Turbine cooling Airflow:
Figure illustrates the turbine cooling airflow of a typical gas turbine engine. The outward flow of cooling air is controlled by air seals of multi-groove construction and the arrangement is such that the turbine discs obtain the maximum possible cooling from the airflow. Interstage seals are incorporated and they are made in such a way that the front sections provide less restriction to the passage of air than the rear sections do. The result is that the rate at which the cooling air flows across the seals is sufficient to prevent any inward flow of hot gases. The front face of each disc receives a greater airflow than the rear.
High pressure cooling air is also directed to the engine's nozzle guide vanes and turbine blades. These components, which are externally heated by the high temperature gas stream, are cooled by ducting air through air passages formed inside the items themselves. After completing its task, the air is exhausted into the engine exhaust gas flow and thence to atmosphere.