Bergen B35:40, Руководство по проекту

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Gas Exhaust gas system
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2.03
0317 BC
E
XHAUST GAS SYSTEM
Introduction
it is important to design a system that will remove all
exhaust gas from the engine and give a total
ventilation out of engine room (to free air).
The engine must have good working condition with
access to free air.
Design of the system
The following must be taken into consideration:
•
Total pressure loss in the exhaust system must
not exceed 300 mm WG
• Radius on pipe bends to be 2xD
pipe
• recommended max. exhaust gas velocity is
45 m/s
• Thermal expansion of the exhaust piping
• Exhaust pipe fixation to prevent vibration
• Insulation with respect to max. allowed surface
temperature
• Required exhaust gas noise attenuation
• Drain pockets to avoid water coming into
the engine
• Exhaust from one engine should not be mixed
with the exhaust from other engines
• Exhaust gas must not enter the fresh air system
We supply compensator(s) for the engine exhaust
gas outlet. The compensator shall be mounted
directly onto the turbocharger. It is not permitted to
fix a diffuser or a pipe directly on the gas outlet.
After the compensator a diffuser must be made to
match the diameter of the exhaust gas pipe.
The diffuser’s taper angle is shown is normally 28°C
or 40°C depending on turbocharger type.
Exhaust from one engine should not be mixed with
the exhaust from other engines. When this is not
possible, silencers and sealed closing valves must be
mounted in front of the mixing point. This will
prevent oscillation between engines and feedback
with carbon build-up in engines not running.
Dimensioning of exhaust pipe and
exhaust gas silencer
The size of the exhaust pipe and silencer is
determined from the following calculation formula:
Exhaust volume flow can be found in technical data,
part 1.04. Flow area in table 2.
Velocity in the exhaust pipe shall not exceed 45 m/s
due to risk of resonance.
Backpressure exceeding 300 mm WG will have a
negative influence on the fuel consumption and the
thermal load of the engine.
Recommended maximum exhaust gas velocity is 45
m/s, and with this velocity the pressure loss through
our standard silencer is 120 mm WG.
Choose an exhaust pipe dimension that gives a
velocity close to the limit of 45 m/s.
The silencer is chosen based on inlet/outlet
information, attenuation and engine type. Note that
pipe dimension and inlet/outlet dimension for the
silencer may be different.
Total pressure drop in air inlet system outside engine
is max. 100 mm WG.
Fitting the exhaust pipes
The pipes should be fixed properly to prevent
vibration. A fixing point must be made on both sides
of the pipe at the support.
Exhaust gas flow m
2
s
  
Flow aera in pipe m
2
 
-----------------------------------------------------------------------
Exhaust gas velocity m s
  
=
DN (pipe diam. 400 450 500 (550)
Flow area (m
2
) 0.1257 0.1590 0.1963 0.2376
DN (pipe diam. 600 700 800
Flow area (m
2
) 0.2827 0.3849 0.5027
Table 2. Flow area in pipe
Pipe
diameter
Pressure loss in
mm WG per
meter pipe
Pressure loss for
a 90° bend
corresp. to
ND 300 - 400 approx. 4.0 approx. 4.5 m pipe
ND 450 - 500 approx. 3.3 approx. 6.0 m pipe
ND 600 - 700 approx. 2.5 approx. 10.0 m pipe
ND 800 approx. 2.0 approx. 12.0 m pipe
Table 3.
Pressure losses with exhaust gas velocity of 45 m/s