core design issues of large lng carrier

CORE DESIGN ISSUES OF

LARGE LNG CARRIER

Ho-Chung Kim, Duck-Yull LeeDaewoo Shipbuilding & Marine Engineering Co., Ltd.

Seoul, Koreawww.dsme.co.kr

Contents

1. Introduction

2. Hydrodynamic Aspect

3. Strength Aspect

4. Propulsion Systems

5. Concluding Remarks

2

1. Introduction

Capacity of LNG Carriers

� Late 1999s - up to 138,000 m3

� Since the year 2000 - rapid increase in

size up to 250,000 m3 based on

membrane type

3

DSME Large LNG Carriers for New LNG Market

Size 210 K 230 K 250 K

303.0 325.0 333.0

50.0 51.0 55.0

12.0/ 13.6 12.0/ 13.6 12.0/ 13.6

210,000 230,000 250,000

No. of Cargo Tank five (5) five (5) five (5)

Service Speed (kts) 19.5 19.5 19.5

No. of propeller Twin Twin Twin

Propulsion System1) DF electric 2) 2-Stroke diesel3) GT electric

1) DF electric2) 2-Stroke diesel3) GT electric

1) DF electric2) 2-Stroke diesel3) GT electric

LBP (m)

B (m)

Td/ Ts (m)

Cargo Vol. (m3)

1. Introduction

4

Investigated Core Design Issues for Large

LNG Carrier

� Optimum hull form development

- Twin/Single propulsion

� Strength assessment

- Sloshing

- ULS, Buckling

- Fatigue ---

[continue]

1. Introduction

5

� Alternative propulsion systems

- Steam turbine propulsion, conventional

- Electric propulsion, dual fuel engines

- Slow speed diesel engines + reliquefaction

plant

- Electric propulsion, gas turbine

1. Introduction

6

Characteristics & Design Requirements

� Ship/shore compatibility

� Cargo tank arrangement

� Hydrodynamic performances

2. Hydrodynamic Aspect

7

2. Hydrodynamic Aspect

� Hull form generation

� CFD analysis

� Model tests

� Performance evaluation

� Next design spiral for improvement

Hull Form Optimization Technology

8

2. Hydrodynamic Aspect

Forebody Hull Forms

9

InitialDevelopedImproved

2. Hydrodynamic Aspect

Bulbous Bow Shapes

F.P.

Load Waterline

10

InitialDevelopedImproved

Developed

Initial

ImprovedEstimated wave patterns

[Full load condition]

2. Hydrodynamic Aspect

11

Estimated wave profiles

[Full load condition]

2. Hydrodynamic Aspect

Developed

Initial

Developed

Improved

12

Developed

Improved

Observed Waves

2. Hydrodynamic Aspect

13

2. Hydrodynamic Aspect

Aftbody Hull Forms

Single skeg Twin skeg

14

Actual modelCFD

Virtual model

2. Hydrodynamic Aspect

Aftbody Optimization

15

Single skeg Twin skeg

Aftbody Models for Comparative Tests

2. Hydrodynamic Aspect

16

Model Test Results for Speed Performance [twin/single, Full load]

Speed power curves [design draft]

Approx. 9%

Single skeg

Twin skeg

Ship Speed in Knots

Required p

ower

20,000

16 17 18 19 20 21

40,000

19.5

knots

2. Hydrodynamic Aspect

17

2. Hydrodynamic Aspect

Model Test Results for Manoeuvring Performance [twin/single, Full load]

-500 0 15001000

Y

1000

500

0

-500

-1000

500

X

Angle

30

0

-10

-20

10

20

-3035030025020015010050

Time

Angle

30

0

-10

-20

10

20

-30

35030025020015010050Time

40

50

-40

10/10 Zig-zag Manoeuvre

20/20 Zig-zag Manoeuvre

Turning Manoeuvre

Single skeg Twin skeg

18

Yaw Checking Ability – 10/10 Zig-zag

IMO limit

Single screw ships tested at SSPA

Twin-skeg ships tested at SSPA

Single skeg

Twin skeg

Yaw checking ability - 10/10 Zig-zag

0

10

20

5 10 20 30 40

Lpp / V [sec]

1st

Overs

hoot angle [deg]

2. Hydrodynamic Aspect

19

Yaw Checking Ability – 10/10 Zig-zag

5

10

20

30

40

5 10 20 30 40

Lpp / V [sec]

2nd

Overs

hoot angle [deg]

IMO limit

Single screw ships tested at SSPA

Twin-skeg ships tested at SSPA

Single skeg

Twin skeg

2. Hydrodynamic Aspect

20

Yaw Checking Ability – 20/20 Zig-zag versus Tactical Diameter

IMO limit

Single screw ships tested at SSPA

Twin-skeg ships tested at SSPA

Single skeg

Twin skeg

2. Hydrodynamic Aspect

5

10

15

20

25

30

35

40

45

1 1.5 2 2.5 3 3.5 4 4.5 5 5.5

Tactical diameter / Lpp [-]

1st

overs

hoot [d

eg]

21

Turning Ability

IMO limit

Single screw ships tested at SSPA

Twin-skeg ships tested at SSPA

Single skeg

Twin skeg

Turning ability

1

2

3

4

5

1 2 3 4 5

Tactical diameter / Ship length [-]

Advance

/ S

hip

length

[-]

2. Hydrodynamic Aspect

22

Spiral Tests

IMO limit

Single screw ships tested at SSPA

Twin-skeg ships tested at SSPA

Single skeg

Twin skeg

Spiral Tests

0

2

4

6

8

10

12

14

0 10 20 30 40 50

Lpp/V [sec]

Loop w

idth

[deg]

2. Hydrodynamic Aspect

23

Speed Losses on Rough Seas

2. Hydrodynamic Aspect

24

Pressure Fluctuation Levels

2. Hydrodynamic Aspect

Comparison of Measured Pressure Pulse LevelsDSME conventional size LNG Carrier

0

1

2

3

4

5

1st 2nd 3rd 4th

Order of Blade Frequency

Pre

ssure

Pulse (kPa)

Twin skeg

Single skeg

25

3. Strength Aspect

SloshingNumerical Analysis

0.71.60.61.5SLOFE2D

0.91.90.51.6Marintek PGM

1.152.2< 1.01.4LR Fluids

250 K

5 tanks

250 K

4 tanks

200K

5 tanks

200 K

4 tanks

0

0.5

1

1.5

2

2.5

200K–4 tanks 200K–5 tanks 250K–4 tanks 250K–5 tanks

Pres

sure

rat

io t

o 13

8K

K

Pres

sure

rat

io t

o 13

8K

K

Pres

sure

rat

io t

o 13

8K

K

Pres

sure

rat

io t

o 13

8K

K LR Fluids LR Fluids LR Fluids LR Fluids

Marintek PGMMarintek PGMMarintek PGMMarintek PGMSLOFE2DSLOFE2DSLOFE2DSLOFE2D

0

0.5

1

1.5

2

2.5

200K–4 tanks 200K–5 tanks 250K–4 tanks 250K–5 tanks

Pres

sure

rat

io t

o 13

8K

K

Pres

sure

rat

io t

o 13

8K

K

Pres

sure

rat

io t

o 13

8K

K

Pres

sure

rat

io t

o 13

8K

K LR Fluids LR Fluids LR Fluids LR Fluids

Marintek PGMMarintek PGMMarintek PGMMarintek PGMSLOFE2DSLOFE2DSLOFE2DSLOFE2D

Figures mean the pressure ratio to conventional 138 K LNGC.

26

3. Strength Aspect

y = 0 .8477x - 9 .1203

0

1

2

3

4

5

6

7

8

11 13 15 17 19 21% o f tank length/ ship length

Pres

sure

(ba

r)

Correlation between tank length & sloshing pressure

27

3. Strength Aspect

Sloshing Model Test

- Joint project with DSME, LR, MARINTEK

- Test for 200K LNGC with 4tanks

- 1 : 50 scale model

- Filling ratio = 10, 70, 80, 90, 95%

28

3. Strength Aspect

- Full scale drop test with information obtained from sloshing model test

Setup for drop testSetup for drop test

Drop Test of Insulation Box

29

3. Strength Aspect

Failure Mode by Drop Test

Averaged Peak Pressure at Failure mode

> Allowable pressure of 14bar

30

3. Strength Aspect

Structural Analysis (SDA)

Whole Ship Global Model

31

3. Strength Aspect

Fine Mesh Analysis

32

3. Strength Aspect

FE Analysis by DLA (Dynamic Load Approach)

Wave Load Generation

33

3. Strength Aspect

- LR FDA 2 & 3

- ABS/SFA

- Critical Structural Details

Hopper Knuckle Connections

Upper Chamfer Connections

Inn. BTM / Bulkheads

No.2 Stringer Connection

- More than 40 years

Fatigue Analysis

34

4. Propulsion Systems

� Steam turbine propulsion

� Slow speed 2-stroke diesel engine

propulsion with reliquefaction plant

� DF engine electric propulsion

� Gas turbine electric propulsion

Disposal/Treatment of BOG

35

4. Propulsion Systems

Steam turbine propulsionBOGHFO

MainBoiler

MainBoiler

Condenser

Reduction

Gear

FPP

HP

LP

SWBD

G

G D/E

G

G

S/T

S/T

S/T

36

4. Propulsion Systems

2-stroke diesel engine

Aux.Boiler

SWBD

FPP M/E

FPP M/E

HFO

G D/E

G D/E

G D/E

G D/E

ReliquefactionPlant

BOG

Emergency GasDumping(Oxidizer)

LNG ( Return to cargo tank)

37

4. Propulsion Systems

DF engine + electric propulsion LNG Forcing vaporizer

SWBD

Emergency GasDumping(Oxidizer)

MDO

G

DF

G

DF

G

DF

G

DF

BOG

FPP

M

M

FPP

G

DF

G

DF

38

4. Propulsion Systems

Gas turbine + electric propulsion

SWBD

Steam

LNG Forcing vaporizer

Emergency GasDumping(Oxidizer)

MDO

G

GT

G

GT

G

ST

BOG

FPP

M

M

FPP

HRSG Exhaust Gas

HRSG Exhaust Gas

39

4. Propulsion Systems

Comparison

H : Higher M : More

GoodGoodBadModerateEmissions

GoodBadBadGoodMaintenance

HigherHigherBase-Initial cost

MMMBaseBaseCargo volume

HHHHHHBaseEfficiency

Gas/DO/DualGas/DOHFOHFO/Gas/DualMain fuel

G/T electric

(200K)

DF electric

(200K)

Slow speed diesel (200K)

Steam

(150K)

40

5. Concluding Remarks

1. DSME has been developing various LNG carriers with different sizes and different propulsion systems in order to meet increasing demands for large LNG carriers of new generation.

2. Numerical analysis and comprehensive model tests confirmed the reliability of the large LNG carrier with 5 tanks having a capacity of 200,000 m3.

3. Structural strengths were verified through the ULS, FLS and buckling criteria.

41---[continue]

4. Following hydrodynamic advantages of the twin skeg type hull form have been verified through a comparative study:

� Reduced propeller loads, increased efficiency, very much reduced pressure pulses level

� Lower power consumption than the corresponding conventional single skeg hull form

� Higher level of maneuverability

5. Concluding Remarks

42---[continue]

5. The propulsion system of the LNG carrier shall preferably be evolved into alternatives to get better efficiency and more cargo capacity.

[Alternative propulsion systems]

� Slow speed diesel engine propulsion system with reliquefaction plant

� Electric propulsion system with dual fuel engines

� Electric propulsion system with gas turbines

5. Concluding Remarks

43---[continue]

Thank you

45