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2.7 Exhaust Outlet
Outlet location. Engine performance and efficiency
depend on the location of the exhaust outlet. Direct the
exhaust outlet away from the air inlet to prevent exhaust
gases from entering the air inlet and clogging the
dry-type air filter elements. Hot exhaust drawn through
the radiator adversely affects engine cooling. Locate
the exhaust outlet to prevent exhaust fumes from
entering a building or enclosure. See Figure 2-4 for
exhaust temperatures.
Noise reduction.
The exhaust outlet configuration
affects the apparent noise level for people or animals in
the vicinity. An upward-directed outlet seems quieter
than
one
directed
Additionally, a 30- to 45-degree angled cut at the end of
a horizontal exhaust outlet pipe reduces turbulence at
the outlet, thereby reducing the noise level.
Rain cap. To prevent precipitation from entering the
exhaust pipe, install a rain cap on vertical outlets. See
Figure 2-3. In a climate where freezing is common, do
not use a rain cap. Instead, extend the exhaust piping at
least 610 mm (24 in.) beyond the roof line and create a
gradual U bend at the end to direct the exhaust outlet
downward. Keep the pipe outlet at least 457 mm (18 in.)
from the roof to prevent hot exhaust from igniting the
roof material.
Note: Avoid using a rain cap in areas subject to freezing
temperatures.
Exhaust Temperatures, _C (_F)
50 Hz
Model, kW
10
490
15
570 (1058)
20
550 (1022)
Figure 2-4 Exhaust Temperatures
TP-6609 6/08
downward
or
horizontally.
60 Hz
(914)
550 (1022)
570 (1058)
560 (1040)
2.8 Exhaust System Back
Pressure
Exhaust back pressure limits engine power and
excessive back pressure causes serious engine
damage. Excessive back pressure usually results from
one or more of the following reasons:
D
The exhaust pipe diameter is too small.
D
The exhaust pipe is too long.
D
The exhaust system has too many sharp bends.
D
The exhaust silencer is too small.
D
The exhaust silencer is not the correct design for the
application.
The engine's maximum exhaust back pressure limit is
shown in Figure 2-5. Use the procedure in Appendix B
to verify that the planned exhaust system does not
exceed the maximum exhaust back pressure limit.
Maximum Exhaust Back Pressure
Model, kW
10
15
20
Figure 2-5 Silencer and Engine Exhaust Pipe Back
Pressures
kPa (in. water)
12.75
(51.3)
7.85
(31.6)
9.81
(39.4)
Section 2 Exhaust Systems
19
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