advanced machinery with crp propulsion for fast rpax vessels.pdf

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

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


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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


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FIGURE 2. General arrangement of the 30 knot long route RoPax vessel.


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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.


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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


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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.


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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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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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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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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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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 :



29 % 34 %

LIPS CPP 33.600 kW 27.700 kW

71 % 66 %


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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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 :



40 % 41 %

LIPS CPP 25.000 kW 24.000 kW

60 % 59 %


FIGURE 13. DF-electric machinery configuration for the 28 knot RoPax


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April 10-11th, 2002


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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April 10-11th, 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.

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òm

jal

acJb

òm

ikd

bkbodv

`lkprjmqflk

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


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)


W 6L32 2700 kW

W 16V46C 16800 kW

W 16V46C 16800 kW

W 8L46C 8400 kW

W 8L46C 8400 kW

DF-electric (LNG/MDO)


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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April 10-11th, 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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April 10-11th, 2002

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

advanced machinery with crp propulsion for fast rpax vessels.pdf

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