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 methodand 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 ShiphandlingMethodforPCCinHeavyWeather
AlthoughPCChasahighpower
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
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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)32.2632.2
ForeDraft(m)8.809.50
AftDraft(m)8.809.50
Trim(m)NilNil
Displacement(ton)28,000 49,923
Mainengine
MCO(kW)13,920 9,700
MCO(EEDIkW)10,970 7,275
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3.2 Estimationofpowercurveandspeedtable
3.2.1 PowercurveofEEDIpowership
Thecalculationmethodofpowercurveandspeed
table of EEDI power ship are described in this
chapter.Theauthorssupposedthattheshipresistance
857
innavigationspeedofexistingshipwasreduced20%
by some technological innovation. In general, it is
necessary to redesign principal dimension of
propeller in this case. However, the selfpropulsion
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.