Which of the following components is NOT part of the high-pressure turbine?

The correct choice is the exhaust hood, as it is not considered a component of the high-pressure turbine itself. The exhaust hood is primarily part of the turbine's exhaust system, designed to guide the exhaust gases away from the turbine and into the environment or further downstream components, like the heat recovery system.

In contrast, blades, shrouds, and diffusers are essential components of the high-pressure turbine. The blades are critical for extracting energy from the high-temperature, high-pressure gas produced by the combustion process, ultimately converting thermal energy into mechanical energy. Shrouds help enhance the performance and efficiency of the blades by reducing tip leakage and improving the aerodynamic flow. Diffusers, on the other hand, help convert the high-velocity gas from the turbine into a lower velocity, higher pressure flow, aiding in the efficient operation of the entire gas turbine system. Understanding the roles of these components highlights their importance in the turbine's design and function, distinguishing them from auxiliary components such as the exhaust hood.