Reaction turbine behavior In a reaction steam turbine, does the steam velocity increase in both the fixed (stator) blades and the moving (rotor) blades due to pressure drop occurring across each?

Introduction / Context:
Reaction turbines differ from pure impulse turbines in that pressure decreases across both stator and rotor passages. This design influences how absolute and relative velocities evolve through the stage and affects the distribution of work between fixed and moving rows.

Given Data / Assumptions:

• Reaction turbine stage with finite degree of reaction (R between 0 and 1).
• Stator and rotor passages shaped as nozzles or diffusers to create pressure and velocity changes.
• Steady, quasi-one-dimensional flow assumptions for velocity-triangle analysis.

Concept / Approach:

In a reaction stage, a portion of the total enthalpy (pressure) drop occurs in the moving blades. The stator accelerates the steam (pressure drop → velocity rise), and the rotor also experiences a pressure drop causing an increase in relative velocity through the rotor passages, even though the absolute exit velocity may be moderated by blade speed and turning. Thus, considering the proper frame, steam is accelerated in both blade rows.

Step-by-Step Solution:

Verification / Alternative check:

Velocity triangles for Parsons-type (R ≈ 0.5) show acceleration in stator and rotor passages, consistent with positive reaction staging.

Why Other Options Are Wrong:

Statements restricting the effect to compounded or Curtis stages confuse impulse compounding with reaction behavior.Zero-degree nozzle angle is not a condition for reaction; geometry sets reaction via blade shapes and pressure distribution.

Common Pitfalls:

Equating “velocity increase” only with absolute velocity; in the rotor, it is the relative velocity that is key when a pressure drop occurs in moving passages.

Final Answer:

True