Bearing chamber cooling, Development of high pressure turbine blade cooling,High pressure nozzle guide vane construction and cooling ,Accessory cooling

Fig. 9-3 Development of high pressure turbine blade cooling.

Bearing chamber cooling


9. Air cooling of the engine bearing chambers is not normally necessary since the lubrication system
(Part 8) is adequate for cooling purposes.
Additionally, bearing chambers are located, where
possible, in the cooler regions of the engine. In instances where additional cooling is required, it is
good practice to have a double skinned bearing housing with cooling air fed into the intermediate space.

Fig. 9-4 High pressure nozzle guide vane construction and cooling

Accessory cooling

10. 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 louvres in the

engine cowlings.

11. When an accessory unit is cooled during flight by atmospheric 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 create a low pressure area which forms an

ejector, so inducing a flow of atmospheric air through the intake louvres. 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 in fig. 9-6.