Hp air for aircraft services:

A number of aircraft accessories produce sufficient heat in normal use to require a cooling system to prevent overheating. A good example is the aircraft electrical generator, which produces considerable heat under normal operating conditions. Such accessories can be cooled by ram airflow when the aircraft is flying, but will require an alternative cooling airflow when the aircraft is on the ground. For ground running and taxiing, the generator for example, is cooled by an airflow that is taken from the engine compressor. This air is blown through nozzles to produce a venturi effect area of low pressure. The low pressure then induces a continuous cooling flow of atmospheric air through the normal ram air passages. This is adequate for cooling most accessories during ground running. Figure. illustrates a generator cooling system. These are sometimes referred to as ejectors or eductors