Textos de Apoio (pdf)

Case 2: Panamax container ship
In this case, a typical Panamax container ship with
a container capacity of up to 5000 TEU might be
specified with an eight-cylinder Wärtsilä RT-flex82C
main engine. However, if a nine-cylinder engine is
employed instead, the daily fuel consumption can be
reduced by some two per cent.
In the engine/propeller layout for this ship as
shown in figure 8, the CMCR points for the two
alternative engines are on the same rating line
(α = 0.2) through a common design point for the
same ship service speed (knots).
The calculation of annual fuel costs given in table
4 is based on 6000 hours running with heavy fuel oil
costing US$ 500 per tonne.
The resulting payback time for the extra cost
associated with the additional engine cylinder
is estimated to be between four and seven years
depending on the bunker price of US$ 600–400 per
tonne respectively (Fig. 9). The calculations of the
payback are based on an interest rate of eight per
cent.
Table 3: Typical ship parameters for a Panamax
container ship
Length overall: about 295 m
Beam: 32.2 m
Design draught: 12 m
Scantling draught: 13.5 m
Sea margin: 15 %
Engine service load: 90 %
Table 4: Main engine options
Alternative engines: 8RT-flex82C 9RT-flex82C
Cylinder bore, mm: 820 820
Piston stroke, mm: 2646 2646
Stroke/bore ratio: 3.2:1 3.2:1
MCR, kW / rpm: 36,160/102 40,680/102
CMCR, kW / rpm: 36,160/102 35,480/97.5
BMEP at CMCR, bar: 19.0 17.5
CSR at 90% CMCR, kW / rpm: 32,544/98.5 32,250/94.3
BSFC at CMCR, g/kWh:
– 100% load: 169.0 166.6
– 90% load: 166.5 164.6
Daily fuel consumption, tonnes/day:
– ISO fuel, LCV 42.7 MJ/kg: 130.0 127.4
– LCV 40.5 MJ/kg: 137.1 134.3
– As percentage, %: 100 98 – 2.0%
Annual fuel costs, US$: 17,138,000 16,790,000
Fuel saving, US$: 0 – 348,000
Engine length, mm: 14,055 16,500
Engine mass, tonnes: 1020 1140
— 6 — © Wärtsilä Corporation, June 2008