Classify a Kaplan turbine with respect to flow direction through the runner. State whether the assertion “A Kaplan turbine is an axial flow reaction turbine” is correct.

Introduction:
Kaplan turbines are widely used for low-head, high-discharge hydro sites. Their hallmark is adjustable runner blades combined with wicket gates to maintain high efficiency across varying loads, and an essentially axial flow path through the runner.

Given Data / Assumptions:

• Kaplan runner with variable-pitch blades.
• Reaction turbine with pressure drop through the runner.
• Draft tube present for pressure recovery.

Concept / Approach:
In axial flow turbines, the bulk direction of water relative to the runner shaft is largely parallel to the axis at inlet and outlet. Kaplan geometry guides flow so that tangential components are minimized at exit, limiting swirl and improving draft tube recovery. The machine operates with significant static pressure change (reaction), distinguishing it from impulse wheels.

Step-by-Step Solution:
1) Wicket gates regulate swirl and discharge.2) Runner blades adjust pitch to keep incidence optimal as load changes.3) Flow remains predominantly axial through the runner passages.4) Draft tube converts kinetic energy to pressure for head recovery.

Verification / Alternative check:
Velocity triangles at best efficiency show small whirl at outlet and axial dominance, confirming classification.

Why Other Options Are Wrong:
Incorrect/part-load/fixed-blade-only: Kaplan retains axial classification across loads and with variable pitch.

Impulse operation: Kaplan is a reaction turbine; pressure drop occurs within the runner.

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

Final Answer:
Correct