WÄRTSILÄ WARTSILA32, Product Manual, Page: 154 / 254

a flap for controlling the direction and amount of air. Also other combustion air consumers,
for example other engines, gas turbines and boilers shall be served by dedicated combustion
air ducts.
If necessary, the combustion air duct can be connected directly to the turbocharger with a
flexible connection piece. With this arrangement an external filter must be installed in the duct
to protect the turbocharger and prevent fouling of the charge air cooler. The permissible total
pressure drop in the duct is max. 1 kPa for engines with 500 kW/cylinder or 2 kPa for engines
with 580 kW/cylinder. The duct should be provided with a step-less change-over flap to take
the air from the engine room or from outside depending on engine load and air temperature.
For very cold conditions heating of the supply air must be arranged. The combustion air fan
is stopped during start of the engine and the necessary combustion air is drawn from the
engine room. After start either the ventilation air supply, or the combustion air supply, or both
in combination must be able to maintain the minimum required combustion air temperature.
The air supply from the combustion air fan is to be directed away from the engine, when the
intake air is cold, so that the air is allowed to heat up in the engine room.
10.2.1 Charge air shut-off valve, "rigsaver" (optional)
In installations where it is possible that the combustion air includes combustible gas or vapour
the engines can be equipped with charge air shut-off valve. This is regulated mandatory where
ingestion of flammable gas or fume is possible.
10.2.2 Condensation in charge air coolers
Air humidity may condense in the charge air cooler, especially in tropical conditions. The
engine equipped with a small drain pipe from the charge air cooler for condensed water.
The amount of condensed water can be estimated with the diagram below.
Fig 10-3 Condensation in charge air
coolers
Example, according to the diagram:
At an ambient air temperature of 35°C and a relative humidity of
80%, the content of water in the air is 0.029 kg water/ kg dry air.
If the air manifold pressure (receiver pressure) under these condi-
tions is 2.5 bar (= 3.5 bar absolute), the dew point will be 55°C.
If the air temperature in the air manifold is only 45°C, the air can
only contain 0.018 kg/kg. The difference, 0.011 kg/kg (0.029 -
0.018) will appear as condensed water.
10.2.3 Combustion air system design in arctic conditions
At high engine loads, the cold air has a higher density and the compressor is working more
efficiently thus increasing the flow of combustion air. The cylinder peak firing pressure increases
10-4 Wärtsilä 32 Product Guide - a21 - 7 September 2016
Wärtsilä 32 Product Guide 10. Combustion Air System