The Turbine provides power which is necessary to drive the engine compressor and the accessory gearbox. The Turbine extracts energy from the hot gases which come from the combustion chamber. On gas turbine engines, there are two different types of turbines.
One is the radial flow turbine and the other one is the axial flow turbine.
The two types of turbine have the same main components.
The first main component of a turbine is always a set of stationary vanes. These vanes named the turbine nozzle guide vanes. The next component is moving rotor blades on the turbine disc. You can find turbines with one or more stages. Like the stages of a compressor, a turbine stage made up of a stator and of a rotor.
RADIAL FLOW TURBINE
Radial flow turbines are always single stage turbines. Such turbines used only on small gas turbine engines like APU. Their advantage is that they have a simple design and are easy to manufacture. Compared to axial flow turbines, radial flow turbine have many disadvantages.
They only allow small airflows and are also less efficient. This is because of high aerodynamic losses and because the airflow must pass through the turbine against the opposing centrifugal forces. The radial inflow turbine has a high single stage turbine efficiency but has poor multistage efficiency. It also has the disadvantage of low axial velocity discharge and short service life under high-temperature loads due primarily to high centrifugal loads on the disk.
AXIAL FLOW TURBINES
Modern gas turbine engines use axial flow turbines. They can be built up with any number of turbine stages as necessary to operate the engine compressor, the accessories and the large fan of these high by-pass turbofan engines.
Another advantage of an axial flow turbine is that they allow the very high airflow which is needed to create the high thrust of modern engines.
Observe that the N2 shaft bolted to the turbine disk at the aft end. The spline first into a coupling device which slips over turbine shaft splines. The N2 compressor also has a splined shaft which fits into the coupling at the front end. The long shaft mechanically couples the rear, low pressure (N 1) turbine to the front (N 1) compressor. The short shaft couples the front turbine to the rear (N2) compressor.