Rotary assembly

A rotary assembly for driving spool rotation, comprising:

• a rotor configured to be mechanically coupled to a spool of a gas turbine engine;
• and
• a flow modifier configured to receive flow from and/or direct flow to the rotor, wherein
• the rotary assembly is configured to permit relative movement along an axial direction of the rotor between the rotor and the flow modifier to move between:
• a turbine configuration in which the rotor is configured to receive air from an external air source to drive the spool to rotate;
• and
• a compressor configuration in which the rotor is configured to be driven to rotate by the spool and to receive and compress air from the gas turbine engine, and discharge the compressed air for supply to an airframe system,
• the rotary assembly further comprises a controller configured to control relative movement along the axial direction of the rotor between the rotor and the flow modifier through a range of turbine positions of the turbine configuration to vary a torque applied to the rotor for driving the spool,
• the flow modifier comprises:
• a diffuser vane array comprising a plurality of diffuser vanes and configured to act together with the rotor to compress air received at the rotor in the compressor configuration;
• and
• a nozzle guide vane array comprising a plurality of nozzle guide vanes and configured to act together with the rotor to expand air received at the nozzle guide vane array from a flow director in the turbine configuration,
• the controller is configured to:
• cause relative movement between the rotor and the diffuser vane array so that the diffuser vane array is disposed around the rotor for operation in the compressor configuration;
• and
• cause relative movement between the rotor and the nozzle guide vane array so that the nozzle guide vane array is disposed around the rotor for operation in the turbine configuration, and
• the nozzle guide vane array is not disposed around the rotor in the compressor configuration, and the diffuser vane array is not disposed around the rotor in the turbine configuration.