Man B&W L35MC6-TII, Project Manual

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MAN B&W 6.04
Page 11 of 12
MAN Diesel
MAN B&W L35MC6-TII 198 72 49-0.0
Calculation of Exhaust Data for Derated Engine
Example 3:
Expected exhaust gas data for a derated 6L35MC6-TII with conventionel MAN Diesel turbocharger type
TCR 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
) P
L1
: 3,900 kW (100.0%) and 210.0 r/min (100.0%)
Specified MCR, (M) P
M
: 3,315 kW (85.0%) and 189.0 r/min (90.0%)
Optmising point, (O) P
O
: 3,315 kW (85.0%) and 189.0 r/min (90.0%), P
O
= 100.0% of P
M
Service rating, (S) P
S
: 2,652 kW and 175.5 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 optmising point O:
P
M%
=
3,315 ____
3,900
x 100 = 85.0%
n
M%
=
189.0
____
210.0
x 100 = 90.0%
By means of Figs. 6.04.07 and 6.04.08:
∆
m
M%
= + 0.25%
∆
T
M
=  7.2 °C
As the engine is optmised in O lower than 100% M,
and P
O%
= 100.0% of P
M
we get by means of equation [6]
∆
T
O
=  0.3 x (100  100.0) =  0.0 °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%
= + 7.1%
∆
T
S
=  18.8 °C