Which statement about turbine power output is most accurate?

• A. It is solely determined by the exhaust nozzle
• B. It is independent of engine speed
• C. It is influenced by temperature, pressure, and bleed air
• D. It is directly related to humidity

Answer: (C)

Turbine power output is driven by the energy carried by the hot gases entering the turbine. The amount of work the turbine can extract depends on how much energy those gases have, which is set mainly by their temperature and pressure as they leave the combustor. A higher turbine inlet temperature means more enthalpy per unit mass, so more energy is available to do work (within material limits). Similarly, higher inlet pressure increases the energy content and the driving force for expansion, boosting the turbine’s ability to produce shaft power.

Bleed air changes things by removing some of the core air for other systems. That reduces the mass flow through the turbine and diverts energy away from being expanded in the turbine, lowering the power that can be produced.

Humidity can slightly affect air density and mass flow, but its direct impact on turbine power is much smaller than temperature, pressure, or bleed air. The nozzle mainly affects exhaust conditions and thrust, not the fundamental energy available to the turbine, and engine speed also influences mass flow and energy but isn’t the primary controlling factor described here.

So the statement that turbine power output is influenced by temperature, pressure, and bleed air best captures the main drivers of the turbine’s power.