In hydraulic turbines classified as mixed-flow reaction turbines, the water path through the runner is a combination of two components. State whether the following is correct: “The flow is partly radial and partly axial.”

Introduction:
Turbines are categorized by the direction of flow through the runner: radial, axial, or mixed. Mixed-flow reaction turbines blend radial and axial components to balance head utilization and discharge capacity across a range of sites and heads.

Given Data / Assumptions:

• Reaction turbine with pressure change across the runner.
• Runner passages guide flow with both radial and axial velocity components.
• Operation near design point.

Concept / Approach:
In mixed-flow turbines (e.g., modern Francis types), water enters the runner radially inward (or outward in some historical designs) and exits with a significant axial component. This combination enables efficient energy conversion over medium heads by controlling whirl and flow angles to maintain favorable incidence and reaction.

Step-by-Step Solution:
1) Guide vanes impart whirl; runner blades turn the flow, extracting energy.2) Velocity triangles show both radial and axial components at inlet/outlet.3) Outlet arranged to reduce residual swirl and minimize draft losses.4) Hence, the qualitative statement “partly radial and partly axial” holds true for mixed-flow reaction turbines.

Verification / Alternative check:
Performance maps and runner geometry confirm non-zero radial and axial velocity components under design conditions.

Why Other Options Are Wrong:
Incorrect/part-load only: mixed nature persists across loads, though angles vary.

Pelton wheel: impulse, tangential flow; not mixed reaction.

Kaplan: primarily axial flow, not mixed.

Common Pitfalls:
Confusing Francis (mixed) with Kaplan (axial) or Pelton (tangential impulse).

Final Answer:
Correct