S80ME-C 198 45 56-4.1
MAN B&W Diesel A/S 6.04
Page 11 of 12
Calculation of Exhaust Data for Derated Engine
Example 3:
Expected exhaust data for a derated 6S80ME-C with high efficiency turbocharger and with fixed pitch
propeller.
Based on the engine ratings below, and by means of an example, this chapter will show how to calculate the
expected exhaust gas amount and temperature at service rating, and for a given ambient reference condition
different from ISO.
The calculation is made for the service rating (S) being 80%of the specified MCR power of the diesel engine.
Nominal MCR, (L
1
)P
L
1
: 23,280 kW (100.0%) and 76.0 r/min (100.0%)
Specified MCR, (M) P
M
: 18,624 kW (80.0%) and 68.4 r/min (90.0%)
Matching point, (O) P
O
: 16,762 kW (72.0%) and 66.0 r/min (86.9%) P
O
= 90.0% of P
M
Service rating, (S) P
S
: 14,899 kW and 63.5 r/min P
S
= 80.0% of P
M
Reference conditions
Air temperature T
air
........................................ 20° C
Scavenge air coolant temperature T
CW
......... 18° C
Barometric pressure p
bar
..................... 1,013 mbar
Exhaust gas back-pressure
at specified MCR ∆p
M
....................... 300 mm WC
a) Correction for choice of specified MCR point M
and matching point O:
P
M%
= x 100 = 80.0%
n
M%
= x 100 = 90.0%
By means of Figs. 6.05.07 and 6.05.08:
∆m
M%
= -0.6 %
∆T
M
= -8.1° C
As the engine is matched in O lower than 100% M,
and P
O%
= 90.0% of P
M
we get by means of equation [6]
∆T
O
= - 0.3 x (100 - 90.0) = - 3.0° C
b) Correction for ambient conditions and back-
pressure:
By means of equations [7] and [8]:
∆M
amb%
= - 0.41 x (20 - 25) + 0.03 x (1,013 - 1,000)
+ 0.19 x (18 - 25) - 0.011 x (300 - 300) %
∆M
amb%
= + 1.11%
∆T
amb
= 1.6 x (20 - 25) - 0.01 x (1,013 - 1,000)
+ 0.1 x (18 - 25) + 0.05 x (300 - 300) °C
∆T
amb
= - 8.8° C
c) Correction for the engine load:
Service rating = 80% of specified MCR power
By means of Figs. 6.04.11 and 6.04.12:
∆m
S%
= + 5.6%
∆T
S
= - 11.7 °C
18,624
23,280
68.4
76.0
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