Gas turgine engine with transmission

Abstract

A multi spool gas turbine engine with a differential having a selectively rotatable member which rotational speed determines a variable ratio between rotational speeds of driven and driving members of the differential. The driven member is engaged to the first spool and a rotatable shaft independent of the other spools (e.g. connected to a compressor rotor) is engaged to the driving member. First and second power transfer devices are engaged to the first spool and the selectively rotatable member, respectively. A circuit interconnects the power transfer devices and allows a power transfer therebetween, and a control unit controls the power being transferred between the power transfer devices. Power can thus be transferred between the first spool and the selectively rotatable member to change the speed ratio between the first spool and the rotatable shaft.

1 . A method of adjusting a speed of a rotatable shaft of a gas turbine engine having a high pressure section including interconnected compressor and turbine rotors, the method comprising:
 rotating at least one rotor of a low pressure turbine with a flow of exhaust gases from the high pressure section;   driving a rotation of the rotatable shaft with a power shaft through a variable transmission, the power shaft being driven by the at least one rotor of the low pressure turbine; and   transferring power between the power shaft and a rotational member of the transmission to change a ratio of rotational speeds between the rotatable shaft and the power shaft.   
     
     
         2 . The method as defined in  claim 1 , wherein transferring power includes transferring power from the power shaft to the transmission to increase the rotational speed of the rotatable shaft and transferring power from the transmission to the power shaft to decrease the rotational speed of the rotatable shaft. 
     
     
         3 . The method as defined in  claim 1 , wherein driving a rotation of the rotatable shaft includes driving a rotation of at least one rotor of a low pressure compressor located upstream of the high pressure section and coupled to the rotatable shaft.