How does a turbine drive the compressor in a gas-turbine engine?

In a gas-turbine engine, the turbine drives the compressor by extracting energy from hot, expanding combustion gases and transferring that power through a shaft.12

Because the turbine and compressor are mechanically linked, the turbine provides the necessary rotational energy to compress incoming air. In many modern, high-performance engines, this is achieved through a "spooled" shaft arrangement. For example, in a multi-spool design, a high-pressure turbine stage is connected to a high-pressure compressor stage via an outer shaft, while a separate low-pressure turbine drives a low-pressure compressor through an inner, independent shaft. This configuration allows different sections of the compressor to rotate at optimal speeds.132

In applications where the engine must also drive an external load (such as a generator or propeller), the turbine may be split into two parts: a high-pressure turbine dedicated solely to driving the compressor, and a separate "free" turbine that extracts the remaining energy to power the external load.2