The rotating section consists of a solid shaft, driven by a shaft mounted air impulse turbine.
The water-valve directs airflow to an impulse turbine with tandem rotors.
British Dictionary definitions for impulse turbine
impulse turbine
noun
1.
a turbine in which the expansion of the fluid, often steam, is completed in a static nozzle, the torque being produced by the change in momentum of the fluid impinging on curved rotor blades Compare reaction turbine