Which method is used to cool the turbine disc?

The use of high-pressure (HP) compressor bleed air is a well-established method for cooling turbine discs in gas turbine engines. This method makes efficient use of compressed air that is already being produced as part of the engine's operation.

When the engine operates, the HP compressor compresses the incoming air, increasing its pressure and temperature. A portion of this high-pressure air can be diverted and routed to provide cooling to the turbine discs. The use of bleed air helps maintain the temperature of the discs below critical levels, allowing them to function effectively and preventing overheating, which could lead to material failure. This process aids in maintaining the integrity and reliability of the turbine, which operates under extreme conditions.

The other options have limitations in their application. Oil jets can be used for lubrication and cooling in various components but are not typically the primary method for turbine disc cooling. Cooling fluids might refer to various types of coolants, but they are not standard for turbine disc cooling in practice. Ambient air may be too cool and potentially insufficient for the high thermal demands of turbine operation, as it would not adequately manage the heat produced during combustion and the subsequent energy conversion processes.