Turbine engine arrangement

Abstract

A turbine engine arrangement incorporates an electrical machine combination which can act as a generator or motor. Thus, the combination during initial turbine engine arrangement start-up acts through this motor to drive shaft rotation. This shaft rotation creates core compressed air which is bled through a valve to an air turbine such that the electrical machine when acting as a motor or generator at low engine loads is appropriately cooled. The arrangement also includes a compressor fan which generates an airflow utilised by the air turbine in order to drive the electrical machine as a generator of electrical power when engine conditions dictate. A duct is provided to direct airflow exhausted from the air turbine to a heat exchanger arranged to exchange heat with a bypass flow from the compressor fan. In such circumstances, the generators can operate substantially independently of rotational speed of the engine shafts within the core whilst bled air through the valve acts to cool the electric machine during initial start-up. Generally, a gearbox is provided whereby matching of air turbine rotation with generator requirements is achieved whilst also through a coupling allowing connection to the primary drive shaft of the core to either allow engine start-up or driving of the generators when engine speed is appropriate.