Calculation Of Exhaust Data For Derated Engine; Reference Conditions - Man B&W S50MC-C8-TII Project Manual

MAN B&W

Calculation of Exhaust Data for Derated Engine

Example 3:
Expected exhaust gas data for a derated 6S50MC-C8-TII with high efficiency MAN Diesel turbocharger
type TCA and 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
Specified MCR, (M)
Optmising point, (O)
Service rating, (S)

Reference conditions

Air temperature T ........................................ 20 °C
air
Scavenge air coolant temperature T
Barometric pressure p
Exhaust gas backpressure
at specified MCR ∆p
M
a) Correction for choice of specified MCR point M
and optmising point O:
8,466
____
P = x 100 = 85.0%
9,960
M%
____
114.3
n = x 100 = 90.0%
127.0
M%
By means of Figs. 6.04.07 and 6.04.08:
= + 0.25%
∆m
M%
=  7.2 °C
∆T
M
As the engine is optmised in O lower than 100% M,
and P = 100.0% of P
O%
we get by means of equation [6]
=  0.3 x (100  100.0) =  0.0 °C
∆T
O
MAN B&W S50MC-C8-TII
P : 9,960 kW (100.0%) and 127.0 r/min (100.0%)
L1
P : 8,466 kW (85.0%) and 114.3 r/min (90.0%)
M
P : 8,466 kW (85.0%) and 114.3 r/min (90.0%), P
O
P : 6,773 kW and 106.1 r/min, P
S
......... 18 °C
CW
....................... 1,013 mbar
bar
......................... 300 mm WC
M
= 80.0% of P
S
b) Correction for ambient conditions and
backpressure:
By means of equations [7] and [8]:
=  0.41 x (20  25) + 0.03 x (1,013  1,000)
∆M
amb%
+ 0.19 x (18  25)  0.011 x (300  300)%
= + 1.11%
∆M
amb%
= 1.6 x (20  25)  0.01 x (1,013  1,000)
∆T
amb
+ 0.1 x (18  25) + 0.05 x (300  300) °C
=  8.8 °C
∆T
amb
c) Correction for the engine load:
Service rating = 80% of specified MCR power
By means of Figs. 6.04.11 and 6.04.12:
= + 7.1%
∆m
S%
=  18.8 °C
∆T
S
MAN Diesel
= 100.0% of P
O M
M
6.04
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