What drives the power turbine?

The power turbine in a turboprop engine operates by harnessing the energy from expanding gases. During the combustion process within the engine, fuel is mixed with air and ignited, which generates high-pressure, high-temperature gases. These gases then expand rapidly as they move through the turbine section, which is designed to convert this thermal energy into mechanical energy.

As the expanding gases pass through the turbine blades, they create a force that drives the turbine, making it rotate. This rotation is essential because it provides the necessary power to turn the propeller, thereby propelling the aircraft forward. The design and operation of the power turbine are fundamentally reliant on the principles of thermodynamics, where the conversion of energy forms takes place.

The other options involve forms of energy or drives that do not contribute directly to the operation of the power turbine in a turboprop engine context. Mechanical rotation, hydraulic pressure, and electrical energy are not the primary forces that drive the turbine's function, which distinctly relies on the energy derived from the high-speed flow of expanding gases.