Accessory Cooling
A considerable amount of heat is produced by some of the
engine accessories, of which the electrical generator is an
example, and these may often require their own cooling
circuit. When air is used for cooling, the source may be the
compressor or atmospheric air ducted from intake louvers
in the engine cowlings.
When an accessory unit is cooled during flight by at-
mospheric air, it is usually necessary to provide an induced
circuit for use during static ground running when there
would be no external airflow. This is achieved by allowing
compressor delivery air to pass through nozzles situated in
the cooling air outlet duct of the accessory. The air velocity
through the nozzles creates a low-pressure area that forms
an ejector, so inducing a flow of atmospheric air through the
intake louvers. To ensure that the ejector system only
operates during ground running, the flow of air from the
compressor is controlled by a valve. A generator cooling
system with an ejector is shown