MAN B&W S65ME-C8.2-GI-TII User Manual

MAN B&W
Page 7 of 7
MAN Diesel
7.0 9
MAN B&W ME-GI TII engines 198 86 39-0.2
Fig. 7.09.06: Gas condition during purging
The gas return system receives the remaining gas
in the pipes and accumulators on engine side
when fuel gas running is stopped and if the sys-
tem is ready to receive gas. Otherwise, the gas is
blown off to the atmosphere.
Calculating the venting gas flow
The gas flow can be calculated from the Bird,
Stewart and Lightfoot source-term model for
choked gas flows from a pressurized gas system:
[2/(k-1)] × (F
a
-1)
t = -------------------------------------------
C
D
× (A/V) × {k (P
0
/d
0
) × [2/(k+1)]
b
}
½
where
t = the time since the flow started (when valve
opens)
k = c
p
/c
v
of the gas (1.77 for methane at 300 bar,
45 °C)
F = the fraction of initial gas weight remaining in
the system at any time t
a = (1-k)/2
C
D
= coefficient of discharge, normally 0.72
A = cross sectional area of purge valve (805) in m
2
V = system volume (piping volume from vent si-
lencer to inert gas control valve (809) in m
3
P
0
= the initial gas pressure in the system, in Pa
(30 MPa)
d
0
= the initial gas density in the system (195 kg/m
3
for methane at 300 bar, 45 °C)
The pressure P at any fraction F : P = P
0
F
k
Example of pressure and mass flow at any given
time for 100 l system volume and DN 50 valve is
shown in Fig. 7.09.06.
P (bar)
m (kg)
mdot (kg/s)
0
0,0
0
50
100
150
200
250
300
350
10
20
30
40
50
60
70
80
0,5 1,0 1,5 2,0 2,5 3,0 3,5
Gas condition during purging
Time after opening of gas purge valve (805) (seconds)
Pressure (bar)
/CUUMI/CUUǤQYMIU
Gas return system
The optional gas return system, option: 4 37 611,
enables emission-free gas solution by saving the
fuel gas that is emitted to atmosphere during gas
pipe emptying procedures.
078 12 97-4.4.1b

MAN B&W S65ME-C8.2-GI-TII Specifications

General

Brand	MAN B&W
Model	S65ME-C8.2-GI-TII
Category	Engine
Language	English