Aerospace Principle Animation:Turbofan Engine Lab

Behind the fan the flow splits: the outer stream is gently accelerated and blown out, the inner stream enters the core to burn fuel. The same core with a bigger fan pushes more air more slowly, so fuel burn drops—why airliner engines keep getting fatter.

A single stage raises pressure by only about a third, so a dozen-plus stages of rotors and stators alternate. Pressure climbs toward the back while the passage narrows, and compression heats the air to nearly 900 K at the exit.

Just 20–30 g of fuel per kilogram of air heats the gas to 1800 K—hundreds of degrees beyond what turbine alloys tolerate. Air bled from the compressor flows inside the blades and seeps out of tiny holes to form a protective film over the surface.

Two concentric shafts work separately: the HP turbine drives the HP compressor on a short shaft, the LP turbine drives the fan and booster on a long shaft through the centre. The gas cools and expands through the turbines, and the remaining pressure becomes speed in the nozzle. The area enclosed on the T–s diagram is the net work per kilogram of air.

The bypass stream moves ten times the core’s air each second; it is slower, yet it supplies most of the thrust. Once the aircraft is moving, incoming air already has speed, the speed gain shrinks and thrust drops at the same throttle—drag the flight speed to see.