At what stage does the turbine begin to extract energy from the combustion gases?

The correct answer indicates that the turbine begins extracting energy from the combustion gases after combustion has occurred. In a gas turbine engine, combustion takes place in the combustion chamber, where air and fuel mix and ignite, producing high-temperature, high-pressure gas.

Once the combustion process is complete, these gases expand and are directed into the turbine section of the engine. It is at this point that the turbine blades begin to extract energy from the high-energy gases, converting thermal energy into mechanical energy to drive the compressor and other connected components.

The understanding of turbine operation relies on recognizing that the energy extraction is fundamentally linked to the combustion process, and it is during or immediately after this combustion phase that the gases provide the necessary energy for the turbine to function efficiently.