Engine air consumption
The engine consumes a certain amount of air during
the
combustion process. This requires the inlet duct to
have a certain internal cross-sectional area.
This area can be calculated using the formula:
A = 1.9 × engine power
A = Area in cm
2
Engine power in kW
The value applies to inlets, without obstacles, that are
up to 1 m (3.3 ft) with only one 90-degree bend. The
bend radius must be at least twice the duct diameter.
If longer ducts or more bends are used, the area must
be corrected by multiplying by the coefficient in the
Coefficient of bends table.
Coefficient of bends
Duct length, m (ft.)
Number
bends
1 (3.3) 2 (6.6) 3 (9.8) 4 (13.1) 5 (16.4)
1 1 1.04 1.09 1.13 1.20
2 1.39 1.41 1.43 1.45 1.49
3 – 1.70 1.72 1.74 1.78
Engine compartment ventilation
In addition to its air consumption, the engine radiates
heat. Heat radiation must be carried away from the
engine compartment in order to keep the temperature
down to permissible values.
The same dimensions must be chosen for the outlet
and
inlet channels in order to achieve low flow speeds
and low noise levels.
Ventilation inlet/outlet area is calculated according
to the following formula:
Area (cm
2
) = 1.65 × engine power (kW)
These values must be corrected in accordance with the
Coefficient of bends table in regard to bends and duct
length.
Outdoor temperature is assumed to be +30 °C (86 °F).
Correction factors according to the Correction factor
table must be used where applicable.
Correction factor
Outside temperature °C
(°F)
Correction factor
+20 (68) 0.7
+30 (86) 1.0
+40 (104) 1.4
Arrangement and Planning, Engine Room
24 47704162 10-2014 © AB VOLVO PENTA
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