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Department of Ship Technology, CUSAT, B.Tech (NA$SB), Batch – XXIX 59 CHAPTER 4 RESISTANCE AND POWERING

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Page 1: Res Propulsion

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

59

CHAPTER 4

RESISTANCE AND POWERING

Page 2: Res Propulsion

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

60

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 Fn Rn Cf [Cform] [Cw] Cr Ct kts ----- ----- ------ -------- -------- -------- -------- -------- 10.00 0.100 1.21e9 0.001495 0.000195 0.000963 0.001159 0.002774 11.00 0.109 1.33e9 0.001478 0.000193 0.000942 0.001135 0.002733 12.00 0.119 1.45e9 0.001462 0.000191 0.000927 0.001118 0.002701 13.00 0.129 1.57e9 0.001448 0.000189 0.000923 0.001113 0.002681 14.00 0.139 1.69e9 0.001435 0.000188 0.000935 0.001123 0.002678 15.00 0.149 1.81e9 0.001424 0.000186 0.000970 0.001156 0.002700 16.00 0.159 1.93e9 0.001413 0.000185 0.001035 0.001220 0.002753 17.00 0.169 2.05e9 0.001403 0.000183 0.001138 0.001322 0.002844 18.00 0.179 2.18e9 0.001393 0.000182 0.001294 0.001476 0.002989 19.00 0.189 2.30e9 0.001384 0.000181 0.001503 0.001684 0.003188

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Vel Rw/W Rr/W Rbare/W Rw Rr Rbare PEbare kts kN kN kN kW ----- ------- ------- ------- ------- ------- ------- ------- 10.00 0.00014 0.00017 0.00041 257.59 309.86 741.88 3816.6 11.00 0.00017 0.00021 0.00049 304.81 367.32 884.46 5005.1 12.00 0.00020 0.00024 0.00058 357.14 430.76 1040.21 6421.6 13.00 0.00023 0.00028 0.00068 417.35 502.91 1211.80 8104.2 14.00 0.00027 0.00033 0.00078 490.33 588.68 1404.08 10112.5 15.00 0.00033 0.00039 0.00091 583.82 695.79 1624.72 12537.4 16.00 0.00040 0.00047 0.00105 708.83 835.25 1884.68 15513.0 17.00 0.00049 0.00057 0.00123 879.95 1021.64 2198.50 19227.1 18.00 0.00063 0.00071 0.00145 1121.08 1278.86 2590.03 23983.7 19.00 0.00081 0.00091 0.00172 1451.57 1626.25 3078.59 30091.5 Vel Rapp Rwind Rseas Rchan Rother Rtotal PEtotal kts kN kN kN kN kN kN kW ----- ------- ------- ------- ------- ------- ------- ------- 10.00 5.60 0.00 0.00 0.00 0.00 747.49 3845.4 11.00 6.76 0.00 0.00 0.00 0.00 891.22 5043.3 12.00 8.02 0.00 0.00 0.00 0.00 1048.23 6471.1 13.00 9.38 0.00 0.00 0.00 0.00 1221.18 8167.0 14.00 10.85 0.00 0.00 0.00 0.00 1414.94 10190.7 15.00 12.43 0.00 0.00 0.00 0.00 1637.15 12633.3 16.00 14.11 0.00 0.00 0.00 0.00 1898.79 15629.1 17.00 15.90 0.00 0.00 0.00 0.00 2214.40 19366.1 18.00 17.79 0.00 0.00 0.00 0.00 2607.82 24148.4 19.00 19.78 0.00 0.00 0.00 0.00 3098.37 30284.8 Condition data Water type: Custom Mass density: 1008 kg/m3 Kinematic visc: 1.16e-06 m2/s ---------- Hull data -------------------------------------------------- Primary: Secondary: Length between PP: 263.000 m Trim by stern: 0.000 m WL aft of FP: 0.000 m LCB aft of FP: 126.820 m Length on WL: 272.500 m Bulb ext fwd FP: 6.150 m Max beam on WL: 48.700 m Bulb area at FP: 42.000 m2 Draft at mid WL: 16.750 m Bulb ctr abv BL: 6.150 m Displacement bare: 182642.0 t Transom area: 15.000 m2 Max area coef(Cx): 0.985 Half ent angle: 52.000 deg Waterplane coef: 0.920 Stern shapes: U-shape Wetted surface: 20052.0 m2 Bow shape: Normal Loading: Load draft 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

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Appendages Total wetted surface (ex. thruster): Rudders: 0.000 m2 Drag coefficient: 0.000 Shaft brackets: 0.000 .................. 0.000 Skeg: 0.000 .................. 0.000 Strut bossing: 0.000 .................. 0.000 Hull bossing: 0.000 .................. 0.000 Exposed shafts: 0.000 .................. 0.000 Stabilizer fins: 0.000 .................. 0.000 Dome: 0.000 .................. 0.000 Bilge keels: 60.000 .................. 1.400 Bow thruster diam: 2.500 m .................. 0.007 Application: Resistance 7 Feb 08 19:25 Page 3 Hull type : Displacement File name: untitled.nc3 Description: ---------- Environment data ------------------------------------------- Wind: Seas: Wind speed: 60.000 kts Sig. wave height: 0.000 m Angle off bow: 30.000 deg Modal wave period: 0.000 sec Tran hull area: 0.000 m2 VCE above WL: 0.000 m Channel: Tran superst area: 0.000 m2 Channel width: 0.000 m VCE above WL: 0.000 m Channel depth: 0.000 m Total longl area: 0.000 m2 Side slope: 0.000 deg VCE above WL: 0.000 m Wetted hull girth: 0.000 m Wind speed: Free stream Arrangement: Tanker/Bulk Symbols and values Vel Ship speed Fn Froude number Rn Reynolds number Cf Frictional resistance coefficient [Cform] Viscous form resistance coefficient [Cw] Wave-making resistance coefficient Cr Residuary resistance coefficient Ct Bare-hull resistance coefficient Rw/W Wave-making resist-displ merit ratio Rr/W Residuary resist-displ merit ratio Rbare/W Bare-hull resist-displ merit ratio Rw Wave-making resistance component Rr Residuary resistance component Rbare Bare-hull resistance PEbare Bare-hull effective power Rapp Additional appendage resistance Rwind Additional wind resistance Rseas Additional sea-state resistance Rchan Additional channel resistance Rother Other added resistance Rtotal Total vessel resistance PEtotal Total effective power * Exceeds speed parameter

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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 Prediction results Vel Fn Rn Cf [Cform] [Cw] Cr Ct kts ----- ----- ------ -------- -------- -------- -------- -------- 10.00* 0.100 1.21e9 0.001495 0.000195 0.000633 0.000829 0.002444 11.00* 0.109 1.33e9 0.001478 0.000193 0.000706 0.000899 0.002497 12.00* 0.119 1.45e9 0.001462 0.000191 0.000760 0.000951 0.002533 13.00* 0.129 1.57e9 0.001448 0.000189 0.000793 0.000982 0.002551 14.00* 0.139 1.69e9 0.001435 0.000188 0.000804 0.000992 0.002547 15.00 0.149 1.81e9 0.001424 0.000186 0.000793 0.000979 0.002523 16.00 0.159 1.93e9 0.001413 0.000185 0.000801 0.000986 0.002519 17.00 0.169 2.05e9 0.001403 0.000183 0.000927 0.001110 0.002632 18.00 0.179 2.18e9 0.001393 0.000182 0.001184 0.001366 0.002879 19.00 0.189 2.30e9 0.001384 0.000181 0.001511 0.001691 0.003196 Vel Rw/W Rr/W Rbare/W Rw Rr Rbare PEbare kts kN kN kN kW ----- ------- ------- ------- ------- ------- ------- ------- 10.00* 0.00009 0.00012 0.00036 169.41 221.68 653.70 3362.9 11.00* 0.00013 0.00016 0.00045 228.55 291.07 808.21 4573.6 12.00* 0.00016 0.00020 0.00054 292.66 366.28 975.73 6023.5 13.00* 0.00020 0.00025 0.00064 358.51 444.07 1152.96 7710.7 14.00* 0.00024 0.00029 0.00075 421.64 519.99 1335.39 9617.8 15.00 0.00027 0.00033 0.00085 477.39 589.37 1518.29 11716.2 16.00 0.00031 0.00038 0.00096 548.76 675.18 1724.61 14195.5 17.00 0.00040 0.00048 0.00114 716.21 857.90 2034.76 17795.1 18.00 0.00057 0.00066 0.00139 1025.93 1183.71 2494.88 23102.6 19.00 0.00081 0.00091 0.00172 1458.54 1633.22 3085.55 30159.6 Vel Rapp Rwind Rseas Rchan Rother Rtotal PEtotal kts kN kN kN kN kN kN kW ----- ------- ------- ------- ------- ------- ------- ------- 10.00* 5.60 0.00 0.00 0.00 0.00 659.31 3391.8 11.00* 6.76 0.00 0.00 0.00 0.00 814.97 4611.8 12.00* 8.02 0.00 0.00 0.00 0.00 983.75 6073.0 13.00* 9.38 0.00 0.00 0.00 0.00 1162.34 7773.5 14.00* 10.85 0.00 0.00 0.00 0.00 1346.24 9695.9 15.00 12.43 0.00 0.00 0.00 0.00 1530.72 11812.1 16.00 14.11 0.00 0.00 0.00 0.00 1738.72 14311.6 17.00 15.90 0.00 0.00 0.00 0.00 2050.66 17934.1 18.00 17.79 0.00 0.00 0.00 0.00 2512.67 23267.3 19.00 19.78 0.00 0.00 0.00 0.00 3105.34 30353.0

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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:

Speed (Knots)

Rbare (KN)

2 x Rbow

thrusters (KN)

Rpod (KN)

RT (DAT) (KN)

PE (DAT) (KW)

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

10 12 14 16 18

5

15

20

25

10

(MW)(10^5N)RT

PE

RP

TE

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

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Table 4.2 Total resistance by Holltrop – Menon 1984 Method:

Speed (Knots)

Rbare (KN)

2 x Rbow thrusters (KN)

Rpod (KN)

RT (DAT) (KN)

PE (DAT) (KW)

10 747.49 11.20 11.70 770.39 3962.89 11 891.22 13.52 14.16 918.90 5199.50 12 1048.23 16.04 16.85 1081.12 6673.54 13 1221.18 18.76 19.77 1259.71 8423.93 14 1414.94 21.70 22.93 1459.57 10511.24 15 1637.15 24.86 26.33 1688.34 13027.23 16 1898.79 28.22 29.95 1956.96 16106.56 17 2214.4 31.80 33.82 2280.02 19938.32 18 2607.82 35.58 37.91 2681.31 24826.79

10 12 14 16 18

5

15

20

25

10 RTPE

(MW)(10^5N)RT

PE

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

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Table 4.3 Total resistance by BSRA Method:

Speed (Knots)

Rbare (KN)

2 x Rbow

thrusters (KN)

Rpod (KN)

RT (DAT) (KN)

PE (DAT) (KW)

10 653.7 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 18367.4018 2494.88 35.58 37.91 2568.37 23781.05

10 12 14 16 18

RP

5

15

20

25

10T

E

(MW)(10^5N)RT

PE

FIG 4.3 Graph from BSRA method of resistance calculation.

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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 (FSICR Research Report No 53)

= 0.261

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

= 0 .326 RT = 1688.34KN An allowance of 25% is provided to get service condition resistance. RT = 1688.34 *1.25 = 2110.5 KN

Thrust calculation

Required thrust = RT/(1-t) = 3131.3 KN

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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 Ukon et al. TU032 (VTT) Mewis

(AE/AO) 0.55 0.537 0.58 Diameter (mm) 200 200 215.15 Pitch Ratio 0.800 0.850 1.104 Boss Ratio 0.280 0.278 0.276 No. of Blades 4 4 4 Rotation direction Right Right 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.

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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

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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 KQ = 0.0398 J = 0.563 n = VA/J×D = 1.306 PD = 2π×ρ×n3×D5× KQ = 15698.62 KW η0 = T× VA /PD = 0.5686 = 56.86 %

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 0.0398 0.0400 0.0395 n 1.306 1.302 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

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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 η t = Efficiency of transformer [Ref30] = 0.97

η g = 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 = 19125 KW ηm = Efficiency of motor = 0.96 η t = Efficiency of transformer [Ref30] = 0.97

η g = Efficiency of generator

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

PD = 17096.8 KW

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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 = 17096.8 KW RPM = 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 = 13500 mm B = 7050 mm C = 6500 mm D = 7750 mm (Given propeller diameter) E = 1600 mm F = 3355 mm G = 4900 mm H = 550 mm J = 2500 mm K = 2600 mm L = 6445 mm Tilt angle = 0o to 6o, Selected = 3o

Fig 4.7 [Ref30]

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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 AE/Ao 0.4 0.55 0.70

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

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Minimum blade area ratio to avoid capitation

(AE/A

O)

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

atm + ρgh – P

V) D

2)]+ K [Auf’en Keller formula]

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

PV

= 1.704 kN/m2

h = 8.0 m D = 7.75 m K = 0.1 for double screw propellers

ρ = 1.008 t/m3

g = acceleration due to gravity (9.81 m/s2)

=0.47

0.4 .55 .7

P/D D

AE/A

KTJ*

N

T

1 Kt 1cm=0.001

2 1cm=0.001

3 P/D 1cm=0.001

4 Ae/Ao 1cm=0.001

5 j* 1cm=0.002

6 T 1cm=2KN

1500

1700

1900

T(KN)

0.6

0.7

0.8P/D

0.6

0.7

0.8

D(m) 0.5

0.6

0.7

no

0.4

0.5

0.6

Ae/Ao

0.1

0.2

0.3

kt

0.2

0.3

0.4

j*

:

:

:

FPP WAGENINGEN

4

7.26m

TYPE

NO. OF BLADE

D

PROPELLER PARTICULARS

:

:

:

Ni - Al Bronze

0.527

0.742

Ae/Ao

P/D

MATERIAL

B - SERIES

RIGHT HANDED SCREW

00

N0

Table 4.8 performance curves

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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 D2 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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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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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:

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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 0.50 0.60 0.70 0.80 0.90 1.00Dis from CL TO TE 0.599 0.684 0.766 0.837 0.901 0.958 0.992 0.965 0.413Dis from CL TO LE 0.963 1.080 1.156 1.182 1.151 1.055 0.855 0.520 * chord length 1.562 1.764 1.922 2.019 2.053 2.013 1.847 1.485 0.413tmax 0.267 0.236 0.206 0.175 0.144 0.114 0.083 0.052 0.045LE-Tmax 0.547 0.618 0.673 0.717 0.798 0.892 0.885 0.742 *

Tables 4.10

Ordinates for the back (As distance in meters) From maximum thickness to trailing edge

From maximum thickness to leading edge

r/R 100 80 60 40 20 20 40 60 80 90 95 1000.2 * 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 *

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Tables 4.11 Ordinates for the face (As distance in meters) From maximum thickness to trailing edge

From maximum thickness to leading edge

r/R 100 80 60 40 20 20 40 60 80 90 95 1000.2 0.08 0.05 0.03 0.01 0.00 0.00 0.01 0.02 0.04 0.05 0.07 0.110.3 0.06 0.03 0.01 0.00 0 0.00 0.00 0.01 0.03 0.04 0.05 0.090.4 0.04 0.01 0.00 0 0 0 0.00 0.01 0.02 0.03 0.04 0.070.5 0.02 0.00 0 0 0 0 0 0.00 0.01 0.01 0.02 0.050.6 0.01 0 0 0 0 0 0 0 0.00 0.01 0.01 0.040.7 0 0 0 0 0 0 0 0 0 0.00 0.00 0.020.8 0 0 0 0 0 0 0 0 0 0 0 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

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= 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 = (1-t)/(1-w)

= 0.912

PE = PT X ηH KW

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

= 16771.3 KW

VICE (maximum) = (PE/980.93)1/3 = 2.576 m/s

VICE (Maximum) = 5.008 Knots

ASTERN SPEED IN KNOTS

0.4 0.6 0.8 1.0 1.2 1.4 1.6

5.06.07.08.0

THICKNESS OF ICE IN m

4.0

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.