hydrodynamic aspects of steerable...

© Wärtsilä

Jie Dang & Hans LaheijWärtsilä Propulsion Netherlands BV (WPNL), 30-09-2004

Dynamic Positioning Conference, Houston, USA

Hydrodynamic Aspects of Steerable Thrusters

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Contents

Introduction J. Dang

Thruster configurations J. Dang

Propulsion Efficiency J. DangBollard pull efficiencyFree sailing efficiencyPulling or pushing arrangement?

Matching with the engine / E-motor J. Dang

Interactions H. LaheijThruster water jetThruster-thruster interactionsThruster-hull interactions

LIPS® HR high efficiency nozzle H. Laheij

Applications for DP / DT vessels H. Laheij

Conclusions H. Laheij

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Introduction

DevelopmentsNew ideas, new concepts, new products - everydayDiesel-electrical drive and large AC E-motors - stimulatingConsequence:

More possibilities -positiveMore suitable system for certain operation -positiveMore confusing -negative

GuidelinesReview of the development -van Terwisga

(2001)General guideline -Deter (1997)

Restricting our discussion in:Azimuth thrusters with propellersFP, CP, Ducted, Counter-rotating PropellersNot including – water jet, pump jet, Voith SchneiderNot including – Cavitation, noise, maneuvering, etc.

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Thruster configurations (1)

LIPS® Z-drive thruster with an open CP propeller

LIPS® L-drive thruster with a FP propeller in LIPS® HR nozzle

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Thruster configurations (2)

LIPS® Z-drive thruster with open propeller (CPP) and pulling arrangement

Thruster with Z-drive and CRP installation

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Propulsion efficiency (1)

Open water characteristics

0

0.2

0.4

0.6

0.8

1

1.2

0 0.2 0.4 0.6 0.8 1 1.2

J=V/nD

Kt,

10K

q, E

ta0

Kt10KqEta0

0

0.2

0.4

0.6

0.8

1

1.2

0 0.2 0.4 0.6 0.8 1 1.2

J=V/nD

Kt,

10K

q, E

ta0

Kt10KqEta0

a typical open propeller typical counter-rotating propellers

0

0.2

0.4

0.6

0.8

1

1.2

0 0.2 0.4 0.6 0.8 1J=V/nD

Kt, 1

0Kq,

Eta

0

Kt10KqEta0Ktn

0

0.2

0.4

0.6

0.8

1

1.2

0 0.2 0.4 0.6 0.8 1J=V/nD

Kt, 1

0Kq,

Eta

0

Kt10KqEta0Ktn

a typical nozzle propeller in 19A nozzle a typical nozzle propeller in LIPS® HR high efficiency nozzle

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Slope of curves

and

Counter-rotating propellers

and

Ducted propeller

TT

dKsdJ

=(10 )Q

Q

d Ks

dJ=

T TCRP OPs s> Q QCRP OPs s>

_ 00Qnozzle propeller J

s==

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Bollard pull efficiency

Merit coefficient32( / )T

dQ

KKπη =

0.5

0.7

0.9

1.1

1.3

1.5

1.7

1.9

0.5 0.7 0.9 1.1 1.3 1.5propeller pitch ratio (front propeller for CRP) P/D

Mer

it co

effic

ient

ηd

B4-70Wageningen CRP series Ka4-70 in 19A nozzleKa4-70 in HR nozzle

Comparison of bollard pull efficiency among different type of propulsors

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Bollard pull efficiencyDucted propeller (major influences):

Blade contourPitch distributionTrailing edge

0.5

0.7

0.9

1.1

1.3

1.5

1.7

1.9

0.5 0.7 0.9 1.1 1.3 1.5propeller pitch ratio P/D

Mer

it co

effic

ient

ηd

Ka4-70 in 19A nozzle

B4-70 in 19A nozzle0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0.9 1.0 1.1 1.2 1.3Ptip / P0.7R

Mer

it co

effic

ient

ηd

Influence of tip loading on pull efficiency (propellers with Kaplan form blades in No. 19 nozzle, based on the model test results of van Manen, 1962)

Influence of tip chord length on pull efficiency

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0

10

20

30

40

50

60

70

0% 50% 100% 150%engine power [%]

pull

thru

st [t

ons]

blades with normal anti-sing edgeon suction side

blades with large ''anti-sing edge'' onpressure side

0%

20%

40%

60%

80%

100%

120%

50% 60% 70% 80% 90% 100% 110%engine shaft speed [%]

engi

ne p

ower

[%]

blades with normal anti-singedge on suction side

blades with large ''anti-singedge'' on pressure side

Engine output limit

Full-scale measurements of pull thrust vs. shaft power for a tug boat – Thetis, Iskes Sleepdiensten BV, IJmuiden, the Netherlands

Full scale measured power-shaft speed relation for the same propeller with different ‘anti-sing edges’

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Free sailing efficiency

0 2T

Q

JKK

ηπ

=

Comparison of the open water efficiency of different propulsors (where P/D is either the pitch ratio of the propeller or the pitch ratio of the front propeller for counter-rotating propellers)

0.81.0 1.0

1.2

1.0

1.2

1.1

1.3

0.4

0.5

0.6

0.7

0.8

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0Thrust load coefficient Ct

Ope

n w

ater

effi

cien

cy η0

Open Propeller B4-70Wageningen CRP series

Ka4-70 in 19A nozzleKa4-70 in high efficient nozzle

P/D=

2

8 tt

KCJπ

=

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Pulling or pushing arrangement?

Efficiency of pulling arrangementTwo factors

1. Friction losses – underwater housing in the slipstream of the propeller wake

2. Rotational energy recovery – due to the down stream strut and fins

For propeller with light loadRotational energy recovery > Friction losses

pulling is betterfast vessel

For propeller with heavy loadFriction losses > Rotational energy recovery

pushing is betterlow speed vessel

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Based on systematic research at SVA Potsdam Grey area Ct=0.5 to 1.0

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Wake field differences

A typical wake field at propeller disc for the pulling arrangement of a twin-screw vessel

A typical wake field at propeller disc for the pushing arrangement with one strut for a twin-screw vessel

Pulling or pushing arrangement?

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Matching with the engine/E-motor (1)

Fixed pitch propeller or controllable pitch propeller

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

110%

120%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 110% 120%

shaft speed N [%]

pow

er P

B [%

]

FSAH FPP OPENFSAH FPP HRFSAH CRPBAH FPP OPENBAH FPP HRBAH CRP

MCR

Design PointMax

. BA

H th

rust

(311

kN) a

t Max

. tor

que

Max

. BA

H th

rust

(366

kN) a

t Max

. tor

que

Max

. BA

H th

rust

(515

kN) a

t Max

. tor

que

Comparison of three different propulsion concepts for an offshore supply vessel with diesel-electric drive propulsion systems (two azimuth thrusters per ship at the stern), here FSAH - free sailing ahead, BAH – bollard ahead

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Matching with the engine/E-motor (2)

A typical semi-submersible

The typical propeller curves for a semi-submersible with two pontoons and four azimuth thrusters with FPP in LIPS® HR nozzle, two thrusters at the bow and two at the stern

0%

20%

40%

60%

80%

100%

120%

140%

160%

50% 60% 70% 80% 90% 100% 110% 120%

N[%]

PB[%

]

Trial-(bow)ThusterTrial-(stern)ThusterService-(bow)ThrusterService-(stern)ThrusterBollard Vs=0knBollard Vs=-2kn

MCR

Qmax

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Thruster-thruster, thruster-hull interactionsunderstanding the jet (1)

water jet of the thruster - the shape

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Thruster-thruster, thruster-hull interactions understanding the jet (2)

Shape of jet of water behind a working thruster at zero speed (bollard condition)

Line of maximum speed

Line of zero speed

D

water jet of the thruster - the position of the maximum speed

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Maximum jet speeds for thruster in bollard pull condition

water jet of the thruster - the maximum speed

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Position of maximum speed goes to shaft center line at x/D = 4 (was 6 without plate)

Flat plate at 0.75D below thruster center line

Position of maximum speed does not stay on center line, but moves towards the plate

Maximum speed for water jet close to a flat plate

Magnitude of maximum speed does not change compared to open water situation !

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Thruster-thruster, thruster-hull interactionsthruster-thruster interaction (1)

3 major different interactions in discussion

x D

x D

x

D φ

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Thrusters in tandem in free open waterFormula to calculate thrust ratio

x D

23( / )

0/ 1 0.8 x DT T = −

0%

20%

40%

60%

80%

100%

0 5 10 15 20 25 30Propeller distance ratio x/D

Thru

st ra

tio [%

] .

Lehn(1980)

Moberg(1983)

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23( / )

0/ 1 0.75 x DT T = −

Thrusters in tandem under a flat bottomFormula to calculate thrust ratio

x D

0%

20%

40%

60%

80%

100%


Thru

st ra

tio [%

] .

Nienhuis(1992)

Blaurock (1977)

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x

D φ

3

3 3(1 )130 /

t t ttφφ

φ= + −

+

Steering angle on the thrusters can reduce the thrustlossLarger angles reducethrustlossFormula to calculate the thrustratio

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 5 10 15 20 25 30 35

steering angle of the forward thruster [degrees]

Thru

st ra

tio [%

]

.

Nienhuis (1992) x/D=2.0Nienhuis (1992) x/D=4.0Nienhuis (1992) x/D=8.0Nienhuis (1992) x/D=16.0Lehn (1980) x/D=3.0Lehn (1980) x/D=6.0

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Interaction applicable toboth bollard and free sailingconditionImportant since DP thrusters are used for mainpropulsion as well

0%

20%

40%

60%

80%

100%


Tota

l thr

ust r

atio

of t

wo

thru

ster

s [%

] .

Blaurock (1977) J=0.00



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Thruster-thruster, thruster-hull interactionsThruster-hull interaction (1)

Water jet close to a flat plateReductions can be as high as 20-25%, Thrusters in the bow are inefficient in the sailing direction

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Thruster-thruster, thruster-hull interactionsThruster-hull interaction (2)

water jet along curved surface

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Thruster-thruster, thruster-hull interactionsthruster-hull interaction (3)

Coanda effect

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Thruster-thruster, thruster-hull interactionsThruster-hull interactions (4)

Thrust deduction depending on stern heeling angleFor astern thrust in practice two times larger than ahead

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

0.11

0.12

10 12 14 16 18 20 22 24

stern heeling angle [degrees]

thru

st d

educ

tion

t

Slope

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Thruster-thruster, thruster-hull interactionsthruster-hull interaction (5)

0%10%

20%

30%

40%

50%

60%

70%

80%

90%

100%0

15

30

45

60

75

90

105

120

135

150

165180

195

210

225

240

255

270

285

300

315

330

345

Typical results of Thruster-hull interaction test

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LIPS® HR Nozzleintroduction - different nozzles (1)

Working principle of nozzle propellers

Flow induced pressure difference creates positive thrust

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Different nozzles

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Bollard condition (BAH)

Free sailing (FSAH)


Different flow patterns at BAH and FSAH

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LIPS® HR Nozzlebackground of HR nozzle

Designed to improve the flowaround the nozzleDesigned to improve efficiency at high speedSeries tests done at GermanSVA Potsdam instituteImproved performance; 8 to10% better than 19A

Flow visualisation in cavitation tunnel

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Calculated flow pattern around HR nozzlerounded leading and trailing edgelarger induced velocitymore nozzle thrust and less resistance

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100% 103% 100%108%

0%

20%

40%

60%

80%

100%

120%

Model scale Full scale

Bollard condition19A HR


Comparison - calculated bollard pull thrust

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With:CPP’sFPP’s (4 and 5 bladed)Steerable thrusters

Up to 3.75 [m]Up to 5500 kW

Ranging from 0 to 18+ knotsDmax. = 5.2 [m] with 12640 kW

Many HR-nozzles already sailing !

LIPS® HR Nozzlefull scale experience

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Application of Thrusters

The largest pipe layer -Solitaire

Vessel specLength 300 [m]Transit speed 13 [kn]Accommodation 420 [men]

Thrusters8 LIPS® azimuth thrusterspartly bollard pull and partly free sailing designpartly HR and partly special nozzle5.55MW@199RPMpropeller diameter 3.75m

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Heavy-lifting vessel - Thialf

Vessel specLength 201 [m]Breadth 88.4 [m]Accommodation 736 [men]

Thrusters6 LIPS® azimuth retractable thrustersbollard pull design (85 tons/unit)19A nozzle5.5MW@199RPMpropeller diameter 3.4m

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Maintenance Service Support Accommodation Unit

vessel specLength ~94 [m]Breadth ~45 [m]

thrusters4 LIPS® azimuth thrustersbollard pull design (50 tons/unit)LIPS® HR nozzle2.5MW @ 203RPMpropeller diameter 3.2mOverspeed of driving motor for free sailing

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Largest Semi Submersible Heavy Lift Vessel

Blue Marlin2 x Retractable thrusters with HR NozzlePropeller diameter 3.4 m2 x 4500 kWMain propulsion upgraded with HR NozzlePropeller diameter 5.2 m1 x 12640 kWResulting in more than 30% increase in bollard thrustCarrying largest offshore structures in the world

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Cable ShipCS Atlantic GuardianP=2 X 2200 kWPropellerdiameter 2.5 mElectric drive CPP thrusterL-drive configurationAble to absorb full power at all conditions

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Cable LayerCS- KnightMain propulsion 2 X 4500 kWPropellerdiameter 3.4 mRetractable 2 x 2000 kWPropellerdiameter 2.5 mElectric driven FP propellers

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Anchor Handling Tug Supply VesselSeabulk BadamyarP= 2 X 1440 kWPropellerdiameter 2.1 m7.4% extra bollard pull due to HR NozzleBollard pull is 10% over charter requirements

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ConclusionsHydrodynamic aspects of steerable thrusters

Mission profile determines the choice of the design point; off-design condition and its co-operation with the E-motor (or engine) are important

For low-medium speed applications (e.g. DP/DT) pushing propellers are more efficient than pulling propellers

Interactions among thrusters, hull, barge, etc should not be ignored in thruster design

High efficiency nozzles improve efficiency8% extra bollard pull thrust10% extra free sailing propulsion efficiency

Propulsion Supplier should take all hydrodynamic aspects of thrusters into account to ensure a perfect match

between thrusters and the vessel

© Wärtsilä

Wärtsilä Propulsion Netherlands BV

Jie [email protected]

+31 416 388283

Hans [email protected]

+31 416 388546

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