855
1 INTRODUCTION
International Maritime Organization (IMO) executes
the restriction of Energy Efficiency Design Index
(EEDI) whichlimitsamountofCO2whenfreightof
onetoniscarriedatonemile(MEPC,2009).Moreover,
anefficientshipoperationbasedonEnergyEfficiency
OperationalIndex(EEOI)wasrequestedfromIMOto
the ship
operators (MPEC,2009). In phase 3 that is
finalstageofEEDI,thereductionin30%isrequested
from the current state. To comply with the EEDI
phase 3 requirements, it is assumed that the ship’s
enginepowerbecomessmallerthantheexistingship.
However, shiphandling in rough seas is expected
to
become difficult when the engine power is reduced.
As temporary steps, IMO adopted the tentative
minimum engine power in adverse condition
(MPEC,2013). However, the restriction is gradually
strengthened then it is predicted that the engine
powerisrestrictedsmallerinafuture.
Therefore, this study examines the influence that
the degraded ship’s engine exerts on the safety of
shiphandling in heavy weather based on the
simulation study. The main problem on the
shiphandling at stormy weather is caused by the
reduction of ship speed. When the ship proceeds
towardthewaveandwind,
theresistanceofthehull
isincreased,andthentheshipdecreasesthespeed.To
keep the ship’s speed, the main engine output must
be increased. However, the main engine enters the
stage of torque rich that is the torq ue over zone
caused by the reduction of ship speed. In
this
condition, the main engine output is automatically
reduced preventing the damage of the main engine,
andasaresult,theship’s speedbecomes lower and
lower.Iftheship’sspeeddecreasesgreatlyinadverse
condition,theperformanceofruddermaydeteriorate
and the ship is jeopardized. Then, the master
maneuver
the ship corresponding to various
situations like the strength and direction of
Simulation study on the Influence of EEDI Requirements
to Shiphandling in Heavy Weather
C.Nishizaki,T.Okazaki&H.Yabuki
TokyoUniversityofMarineScienceandTechnology,Tokyo,Japan
Y.Yoshimura
TheUniversityofTokyo,Tokyo,Japan
ABSTRACT:InordertoreducetheCO2emissionfromships,InternationalMaritimeOrganizationexecutesthe
restrictionofEnergyEfficiencyDesignIndex(EEDI)whichlimitsamountofCO2whenfreightofonetonis
carriedatonemile.Althoughtherealizationofhigherefficiencyofmain
enginewithoutreductionofengine
outputisthebestsolution,itmightbeimpossible.TocomplywiththeEEDIrequirements,itisassumedthat
theship’s engine powerbecomes smaller than theexisting shipbymeansofimproving the ship propulsive
efficiency. However, shiphandling in rough seas is expected to
become difficult when the engine power is
reduced. In this paper it is shown that the influence of the degraded main engine exerts on the safety of
shiphandlinginheavyweatherbasedonthesimulationstudy.Intheseexperiments,boththesimulationmodel
thatdecreasedenginepowercorrespondingtoEEDIrequirement
andthatwiththeconventionalenginepower
weretested,andmastersinactiveservicemaneuveredthetestshipsintheroughseas.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 13
Number 4
December 2019
DOI:10.12716/1001.13.04.19
856
disturbances, condition of ship’s speed reduction,
targetcourse,typeofship,ship’ssizeetc.Therefore,
inthisstudy,mastersinactiveserviceareinvited,and
theshipmaneuvering simulatorexperimentsinheavy
weather are performed. The simulator experiments
were set for the comparative study with the
maneuveringperformanceinrough
seasbyusingthe
simulation model that decreased engine power
corresponding to EEDI requirement and that of the
conventional engine power (Yasukawa,2008). As the
result of the simulator experiments, the safe
shiphandling limit of the EEDI compliant ship has
decreasedbyonestagecomparingwithconventional
shipintheBeaufort
scale.
In this paper, section 2 introduces the method of
shiphandling in heavy weather of hearing from the
masters. The experimental method and the
experimental results are shown in section 3 and
section 4 respectively. Finally, a discussion of our
findings and the conclusion drawn from this study
arepresentedin
section5and6,respectively.
2 METHODOFSHIPHANDLINGINHEAVEY
WEATHER
Thissectionindicatesthemethodof shiphandlingin
heavy weather. The method is different in each of
ship’s type. Therefore, the standard method and the
typical method for bulk carrier and pure car carrier
(PCC)are shown. The
followingsare the summaries
oftheinterviewresultstomasters.
2.1 StandardShiphandlingMethodinHeavyWeather
Duringtheheavyweather,asadangerphenomenon
tobenoticedonshiphandlingwhentheshipproceeds
againstthewave,propellerracing,torquerichofthe
mainengine,takinggreenwateroverthebow
(green
water taking), slamming and accompanying
whippingcanbepointedout.Inordertoavoidthese
danger phenomenon, it is known that speed
deceleration and change of course are effective. In
addition, as a shiphandling method when the ship
encountersheavyweatheranditbecomesdifficultto
continue navigation, the
master selects “Heave to”
that reduces the speed of the ship to the extent that
the steering effect is not lost and receives the wind
andwavesfrom22to33degreesfromthebow.
2.2 ShiphandlingMethodforBulkerinHeavyWeather
Inbulker,theoutputofthemainengine
isarelatively
smallcomparedwiththehullsize.Therefore,incalm
weather the bulker sails at about 14 knots at full
loading, and sails at about 15 knots at ballast
condition. When bulker avoids stormy weather in
advance,a speedof12knotsormoreisrequired.The
bulker
attheencounterofroughweatherneedstopay
attentiontoslammingandgreenwatertaking.Then,
bulkersailsbyreceivingthewavefromthedirection
of 30
o
from the bow at a speed of 3 to 5 knots with
loweringthemainengineoutputwithCfueloilasit
is.Inaddition,themastertoldthatbulkerrarelytook
“Heaveto”.
2.3 Ship‐handlingMethodforPCCinHeavyWeather
AlthoughPCChasahigh‐power
mainengine,ithasa
largewindreceivingarea.Therefore,incalmweather
thePCCsailsat18.5to20knots.Then,whenitcomes
totheBeaufortscale6to7,thePCCdecelerates.When
thePCCencountersstormyweatherthemasterpays
attentiontogreenwatertakingthanslamming.
Then
thePCCdeceleratesto6to10knotsavoidingtorque
rich zone of main engine, and sails by receiving the
wavefromthedirectionof40
o
fromthebowwhenthe
shipconditionisfullloaded.Attheballastcondition,
thePCCsailsbyreceivingthewavefromthedirection
of 34
o
from the bow. In addition, when the PCC
deceleratesto4knots,thebowishit bya waveand
thehullliesbetweenwaves.Thisisadangerousstate
where the ship is difficult to control her attitude by
steering.Inthiscase,theshipsailswhilereceivingthe
transverse wave to the hull until the ship’s speed
increasesto8knots.Afterthat,themasterchangesthe
ship’s course to windward and recover the ship’s
attitude.
3 EXPERIMENTS
3.1 Targetships
PCCcarrying3,500units(Fullload)and54,000DWT
Panamax Bulker carrying wood chip (Half load
condition) were
used in this study. Principal
particulars of these ships are shown in Table 1.
“EEDI” included at main engine means the power
correspondingtotheEEDIPhase3inthistable.
These are named (EEDI Power) and estimated
fromthe existing power (Existing Power) improving
the propulsive performances of ship.
Method for
estimatingpower curveandspeedtableoftheEEDI
power ship based on existing power ship are
describedinchapter3.2.1.Additionally,procedureto
realize the torque rich in simulator experiments is
describedinchapter3.2.2.
Table1.Principalparticularsoftargetships
_______________________________________________
PCC Panamaxbulker
_______________________
3,000units 35,000DWT
Fullload Halfload
_______________________________________________
Hull
G.T.51,819 43,000
LOA(m)180.00 209.00
LPP(m)170.00 204.00
B(m)32.2632.2
ForeDraft(m)8.809.50
AftDraft(m)8.809.50
Trim(m)NilNil
Displacement(ton)28,000 49,923
Mainengine
MCO(kW)13,920 9,700
MCO(EEDIkW)10,970 7,275
_______________________________________________
3.2 Estimationofpowercurveandspeedtable
3.2.1 PowercurveofEEDIpowership
Thecalculationmethodofpowercurveandspeed
table of EEDI power ship are described in this
chapter.Theauthorssupposedthattheshipresistance
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innavigationspeedofexistingshipwasreduced20%
by some technological innovation. In general, it is
necessary to redesign principal dimension of
propeller in this case. However, the self‐propulsion
factors remained unchanged for the estimation of
EEDIpowershipinthisstudy.Insuchway,required
engineoutput
(BHP)ofEEDIpowerwasreduced20%
from the existing ship. The propeller efficiency was
also improved by the reduction of propeller loading
that was introduced by the reduction of ship
resistance, which made BHP further reduce.
Furthermore,theimprovementinthefueleconomyof
entire plant was expected by
some technological
innovationinthefuture.Astheresults,powercurve
andspeedtableofEEDIpowershipwascalculatedso
as to be the total CO2 emissions cut by 30% in the
75%MCR speed from existing ships. Although the
maximumpowerandrevolutionsofmainengineare
discontinuously provided in
general, they could be
selectedasdesignedinthisstudy.
PCC’s power curve of existing ship and EEDI
power ship are shown in Figure 1, and Panamax
bulker’spowercurveofexistingshipandthatofEEDI
powershipareshowninFigure2.Ineachfigure,the
left ordinate
indicates BHP and the right ordinate
indicates revolutions of main engine. The abscissa
indicatesshipspeedinthesefigures.Thesolidlineof
browncolorshowspowercurveofexistingship,and
thebrakeline ofbrown color showspower curve of
EEDIpowership.Additionally,thesolidlineofblue
color shows revolutions of existing ship in the
75%MCR speed, and the brake line of blue color
shows revolutions of EEDI power ship in the
75%MCRspeed.
3.2.2 Settingoftorquerichconditions
Ship speed is significantly reduced by the head
wave and wind in heavy weather. In this case,
the
propellertorqueisincreased.Asaresult,torquerich
conditionappears. In this condition, the governor of
main engine is controlled to reduce revolution of
main engine. In order to maintain the safety and
serviceabilityofmainengine,thecontrollingvalueof
governoraresetinadvancebyenginemanufacturers.
However,sincethetypeofmainengine couldnotbe
set in the simulator, the revolution of main engine
waslimitedsoasnottoexceedthetorq ueintheMCR
speedsimply.
Specifically, the each torque was calculated for
variousshipspeedandrevolutioninadvance,andthe
revolution
of main engine was coercively set by the
operator corresponding to the ship speed. When the
revolution was limited by operator, it was soon
informed to the bridge. This torque rich procedure
wasavailablewhenenginetelegraphwassettoover
“Stand by Full”. Red colored lines in Figure 1 and
Figure2indicatemaximumrevolutionofmainengine
usedinsimulatorexperiments.
3.2.3 Settingofweatherconditions
Thewindandwaveinsimulatorexperimentswere
setin theBeaufort scale7 through 11,and the wind
andwaveconditionsareshowninTable2.Thewind
speedwas setas
thefluctuating wind and the wave
was set as the irregular wave. In this Table, wind
speed is average one and wave height is significant
waveheightcorrespondingtotheBeaufortscale.The
wave was defined as combination wave incorporate
wind waves and swell. The wind direction and the
wave direction
were set as same value in the
experiments.
Power Curves PCC (Full Load)
-
3,000
6,000
9,000
12,000
15,000
4 6 8 10121416182022
Vs (knots)
BHP (kW)
0
30
60
90
120
150
N (rpm)
Figure 1. PCC’s power curve of existing ship and EEDI power ship.
Power Curves Handy BC (Half Load)
-
2,000
4,000
6,000
8,000
10,000
4 6 8 1012141618
Vs (knots)
BHP (kW)
0
30
60
90
120
150
N (rpm)
Figure 2. Panamax bulk carrier’s power curve of existing ship and EEDI
power ship.
Table2.Thewindandwaveconditionsinexperiments.
_______________________________________________
BeaufortScaleWind(m/s)Wave(m)
_______________________________________________
7154
8195.5
9227
10269
113011.5
_______________________________________________
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3.3 Scenarioofsimulatorexperiments
The scenario of simulator experiments is developed
onthebasisoftheshiphandlingmethodsinthehead
seasinheavyweatherthataredescribedinchapter2.
The ship is proceeding with slow speed under
receiving the bow seas. In this condition, the ship
course
changesbythewaveforceandshipbeginsto
receive the transverse wave to the hull. As a result,
rolling of ship is increased. In order to avoid the
heavyrolling,itisnecessarytochangeshipcourseto
windward and recover the ship’s attitude
immediately.
Undertheabovecondition,
shipmotionsofEEDI
power ship and existing ship were compared.
Scenarioandprocedureofshiphandlingareshownin
1 The initial speed of ship is 5 knots, and the ship
receivesthetransversewaveandwindfrom
2 Shipcoursechangestothedirectionthattheship
receiveswindand
waveofstarboardbow
whetherthiscoursecanbekeptontheconstantspeed
of3to10knots.
The effect of green water taking and slamming
were not considered in experiments, because it is
difficult to reproduce these phenomena in the
simulator.
Figure3.Scenarioandprocedureofshiphandling.
4 RESULTSOFEXPERIMENTS
4.1 ResultsofPCC
Ship tracks of the simulator experiment result are
showninFigure4and5,andthetimeseriesofship’s
heading and speed are shown in Figure 6 and 7.
Figure4and6indicatetheresultsoftheconventional
engine power ship,
and Figure 5 and 7 indicate the
resultsofthedecreasedenginepowercorresponding
toEEDIrequirements. Inthefigure6and7,theblack
coloredlineshows resultwith Beaufortscale 7(BF7),
theradcoloredlineshowsresultwithBeaufortscale
8(BF8), the green colored line shows result with
Beaufort scale 9(BF9), the blue colored line shows
result with Beaufort scale 10(BF10), and the purple
colored line shows result with Beaufort scale
11(BF11).
Figure4.ShiptracksofPCC(Conventional)
Figure5.ShiptracksofPCC(EEDI)
The conventional engine power ship had enough
speedattheheadingof50°inthecaseofBF7andBF8,
butinthecaseofBF9,theheadingwaschangedto40°
to have enough speed. Also, the ship could have
enough speed such as 10 knots with the heading of
40°inthecaseofBF10.However,inthecaseofBF11,
itwasonly7knotseventheheadingwas40°.Inthat
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state,theshipreceivesthediagonalwaveandtheship
rolls greatly. Therefore, it is difficult to do the
shiphandling assumed by the scenario and to
continuesailingbythesamecourse.
Figure6. Time series of heading and speed of PCC
(convent.)
Figure7.TimeseriesofheadingandspeedofPCC(EEDI)
TheEEDIpowershipcouldkeepenoughspeedat
theheadingof50°onlyinthecaseofBF7.Inthecase
ofBF9,theshipcouldobtainthespeedof11knotsby
changingtheheadingto30°.However,inthecaseof
BF10, the ship’s speed was only 6
knots even the
ship’sheadingwaschanged.
From the results of simulator experiments, the
limitationwheretheshiphandlingthatisassumedby
the scenario could be continued is BF10 for the
conventionalenginepowership,andBF9forthecase
ofcorrespondingtoEEDIrequirements.
4.2 ResultsofBulker
For
bulker,simulatorexperimentswereconductedin
Beaufortscale7through9.Theshiptracksareshown
infigure8and9,andthetimeseriesofship’sheading
andspeedareshowninfigure10and11.Figure8and
10 indicate the results of the conventional engine
powership,and
figure9and11indicatetheresultsof
EEDIpowership.IntheFigure8and9,descriptions
weresameasFigure4and5.
Figure8.Shiptracksofbulkcarrier(conventional)
Figure9.Shiptracksofbulkcarrier(EEDI)
InthecaseofBF7,theconventionalenginepower
shipcouldkeeptheship’sheadingto60°whichwas
targetcourseinthescenariowithspeedof7knots.In
thecaseofBF8,theshipcouldkeepthecourseto60°
however the ship’s speed had been reduced to 1.5
knots. Then the ship’s speed became almost zero,
eveniftheship’sheadingwaschangedto50°inthe
caseofBF9.Thisisthestateof“Heaveto”described
860
in section 2.1. The EEDI powership could keep the
ship’sheadingto60°withenoughship’sspeedtosail
inthecaseofBF7.However,theship’sspeedbecame
almostzero in the case of BF8. That state is “Heave
to”sameasconventionalshipinthecaseBF9.
From
the results of simulator experiment, the
limitation where the shiphandling assumed by the
scenario could be continued is BF8 for the
conventional engine power ship, and the case of
correspondingtoEEDIrequirementisBF7.
Figure10.Timeseriesofheadingandspeedofbulkcarrier
(conventional)
Figure11.Timeseriesofheadingandspeedofbulkcarrier
(EEDI)
5 DISCUSSION
Basedontheexperimentalresults,itcanbesaidthat
inthecase ofa moderate high‐speedship withhigh
power engine output such as PCC, the influence of
reduction of the engine power due to the EEDI
requirementsontheshiphandlingintheheavywave
isrelatively
small. However,thefollowing comment
was obtained from masters who participated in the
experiments.ʺForrecent6,000 unitsPCC, theengine
power is not larger than those of ten years ago, so
whentheshipencountersheavyweatherwecan‐not
steerwithauto‐pilotinearlystageofheavy
weather.
The work load of the crew increases if the shipʹs
course cannot be kept by the auto‐pilot.” Then, it is
predicted that the ship corresponding to EEDI
requirements cannot use auto‐pilot at early stage of
stormy weather than present PCC, and the crewʹs
workloadincreases
greatly.
Ontheotherhand,sincebulkerhassmallermain
engineoutputagainstthehullsize,reducingthemain
engine output by EEDI requirements has a big
influenceon shiphandling. Therefore, it isimportant
tooperatetheEEDIpowershipbymeansofavoiding
heavy weather areas in advance properly
accumulatingtheforecastinformation.
6 CONCLUSION
In this study, the authors conducted comparative
simulator experiments of shiphandling in heavy
weatherwiththeconventionalenginepowershipand
theEEDIpowership,andevaluatedtheinfluenceof
reductionofmainengineoutputontheshiphandling.
In the simulator experiments using PCC, the
safe
shiphandling limit of the EEDI power ship was the
state of Beaufort scale 9 and that of conventional
outputshipwasthestateofBeaufortscale10.Forthe
simulator experiments using bulkier, the limit of
shiphandlingassumedtobethestateofBeaufortscale
8 for conventional engine
power ship and to be the
stateofBeaufortscale7fortheEEDIpowership.
In this simulator experiments, it was carried out
underlimitedconditionssuchasestimationofpower
curve,handlingoftorquerich,handlingofwaves,etc.
as mentioned in Section 3. Also, the simulation did
not
considertheeffectsofslammingandgreenwater
taking.Inthefuture,itmaybedesiredtoper‐formthe
simulatorexperimentwhichmoreaccurate‐lyreflects
theactualsituationofshiphandlingforheavyweather
intheactualseaarea.
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MEPC. Interim guidelines on the method of calculation of
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MEPC.Reduction
ofGHGemissionsfromships,Technical
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