwin-screw
HFO
D-ElectricPOD
HFO
CODEDCRP
HFO
CODEDCRP
MDO
DF-ElectricCRP
LNG
Annualcosts[kUSD]
SCR costs
Annual capitalcosts
Maintenancecosts
Lub oil costs
Fuel oil costs
FIGURE 19. Total annual machinery related costs. The capital costs are based on 8% interest
rates and a 10-year repayment time.
Emissions
The primary exhaust emission levels for theentire machinery including both engines and oilfired boilers (OFB) are compared against the
conventional machinery alternative in figure 20.It can be seen that the DF-electric machinery
using LNG as fuel offers by far the lowestemission levels. The second best result isachieved with CODED machinery equippedwith a SCR unit and using MDO as fuel. Thegreat benefit of the LNG version is the clear
reduction in CO2 emissions, which can not bereached with conventional fossil fuels.
0 %
20 %
40 %
60 %
80 %
100 %
120 %
D-Mechanical
HFO
D-Electric
HFO
SCR
CODED
HFO
SCR
CODED
MDO
SCR
DF-Electric
LNG-MDO
CO2 NOx SOx
FIGURE 20. Relative annual exhaust emissions for the entire machinery (engines + OFB).
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Oskar Levander Advanced machinery with CRP propulsion for fast RoPax vessels
SUMMARY
The new CODED machinery with a CRP podoffers most of the benefits associated either withdiesel electric or diesel mechanical machinery
without their respective downsides. The result isa very competitive solution that providesoutstanding technical and economicalperformance for fast RoPax and RoRo
applications. This machinery solution also showsgreat potential for other twin screw vessels,
single screw ships with highly loaded propellersor ships with high manoeuvring demands.
The new Wrtsil Dual Fuel engines operating onLNG is an interesting future option that can offera very environmentally friendly alternative.
REFERENCES
1. Backlund A. and Kuuskoski J., The ContraRotating Propeller (CRP) Concept with aPodded Drive Motor Ship Conference,Amsterdam, The Netherlands, March 28-292000
2. Bernardes-Silva P. Natural gas fuelled fastcraft - challenges and development, FAST2001 conference, Southamption UK,September 4-6th, 2001
3. Common Questions about LNGs Use as aTransportation Fuel, LNG Express AnnualDirectory; 1993-1994
4. DNV - Rules for Classification of Ships Newbuildings - Part 6 Chapter 13 - GasFuelled Engine Installations, January 2001
5. EMPRO - Summary Report - Task 3.1.2 -Propulsion Drive for a New RoPax Concept,Kvaerner Masa-Yards Technology, Turku
Finland; June 2001
6. ESMA - Activity NO. 3.2 Alternative fuelsfor marine applications, Marintek Sintef
Group, March 1999
7. Jokela R., Determining the most efficientpropulsion system, Ship Propulsion Systems2001 2nd annual international multi-streamed conference - Lloyds List Events,Hamburg Germany, October 2001
8. Laurilehto M., Gas fuelled engines for
marine applications, Marine News, WrtsilCustomer Magazine nr 1 - 2001
9. Levander K., Improving the RoPaxConcept With High Tech Solutions,EuroConference on Passenger Ship Design,
Operation & Safety, Crete Greece, October2001
10.Levander O., Combined Diesel-Electricand Diesel Mechanical Propulsion for aRoPax Vessel, Marine News - WrtsilCustomer Magazine nr3 2001, December2001
11.Levander O., LNG as bunkered fuel,EMPRO seminar, Helsinki Finland,December 2001
12.Levander O., New Machinery Solutionsfor Fast RoPax vessels, SeaTech 2000+seminar, Raumo Finland, March 2002
13.Praefke E., Richards J. and EngelskirchenJ., Counter rotating propellers withoutcomplex shafting for a fast monohullferry, Presentation at FAST 2001,Southampton UK, September 2001
14.Shuto H. and Dr Yoshida Y. Contra-rotating propellers: taking the concept tojumbo containerships, Ship PropulsionSystems 2001 2
ndannual international
multi-streamed conference - Lloyds List
Events, Hamburg Germany, October 200115.Sipil H., Machinery Development for
RoPax vessels, EMPRO seminar, HelsinkiFinland, December 2001
16.Veikonheimo T., CRP Azipod propulsionsystems EMPRO seminar, HelsinkiFinland; December 2001
17.Wrtsil 46 Project Guide for MarineApplications, Wrtsil Finland Oy, Vaasa,Finland, January 2001
18.Wrtsil 32 Project Guide for MarineApplications, Wrtsil Finland Oy, Vaasa,Finland, August 1998