In a reaction turbine, which component supports the rotating passages?

• A. Shroud ring
• B. Casing
• C. Rotor
• D. Diaphragm

Answer: (C)

In a reaction turbine, the moving blades (the rotating passages) are mounted directly on the rotor discs. The rotor provides the mounting points at the blade roots and carries the blades around with the shaft, so it is the component that actually supports the rotating passages as the turbine spins. The shroud ring ties the blade tips together to help with stiffness and vibration control, but it does not bear the blade roots. Stationary blades are supported by diaphragms and the casing, not the rotor.