Gas turbine engine

A gas turbine engine for an aircraft, the gas turbine engine comprising:

• a compressor stage;
• a bleed air line diverted from the compressor stage;
• and
• a thermoelectric generator system comprising:
• a thermoelectric generator;
• a vortex tube comprising a flow input fluidically connected to the bleed air line to receive an input of compressed gas from the bleed air line, wherein the vortex tube is configured to separate the compressed gas into a hot flow discharged from a first output of the vortex tube, and a cold flow discharged from a second output of the vortex tube;
• a radiator system comprising a first heat exchanger and a second heat exchanger disposed on opposing sides of the thermoelectric generator;
• wherein at least one of:
• the hot flow is directed to the first heat exchanger;
• and
• the cold flow is directed to the second heat exchanger,
• wherein the hot flow and/or the cold flow are directed back to join the bleed air from the bleed air line after passing through the radiator system.