MAN B&W
2.02
Page 1 of 2
MAN Diesel
198 38 782.6
MAN B&W MC/MC-C, ME/ME-C/ME -B/GI engines
D = Optimum propeller diameters
P/D = Pitch/diameter ratio
Shaft power
kW
8.500
8.600
8.700
8.800
8.900
9.000
9.100
9.200
9.300
9.400
9.500
70
80
90
100
110
120
130
r/min
Propeller
speed
P/D
1.00
0.95
0.90
0.85
0.80
D
7.4m
0.75
7.2m
7.0m
6.8m
6.6m
0.70
0.65
0.60
0.55
D
P/D
0.50
Fig. 2.02.01: Influence of diameter and pitch on propeller design
Propeller diameter and pitch, influence on the optimum propeller speed
In general, the larger the propeller diameter D,
the lower is the optimum propeller speed and the
kW required for a certain design draught and ship
speed, see curve D in the figure below.
The maximum possible propeller diameter de-
pends on the given design draught of the ship,
and the clearance needed between the propeller
and the aft body hull and the keel.
The example shown in the figure is an 80,000 dwt
crude oil tanker with a design draught of 12.2 m
and a design speed of 14.5 knots.
When the optimum propeller diameter D is in-
creased from 6.6 m to 7.2. m, the power demand
is reduced from about 9,290 kW to 8,820 kW, and
the optimum propeller speed is reduced from 120
r/min to 100 r/min, corresponding to the constant
ship speed coefficient
∝
= 0.28 (see definition of
∝
in Section 2.02, page 2).
Once an optimum propeller diameter of maximum
7.2 m has been chosen, the corresponding op-
timum pitch in this point is given for the design
speed of 14.5 knots, i.e. P/D = 0.70.
However, if the optimum propeller speed of 100
r/min does not suit the preferred / selected main
engine speed, a change of pitch away from opti-
mum will only cause a relatively small extra power
demand, keeping the same maximum propeller
diameter:
•
going from 100 to 110 r/min (P/D = 0.62) requires
8,900 kW i.e. an extra power demand of 80 kW.
•
going from 100 to 91 r/min (P/D = 0.81) requires
8,900 kW i.e. an extra power demand of 80 kW.
In both cases the extra power demand is only
of 0.9%, and the corresponding ‘equal speed
curves’ are
∝
=+0.1 and
∝
=0.1, respectively, so
there is a certain interval of propeller speeds in
which the ‘power penalty’ is very limited.
178 47 032.0
Summary of Contents for B&W S50ME-B9.3-TII
Page 4: ......
Page 10: ......
Page 11: ...MAN B W MAN Diesel Engine Design 1 ...
Page 12: ......
Page 27: ...MAN B W MAN Diesel Engine Layout and Load Diagrams SFOC 2 ...
Page 28: ......
Page 53: ...MAN B W MAN Diesel Turbocharger Selection Exhaust Gas By pass 3 ...
Page 54: ......
Page 58: ......
Page 59: ...MAN B W MAN Diesel Electricity Production 4 ...
Page 60: ......
Page 92: ......
Page 93: ...MAN B W MAN Diesel Installation Aspects 5 ...
Page 94: ......
Page 124: ......
Page 133: ...MAN B W MAN Diesel List of Capacities Pumps Coolers Exhaust Gas 6 ...
Page 134: ......
Page 154: ......
Page 155: ...MAN B W MAN Diesel Fuel 7 ...
Page 156: ......
Page 170: ......
Page 171: ...MAN B W MAN Diesel Lubricating Oil 8 ...
Page 172: ......
Page 188: ......
Page 189: ...MAN B W MAN Diesel Cylinder Lubrication 9 ...
Page 190: ......
Page 199: ...MAN B W MAN Diesel Piston Rod Stuffing Box Drain Oil 10 ...
Page 200: ......
Page 202: ......
Page 203: ...MAN B W MAN Diesel Central Cooling Water System 11 ...
Page 204: ......
Page 209: ...MAN B W MAN Diesel Seawater Cooling System 12 ...
Page 210: ......
Page 220: ......
Page 221: ...MAN B W MAN Diesel Starting and Control Air 13 ...
Page 222: ......
Page 227: ...MAN B W MAN Diesel Scavenge Air 14 ...
Page 228: ......
Page 239: ...MAN B W MAN Diesel Exhaust Gas 15 ...
Page 240: ......
Page 254: ......
Page 255: ...MAN B W MAN Diesel Engine Control System 16 ...
Page 256: ......
Page 265: ...MAN B W MAN Diesel Vibration Aspects 17 ...
Page 266: ......
Page 280: ......
Page 281: ...MAN B W MAN Diesel Monitoring Systems and Instrumentation 18 ...
Page 282: ......
Page 302: ......
Page 306: ......
Page 307: ...MAN B W MAN Diesel Dispatch Pattern Testing Spares and Tools 19 ...
Page 308: ......
Page 322: ......
Page 323: ...MAN B W MAN Diesel Project Support and Documentation 20 ...
Page 324: ......
Page 332: ......
Page 333: ...MAN B W MAN Diesel Appendix A ...
Page 334: ......