Res Propulsion

Department of Ship Technology, CUSAT, B.Tech (NA$SB), Batch – XXIX

CHAPTER 4 RESISTANCE AND POWERING

59

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4. RESISTANCE CALCULATION 4.1 Introduction The resistance of a ship at a given speed is the force required to tow the ship at that speed in smooth water, assuming no interference from the towing ship. If the hull has no appendages this is called bare hull resistance. The resistance will be equal to the components of fluid forces acting parallel to the ship centreline. The resistance of a DAT can be given by: Total resistance RT (DAT) = R bare + R bow thrusters + R pod 4.1.2 Resistance Calculation of POD: R pod can be calculated by using the equation: (from proceedings of 24th ITTC – Vol. III, Specialist committee on Azimuthing podded propulsion) Rpod = Rbody + Rfin Where, R body = ½ ρV2 S body [C body (1+ k body) + ΔCF body] R fin = ½ ρV2 S fin [C fin (1+ k fin) + ΔC Ffin] The parameters of podded propulsion system can be assumed from the parent ship data. The approximate values are: S body = 136.4 m2 (approx.) Diameter of shaft = 1.0 m. S fin = 8.4 m2 (approx.) CF body = C fin = 0.001556 (from ITTC-57 line) ΔCF body = ΔC fin =[105(ks/L)1/3 – 0.64] x 10-3 = 0.00358 (for ks = 0.015 m and L is the length of the ship) K body = K fin = 0.7 (from VTT, Finland) (The form factor, k, which is defined in pod setup and test location, is given only as qualitative information of the test results and the hull. The numerical value of form factor, k = 0.7, is rather high if it is compared with conventional hull forms. However, form factor values of this range are fairly common for icebreaking hull forms

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R body = 24.81 KN R fin = 1.52 KN The sum of the separately measured nominal total resistance (bare hull + pod drag) compared to the directly measured total resistance deviate only approximately 2 % from each other. Thus it can be concluded that there are no significant pod hull interaction despite the rather large sized pod units. (Source: VTT technical research center of Finland.) Therefore, R pod = R body + R fin = 26.33 KN (for V = 15.0 Knots) For bare hull and bow thrusters resistance calculation, we can follow different methods of calculating resistance and assume the maximum of all to decide the powering requirements. The ship stern shape is considered to be normal, and the bow has a U-shape. Saltwater properties and the speed range are detailed in the vessel condition section of NAVCAD. The input parameters for calculating resistance by any of the methods given in NAVCAD v3.1e. [X]Bare-hull: Holtrop-1984 method [X]Appendage: Holtrop-1988 method Technique: Prediction [ ]Wind : Cf type : ITTC [ ]Seas : Align to : [ ]Channel : File : [ ]Barge : Correlation allow(Ca): 0.00012 [ ]Net : [X]Roughness: 0.15mm dCa: %-7.5 [X]3-D corr : Form factor(1+k): 1.1307 [ ]Speed dependent correction ---------- Prediction results ----------------------------------------Vel kts ----10.00 11.00 12.00 13.00 14.00 15.00 16.00 17.00 18.00 19.00

Fn

Rn

Cf

[Cform]

[Cw]

Cr

Ct

----0.100 0.109 0.119 0.129 0.139 0.149 0.159 0.169 0.179 0.189

-----1.21e9 1.33e9 1.45e9 1.57e9 1.69e9 1.81e9 1.93e9 2.05e9 2.18e9 2.30e9

-------0.001495 0.001478 0.001462 0.001448 0.001435 0.001424 0.001413 0.001403 0.001393 0.001384

-------0.000195 0.000193 0.000191 0.000189 0.000188 0.000186 0.000185 0.000183 0.000182 0.000181

-------0.000963 0.000942 0.000927 0.000923 0.000935 0.000970 0.001035 0.001138 0.001294 0.001503

-------0.001159 0.001135 0.001118 0.001113 0.001123 0.001156 0.001220 0.001322 0.001476 0.001684

-------0.002774 0.002733 0.002701 0.002681 0.002678 0.002700 0.002753 0.002844 0.002989 0.003188

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Vel kts ----10.00 11.00 12.00 13.00 14.00 15.00 16.00 17.00 18.00 19.00

Rw/W

Rr/W

Rbare/W ------0.00041 0.00049 0.00058 0.00068 0.00078 0.00091 0.00105 0.00123 0.00145 0.00172

Rw kN ------257.59 304.81 357.14 417.35 490.33 583.82 708.83 879.95 1121.08 1451.57

Rr kN ------309.86 367.32 430.76 502.91 588.68 695.79 835.25 1021.64 1278.86 1626.25

Rbare kN ------741.88 884.46 1040.21 1211.80 1404.08 1624.72 1884.68 2198.50 2590.03 3078.59

PEbare kW ------3816.6 5005.1 6421.6 8104.2 10112.5 12537.4 15513.0 19227.1 23983.7 30091.5

------0.00014 0.00017 0.00020 0.00023 0.00027 0.00033 0.00040 0.00049 0.00063 0.00081

------0.00017 0.00021 0.00024 0.00028 0.00033 0.00039 0.00047 0.00057 0.00071 0.00091

Vel kts ----10.00 11.00 12.00 13.00 14.00 15.00 16.00 17.00 18.00 19.00

Rapp kN ------5.60 6.76 8.02 9.38 10.85 12.43 14.11 15.90 17.79 19.78

Rwind kN ------0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Rseas kN ------0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Rchan kN ------0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Rother kN ------0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Rtotal kN ------747.49 891.22 1048.23 1221.18 1414.94 1637.15 1898.79 2214.40 2607.82 3098.37

PEtotal kW ------3845.4 5043.3 6471.1 8167.0 10190.7 12633.3 15629.1 19366.1 24148.4 30284.8

Condition data Water type: Custom Mass density: 1008 kg/m3 Kinematic visc: 1.16e-06 m2/s ---------- Hull data -------------------------------------------------Primary: Length between PP: WL aft of FP: Length on WL: Max beam on WL: Draft at mid WL: Displacement bare: Max area coef(Cx): Waterplane coef: Wetted surface: Loading:

263.000 m 0.000 m 272.500 m 48.700 m 16.750 m 182642.0 t 0.985 0.920 20052.0 m2 Load draft

Secondary: Trim by stern: LCB aft of FP: Bulb ext fwd FP: Bulb area at FP: Bulb ctr abv BL: Transom area: Half ent angle: Stern shapes: Bow shape:

Parameters: Holtrop-1984 method Fn(Lwl) [0.10..0.80] 0.10* Fn-high [0.10..0.80] 0.19 Cp(Lwl) [0.55..0.85] 0.83 Lwl/Bwl [3.90..14.90] 5.60 Bwl/T [2.10..4.00] 2.91

62

0.000 126.820 6.150 42.000 6.150 15.000 52.000 U-shape Normal

m m m m2 m m2 deg

Department of Ship Technology, CUSAT, B.Tech (NA$SB), Batch – XXIX

Appendages Total wetted surface (ex. thruster): Rudders: 0.000 m2 Drag coefficient: Shaft brackets: 0.000 .................. Skeg: 0.000 .................. Strut bossing: 0.000 .................. Hull bossing: 0.000 .................. Exposed shafts: 0.000 .................. Stabilizer fins: 0.000 .................. Dome: 0.000 .................. Bilge keels: 60.000 .................. Bow thruster diam: 2.500 m ..................

Application: Resistance Hull type : Displacement Description:

7 Feb 08 19:25 File name: untitled.nc3

0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 1.400 0.007

Page 3

---------- Environment data ------------------------------------------Wind: Wind speed: Angle off bow: Tran hull area: VCE above WL: Tran superst area: VCE above WL: Total longl area: VCE above WL: Wind speed: Arrangement:

60.000 kts 30.000 deg 0.000 m2 0.000 m 0.000 m2 0.000 m 0.000 m2 0.000 m Free stream Tanker/Bulk

Seas: Sig. wave height: Modal wave period:

0.000 m 0.000 sec

Channel: Channel Channel Side Wetted hull

0.000 0.000 0.000 0.000

Vel Fn Rn Cf [Cform] [Cw] Cr Ct

Symbols and values Ship speed Froude number Reynolds number Frictional resistance coefficient Viscous form resistance coefficient Wave-making resistance coefficient Residuary resistance coefficient Bare-hull resistance coefficient

Rw/W Rr/W Rbare/W Rw Rr Rbare PEbare

Wave-making resist-displ merit ratio Residuary resist-displ merit ratio Bare-hull resist-displ merit ratio Wave-making resistance component Residuary resistance component Bare-hull resistance Bare-hull effective power

Rapp Rwind Rseas Rchan Rother Rtotal PEtotal

Additional appendage resistance Additional wind resistance Additional sea-state resistance Additional channel resistance Other added resistance Total vessel resistance Total effective power

*

Exceeds speed parameter

63

width: depth: slope: girth:

m m deg m

Department of Ship Technology, CUSAT, B.Tech (NA$SB), Batch – XXIX

BSRA METHOD The bare hull resistance and the resistance by bow thrusters of the vessel is calculated by using the software NavCAD v3.1e. The results are shown below: Analysis parameters [X]Bare-hull: BSRA series [X]Appendage: Holtrop-1988 method Technique: Prediction [ ]Wind : Cf type : ITTC [ ]Seas : Align to : [ ]Channel : File : [ ]Barge : Correlation allow(Ca): 0.00012 [ ]Net : [X]Roughness: 0.15mm dCa: %-7.5 [X]3-D corr : Form factor(1+k): 1.1307 [ ]Speed dependent correction

Vel kts ----10.00* 11.00* 12.00* 13.00* 14.00* 15.00 16.00 17.00 18.00 19.00

Fn

Rn

----0.100 0.109 0.119 0.129 0.139 0.149 0.159 0.169 0.179 0.189

-----1.21e9 1.33e9 1.45e9 1.57e9 1.69e9 1.81e9 1.93e9 2.05e9 2.18e9 2.30e9

Prediction results Cf [Cform] -------0.001495 0.001478 0.001462 0.001448 0.001435 0.001424 0.001413 0.001403 0.001393 0.001384

-------0.000195 0.000193 0.000191 0.000189 0.000188 0.000186 0.000185 0.000183 0.000182 0.000181

Vel kts ----10.00* 11.00* 12.00* 13.00* 14.00* 15.00 16.00 17.00 18.00 19.00

Rw/W

Rr/W

Rbare/W

------0.00009 0.00013 0.00016 0.00020 0.00024 0.00027 0.00031 0.00040 0.00057 0.00081

------0.00012 0.00016 0.00020 0.00025 0.00029 0.00033 0.00038 0.00048 0.00066 0.00091

Vel kts ----10.00* 11.00* 12.00* 13.00* 14.00* 15.00 16.00 17.00 18.00 19.00

Rapp kN ------5.60 6.76 8.02 9.38 10.85 12.43 14.11 15.90 17.79 19.78

Rwind kN ------0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

[Cw]

Cr

Ct

-------0.000633 0.000706 0.000760 0.000793 0.000804 0.000793 0.000801 0.000927 0.001184 0.001511

-------0.000829 0.000899 0.000951 0.000982 0.000992 0.000979 0.000986 0.001110 0.001366 0.001691

-------0.002444 0.002497 0.002533 0.002551 0.002547 0.002523 0.002519 0.002632 0.002879 0.003196

------0.00036 0.00045 0.00054 0.00064 0.00075 0.00085 0.00096 0.00114 0.00139 0.00172

Rw kN ------169.41 228.55 292.66 358.51 421.64 477.39 548.76 716.21 1025.93 1458.54

Rr kN ------221.68 291.07 366.28 444.07 519.99 589.37 675.18 857.90 1183.71 1633.22

Rbare kN ------653.70 808.21 975.73 1152.96 1335.39 1518.29 1724.61 2034.76 2494.88 3085.55

PEbare kW ------3362.9 4573.6 6023.5 7710.7 9617.8 11716.2 14195.5 17795.1 23102.6 30159.6

Rseas kN ------0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Rchan kN ------0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Rother kN ------0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Rtotal kN ------659.31 814.97 983.75 1162.34 1346.24 1530.72 1738.72 2050.66 2512.67 3105.34

PEtotal kW ------3391.8 4611.8 6073.0 7773.5 9695.9 11812.1 14311.6 17934.1 23267.3 30353.0

64

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The above data give resistance of bare hull and the resistance offered by one bow thrusters Hence the total resistance, (from Holltorp Menon - 1984 Method) RT (DAT) = Rbare + 2 x Rbow thrusters + Rpod For V = 15.0 knots (From Holltrop – Menon 1984 Method) RT (DAT) =

1637.15+ 2 x 12.43+ 26.33 KN

=

1688.34 KN

Table 4.1 Total resistance Guldhammer – Harvald Method: 2 x Rbow Speed Rbare Rpod RT (DAT) PE (DAT) thrusters (KN) (KW) (Knots) (KN) (KN) (KN) 10 640.06 11.20 11.70 662.96 3410.25 11 768.90 13.52 14.16 796.58 4507.38 12 909.11 16.04 16.85 942.00 5814.77 13 1069.65 18.76 19.77 1108.18 7410.65 14 1249.57 21.70 22.93 1294.20 9320.32 15 1487.56 24.86 26.33 1538.75 11873.00 16 1801.46 28.22 29.95 1859.63 15305.53 17 2126.36 31.80 33.82 2191.98 19168.44 18 2531.69 35.58 37.91 2605.18 24121.88

25 20 15 P E(MW) R T(10^5N) 10 RT 5

10

PE

12

14

16

18

FIG 4.1 Graph from Guldhammer- Harvald method of resistance calculation.

65

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Table 4.2 Total resistance by Holltrop – Menon 1984 Method: 2 x Rbow Speed (Knots) 10 11 12 13 14 15 16 17 18

Rbare (KN) 747.49 891.22 1048.23 1221.18 1414.94 1637.15 1898.79 2214.4 2607.82

Rpod (KN) 11.70 14.16 16.85 19.77 22.93 26.33 29.95 33.82 37.91

thrusters

(KN) 11.20 13.52 16.04 18.76 21.70 24.86 28.22 31.80 35.58

RT (DAT) (KN) 770.39 918.90 1081.12 1259.71 1459.57 1688.34 1956.96 2280.02 2681.31

PE (DAT) (KW) 3962.89 5199.50 6673.54 8423.93 10511.24 13027.23 16106.56 19938.32 24826.79

25 20 15 P E(MW) R T(10^5N)

10

RT PE

5

10

12

14

16

18

FIG 4.2 Graph from Holltrop-Menon 1984 method of resistance calculation.

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Table 4.3 Total resistance by BSRA Method: 2 x Rbow (KN)

Rpod (KN)

RT (DAT) (KN)

PE (DAT) (KW)

653.7

11.20

11.70

676.60

3480.43

11

808.21

13.52

14.16

835.89

4729.80

12

975.73

16.04

16.85

1008.62

6226.01

13

1152.96

18.76

19.77

1191.49

7967.73

14

1335.39

21.70

22.93

1380.02

9938.35

15

1518.29

24.86

26.33

1569.48

12110.11

16

1724.61

28.22

29.95

1782.78

14672.99

17

2034.76

31.80

33.82

2100.38

18367.40

18

2494.88

35.58

37.91

2568.37

23781.05

Speed (Knots)

Rbare (KN)

10

thrusters

25 20 15 P E(MW) R T(10^5N) 10

RT

PE

5 10

14

12

16

18

FIG 4.3 Graph from BSRA method of resistance calculation.

67

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From these three methods, Holltrop and Menon 1984 have the max value of resistance.

4.2 Powering Calculation 4.2.1 Introduction This deals with the selection of the main engine. The derivation of the engine power starts from resistance at service speed. A preliminary design of the podded machinery can be done which would deliver the required thrust. The selection of the pod is done on the basis of model test results carried out in the proceedings of 24th ITTC, Vol. – II (Special committee on Podded Propulsion). The Model tests were carried out for the Ice capable ships Mewis (2001) and Ukon et al (2003). The main engine is selected according to this parameter. Then an optimum for this engine is decided. Propeller design is done with the help of T-J and P-J charts. Wake fraction (w) w

=

0.55CB-0.20

=

0.261

(FSICR Research Report No 53)

Thrust deduction factor (t) t = 1.25w (FSICR Research Report No 53) RT

=

0 .326

=

1688.34KN

An allowance of 25% is provided to get service condition resistance. RT

= 1688.34 *1.25 =

Thrust calculation Required thrust = =

2110.5 KN

RT/(1-t) 3131.3 KN

68

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Velocity of advance (VA) VA

=

V (1-w)

=

15.0 × 0.5144(1-0.261) m/s

= 5.702 m/s Diameter of propeller D = 2/3 T = 11.166 m T = draft D selected = 7.75 m (twin Azipod propeller) Td

=

√T/ρ/ (D × VA)

In this case Td

=

(1/7.75× 5.7021) √(1565.65 /1.008)

=

0.89

From Model results: (Table 4.4 Model used for Extrapolation) (24th ITTC - Volume II) Particulars (AE/AO) Diameter (mm) Pitch Ratio Boss Ratio No. of Blades Rotation direction

Ukon et al.

TU032 (VTT)

Mewis

0.55 200 0.800 0.280 4 Right

0.537 200 0.850 0.278 4 Right

0.58 215.15 1.104 0.276 4 Right

Values of J, KQ are read off from T-J chart where the Td=0.89 line intersects the optimum efficiency line for optimizing n. This is done for AE/AO = 0.4, 0.55 and 0.70 Graphs are drawn with J and KQ versus AE/AO .Then the values of J and KQ for AE/AO = 0.55, 0.537 and 0.58 are found out for z = 4.

69

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Table 4.5 KQ, J values for 4 bladed propellers

AE/A0

J

KQ

0.4

0.47

0.0225

0.55

0.565

0.04

0.7

0.515

0.031

Fig 4.4 Graph to find KQ, J values for 4 bladed propeller

70

Department of Ship Technology, CUSAT, B.Tech (NA$SB), Batch – XXIX

From the above graph: Table 4.6 J, KQ Values from the Graph above

Ae/Ao

J

KQ

0.537

0.563

0.0398

0.55

0.565

0.04

0.58

0.564

0.0395

For AE/AO

=

0.537; J= 0.563

J n PD

= = =

0.563 VA/J×D = 1.306 2π×ρ×n3×D5× KQ

=

15698.62 KW

=

T× VA /PD

=

0.5686

=

56.86 %

η0

KQ = 0.0398

Table 4.7 n, PD and η0 for the models: Ae/Ao

0.537

0.550

0.580

J

0.563

0.565

0.564

KQ n

0.0398 1.306

0.0400 1.302

0.0395 1.304

PD (KW)

15698.62

15632.98

15508.82

η0(%)

56.86

57.1

57.5

The FP propeller with BAR of 0.58 can be selected

71

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4.2.2 Brake power calculation (for ahead running condition) PD

=

15508.82 KW

PB

=

PD /( ηm x ηt x ηg )

ηm

= Efficiency of motor = 0.96

ηt

= Efficiency of transformer

[Ref30]

= 0.97 ηg

= Efficiency of generator = 0.96

PB

= 15508.82/ (0.96*0.97*0.96) = 17348.6 KW

4.2.5 Engine selection In order to utilize Azipod propulsion system the ship has an electric power plant. Generator sets are connected to the main electric switchboard to distribute electric power for all power consumers onboard, including Azipod propulsion. In case of diesel electric power plant all the diesel engines can be of the same type as of the conventional vessel, which minimizes the spare parts inventories. The number of vulnerable auxiliary systems is reduced to a minimum. Diesel Engines Type: 9TM620 Number:3 Manufacturer: STORK WARTSILA DIESEL CO. Holland Rated output: 12,750KW Rated speed: 428rpm Consumption of heavy fuel oil: 174G/KWH +5% Consumption of lube oil: 1.3+0.3G/KWH Greatest weight/piece: 270T Generators Type: HSG 1600 S14 Number: 3 Rated capacity: 15,537 KVA Cos Factor: 0.8 Frequency: 50 HZ

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Rated current: 815A Rated voltage: 11KV Greatest weight/piece: 55T Rated speed: 429 rpm Rated output: 12.43 MW Transformers Number: 2 Type: STROD/BTRD. Rated voltage: 11KV/121KV Weight: 58T Auxiliary engines Type: SKU CUIN-1400N305, Model 1400 GQKA Number: 3 Manufacturer: Cummins Rated output: 1400 kW Rated capacity: 1400 kW (1750 kVA) 60 Hz or 1166.7 kW (1458.3 kVA) 50 Hz The engine is well suited for operation on low-quality fuels and intended to drive the generator directly without any speed changing device. Normally generators are running at higher rpm, but selected engine is medium speed engine using heavy fuel oil. This engine has been especially designed for such specific purpose only.

Brake power calculation (for ahead running condition) PB ηm

= 19125 KW = Efficiency of motor = 0.96

ηt

= Efficiency of transformer = 0.97

ηg

= Efficiency of generator

PD

= 0.96 = P (Generator)x( ηm x ηt x ηg )

PD

=

17096.8 KW

73

[Ref30]

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4.3 Selection of POD: Power transmission and steering module is installed to the ship hull at a convenient phase of ship construction. Pre-fabricated pod including strut and motor are delivered, installed and connected to the power and steering module separately on the most suitable phase only just before launching of the ship. The Azipod unit itself has a flexible design. It can be built for pushing or pulling in open water or ice conditions. PD

=

17096.8 KW

Hence from Azipod performance curve, V25 type Azipod can be selected with special material requirements of Ice class operations. Pod parameters are as follows PD

=

RPM

=

17096.8 KW 110

Fig 4.5 Power (KW) Vs Propeller speed [Ref30]

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Fig 4.6 Azipod main dimension drawing [Ref30] For V25 type (from ABB) [Project Guide for Azipod Propulsion Systems, Version 5.2] A B C D E F G H J K L Tilt angle

= = = = = = = = = = = =

13500 mm 7050 mm 6500 mm 7750 mm (Given propeller diameter) 1600 mm 3355 mm 4900 mm 550 mm 2500 mm 2600 mm 6445 mm 0o to 6o, Selected = 3o

Fig 4.7 [Ref30] 75

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Weight of V25 Standard Azipod = Complete weight excluding propeller + Weight of AZU (Azipod unit) + Weight of STU (Steering unit) + Weight of SRP (Slip ring unit) + Weight of CAU (cooling air unit) + Weight of HPY (Hydraulic power unit) + other ancillaries + weight of propeller [Ref30] = 315 + 175 + 85 + 4 + 10 + 5 + 8 + 60 = 662 tons

4.4 Design of propeller to match the selected pod PD

=

17096.8 KW

RPM

=

1.833

VA

=

5.7021 m/s

PN

=

(n/ VA 2)(P/2π × ρ × VA)1/2

PN

=

1.833/ (5.702)2 × (17096.8 /2π × 1.008 × 5.702)1/2

=

1.22

Steps to get performance values for Wageningen B-Series propeller using P-J charts. a) . Find the point of intersection of PN = 1.22 line with the η optimum for PN constant b) Read off J, where J = Advance coefficient c) Increase J by 6 %. d) At this J’=J(1.06), find the propeller characteristic where J’ meets e) For PN = 1.22 From J’ we can find the value of KT for given (AE/AO) = 0. 4 ,0.55 and 0.70after Interpolating the values of J’ and KT from the P-J charts Table 4.8 performance values 0.4 0.55 0.70 AE/Ao J

0.385

0.408

0.43

J' (=J*1.06)

0.408

0.432

0.456

KT

0.158

0.175

0.208

P/D

0.68

0.75

0.77

D

7.635

7.204

6.836

T

1812.4

1591.6

1533.3

AE/Ao(min)

0.476

0.522

0.568

ηO

60.45

53.08

51.14

76

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Minimum blade area ratio to avoid capitation (A /A ) E

O min

= [((1.3 + 0.3Z) T) / ((P

2

atm

+ ρgh – P ) D )]+ K [Auf’en Keller formula] V

WhereK = 0.1 for twin screw propellers Z = number of blades

h = height of LWL above shaft central line in meters P

atm

= 101.366 kN/m2

P = 1.704 kN/m2 V

h = 8.0 m D = 7.75 m K = 0.1 for double screw propellers ρ = 1.008 t/m

3 2

g = acceleration due to gravity (9.81 m/s ) =0.47

1900 T 1700 0.8

0.8

0.6 0.6

N0

D AE/A0

0.5

Kt

1cm=0.001

2 3

N0 P/D

1cm=0.001

4

Ae/Ao 1cm=0.001

5

j*

1cm=0.002

6

T

1cm=2KN

1cm=0.001

0.6 0.6 0.5

PROPELLER PARTICULARS

no

P/D

0.4

TYPE

:

FPP WAGENINGEN B - SERIES RIGHT HANDED SCREW

Ae/Ao

kt 0.3

0.4

1500 0.7 0.7 D(m)

P/D

T(KN)

0.7

1

0.3 J*

0.2

j*

0.1

.55

:

4

D

:

7.26m

P/D

:

0.742

Ae/Ao

:

0.527

MATERIAL

:

Ni - Al Bronze

0.2

KT

0.4

NO. OF BLADE

.7

Table 4.8 performance curves

77

Department of Ship Technology, CUSAT, B.Tech (NA$SB), Batch – XXIX

Particulars of selected propellers D

:

7.26 m

Z

:

4

AE/AO

:

0.527

P/D

:

0.742

T

:

1612.56 KN

ηO

:

53.8

Material

:

Lloyd’s grade Cu 4 Manganese Aluminium Bronze

Type

:

Wageningen B –series Fixed pitch

Tensile strength N/mm2 minimum: 630N/mm2 Chemical composition of propeller and propeller blade castings Sn 70-80%, Pb-6% Ni-0.05%, Fe-1.-3% Al-5-9%, Mn-8-20% Zn-1%

4.5 Determination of ice torque Dimensions of propellers, shafting and gearing are determined by formulae taking into account the impact when a propeller blade hits ice. The ensuing load is hereinafter called the ice torque M. M = m ‫ ڄ‬D2 ton meters where: D = diameter of propeller in meters m = 2.15 for ice class IA Super = 1.60 (IA) = 1.33 (IB) = 1.22 (IC)

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Department of Ship Technology, CUSAT, B.Tech (NA$SB), Batch – XXIX

If the propeller is not fully submerged when the ship is in ballast condition, the ice torque for ice class IA is to be used for ice classes IB and IC. M = =

2.15X7.262 113.32 ton meters

The elongation of the material used is not to be less than 19%, preferably less than 22% for a test piece length = 5 d and the value for the Charpy V-notch test is not to be less than 2.1 kpm at –10°C. Width c and thickness t of propeller blade sections are to be determined so that: a) at the radius 0.25 D/2, for solid propellers

t = 23.85 cm b) at the radius 0.35 D/2 for FP-propellers

t = 20.31 cm c) at the radius 0.6 D/2

t = 13.06 cm Where: c = length in cm of the expanded cylindrical section of the blade, at the radius in question t = the corresponding maximum blade thickness in cm H = propeller pitch in meters at the radius in question. = 5.386 (For controllable pitch propellers 0.7 H nominal is to be used.) Ps = shaft engine output according to 3.1, but expressed in horsepower [hp] = 22927.18hp n = propeller revolutions [rpm] = 110

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Department of Ship Technology, CUSAT, B.Tech (NA$SB), Batch – XXIX

M = ice torque =113.32 ton meters Z = number of blades =4 σ b = tensile strength in kp/mm2 of the material =31.5kp/mm2 The blade tip thickness t at the radius 1.0 D/2 is to be determined by the following formulae: Ice Class IA Super

t = 43.49 mm Ice Classes IA, IB and IC

Where D and σb are as defined previously a) The thickness of other sections is governed by a smooth curve connecting the above section thicknesses. b) Where the blade thickness derived is less than the class rule thickness, the latter is to be used. c) The thickness of blade edges is not to be less than 50% of the derived tip thickness t, measured at 1.25 t from the edge. For controllable pitch propellers this applies only to the leading edge. d) The strength of mechanisms in the boss of a controllable pitch propeller is to be 1.5 times that of the blade when a load is applied at the radius 0.9 D/2 in the weakest direction of the blade.

Screw shaft The diameter of the screw shaft at the aft bearing is not to be less than:

80

Department of Ship Technology, CUSAT, B.Tech (NA$SB), Batch – XXIX

Where σb = tensile strength of the blade in kp/mm2 (49.0kp/mm2) ct2 = value derived =94667.3 σy = yield stress of the shaft in kp/mm2 (31.5kp/mm2) ds=570.3m

4.6 Propeller Geometry Tables 4.9 Propeller geometry PROPELLER OFFSETS (all dimensions in m) r/R 0.20 0.30 0.40 Dis from CL TO TE 0.599 0.684 0.766 Dis from CL TO LE 0.963 1.080 1.156 chord length 1.562 1.764 1.922 tmax 0.267 0.236 0.206 LE-Tmax 0.547 0.618 0.673

0.50

0.60

0.70

0.80

0.90

1.00

0.837 0.901

0.958 0.992 0.965 0.413

1.182 2.019 0.175 0.717

1.055 2.013 0.114 0.892

1.151 2.053 0.144 0.798

0.855 1.847 0.083 0.885

0.520 1.485 0.052 0.742

* 0.413 0.045 *

Tables 4.10 Ordinates for the back (As distance in meters) From maximum thickness to trailing From maximum thickness to leading edge edge r/R 100 80 60 40 20 20 40 60 80 90 95 100 0.2 * 0.14 0.19 0.23 0.26 0.26 0.25 0.23 0.20 0.17 0.15 * 0.3 * 0.12 0.17 0.21 0.23 0.23 0.22 0.20 0.17 0.15 0.13 * 0.4 * 0.10 0.14 0.18 0.20 0.20 0.19 0.17 0.14 0.12 0.11 * 0.5 * 0.08 0.12 0.15 0.17 0.17 0.16 0.14 0.12 0.10 0.09 * 0.6 * 0.06 0.10 0.12 0.14 0.14 0.13 0.11 0.09 0.08 0.06 * 0.7 * 0.04 0.08 0.10 0.11 0.11 0.10 0.09 0.06 0.05 0.04 * 0.8 * 0.03 0.06 0.07 0.08 0.08 0.07 0.06 0.04 0.03 0.02 * 0.9 * 0.02 0.04 0.05 0.05 0.05 0.05 0.04 0.02 0.02 0.01 * 1 * 0.01 0.02 0.02 0.02 0.02 0.02 0.02 0.01 0.01 0.00 *

81

Department of Ship Technology, CUSAT, B.Tech (NA$SB), Batch – XXIX

Tables 4.11 Ordinates for the face (As distance in meters) From maximum thickness to From maximum thickness to leading trailing edge edge r/R 100 80 60 40 20 20 40 60 80 90 95 0.2 0.08 0.05 0.03 0.01 0.00 0.00 0.01 0.02 0.04 0.05 0.07 0.3 0.06 0.03 0.01 0.00 0 0.00 0.00 0.01 0.03 0.04 0.05 0.4 0.04 0.01 0.00 0 0 0 0.00 0.01 0.02 0.03 0.04 0.5 0.02 0.00 0 0 0 0 0 0.00 0.01 0.01 0.02 0.6 0.01 0 0 0 0 0 0 0 0.00 0.01 0.01 0.7 0 0 0 0 0 0 0 0 0 0.00 0.00 0.8 0 0 0 0 0 0 0 0 0 0 0

100 0.11 0.09 0.07 0.05 0.04 0.02 0.01

4.7 Power requirement for Ice operations (Astern running condition): For Ice breaking speed of 1 m/s (“Icebreaker performance prediction” by Arno Keinomen, Robin P Brown, Colin R Revill and Ian M Bayly, SNAME R1 = 0.015CSCHB0.7L0.2T0.1H1.25[1-0.0083(t + 30)][0.63 + 0.00074σF][1 + 0.0018(90 – ψ)1.6][1 + 0.003(φ – 5)1.5] x 103 KN Where, CS = Salinity coefficient = 0.85 (for brackish Ice) CH = Hull condition coefficient = 1.33 (for new steel) B = Beam of ship = 48.7 m L = Length of ship at LWL = 272.5 m T = Designed draft = 16.75 m H = Thickness of Ice t = Ice surface air temperature = taken as -10oC (most severe condition) ψ = flare angle = 65 o φ = buttock angle = 24o σF = 270 KPa (for Baltic Ice) R1 = Level Ice resistance at 1 m/s for rounded type icebreakers

82

Department of Ship Technology, CUSAT, B.Tech (NA$SB), Batch – XXIX

= 1154.05 KN (for H = 1.0 m, most severe Ice condition thickness) Since, R α V2 For Designed Ice speed of 5.0 Knots in 1.0 m thick Ice R

1154.05 x VICE2

=

Required delivered power = R x VICE2 x 0.85 (assume 15% reduction for a DAT) = 980.93 VICE2 ηH

=

PE

ASTERN SPEED IN KNOTS

VICE (maximum)

(1-t)/(1-w)

=

0.912

=

PT X ηH KW

=

(1612.56X5.702X2) X 0.912 (Twin Azipod)

=

16771.3 KW

=

(PE/980.93)1/3

=

2.576 m/s

VICE (Maximum)

=

5.008 Knots

8.0 7.0 6.0 5.0 4.0

0.4

0.6

0.8

1.0

1.2

1.4

1.6

THICKNESS OF ICE IN m

Fig 4.9 Ice thickness (HICE) vs. VICE Hence for minimum Ice speed of 5 Knots is achievable with the selected model of Pod and the brake power calculation.

83